# Hybrid glenoid component migration after total shoulder arthroplasty: a cohort study using radiostereometric analysis with 2 years’ follow-up

## TL;DR

This study used radiostereometric analysis to track the movement of hybrid glenoid components in shoulder replacements over two years, finding most movement happened in the first six months.

## Contribution

The study introduces radiostereometric analysis to evaluate hybrid glenoid component migration in total shoulder arthroplasty.

## Key findings

- Hybrid glenoid components showed most migration within the first 6 months.
- The mean MTPM at 24 months was 0.97 mm with a plateau phase after initial movement.
- Two revisions occurred, both with positive cultures, but no clear link to early migration was established.

## Abstract

Anatomic total shoulder arthroplasty (aTSA) is an effective treatment for glenohumeral osteoarthritis, but loosening of the glenoid component is a common cause for revision. Our primary aim was to analyze migration of a hybrid glenoid component in aTSA using marker-based radiostereometric analysis (RSA). Second, we aimed to compare early migration with later revision.

Patients with primary glenohumeral osteoarthritis treated with a hybrid glenoid aTSA had tantalum markers inserted in the scapular bone and the glenoid component from 2017 to 2020. We used hybrid glenoid fixation techniques combining cementation with bone in-growth. Patients were followed with RSA radiographs for 24 months. Migration analyses included translation, rotation, and MTPM (maximum total point of motion). Data regarding revisions was retrieved from the Danish Shoulder Arthroplasty Register.

72 patients were included (mean age 69 [SD 8] years, 41 females, 37 left shoulders). The mean MTPM at 24 months was 0.97 mm (95% confidence interval [CI] 0.85–1.1), but migration occurred mainly within the first 6 months (MTPM 0.88 mm, CI 0.78–0.98). The predominant movement was valgus rotation. 2 cases were revised and both had positive cultures. 1 of these had major migration and was found to be loose at revision.

The hybrid glenoid components migrated mainly within the first 6 months (initial seating). Thereafter the components reached a plateau phase and stabilized. Due to the few observations and the relatively short study period, association between early migration and later revision could not be evaluated.