Intra- and Inter-rater Reliability of Postoperative Radiographic Analysis of Reverse Shoulder Arthroplasty in 49 Shoulders After Proximal Humerus Fracture.

Abstract

Introduction: The lateralization shoulder angle (LSA), the distalization shoulder angle (DSA) and the new "pentagon" concept are tools used in scheduled shoulder surgery to evaluate the positioning of reverse shoulder arthroplasty (RSA) implants. There is no information on the intra- and inter-rater reliability of these tools in the context of RSA for a proximal humerus fracture. The first hypothesis was the high reliability of the intra- and inter-rater analysis of the LSA and DSA angles. The second hypothesis was the reproductibility of the pentagon based on LSA and DSA analysis.

Methods: Forty-nine patients were evaluated retrospectively with a minimum of 2 years radiological follow-up after RSA surgery. Tuberosity healing was evaluated using an AP radiograph of the shoulder and their location analyzed within the said "pentagon" defined by the LSA/DSA angles and the maximum lengthening recommended.

Results: The intra-rater analysis found strong to an almost perfect agreement for the LSA and DSA. The agreement was moderate to strong for the pentagon. The inter-rater analysis found a fair agreement for the LSA and moderate agreement for the DSA and pentagon.

Conclusion: The LSA/DSA is used in patients undergoing RSA for glenohumeral OA. In this context, the tuberosities were intact and certain complications inherent to RSA for humeral fracture were not present. The population studied here (RSA after fracture) creates an interpretation bias due to the difficulty in analyzing tuberosity position.

Level of evidence: 4, retrospective study.