kyphosis

definition

· abnormal posteriorly directed sagittal plane curve of spine

· Scoliosis Research Society states that normal range thoracic kyphosis is 20 to 40^o

· T1 to T12

· measured by Cobb method

· studies have shown upper limit of normal kyphosis to be 45^o

· in cervical and lumbar region, lordosis is normal and any kyphosis (>5^o) considered abnormal

classification

Scoliosis Reseach Society

Postural

Scheuermann's disease

Congenital

· defect of segmentation

· defect of formation

· mixed

Paralytic

· poliomyelitis

· anterior horn cell

· upper motor neurone

· meningomyelocoele

Post-traumatic

· acute

· chronic

Inflammatory

· tuberculosis

· other infections

· ankylosing spondylitis

Post-surgical

· post-laminectomy

· postexcision (eg. tumour)

Postradiation

Metabolic

· osteoporosis

· osteogenesis imperfecta

Developmental

· achondroplasia

· mucopolysaccharidoses

· other

Tumour

· benign

· malignant

Scheuermann's disease

definition

· structural kyphosis of thoracic or thoracolumbar spine

epidemiology

· prevalence - 0.4 to 8%

· M:F ratio 2:1 (conflicting reports)

· usually apparent clinically

· must be confirmed radiologically

· high familial predilection

· no definite mode of inheritance

aetiology

· many theories proposed

· true cause unclear

· Scheuermann

· considered it to be avascular necrosis of ring apophysis causing growth arrest and wedging of anterior portion of vertebral bodies

· subsequently shown that ring apophysis does not contribute to vertebral growth

· Schmorl

· noted herniation of disc material through vertebral end-plates

· thought this inhibited enchondral ossification at sites of perforation with resultant growth arrest of anterior vertebral body

· subsequently found that Schmorl nodes occur in people without the disease

· mechanical factors implicated

· likely that kyphosis occurs first

· results in increased pressure on vertebral end-plates anteriorly

· causes uneven growth of vertebral bodies with wedging

· has been referred to as osteochondritis or epiphysitis

· but no inflammatory features and no necrotic bone

· significant abnormality of cartilage growth plate identified

clinical features

· onset around puberty

· usually presents at age 12 to 15

Pain

· often present

· aggravated by sitting, standing, heavy physical activity

· usually subsides with cessation of growth

· may persist into adulthood if deformity severe

· due to degenerative spondylosis

· pain usually in area of deformity

· may also occur in lower lumbar area, esp. if deformity severe

Deformity

· very well circumscribed thoracic or thoracolumbar angular kyphosis

· apex usually about T7

· compensatory hyperlordosis of lumbar spine

· often there is increased cervical kyphosis with forward protrusion of head

· kyphosis is fixed and remains apparent on hyperextension of spine

· accentuated on forward bending

· associated mild to moderated scoliosis is common

· may also be

· anterior bowing of shoulder girdle

· tight pectoral muscles

· tight hamstrings

· paraparesis has been reported with severe deformity

· rare

Cardiorespiratory

· restrictive lung disease only occurs if curve > 100^o

radiology

Plain x-rays

· diagnosis made from lateral standing x-ray

· line drawn along superior and inferior end-plates of each vertebral body and measuring angle of intersection

· often difficult to see T1 to T5

· should be suspicious and perform better x-rays if kyphosis > 33^o from T5 to T12

· diagnostic criteria

· kyphosis > 45^o

· more than 5^o of wedging of at least 3 adjacent vertebrae at apex

· other features

· Schmorl nodes

· irregularity and flattening of vertebral end-plates

· increased AP diameter of apical vertebrae

· narrowing of intervertebral disc spaces

· spondylosis in adults

· can perform hyperextension lateral x-ray

· over bolster

· shows structural degree of deformity and degree of correction

· differentiates postural kyphosis

natural history

· may have benign course with no pain or deformity

· usually progressive structural kyphosis through growth period

· back pain usually disappears with skeletal maturity

· if kyphosis < 60^o, long-term problems uncommon

· if kyphosis > 60^o

· deformity may progress

· pain from spondylosis may become troublesome

treatment

Exercise

· does not provide long-term correction

· may be useful to

· maintain flexibility

· correct lumbar lordosis

· strengthen extensors of spine

· important in conjunction with orthotic treatment

Electrical stimulation

· no published studies

· inconsistent results

Brace

· can almost always be managed with brace if

· started before skeletal maturity

· curve < 75^o

· in form of Milwaukee brace

· can use TLSO with thoracolumbar kyphosis

· if deformity mild, brace worn full-time for 12 months

· if deformity kept fully corrected, brace weaned over 12 months

· if deformity more severe, brace worn full-time for 12 to 18 months and then part-time until skeletal maturity

· with closure of ring apophyses of wedged vertebrae

· correction obtained after 6-12 months of full-time bracing

· can expect correction of about 40%, with gradual loss of some of correction when brace discarded

· in Europe, serial hyperextension casts popular

Operative treatment

· rarely necessary

Indications

Adolescents

· significant symptoms AND

· deformity cannot be controlled by bracing OR

· kyphosis > 75^o

Adults

· kyphosis > 60^o AND

· persistent pain despite nonoperative treatment OR

· unacceptable cosmetic appearance

Principles

· correction of kyphosis

· arthrodesis of spine

Approach

· failure rate high with loss of correction and pseudarthrosis if curve large

· because fusion on tension side of spine

· if curve < 75^o that corrects to < 50^o, single-stage posterior fusion with instrumentation may be sufficient

· if curve > 75^o that does not correct to 50^o, two-stage procedure

· initial anterior approach through thoracotomy with release of anterior longitudinal ligament, discectomy and interbody fusion of 5 or 6 apical levels

· then posterior fusion with instrumentation 1 to 2 weeks later

· may use Harrington rods or CD instrumentation

Congenital kyphosis

· kyphosis due to congenitally anomalous vertebrae

classification

Type I

· congenital failure of formation of all or part of vertebral body with preservation of posterior element

· most common

· most likely to progress

· most likely to result in paraplegia

Type II

· congenital failure of segmentation of vertebral bodies anteriorly, producing anterior unsegmented bar

Type III

· mixed pattern

clinical features

· severe deformities may be obvious at birth

· less obvious deformities may not appear until later and may be accentuated during adolescent growth spurt

· progression occurs to end of growth and often after growth complete

· due to

· growth differential

· erosion of vertebral body from mechanical pressure

· deformity can become very severe (type I)

· paraplegia may occur (type I)

treatment

Nonoperative

· not effective

Operative

Type I

· ideal treatment is early detection and early posterior fusion

· best results if fusion by age 3

· can be done as early as age 6 months

· anterior and posterior fusion indicated in curve > 50^o

· posterior fusion often inadequate to stabilise spine if significant kyphosis present

· performed at age 5 or older

Type II

· if early, can treat with anterior osteotomy of unsegmented bar

· if late, requires posterior fusion

Other

postural kyphosis

· often confused with Scheuermann's disease

· features that differentiate it

· gradual rather than angular curve

· ability to voluntarily correct roundness in standing position

· reversal of thoracic spine to lordosis by hyperextension in prone position

· no structural vertebral changes

· no treatment necessary

post-laminectomy kyphosis

· following radical laminectomy that removes facet joints bilaterally

· almost inevitable in growing child

· indication is usually spinal cord tumour

· not uncommon in adult

· indication is usually spinal stenosis

· occurs because posterior supporting structures removed that normally resist gravity producing kyphosis

· child

· must recognise potential for deformity and closely observe child

· orthoses do not often work

· if deformity develops and progresses, fusion usually indicated

· adult

· prevention is key

· must preserve at least 1/2 of each facet joint or one whole facet per level

· if not possible, fusion indicated

post-traumatic kyphosis

· focal kyphosis may develop if there is damage to the anterior column

· accentuated when there is posterior column disruption

· osseous injuries produces mainly static lesions

· ligamentous injuries may lead to late deformity

· upper thoracic lesions are more stable than those at thoraco-lumbar junction

· indications for surgical intervention

· neurological deficit due to kyphosis

· refractory pain

· progression of deformity

· unacceptable cosmetic appearance

· curve < 60^o

· posterior instrumentation and fusion usually adequate

· curve > 60^o

· anterior approach usually necessary

· posterior column involved

· combination with posterior instrumentation and fusion usually indicated