Characterization of humeral head displacements during dynamic glenohumeral neuromuscular control exercises using quantitative ultrasound imaging: A feasibility study

The objectives of the present study were to test the feasibility of measuring humeral head displacements using quantitative ultrasound imaging during the performance of two different dynamic glenohumeral neuromuscular control exercises and to investigate the influence of these exercises on the acromiohumeral distance (AHD) and anterior-posterior distance (APD). Ten individuals who have no history of shoulder injury at the non-dominant shoulder completed three repetitions of an active humeral head lowering exercise and three repetitions of a posteriorisation exercise in a random order in a seated position. The AHD and the APD of the humeral head relative to the glenoid cavity were measured continuously using an ultrasound imaging system during each exercise. Variations in AHD and APD, defined as the difference between the distance obtained before the exercise and the maximal distance reached during the exercise, were compared for each exercises. The active humeral head lowering exercise significantly increased the AHD by 0.94 ± 0.28 mm (relative: + 11.4%), but had no significant effect on the APD. The active humeral head posteriorisation exercise significantly increased the AHD by 0.65 ± 0.41 mm (relative: + 6.3%) and the APD by 1.51 ± 0.51 mm (relative: + 13.8%). The use of quantitative ultrasound imaging allows physiotherapists to quantify inferior and posterior humeral head displacements during dynamic glenohumeral neuromuscular control exercises. These measures, confirming favourable inferior and posterior humeral head displacements at the shoulder, may become useful when studying the effectiveness of rehabilitation programs incorporating dynamic glenohumeral neuromuscular control exercises.