The ligamentous injury pattern in acute acromioclavicular dislocations and its impact on clinical and radiographic parameters

Abstract Background Acromioclavicular (AC) joint dislocations are classified according to Rockwood (RW), which is based on radiographic findings. Several authors suggested MRI for visualization of the capsuloligamentous structures stabilizing the AC joint. The aim of this study was to describe the ligamentous injury pattern in acute AC joint dislocations by MRI and to investigate associations with clinical and radiographic parameters. Methods 45 (RW I = 5, RW II = 8, RW III = 18, RW V = 14) consecutive patients [5f, 40m, mean age: 33.6 (19-65) years] with an acute AC joint separation were included in this prospective study. All patients underwent physical examination of both shoulders and clinical scores (Subjective Shoulder Value = SSV, Constant Score = CS, Taft Score = TF, Acromioclavicular Joint Instability Score = ACJI) were used to evaluate the AC joint clinically as well as radiographically. Posttraumatic radiography included bilateral anteroposterior stress views and bilateral Alexander views to evaluate vertical instability and dynamic posterior translation (DPT). MRI was performed for assessment of the AC and coracoclavicular (CC) ligaments and the deltotrapezoidal fascia (DTF). Results Radiographic and MRI classifications were concordant in 23 of the 45 (51%) patients, 22 (49%) injuries were misjudged, six (13%) of them were reclassified to a more severe type and 16 (36%) to a less severe type. The integrity of the CC ligaments was found to have a clinical impact on vertical as well as horizontal translation determined by radiographs and on clinical parameters. Patients with an MRI confirmed complete disruption of the CC ligaments showed a radiographic CC-difference of >30% in 68% and complete DPT in 75%. Inferior clinical parameters were noted in these patients as compared to patients with intact or partial disruption of the CC ligaments (CS: 67 vs. 49 points, p Conclusion The integrity of the CC and AC ligaments found on the MRI has an impact on clinical and radiographic parameters.