Fluoroscopic measurements of the glenohumeral joint position and space in true anteroposterior and axillary views – a reliability study

Two-dimensional (2D) fluoroscopy has been used in shoulder pathologies to estimate the humeral head position (HHP) in the true anteroposterior (AP) view. However, there is a lack of evidence regarding the reliability estimating it in the axillary view and in measuring the shoulder joint space width (JSW). True AP view images (n=36) of subjects with adhesive capsulitis were taken in supine in multiple arm abduction positions. The axillary view images (n=48) were taken in supine and prone in 75° of abduction. The HHP was assessed in the glenoid reference frame. The position and radius of the humeral head along with the superior, inferior, anterior, posterior, and middle JSWs were measured in each image. All the images were coded and randomly presented twice to a physiotherapist at a gap of 48-72 h for intra-rater reliability and to 2 therapists and an orthopaedic surgeon for inter-rater reliability. Reliability was expressed using intraclass correlation coefficients (ICC) and standard error of measurement (SEM). In both the views, inter-rater, and intra-rater reliability was excellent for the radius of the humeral head (inter-rater – 0.95-0.97 and intra-rater -0.98)], moderate (ICC: 0.70 and 0.76), and excellent (ICC: 0.89 and 0.93) for HHP. The reliability for JSWs was moderate to good (ICC: 0.66-0.82) for inter-rater and good to excellent (ICC: 0.75-0.95) for intra-rater analysis. The SEM for HHP and JSWs were <0.4 mm for intra-rater analysis, and <0.7 mm for inter-rater reliability in both views. The study demonstrated that the glenohumeral arthrokinematic parameters can be measured with good to excellent levels of reliability when using 2 D fluoroscopy. The study is part of a clinical trial (Clinical Trial Registry India: CTRI/2018/12/016657).