Abstract: We included seven trials (six randomised controlled trials and one quasi-randomised controlled trial) with 704 participants; three of these trials (234 participants) are new to this update. The mean age across the trials was 29 years (range 12 to 90 years), and 82% of the participants were male. All trials compared immobilisation in external rotation (with or without an additional abduction component) versus internal rotation (the traditional method) following closed reduction. No trial evaluated any other interventions or comparisons, such as rehabilitation. All trials provided data for a follow-up of one year or longer; the commonest length was two years or longer. All trials were at some risk of bias, commonly performance and detection biases given the lack of blinding. Two trials were at high risk of selection bias and some trials were affected by attrition bias for some outcomes. We rated the certainty of the evidence as very low for all outcomes. We are uncertain whether immobilisation in external rotation makes a difference to the risk of re-dislocation after 12 months' or longer follow-up compared with immobilisation in internal rotation (55/245 versus 73/243; risk ratio (RR) 0.67, 95% confidence interval (CI) 0.38 to 1.19; 488 participants; 6 studies; I² = 61%; very low certainty evidence). In a moderate-risk population with an illustrative risk of 312 per 1000 people experiencing a dislocation in the internal rotation group, this equates to 103 fewer (95% CI 194 fewer to 60 more) re-dislocations after immobilisation in external rotation. Thus this result covers the possibility of a benefit for each intervention. Individually, the four studies (380 participants) reporting on validated patient-reported outcome measures for shoulder instability at a minimum of 12 months' follow-up found no evidence of a clinically important difference between the two interventions. We are uncertain of the relative effects of the two methods of immobilisation on resumption of pre-injury activities or sports. One study (169 participants) found no evidence of a difference between interventions in the return to pre-injury activity of the affected arm. Two studies (135 participants) found greater return to sports in the external rotation group in a subgroup of participants who had sustained their injury during sports activities. None of the trials reported on participant satisfaction or health-related quality of life. We are uncertain whether there is a difference between the two interventions in the number of participants experiencing instability, defined as either re-dislocation or subluxation (RR 0.84, 95% CI 0.62 to 1.14; 395 participants, 3 studies; very low certainty evidence). Data on adverse events were collected only in an ad hoc way in the seven studies. Reported "transient and resolved adverse events" were nine cases of shoulder stiffness or rigidity in the external rotation group and two cases of axillary rash in the internal rotation group. There were three "important" adverse events: hyperaesthesia and moderate hand pain; eighth cervical dermatome paraesthesia; and major movement restriction between 6 and 12 months. It was unclear to what extent these three events could be attributed to the treatment. The available evidence from randomised trials is limited to that comparing immobilisation in external versus internal rotation. Overall, the evidence is insufficient to draw firm conclusions about whether immobilisation in external rotation confers any benefit over immobilisation in internal rotation. Considering that there are several unpublished and ongoing trials evaluating immobilisation in external versus internal rotation, the main priority for research on this question consists of the publication of completed trials and the completion and publication of ongoing trials. Meanwhile, evaluation of other interventions, including rehabilitation, is warranted. There is a need for sufficiently large, good-quality, well-reported randomised controlled trials with long-term follow-up. Future research should aim to determine the optimal immobilisation duration, precise indications for immobilisation, optimal rehabilitation interventions, and the acceptability of these different interventions.

Plain-language summary: We identified three new relevant studies in this update. In total, this review now includes seven studies with 704 participants. Most of the participants (82%) were male; the average age across the studies was 29 years (range 12 to 90 years). All of the studies investigated just one comparison: immobilisation in external rotation (when the arm is orientated outwards with the forearm away from the chest) versus immobilisation in internal rotation (the usual sling position, where the arm rests against the chest) following closed reduction. Participants were followed over different lengths of time; the most common duration was two years or longer. We are uncertain whether immobilisation in external rotation makes a difference to the risk of re-dislocation at one-year or more follow-up compared with immobilisation in internal rotation. None of the four studies reporting on patient-reported outcome measures for shoulder instability at a minimum of one-year follow-up found evidence of any important difference between the two interventions. We are uncertain of the relative effects of the two methods of immobilisation on resumption of pre-injury activities or sports. One study found no evidence of a difference between interventions in the return to pre-injury activity of the affected arm. Two other studies found greater return to sports in the external rotation group in a small group of participants who had sustained their injury during sports activities. None of the trials reported on participant satisfaction or health-related quality of life. We are uncertain whether there is a difference between the two interventions in the number of participants experiencing instability, defined as either re-dislocation or subluxation (a partial dislocation). The reporting of adverse events (complications) was unsatisfactory. There were reports of nine cases of short-term shoulder stiffness in the external rotation group and two cases of under-arm rash in the internal fixation group. There were three more serious adverse events: abnormal sensitivity and hand pain; abnormal sensation such as tingling in the little finger and along to the elbow; and major movement restriction. It was unclear to what extent these three adverse events could be attributed to the treatment. We rated the certainty of the evidence as very low for all outcomes. This was mainly because there were not enough data and we were unsure how reliable the results were from the individual studies. Thus we are uncertain about the estimates of effect. Overall, the current evidence is insufficient to inform the choice of immobilisation in external versus internal rotation. There is no evidence to inform on any other conservative interventions following closed reduction of traumatic anterior dislocation of the shoulder.