Background. Acute anterior dislocation of the glenohumeral joint may be complicated by injury to neighboring structures. These injuries are best considered a spectrum of injury ranging from an isolated dislocation (unifocal injury), through injuries associated with either nerve or osteoligamentous injury (bifocal injury), to injuries where there is evidence of both nerve and osteoligamentous injury. The latter combination has previously been described as the “terrible triad,” although we prefer the term “trifocal,” recognizing that this is the more severe end of an injury spectrum and avoiding confusion with the terrible triad of the elbow. We evaluated the prevalence and risk factors for nerve and osteoligamentous injuries associated with an acute anterior glenohumeral dislocation in a large consecutive series of patients treated in our Unit. Materials and Methods. 3626 consecutive adults (mean age 48yrs) with primary traumatic anterior shoulder dislocation treated at our unit were included. All patients were interviewed and examined by an orthopaedic trauma surgeon and underwent radiological assessment within a week of injury. Where rotator cuff injury or radiologically-occult greater tuberosity fracture was suspected, urgent ultrasonography was used. Deficits in neurovascular function were assessed clinically, with electrophysiological testing reserved for equivocal cases. Results. Unifocal injuries occurred in 2228 (61.4%) of patients. There was a bimodal distribution in the prevalence of these injuries, with peaks in the 20–29 age cohort (34.4% patients) and after the age of 60 years (23.0% patients). Of the 1120 (30.9%) patients with bifocal dislocations, 920 (82.1%) patients had an associated osteotendinous injury and 200 (17.9%) patients had an associated nerve injury. Trifocal injuries occurred in 278 (7.7%) of cases. In bifocal and trifocal injuries, rotator cuff tears and fractures of the greater tuberosity or glenoid were the most frequent osteotendinous injuries. The axillary nerve was most frequently injured neurological structure. We were unable to elicit any significant statistical differences between bifocal and trifocal injuries with regards to patient demographics. However, when compared with unifocal injuries, bifocal or trifocal injuries were more likely to occur in older, female patients resulting from low energy falls (p<0.05). Conclusions. We present the largest series reporting the epidemiology of injury patterns related to traumatic anterior shoulder dislocation. Increased understanding and awareness of these injuries among clinicians will improve diagnosis and facilitate appropriate treatment

The generally-accepted treatment for large, displaced fractures of the glenoid associated with traumatic anterior dislocation of the shoulder is operative repair. In this study, 14 consecutive patients with large (> 5 mm), displaced (> 2 mm) anteroinferior glenoid rim fractures were treated non-operatively if post-reduction radiographs showed a centred glenohumeral joint.

After a mean follow-up of 5.6 years (2.8 to 8.4), the mean Constant score and subjective shoulder value were 98% (90% to 100%) and 97% (90% to 100%), respectively. There were no redislocations or subluxations, and the apprehension test was negative. All fragments healed with an average intra-articular step of 3.0 mm (0.5 to 11). No patient had symptoms of osteoarthritis, which was mild in two shoulders and moderate in one.

Traumatic anterior dislocation of the shoulder, associated with a large displaced glenoid rim fracture can be successfully treated non-operatively, providing the glenohumeral joint is concentrically reduced on the anteroposterior radiograph.