Shoulder Kinematics
Objective: The purpose of this study was to evaluate the ability of the Weaver-Dunn reconstruction of the Acromioclavicular (AC) joint to recreate normal passive AC joint motion. Methods: Four intact hemi-torsos were used in this study to provide a complete shoulder girdle and musculature. Both shoulders of each specimen were tested. 2.0 mm k-wires were inserted into the mid-clavicle, biceps insertion of the humerus, and scapular spine. Electromagnetic motion sensors (Polhemus Inc., VT, USA) were rigidly attached to these pins and the sternum. The relative position of the sensors were recorded while the humerus was passively moved through three cycles of scapular plane abduction. This motion testing protocol was performed on the specimen in three states: intact, after AC ligament transection, conoid and trapezoid ligament transection, and following a Weaver-Dunn reconstruction. The maximum, minimum, and total range of translations of the clavicle with respect to the scapula in all planes (medial-lateral, anterior-posterior, and inferior-superior) were analyzed and compared across test states. Statistical analysis was performed using a paired Student's T-test with 0.05 being considered as significant. Results: The range of motion of the AC joint in the cut state was significantly greater than both the intact and reconstructed states in all planes, except anterior-posterior translation (Table I). The maximum and minimum points of the reconstructed state were significantly less (max 3.5 mm, and mm. 3.3 mm) than the intact state. All other maximum and minimum differences were not found to be significantly different. Conclusions: The Weaver-Dunn reconstruction was found to restore the normal range of passive motion of the AC joint, but created a more inferior location of the clavicle with respect to the medial aspect of the acromion.
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