Posterior approach shoulder arthroplasty: a cadaveric study assessing access

Background: Posterior shoulder arthroplasty is an approach to shoulder replacement. The goal of this cadaveric study was to determine anatomic feasibility for posterior approach shoulder arthroplasty by evaluating access to the glenoid, humerus, and canal. Methods: Twelve fresh frozen shoulders (10 males; 2 females) (mean age, 76 [range, 55-92 years]; weight, 79 kg [range, 34-125 kg]) were used. Traditional exposure techniques and retractors were used to evaluate direct access. Exposure to the glenoid and humerus was evaluated using digital imaging software. Successful placement from stemmed arthroplasty was evaluated using digital radiographs and imaging software. Results: The posterior approach permitted direct access to 88.8% +/- 8.1% of the glenoid. There was access to the center of the humeral head cut surface in 12 of 12 specimens. In 10 specimens, there was 100% access to the entire cut surface of the humerus and peripheral edges. The average access to the humerus was 95.3% +/- 13.4%. Average angulation with stem placement was 0.73 degrees of varus (range, 4.4 degrees of varus to 3.5 degrees of valgus). Regarding lateral plane angulation, there was an average of 0.33 degrees of posterior angulation (range, 3.3 degrees of posterior angulation to 2.5 degrees of anterior angulation). Conclusion: Access to the center of the glenoid and humerus was achieved in all cases. More research is needed to evaluate the clinical efficacy of posterior shoulder arthroplasty, including mid- and long-term outcome and safety studies. (C) 2020 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.