The study summarizes the methodology of clinical and instrumental methods available for the preoperative work-up of patients with acromioclavicular joint dislocation who underwent operative treatment in our department over the past 10 years. It is shown that high-quality preoperative examination of patients is the key to successful surgical treatment, postoperative rehabilitation, and recovery.

The physical examination of acute AC joint dislocation is well studied and described in many guidelines, textbooks, and scientific articles [19-26]. Chronopoulos et al. reported a sensitivity of 77% for the cross-body adduction test, 72% for the AC resistance test, and 41% for the active compression test; the combination of all 3 tests showed a specificity of 95% [27]. The combination of the Paxinos sign and Hawkins–Kennedy test has a sensitivity of 93% if both special tests are negative; the combination of O’Brien’s Test and AC joint tenderness demonstrated the greatest specificity (96.7%), although it was the combination of Paxinos sign and O’Brien’s test that had the highest calculated positive likelihood ratio of 2.71 [28]. According to our study results, no clinical test had 100% accuracy, sensitivity and specificity for detecting AC joint injuries. In patients with Rockwood type III AC joint dislocation, the highest accuracy of 77% was revealed for the piano-key test and Paxinos test, while the cross-body adduction test had 65% sensitivity, and the piano-key test had 88% specificity. In patients with Rockwood type IV AC joint dislocation the piano-key test also had 87% accuracy, and this test, the Paxinos test and the cross-body adduction test had 75% sensitivity; the piano-key test also had 88% specificity. In patients with Rockwood type V AC joint dislocation, the Paxinos test had 89% accuracy and 91% sensitivity and the piano-key test had 88% specificity. An explanation for these findings may be that at the time of injury, it is not always possible to conduct clinical testing of patients due to low pain intensity or in patients with increased subcutaneous fat [29]. If patients do not report immediately after the injury and soft tissue edema increases, the identification of shoulder joint anatomical landmarks becomes difficult. Also, the lack of a specific test for AC joint dislocation is due to the presence of simultaneous concomitant injuries in the shoulder joint.

Developed by Rockwood et al. in 1984, his six-type classification system is the most common and popular classification used for acromioclavicular joint dislocations. Since then, numerous modifications of the classification system have been suggested by various authors. In 2014, the Upper Extremity Committee of ISAKOS subdivided Rockwood’s type III of AC joint dislocation into two types after x-ray examinations in specific view (cross-body stress view), namely, type ІІІ А of stable injures that should be evaluated for conservative treatment and type ІІІ В of unstable injures that should be evaluated for operative treatment, but it is unclear to what extent this subdivision predicts treatment outcomes [30, 31]. De Rooij et al. showed in his survey significant individual variation with regard to diagnosis of AC joint dislocation, with 65 (61%) respondents using the Rockwood classification, and 41 (39%) using the Tossy classification [32]. In our study, 17 patients (16.6%) were classified according to the Tossy classification,32 patients (31.4%) were classified according to the Rockwood classification, and, in 53 patients, the type of injury was not established (51.9%) during earlier management.

Plain radiographs are a standard examination for patients with AC joint injury, as based on the original descriptions by Tossy et al., Allman and Rockwood et al.

A national survey in the Netherlands shows that the diagnosis of AC joint dislocation is mainly based on a combination of physical examination and radiographs; 89% of respondents used anteroposterior and axial radiographs, 33% used Zanca view radiographs, and 15% used weight-bearing radiographs. For decades, surgeons worldwide have debated whether weighted or non-weighted views diagnose AC joint dislocations effectively [33]. Bossart et al. presented 83 pairs of radiographs with and without weights obtained as part of work-up for AC joint dislocation. In only three cases (4%) did the weights cause the coracoclavicular distance on the injured side to increase, thereby revealing a grade 3 injury not evident on plain radiographs [34]. In our study, after performing additional X-ray examination (axillary and Alexander view), the type of AC joint dislocation was changed from Rockwood type II/III to type IV in 3 patients (2.9%), from type II to III in 5 patients (4.9%), and from type III to V in 2 patients (1.9%). The absence of 100% sensitive and specific radiographs for all AC joint dislocation types requires an X-ray examination in at least three views.

Depending on the severity of the injury, the coracoclavicular ligaments can be stretched [35], partially torn, or completely torn; an ultrasound examination can evaluate their contribution to AC joint injury diagnosis. In a human cadaveric study, Gerhard Martin Hobusch et al. determined that horizontal displacement in the AC joint was 1.3 ± 0.9 mm with intact ligaments, 1.4 ± 1.2 mm after transecting the AC ligaments, and 1.9 ± 1.3 mm after additionally transecting the CC ligament. The joint space was 3.3 ± 1.1 mm with intact ligaments, 4.1 ± 1.8 mm in an iatrogenic Rockwood type II injury, and 5.3 ± 3.3 mm in an iatrogenic Rockwood type III injury [36]. Heers et al. performed ultrasound examinations in 13 cadaveric acromioclavicular joints. The mean sonographic width of the joint space was 3.9 mm ± 1.7 mm and the distance from the joint space to the capsular insertions on the clavicle and on the acromion was 4.4 ± 1.4 mm and 5.3 ± 2 mm, respectively [37]. In another study, an ultrasound examination was developed and tested for its ability to detect ligament in jury and mean distance in the AC joint in the horizontal [38] and vertical plane, measure distance between the coracoid process and clavicle, to detect dynamic instability with provocative tests (piano-key test and Paxinos test) in the vertical and horizontal planes, identify detachment of the deltoid and trapezius muscles from the acromial end of the clavicle and injury to the capsular ligament of the sternoclavicular joint, and compare the indicators with the contralateral intact joint.

MRI is optimal for evaluating soft tissue injuries, occult fractures, articular cartilage damage, synovitis, and there is no risk of radiation exposure to the patient, but it is not a routine method for diagnosing AC joint dislocation [39]. However, there is a growing interest in and popularization of the use of this method for assessing AC and coracoclavicular ligamentous injury [40,41]. Kaywan Izadpanah et al. described a new method: stress MRI facilitates the acquisition of morphologic and functional information on acute ACJ injuries; it helps to distinguish between partial and complete ligament tears. In chronic ACJ injuries, it provides functional information about ligament regrinds [42]. In our study, in most patients with acute AC joint dislocation, MRI scans revealed injury to both coracoclavicular ligaments (96% for conoid ligament and 81% for trapezoid ligament), detachment of the deltoid muscle (65%) and trapezius muscle (73%), injury to both acromioclavicular ligaments. Stress MRI should be used as an additional option in difficult cases. Jensen et al. identified one or more concomitant glenohumeral pathologies in 201 patients (53%) who underwent arthroscopically-assisted stabilization of acromioclavicular joint dislocation of Rockwood type III and V. We observed concomitant glenohumeral pathologies (SLAP lesion, biceps tendinitis, partial rotator cuff tear, biceps pulley lesion, os acromiale, distal clavicular osteolysis) in 22 patients (85%). MRI should be mandatory in examination of patients with AC joint injury to choose the tactics of surgical intervention, i.e. an open (mini-open) procedure only on the AC joint or arthroscopically-assisted procedure to treat concomitant glenohumeral pathologies.

CT imaging is not a routine evaluation of AC joint dislocation. Nouh MR et al. determined the morphometric and biometric measurements of the typical AC joint in vivo on a multidetector CT device: anterior and posterior axial AC joint distances were 0.59± 0.27 cm and 0.26 ± 0.11 cm; the coracoclavicular distance was 0.73 ± 0.41 cm; the AC angle was 26.550 ± 14.71 [43]. David R Dyer et al. described the case of a 21-year-old female pedestrian involved in a motor vehicle accident that presented 4 months post-injury with unresolved shoulder pain. However, acute trauma X-ray and CT showed no shoulder abnormality. Repeat plain radiographs showed a moderately increased coracoclavicular distance, an ultrasound examination showed a partial rotator cuff tear and disruption of the AC joint, and a MRI examination showed mild AC joint disruption. Dynamic 4D CT showed a significant translation of the AC joint in multiple planes, which changed future management. With a wide field of view, dynamic 4D CT is an accurate and quick modality to diagnose acute and chronic AC joint injury [42, 44-50]. Given the hazards of ionizing radiation, it is pertinent to investigate diagnostic examinations using non-hazardous imaging modalities to examine the acromioclavicular joint. The frequently sports-related nature of the injury often means that the patient is a young adult.

Delayed and incomplete diagnosis is one of the main reasons for unsatisfactory treatment outcomes for ACC dislocations. To optimize the diagnosis of shoulder joint lesions, we analyzed the available examination methods, and the most informative of them were selected, on the basis of which a set of diagnostic measures was proposed that maximally reflects the condition of the joint without resorting to invasive research methods. According to the results of the study, no clinical test can indicate AC joint dislocation with 100% sensitivity and specificity. Determination of sensitivity and specificity of X-ray examination revealed that no specific X-ray view can detect type III and V of dislocation with 100% accuracy. The accuracy and sensitivity of ultrasound, MRI, and CT are high.

A gold standard for investigating and diagnosing acute AC joint dislocation does not currently exist. There is currently no consensus on a protocol to view acute AC joint injuries. Complete and timely early diagnosis of acromioclavicular dislocation allows for a differentiated approach to surgical treatment tactics, preventing possible complications and fully restoring the function of the injured shoulder joint [51,52].