Lumbar Stenosis

DefinitionLumbar Stenosis

 

Reduction of space available for neural elements in spinal canal or intervertebral foramina

- due to degenerative changes, congenital abnormalities or both

- involves compression of the thecal sac or nerve roots

 

Epidemiology

 

Onset 50 - 60's

- M = F

- associated with onset OA spine

 

L3/4 & L4/5 most common

 

Aetiological Classification

 

1. Congenital

 

Achondroplastic

- short thick pedicles and narrowed interpedicular distance

 

SED

 

Idiopathic ~ Polynesians

- trefoil-shaped canal

 

Congenital narrow spinal canal

- most syptomatic patients have canals at lower end of spectrum

 

Prematurity

- narrow L3

 

Ostepetrosis

 

2. Acquired

 

Degenerative

- most common aetiology

- disc desiccation / loss of height / bulging of annulus

- facet subluxation / capsular hypertrophy / osteophytes

- overall shortening of lumbar spine / decreased volume

- ligamentum flavum hypertrophy

 

Spondylolisthesis

 

Kyphosis

 

Iatrogenic

- post-laminectomy

- post-fusion

 

Miscellaneous

- Paget's disease

- Fluorosis

- DISH

- Ankylsing spondylitis

- Tumour

- Infection - TB

 

Traumatic / Post fracture

 

Anatomical Classification

 

1.  Central Canal Stenosis

 

2.  Lateral Recess Stenosis

 

3.  Foraminal

 

Anatomy

 

1.  Central canal

 

Posterior wall - ligamentum flavum & laminae

Lateral wall - medial facet joints & intervertebral foramina

Anterior wall - annulus fibrosis & posterior vertebral body

 

2.  Lateral recess

 

Extends from where nerve root leaves dural sac to where nerve root enters foramen

 

Posterior wall - ligamentum flavum & superior part of lamina

Anterior wall - posterior vertebral body & annulus fibrosis

Lateral wall - medial & inferior pedicle

 

3.  Intervertebral foramen

 

Extends from inner to outer foramen

 

Superior wall - inferior part of pedicle above

Inferior wall - superior part of pedicle below

Anterior wall - above is body, below is disc

Posterior wall - pars interarticularis, ligamentum flavum & apex of superior facet of vertebrae below

 

Pathology

 

Stenosis typically at disc level either due to disc or facets

 

1.  Central Canal

- bulging of annulus posterior

- facet osteophytes posterolateral

- hypertrophied ligamentum flavum posterolateral

 

Lumbar MRI Stenosis Trefoil Canal

 

2.  Lateral Recess

- facet subluxation & osteophytes + hypertrophied ligamentum flavum

 

3.  Intervertebral Foramen

- loss of disc height with approximation of pedicles

- inferior annular bulge

- medial facet hypertrophy

 

Effects

 

Mechanical

- increased canal narrowing with extension

- also get posterior disc protrusion and redundancy of ligamentum flavum

- root lacks perineurium & hence more susceptible to compression

 

Ischaemia

- interference with metabolic demands of nerve root

- exercise increased nutritional requirements & waste production

- canal constriction limits response = relative ischaemia

 

Symptoms

 

Back Pain

 

Sciatica

- L5 most common, then S1

 

Neuropathic claudication

- insidious onset

- usually bilateral

- diffuse / no dermatomal pattern

- buttocks / thighs / calves

- heaviness / weakness / burning / cramping / tingling / numbness

 

Worse with walking, standing & lumbar extension

 

Relieved by sitting, flexion, walking upstairs, squatting

 

Signs

 

Often none, but can overlap with HNP

 

DDx

 

Vascular claudication

- calf pain with exercise

- rapid relief with cessation walking

- no back pain / no numbness

- abnormal pulses

 

Hip Disease

Diabetic neuropathy

Retroperitoneal pathology

 

X-ray

 

Rule out 

- infection / tumour / fracture

 

Confirm degenerative changes

- facet hypertrophy / disc narrowing

- decreased AP diameter of canal

- identify associated pathology i.e. spondylolisthesis / scoliosis

 

MRI

 

T2 Sagittal "MRI Myelogram"

 

Lumbar MRI Stenosis Sagittal T2Lumbar Stenosis MRI SagittalLumbar Stenosis MRI

 

Stenotic Measurement

 

A.  Volume

- more accurate

- critical area is 100 mm2

 

B.  AP diameter less accurate

- normal if > 12mm

- absolute stenosis if < 10mm

 

Intervertebral foramina

- no fat about nerve root

- reduced height

 

Lumbar Foraminal Stenosis L45 MRILumbar MRI Tight Intervertebral Foramina L3

 

B.  Axial slices

 

Findings

- no fat about dura

- trefoil shape canal

- lateral recess or foramina compression

- nerve root compression

 

Lumbar MRI Stenosis Trefoil CanalLumbar stenosis axial MRILumbar MRI Axial Stenosis

 

NHx

 

Not clear not all patients progress

 

Johnsson 1993 Clin Orthop

- 32 patients followed 4 years

- 70% unchanged

- remainder: half worse, half better

 

Management

 

Non-Operative Management

 

Options

 

Rest / Avoid aggravating activities

 

Analgesics

- simple analgesia

- short course NSAIDS

 

Back support

- prevent extension

 

Physio

- back strength in flexion

- stabilise abdominal muscles

- aerobic fitness on exercise bike 

 

Epidural steroids

 

Koc et al Spine 2009

- RCT of exercise v epidural steroids v control in spinal stenosis

- exercise and epidural steroids both efficious up to 6 months

 

Calcitonin

 

Podichetty et al Spine 2004

- RCT of calcitonin v placebo

- no difference in two treatment groups

 

Operative Management

 

Indications

 

Absolute 

 

Cauda equina syndrome

 

Relative

 

Failure to respond to non operative treatment

Disabling neurogenic claudication

Progressive neurological deficit

 

Back pain is not an indication

 

Options

 

Decompression +/- fusion

 

Interspinous devices

- limit extension

 

Indications for fusion

 

1.  Degenerative Spondylolisthesis

 

2.  Radiological instability

- > 3mm or > 11o

 

3.  Intra-operative destabilisation

- removal of > 1 facet joint or pars

- i.e. radical decompression required laterally

 

4.  Degenerative scoliosis

 

5.  Significant low back pain / disc degeneration

 

Decompression

 

Define site of compression

- central / lateral recess / foramina

 

Define levels

- single / multilevel

 

Fusion

- must be prepared to fuse if cause instability

- consent

 

Results

 

Operative v Non Operative

 

Weinstein et al Spine 2010

- SPORT trial

- RCT of operative v non operative treatment lumbar stenosis

- 289 patients with 4 year follow up

- substantially improved pain and function in operative group

 

Interspinous Devices

 

Hsu et al J Neurosurg Spine 2006

- RCT of non operative v X Stop interspinous device

- significant improvement in QOL, with results similar to surgical decompression

 

Decompression v Fusion

 

Niggemeyer et al Eur Spine J 1997

- meta-analysis

- if symptoms < 8 years, decompression without fusion yields best results

- if symptoms 15 years or more, decompression with instrumented fusion best results

- decompression and fusion without instrumentation had worst results

 

Complications

 

Epidural haematoma

Instability

Infection

Nerve root injury

Dural Tears

 

Technique L4/5 Decompression

 

Position

- abdomen free to limit venous pressure and bleeding

- 4 poster / knee below hips / arms on bolster

- feet / knees / elbows / face / eyes cushioned

- SCUDS, TEDS

- betadine packs in buttocks

- +/- Jackson table (enables more lordotic position if instrumentation planned)

 

Landmarks / Check level

- iliac crest L4/5 interspinous space

- prep area aseptically, spinal needle

- check with lateral x-ray

- square drape

 

Incision

- inject LA with A

- midline

- meticulous haemostasis

- divide thoracolumbar fascia

 

Superficial Dissection

- subperiosteal elevate of supraspinous muscles (Cobb's and diathermy)

- sequentially pack with rolled swabs / sausages to control bleeding

- out to lateral extent of pars

- expose facet joints, but preserve capsule if not fusing

- beware parafacetal arteries

- don't extend between transverse processes as nerve root at risk

 

Deep dissection (L4/5)

 

L4 5 DecompressionL4 5 Decompression Laminectomy

 

Recheck level

- L4/5 interspinous gap

 

Resect L4 spinous process

- remove ligamentum flavum above and below

- Kerrison Rongeur / knife

- remove all of L4 lamina

- expose L4/5 disc space

- L5 nerve root exits inferior

- L5 nerve root will pass below L5 pedicle

 

Remove L4/5 disc fragments if needed

- nerve root retractor

- gently retract dura to each side

- take out with pituitary rongeur

 

L4/5 medial facetectomy

- above L5 pedicle

- L5 nerve root exits inferior to it

- decompress, pass Watson Chaney

 

Preserve pars & half of facet

- may have to remove entire facet joint & pars

- preserve one facet joint at each level

- can be 1/2 on each side