Summary

This study investigates the association between osteolysis and tray protrusion in reverse shoulder arthroplasty , finding that greater tray protrusion increases osteolysis in the proximal humerus. Analysis of 50 patients showed medial and lateral tray protrusion, suggesting the need to select smaller trays and appropriate offsets to minimize this complication, especially in smaller patients.

Abstract

Introduction

The postoperative complications of reverse shoulder arthroplasty (RSA) include osteolysis around the humeral stem, potentially leading to peri-stem fractures and bone loss at revision surgery. In a previous study, we reported that proximal humeral osteolysis was significantly more frequent in cases with a large humeral tray diameter. The aim of this study was to investigate the relationship between osteolysis and the amount of tray protrusion, along with other factors. We hypothesized that osteolysis around the proximal humerus would increase with greater tray protrusion.

Methods

This study include 50 patients who underwent RSA for massive rotator cuff tears, cuff tear arthropathy and osteoarthritis with a follow-up period of at least two years. RSA was performed using Comprehensive Reverse Shoulder System (Zimmer-Biomet, Warsaw, IN, USA), and a micro stem (stem length 55mm) was used in all cases. Anteroposterior radiographs at the final follow-up were used to classify osteolysis of the greater tuberosity and calcar region from grade 0 to 4 according to the Inoue classification.. Age, sex, humeral tray diameter, transverse diameter of the stem, metaphyseal and distal medullary filling ratio(FRmet, FRdia), medial and lateral protrusion of the tray on plain radiograph immediately after surgery (MP, LP) were analyzed as risk factors. Univariate and multivariate logistic regression analyses were performed to evaluate the data.

Results

Univariate analysis showed that osteolysis of the greater tuberosity was associated with gender, transverse diameter of the stem, FRmet, FRdia, MP and LP, while osteolysis of the calcar was associated with tray diameter, FRmet, FRdia, MP and LP. Multivariate analysis revealed that osteolysis of the greater tuberosity was associated with MP and LP, and osteolysis of the calcar was associated with FRdia, MP and LP.

Discussion

The tray protrusion was associated with osteolysis in the proximal humerus both medially and laterally. To prevent osteolysis, smaller trays should be selected for smaller patients , and an appropriate offset option should be chosen in each case to avoid tray protrusion.