The fulcrum axis: a new method for determining glenoid version.

Previously applied methods for the evaluation of glenoid version did not use body-surface landmarks; therefore, it is not possible to get information about glenoid version from the outside. The tip of the coracoid and the posterolateral corner of the acromion can easily be found on the body surface. These 2 landmarks were connected by a line called the fulcrum axis. After using an experimental x-ray technique in 143 human cadaver scapulae, 5 independent observers identified the fulcrum axis and the glenoid fossa twice. The resulting overall angle between the fulcrum axis and the glenoid fossa was 1.8 degrees (SD 4.5). The fulcrum axis may be used for the preoperative planning and the intraoperative evaluation of glenoid version while performing total shoulder arthroplasties. As the fulcrum axis and the plane of the glenoid fossa are approximately parallel, the fulcrum axis can be used to position patients for performing a true antero-posterior x-ray.