Humeral Head Posterior Subluxation on CT Scan: Validation and Comparison of 2 Methods of Measurement

Abstract

Background 

Humeral static posterior translation is important for evaluation of osteoarthritis. Two different methods are compared for absolute difference and reliability.

Methods 

A group of patients with shoulder pathology were analyzed. Images were evaluated 2 times with 2 methods by 3 evaluators. The first method, scapula method (SM), uses the scapula axis as a reference line (line drawn from the medial border of the scapula body to the center of the glenoid). The second method, named mediatrice method (MM), used the “mediatrice” line, drawn as a perpendicular line to glenoid joint surface passing in its middle. The percentage of the humeral head posterior to the line was assessed at the longest AP diameter. A percentage higher than 55% defined posterior subluxation. Reliability of both methods was obtained using consistency and interobserver agreement using intraclass correlation.

Results 

One hundred fifteen cases met the inclusion criteria. The intraobserver reliability was very good using SM and good with MM. The interobserver reliability was very good for SM and good for MM.

Conclusion 

The SM is slightly more reliable for subluxation measurement of the glenohumeral joint, however, both could be used to study the influence of humeral head subluxation on postoperative results.