Quantitative analysis of traction in the glenohumeral joint. In vivo radiographic measurements.

PURPOSE To analyse change in distance between the humeral head and the glenoid fossa during traction in the maximally loose-packed position (MLPP) and the maximally closed-packed position (MCPP) under standardized conditions. SUBJECTS Six healthy subjects (three male and three female) with a mean age of 40.5 years, volunteered to participate in this study. MATERIALS AND METHODS Subjects were placed with the right shoulder in a modified shoulder brace (Otto Bock Armabduktions-Orthese in Modular Bauweise in 45 degrees abduction in the plane of the scapula with neutral rotation (MLPP). A standard anterior-posterior radiograph of the glenohumeral joint was made. A 14 kg traction force was applied for 40s, and a second radiograph was made. The same procedure was repeated with the shoulder placed in the MCPP, which was 90 degrees abduction and 90 degrees external rotation. A radiologist, blinded for the variable traction or no traction, performed all radiographic measurements. Measurements were made on the same radiographs on two separate occasions (O1 and O2) with a 2-month interval. RESULTS No significant differences were found in mean distance between the humeral head and the glenoid fossa during traction in the MLPP compared to traction in the MCPP (O1: P=1.00) and (O2: P=0.63). CONCLUSIONS Application of a 14 kg force does not result in a significant increase of distance between the humeral head and the glenoid fossa. No significant difference was found between the change in distance of the humeral head and the glenoid fossa after traction in the MLPP compared to traction in the MCPP.