Motion analysis in the axial plane after realignment surgery for adolescent idiopathic scoliosis

This study aimed to define changes occurring in axial plane motion after scoliosis surgery in patients with adolescent idiopathic scoliosis (AIS) using gait analysis. Pre- and postoperative axial plane motion was compared to healthy/control subjects. This may potentially improve our understanding of how motion is impacted by deformity and subsequent surgical realignment.

15 subjects with AIS underwent pre- and postoperative radiographic and gait analysis, with focus on axial plane motion (clockwise [CW] and counterclockwise [CCW]). Age, weight, and gender-matched controls (n = 13) were identified for gait analysis. Control, preoperative and postoperative groups were compared with paired student's t-tests.

Surgical realignment resulted in significantly decreased in upper thoracic, thoracic, thoracolumbar and lumbar Cobb angles pre-to-postoperatively (36.7° vs. 15.2°, 60.1° vs. 25.6°, 47.7° vs. 17.7° and 27.2° vs. 4.8°, respectively) (all p < 0.05), with no significant change in thoracic kyphosis, lumbar lordosis, central sacral vertical line, pelvic incidence, and sagittal vertical axis. However, pelvic tilt significantly increased from 4.9° to 8.1° (p = 0.035). Using gait analysis: preoperative thoracic axial rotation differed (mean CW and CCW rotation was 1.9° and 3.1° [p = 0.01]), whereas mean CW & CCW pelvic rotation remained symmetric (2.0° and 3.0°; p = 0.44). Postoperatively, CCW thoracic rotation range of motion decreased (CW: 0.6° and CCW: 1.4°; p = 0.31). No significant difference in postoperative pelvic rotation occurred (1.1° and 3.4°; p = 0.10). Compared to controls, AIS patients demonstrated no significant difference in total CW & CCW thoracic motion relative to the pelvis both pre- (14.9° and 12.3°, respectively; p = 0.45) and postoperatively (12.9° and 12.3°, respectively; p = 0.82).

AIS patients demonstrated abnormal gait patterns in the axial plane compared to normal controls. After surgical realignment and de-rotation, marked improvement in axial plane motion was observed, highlighting how motion analysis can afford surgeons three-dimensional perspective into the patient's functional status.