Center of rotation mismatch in total shoulder arthroplasty relative to surgeon experience

Abstract

BackgroundWhile accurate restoration of the anatomic humeral center of rotation (CoR) is challenging in anatomic total shoulder arthroplasty (TSA), increased CoR mismatch may be associated with worse functional outcomes after surgery. The purpose of this investigation was to assess center CoR mismatch in TSA relative to surgeon experience. We aimed to compare mean differences with respect to CoR mismatch for surgeons in their TSA learning-curve period versus surgeons outside of their learning-curve period. MethodsWe identified all patients that underwent a primary TSA from 2010 to 2021 within a single, academic healthcare system. Baseline demographics for patients and surgeons were recorded for each case. Postoperative anteroposterior radiographs were assessed and the CoR mismatch (defined as the distance between the anatomic and prosthetic centers of rotation) was measured for each case. In addition, the direction of mismatch was recorded. Two groups were created for comparison: cases performed by surgeons who had completed more than 30 TSA procedures (non-learning curve group) and TSAs performed by surgeons who had less than or equal to 30 TSA procedures (learning curve group). ResultsThere was a total of 439 TSAs performed by 14 surgeons. There was a statistically significant difference in the mean CoR mismatch between learning curve and non-learning curve groups (4.4mm vs 5.6mm; P < .001), with a 1.2mm greater mismatch measured among TSAs performed by surgeons outside of their learning curve. Surgeons in their learning curve period were less likely to use standard length humeral stems (56% vs 91%) and more likely to use intraoperative radiographs (29% vs <1%). ConclusionsThese data indicate that surgeons within a defined learning curve more closely restored the anatomic CoR in TSA compared more experienced surgeons. Future investigations should aim to more clearly define the learning-curve period for anatomic TSA with respect to both radiographic and clinical outcomes.