Characterizing Glenoid Wear after Hemiarthroplasty with Concentric Glenoid Reaming: A Study of 113 Arthroplasties at Mean of 6.7 Years Follow-Up.

Abstract

Hemiarthroplasty with concentric glenoid reaming using a metal humeral head can be considered in young, active patients who want to remain active and avoid the risks and limitations associated with a prosthetic glenoid component. However, there are concerns with glenoid bone wear over time. This study sought to better characterize the amount and rate of glenoid wear, and associations with glenoid wear with patient-reported outcomes. Patients enrolled into shoulder arthroplasty database with comparable radiographs and minimum 4-year radiographic follow-up were included. Medialization was determined by measuring the position of the humeral head center of rotation relative to a line drawn through the lateral edge of the acromion and parallel with the glenoid face. The amount of medialization was calculated between interval radiographs. Glenoid wear was categorized into minimal/mild (≤5mm), moderate (>5mm but below ≤10mm), or substantial (>10mm). Simple Shoulder Test (SST) were collected preoperatively and annually for each patient. Comparable radiographs of 113 shoulders with a mean radiographic follow-up of 6.7 ± 2.3 years were analyzed. Minimal/mild glenoid wear was noted in 92 (81%) patients, moderate wear in 15 (13%), and severe wear in 6 (5%). The mean total glenoid wear was 2.9 ± 4.3 mm. Based on linear modeling, the glenoid wear rate was calculated at 0.3mm per year, but medialization rates were best predicted by a quadratic function (R² = 0.821; p = 0.001) rather than a linear function. The majority of glenoid wear occurred in the first four years after ream-and-run arthroplasty and plateaued thereafter. On multivariable analysis, younger patients (P = .004) and patients without prior shoulder surgery (P = .015) were at risk for moderate or severe glenoid wear. Change in SST and pain scores were not different in those with minimal/mild wear compared to those with moderate or severe medialization, but open revision rates were higher in those with moderate or severe medialization. Glenoid wear after hemiarthroplasty with concentric glenoid reaming using a metallic humeral head occurs at a rate of approximately 0.3mm/year but may not be linear over time. Improvement in clinical outcomes demonstrated no differences between minimal/mild wear and moderate/severe wear cohorts. Level IV; Case Series; Treatment Study.