Distal clavicle “A-frame” morphology: a reliable intraoperative guide for arthroscopic distal clavicle excision

The purpose of this cadaveric study was to describe the characteristics of the “A-frame” morphology of the distal clavicle via computed tomography (CT) to determine whether it can be used as a reliable intraoperative guide for arthroscopic distal clavicle excision. Twenty-eight fresh-frozen human cadaveric clavicles underwent a 3-dimensional CT scan using 1.0-mm cuts. The distance from the most lateral aspect of the clavicle to the point at which the superior cortex of the clavicle paralleled the inferior cortex was measured. Measurements were performed in a blinded fashion by a single author on 2 separate occasions. The A-frame was present in all specimens (28 of 28). On the first measurement, the mean distance from the distal clavicle to the point at which the A-frame disappeared was 1.00 cm (range, 0.90-1.08 cm; standard deviation, 0.5 mm). On the second measurement, the mean distance was 1.02 cm (range, 0.90-1.11 cm; standard deviation, 0.6 mm). The intrarater reliability between measurement occasions was 0.65 (95% confidence interval, 0.36-0.82; P < .001). This study demonstrated that the cross-sectional A-frame morphology of the distal clavicle was consistently visualized on CT scans. The A-frame disappeared 1.00-1.02 cm medial to the most lateral extent of the clavicle on CT scans. The disappearance of the A-frame morphology of the distal clavicle can serve as a reliable intraoperative guide for arthroscopic distal clavicle excision.