Definition
Structural kyphosis of thoracic or thoracolumbar spine
- characterised by vertebral wedging & subsequent growth disturbance of vertebral end plate
X-ray Diagnostic Criteria Sorensen 1964
1. Kyphosis > 45°
2. > 5° wedging 3 or more adjacent apical vertebrae
Other features
- Schmorl nodes
- irregularity & flattening of vertebral end-plates
- narrow disc spaces
- increased AP diameter of apical vertebrae
- spondylosis in adults
Epidemiology
Prevalence 0.5 to 8%
M:F 2:1
High familial predilection
- AD with high penetrance and variable expression
Aetiology
Many theories proposed / true cause unclear
1. AVN of ring apophysis
- but Ring Apophysis doesn't contribute to vertebral growth
2. Schmorl Nodes
- protrusions of cartilage of disc through endplate into body
- ? nodes decrease enchondral ossification with growth arrest of anterior body
- but nodes present in normal patients (40-75% autopsies)
3. Mechanical Factors
- likely that kyphosis occurs first
- increases pressure on vertebral end-plates anteriorly and causes secondary body wedging
4. Osteochondritis or Epiphysitis
- but no inflammatory features or necrotic bone
5. Abnormality of Cartilage endplate identified
- Abnormal matrix
6. Tight ALL
Symptoms
Onset prior to puberty ~ 10 years old
Pain
- mechanical and usually in area of deformity
- ceases with maturity
Signs
Kyphotic Deformity
- fixed / remains with hyperextension
- worsen's on Adam's forward bending
Also
- compensatory lumbar hyperlordosis
- increased cervical kyphosis
- associated mild - moderate scoliosis common
Lateral standing X-ray
Cobb angle
- line along superior & inferior end-plates of each body
- measure angle of intersection
- often difficult to see T1 - T5
Individual vertebral wedging
- > 5o
- > 3 adjacent vertebrae
Schmorl nodes
Irregularity & flattening of vertebral end-plates
Hyperextension Lateral X-ray
Over bolster
- structural degree of deformity
- degree of correction
DDx
1. Postural kyphosis
- more flexible, disappears prone, normal x-ray, disappears with hyperextension lateral
2. Osteoporosis / crush fracture
3. Congenital kyphosis / anterior bar
4. Infection, tumour
5. Ankylosing spondylitis
6. Post laminectomy
7. Congenital / Developmental
- OI / SED / Achondroplasia / Morquio's
Natural History
Weinstein 1993 Iowa
- 67 patients average kyphosis 71°
- follow up 32 years vs age match controls
Findings
1. More intense back pain but no increased analgesia use
2. No difficulty with ADL's
3. Normal recreational activities
4. No increased numbness
5. More sedentary jobs
6. ROM
- decreased extension
- weaker extension
7. Normal self esteem
Curve <100°
- normal pulmonary function
Curve >100°
- restrictive lung disease
Management
Non Operative Management
Observe
<50°
No progression on serial Xray
No / mild pain
Exercise
No long-term correction
- useful to maintain flexibility / correct lumbar lordosis
- strengthen extensors of spine i.e. swimming, pilates
Brace
Indications
- skeletally immature
- curve < 75°
Type
- Milwaukee Brace / thoracic kyphosis
- TLSO / TL kyphosis
Timing
Brace full-time for 18/12
- then part-time until skeletal maturity
Issue
- trying to get a 15 year old boy to wear a CTLSO for 3 years
Operative Management
Indications
Adolescent
- pain +++ uncontrolled by brace
- kyphosis > 75° & progressing
- most surgeons won't operate until 90°
Adults
- pain +++ despite non-operative treatment
Principles
1. Correction of kyphosis
2. Arthrodesis of spine
Issues
Approach
Posterior Approach
- failure rate high with loss of correction & pseudarthrosis if curve large
- fusion on tension side of spine
Correction films
- crucial
- posterior instrumentation will only give you 10o correction
- if corrects only to > 50o , need to release ALL
One Stage
Curve < 75° & corrects to < 50°
- one stage posterior instrumented fusion
Two Stage
Curve > 75° & corrects to > 50°
- two stage procedure
- anterior thoracotomy / release of ALL
- discectomy & interbody fusion of 5 or 6 apical levels with ribs
- posterior instrumented fusion 2/ 52 later
Last Instrumented Vertebra LIV
Sagittal line from the posterior edge of the sacrum should intersect the LIV
- supine & standing hyperextension Xrays
- should be distal to first lordotic disc
- usually L1 if apex T6; L2 if apex T8; L3 if apex T10
Results
Coe et al Spine 2010
- retrospective review of 683 cases
- 50% posterior fusion, 40% anterior and posterior, 10% anterior only
- mean patient age 21
- 4% infection rate
- 2% acute neurological injury
- 4 spinal cord injuries (0.6%)
- 4 deaths (0.6%)