The need for operative treatment for acute acromioclavicular (AC) joint dislocation is unclear. The purpose of this randomized controlled trial was to compare the outcomes after operative treatment with hook plate with those after non-operative treatment in acute AC joint dislocation Rockwood type III or V, separately.

Inclusion criteria were patients aged 18-65 years with acute AC joint dislocation type III or V with availability to start treatment within 3 weeks after trauma. All patients received the same standardized outpatient rehabilitation, and were followed for 24 months. Assessments were based on radiographs, clinical examination, and questionnaires. Primary outcome was Constant score (CS). Secondary outcomes were subjective shoulder value (SSV), QuickDASH, shoulder pain at rest and during movement on a visual analogue scale (VAS), EQ-5D, patients' satisfaction, cosmesis, complications and adverse events. The four groups were compared using one-way analyzes of variance and intention-to-treat.

Included patients (n=124) (mean age 40 years [range 18-64], 91% male) were randomized, stratified by type, to non-operative treatment (n=33 type III and n=30 type V) or operative treatment with hook plate (n=30 type III and n=31 type V) at a single center. Three patients randomized to physiotherapy dropped out before any follow-up measures, leaving 121 patients in the study. Complete clinical follow-up data was obtained from 118 patients at 24 months. At 3 months, patients from both groups treated non-operatively, had significantly better mean CS, SSV, QuickDASH and less pain at rest and movement compared to those operatively treated. At 6, 12, and 24 months, there were no significant differences in CS, SSV, QuickDASH, pain or EQ-5D between the groups regardless interventions. At 24 months, mean CS for non-operatively treated type III was 88, vs. 91 for operatively treated type III, and, for type V, 90 vs. 91, p=.477. At final follow-up, patients had regained 97% of mean CS comparing the non-injured and the injured shoulder and 86% of the patients rated the result as excellent or good. Eleven patients assigned to non-operative treatment, (18%, 6 type III and 5 type V) underwent surgery within 19 months.

Both treatment groups had very good restoration of shoulder function and patient satisfaction at 24 months, and operative treatment did not lead to better outcome compared with non-operative treatment. In conclusion, our study did not support surgery with hook plate for patients with acute AC joint dislocation Rockwood type III or V.