Humeral head osteotomy in shoulder arthroplasty: a comparison between anterosuperior and inferoanterior resection techniques

Background: The best chance that a shoulder arthroplasty will restore motion and muscle balance across the glenohumeral joint is by closely replicating natural articular morphology. Defining the humeral osteotomy plane along clear landmarks at the anatomic neck is critical. We hypothesized that a new osteotomy, based on alternative landmarks on the anatomic neck, would restore 3-dimensional humeral head morphology more reliably than the traditional osteotomy. Methods: The anatomic neck was digitized in 30 human cadaver shoulders and compared with its 3-dimensional computed tomography reconstruction. Two different osteotomy techniques were virtually performed: the traditional, following the anterosuperior anatomic neck; and a new technique, defined by the inferoanterior anatomic neck. The length-width difference and orientation (retroversion, inclination) of the resection area were compared between the techniques and with native anatomy. Results: Length-width difference of the anterosuperior resection area was higher than in the inferoanterior osteotomy (6 +/- 2 mm vs. 3 +/- 1 mm; P <.001). Retroversion of the anterosuperior resection plane was higher than the native head (50 degrees +/- 12 degrees vs. 37 degrees +/- 11 degrees; P <.001), whereas retroversion after the inferoanterior osteotomy (32 degrees +/- 12 degrees) did not differ from native (P = .057). Inclination differed after the anterosuperior osteotomy (129 degrees +/- 5 degrees) and the inferoanterior osteotomy (127 degrees +/- 4 degrees) compared with the native head (134 degrees +/- 4 degrees; P = .001). Conclusion: The inferoanterior referenced osteotomy generated a more circular resection area, matching the native humeral head retroversion more closely than in the anterosuperior technique. This study suggests that in shoulder arthroplasty, the humeral resection level should be referenced at the inferoanterior rather than the anterosuperior anatomic neck. Further studies should investigate the biomechanical effects of this alternative resection plane. (C) 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.