Review Article Cervical Spine Deformity: Indications ...involves fusion of cervical verte-brae...

Review Article

Cervical Spine Deformity:Indications, Considerations, andSurgical Outcomes

Abstract

Cervical spinal deformity (CSD) in adult patients is a relativelyuncommon yet debilitating condition with diverse etiologies andclinical manifestations. Similar to thoracolumbar deformity, CSD canbe broadly divided into scoliosis and kyphosis. Severe forms of CSDcan lead to pain; neurologic deterioration, including myelopathy; andcervical spine–specific symptoms such as difficulty with horizontalgaze, dysphagia, and dyspnea. Recently, an increased interest isshown in systematically studying CSD with introduction of classifi-cation schemes and treatment algorithms. Both major and minorcomplications after surgical intervention have been analyzed andjuxtaposed to patient-reported outcomes. An ongoing effort exists tobetter understand the relationship between cervical andthoracolumbar spinal alignment, most importantly in the sagittalplane.

Cervical spinal deformity (CSD)remains a moving target in

the current spine literature. It is apotentially debilitating conditionwith numerous etiologies, such asiatrogenic, inflammatory arthropathy,spondylosis, congenital, neuromuscu-lar, traumatic, infectious, and neuro-muscular processes. Severe cervicalinstability or sagittalmalalignment canlead to pain; neurologic deterioration,including myelopathy; and cervicalspine (CS)–specific symptoms such asdifficulty with horizontal gaze, dys-phagia, and dyspnea. Recent effortshave sought to classify CSD and for-mulate treatment algorithms. In thisreview, we discuss the anatomy,pathophysiology, and common etiol-ogies of CSD. We then describe pos-sible treatments, which are as myriadas the etiologies of CSD. Finally, wediscuss the outcomes of CSD in theliterature and its relationship to thor-acolumbar deformity (TLD).

Etiology

CongenitalAtlanto-occipital fusion, osodontoideum, and basilar invagi-nation are atlas and axis anomaliesthat can lead to CSD. Klippel-Feilsyndrome, which causes most of thesubaxial cervical congenital defects,involves fusion of cervical verte-brae (Figure 1). Achondroplasia, thecommon skeletal dysplasia, can leadto posterior vertebral scalloping, shortpedicle canal stenosis, laminar thick-ening, and widening of intervertebraldisks. Down syndrome is linked toligamentous laxity that causes cervicalinstability seen at both the atlanto-axial joint and occiput-C1 level.

TraumaticCSD can result from instability sec-ondary to trauma. Upper CS injuries

Samuel K. Cho, MD

Scott Safir, MD

Joseph M. Lombardi, MD

Jun S. Kim, MD

From the Department of OrthopaedicSurgery (Dr. Cho and Dr. Kim), theDepartment of Vascular Surgery(Dr. Safir), Icahn School of Medicine atMount Sinai, and the Department ofOrthopaedic Surgery (Dr. Lombardi),Columbia University Medical Center,New York, NY.

Dr. Cho or an immediate familymember serves as a paid consultantto Corentec, Globus Medical,Medtronic, and Zimmer Biomet; hasreceived research or institutionalsupport from Zimmer Biomet; andserves as a board member, owner,officer, or committee member of theAmerican Academy of OrthopaedicSurgeons, the American OrthopaedicAssociation, the AOSpine NorthAmerica, the Cervical Spine ResearchSociety, the North American SpineSociety, and the Scoliosis ResearchSociety. None of the following authorsor any immediate family member hasreceived anything of value from or hasstock or stock options held in acommercial company or institutionrelated directly or indirectly to thesubject of this article: Dr. Safir,Dr. Lombardi, and Dr. Kim.

J Am Acad Orthop Surg 2019;27:e555-e567

DOI: 10.5435/JAAOS-D-17-00546

Copyright 2018 by the AmericanAcademy of Orthopaedic Surgeons.

June 15, 2019, Vol 27, No 12 e555

Copyright © the American Academy of Orthopaedic Surgeons. Unauthorized reproduction of this article is prohibited.

http://dx.doi.org/10.5435/JAAOS-D-17-00546

include occipitocervical dislocation,occipital condyle fractures, atlas frac-tures, atlanto-axial rotatory instability(AAI), atlanto-dens instability, andodontoid fractures. Subaxial injuriesinclude traumatic spondylolisthesisof axis (Hangman’s fracture), flexioninjuries, vertical compression in-juries, and subaxial extension in-juries. Posttraumatic CSD developsin most patients because of thetrauma itself, but interestingly,a minority of patients in whom a

posttraumatic CSD develops do sobecause of nonunion, implant fail-ure, Charcot joint, or technicalerror after surgery for the injury.1

Injuries involving the posteriorligamentous structures, such asadvanced-staged burst flexion-compression or flexion-distractioninjuries, are prone to deformityoverall (Figure 2), whereas lateralcompression or burst injuries canresult in posttraumatic coronal orscoliotic deformities.1

Spondylosis andDegenerative Disk DiseaseDisk degeneration leads to increasedmechanical stress at the cartilaginousend plates at the vertebral body (VB)lip. Generally, spondylosis beginswith intervertebral disk desiccation,leading to bulging of the anulus fi-brosus, loss of height anteriorly, and apositive feedback loop of increasedanterior weight bearing leading tocervical kyphosis (CK)2 (Figure 3).

Figure 1

A, Preoperative AP and lateral radiographs of the cervical spine demonstrating kyphoscoliosis in an adult patient withKlippel-Feil syndrome. B, MRI of the cervical spine showing stenosis. C, Postoperative AP and lateral radiographs of thecervical spine after C2-T3 circumferential reconstruction.

Cervical Spine Deformity

e556 Journal of the American Academy of Orthopaedic Surgeons


Spondylosis is also associated withossification of the posterior longitu-dinal ligament, which can contributeto ventral cord compression. Thisoften leads to loss of lordosis in thesubaxial spine and can negativelyinfluence global sagittal alignment(GSA). Patients will often hyperextendthrough their high CS (occiput-C2) tocompensate for the loss of subaxialsegments. By contrast, pure scolioticdeformity is rarely from spondylosis.

InflammatoryRheumatoid arthritis (RA) is the mostcommon inflammatory disorder thatcan affect the CS. The prevalence ofCS involvement in RA ranges from25% to 80%, depending on the algo-rithm used,3 with seropositivity as amajor risk factor. The three typicalRA deformities in the CS are, in orderof decreasing frequency, AAI orsubluxation, superior migration ofthe odontoid process, and subaxialsubluxation.Seronegative spondyloarthropathies

include ankylosing spondylitis (AS),Reiter’s syndrome, psoriatic arthritis,and enteropathic arthritis. AS is themost common of the seronegativedisorders andwill affect the CS later inthe disease course. Common mani-festations in the CS are CK and AAI.Global spinal kyphosis progresses as ameans to offload painful facet joints,and autofusion in this abnormal sag-ittal alignment leads to a fixed flexiondeformity. Furthermore, susceptibilityto spinal fractures leads to frequentand missed fractures that can worsenthe existing deformity.

IatrogenicIatrogenic (postoperative) remainsthe most common cause. Typically,postoperative CK is associatedwith a previous laminectomy orlaminoplasty and demonstrates aloss of sagittal alignment, shiftingthe weight-bearing axis anteriorly(Figure 4). Surgery denervates the

posterior cervical muscles, causingatrophy, and disruption of facetjoints may lead to instability.Removal of the posterior tensionband leads to worsening compres-sive forces on the anterior VB, thusexacerbating sagittal deformity andcausing a kyphotic angulation.4

The incidence of iatrogenic CSD isdifficult to measure because of hetero-geneity of patient and case complexity.One case series demonstrated a 45%incidence in patients without any pre-operative instability.5 Contrarily,postoperative kyphosis developed in10.6% of patients undergoing lam-inoplasty for cervical spondylosis,ossification of the posterior longitu-dinal ligament, and multilevel diskherniation.6 A retrospective analysisinvestigating the incidence and out-comes of kyphotic deformity afterlaminectomy for cervical spondyloticmyelopathy determined that kyphosismay develop in 21%of these patients.7

In the pediatric population, weakermusculature, ligamentous elasticity,and greater horizontal facets have beentheorized to account for the greaterrates of postoperative kyphosis.8

Postoperative development of insta-bility because of removal of static anddynamic stabilizing soft-tissue struc-tures and facet violation is a well-known complication, and it was amajor stimulus to the use of laminec-tomy with instrumented fusion andlaminoplasty. The literature compar-ing outcomes of laminoplasty versuslaminectomy are disparate, likely sec-ondary to the heterogeneity betweensurgeon technique and patient as wellas radiographic characteristics.9,10 Itcan be agreed on, however, that theprogression of loss of lordosis tokyphosis after laminoplasty appearsto be dependent on the technique.Invariably, the preservation of muscleattachments has been shown to beessential for maintaining sagittal cer-vical alignment. The posterior cervicalapproach requires careful exposurefrom C3 to C7 while taking care todissect in the avascular plane, or theraphe, between the left and the rightparaspinal musculature. Additionally,during exposure of the lateral masses,facet capsule violation can lead toaccelerated spondylosis, axial neckpain, and loss of lordosis.

Figure 2

Chronic flexion-distraction injury leading to angular kyphotic deformity in thesubaxial cervical spine. This patient successfully underwent C2-T1circumferential spinal fusion with correction of deformity.

Samuel K. Cho, MD, et al

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InfectiousThough a small contributor to theoverall causes of CSD, spinal in-fections represent a growing area,given the use of illicit intravenousdrugs in the younger population andgenitourinary surgery and intrave-nous access devices in the elderly.Infectionsmay involve any part of thespine including the VB, intervertebraldisk, neural arch, or posterior ele-ments, but most commonly it willaffect the anterior and middle col-umns. Given its rich vascular supply,the VB are a common destinationfor dissemination of hematogenousosteomyelitis. Kyphosis is often a late

finding but can present more fre-quently ifMycobacterium tuberculosisis the etiologic agent. In addition, earlysurgery for vertebral osteomyelitis hasthe benefit of improving stability andreducing kyphotic deformity relativeto conservative management. Patientsbeing treated with chemotherapy forspinal tuberculosis have, on average,an increase of 15� in deformity, and akyphosis of .60� develops in 3% to5% of patients.11

NeoplasticThough tumors involving the spinalcord or surrounding structures inthe CS are much more likely to

cause deformity via the therapeuticapproachused tomanage them, certainentities exist which may engendermalalignment and deformity even pre-operatively.Kawabataetal12 describedtheir experience treating three patientswith severe CK associated with neu-rofibromatosis (NF) and noted that ahigh risk of spinal cord injury, coex-isting spinal cord and paraspinal tu-mors, difficulties in placing anchors indystrophic vertebrae, and difficulty inobtaining solid fusion all potentiallycomplicate the treatment of their pa-tients’ cervical disease.

Radiographic Definition

Lordosis/KyphosisIt is important to consider the influ-ence of CSD on global spinal align-ment as compensatory changes occurto maintain horizontal gaze. Unlikethe thoracolumbar spine (TLS), theCS can be divided into anterior (VBand disks) and posterior (facet joints)columns. The cervical load-bearingaxis lies posterior to the VB of C2-C7,withposterior structuresbearingabout64% of the axial load. This balanceafforded by the stability of bony andligamentous anatomy maintains thenormal cervical curvature and main-tains an upright head position13

PA and lateral radiographs shouldbe used to assess coronal and sagittalalignment. Flexion-extension viewsallow for assessment of flexibility andstability. The most common methodto evaluate cervical lordosis involvesthe use of Cobb angles. Similarly, thecervical curvature index (Ishihara) isan alternative method of assessingcervical spinal alignment numeri-cally and is highly correlatedwith theC2-C7 Cobb angle.14 Although thecervical Cobb angle is straightfor-ward and has good interrater reli-ability, measurements such as thesagittal vertical axis (SVA) havegained traction in recent years(Figure 5).

Figure 3

An adult patient with severe spondylotic kyphosis (A). He is hyperlordosing hislumbar spine to maintain horizontal gaze. C2-T4 posterior spinal fusion with C7pedicle subtraction osteotomy to correct the deformity (B).




GSA can be defined in multipleways. Numerous studies have ana-lyzed the health-related quality of lifescores in relationship to adult TLD.These concepts have been echoed inthe cervical deformity literature.Global alignment can be assessedby the C7 plumb line and the differ-ence between the C2 and C7 SVA.The normal range of the C2–C7SVA is reported to be 16.8 611.2 mm.15 Additionally, in a ret-rospective review of patients under-going cervical laminoplasty, Oshimaet al16 found that postoperativefunctional outcome scores weremarkedly lower in patients withC2-C7 SVA of .150 mm.If full-standing spinal radiographs

are unavailable, T1 sagittal angle orT1 slope is useful in predicting overallsagittal balance. The incidence of CKis likely to be twice as high if a patienthas a higherT1 slope.17 Although thehigh T1 slope demands a greaterdegree of cervical lordosis, patientsmay be unable to provide it, causingprogressive kyphosis. Cervical lor-dosis is also strongly linked with T1slope in maintaining horizontal gaze,and patients with higher T1 slopeshow more kyphotic changes af-ter cervical laminoplasty at 2-yearfollow-up.18 Lee et al18 demonstratedthat thoracic inlet alignment hadnotable correlation with craniocervicalsagittal balance, similar to the ef-fect that the pelvic incidence has onthe lumbar spine. Thoracic inletangle, along with neck tilt, affectsthe alignment of the CS in thatthe thoracic inlet angle must in-crease or decrease based on changesin T1 slope and cervical lordosisto maintain neck tilt at roughly44� to minimize muscle energyexpenditure.19

Measuring horizontal gaze is also acrucial clinical data point because itcan occur with severe kyphosis andlead to a mechanical dysfunction ofswallowing. Swallow dysfunctionarises as a consequence of collapse of

the pharyngeal space. The chin browvertebral axis (CBVA) is used to assesshorizontal gaze and is defined by theangle subtended between a line drawnfrom the patient’s chin to brow and avertical line. To obtain this distance, aphotograph must be taken with thepatient standing, with hips and kneesextended and neck neutral or fixed.Lafage et al20 reported on CBVAthresholds for disability and foundthat CBVA of ,24.8� or .117.7�correlated with an Oswestry Dis-ability Index of .40.

Ames ClassificationOnly one comprehensive CSD classifi-cation system exists, which was pro-posed by Ames et al;21 it is anadaptation of the Scoliosis ResearchSociety-Schwab classification for adultTLD. The system involves a deformitydescriptor and five modifiers.The classification system requires a

full-length standing PA and lateralspine radiographs that include the

CS and femoral heads, standing PAand lateral CS radiographs, modifiedJapanese Orthopaedic Association(mJOA) scores, and a clinical photo-graph or radiograph that includes theskull for measurement of CBVA.

ScoliosisScoliosis, though infrequent, presents adistinct challenge for the spine sur-geon. It is often found in associationwith congenital bony anomalies,Klippel-Feil syndrome, and NF type 1.Preoperative CT and MRI are bothcrucial, especially given the latter’sability to detect spinal dysraphism,which approaches a prevalence of30% in patients with congenital spinedeformity.22 Surgical approach of thisrare entity can be anterior, posterior,or combined (Figure 1). In a caseseries of 18 patients with isolatedcervical scoliosis, the Cobb angleimproved from 35.1� to 15.7�;however, a complication rate of30.8% was related to surgery.23

Figure 4

Post-laminectomy kyphosis. Patient required a long spinal fusion (C2-T1) tocorrect the deformity.


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Cervical-Thoracic-LumbarRelationshipGiven the fact that CK may representnormal alignment in some patients,often a close relationship existsbetween cervical and thoracolumbaralignment.24 Smith et al25 found that53% of adult patients with TLDhad a concomitant cervical defor-mity. Furthermore, in patients withnormal horizontal gaze, thor-acolumbar alignment and thoracickyphosis (TK) directly affect thecervical alignment.24 Patients withpoor sagittal alignment often developpainful compensatory alignmentchanges to maintain upright postureincluding knee flexion, pelvic retro-version, thoracic hypokyphosis,and cervical hyperlordosis. Dieboet al24 found that patients with SVAof .50 mm require cervical lordosisto maintain gaze.In the presence of spondylotic

degenerative changes, loss of com-pensatory mechanisms for positivesagittal alignment may occur, result-

ing in increased sagittal deformity.26

Ames et al27 analyzed spinal param-eters in an asymptomatic populationand found that pelvic incidence cor-related with lumbar lordosis, lumbarlordosis correlated with TK, and TKcorrelated with cervical lordosis. Therelationship between these parame-ters does not perfectly translate fromone spinal segment to the next. Forinstance, the increase in cervical lor-dosis in response to TK may not beenough to maintain the head over thepelvis but does allow the patient tomaintain horizontal gaze.The relationship between cervical

deformity and TLD has been analyzedbefore and after surgical treatment.In a study of 470 patients with TLD, a53%prevalence of CSD and CSDwasassociated with C7-S1 SVA, pelvic tilt,and pelvic incidence-lumbar lordosis,suggesting that CSD should be inves-tigated in patients presenting withother spine pathologies.25

After correction of the TLD, pa-tients tend to be more misaligned 2years from surgery with worse TK,

T1 slope-cervical lordosis, cervicallordosis, cSVA, C2-T3 SVA, andglobal SVA compared with patientswith TLD who were not operatedon.28 These patients additionallyhave worse Oswestry DisabilityIndex and Scoliosis Research Societyactivity at 1 and 2 years. Even aftercontrolling for magnitude of TLD,cervical alignment has a direct effecton health measures.29

Pathophysiology

Normal cervical lordosis is between10� and 20�with an average of 14.4�(as measured by C2-C7 angle). Pres-ervation of sagittal balance requiresintact anterior and posterior struc-tures. Anteriorly, the VB and inter-vertebral disks resist compression.Posteriorly, the facet joints, posteriorCS musculature, and interspinousligaments act as a tension band.When the integrity of the posterior oranterior structures is compromisedand kyphosis is present, deformity is

Figure 5

Cervical alignment, Ishihara index, and spinal sagittal alignment. C7S Beta = C7 tilt angle, c-SVA = cervical sagittalvertical axis, LS = lumbar lordosis, PI = pelvic incidence, PT = pelvic tilt, SS = sacral slope, SVA = sagittal vertical axis,TK = thoracic kyphosis. (Reproduced with permission from Endo K, Suzuki H, Sawaji Y, et al: Relationship amongcervical, thoracic, and lumbopelvic sagittal alignment in healthy adults. J Orthop Surg (Hong Kong) 2016;24[1]:92-96.)26




more than likely to progress. Ulti-mately, the spinal cord may becomedraped and tensioned over the pos-terior aspects of the VB, therebycompromising vascular supply. Inthis setting, myelopathic symptomsmay develop in patients, which canlead to stepwise and potentially irre-versible neurologic injury.

Clinical Presentation andIndications

Initial evaluation of the patientshould be tailored based on the sus-pected etiology of their deformity.PatientswithASoften exhibit chronicdeformity that is gradually and pro-gressively debilitating. Alternatively,in the setting of trauma, they can alsoexhibit acute deformity secondary tofracture, with sudden decompensa-tion in posture and evidence of neu-rologic deficit. Patients with cervicaldeformity and evidence of ankylosison imaging with sudden pain shouldbe considered to have a fracture untilproven otherwise.Examination of patients with AS

should comprise of the patient stand-inguprightwith thehips fully extendedand in the seated and supine positions.Patients with cervical deformity oftenexhibit persistent cervical flexiondespite lying flat. The rigidity of thedeformity can be often assessed by

having the patient suspend his/herhead in air when supine, the so-calledhead suspension test (Figure 6). Pa-tients can also exhibit a chin-on-chestdeformity that is characteristic of AS.Iatrogenic deformities are unique in

their presentation, and each requirestheir own corrective approach de-pending on the plane of deformity(sagittal, coronal, or both), the loca-tion of the fusion mass and instru-mentation (anterior, posterior, orboth), bone quality, soft-tissue quality,and the presence or absence of infec-tion. In addition, patients with highto mid-cervical deformity may notpresent with an obvious abnormalityon visual inspection (Figure 2). Bycontrast, those with cervicothoracicdeformity often have a kyphoticappearance with difficulty raising thehead and pain, similar to those suf-fering from flatback syndrome in theTLS (Figure 3). Revisions, especially inthe setting of complex cervical defor-mity, require the utmost attention todetail to minimize complications.

The indications for corrective sur-gery in the setting ofAS are intolerabledeformity, neurologic deficit, airwaycompromise, esophageal dysmotility,and instability associated with frac-ture. The indications for surgery in thesetting of iatrogenic deformity includeintolerable posture, neurologic deficit,and intractable pain.

Preoperative Evaluation

Patients with cervical deformitywhether AS or iatrogenic often haveother medical comorbidities thatincrease the risk of morbidity andmortality. A thorough preoperativemedical evaluation should be per-formed and the patient optimizedbefore surgery. Nutrition and smok-ing status should be assessed in everycase. Osteotomies can lead to sub-stantial blood loss, and thus, preop-erative measures should be taken tohave blood prepared.Radiographic evaluation should

include long-standing radiographs to

Figure 6

A patient whose head is completelysuspended in air because of rigidcervical kyphosis (head suspensiontest).

Figure 7

Algorithmic selection of cervical deformity based on flexibility. (Reproduced withpermission from Hann S, Chalouhi N, Madineni R, et al: An algorithmic strategyfor selecting a surgical approach in cervical deformity correction. NeurosurgFocus 2014;36[5]:E5.)31


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assess GSA and coronal alignment. Apreoperative CT provides informationon existing implants, fusion masses,and osseous landmarks for plannedinstrumentation. MRI should also bepart of the workup in the setting of anabnormal preoperative neurologicexamination, previous decompressionsurgery, or congenital anomalies.Surgical management of cervical

deformity requires meticulous pre-operative planning to determine theapproach and the degree of correc-tion needed.Digital imaging softwarecan allow surgeons to plan their os-teotomies and provide insight intothe postoperative alignment that canbe attained.30

Surgical Treatment

One of the keys to surgical successis a thorough preoperative planning.Ideally, the CS should be made per-pendicular to the clavicles in the coro-nalplane.Considerations in the sagittalplane should include flexibility andassessment of occiput-C2 motion. Weprefer to align the posterior vertebralline of C2 as close to the anterior ver-tebral line of C7 as possible. This re-sults in a balanced cervical posture,assuming the TLS is already wellaligned. In the settingofa spinewithoutmobile cervical segments, we attemptcorrection toaminimally flexed (15� to

20�) cervical alignment to allow thepatient to be able to visualize theground in front of him/her.Approaches to deformity correction

can be broadly categorized into ante-rior, posterior, and combined. Thestrategy for selecting a particularapproach is often not straightforward.Hannet al31 attempted to delineate analgorithm for surgical approachselection based on fixed versus pas-sively correctable deformities. Adetailed graphical summary of thearticle has been provided, delineatingpossible surgical approach and tech-niques for addressing various cervicaldeformities (Figure 7).

Anterior

Care should be taken to identify thevertebral arteries on preoperativeMRI and to protect them duringsurgery. For maximal mobilizationand induction of lordosis, we rec-ommend wide exposure to the lateralmargin of the uncinates bilaterally(Figure 8). If a previous fusion hadbeen present, a high-speed burr canbe used to take down the fusion atthe original disk space to the level ofthe posterior longitudinal ligament.Concomitant coronal deformity canbe corrected with asymmetric resec-tion of the fusion mass. Prophylacticforaminotomies are performed toprevent root injury with spineextension. Diverging distraction pinscan also be used so that distractionrecreates lordosis. Two pins can beused on each VB to distribute forcesif bone quality is poor. The head canbe propped up with sheets initiallyand gently pushed down on theforehead with removal of the sheetsone at the time on completion of theosteotomy to induce lordosis.32

Posterior

For posterior osteotomies, the patientis placed prone in a Jackson frame

Figure 8

Chin-on-chest kyphoscoliosis. This patient underwent C4-C7 anteriorosteotomies (with standalone cages and one screw fixation) combined with C2-T3 posterior spinal fusion with multilevel Smith-Petersen osteotomies. C2 hastwo pars screws and one intralaminar screw as proximal anchors.




withmaximumreverseTrendelenburg.The foot of the Jackson frame isplaced in the lowest rung of bottombracket, and the top of the frameis placed in the lowest rung of thetop bracket. We recommend thatthe head is placed in Gardner-Wellstongs with bivector traction. Typi-cally, 15 pounds of weight is appliedon the inline traction at the beginningof the procedure. This weight is thenplaced on the extension rope at theconclusion of the osteotomy to aid incorrection.Blood pressure should be closely

monitored by an arterial line or awell-placed blood pressure cuff. Weprefer to keep the blood pressurerelatively high (around 85mmHg) inthe setting of myelopathy to ensureadequate spinal cord perfusion. Foleycatheter placement is inserted toassess fluid balance. A warmingblanket can prevent hypothermia andthereby coagulopathy. Hemostatictechniques (eg, hemostatic agents,intraoperative blood salvage) can beused to minimize blood loss.A posterior midline incision is

made. The raphe of the paraspinalmuscles is identified and dissectedto minimize blood loss duringexposure. Previous posterior fusionswith a mobile anterior column areamenable to correction with multipleSmith-Petersen osteotomies. Weadvise prophylactic foraminotomiesto prevent nerve root entrapmentwith correction of the deformity. Atensionband construct can beused byconnecting available spinous pro-cesses with a cable. This is done tohelp maintain the extension of thespine and hold correction until rodscan be placed and tightened intoposition.The Simmons osteotomy was clas-

sically described as an openingwedgeosteotomy of the lower CS thatcompromises the anterior columnopening by hinging on the posteriorcolumn. This was inherently unsta-ble, and subsequently, pedicle sub-

traction osteotomy (PSO) at C7 wasdeveloped as a means of shorteningthe posterior column while leavingthe anterior column intact (Figure 3).We recommend that all availablepoints of fixation be used. In caseswhere the occipital-cervical junctionis mobile, we leave this joint alone. Incases where the occipital-cervicaljunction is autofused, good boneypurchase can be made in the occipitalprotuberance. It is the author’spreference to use C2 pedicle screwsover laminar screws because theyallow for collinear rod attachment.Pedicle or pars screws and laminarscrews can be used together, that is,three or four points of fixation atC2, in case of poor bone qualityresulting in poor fixation (Figure 8).The fusion should be extended

down into the thoracic spine inferiorto the level of the osteotomy. Werecommend that if any question ofbony purchase comes up, then thesurgeon supplements the posteriorfixation with anterior plate fixation atthe level of the osteotomy. The tech-nical details of a cervical PSO havebeen described in the literature.33

Recently, some surgeons have foundC8 or T1 nerve root palsy with pro-found intrinsic hand weakness afterC7 or T1 PSO and recommend thatthe three-column osteotomy be per-formed at T2 or below (Figure 9).

Complications

Complications resulting from cervi-cal deformity surgery are numerous

Figure 9

Rigid cervical kyphosis after laminectomy and fusion (A). The patient underwentC2-T4 revision fusion with T2 pedicle subtraction osteotomy to correct thedeformity while avoiding C8 or T1 radiculopathy (B).


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Table 1

Patient Outcomes Table Exploring Correction and HRQOL Measures

StudySurgical Correction

ApproachPreoperativeKyphosis

PostoperativeKyphosis Degree of Correction HRQOL Measures

Kimet al36

Group 1 (17): Anteriorcervical osteotomy w/w/out posteriorinstrumentation

Lordosis(P = 0.10)

Lordosis(P = 0.92)

Group 1: 23.1� angularcorrection, 1.4 cmtranslationalcorrection

NDI

Group 2 (21): Anteriorosteotomy andSPOs w/posteriorinstrumentation

Group 1: 18.8� Group 1:25.0� Group 2: 32.4� angularcorrection, 3.7 cmtranslationalcorrection (P = 0.15and 0.03,respectively)

Group 1: 26.3 / 25.5

Group 2: 29.3� Group 2:24.7� Group 2: 20.8 / 19.7(P = 0.56,P = 0.78, respectively)

Duet al37

43 pts CDM associatedwith kyphosis-enlargedlaminectomy w/lateralmass screw fixation

8.4% (Ishiharaindex) (P ,0.001)

19.3%(Ishiharaindex)(P , 0.001)

— VAS: 37.46 12.1 / 10.66 5.3 (P , 0.001)

— JOA: 6.2 6 1.9 / 14.9 61.4(P , 0.001)

Yehet al38

20 pts anterior fusion,EOLP, lateral mass orpedicle screwinstrumented fusion

25.0� (cervicalcurvature) (P, 0.001)

9.3� (cervicalcurvature)(P , 0.001)

— NDI: 39.96 6.1 / 22.4 63.8(P , 0.001)

— Nurick scale: 2.6 6 0.7 /0.4 6 0.9 (P = 0.001)

— VAS: 6.2 6 0.8 / 2.0 61.3(P = 0.118)

— JOA: 10.16 1.6 / 15.7 61.8(P , 0.001)

Grossoet al35

34/13/53 pts dorsal/ventral/combined

Focal 23.9�(SD 14.5�)

Focal 2.8�(SD 7.4�)

Focal 1.5� (SD 7.8�) mJOA change

Global 17.2�(SD 14.0�)

Global 24.2�(SD 11.2�)

Global 1.3� (SD 5.6�) Dorsal: 1.42

Ventral: 2.37Combined: 1.05 (P = 0.097)

Yehet al39

109 pts EOLP andadjunct short-segmentACDF

7.7� (CC) 16.1� (CC) — VAS: 5.4 / 3.9

— Nurick scale: 2.7 / 0.3— JOA: 10.9/ 15.8

Lauet al40

100 pts sequentialinterbody dilation

5.7� 6 7.3�(P , 0.001)

6.7� 6 7.3�(P = 0.001)

12.4� 6 8.0� (P ,0.001)

Nurick grade: 1.4 6 1.5/0.9 6 1.5 (P = 0.037)

Neck VAS: 6.26 2.6/ 4.46 2.0 (P = 0.02)

(continued )

ACDF = anterior cervical, diskectomy and fusion, ATO = anterior osteotomy, CC = cervical curvature, CDM = cervical degenerative myelopathy,EOLP = expansive open door laminoplasty, HRQOL = health-related quality of life, JOA = Japanese Orthopaedic Association, mJOA = modifiedJapanese Orthopaedic Association, NA = not applicable, NDI = Neck Disability Index, PSO = pedicle subtraction osteotomy, SPO = Smith-Petersenosteotomy, VAS = visual analog scale




and include implant displacement,graft dislodgement, pseudarthrosis,dysphagia, hoarseness, wound infec-tion, dural tear, pneumonia, neuro-logic deficits, airway issues, andvertebral artery injury.13 Complica-tions can be divided into categoriesbased on the operative technique.Anterior approaches are more likelyto cause vocal cord palsy, tracheal/esophageal injury, graft failure, andinfection or hematoma. The poste-rior approach is associated withhigher rates of spinal cord or nerveroot injury, hardware failure orfracture, nonunion, vertebral arteryinjury, and infection or hematoma.Finally, osteotomies are likely tocause infectious, respiratory, andcardiovascular morbidities.A review of a multicenter database

for adult patients undergoing cervical

deformity surgery found 52 earlycomplications (#30 days postop)of 78 patients, with 28.2% ofpatients having $1 minor complica-tion and 24.4% of patients having$1major complication.34 Of the threeapproaches (anterior, posterior, andcombined), some have found thecombined approach to be mostfraught with complications at a rate of40% versus 30% and 27% for ante-rior and dorsal, respectively.35

Patient Outcomes

Patients undergoing surgery forCSD can be analyzed postoperativelyby examining the effects on the mag-nitude of deformity and the functionand quality of life. Table 1 demon-strates a series of studies that explored

the effects of surgical correction ondegree of deformity and health-relatedquality of life measures.

Summary

CSD is an uncommonbut debilitatingcondition with myriad etiologies butwith iatrogenic-induced deformitybeing the most common cause. De-pending on the severity of the defor-mity, the flexibility, and the surgicalapproach, the complication rate canbe high. The relationship of CSD toTLD has been studied; sagittal imbal-ance in the lumbar spine can lead topainful compensatory changes in theCS. At this time, the subject of CSDrepresents a moving target as ourunderstanding of cervical and thor-acolumbar alignment evolves.

Table 1 (continued )

Patient Outcomes Table Exploring Correction and HRQOL Measures

StudySurgical Correction

ApproachPreoperativeKyphosis

PostoperativeKyphosis Degree of Correction HRQOL Measures

Kimet al41

Group 1 (31): Anteriorosteotomy w/w/outposteriorinstrumentation

Lordosis(P = 0.73)

Lordosis(P = 0.03)

Angular(P =0.03)

Translational(P = 0.56)

NDI: (P = 0.99)

Group 2 (4): PSO Group 1: 24.8� Group 1:25.0� Group 1:27.7�

Group 1:1.8 cm

Group 1: 26.0 / 21.5

Group 2: 4.3� Group 2:216.2�

Group 2:48.8�

Group 2:2.8 cm

Group 2: 25.2 / 20.5

Kimet al42

4 groups (61 total): Lordosis Lordosis Angular Translational NASPO 13.8� 25.6� 19.4� 3.5 cmPSO 20.3� 216.2� 44.8� 2.8 cmATO 13.9� 24.9� 22.4� 1.3 cmATO 1 SPO 30.9� 24.8� 32.5 3.6 cm

Maheshet al43

9 pts single-stageposteriordecompression anddeformity correction formultilevel cervicalmyelopathy w/kyphosis

6.33� (C2-C7Cobb angle)

2� (C2-C7Cobb angle)

— mJOA: 7.88 / 15

215.8%(IshiharaIndex)

23.6%(IshiharaIndex)

—

ACDF = anterior cervical, diskectomy and fusion, ATO = anterior osteotomy, CC = cervical curvature, CDM = cervical degenerative myelopathy,EOLP = expansive open door laminoplasty, HRQOL = health-related quality of life, JOA = Japanese Orthopaedic Association, mJOA = modifiedJapanese Orthopaedic Association, NA = not applicable, NDI = Neck Disability Index, PSO = pedicle subtraction osteotomy, SPO = Smith-Petersenosteotomy, VAS = visual analog scale


June 15, 2019, Vol 27, No 12 e565


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