Study design: Posture and motion analysis after a Cotrel-Dubousset instrumentation.
Objectives: To investigate the compensation role of pelvis.
Summary of background data: Few existing studies found no compensation at the lower unfused level but did not investigate the pelvis.
Methods: Thirty patients were analyzed before surgery then at short-, medium-, and long-term postoperative follow-up. Calibrated x-rays with three-dimensional reconstruction yielded quantification of pelvic parameters. Noninvasive optoelectronic system allowed analyzing subjects first in standing position, then during flexion-extension, lateral bending, and axial rotation. Skin markers were used to quantify three-dimensional orientation of the shoulders, trunk and pelvis, and their range of motion (ROM).
Results: Ten patients among 21 had after surgery more than 5 degrees change of pelvic incidence. In flexion, global ROM decreased from preoperative to postoperative phase (P < 0.05). Global ROM variation was not correlated to that of lower unfused segment, while it was highly correlated to pelvic ROM variation (r = 0.78 at medium follow-up).
Conclusion: This study underlines the central role of pelvis in balance and motion of the patients before and after surgery.