Humeral stem alignment of curved short stem in reverse shoulder arthroplasty: varus/valgus alignment is not a determinant for clinical outcomes.

BACKGROUND

This study aimed to investigate the influence of curved short stem alignment within the proximal humerus on the clinical outcomes of reverse shoulder arthroplasty. We hypothesized that the varus/valgus alignment would yield clinical outcomes comparable to those of a neutral alignment.

METHODS

We retrospectively reviewed 167 patients who underwent reverse shoulder arthroplasty using the Aequalis Ascend Flex implant between January 2017 and December 2021. The study categorized the patients into 3 groups based on the angle difference between the humeral axis and the stem axis: neutral group (GN, defined as within ±5°), valgus group (GL), and varus group (GR). Functional outcomes were assessed using the visual analog scale pain score, subjective shoulder value, American Shoulder and Elbow Surgeons score, University of California Los Angeles shoulder score, and active range of motion. Routine radiographic evaluations were also conducted to assess the filling ratio and bone resorption.

RESULTS

Among 138 patients, 89 were in the GN group, 37 (27%) in the GL group, and 12 (9%) in the GR group. The average degree of varus alignment was 6 (range from 5 to 7°), while the average degree of valgus alignment was -7 (range from -8 to -5°). According to our findings, the clinical outcomes did not exhibit significant differences among the 3 groups. Furthermore, the radiologic outcomes showed no significant differences among the 3 groups.

CONCLUSIONS

Compared to neutral alignment, varus or valgus alignment of the humeral stem in reverse shoulder arthroplasty using a curved short stem does not significantly affect clinical outcomes.