Inter and Intra-Rater Reliability of Using Computed Tomography to Assess Prosthesis Position Post Shoulder Arthroplasty

Background Computer models and cadaveric studies have demonstrated that humeral version has a significant impact on the impingement, stability, and range of motion of the prosthetic shoulder joint. Computed tomography (CT) has been used to measure native humeral version, however the reliability of using CT to measure humeral version post reverse total shoulder replacement has not yet been established. Aims To investigate the inter and intra-rater reliability of using CT to assess the post-operative humeral version following shoulder arthroplasty. Methodology Patients underwent a limited CT scan of the operative limb; positioned and protocoled by one consultant radiologist on one machine. The humeral version of the prostheses was calculated individually by two experienced, board certified consultant radiologists. They were blinded to each other’s measurements. The humeral version was calculated using the epicondylar axis. Data Overall, 20 shoulders are included; 12 females (60%), and 10 left-sided (50%). The median anteversion was 0° (range 33° retroversion–27° anteversion; IQ 6.75° retroversion–4.75° anteversion). The inter-rater reliability was 0.985 (95% CI: 0.964–0.994). The intra-rater reliability for radiologist A was 0.988 (95% CI: 0.969–0.995), and the intra-rater reliability for radiologist B was 0.976 (95% CI: 0.942–0.991). Conclusion The use of post operative CT has excellent inter and intra-rater reliability in measuring humeral version following shoulder arthroplasty. This study will facilitate future research regarding impact of the humeral version on patient outcomes.