Upper extremity kinematics analysis in obstetrical brachial plexus palsy.

INTRODUCTION Several recent studies demonstrate that upper extremities kinematics analysis is in increasing use to assist clinical practice. We describe an upper limb kinematics analysis protocol that was first applied to a group of healthy children (to obtain normative data), and subsequently, to a child presenting with obstetrical brachial plexus palsy (OBPP) before and after surgical treatment. MATERIALS AND METHODS The protocol is based on two very simple tasks. Reflective markers are placed on the studied segments, and optoelectronic cameras three-dimensionally record the position of the markers during the course of movement. The data, collected by a Vicon system (Oxford Metrics Ltd., Oxford, UK), are analyzed by a dedicated software; this software provides coefficient of multiple correlation (CMC) for the comparison of different kinematics curves and motion amplitudes. A CMC above 0.95 was considered to be excellent, between 0.85 and 0.95 was good, and below 0.85 was poor. Twelve healthy children, average age 9.7 years (from 7 to 14 years), were analyzed. A 7-year-old patient presenting left OBPP was similarly analyzed, pre- and postoperatively, after a lateral rotation osteotomy of the humerus. RESULTS The analysis of the 12 healthy children established a kinematics corridor for each task and each angle considered. Analysis of the pathological patient revealed kinematics anomalies during movement which went undetected at simple clinical examination. CMC analysis after treatment showed improvement of all movements around the shoulder, going from "poor" preoperatively to "excellent" postoperatively. Amplitudes analysis similarly demonstrated postoperative improvement, which increased from 28 to 67% according to the rotations considered, around the shoulder and elbow. The interest in these results should be confirmed by studies in a larger number of patients. DISCUSSION Upper extremity kinematics analysis is increasingly utilized in current clinical practice. Although many problems occur because of the non-cyclical and non-automatic nature of movement, review of the literature and our preliminary results show that reproducibility is satisfactory. Interest in our work arises from helping develop a preoperative evaluation tool (providing a more global view of abnormalities) as well as a postoperative assessment one (for the quantification of movement gains obtained by surgery after humeral osteotomy). LEVEL OF EVIDENCE Level IV. Diagnostic retrospective study.