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CHAPTER 14

The Adult SpineSERGIO MENDOZA-LATTES/ANDRÉ P. BOEZAART

� THE CERVICAL SPINE

Special Anatomic Considerations

The surgical anatomy of the cervical spine is divided intothat of the craniocervical junction and the subaxial cervi-cal spine (Fig. 14-1). The first includes the occiput (C0),atlas (C1) and axis (C2) vertebrae. The atlas vertebra hasthe form of a ring, with two lateral articular masses thatarticulate with the occipital condyles cephalad and withthe superior facets of the axis caudad. The atlas and axisprovide 40 percent of the total rotation of the cervicalspine. This occurs around the odontoid process (dens).The stability between C1 and C2 depends on the lateral-mass facet-joint capsules and on the transverse ligamentof the atlas, which prevents anteroposterior (AP) transla-tion of the dens. Pathology that can potentially damagethis ligament includes trauma and inflammatory pannus,as that from rheumatoid arthritis (Fig. 14-2). Instability ofC1–C2 may be repaired by a C1–C2 fusion. Advancedarthritis may also erode the articular surfaces of C0–C1and C1–C2. As a consequence, the axis migrates closer tothe foramen magnum and the dens may intrude into thecranium. If this basilar invagination is reducible withtraction, the patient is operated under skeletal tractionand the occiput is fixed or fused in the reduced positionto the cervical spine (craniocervical fusion). Nevertheless,if the dens cannot be reduced or there are other condi-tions that occupy the anterior spinal canal and displacethe brainstem, this may be decompressed anteriorly viatransoral exposure.

The subaxial cervical spine consists of five vertebraelinked by five joints at each level: the intervertebral disk(a symphysis), two facet joints, and two uncinate processes.These joints provide significant range of motion and also

protect the neural elements. This area may be approachedfor fusion and/or decompression from both the anteriorand posterior aspects of the neck.

Anterior decompression includes anterior diskec-tomy or corpectomy and fusion. Posterior decompres-sion may be by laminectomy or laminoplasty. In general,posterior decompression is preferred for multilevel dis-ease with a lordotic cervical spine. The anterior approachto the subaxial cervical spine is a standard, widely usedprocedure. The approach takes advantage of the anatomicplanes of the neck and requires only minimal soft tissuedisruption.

Patient Profile

A wide array of patients may present, including youngand healthy patients who have suffered an injury as wellas elderly patients with long-standing spinal cord dys-function secondary to myelopathy. A spine affected byrheumatoid arthritis requires special attention and is dis-cussed later (see also Chap. 8). Multiple other comorbidi-ties may be present in the elderly group. Finally, there arealso those who have suffered spinal cord injury, whosemanagement deserves special consideration.

Common Comorbidities

Comorbidities and, therefore, the indications for the proce-dure may vary significantly. Most frequently, patients whorequire fusion for injuries or for cervical disk disease areyoung and present without comorbidities. Patients withcervical spondylotic myelopathy, on the other hand, arefrequently in their sixth or seventh decade of life and pres-ent with one or more comorbidities as well as long-termspinal cord dysfunction. Patients suffering from rheumatoidarthritis and subsequent atlantoaxial instability frequently

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present with multiple medical problems, including thoseassociated with chronic steroid therapy.

Spinal Cord Injury

The loss of sympathetic tone produces generalizedvasodilatation below the level of the injury. The intravas-cular volume is expanded, which leads to hypotension.Additionally, there is an increase in vagal tone due to sym-patholysis, resulting in bradycardia, which reduces cardiacoutput and further adds to the reduction of systemic bloodpressure. Fluid management is therefore crucial. Tooaggressive attempts to treat neurogenic shock solely by theadministration of fluids may cause fluid overload and pul-monary edema. Furthermore, some patients may have con-comitantly suffered pulmonary contusion. The resultanthypoxia not only worsens the effects of oligemia but mayalso contribute to the progression of secondary injury of thespinal cord. Optimal oxygenation is mandatory, and anti-cholinergic drugs such as atropine may be used to counter-act bradycardia. Careful administration of vasopressors isindicated to control vasomotor disturbances, and great caremust be taken to identify and treat other associated injuries,such as liver and spleen lacerations, which may be maskedby the spinal cord injury. If the injury is above the level ofC4, respiratory function may be compromised owing toinvolvement of the phrenic nerve, and assisted ventilationmay be required after surgery. Additionally, gastroparesisand immobility increase the risk of aspiration pneumonia.Nasogastric tubes are therefore essential.

Positioning on the Operating Table

Positioning may directly influence surgical exposure andfusion alignment. Correct positioning is also necessitatedto preserve neurologic function. Once the patient isanesthetized, there are no warning signs of maneuversthat might be damaging to the cervical spinal cord. Thisis especially important in cases of instability and cervicalcanal stenosis. General precautions include moving thepatient in a rigid cervical orthosis at all times and head-to-trunk immobilization during transfers.

Positioning for Anterior Surgical ExposureFor anterior cervical exposure, the neck should lie in aneutral or slightly extended position. This is achieved byplacing a roll under the scapulae. Care must be taken inpositioning an elderly patient with a stenotic spinalcanal. Gardner-Wells tongs may be used to assist in posi-tioning and also to help in immobilizing the head andneck. The shoulders may be taped down distally to facil-itate fluoroscopic visualization of the cervicothoracicjunction. The arms are carefully padded and wrapped tothe sides. If autologous bone is required for grafting, theanterior iliac crest may be prepared. A horseshoe orMayfield head rest is padded with a soft roll, adapted,

156 PART II OPERATIVE ORTHOPAEDIC PROCEDURES

Figure 14-1. Posterior surgical anatomy of the cervi-cal spine.

Figure 14-2. Sagittal view of the pathologic anatomyof the upper cervical spine in inflammatory arthritis.There is atlantoaxial subluxation and the posterioratlanto-dens interval (PADI) is reduced.

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and secured. After the anesthesiologist has secured theairway, the surgeon should hold the patient’s head andgently extend the neck slightly. Most of this extensionshould involve the occipitocervical junction. Once ade-quate positioning has been obtained, the head rest issecured and, if necessary, a head halter or tong tractionapplied. Finally, the head of the bed is slightly elevatedto decrease venous bleeding. The knees can be raised toprevent the patient from sliding down during the opera-tion and to protect the sciatic nerve from traction injury.

Positioning for Posterior Cervical ExposureFor posterior cervical exposure, the neck must bealigned close to neutral, with some degree of forwardthrust of the head. If instability is caused by flexion, caremust be taken not to increase traumatic deformity. Whenoccipitocervical and/or atlantoaxial fixation is planned,flexion of the head creates space for exposure andinstrumentation by maximizing the distance between theocciput and the posterior arches of the atlas and axis. Ahorseshoe or Mayfield head rest is recommended. Inoccipitocervical fixation the head should be aligned in afunctional position at the time the implants are fixed.

For both anterior and posterior procedures, the armsare carefully positioned next to the body, with elbows,wrists, and hands well padded. Wrist straps may be usedfor traction, especially for lower cervical or cervicothoracicfusions. In this situation, lateral fluoroscopy may be verydifficult because the shoulders may obstruct the x-rays;therefore downward traction of the shoulders may beneeded.

Potential complications due to positioning includenerve trauma at the ulnar tunnel, at the carpal tunnel, or inthe axillae. In the lower extremities, the most commonnerve compression syndromes associated with positioninginclude femorocutaneous and peroneal nerve palsies. Theorbits should also be free of any external compression.

Authors’ Surgical Technique

Anterior Cervical Decompressionand Fusion (ACDF)The anterior exposure to the cervical spine has beenwidely used since its original description in 1958. Asdescribed, this approach is useful for single- or multiple-level diskectomy and cervical corpectomy. The removal ofa vertebral body is useful in trauma where the thecal sac isinvaded by a fragmented vertebral body or as an alterna-tive to multiple-level diskectomy and interbody fusions,where the pseudoarthrosis (nonunion) rate increases inproportion to the number of levels of attempted fusion.

Magnification is recommended, and the skin isincised horizontally, starting from the midline andextending laterally. The surface landmarks for the inci-sion are the hyoid at C3, the thyroid cartilage at C4–C5,

and the cricoid cartilage at C6. A longitudinal incisionfollowing the anteromedial border of the sternocleido-mastoid muscle is indicated for the treatment of multi-level surgery, as for two or more vertebrae. With a prop-erly placed horizontal incision, up to three diskectomiesmay be performed. If multiple corpectomies are planned,a longitudinal incision is preferred.

Following incision, the platysma muscle is dividedlongitudinally, strap and sternocleidomastoid muscles areidentified, and the superficial layer of fascia is divided(Fig. 14-3). The pretracheal fascia is exposed, and the strapmuscles are divided longitudinally to identify the medialborder of the carotid sheath. The omohyoid muscle maybe transected if more extensive exposure is required. Thestrap muscles, trachea, and esophagus are retracted medi-ally, and the prevertebral fascia is exposed. A needle isused to mark the appropriate disk space, and AP and lat-eral fluoroscopy is used to confirm the appropriate level,and the midline.

Once the appropriate disk space is confirmed, theprevertebral fascia and longi colli muscles are dissectedand Cloward-type retractor blades are placed with thedistal lips lying deep in these muscles. All static retractorscause pressure on the soft tissues, including the airway,carotid artery, and internal jugular vein; this pressureshould therefore be relieved at regular intervals. It maybe advantageous to reduce the endotracheal cuff pres-sure to avoid mucosal ischemia.

CHAPTER 14 THE ADULT SPINE 157

Figure 14-3. Cross section through the neck demon-strating the intermuscular approach to the anteriorcervical spine.


The disk is then removed, as are anterior osteophytes.To visualize the posterior annulus and spinal canal, thevertebrae are distracted with a Cloward distractor orCaspar spreader. Microsurgical curettes, Kerrison rongeurs,and a nerve hook are used to complete the diskectomy andexamine the spinal canal for evidence of any compressingelements. If disk material is suspected to be lying posteriorto the posterior longitudinal ligament (PLL), this is removed,avoiding pressure on the dura. Free disk fragments areremoved with a pituitary rongeur.

After decompression, arthrodesis is done by posi-tioning a graft between the endplates. The distractor sys-tem is removed, and fluoroscopy is used to confirm cor-rect placement. A low-profile titanium plate may also beadded for increased stability (Fig. 14-4).

If two adjacent disks have been removed, a Leksellrongeur is used to create a trough in the vertebral body.The remainder of the vertebral body is then burreddown to the posterior cortex, which is finally removedwith curettes and a Kerrison rongeur. The lateral marginsof the corpectomy must always be limited to the projec-tion of the uncovertebral processes in order to protectthe vertebral arteries.

The muscles are repositioned and the platysma andsubcutaneous tissue layer and skin sutured. The patient’sneck is stabilized with a cervical orthosis.

Posterior Cervical Decompressionand FusionAfter prone positioning of the patient and surgical prepa-ration, a vertical incision is made from the superioroccipital protuberance to the prominent spinous processof C7. Epinephrine (1:500,000) may be used to help withhemostasis. After dissection of the subcutaneous tissuelayer, the trapezius fascia and paraspinal muscles are dis-sected from the tip of the spinous processes, extendinglaterally to the lateral aspect of the articular processes.Dissection beyond the facet joints or articular processesmay result in denervation of the muscles and may alsothreaten the vertebral artery. Intraoperative x-rays or flu-oroscopy are used to confirm the correct anatomic site.Decompression procedures—including foraminotomy,laminectomy, and laminoplasty—are carried out throughthis exposure (Fig. 14-5). In laminoplasty, the posteriorarch is hinged open to increase the AP diameter of thespinal canal, thus maintaining the integrity of the poste-rior tension band. Laminectomy also allows decompres-sion of the thecal sac, but this may compromise the sta-bility of the spine. Foraminotomy allows access todecompress a single nerve root without compromisingspinal stability.


Figure 14-4. View of the anterior exposure of thecervical spine. A corpectomy has been replaced byinterbody strut graft and anterior plate reconstruction.

Figure 14-5. Posterior approach to the cervicalspine with a laminoplasty. Note that the laminae havebeen hinged open, the so-called open door.


Screws may be placed into the lateral articularprocesses. The technique described by Magerl is the mostpopular owing to its many biomechanical advantages andbecause it protects the neurovascular structures, thoughnot completely. This is so especially during drilling, whichis targeted cranially from 30 to 40 degrees, following thedirection of the superior articular surface and laterally 25to 30 degrees to avoid the vertebral artery. The screws areconnected to plates or rods, providing rigid fixation of thesegments with disordered motion.

The articular surfaces and the lateral processes areprepared for arthrodesis with a high-speed burr so as toprovide decorticated bone for bone graft only. Finally,the wound is closed in three layers and a cervical ortho-sis applied.

Occipitocervical FusionWith the patient in the prone position, a midline incision ismade from the caudal aspect of the occiput to the C3 spin-ous process. The deep dissection is kept as close to themidline as possible, although the median raphe or liga-mentum nuchae may follow a tortuous course, making itdifficult to remain in an avascular plane for the dissection.The ligamentous attachments of the C2 spinous processare identified and subperiosteally elevated. The exposureextends no further than the medial one-third of the facetjoint between C2 and C3. The midline of the occiput isexposed subperiosteally. The posterior tubercle of C1 ispalpated and subperiosteal dissection performed.Excessive pressure on the posterior arch of C1 can causeaccidental penetration of the atlantooccipital membrane,which may injure underlying structures. The dura can beespecially vulnerable in cases of C1–C2 instability. The ver-tebral artery and vein are vulnerable beyond a point 15 mmfrom the midline as the artery courses from a slightly pos-terior foramen transversarium of C1 in a posteromedialdirection to enter the foramen magnum, just cephalad ofthe ring of C1. If the atlantooccipital membrane is acciden-tally penetrated proximally to the superior border of thering of C1, the vertebral artery lies more medial, where itmay be vulnerable. Arterial bleeding in this location mayhave disastrous consequences. Additional care must betaken when these structures are being dissected in rotatorydislocations of C1–C2, because the vertebral artery isstretched across the joint where C1 is dislocated anteriorly.

After dissection, instrumentation is started by insert-ing 4.5- to 5.25-mm screws into each side of the occiput,avoiding penetration of the skull. Cerebrospinal fluid(CSF) may leak, but this stops once the screw is placed.Ideally, three screws per side are placed.

Transarticular C1–C2 screws are then placed startingat the midline of the caudal aspect of the inferior facet ofC2, aiming toward the lateral mass of C1 through theC1–C2 joint. This procedure is fluoroscopically guidedand provides reliable fixation of this joint. Additionally, a

sublaminar wire loop is passed under the posterior archof C1 and anchored under the spinous process of C2.The free ends are used to hold an H-shaped bicorticalautograft from the base of the occiput to the posteriorarch of C2. The wires are tied, firmly fixing the graft, andthe transarticular screws are connected through a rod tothe occipital screws. The wound is then closed in threelayers and a cervicothoracic orthosis (CTO) is applied.

Anesthetic Considerations

Spinal Cord MonitoringSpinal cord monitoring is widely used during cervicaland thoracic spinal procedures. Intraoperative neuro-physiologic monitoring of the spinal cord has provenbeneficial in minimizing the risks of neural injury duringsurgery.

The Wakeup TestTraditionally, the wakeup test (WUT) has been consideredthe “gold standard” that provides a “snapshot” of the neu-rologic situation. This test is performed after instrumenta-tion, decompression, and correction of the deformity havebeen completed. It consists of decreasing the anesthesia,typically by administering an infusion of remifentanil oralfentanil with propofol or inhalational anesthesia to thepoint where the patient is able to follow verbal commands.The patient must be fully reversed from any neuromuscu-lar blocking agents and is first asked to squeeze the anes-thesiologist’s hand to indicate his or her ability to respondand then to move the feet and toes. If hand movementoccurs but foot movement does not, the surgeon will undocorrective procedures or remove implants invading thespinal canal in order to reassess the situation. Removal ormodification of instrumentation within 3 h after the onsetof a neurologic deficit may significantly decrease perma-nent damage. Spinal cord perfusion and oxygenation mustbe optimized. High doses of steroids can be used to pre-vent the progression of secondary injury to the spinal cord,but this is controversial.

Because inhalational anesthetics make timing of thewakeup test very difficult, opioids like remifentanil withnitrous oxide and propofol or ketamine are anestheticagents of choice. Risks involved with the wakeup testinclude accidental extubation, dislodgment of instru-mentation, injury, bronchospasm, recall of intraoperativeevents, and psychological trauma, air embolism, and car-diac ischemia. Success and safety are therefore verydependent on informing the patient properly before-hand. Midazolam is also helpful in causing anterogradeamnesia.

Somatosensory Evoked PotentialsSomatosensory evoked potentials (SSEPs) allow for con-tinuous assessment of spinal cord function, primarily the



function of the sensory system. The negative predictivevalue of SSEPs is reported to be 99.93 percent, and thisassessment is started immediately after the induction ofanesthesia. A peripheral nerve, usually the posterior tib-ial nerve at the ankle, is stimulated, and cortical poten-tials are recorded with surface electrodes. Early positivepotentials after stimulation are recorded at 31 ms (P31),followed by a small negative potential at 35 ms (N35)and subsequent sizable positive potentials at 40 ms(P40). The P31 potential arises from the brainstem and ismore consistent and resistant to anesthetic agents thanP40, which is a cortical response. An increase in latencyand decrease in amplitude may be observed at clinicallyused concentrations of inhalation anesthetic agents. Thisdecreases the specificity and sensitivity of the monitor-ing. This false-positive response is dose-dependent. Ithas been determined that 0.5 MAC of halothane or 1.0MAC of isoflurane, sevoflurane, or enflurane combinedwith 50% nitrous oxide will provide adequate sensitivityand specificity of the monitoring. Data for desflurane arenot available. Additionally, stable spinal cord blood flowand oxygenation provide more consistent responses.This requires normal temperature and blood pressure aswell as optimal oxygenation, hematocrit, and glucose.

Motor Evoked PotentialsMotor evoked potentials (MEPs) are motor responses ofthe limb muscles obtained by transcranial electrical stim-ulation or by magnetic pulse stimulation of the motorcortex. A brief muscle response is recorded in the lowerextremities. This tests the pathways of the motor neu-rons. Transcranial electrical stimulation requires theapplication of high voltage and may be painful to theconscious patient. Magnetic stimulation is not painful butrequires a sizable coil and cable that is extremely sensi-tive to positional changes, making its use during surgeryimpractical. Electrical stimulation thus seems more prac-tical for intraoperative monitoring. MEPs are also verysensitive to anesthetic agents. Halogenated inhalationalagents must be avoided. Nitrous oxide also interfereswith MEP recordings and may be used as an adjunct topropofol anesthesia with a concentration below 50%.Neuromuscular blockade makes this type of monitoringof spinal cord function impossible, but neuromuscularblockade to one to two twitches of the train-of-fournerve stimulator monitor may be permissible. It is impor-tant to discuss the problem with neurophysiologistsbefore neuromuscular blocking agents are used.

Postoperative Analgesia

Anterior cervical exposure requires little dissection; tissuedisruption and postoperative pain are therefore limitedand little analgesia is required. Most commonly, the phar-ynx and larynx are edematous and inflamed, causing

dysphagia. This requires alimentation with cool fluids aswell as mashed and semisolid foods until symptoms sub-side. If bone was removed from the iliac crest for grafting,this commonly becomes the main source of pain.

Pain following posterior cervical exposure requiresmore analgesia because tissue disruption is greater thanwith anterior exposure. The patient with spinal cordinjury also suffers from pain at the operative site and mayalso have other complex regional pain or neuropathicpain syndromes that necessitate intensive management.

Associated Medication

Antibiotic prophylaxis is similar to that in other muscu-loskeletal procedures where implants are used. Modernguidelines for using prophylactic antibiotics are outlinedin Chap. 4.

A further consideration is the use of steroids. Apatient admitted with a spinal cord injury will havereceived high-dose steroid therapy. This usually includes30 mg/kg of methylprednisolone (Solu-Medrol) as abolus diluted in normal saline and infused over 30 min.Thirty minutes after this bolus has been completed, acontinuous infusion of methylprednisolone at 5.4mg/kg/h is initiated for 24 or 48 h. Although this proto-col is currently considered the standard of care in mostemergency department settings, its use remains a matterof controversy. Not only has its usefulness been ques-tioned but it has also been pointed out that high-dosesteroids may increase perioperative morbidity, particu-larly surgical-site infection, pneumonia, and gastroin-testinal hemorrhage. Finally, existing studies lack controlfor surgical interventions, stratification of the patientpopulation, and the use of summed motor scores andfunctional assessment of improvement in motor func-tion. Mortality after hospitalization for spinal cord injurycurrently reaches approximately 7 percent in the firstyear; this is attributed mainly to multiple trauma and res-piratory and infectious complications. Mortality isdirectly proportional to the level of injury and thepatient’s age. Although not proved by evidence in theclinical literature, the timing of surgical intervention maybe a key factor determining neurologic outcome. Thereis wide support for early surgical intervention and earlyrehabilitation. Improved nursing care and attempts toreduce systemic complications seem to be among themost important factors that reduce mortality and improveneurologic outcome.

Physical Therapy Goals andRequirements in thePostoperative Period

Reconstruction procedures of the cervical spine often pro-vide enough stability to allow the patient to begin rehabil-itation. If there is doubt about stability or bone quality, a



cervical orthosis must be used to protect the bone-implantinterface. Upper extremity loading is restricted until fusionis achieved. Exposure to potential trauma is also avoided,including participating in sport—especially contact sport,use of all-terrain vehicles, horseback riding, etc.

For patients with anterior cervical decompressionand fusion, out-of-bed activities are encouraged on theday of surgery, and patients are usually discharged fromthe hospital after 1 or 2 days. Generally one or two visitsby the physical therapist and occupational therapist aresufficient to provide instructions on care and independ-ence in daily activities. Patients subject to more extensiveposterior procedures may require an additional day ofhospitalization for pain control.

In cases of spinal cord injury, the reconstruction ofthe spine should be stable enough to allow for all reha-bilitation procedures, including pulmonary rehabilita-tion, orthostatic rehabilitation, the acquisition of transferskills, and self-care.

Special Intra- and PostoperativeSurgical Requirements

The Unstable Cervical SpineThere is currently no consensus on the definition of clin-ical instability of the spine. It has been defined as the lossof the capacity of the spine to support physiologic loadswhile still maintaining a harmonious relationship betweenthe vertebrae in such a way that there is neither initialnor subsequent damage to the spinal cord or the devel-opment of incapacitating deformity or pain. A checklistthat facilitates its clinical application has also accompa-nied this definition. The checklist also includes imagesthat reveal destruction of the bony architecture, thepresence of neural deficit, anticipated dangerous load-ing, spinal canal narrowing, and static/dynamic (flexion-extension) radiographic signs (>3.5 mm of subluxationor more than 11 degrees of focal kyphosis). For thepatient who undergoes general anesthesia, the mostimportant predictor of paralysis is the space available forthe cord (SAC). The SAC is the distance between the pos-terior cortex of the vertebral body and the spinolaminarline. In a cohort of 49 patients with rheumatoid arthritiswho underwent joint arthroplasty, almost 50 percentpresented criteria for instability with subaxial sublux-ation of the cervical spine >3 mm; nevertheless, only8 percent presented with SAC ≤13 mm.

At the level of the atlantoaxial complex, the SAC issignificantly greater than that in the subaxial cervicalspine. The “rule of thirds” describes the relationshipbetween the dens and the spinal cord inside the ring ofthe atlas. The dens and the thecal sac occupy one-thirdeach, leaving a safety margin of a third of the anteropos-terior diameter of the spinal canal. The relationshipbetween C1 and C2 is maintained by its lateral masses

and by the transverse ligament of the atlas. If the dis-tance between the anterior margin of the dens and theposterior margin of the ring of the atlas (atlanto-densinterval) exceeds 4 mm, then most likely the transverseligament is incompetent. Nevertheless, a SAC ≤13 mm isa major clinical predictor of spinal cord injury. The pos-terior atlanto-dens interval (PADI) represents the SAC atthe level of the atlas and has a negative predictive valueof 94 percent for the development of paralysis if themeasurement is greater than 14 mm. The PADI is espe-cially useful in determining risks for chronic atlantoaxialinstability, such as rheumatoid arthritis and Down’s syn-drome. Other conditions include the presence of ahypoplastic dens, os odontoideum, rheumatoid arthritis,or a pseudoarthrosis of the dens.

In cases of cervical instability, the unconsciouspatient is at particular risk. Fiberoptic endoscopicallyassisted intubation of the patient is preferable. The patientis turned and transferred to the operating table with a rigidcervical orthosis in position. Sometimes surgeons prefer toplace the patient in the prone position before generalanesthesia is induced. This allows for neurologic assess-ment after positioning. Common causes of cervical insta-bility include trauma and destructive lesions caused byinfection or malignant tumor growth.

Cervical StenosisThe patient with a narrowed cervical spinal canal may beat particular risk of developing central cord syndrome ifthe neck is extended. The normal sagittal diameter of thespinal canal in the subaxial cervical spine is approxi-mately 17 to 18 mm in healthy people, and the spinalcord diameter is approximately 10 mm in this sameregion. Cervical stenosis is defined as an anteroposteriorspinal canal diameter ≤13 mm by a Torg (Pavlov) ratioof less than 0.8. This ratio is the size of the spinal canalrelative to the anteroposterior dimensions of the vertebralbody. A Torg ratio of less than 80 percent represents arisk factor for the development of myelopathy in patientswith cervical spondylosis.

The dimensions of the spinal canal change with flex-ion-extension movements. When the neck is extended, thespinal cord may be compressed between the posterior ver-tebral bodies’ osteophytes projecting from the posterior lipof the inferior endplate and the superior border of thelamina of the vertebra immediately below, resulting in acentral cord syndrome. Flexion, on the other hand, resultsin tension forces on the spinal cord, and concomitantcompression of the ventral spinal cord against endplateosteophytes and disk material. Furthermore, during exten-sion, the cervical cord shortens and its cross-sectionalarea increases. Simultaneously, the ligamentum flavumbulges inward to further reduce the SAC and compress thespinal cord. Neck extension poses the greatest risk of cordinjury because the SAC is narrowed with simultaneous



expansion of the cervical cord. Neutral alignment of theneck must thus be maintained at all times, since that posi-tion provides the largest SAC.

Patients with a significant risk of spinal cord com-pression and ischemia, due either to traumatic instabilityor stenosis, should be stabilized before anesthesia induc-tion. This is possible only for anterior cervical exposurewith the patient supine. Fiberoptic assisted intubation inawake patients is mandatory to prevent manipulation ofthe neck. When awake, the patient is able to providefeedback, and continuous neurologic assessment is pos-sible. If anesthesia must be induced before positioningthe patient, as for posterior cervical exposure, it is impor-tant to position the patient with a rigid cervical orthosisconstantly in place.

Complications

Neurologic InjuryInjury to the spinal cord is probably the most fearedcomplication associated with spinal procedures. TheCervical Spine Research Society has surveyed 5356 casesand has reported an incidence of 1.04 percent neuro-logic complications, with 0.2 to 0.4 percent of thesebeing spinal cord injuries. The figure was lower for anteriorprocedures than for posterior procedures. Intraoperativemanagement as well as the principles of prevention havebeen described earlier.

Vascular ComplicationsAlthough ACDF involves minimal blood loss, theapproach involves displacing the carotid sheath and all itscontents. Although injury to the carotid artery is extremelyrare, bradycardia may result from a vasovagal responsecaused by retraction of the carotid sheath. Other struc-tures that may bleed during and after surgery are the thy-roid vessels as well as the superficial jugular vein.

Vertebral artery laceration is rare, with a reportedincidence of 0.5 percent. These injuries usually occurduring cervical corpectomy. Anatomic variants of the tra-jectory of this artery and excessive lateral resection of thevertebral body are the key factors. The vertebral artery isapproximately 5 mm from where a decompression isperformed at the C6 level and is situated in the posteriorquarter of the vertebral body, allowing a very narrowmargin of safety when the lateral nerve roots are beingdecompressed.

Control of bleeding from vertebral artery laceration isdifficult. Ligation may result in cerebellar infarction withcranial nerve palsies, transient dysphagia and dysarthria,persistent posterior fossa circulatory insufficiency, vocalcord paralysis, and quadriplegia. A report on 100 patientswith vertebral artery ligation gave a mortality of 12 percent,secondary to brainstem ischemia.

Postoperative Visual LossThis devastating complication of spinal surgery has fre-quently been reported in the literature on anesthesia inorthopedics and neurosurgery with an incidence ofapproximately 0.2 percent. In an attempt to identify riskfactors and preventive measures, the American Societyof Anesthesiologists developed the “postoperative visualloss (POVL) registry” in June 1999 and had registered 79cases by the end of summer 2003. Although this does notrepresent the true occurrence of this problem, this reg-istry revealed some interesting facts. First, ischemic opticneuropathy (ION) was by far the most common cause ofvisual loss. Second, the most common procedures asso-ciated with POVL were spine surgery (54 percent) fol-lowed by cardiac surgery (10 percent). Third, most of thespinal cases involved prolonged prone positioning(median 8 h) and large blood losses (median 2.3 L). Agedoes not seem to matter. Some cases occurred in young,healthy patients with 3 h prone time and minimal bloodloss. Nevertheless, the incidence does seem to increasedramatically for prone times ≥5 h. Venous congestionmay be important, in association with hypotension andanemia.

Finally, of the spine surgery cases in the prone posi-tion that developed POVL, 77 percent had their headspositioned with a foam support and 18 percent withMayfield tongs.

Other Complications

Horner’s syndrome may occur because of an injury tothe cervical sympathetic plexus. This plexus lies withinthe longi colli muscles and can be injured by dissectionor excessive pressure from a retractor blade. The syn-drome may be temporary or permanent.

The recurrent laryngeal nerve may be damaged,causing hoarseness and vocal cord paralysis. The hoarse-ness is usually temporary, but cases have been reported inwhich the vocal cords were permanently paralyzed. Caremust be taken when considering a second procedure withcontralateral exposure. Visual inspection of the vocalcords is recommended before surgical intervention.

Laceration of the dura is uncommon during cervicalspinal surgery. If it does occur, repair should be attempted.Possible complications include dural-cutaneous fistula,secondary Arnold-Chiari phenomenon, and cranial nervedysfunction. The thecal sac may be lacerated as a result ofa traumatic injury or may be damaged during ossificationof posterior longitudinal ligament (OPLL) surgery.

Postoperative dysphagia is a common yet underre-ported problem, which may last up to a year. This com-plication has been reported in up to 50 percent ofpatients 1 month after surgery and in 12 percent ofpatients after 1 year. The dysphagia is commonlymechanical but may also be accompanied by odynopha-gia, breathing difficulties in 18 percent, and pneumonia



during the early postoperative period. Patients with gas-troesophageal reflux disorder are more likely to experi-ence breathing difficulties in the postoperative period.The etiology of dysphagia is not completely understood.

During the procedure, inadvertent perforation of theesophagus may occur. This is a very serious complication,including the development of osteomyelitis, abscess forma-tion, and mediastinitis. The incidence of this complicationhas been reported to be between 0.2 and 0.9 percent of allanterior cervical exposures, and one-third of these injuriesoccur during surgery. Protruding graft, hardware, or cement,which may erode the esophagus in the postoperativeperiod, accounts for the other two-thirds. Early recognitionand immediate management are vitally important.

In the postoperative period, the most urgent compli-cation is acute respiratory distress due to cervicalhematoma. Careful intraoperative hemostasis as well as apostoperative drain deep to the aponeurosis help to pre-vent this problem. Immediate treatment includes orotra-cheal intubation. A cricothyroidotomy may be lifesaving,along with immediate drainage of the hematoma. If thepatient has been subjected to prolonged surgery, espe-cially in the prone position, edema may develop aroundthe neck and compromise the upper airway. Steroid ther-apy may be useful in coping with this complication.

Finally, although extremely uncommon, a hematomaof the spinal canal may develop. This will lead to progres-sive neurologic deterioration. This situation also requiresimmediate exploration. The diagnosis is confirmed by mag-netic resonance imaging (MRI) or computed tomography(CT) myelography.

� THE THORACIC SPINE

Indications and Special AnatomicConsiderations

The thoracic spine provides structural support, limitedmotion, and protection of the neural elements. The sta-bility and rigidity of this part of the spine partiallydepends on its relationship with the rib cage through thecostovertebral and costotransverse joints. Injury to theheads of the ribs is an indirect sign of significant tor-sional stress on the spine and must not be overlooked. Inaddition, the close relationship with the mediastinumand lungs must warn of potential injuries to these struc-tures, especially when there is evidence of translationalor shearing forces that have acted on the thoracic spine.

Posterior surgery to the thoracic spine includes thatfor the correction of deformities, stabilization after traumaor tumor resection, and decompression of the thoracicspinal cord. Anterior surgery is most commonly under-taken for decompression of the thoracic spinal cord fromtrauma, tumor, infection, or degenerative pathology suchas thoracic disk herniation. Anterior surgery also plays an

increasing role in the correction of deformities, alone orcombined with a posterior procedure. More detail on thecorrection of deformities in the pediatric population isgiven in Chap. 14.

Patient Profile

The patient profile ranges from the healthy young adultwith a deformity or a herniated disk to the chronically illpatient with an infection or tumor.

It must be always kept in mind that the enormousenergy required to injure the thoracic spine may havedamaged other organs or systems. With lung contusions,prone positioning of the patient may potentially disruptpulmonary blood flow and cause ventilation/perfusionmismatch.

Similar considerations apply to patients with spinalcord injury, such as those described in the discussion ofthe cervical spine, above. In thoracolumbar trauma, thepatient with paralysis is even more likely to have occultabdominal or thoracic trauma, which must be thoroughlyevaluated.


For the anterior exposure to the thoracic or thoracolum-bar spine, a thoracotomy is required. This exposure sig-nificantly decreases the values of pulmonary functiontests (PFTs) for up to 2 years. Patients with previous lungdisease must be carefully evaluated, and planning for thepostoperative period is mandatory. Ventilatory assis-tance may be required after surgery. In patients withinjuries to the thoracolumbar spine, pulmonary contu-sion may be relevant in deciding on the timing and lat-erality of the surgical exposure. Spinal instability will notallow adequate mobilization of the patient, and it may beimpossible to achieve adequate pulmonary function.Gas exchange can be further compromised by single-lung ventilation during spinal surgery, and the surgicalteam must decide whether the patient will be able to tol-erate one-lung ventilation for several hours.


Posterior Approach to the Thoracic SpineThis exposure requires prone positioning. Most sur-geons prefer to use a four- or five-post frame. The face ispositioned on contoured foam, taking care to preventpressure and congestion around the eyes. Some deviceswith a mirror allow continuous observation of endotra-cheal tube placement. Care should also be taken toavoid compression of the abdomen, since this increasesvenous congestion and intraoperative bleeding fromvenous epidural sinuses. Decompression of theabdomen and inferior vena cava reduces epidural bloodflow, which allows better visualization of structures in



the spinal canal. If the fusion is carried into the lumbarspine, preservation of the sagittal alignment is essential.This is further discussed below, under positioning forlumbosacral fusion exposures.

The superior posts should be positioned under thepatient’s rib cage, while the inferior posts should bepositioned underneath the anterior iliac spine. For heav-ier patients, a transverse post across the superior chest,two posts on the inferior rib cage, and two posts on theiliac crests are used. The legs are supported with pillows.Care should be taken to prevent excessive pressure onthe breasts in female patients.

The arms are positioned with 90 degrees or more offlexion of the elbows and 90 degrees or less abduction ofthe shoulders. The arms rest on well-padded boards, andspecial care is taken to avoid pressure on the ulnar groovesand the wrists. The axillae must also be protected againstcompression.

Prone positioning checklist:No pressure on eyes to ensure normal retinal blood

flowEndotracheal tube unobstructedHead not lower than heart to prevent cerebral con-

gestion and decreased cerebral blood flowNeck not extended but neutralAbdomen free to prevent venous congestion,

increased bleeding, and epidural venous con-gestion

Breasts not compressedMale genitals free and not compressedUrinary catheter free and not compressed or

obstructedLegs supported; femoral nerves free from com-

pressionShoulders abducted 90 degrees or lessElbows flexed 90 degrees or lessUlnar nerves free and not compressedMedian nerves at wrists free of compression; wrists

neutralVentilation bilateral and normalIntravenous and arterial lines free and unobstructed

Anterolateral Approach to the Thoracic Spine This exposure requires lateral positioning, usually on thepatient’s right side. The left-sided exposure is the mostconvenient, especially for the lower thoracic spine andthoracolumbar junction. Retracting the right hemidi-aphragm may be difficult. The spleen is smaller and there-fore easier to retract than the liver. In addition, the venacava (on the right side) can be lacerated more easily thanthe aorta. Because of its pulsation, the aorta is easier tolocate on the left side (Fig. 14-6). This is especially impor-tant when resection includes soft tissue mass extensionfrom tumor or infection. Nevertheless, there are conditionswhen a left-sided exposure will not be convenient, as in

the correction of scoliosis with a right-sided curve. If theoperation involves the upper thoracic spine (T1–T4), it isconvenient to approach the spine from the right side so asto avoid the aortic arch. If the vertebral bodies are small, asin small people, spinal implants may be relatively promi-nent and the aortic wall may be eroded by the pulsationsof the artery against them. The right arm is abducted andflexed as far cephalad as possible to allow mobilization ofthe scapula anteriorly and superiorly. Since left-sidedexposures are more frequent, the following descriptionconsiders the patient lying on his or her right side.

The patient is transferred to the operating table in asupine position. After anesthesia has been induced andthe endotracheal tube (usually a double-lumen tube tofacilitate one-lung ventilation) is inserted, the patient isturned to a lateral decubitus position and a roll is placedunderneath the axilla to prevent circulatory disturbanceto the right arm (Fig. 14-7). Most surgeons prefer silicone


Figure 14-6. Left-sided thoracotomy exposure. Thelung has been retracted anteriorly, and the dome ofthe left hemidiaphragm is observed.


padding. Foam padding is also placed underneath theright leg from the hip down to the foot. The head is sup-ported with pillows or foam, maintaining neutral align-ment of the neck. The trunk is supported on the sternumand the back by padded supporting attachments or by abeanbag. The pelvis is supported by adhesive tape orstraps over the left greater trochanter, which is alwaysprotected by foam padding. In procedures involvingdecompression of the spinal canal or instrumentation ofthe spine, stable positioning is important for surgical ori-entation and intraoperative imaging. The right arm issupported by a foam-padded arm board with the shoul-der at 90 degrees of extension and the left is extended ontop of this, separated by pillows or other soft padding.Special supporting devices for the upper arm are avail-able. Some surgeons prefer to flex the table at thepatient’s waist in order to increase the space between theribs. Tilting the table into a reverse Trendelenburg posi-tion facilitates retraction of the hemidiaphragm by dis-placing the abdominal viscera caudally. This positionalso facilitates venous drainage and decreases surgicalbleeding from the epidural venous sinuses or obstruc-tion of vision by them.


Posterior Spinal Fusion and InstrumentationAfter a standard midline incision of the skin and subcu-taneous tissues, the thoracic fascia and paraspinal mus-culature are dissected in a subperiosteal manner with abovie cautery and a Cobb elevator. After the skin inci-sion, 1:500,000 epinephrine may be used to providehemostasis. Stripping of the muscles subperiosteally pre-vents muscle tearing and excessive bleeding. Self-retainingretractors are inserted, and tissue ischemia is avoided byintermittently decreasing the pressure. The facet jointcapsules are stripped and the cartilage removed with theuse of a high-speed burr and curettes. Care is taken toavoid injury to the facet joints that are not to be includedin the fusion. Intraoperative x-ray or fluoroscopy is con-venient at this point to confirm the levels to be operatedon. To prepare the spine for fusion, the transverseprocesses and laminae are also decorticated with the useof a high-speed burr.

Instrumentation consists of sublaminar hooks, pedi-cle screws, and rods. Hooks are placed either facing in acaudal direction and anchored over the superior border ofthe lamina or facing in a cephalad direction and anchoredunder the inferior border of the lamina. To place eachhook, the ligamentum flavum is removed from its attach-ment with a curette; once the spinal canal is visualized, aKerrison rongeur is used to square off the anchoring pointon the lamina. Hooks of different sizes and angulationsare available and are determined by the orientation anddimensions of the lamina and spinal canal. The hookswill occupy a portion of the posterior spinal canal. Thenumber of hooks and the pattern of placement areplanned before surgery and depend on the correctivemaneuvers that are deemed necessary. Once all hookshave been positioned, they are connected with rods, andcompression or distraction forces are applied as appropri-ate. These forces may significantly modify the contoursand dimensions of the spinal canal.

The bone graft is placed laterally, over the decorti-cated transverse process and along the lateral aspect ofthe lamina and decorticated pars interarticularis regionas well as on the facet joints. Finally, the wound is closedin three layers.

Thoracoabdominal Approach forCorpectomy and ReconstructionInjuries to the thoracolumbar spine frequently occur atthe thoracolumbar junction (T10–L2). Corpectomies ofthese transitional segments or instrumentation for defor-mity correction requires thoracoabdominal exposure.This starts with a skin incision placed over the 10th rib(Fig. 14-7). If the approach involves higher levels, the ribchosen is at the level of the affected vertebral body orone level higher. For the upper thoracic spine (T1–T4),


Figure 14-7. Positioning and skin incision for left-sided thoracoabdominal exposure.


the arm is placed as far cephalad as possible so as tomobilize the scapula anteriorly and superiorly.

The musculature is divided in line with the riband includes the latissimus dorsi and external oblique(Fig. 14-8). The rib is dissected subperiosteally and is cutfrom the costochondral junction anteriorly and as far pos-terior as possible. After removal of the rib, the abdominalmuscles are transected with a bovie cautery, in line with theskin incision. The posterior aspect of the approach shouldnot reach the midline. The costochondral cartilage isdivided longitudinally, exposing the retroperitoneal space.The peritoneum is dissected bluntly from the abdominalwall and from the undersurface of the diaphragm andforced distally toward the side opposing the approach. Thechest cavity is opened along the rib bed by longitudinaldivision of the parietal pleura. Wet laparotomy sponges areplaced on the borders of the thoracotomy, and a ribspreader is placed to allow for better visualization. The lungis retracted with a sponge-covered malleable (Fig. 14-6). Atthis point, the spine is identified and the posterior parietalpleura are incised in line with the midline of the vertebralbodies. Dissection is started over the intervertebral disksbecause they are easy to identify. Next, the segmental ves-sels are identified in the midline of the vertebral bodies.These vessels are elevated with a dissector and ligated orclipped and successively cut. If these vessels are cut toonear the aorta, there is a risk of bleeding from an orifice inthe aorta. On the other hand, if they are cut too near the

foraminae, blood flow to the spinal cord may be compro-mised. The midthoracic spinal cord has the least abundantblood supply and the narrowest bony confines. The ante-rior spinal artery is smaller in diameter and in 85 percent ofthe cases depends mainly on a single accompanyingradiculomedullary artery that arises somewhere from T9through L2 (artery of Adamkiewicz). The segmental arter-ies contribute to the anterior medullary artery through theanterior radicular branch. Collateral circulation is usuallypresent in close proximity to the foramen and includesanastomoses at the same foraminal level distal to the lig-ated segmental artery or by radicular arteries originatingfrom adjacent segmental vessels. This critical zone of thespinal cord may predispose the patient to an ischemicinsult to the cord after ligation of the segmental vessels,especially if cut too short from these anastomoses. Somesurgeons favor temporary ligation and evaluation of theSSEPs. In our experience, ligation of the segmental vesselsin the midportion of the vertebral body has proven to be asafe procedure. After ligation, the mediastinal structuresare easily displaced and a malleable retractor is placed forprotection during the procedure.

The diaphragm can be circumferentially transectedapproximately 2 cm from the chest wall insertion. If it issectioned too peripherally, reconstruction may be verydifficult; if too medially, hemostasis may be difficult andthe phrenic innervation may be compromised. Differentor alternate colored marking sutures are placed, whichwill enable appropriate reconstruction at the end of theprocedure. If the dissection continues distally into theupper lumbar spine, the psoas muscle should be cau-tiously dissected off the anterior surface of the lumbarvertebral bodies, or the lumbar plexus may be injured.

For the upper thoracic spine, the skin incision sur-rounds the inferior and medial aspects of the scapularwing. The trapezius muscle is dissected along the skinincision, and latissimus dorsi muscles are dissected as farcaudally as possible. When the rib cage is encountered,the dissection continues as described above.

When the exposure has been completed, the inter-vertebral disks are excised, starting with an incision inthe annulus fibrosus. The nucleus pulposus is removedwith curettes and pituitary rongeurs. If anterior release isnecessary for mobilization of the spine, the annulus andthe anterior longitudinal ligament must be circumferen-tially excised. Angled curettes and Kerrison rongeurs areused for this purpose. The surgeon’s fingertips shouldbe able to circumferentially palpate the disk, includingthe contralateral side of the exposure. A small portion ofthe posterior annulus and posterior longitudinal ligamentare left intact. After the diskectomy has been completed,endplates are freed of all cartilage with ring curettes toprepare them for fusion.

If the purpose of diskectomy is that of spinal canaldecompression, the rib head is removed by the use of


Figure 14-8. Thoracoabdominal exposure. The 10thrib has been resected and the parietal pleura opened.The lung and diaphragm are visible and the retroperi-toneal space is visible underneath the diaphragm.


osteotomes and a Kerrison rongeur, allowing access toand view of the spinal canal. Extruded disk material maybe removed by this route. If the purpose of the surgeryis a corpectomy to decompress the spinal canal frombone fragments, the ipsilateral pedicle may also beremoved, with great caution to protect the emergingsegmental nerve. The vertebral body, including the ipsi-lateral cortex, is excised with osteotomes, a high-speedburr, curettes, and pituitary rongeurs. The anterior andcontralateral cortices are preserved for protection of themediastinal structures. When the vertebral body hasbeen cavitated, the retropulsed bone is removed in aposteroanterior direction, away from the thecal sac. Theprocedure is completed when the dura is free of all com-pressing elements.

Finally, for the reconstruction of the spine, an inter-body strut graft is measured and placed between theadjacent endplates. A wide variety of materials may beused, including autograft, allograft fibula or humerus,titanium-mesh or carbon-fiber cages, according to thesurgeon’s preference. After reconstruction, a titaniumplate is secured to the adjacent vertebral bodies withbicortical screws, which are placed under fluoroscopicguidance.

When the decompression and reconstruction of thespine have been completed, the diaphragm is recon-structed with a running, nonabsorbable suture. Incompletereconstruction of the diaphragm may lead to the devel-opment of a hernia. The pleura may be closed with run-ning suture. Many times, due to the presence of theimplants, this is not possible. Revision procedures showevidence of complete epithelial coverage 2 weeks after a

pleural defect occurs. Some surgeons feel that insistenceon sealing a pleural defect may actually carry the medi-astinal structures closer to the metallic implants. Thechest is thoroughly lavaged and the lungs are allowed toreexpand. Careful inspection for air leakage or injuries tothe visceral pleura is carried out. One or two chest tubesare left in the chest cavity, and the chest is closed. First,the ribs are approximated with a nonabsorbable threadedinterrupted suture. The intercostal muscles and the pari-etal pleura are then closed with a running suture and sim-ilarly the latissimus dorsi on a separate plane.

Costotransversectomy ApproachThis is a posterior extrapleural approach that allows accessto the lateral aspect of the vertebral bodies (Fig. 14-9).The positioning of the patient is similar to that for posteriorspinal fusion. The incision may be in the midline or just lat-eral to the midline over the costotransverse junction. Afterdissection of the skin and subcutaneous tissues, the costo-transverse joint is approached through the erector spinaemuscles. The base of the rib and the transverse process areremoved. Great care is taken to avoid disrupting the pari-etal pleura. If this were likely to occur, the patient wouldhave to be warned that a chest tube might be required inthe postoperative period. The spinal canal and the dura areapproached by laminectomy and by removal of the ipsilat-eral pedicle. Great care is taken with the neurovascularbundle exiting caudal to the pedicle. The spinal cord issafely decompressed, with optimal visualization.Compressing elements on the midline, such as a centraldisk protrusion or OPLL, may not be accessible by thisapproach. This approach is not suitable for placement of a


Exiting nerve root

Neurovascular bundle

Azygos vein

Aorta

Spinal cord

Figure 14-9. Costotransversectomy approach. After resection of the ipsilateral pedicle,the spinal cord may be decompressed through a posterior approach to the thoracicspine.


structural interbody graft. The anterolateral approach ispreferred for these cases (Fig. 14-10).


Spinal cord monitoring is preferred for most operationson the thoracic spine. Anesthetic recommendations aresimilar to those described for cervical spinal procedures.

Measures to prevent iatrogenic spinal cord injury aresimilar to those described for cervical spinal procedures.In particular, hypotensive anesthesia is to be avoided,especially when the anatomy of the spinal canal is signif-icantly altered or when the thecal sac is manipulated.Similar considerations apply to anterior procedures whenthe segmental vessels are ligated.

Blood Loss and the Qualityof the Surgical FieldBleeding due to surgery to the spine is mainly fromvenous epidural sinuses. Arterial or capillary bleeding

plays no role or a very small role during spinal surgery.It is therefore important to keep the venous pressure aslow as possible while still maintaining cardiac filling andcardiac output. It is of no value to decrease the arterialpressure. Furthermore, measures that decrease the car-diac output, and therefore increase the central venouspressure, should be avoided. This includes the popularyet senseless practice of reducing the arterial blood pres-sure with beta-blocking agents. This will only serve toincrease the bleeding from venous sinuses and worsenthe surgical field.

Apart from keeping the blood volume optimal andadequately positioning the patient, keeping pressureoff the abdomen, venous dilators like trinitroglycerinwill further help to decrease bleeding. If the centralvenous pressure is abnormally high, it may even benecessary to administer small doses of furosemide. Acentral venous pressure lower than that of the surgicalfield will cause air to be sucked into the venous system,with resulting air embolism. Although this is rare, it maybe the cause of an otherwise inexplicable state ofhemodynamic instability. It is therefore essential tomonitor the central venous pressure and keep itapproximately at the same level as the main surgicalactivity.

Analgesia

When anterior exposure to the thoracic spine is used,intercostal block with 0.25% bupivacaine at the time ofclosure is recommended. Epidural block above andbelow the level of surgery provides excellent analgesia,and so does thoracic paravertebral block. These two pro-cedures provide short-term analgesia and help with pul-monary rehabilitation and ventilation. Recovery of venti-latory mechanics is fundamental for functional recoveryand in avoiding pulmonary complications. Pain manage-ment must be optimized, and we insist on the frequentuse of an incentive spirometer.

Patients who do not receive epidural or paraverte-bral block usually require intravenous morphine orhydromorphone patient-controlled analgesia (PCA) forthe first 24 to 36 h. Thereafter they are managed with oralopioids such as oxycodone.


Patients with spinal cord injury may be receiving highdoses of steroids. Steroids may also be given when mon-itoring indicates possible damage to the spinal cord dur-ing the operation.

Treatment with prophylactic antibiotics is started 1 hbefore the operation and repeated every 6 h during theprocedure. Thereafter, antibiotics are continued until allindwelling catheters have been removed, includingchest tubes and the urinary catheter.


Figure 14-10. View through a left-sided thoracotomyexposure. The intervertebral disk has been partiallyremoved. The segmental vessels are on the midpor-tion of the adjacent vertebral bodies.


Physical Therapy Goals andRequirements in thePostoperative Period

Patients undergoing surgery for deformity usually havevery stable constructs and require very little if any externalimmobilization. Out-of-bed activities are encouraged,with assistance, on the first day after surgery. Thesepatients can walk or sit on a recliner as tolerated. Ageobviously has an enormous influence on the speed ofrecovery. If there has been any anterior surgery, respira-tory therapy is started immediately. This includes use ofan incentive spirometer. Upright posture is encouragedbecause of its benefits for pulmonary toilette. Chest tubesare removed on the second to third days after surgery, andpatients with either anterior and/or posterior fusions aredischarged within 5 to 7 days. Physical therapy goalsinclude independent walking (may be aided by a walker),transfers, personal hygiene, and some stair steps. If thesegoals are not met within the first week, patients are trans-ferred to a rehabilitation facility for 2 to 4 weeks, espe-cially elderly patients.

The reconstruction of the spine should be stableenough to allow all necessary rehabilitation procedures,including pulmonary rehabilitation, and the acquisitionof transfer skills and self-care.


Lung retraction is probably one of the most importantconsiderations during anterior surgery to the thoracicspine. In open thoracotomy, handheld malleable retrac-tors may collapse the lung sufficiently. Nevertheless, weare increasingly performing anterior operations on thethoracic spine through video-assisted thoracoscopicspinal surgery (VATSS). The exposure is minimal, requir-ing three or four 15- to 20-mm portals to perform a cor-pectomy. The success of this procedure depends largelyon adequate lung deflation. This is obtained either byuse of a double-lumen endotracheal tube or a bronchialblocker. The double-lumen tube tends to be obstructedby mucous plugs due to its smaller diameter. The patientmay develop inadequate gas exchange during the pro-cedure, requiring reexpansion of the lung and fiberopticinspection and lavage of the lumens of the tube. Thebronchial blocker also provides adequate lung collapse,but it may require repositioning during the procedure.

Common Problems (Pre-, Intra-and Postoperative)

Vascular InjuriesThe proximity of the greater vessels obviously makes avascular injury possible. In the thoracic spine, most intra-operative problems may be caused by inappropriate

handling and ligation of the segmental vessels. Carefuldissection and respect for anatomic landmarks is the bestway to prevent damage to these vessels.

Spinal Cord InjuryAlthough it is very uncommon, spinal cord injury is amongthe most devastating complications of spinal surgery. In alarge single-center case series, including adult and pedi-atric deformity cases, a 0.37 percent incidence of majorneurologic complications was reported. All these patientsunderwent combined anterior and posterior exposure,they all had ligation of segmental vessels, and they were allsubject to intraoperative controlled hypotension.

Although most surgeons now prefer to use spinalcord monitoring, some surgeons have described false-negative results. The mechanisms of injury are multifacto-rial and include those related to the anatomic configurationof the spinal canal, the placement of spinal instrumenta-tion, and adequate perfusion of the spinal cord. The firstof these mechanisms is most commonly associated withthe correction of deformity and realignment of the spinalcanal, while the second may have to do with the spaceoccupied by instrumentation, including laminar hooks ormisplaced pedicle screws.

Spinal cord injury may also occur in the immediatepostoperative period because of the development of anexpanding epidural hematoma. This problem must beaddressed immediately and includes surgical evacuationof the hematoma and management of coagulopathies.Patients who have received multiple transfusions and suf-fer from dilutional decrease in coagulation factors maybenefit from transfusion of fresh frozen plasma andplatelets. In spite of all immediate efforts, damage may bepermanent.

DURAL LACERATION

This complication may occur as a result of trauma or sec-ondary to aggressive decompression of the thecal sac. Inparticular, patients with OPLL may have an ossified dura,which may leave a dural defect at the time of removal. Inthe chest, this creates a particular problem due to the neg-ative intrathoracic pressure. A dural-pleural fistula createsa strong gradient for the leakage of spinal fluid. This gra-dient may force the spinal cord into the defect and mayeven produce a herniation of the cord. The patient willthen develop further signs and symptoms of myelopathy.The consequences of spinal fluid leakage are discussed inthe section on the lumbar spine, below.

PULMONARY COMPLICATIONS

Atelectasis is very common, but aggressive respiratorytherapy in the early postoperative period is effective inpreventing it. If this is not aggressively done, atelectasismay lead to pneumonia. Other complications includehemothorax, pneumothorax, and chylothorax.



Diaphragmatic rupture and the formation of a herniaare extremely rare complications and may be avoided byproper reconstruction of the divided diaphragm.

� THE LUMBAR SPINE

Indications and Special AnatomicConsiderations

In contrast to the rigid thoracic spine, the lumbar spinemakes motion of the trunk possible while also providingstructural support to approximately 60 percent of thebody weight as well as protection to the neural struc-tures. The conus medullaris lies somewhere between theT12–L1 and the L1–L2 disk spaces. The cauda equinafloats within the spinal fluid contained by a thecal sac.

The vast majority of degenerative conditions—including disk herniation, spondylosis, and osteoarthritis—occur in the last two or three disk spaces.

Patient Profile

An increasing number of elderly people seek surgicalcare for symptoms of spinal stenosis. This is explainedby increase in life expectancy and increased functionaldemands. Advanced age is accompanied not only bycomorbid conditions but also by a decreased physiologicreserve. Attention to detail is important for patient safetyand early recovery. Fluid volume management, oxygentransport, perfusion, and metabolic control constitutethe most important elements. Continuous evaluation ofhemoglobin, gas exchange, and lactic acid are recom-mended during prolonged surgery.


Multiple comorbidities are frequently seen in elderlypatients who undergo lumbar decompression with orwithout fusion. Diabetes, high blood pressure, coronaryartery disease, and chronic obstructive pulmonary dis-ease (COPD) are common in this age group.


Posterior Approach to the Lumbar Spine The posterior approach requires prone positioning.Patients who do not need fusion, such as microdiscec-tomy or laminectomy for decompression of a stenoticspine, may be positioned in the semigenupectoral(“90/90,” or knee-chest) position with the use of anAndrews frame or with the double bend of a Maquettable. The patient’s back should be parallel to the floor;knees and hips are flexed slightly past 90 degrees. Manysurgeons prefer the prone position on a flat table with aWilson frame. Care must be taken to avoid compression

of the abdomen. Decompression of the abdomen andinferior vena cava helps to reduce epidural blood flow,allowing better visualization (see “Blood Loss and theQuality of the Surgical Field,” above). Additionally, if thespine remains in lordosis, the interlaminar space isclosed down and an unnecessary amount of laminec-tomy will be required to expose the disk.

For lumbar fusion procedures, the most importantfunction of positioning is to preserve the sagittal con-tours of the lumbosacral spine. A radiolucent fourposterframe or similar device is recommended, and paddingshould be added to maintain the hips fully extended.This position preserves normal lordosis, thus avoidingflat-back deformity. The superior posters should be posi-tioned under the patient’s rib cage and the inferior onesunder the anterior iliac spine.

The arms are positioned with 90 degrees of flexionat the elbows and less than 90 degrees of abduction atthe shoulders. The arms rest on well-padded arm boardsand care is taken to avoid pressure on the ulnar groovesand wrists. Care is also taken at the superior posts, whichmust not exert pressure on the axillae. In women, pressureon the breasts must be minimized. In heavier patients, weprefer a five- or six-post configuration instead of four toallow better distribution of the weight. The male genitalsshould also be free of pressure. (See “Prone positioningchecklist” on page 164.)

Anterolateral Retroperitoneal Exposureof the Lumbar Spine These approaches require lateral positioning. The posi-tioning is similar to that required for the anterior expo-sure of the thoracic spine and is adequate for anterolat-eral retroperitoneal exposure of the lumbar spine as wellas for transpleural retroperitoneal (thoracoabdominal)exposure of the thoracolumbar junction. The patient isplaced in a lateral decubitus position with the side to beoperated on facing up. Since left-sided exposures aremore frequent, the following description considers thepatient to be lying on his or her right side.

The patient is transferred from the preanesthesiacart to the operating table in a supine position and thenturned 90 degrees. An axillary roll is placed to preventcirculatory obstruction to the right arm. Our preferenceis for silicone padding. Foam padding is also placedunderneath the right leg from the hip down to the foot.Pressure on the peroneal nerve on the right side must beavoided. The head is supported with pillows or foam,taking care to maintain the alignment of the neck. Thechest cage is supported on the sternum and the back bypads and adhesive tape or by a beanbag. The pelvis issupported by adhesive tape over the greater trochanter,which is always protected by foam padding. In proce-dures involving decompression of the spinal canal orinstrumentation of the spine, stable positioning is essential



for surgical orientation and intraoperative imaging.Finally, the right arm is supported by a foam-padded armboard with the shoulder at 90 degree extension and theleft is extended on top of this, separated by pillows orother soft padding. Some surgeons prefer to break thetable at the patient’s waist in order to increase the spacebetween the inferior rib border and the ilium. This is par-ticularly beneficial for the lower lumbar spine.

Anterior Trans- or Retroperitoneal Exposureof the Lumbar SpineThe exposure to the two or three lower lumbar segmentsrequires supine positioning with hyperextension of thelumbosacral junction. This is obtained by placing foampadding underneath the lumbar region. The table is thentilted into the Trendelenburg position. This helps to dis-place the abdominal contents cephalad, facilitating theexposure. Owing to the necessary mobilization of theiliac vessels, some authors recommend pulse oximetersin both the upper and lower extremities.


Lumbar MicrodiskectomyThe level of the disk to be removed is confirmed withfluoroscopy. A 1-in. midline skin incision is then made(Fig. 14-11). After dissection of the skin and subcutaneoustissues, the dorsal lumbar fascia and paraspinal muscula-ture are dissected in a subperiosteal manner from the tip ofthe spinous process all the way lateral to the correspon-ding facet joint. A Taylor retractor is placed lateral to thisjoint, and the ligamentum flavum is released with a small

angled curette from the inferior and superior borders of theadjacent laminae as well as from the medial edge of thesuperior facet. A Kerrison rongeur is used to remove sev-eral millimeters of the cephalad lamina and 2 to 3 mm ofthe medial border of the inferior facet. The ligamentumflavum is then removed in a piecemeal manner. Themedial border of the superior facet is visualized andremoved with a Kerrison rongeur. A nerve root retractor isused to displace the dural sac and the emerging nerve roottoward the midline of the spinal canal. Epidural veins areusually encountered, and these are coagulated with abipolar cautery. This allows optimal visualization of thedisk and the herniation. The extruded disk fragments arenow removed with a pituitary rongeur. If the extrusion issubligamentous, the posterior longitudinal ligament isincised with a knife in a horizontal manner. Following this,the spinal canal is thoroughly explored with a 4-mmMurphy ball-tipped probe to determine whether there areany residual disk fragments or any other compressing ele-ments on the dural sac or emerging nerve root.

This procedure may be carried out under micro-scopic or loupe magnification. There are certainlyadvantages to the use of a microscope, but their consid-eration is beyond the scope of this chapter.

When the procedure is complete, 40 mg of Depo-Medrol is deposited on the interlaminar space and thewound is closed in three layers. After closure, the skin isinjected with 0.25% bupivacaine.

Lumbar DecompressionLaminectomy has become the standard procedure forsurgical decompression in lumbar spinal stenosis. Amidline skin incision is made. After dissection of thesubcutaneous tissues, the dorsal lumbar fascia andparaspinal musculature are dissected in a subperiostealmanner, from the tip of the spinous processes all theway lateral to the corresponding facet joints (or trans-verse processes if fusion is going to be done). After thor-ough hemostasis, the inferior half of the superior spin-ous process as well as the superior half of the inferiorspinous process and all intermediate spinous processesare removed with a rongeur. The laminae are thinneddown with a Leksell rongeur or a high-speed burr. AKerrison rongeur is then used to remove the remainderof the laminae and ligamentum flavum in a caudad-to-cephalad direction (Fig. 14-12A). The dural sac is nowcentrally decompressed and can be manipulated toallow access to the lateral recesses or subarticular areasof the spinal canal. A partial medial facetectomy isperformed by undercutting with a 45-degree Kerrisonrongeur all the way lateral to the medial wall of thepedicles (Fig. 14-12B ). The nerve roots are identifiedand followed into the corresponding foramina with anoverlying Kerrison rongeur removing all overlying spurs(Fig. 14-12C ). A 4-mm Murphy ball-tip probe is used


Figure 14-11. Midline posterior approach to the lumbarspine. The paravertebral muscles have been dissectedsubperiosteally.

Boezaart_CH14.qxd 4/26/06 6:44 PM 1


A B

C

Figure 14-12. Lumbar decompression. After posterior exposure of the spine, the spin-ous process is cut and a curette or small Cobb is used to dissect the ligamentum flavumfrom the undersurface of the lamina. A. A Kerrison ronguer is used to undercut the hyper-trophic facet joints and ligamentum flavum. B. The emerging nerve roots are freed of anycompressing elements all the way toward the foramina. C. Completed lumbar decom-pression.


to determine whether decompression is adequate.Closure is similar to that for microdiskectomy.

Anterior Lumbar Interbody FusionThis procedure is indicated mainly for the caudal lumbardisks, namely L5–S1, L4–L5, and/or L3–L4. The approachto this area of the lumbar spine must allow the surgeon tosee the disks facing the midline, and it requires either aretro- or transperitoneal exposure. The first choice shouldbe retroperitoneal exposure, especially in male patients.Our second choice is the transperitoneal exposure, butwe prefer it for obese patients, revision exposures, and forpatients in whom the abdominal retroperitoneum orpelvis have been exposed previously.

An infraumbilical vertical incision is extended proxi-mally to the pubis. The rectus fascia is opened longitudi-nally with the incision; the rectus abdominis muscle is thenretracted laterally, exposing the posterior rectus fascia.This is done to avoid damage to the segmental (T6–T12)innervation of the rectus. The arcuate line is identified. Thepreperitoneal space is encountered, and the peritoneum isdissected away from the posterior rectus sheath beforeincising the sheath. Great care is taken to avoid injury tothe inferior epigastric vessels. The exposure continues bydissection of the retroperitoneal space. The peritoneum ismobilized from medial to lateral by gentle digital dissec-tion. Once the psoas muscles are reached, the peritonealsac is protected with wet laparotomy sponges and retrac-tors are placed. Care must be taken with the ureter on theside of the dissection.

In the transperitoneal approach, the peritoneum isincised in line with the rectus sheath. The bowels arepacked cephalad to expose the posterior peritoneum,which is also incised in a longitudinal manner, exposingthe great vessels and the lumbar spine.

The next part of the dissection consists of mobilizingthe greater vessels to allow for the orthopaedic procedure(Fig. 14-13). The aorta and vena cava usually bifurcate atthe height of the L4–L5 intervertebral disk, but higher orlower bifurcations are not infrequent. We recommend athorough preoperative assessment of the vascular anatomywith MR angiography (MRA) as well as planning the direc-tion in which the greater vessels are to be mobilized. Theparasympathetic plexus (hypogastric) is distributed as adiffuse plexus that courses around the aorta and head dis-tal from the bifurcation in the presacral area. Great care istaken in protecting this plexus, so as to avoid the compli-cation of retrograde ejaculation. The middle sacral arteryand/or lower segmental vessels and ascending lumbarvein are ligated at the level and side of mobilization. Thepsoas muscles mark the lateral limits of the dissection. Theureters may occasionally be visible and must be retractedwith the peritoneum.

The lower lumbar disks should be directly visible atthis point. Retractor blades are then placed on a table-

mounted retractor system, including vascular retractors.Some systems anchor with pins into the vertebral bodies.The orthopaedic procedure consists of removal of theanterior annulus and anterior longitudinal ligament,complete removal of the nucleus pulposus, and prepara-tion of the endplates with curettes and osteotomes.Fusion is achieved by implanting a femoral ring allograftor cage with bone graft. This approach is also optimal fortotal disk replacement or disk arthroplasty.

Instrumented Posterior Lumbar FusionAfter a standard midline dissection of the skin and subcu-taneous tissues, the lumbar fascia is dissected in a subpe-riosteal manner with a bovie cautery and a Cobb elevator.After the skin incision, 1:500,000 epinephrine may be usedfor hemostasis. This dissection is advanced from the tip ofthe spinous process all the way lateral to the tip of thetransverse processes. Stripping the muscles subperiosteallyprevents tearing of the muscles and excessive bleeding.The superior and inferior segments are sequentiallystripped, depending on the levels to be fused. Self-retainingretractors are then placed, but prolonged pressure on the


Figure 14-13. Anterior retroperitoneal exposure ofthe L5–S1 intervertebral disk. This disk conforms to theapex of the promontorium and is distal to the bifurca-tion of the greater vessels. The middle sacral arteryand vein and hypogastric plexus are in the midline.


paravertebral musculature is avoided by freeing the pres-sure intermittently to prevent necrosis. The interveningfacet joint capsules are stripped and the cartilage isremoved with a high-speed burr and curettes. Great care istaken to avoid damage to the facet joints that will not befused. Some bleeding may occur, especially during the dis-section of the pars interarticularis, where the superior artic-ular artery may be damaged. Bipolar cautery is recom-mended to avoid injury to the exiting nerve root.

To prepare the spine for fusion, the facet joints arestripped of their capsules and articular cartilage and thetransverse processes and laminae are decorticated withthe use of a high-speed burr. The ala of the sacrum isalso decorticated if needed (Fig. 14-14).

Instrumentation consists of pedicle screws and rods.Landmarks for placing pedicle screws in the lumbarspine include the midline of the transverse process andthe lateral cortex of the pars interarticularis. A Leksellrongeur or a high-speed burr is used to decorticate theentry position. A pedicle opener or “gearshift” is thenused to perforate the pedicle, and a ball-tipped pedicleprobe is used to palpate the inner walls of the trajectoryof the screw hole. An appropriately sized tap is nextused, and finally the screw is inserted. The structures atrisk during the insertion of pedicle screws include thedural sac medially, the exiting nerve root medial andcaudal to the pedicle, and the greater vessels anteriorly.

These vessels lie anterior to the vertebral bodies aboveL3 or L4 and caudal to L4; the bifurcating common iliacarteries and veins take a more lateral position, directlyanterior to the pedicles. For the placement of sacral (S1)pedicle screws, bicortical purchase is strongly recom-mended. The internal and external iliac artery and veinlie laterally along the sacral ala, and any penetration ofthe anterior cortex must be done with extreme caution.In the anterior midline of the sacrum, the middle sacralartery may also be injured.

The bone graft is placed laterally, over the decorti-cated transverse process and along the lateral aspect ofthe lamina and decorticated pars interarticularis regionas well as the facet joint.

In longer surgical incisions, we use a medium-sizeddrain between the fascia and the skin. The wound isclosed in three layers.

TRANSFORAMINAL LUMBAR INTERBODY FUSION (TLIF)As an additional step in posterior lumbar fusion, an inter-body device or cage may also be placed. The major rea-sons for doing this are to restore sagittal contours,strengthen the load-bearing characteristics of the con-struct, and increase the chances of obtaining a success-ful fusion. The inferior articular process is removed withan osteotome and the superior articular process is thenremoved in a piecemeal manner with a Kerrisonrongeur. This allows access to the intervertebral disk.The dural sac lies medially, underneath the ligamentumflavum, and the exiting nerve root is on the superolateralaspect of the foraminotomy. Both the thecal sac andemerging nerve root are protected with retractors.Annulotomy is performed with a knife blade, and thedisk is completely removed with disk shavers, pituitaryrongeurs, and sharp curettes. The cartilage endplates areremoved as well to prepare the adjacent vertebrae forinterbody fusion. The anterior interbody space (poste-rior to the anterior annulus) is packed with bone graft;an interbody device is placed between both endplatesand filled with bone graft as well. Fluoroscopy is used toassess correct placement of the cage.

Posterior Iliac Crest Bone GraftMorcellized corticocancellous autograft may be obtainedby the same skin incision used for a lumbopelvic fixationor by a separate incision. If the spinal fusion extends intothe sacrum, the subcutaneous tissue layer is underminedand the posterior iliac crest approached through a separatefascial incision that stretches approximately 4 cm from theposterior superior iliac spine (PSIS), in an anterior direc-tion. The gluteal musculature is dissected in a subpe-riosteal manner and a Taylor retractor is placed in thedepth of the wound under direct vision. Great care is takennot to use any sharp instruments in the sciatic notch. TheTaylor retractor or a sharp Cobb may not only injure the


Figure 14-14. Preparation for pedicle screws. Thetransverse process, lamina, and facets have beendecorticated.


sciatic nerve but also lacerate the superior gluteal artery, inwhich case bleeding will be very difficult to control.Alternatively, a vertical incision may be made 4 cm lateralto the PSIS. After dissection of the skin and subcutaneoustissues, the procedure is as described above.

The graft is obtained by removing the lateral cortexof the ilium with the use of osteotomes. The cancellousbone is then obtained by exposing the cortex of the iliumwith gouges and curettes. Care is taken to avoid pene-trating the inner cortex of the ilium and potentially dam-aging the sacroiliac joint or ilioinguinal nerve (Fig. 14-15).When sufficient bone graft has been removed, surfacebleeding of the bone is controlled by bone wax andGelfoam. The aponeurosis is then closed with a runningsuture. Wound drains are usually not necessary.


Microdiskectomy is usually performed under general anes-thesia, but it may also be performed under epidural or localanesthesia. Advantages of epidural anesthesia includeshorter recovery room time, faster return of alertness,absence of postoperative nausea and vomiting, and superiorpostoperative pain management. Additionally, there can be

less intraoperative bleeding due to decreased venous pres-sure (see “Blood Loss and the Quality of the Surgical Field,”above). Disadvantages of epidural anesthesia includehypotension, difficulty in obtaining an airway in case of anadverse intraoperative emergency and the fact that thepatient may move the upper body during the procedure.The patient may also be uncomfortable during the surgery.Furthermore, the volume of the anesthetic may further com-promise severely diminished canal dimensions due to alarge disk extrusion. Epidural anesthetics may also increaseurinary retention, requiring an overnight hospital stay.Laminectomy for decompression and posterior spinal fusionrequires general anesthesia, mostly due to the length of theprocedure. For these procedures, as in thoracic spinalfusion, control of the surgical field and reduction of intraop-erative bleeding are important anesthetic considerations(see the discussion of thoracic spinal fusion, above).

Analgesia

After microdiskectomy, patients may be discharged on thesame day or after a 23-h hospitalization regimen. They aremobilized within a few hours and may require only mildenteral analgesics, since this surgery is generally notpainful. More extensive procedures, including laminec-tomy or lumbar fusion, require longer hospital stays andmore intensive pain control. It is recommended that thepatient become mobile on the day after surgery.Intrathecal morphine (0.004 mg/kg, or 0.3 mg for the aver-age patient, injected by the surgeon before closing thewound) or epidural analgesia (the catheter placed by thesurgeon prior to closure of the wound) have been shownto be very effective analgesic measures.


Most elderly patients with degenerative conditions of thelumbar spine also have one or more comorbid condi-tions that require specific management.

Prophylactic antibiotics are used for all spinal pro-cedures. Because the intervertebral disk is poorly vascu-larized, it is more vulnerable to a disk-space infection(diskitis). In general, this occurs with an incidence of1 percent for lumbar diskectomy; but this figure doublesin diabetic patients. For all implant procedures, antibi-otics are continued until all indwelling catheters havebeen removed. (See Chap. 3 for antimicrobial prophy-laxis and Chap. 4 for thromboprophylaxis.)

Physical Therapy Goalsand Requirements in thePostoperative Period

Patients who underwent microdiskectomy are encouragedto resume their activities in a short time. Ambulation andphysical therapy are initiated on the same afternoon after


Figure 14-15. Incisions for posterior lumbar expo-sure and posterior iliac crest bone harvesting. Notethe relationship with the clunial nerves and the sciaticnotch.


surgery. A corset is used, mostly for comfort, after dischargefrom the hospital. Patients are encouraged to increase theiractivities progressively but to avoid bending, stooping, orlifting heavy objects during the first 2 weeks. Return towork is within 2 weeks for occupations that are not physi-cally challenging; otherwise, patients may return to workin 4 to 6 weeks after an intensive course of physical ther-apy. Similar guidelines are observed for laminectomy.Nevertheless, this operation is indicated mostly for elderlypatients; the surgery is longer, and the resulting physiologicimpact greater. Hospital stays are therefore longer, but thismust be decided individually.

In the case of fusions, patients begin with out-of-bedactivities on the first day after surgery. Especially in theelderly, transfer to a recliner may be sufficient.Ambulation is increased slowly throughout the followingdays. Hospital goals for discharge include independenttransfers, independent gait (may include the use of awalker), and stair climbing. Occupational therapy con-sultation is provided to help patients resume daily activ-ities. If these goals are not achieved within the first 5 to7 days, we recommend transfer to a rehabilitation facilityfor 2 to 4 weeks until these goals are met. Otherwise,patients are discharged with recommendations for a pro-gressive walking program, with strict instructions againstbending, stooping, or lifting. Especially in the case ofinstrumented fusions in the osteoporotic spine, a rigidbrace is recommended for all out-of-bed activities.


Neuromuscular blockade is helpful for surgery to thelower lumbar spine, especially in obese or very muscu-lar patients; it may be very difficult to obtain adequateaccess to this area. Completely paralyzed paravertebralmusculature is easier to retract laterally and allows forbetter visualization. Nevertheless, thereafter, completerecovery of neuromuscular function in order to monitorelectromyographic (EMG) activity should be achievedfor spontaneous as well as for stimulus-evoked modali-ties. This is discussed further in the next section.

Common Problems (Pre-, Intra- andPostoperative)

Complications of Iliac Bone Graft HarvestingDonor-site problems have a reported incidence of 8 to 39percent and range from minor wound problems to severe,persistent donor-site pain, neurovascular injury, and evenloss of pelvic stability. The most common problem is thatof pain, which can be severe within the first 6 months buttends to diminish thereafter. Other complications that mayhave direct intraoperative implications include herniationthrough the ilium, lateral femoral cutaneous nerve injury

(meralgia paresthetica), and injury to the superior clunealnerves or ilioinguinal nerve.

The superior gluteal artery may be injured by dis-section with a sharp instrument or by retraction over thesciatic notch. Bleeding is extremely difficult to control,and owing to its anatomic location, repair or ligation isnot only difficult but may cause other complications,including sciatic nerve injury and injury to the ureter oriliac vessels. In our opinion, the best way to deal withthis problem includes tamponade by direct pressure andendovascular repair or selective embolization.

The stability of the sacroiliac joint may be damagedby removing excessive amounts of the inner cortex ofthe posterior ilium as well as by damage to the sacroiliacligaments. Pelvic instability and pain are the long-termconsequences of such damage. In patients with persist-ent sacroiliac joint pain after graft harvesting, there is ahigh prevalence of inner cortical disruption of the ilium.

Problems with Pedicle Screw PlacementAs previously mentioned, soft tissue structures may beharmed by misplaced pedicle screws. A review of theliterature reveals that in cadaver studies, experiencedsurgeons breech the cortex of the pedicle 5.5 to 31.3percent of the time; in clinical studies, between 28.1 and39.9 percent of pedicle screws are misplaced.Nevertheless, only 1.6 to 5 percent of clinical series pres-ent with irritation or injury to the adjacent nerve roots.Current methods to avoid this problem include pedicleprobing, visualization of axial landmarks by fluoroscopy,image-guided navigation systems, neuromonitoring withstimulus-evoked EMGs, and sensory evoked potentials.The latter have had limited success because they are notsensitive enough to detect individual nerve root dys-function. Evoked EMG has become an increasingly pop-ular technique to confirm correct pedicle screw place-ment in the lumbar and sacral spine. The intact pediclecortex insulates the adjacent nerve root from the stimu-lating current, and relatively high levels of energy arerequired to stimulate it, while the stimulation threshold islower after a cortical breach in the pedicle. Electrodesare placed in muscle groups whose nerve roots are atrisk from misplaced screws. Because EMG monitoring isstrongly influenced by paralysis from pharmacologicagents and chronic nerve compression, neuromuscularblockade is reversed after exposure is completed.

Vascular InjuryA serious complication of anterior spinal surgery is lac-eration of the greater vessels, with significant blood loss.These injuries occur very rarely, but they do have disas-trous consequences. The reported mortality of operativeinjury to a major vessel has ranged up to 50 percent. Ifthe patient survives, blood supply to the spinal cord mayalso be affected. Although the incidence of these injuries



is extremely low, it could be underestimated, becausethe clinical manifestations may be extremely variable.Sometimes the effects are readily apparent early on, butthey may also manifest in the long term, as is the case ofarteriovenous fistulas or pseudoaneurysm in the retroperi-toneal space.

During anterior exposure of the lower lumbarspine, direct pressure on the iliac artery may promotearterial occlusion, especially in patients with risk factorsfor thrombosis (obesity, smoking, hypotensive anesthe-sia, prolonged retraction time, and history of thrombosis).Great care is taken with patients who have demonstratedatheromatous plaques.

Deep Venous Thrombosis andPulmonary EmbolismThe incidence of deep venous thrombosis as revealed byultrasound has been reported in 0.6 to 2 percent and byvenographic studies in 10.8 to 17.7 percent of patientssubjected to spinal surgery (see Chap. 4). The occur-rence is higher for lumbar spinal surgery (26.5 percent)than for cervical spinal surgery (5.6 percent), and theprevalence of proximal deep venous thrombosis is 0.9percent. Fatal pulmonary embolisms have been describedin many case reports, but the exact incidence is not yetclear. Risks factors include lengthy procedures, pronepositioning, prolonged recumbence after surgery, andmotor paralysis of the lower extremities, as is the case forpatients with spinal cord injuries. One particular reasonthat may explain a higher incidence in lumbar surgerymay be the use of Hall-Reston type frames with directpressure on the inguinal region, thus increasing venousstasis in the lower legs. The same holds true for pro-longed retraction of the iliac vessels during anteriorexposure to the lower lumbar spine.

Several methods to prevent these complicationshave been attempted; nevertheless, there is no clear con-sensus on the optimal regimen. Both pharmacologic andmechanical methods have been shown to reduce thisrisk. Pharmacologic prophylaxis is not a well-acceptedmethod for reducing this risk, because it may increasethe risk of formation of an epidural hematoma withpotentially catastrophic neurologic damage. For this rea-son, most surgeons prefer mechanical prophylaxis.Venographic studies show that most of the thrombi are inthe calves, and they may occur proximally only occa-sionally. The effects of mechanical methods to preventthrombosis have not been clearly demonstrated in spinalsurgery (see Chap. 4).

Dural LacerationsIn spite of meticulous surgical technique, dural lacera-tions sometimes cannot be prevented during lumbarspinal surgery, particularly in cases of spinal stenosis andprevious laminectomies. The reported incidence is 4.6

percent in patients subjected to laminectomy for lumbarstenosis, 9.8 percent if the surgery is revision, and 1.8percent in disk surgery. Some authors have reportedeven higher numbers for patients with lumbar stenosis,possibly as a consequence of an atrophic dura. It is note-worthy that accidental durotomy constitutes the secondmost frequent cause for malpractice claims in lumbarspinal surgery.

The manifestations of intracranial hypotension maybe quite dramatic, with cranial nerve dysfunction, tonsillarherniation, cerebellar hemorrhage, brainstem compres-sion, and respiratory arrest. More commonly, patients pres-ent with orthostatically induced headaches, vertigo, or asubarachnoid-cutaneous fistula. This may potentiallycause and signal meningitis. Repair is warranted. The eti-ology of cerebellar hemorrhage has been ascribed toreduced intracranial CSF pressure, which increases the dif-ference between intravascular pressure and CSF pressure.Alternatively, extensive CSF loss causes downward dis-placement of the cerebellum and stretching of the superiorvermian veins. Other nontraumatic risk factors includehypertension, coagulation disorders including anticoagu-lant therapy, and vascular malformations.

When dural laceration is diagnosed, it must berepaired. The exposed nerve roots are protected with acottonoid, the laminectomy is made adequate, and thedura is sutured with running monofilament, nonab-sorbable 5–0 suture. Care is taken to avoid catching thenerve roots into the suture. The repair is then tested forleakage by applying a Valsalva maneuver. Fibrin glue isused to cover the repair at the end of the procedure. Thepatient is left in flat bed rest for the subsequent days, whichlowers the intrathecal pressure and thus promotes healingof the dura.

If CSF drainage continues after surgery, Trendelenburgpositioning or a blood patch may be attempted. The place-ment of an intrathecal lumbar drain may also facilitate heal-ing. Prophylactic antibiotics are used, and the height of thedrain receptacle is adjusted to obtain 50 to 100 mL of CSF per8-h shift over 4 days. Alternatively, the patient may bereturned to the operating room for repair.

� APPENDIX

Common Surgical Procedures

Fusion: Surgical arthrodesis allowing permanentimmobilization of a joint by inducing bone growthacross the joint space. For example, in the subax-ial cervical spine, two adjacent vertebral bodieshave five joints, allowing for motion betweenthem. This includes the intervertebral disk, thefacet joints (one on each side) and the uncovertebralprocesses. In an anterior procedure, an interbody



structural load-bearing bone graft is placedbetween the vertebral endplates to allow bonegrowth between the vertebral bodies. In a poste-rior procedure, the facet joint surfaces are partiallydestroyed, and the lateral masses are bridgedtogether by morcellized cancellous bone graft.

Anterior cervical decompression and fusion (ACDF):Anterior approach to the cervical spine, removal ofthe intervertebral disk and interbody fusion.

Corpectomy: Surgical excision of the vertebral body,including the two adjacent intervertebral disks.This procedure is intended for decompression ofthe spinal canal and for reconstructive purposes.The spine is then reconstructed with a structuralbone graft and plate instrumentation.

Anterior instrumentation: Placement of anteriorplate to increase stability and to promote fusion.

Laminectomy: Removal of the laminae and spinousprocess to increase the AP dimensions of the spinalcanal, thus relieving pressure on the thecal sac.

Laminoplasty: This procedure is intended toincrease the AP diameter of the spinal canal whilepreserving the posterior tension band, thusavoiding iatrogenic deformity (kyphosis). Thereare several different techniques, but the posteriorarch is interrupted on one side of the spine andhinged on the opposite side, producing an open-door effect. As the laminae are splayed, the cordmigrates posteriorly and the pressure is reduced.

Posterior cervical lateral-mass instrumentation:Screws are positioned in the articular processesand are subsequently interconnected by plates orrods.

Posterior wire fixation: Multiple techniques includethe passage of wires or titanium cables throughthe spinous processes or facets so as to reproducestability on motion segments that have becomeunstable.

Craniocervical fusion: Surgical arthrodesis betweenthe occiput and the cervical spine. This is achievedby inserting a structural bone graft, which spansthe base of the occiput, posterior to the opisthion,and down to the posterior arch of C1 and C2.Several techniques have been described, but prob-ably the most widely used includes occipital platesanchored with screws connected through rods tothe lateral processes of the subaxial cervical spineand the pars interarticularis of C2.

Transarticular C1–C2 screws: Screws are drivenfrom the inferior articular process of the axisthrough the C1–C2 joint into the lateral mass ofthe atlas, as described by Magerl. This allows forC1–C2 fusion procedures.

Gallie or Brooks wiring technique: These tech-niques for C1–C2 arthrodesis consist of sublami-

nar wires that are passed anterior to the posteriorarch of C1 and C2 (Brooks) and then over a struc-tural bicortical graft that is used to provide fusion.This requires both posterior arches to be intact.

Dens screws: Anterior exposure is required at theheight of the C4 vertebral body so as to obtain ade-quate angulation for the insertion of screwsthrough the anteroinferior corner of the body of theaxis and into the dens. This procedure is indicatedfor dens fractures with a risk factor for nonunion.

Transoral decompression: This approach allows forremoval of ventrally situated bony abnormalitiescausing cervicomedullary compression from thebase of the clivus to the body of the axis. Theapproach is through the soft palate and posteriorwall of the pharynx. After excision of the anteriorarch of the atlas, the dens is fully viewed and maybe completely removed.

Anterior release: The thoracic or thoracolumbarspine is approached anteriorly to removing theintervertebral disks. This allows for increasedflexibility of the spine and provides enhanceddeformity correction. The endplates are curettedfree of cartilage and bone graft is packed inbetween in order to obtain interbody fusion.

Posterior Thoracospinal fusion: A fusion is a surgi-cal arthrodesis that allows permanent immobi-lization of a joint by inducing bone healing acrossthe joint space. Through a posterior approach tothe thoracic or thoracolumbar spine, the trans-verse processes are decorticated and a morcel-lized bone graft is laid in the inter-transverse-process area to allow bone to bridge between thevertebral segments. This may be combined withposterior instrumentation, including hook, screw,and rod constructs.

Thoracolumbar corpectomy: Complete or subtotalremoval of a vertebral body in the thoracic spine,including the two adjacent disks, with the pur-pose of decompressing the spinal cord and/orreconstructing the anterior column. The void isfilled with a structural bone graft or a cage devicepacked with morcellized bone.

Anterior instrumentation: Placement of anteriorplate or rod-screw construct to obtain increasedstability and promote fusion. In scoliosis surgery,anterior instrumentation may be used to correctthe curvature, avoiding a posterior procedureafter anterior release.

VATSS (video-assisted thoracoscopic spinal surgery):Endoscopic or mini-open thoracotomy allowsaccess to the anterior thoracic spine for moststandard procedures, including anterior release,corpectomy, spinal cord decompression, andanterior instrumentation.



Costotransversectomy: A posterior extrapleuralapproach to the anterior and middle column ofthe spine, including the vertebral body and ipsi-lateral pedicle. This allows for adequate decom-pression of the spinal canal. It also allows for par-tial reconstruction of the anterior column.

Microdiskectomy: The spinal canal is approachedthrough the interlaminar space, with a very smalllaminotomy (hemi-, semilaminectomy), with thepurpose of removing an extruded disk fragment.

Lumbar decompression: This procedure is intendedfor the treatment of lumbar spinal stenosis. Thespinal canal is approached through wide laminec-tomies, with the purpose of removing osteophytes,and other hypertrophic structures that producepressure over the thecal sac.

Posterior lumbar fusion: Surgical arthrodesis isobtained by decorticating the intervening facet jointas well as the transverse processes. Morcellizedbone is placed in the intertransverse process area,providing a scaffold for vascular ingrowth and boneformation.

Anterior lumbar interbody fusion (ALIF): Surgicalarthrodesis is obtained by placing a structuralgraft or device between the vertebral bodiesthrough an anterior exposure. The endplates areprepared by curetting them free of cartilage. If acage is used, it is filled with bone graft to allowfor the formation of a bone bridge.

Posterior lumbar interbody fusion (PLIF) and trans-foraminal lumbar interbody fusion (TLIF):Surgical arthrodesis is obtained by placing a struc-tural graft or device between the vertebral bodiesthrough a posterior exposure. If the approach tothe disk includes a laminectomy and displacementof the thecal sac, this is defined as a PLIF. If theapproach is through a foraminotomy, this isdefined as a TLIF.

Circumferential spinal fusion (“360-degreefusion”): Surgical arthrodesis including both pos-terior intertransverse process fusion and anteriorlumbar interbody fusion.

“270” fusion: An anterior lumbar fusion is comple-mented by the implantation of posterior instru-mentation without posterior arthrodesis. This hasbecome increasingly popular with the advent ofpercutaneous posterior spinal instrumentation.

SUGGESTED FURTHER READING

Apel DM, Marrero G, King J, et al. Avoiding paraplegia duringanterior spinal surgery: The role of somatosensory evokedpotential monitoring with temporary occlusion of segmen-tal spinal arteries. Spine 16(Suppl 8):S365–S370, 1991.

Bazaz R, Lee MJ, Yoo JU. Incidence of dysphagia after anteriorcervical spine surgery: A prospective study. Spine27(22):2453–2458, 2002.

Bohlman H, Emery S, Goodfellow D, Jones P. Robinson ante-rior cervical diskectomy and arthrodesis for cervical radicu-lopathy: A long-term follow-up of one hundred andtwenty-two patients. J Bone Joint Surg 75(A):1298, 1993.

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