Proximal humeral bone loss in stemless shoulder arthroplasty: potential factors influencing bone loss and a new classification system.

INTRODUCTION

Proximal humeral bone loss in total shoulder arthroplasty (TSA) is more frequent than in hemiarthroplasty. Factors such as age, gender, inclination angle, and radiolucent lines may also contribute. Additionally, current bone loss grading systems are often not sensitive enough to detect slight bone changes, especially at the medial calcar where bone loss is commonly observed. This study uses a new, more detailed bone loss grading system to evaluate factors that could influence bone loss at the proximal humerus.

MATERIALS AND METHODS

In this single-center prospective study, patients underwent hemiarthroplasty or TSA with an anatomic stemless prosthesis. Bone loss was measured at the proximal humerus using the new grading system. The effect of treatment type, age, gender, radiolucent lines, and inclination angle on bone loss was evaluated. The Constant-Murley score of patients was assessed and complications recorded.

RESULTS

Ninety-one shoulders were available for the final follow-up examination at a median of 85.0 months (range 82.6-121.1 months). Bone loss was found at the proximal humerus in approximately one-third of shoulders, and significantly more shoulders had bone loss in TSA than in hemiarthroplasty (P = 0.03). However, this difference was no longer significant after stratifying by gender and age (P > 0.05). Bone loss significantly correlated with gender (P = 0.03) but not with treatment type, radiolucent lines, and the postoperative inclination angle (P > 0.05). Most Constant-Murley score components did not differ significantly between shoulders with and without bone loss (P > 0.05). Lastly, six complications and four revisions were reported.

CONCLUSIONS

Results showed gender had the greatest influence on bone loss after stemless shoulder arthroplasty. Furthermore, both patients with or without bone loss can expect similar clinical outcomes with the stemless prosthesis used in this study. Lastly, the new grading system is simple and straightforward to use.