Adolescent Idiopathic Scoliosis (AIS)
- 3-D deformity of the trunk defined as radiographic lateral curvature of the spine with a Cobb angle of 10degrees or greater with rotation; presents between 10-17 yrs
- Etioloty unknown; may be related to hormonal, brain-stem, proprioception, melatonin
- Cobb angle that exceeds 10°,
- genetic factors demonstrated. Monozygotic twins=70%, Dizygotic twins=40%
- melatonin deficiency in chickens causes scoliosis, not demonstrated in humans yet.
- 1.9%-3% of adolescents
- M:F ratios = curve 11-20=1:1.4: curve >20=1:5.4, curve>30=1:10
- Increased incidence in rhymic gymnasts.
AIS Clinical Evaluation
- important questions=FH, menarchy, Pain, PMH, growth spurt
- complete neuro exam
- evalute for pelvic obliquity, limb length inequality, trunk shift, waist/shoulder asymmetry,
- Adams forward bending test demonstrates trunk rotation, note thoracic and/or lumbar prominence
- inclinometer >7 indicated need for further evaluation
- Neuro exam: includes abdominal reflexes(umbilicus deviates towards stimulus in all quadrants, deep tendon reflexes, evan for clonus, Babinski. Any adnormality indicates neurologic abnormality, MRI indicated to eval for intrapsinal tumor, syringomyelia etc. (Ginsgurg GM, JBJS 1995;77A:46).
- Evaluate for Marfan's Syndrome
- Pain: AIS is painless. Patients with complaints of pain should be evaluated for other causes of scoliosis such as neoplasm, infection, tethered cord, syrinx, herniated disc.
- PA standing xray of spine, pelvis, rib cage. Lateral xray; PA and Lat thoracic-lumbar spine include pelvic brim and top of hips
- Right and left spine side-bending films evaluate curve flexibility before surgery. Fulcrum bending and push-prone xray more accurate to predict correction and select fusion levels
- Cobb angle (intraobserver variability=5-10 degrees)=top of last involved vertebrae to bottom of last involved vertebrae, Morris=6 degree variation in Cobb angle if end vertebrae are chosen for you, 7 degree in you choose
- lumbar lordosis=bottom of L5 to top of L1
- thoracic kyphosis=T12-T5, normal=20-45 degrees
- MRI indicated for: spinal pain out of proportion to deformity, atypical curve pattern(left thoracic), radiographically documented rapid curve progression, abnormal PE findings(neuro deficit, resticted motion)
AIS Natural Hx
- Predictive factors for curve progression=peak height velocity, female sex, young chronologic or bone age, early Risser sign, open triradiate cartilage, premenarchal status, curve severity, and curve type(thoracic or lumbar, double curve or single curve)
- <30 degrees at skeletal maturity unlikely to progress
- >50 degrees at skeletal maturity progress at a rate of approximalely 1 degree per year
- curves >90 degrees =cardiopulmonary dysfunction, early death, decreased self image, pain.
- Magnitude of the curve at the time of peak height velocity is the most prognostic indicator of the need for sugery. >70% of curves >30° at peak height velocity require surgery (Little DG, JBJS 2000;82A:685).
- King-Moe most commonly used. Useful to determine fusion levels. Poor interobserver and intraobserver reliability
- Bracing indicated for curves 20-40 degrees in pts with significant growth remaining (Risser 0-3). <30 degrees should have documented >5 degree progression before bracing. Full-time bracing until skeletal maturity. Boston (TLSO) for curves with apex at or below T8, want at least 50% correction while in brace. Milwaukee (CTLSO) for apex above T8.
- Charleston=bending brace=indicated for lumbar or thoracolumbar curve <35 degree, Want 100% correction in brace. Bracing prevents progression, does not correct.
- Surgery indicated for skeletally immature pts who failed brace and have curves>40 degrees and for skeletally mature pts with curves >50 degrees.
AIS Surgical Treatment
- Standard=PSFI with multi-rod, hook, screws from neutral vertebra above to the stable vertebra level below
- Anterior discctomy and fusion indicated for severe rigid curves of for pts with open triradiate cartilage to avoid crankshaft phenomenon.
- autogenous bone grafting with ICBG is gold standard for posterior fusion.
- Thoracoplasty provides bone graft and increased cosmesis, but decreased pulmonary function=controversial
- somatosensory and/or motor-evoked potentials +/- Stagnara wake-up tests are standard of care.
- spinal cord of nerve root injury
- crankshaft phenomenon
- implant failure.
- Late infection >2%
AIS Follow up care
- Bracing=1 month f/u after brace available, take xrays in brace. Then every 6 months until skeletal maturity, xrays out of brace with each visit.
- PSFI=3wks, 6wks, 3months, 6months, then yearly until age 18.