| Abstract ID |
| 20260134 |
| Category |
| Shoulder: Arthroplasty |
| Preferable Presentation |
| Both |
| Title |
| REVERSE SHOULDER ARTHROPLASTY ANGLE ASSESSMENT: MRI VS PLAIN RADIOGRAPHY AND THE IMPACT OF ARTICULAR CARTILAGE |
| Author |
|
| Presenter |
| Thanjira Sumanont |
| Abstract |
| Background: Accurate glenoid inclination is critical in reverse shoulder arthroplasty (RSA) to prevent superior baseplate tilt and scapular notching. While plain radiographs are the standard for measuring the RSA angle, MRI is increasingly utilized in preoperative evaluation. However, differences between cartilage- and bone-based measurements on MRI and their clinical relevance remain unclear. Objectives: To compare RSA angle measurements between plain radiographs and MRI, and to evaluate the effect of articular cartilage on RSA angle. Study design: A retrospective–prospective correlation study was conducted in 42 patients with shoulder pathology who underwent both MRI and true AP (Grashey) radiographs within six months. RSA angles were measured on plain radiographs and MRI using bony (B-RSA) and cartilage (C-RSA) landmarks. Two independent observers performed all measurements twice, six weeks apart. Interobserver reliability was assessed using the intraclass correlation coefficient (ICC). Results: The mean RSA angle on plain radiographs was 17.4 ± 5.5°, comparable to MRI bony measurements (17.8 ± 6.6°). In contrast, MRI cartilage-based measurements were consistently higher (21.5 ± 6.9°), demonstrating a systematic increase of approximately 3–4°. Interobserver reliability was moderate to good for single measurements (ICC = 0.605) and excellent for averaged measurements (ICC = 0.902; p < 0.001). Conclusion: MRI-based bony RSA measurements are comparable to plain radiographs and may be used interchangeably for structural assessment. However, cartilage-based measurements systematically demonstrate higher RSA angles. Given that intraoperative guide pin placement and glenoid reaming are performed on the articular surface, cartilage-based RSA may better approximate the functional intraoperative reference. This discrepancy highlights a potential mismatch between preoperative planning based on bony landmarks and intraoperative execution. |