· narrowing of spinal canal
· can occur in
· central canal
· lateral recess
· intervertebral foramen
· old men
· onset usually in 50s and 60s
· M:F = 4:1
· achondroplastic
· idiopathic
· congenital narrow spinal canal
· degenerative
· spondylolisthesis
· post-traumatic
· iatrogenic
· post-laminectomy
· post-fusion
· miscellaneous
· Paget’s disease
· kyphosis
· scoliosis
· flourosis
· DISH
Central canal
· most important part is at level of disc
· posterior wall
· ligamentum flavum
· laminae
· lateral wall
· medial part of facet joints
· intervertebral foramina
· anterior wall
· annulus fibrosis
· posterior vertebral bodies
Lateral recess
· extends
· from where nerve root leaves dural sac
· to where nerve root exits foramen
· posterior wall
· ligamentum flavum
· superior part of lamina
· anterior wall
· posterior vertebral body
· annulus fibrosis
· lateral wall
· medial and inferior pedicle
Intervertebral foramen
· extends
· from inner foramen
· to outer foramen
· superior wall
· inferior part of pedicle above
· inferior wall
· superior part of pedicle below
· anterior wall
· posterior part of vertebral bodies above and below
· intervening intervertebral disc
· posterior wall
· pars interarticularis
· ligamentum flavum
· apex of superior articular facet of vertebra below
Central canal
· usually heart-shaped
· may be trefoil-shaped
· short pedicles in achondroplasia
Central canal
· extension makes canal smaller
· shortening of spinal canal
· posterior protrusion of disc
· redundancy of ligementum flavum
· most common aetiology
Discs
· primary change is in discs
· results in
· loss of height
· bulging of annulus
Facet joints
· secondary change occurs in facets
· results in
· facet subluxation
· capsular hypertrophy
· osteophyte formation
Instability
· is result of disc and facet degeneration
· causes
· rotation
· translation
· ligamentum flavum hypertrophy
Central canal
· narrowing due to
· bulging of annulus posteriorly
· facet osteophytes posterolaterally
· hypertrophied ligamentum flavum posterolaterally
· worsened by
· rotation and translation
Lateral recess
· narrowing due to
· facet subluxation, esp. anterosuperior migration of superior facet
· facet osteophytes
· hypertrophied ligamentum flavum
Intervertebral foramen
· narrowing due to
· loss of disc height with approximation of pedicles
· annular bulge inferiorly
· facet hypertrophy medially
Central canal
· AP diameter defined as
· midsagittal distance
· from posterior margin of tip of vertebral body
· to line joining tips of facets at facet joint
· average AP canal diameter is 15 mm
· narrowest at L2-L4
· widest at L5-S1
· critical diameter determined by Verbeist
· normal if > 12
· relative stenosis if 10-12
· absolute stenosis if < 10
· critical area is 100 mm2
Intervertebral foramen
· no absolute values determined
· important variables are
· height
· AP width
· shape
Mechanical
· probably unimportant
Ischaemia
· due to interference with metabolic demands of nerve root
· nerve root supplied with blood from
· spinal artery centrally
· radicular artery laterally
· drained by corresponding veins
· exercise increases nutritional requirements and waste production
· response is arteriolar and venous dilatation
· canal constriction limits response
· causes relative ischaemia
Back pain
· present for years
· tolerable
Leg pain
· two types
Type 1
· sciatic type
· may have associated neurological deficit
· L5 most common
Type 2
· neurogenic type
· insidious onset
· usually bilateral
· diffusely localised
· no dermatomal pattern
· usually in
· buttocks
· thighs
· calves
· described as
· heaviness / weakness
· burning / cramping
· tingling / numbness
· worse with walking
· relieved by rest
· sitting
· flexion
· usually does not affect voiding
· usually normal
· may be L5 radiculopathy
· important to exclude other pathology
· vascular
· hip
· abdomen
· vascular claudication
· calf pain
· rapid relief with standing
· no back pain
· no numbness
· abnormal pulses
· hip disease
· primary neurological disorders
· peripheral neuropathy
· amyotrophic lateral sclerosis
· retroperitoneal pathology
· aortic aneurysm
· tumour
· renal pathology
· performed to
1. rule out serious pathology
· infection
· tumour
2. confirm degenerative changes
· facet joint hypertrophy
· disc space narrowing
· osteophyte formation
· decreased AP diameter of canal
3. identify associated pathology
· degenerative spondylolisthesis
· degenerative scoliosis
· gold standard
· may be routine in future
· not clear
· some studies suggest that not all patients show progressive deterioration
· rest
· avoid aggravating activities
· analgesics
· simple analgesia
· short course of NSAIDs
· back support
· brace to prevent extension
· epidural caudal injection
· if operation not indicated
· calcitonin
· effective in Paget’s disease
Indications
· absolute
· cauda equina syndrome
· relative
· failure to respond to nonoperative treatment
· significant disability (pain and limited walking distance)
· progressive neurological deficit
Principles
· balance between
· neurological decompression
· spinal stability
Decompression
· central stenosis can be decompressed by
· multiple laminotomies
· multilevel laminectomy
· nerve roots should be decompressed
· in lateral recess
· in intervertebral foramen
· involves removal of
· medial aspect of facet joint out to pedicle
· pars should be preserved if possible
· may have to remove entire facet joint and pars
· disc usually not removed
· only if significant prolapse
· should preserve one facet joint at each level
· can be half on each side
Fusion
· indicated in
· degenerative spondylolisthesis
· intraoperative destabilisation (removal of > 1 facet joint or pars)
Results
· 70% improvement in 70% of patients
· will not relieve back pain
Complications
· epidural fibrosis
· vertebral subluxation