Acromioclavicular joint dislocations. Epidemiology, radiography and outcome

Abstract: Background: Acromioclavicular joint (ACJ) dislocations are common and frequently affecting young adults injured during sports. The Rockwood classification system is used to grade the dislocations according to the extent of injury to the soft tissues stabilizing the joint. Rockwood type 1 and 2 are not proper dislocations but partial ligamentous injuries without complete ACJ separation and regarded as low-grade injuries. Rockwood type 3-6 are high-grade injuries with complete dislocation of the joint. There is a lack of epidemiological knowledge and controversy regarding how to best radiograph and how to treat ACJ dislocations.Aims: To increase the knowledge regarding epidemiology, radiography and outcome after ACJ dislocation.Patients and methods: This thesis is based on 2 patient cohorts. The first consists of prospectively included patients with ACJ dislocations within the last 2 weeks. Epidemiologic data was obtained, patients underwent study radiographs and were followed using the patient related outcome measures (PROMs); the disabilities of the arm, shoulder, and hand (DASH) score, and the EuroQol-5 dimension (EQ-5D) visual analogue scale (VAS) for life quality. The second cohort included patients with chronic ACJ dislocations planned for reconstructive surgery. Patients were operated using the AC-GraftRope device, a technique that uses an autologous gracilis tendon graft. The shoulder was evaluated using radiographs and computed tomography (CT) scans, as well as DASH score, Constant-Murley score and EQ-5D VAS. The graft donor leg was assessed using measurement of isometric knee flexion strength, and the knee injury and osteoarthritis outcome score (KOOS).Results: Paper I describe the epidemiology of ACJ dislocations. The incidence was 2.0 per 10,000 person-years decreasing with higher age. Sports activity was the most common trauma mechanism and men were injured more often than women. Higher age and traffic accidents were risk factors for high-grade injury. Paper II shows that weighted, or internal rotation radiographs are not useful in uncovering high-grade ACJ dislocations. In paper III patients with Rockwood type 1 and 2 injuries were assessed at 2 years and almost one third were unsatisfied with their shoulder. The trial for paper IV was halted prematurely due to a high rate of complications with 4 out of 8 patients suffering a loss of reduction. In 3 cases the reason was a fracture through the drill tunnel in the coracoid process. Paper V evaluated the donor leg after gracilis tendon harvest and there was no evidence that subjective knee function was affected, but a slight decrease in knee flexion strength compared to the contralateral leg was seen.Conclusions: The incidence of ACJ dislocations is 2.0 per 10,000 person-years. Men are injured more often than women and injury during sports is common. Higher age and traffic accidents are risk factors for high-grade injuries. Weighted or internal rotation radiographs are not useful in the classification of ACJ dislocations. Rockwood type 1 and 2 dislocations are not insignificant injuries with one third of the patients unsatisfied with their shoulder. The AC-GraftRope is not a safe treatment method and should be avoided. Patients seem to tolerate gracilis tendon harvesting well.