Spine Non Trauma

Lumbar spinal stenosis

Lumbar canal stenosis: presentation, imaging and management

23 questions 2 source pages

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Q1Describe the MRI findings in lumbar stenosis.▸

Sagittal T2 image: severe stenosis and grade 1 anterolisthesis at L3/4 and L4/5
Disc bulging and buckling of the thickened ligamentum flavum
No endplate destruction, no collapse

Q2What must be excluded and assessed in back pain with suspected stenosis?▸

Rule out infection/tumour, rule out cauda equina syndrome, rule out upper spinal involvement (brisk jerk)
Assess severity of axial symptoms and neurology
Assess instability

Q3What are the red flag signs in lumbar stenosis?▸

Extremes of age; history of trauma
History of cancer/drug abuse; constitutional symptoms
Rest pain / night pain waking the patient
Saddle anaesthesia / sphincter disturbance

Q4How do you differentiate the nature of pain and claudication?▸

Discogenic: worse with increased intradiscal pressure - flexion, sitting, heavy lifting, sneezing
Facet: pain in extension, radiating to posterior thigh and buttock; instability: forward flexion + extension catch
Inflammatory: relief with exercise, morning stiffness; pathological: persistent/night pain
Vascular claudication: exertion-related, worse walking/upslope, relieved by rest even upon standing, diminished peripheral pulses
Neurogenic claudication: exertion + posture, worse walking/downslope, relieved by sitting, not standing (flexion reduces ligament buckling)

Q5What are the treatment aims and indications for fusion?▸

Aims: pain relief (disc, instability, facet), decompression of neural elements, prevent progression
Conservative: anti-lordotic brace, flexion-based exercises
Fusion if: pain (discogenic, facet effusion, foraminal stenosis), severe deformity (degenerative scoliosis), instability (dynamic X-ray, anterolisthesis, iatrogenic >50% facet removal, extensive discectomy)
In anterolisthesis with a very narrowed disc (autostabilization) and no dynamic instability, decompression alone may suffice

Q6What is the evidence for decompression with or without fusion, and the natural history of degenerative spondylolisthesis?▸

SPORT trial: surgery better SF-36 and ODI vs non-operative up to 8 yrs
Pro-fusion: Herkowitz 1991, Kornblum 2004, Martin 2007 (revision 28% vs 17%), Ghogawala NEJM 2016 (SLIP) - stable slips – fusion group had better functional outcomes and lower revision rate
Against: Forsth NEJM 2016 - fusion group had significantly higher blood loss, surgical cost, length of stay, no difference in outcomes; authors did not distinguish between stable and unstable slips. Repoperation rate of 20% due to ASD, restenosis
Weinstein commentary 2016: decompression alone reasonable for many; fusion may prevent slip progression and reduce reoperation
Degenerative spondylolisthesis (Johnson): 70% stable, 15% improve, 15% deteriorate
Matsunaga: 30% progressive, no X-ray/clinical correlation; instability risk: translation >5mm, disc height <6.5mm, Facet angle >50 deg

Q7What else should be delineated on MRI in lumbar stenosis?▸

Neuroforamen stenosis and which side of the lateral recess/central canal is more stenotic
Facet effusion and facet orientation

Q8What are the borders of the lateral recess, midzone and intervertebral foramen?▸

Lateral recess: posterior SAP, anterior disc, medial sac, lateral pedicle
Midzone: posterior pars, anterior VB, medial canal, lateral foramen, superior pedicle
IVF: posterior SAP, anterior disc, superior/inferior pedicle

Q9How can fusion relieve back pain and why choose interbody fusion?▸

PL and interbody fusion have similar fusion rates (Levin Spine 2018 meta-analysis: PL 84% vs TLIF 94% radiological fusion; weak data for clinical improvement)
Interbody fusion: compression side gives theoretically better fusion and eliminates the disc pain generator
Better at reducing listhesis and restoration of sagittal balance
Corrects disc height (helps neuroforamen stenosis) and restores ligament tension (flagpost theory)

Q10What are the anterior and posterior approaches and operations used to relieve stenosis?▸

Anterior: less muscle dissection and infection, bigger cage, better deformity correction, indirect decompression
Posterior: avoids great vessels, allows foraminal decompression
Central stenosis (claudication): laminectomy, which can selectively increase decompression on the more stenotic side
Radiculopathy (lateral recess/neuroforamen): undercut/medial facetectomy; restore disc height to increase neuroforamen space

Q11What are the complications of fusion and of each surgical approach?▸

Fusion complications: pseudoarthrosis, cage migration/subsidence, implant failure
Posterior approach: durotomy and traction injury to the nerve root, posterior muscle pain and spasm
Anterior approach: vascular injury, sympathetic dysfunction, transpsoas injury (ureter, lumbar plexus e.g. genitofemoral nerve)

Q12What is degenerative spondylolisthesis and what do the natural history studies show?▸

Result of disc degeneration with decreased disc height, ligament buckling and microinstability
Commonest at L4/5; PE shows stepping at L4/5
76% of patients with no neuro deficits initially remained without deficits; 83% with neuro symptoms experience deterioration

Q13Describe the radiographic assessment of isthmic spondylolisthesis.▸

Lateral: L5 pars defect with spondylolisthesis; slip severity (Meyerding); L5/S1 disc status; bone morphology (trapezoidal VB, dome sacrum)
Lumbar lordosis (normal 20-45), lumbosacral kyphosis (slip angle), sacral inclination (normal >30)
AP: spina bifida occulta; inverted Napoleon's hat in spondyloptosis
Dynamic lateral: 4.5mm translation or 22deg angulation vs the adjacent motion segment
Scannogram: PI = SS + PT

Q14What are the clinical features of isthmic spondylolisthesis?▸

PE (L5/S1): stepping at L4/5, lumbar hyperlordosis, pelvic retroversion + hip flexion contracture + hamstring tightness + knee flexion contracture
Phalen-Dixon sign in severe slip
Phalen-Dixon crisis - high grade slip: sudden severe sciatic pain (L5/S1 root irritation), tight hamstrings, flat sacrum, pelvic waddling gait, cauda equina compression with ischiocrural spasm, scoliosis

Q15What is the natural history of spondylolisthesis (Fredrickson 1984)?▸

500 patients at age 6 with 45-year follow-up
M>F
No slip if unilateral; most frequent progression in the adolescent
No association between slip progression and back pain
Conclusion: benign course, with only a small percentage developing symptomatic progression

Q16What are the risk factors for progression of an isthmic slip?▸

Patient factors: female, young age at presentation, frequent back extension
Morphology: dysplastic pars, sacral dome, wedging of L5, sacral inclination <30, PI >70, large slip angle (>45)
Slip: high grade

Q17What are the treatment options for spondylolisthesis?▸

Conservative: flexion-based exercises, anti-lordotic brace, hamstring stretching, core strengthening
Surgery if: slip progression, high grade, Phalen-Dixon crisis, failed conservative treatment (back pain/radiculopathy)
Pars repair in young patients with no slip and normal disc: Buck's screw (cortical bone trajectory, directly across the fracture), Scott wire, Morscher hook screw, pedicle hook screw
Fusion +/- reduction +/- decompression
Reduction controversial: consider in high grade (>50%) + retroverted pelvis + poor sagittal balance; risk of neuro impairment ~33% (L5 stretch injury), needs neuromonitoring
Reduction advantages: restores sagittal alignment, reduces gait abnormalities, larger fusion bed placing fusion in compression rather than shear

Q18What are the causes of symptoms and the etiological classification of spondylolisthesis?▸

Wiltse and Newman: dysplastic, isthmic (lytic, elongated, pars fracture), degenerative, traumatic, pathological, post-surgical
Back pain causes: discogenic, pars defect, instability, facet degeneration (remember asymptomatic slip is common)
Radiculopathy: L5/S1 slip compresses the L5 root (foramen enlarged; root encroached by pedicles/fibrocartilage of the pars defect); L5/S1 PID gives S1 radiculopathy
Isthmic: most common at L5/S1; risk factors repetitive hyperextension (gymnasts, dancers), Eskimo populations, first-degree relative
Reduction: passive (muscle relaxant, prone, facet + discectomy, disc height restoration); active (reduction screws, neuromonitoring, fluoroscopy)

Q19What is the Spinal Deformity Study Group classification for reduction in high-grade spondylolisthesis?▸

High grade, balanced pelvis = no need for forceful attempts at reduction
High grade, retroverted pelvis but balanced spine = attempt postural (passive) reduction
High grade, retroverted pelvis and unbalanced spine = reduction/realignment mandatory (active), under neurological monitoring

Q20What are the problems of in-situ fusion for high-grade spondylolisthesis?▸

Pseudoarthrosis
Progressive slippage
Persistent lumbosacral deformity
Cauda equina syndrome

Q21What is the Gaines procedure and what is its risk?▸

Anterior L5 vertebrectomy + posterior L4 to S1 fusion
75% neurological injury

Q22What are the subgroups of isthmic spondylolisthesis?▸

Elongated pars
Fatigue fracture
Acute fracture

Q23What fusion technique is preferred in spondylolisthesis surgery?▸

Posterolateral (PL) vs interbody fusion
Circumferential fusion is preferred

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Lumbar spinal stenosis