Lumbar Disc Protrusions

Rodney Gordon Middlemore Hospital

Pathophysiology

Herniated Disc – especially nucleus pulposus, is not inert •  Inflammatory •  Biochemical •  Vascular •  Compressive

Inflammation - Radiculopathy

Olmaker (Spine 1995) Epidural application of autologous nucleus pulposus without pressure caused impairment of nerve function and axonal injury and cell damage

Nucleus is avascular, when exposed it is perceived as an

antigen – intense inflammation

Both associated with significant inflammation -  Increased phospholipase A2 -  Increase Cytokines -  Serotonin/5-HT

Annular Tear and nucleus herniation

Nucleus Pulpous

•  Inflammatory induced nerve root injury reverses in 2 months and may be present without nerve root compression (Otani – Spine 1997)

Patients with Disc Herniation/Sciatica

•  Increase concentration of neurofilament protein and S-100 in the CSF indicating axonal damage and Schwann cell damage

DRG - PAIN •  Severity of pain is worse the closer the disc is to the

DRG. DRG may be a crucial mediator of pain and an important processor in “chemical radiculitis”. Neuron stimulation by non compressing nucleus suggests that pathogenic factors in the nucleus may have a crucial role in the induction of hyperalgesia

•  May explain “severe pain without a visually identified protrusion” (Anzai)

Radiculopathy

•  Biochemical Process – Cytokines/PG’s etc •  Mechanical process – compression – local damage/

ischaemia •  Chronically compressed nerves acquire a tolerance to

acute compression •  Chronic double level compression does not induce more

changes than single level compression but recovery is less complete

Radiculopathy Mechanical compression is not necessary for induction of

pain involving a nerve root irritated by the nucleus pulposus. Such affects can involve adjacent or contralateral roots. This may explain why symptoms may be present from multiple levels even when the herniation is limited to one level (Olmarker – Spine 1998)

Vascular Pathophysiology •  Nerve root injury adjacent to areas of nucleus pulposus leakage

through the annular tear may have a vascular pathophysiological mechanism. This findings may explain symptomatic sciatica without radiographic or surgical evidence of disc herniation.

•  Application of nucleus pulpous to nerve root –  Increase endoneural pressure –  Decrease blood flow in the DRG –  ?? “Compartment Syndrome” in the DRG

Clinical Anatomy •  Contained

–  Central –  Posterolateral –  Foraminal –  Extraforaminal

•  Non Contained –  Extruded –  Sequestrated

•  Subligamentous – wrt the PLL •  Transligamentous - wrt the PLL

E Carrage (JBJS 2003) 1.  Fragment-fissure herniation (49%) best outcome

1% reherniation 1% reoperation

2.  Fragment-defect herniation (18%) 27% reherniation 21% reoperation

3.  Fragment contained herniation (23%) 10% reherniation 5% reoperation

4.  No fragment contained herniation (9%) 38% recurrent/persistent sciatica Standard outcome scores less improved (Signif)

Carragee

•  Degree of annular competence after discectomy •  Type of herniation

–  Both have value for the prediction of recurrence, reoperation, and clinical outcome following discectomy

Carragee - Conclusion

•  Intraop findings were more clearly associated with outcomes than were demographic, socioeconomic, or clinical variables

Ito et al– Spine 1996 Neovascularisation

•  Neovascularisation of herniated discs –  Sequestrated (common) –  Protrusions – less frequent –  Subligamentous extrusions – less frequent

•  Neovascularisation did not lead to scarring, more like absorption

•  Clinical course ≥ 30 days – more prominent absorptive process

Ito et al

•  Contained disc herniation – protrusion/subligamentous extrusion

•  Non contained disc herniation – transligamentous extrusion/sequestration

Ito et al •  Non contained disc herniation – direct contact with

epidural tissue •  Contained DH – no contact

Absorption

•  Larger disc herniation – greatest tendency to decrease in size (Saale and Maigre)

•  Unfortunately it is difficult to differentiate between the types on an MRI scan

•  Conservation Rx should not be prolonged beyond 3 months (Ito)

Ito et al Attempted Conservation Mx

Surgery offered if Cons Mx failed/cauda equina syndrome / progressive nerve deficit

Rare for surgery to be needed ≥ 2/12 after onset of

symptoms for non contained herniation (extremely rare at > 4/12)

Symptoms in patients with contained herniation last longer

and operative Tx may be necessary even 4/12 after onset of symptoms

Ito et al

•  Non contained lumbar disc herniation can be treated without surgery if these patients can tolerate the symptom for the first 2 months

Physical Examination

•  Mannequin Sign (100% reproducible, 80% specificity) –  Antalgic posture –  Relevant hip and knee flexed –  Pelvic tilt towards affected side

Treatment •  Microdiscectomy – rapidly taking hold as the gold

standard –  More cost effective –  Less postoperative pain –  Less work days lost –  Improved visualisation –  Better binocular vision through smaller incision

Microscopic •  Optics of the microscope condense the 3D line of vision

to 22 mm –  No matter how deep the wound, as long as it is

>22mm diameter, 3D will be maintained •  Interpupillary distance ~ 62 mm •  To maintain 3D vision with loupes - require a skin

incision ≥ 62 mm •  If skin incision < 62 mm = monocular vision

Surgical Indications

•  Cons Mx failed at 6 weeks •  Cauda Equina syndrome •  Increasing neuro defect •  Painless severe nerve defect •  Recurrent sciatica after a successful trial of Cons Mx •  Signif motor deficit with tension signs •  Herniation into an already stenotic canal •  Large extruded fragment •  Intractable pain

Prognosis

•  Larger A-P disc length •  Small disc width •  Large medio-lateral canal width

–  Robust correlation with good surgical outcomes

Prognosis

•  The degree of neurological deficit does not correlate with outcome

•  Patients with weakness can improve with non operative treatment

McCulloch 1.  LDH = common (1% of population) 2.  > 90% improve with non operative Mx 3.  2-4% are surgical candidate 4.  MRI will reveal LDH in 30% of asymptomatic adults less

than 60 years 5.  Surgical intervention will improve short term outcome –

with little long term difference 6.  Surgical intervention is rarely indicated before 6 weeks

from onset of symptoms but should not be delayed beyond 3-4 months

7.  Discs will continue to degenerate with Sx or conserv Mx 8.  Scar tissue will form if repeated discectomy is required

Painless Weakness

•  A dissociation between pain and sensorimotor dysfunction should not be a contraindication to providing the patient an opportunity to receive surgical relief for nerve compression if non operative measures fail.

•  But Lipetz et al conservatively treated 7 consecutive patients with painless weakness with full recovery in 100%

Red Flags •  History of signif trauma •  Cancer •  Constitutional symptoms •  Night pain •  Immunosuppression •  Recent infection •  Bladder/bowel dysfunction •  Bilat neurological deficits •  Saddle anaesthesia •  Progressive neurological deficit •  Unremitting pain