Gravity-induced XXXX in adolescent idiopathic scoliosis.

@entity1 @entity168 @entity1635 @entity2112 @entity2720 @entity85
BACKGROUND: Adolescent @entity2112 is the most common type of @entity85 , and whilst the isk of progression appears to be biomechanically mediated (larger deformities are more likely to progress), the detailed biomechanical mechanisms driving progression are not well understood. Gravitational forces in the upright position are the primary sustained loads experienced by the spine. In @entity1635 they are asymmetrical, generating moments about the @entity2720 which may promote asymmetrical growth and @entity85 . Using 3D imaging modalities to estimate segmental torso masses allows the gravitational loading on the scoliotic spine to be determined. The resulting distribution of joint moments aids understanding of the mechanics of @entity1635 progression. METHODS: Existing low-dose CT scans were used to estimate torso segment masses and joint moments for 20 female @entity1635 @entity1 . Intervertebral joint moments at each vertebral level were found by summing the moments of each of the torso segment masses above the required joint. RESULTS: The @entity1 ' mean age was 15.3  years ( @entity168 2.3; range 11.9-22.3  years); mean thoracic major Cobb angle 52(  ) ( @entity168 5.9(  ); range 42-63(  )) and mean weight 57.5  kg ( @entity168 11.5  kg; range 41-84.7  kg). Joint moments of up to 7  Nm were estimated at the apical level. No significant correlation was found between the @entity1 ' major Cobb angles and apical joint moments. CONCLUSIONS: @entity1 with larger Cobb angles do not necessarily have higher joint moments, and curve shape is an important determinant of joint moment distribution. These findings may help to explain the variations in progression between individual @entity1 . This study suggests that substantial corrective forces are required of either internal instrumentation or orthoses to effectively counter the gravity-induced moments acting to deform the @entity2720 of @entity2112 @entity1 .
