Cementless reverse total shoulder arthroplasty implantation with humeral matchstick autograft augmentation: early radiographic outcomes.

ABSTRACT

BACKGROUND: Humeral-sided complications account for up to 21% of all revision reverse total shoulder arthroplasty (RTSA) surgeries. Stress shielding with large bulky stems can lead to proximal bone resorption per Wolff law, complicating further surgeries. Previously published studies suggest that lowering the metaphyseal implant fill ratio can lead to fewer adaptive radiographic changes and decreased bone resorption. Inspired by these studies, cementless primary RTSA implantation technique with humeral matchstick autografts was proposed to augment cementless humeral constructs, foster the use of a smaller size stem, and create primary stability of the humeral implant even in osteoporotic or in-between size medullary canals. In this study, retrospective review of this cementless RTSA technique with short-term radiographic evaluation was performed. METHODS: Forty-six nonconsecutive patients underwent primary RTSA with a short-stem cementless prosthesis (Stryker Ascend Flex) augmented by matchstick bone grafting from January to July 2020. Patient demographics were recorded, and follow-up radiographs were retrospectively reviewed to assess metaphyseal fill ratios and incidence of stress shielding at minimum 1-year follow-up. Discrepancies between templated and final stem sizes were recorded, along with all intraoperative and postoperative complications. RESULTS: Of the 46 patients originally identified, there were 5 men and 41 women with a mean age of 71 years (standard deviation [SD] 7, range 53-88). Mean templated stem size was 4 (SD 2, range 1-8), whereas the mean final implant size was 2 (SD 1, range 1-3). Mean fill ratios were 0.76 (SD 0.06, range 0.54-0.89) along the metaphysis and 0.67 (SD 0.09, range 0.49-0.83) along the diaphysis. There were no intraoperative humeral fractures from implantation. All patients were available for radiographic follow-up with a mean of 19 months (SD 8, range 12-40). There were 3 cases (7%) of proximal humeral stress shielding, with average fill ratios of 0.857 and 0.807 in the metaphysis and diaphysis, respectively. There were 3 patients (7%) who underwent revision surgeries for baseplate failure and periprosthetic humeral fracture. There were no cases of early humeral loosening. DISCUSSION: Matchstick autograft humeral augmentation is a simple, promising surgical technique with low intraoperative complication rates and good short-term radiographic outcomes. When the implant fill ratio is successfully reduced, there is a possible lower risk of humeral stress shielding. The authors believe this technique can help maximize implant stability in cementless shoulder arthroplasty and preserve humeral bone stock for future revision surgeries.