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Abstract
Adolescent idiopathic scoliosis individuals after spinal fusion (SF-AIS) often return to intense physical activity, but it is unclear how they adapt their movements to compensate for a rigid spine. The objective was, for the stop-jump task, to compare the spine kinematics and lower biomechanics of SF-AIS and controls (CON). Nine SF-AIS and 9 CON pair-matched individuals performed 5 trials of stop-jump. Vertical ground reaction force (VGRF) signals (1200 Hz) and spatial locations of 39 trunk, pelvis and lower limb markers were recorded (120 Hz). Analysis of covariance (jump height = covariate, p <.05) was used to compare the groups relative (RelAngDisp) and segmental (SegAngDisp) angular displacements of the upper (UT), middle (MT), and lower trunk (LT) and pelvis. Additional 2 x 2 (Group: [SF-AIS, CON] 2 (Limb: [dominant, non-dominant; repeated factor] mixed-model ANOVAs (p<.05) were applied for peak values of angular displacements, VGRF, and joint moments of both lower extremities for the stance phase. 95% confidence intervals of group differences also were assessed. Performance was similar between groups, as vertical jump height was not different. For kinematic and kinetic group differences, SF-AIS compared to CON displayed 3.2 6.2 greater LT-SegAngDisp in the sagittal and frontal planes, 5.1 greater MT-SegAngDisp in the sagittal plane, lower knee extension displacement; 0.06 Nm/kg greater peak internal hip rotator, 0.40 Nm/kg greater peak knee abductor, 0 .39 Nm/kg lower peak knee extensor, and 0.04 Nm/kg greater peak internal rotator ankle moments during the stance phase. For limb differences, the dominant limb demonstrated 0.02 0.06 Nm/kg greater peak hip internal rotation moment than the non-dominant limb. Greater peak VGRF of the dominant limb for SF-AIS was partly due to shifting more weight onto the dominant limb. These outcomes indicate that SF-AIS MT appeared to displace with the LT, suggesting LT and pelvis movements were used as a compensatory adaptation to move the trunk. Reliance on the low back and pelvis to extend the trunk may have clinical relevance for back care. Otherwise, physically active SF-AIS display comparable spine and lower limb mechanics to that of CON and can safely perform physical activities like stop-jump.