Shoulder motion results from a complex interaction between the interconnected segments of the shoulder girdle. Coordination is necessary for normal shoulder function and is achieved by synchronous and coordinated muscle activity. During rotational movements, the humeral head translates on the glenoid fossa in the anterior-posterior plane. Tension developed by the rotator cuff muscles compresses the humeral head into the glenoid fossa. This acts to limit the degree of humeral head translation and establishes a stable GH fulcrum about which the arm can be moved. Previous studies have been limited by the use of contrived movement protocols and muscular coordination has not been previously considered with regard to shoulder rotation movements. This study reports the activation profile and coordination of 13 muscles and 4 muscle groups during a dynamic rotational movement task based on activities of daily living. Eleven healthy male volunteers were included in the study. Electromyography (EMG) was recorded from 13 muscles (10 surface and 3 fine-wire intramuscular electrodes) using a wireless EMG system. EMG was recorded during a movement task in which the shoulder was consecutively rotated internally (phase 1) and externally (phase 2) with a weight in the hand. Muscle group data was calculated by ensemble averaging the activity of the individual component muscles. Mean signal amplitude and Pearson correlation coefficient (PCC) analysed muscle activation and coordination, respectively.Introduction
Methods
The aim of this study was to evaluate prospectively the outcome following arthroscopic Bankart repair using two types of suture anchors, absorbable and non-absorbable. Patients with a diagnosis of recurrent traumatic anterior instability of the shoulder, seen between April 2000 and June 2003 in a single unit, were considered for inclusion in the study. Patients were assessed pre-operatively and post-operatively using a subjective patient related outcome measurement tool (Oxford instability score), a visual analogue scale for pain and instability (VAS Pain and VAS instability) and a quality of life questionnaire (SF-12). The incidence of recurrent instability and the level of sporting ability were recorded. Patients were randomised to undergo surgical repair with either non-absorbable or absorbable anchors. 130 patients were included in the study. 6 patients were lost to follow-up and 124 patients (95%) completed the study. Both types of anchors were highly effective. There were no differences in the rate of recurrence or any of the scores between the two. Four patients in the non-absorbable group and 3 in the absorbable group experienced further episodes of dislocation after a traumatic event. The rate of redislocation in the whole series was therefore, 5.6%. In addition, 4 patients, all of them in the absorbable group (4%) described ongoing symptoms of instability but no true dislocations. 85% of the patients have returned to their previous level of sporting activity. There are no differences in the outcome of Arthroscopic Bankart repair using either absorbable or non-absorbable anchors. Both are highly effective, showing a redislocation rate of 5.6%.
