Clavicle Elevation or Shoulder Girdle Depression in Acromioclavicular Joint Dislocation: A Radiological Investigation

Abstract

Background: The side-comparative coracoclavicular (CC) distance is used to describe the vertical instability component of acute acromioclavicular (AC) joint dislocations. Elevation of the clavicle or a depression of the shoulder girdle can lead to an increased CC distance. The dislocation direction has not yet been investigated and is not included in common classification systems. Hypothesis: Clavicle elevation is primarily responsible for vertical dislocation in AC joint separation. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Weighted and nonweighted bilateral plain anteroposterior views of the shoulder girdles of patients with AC joint dislocations (Rockwood [RW] types III and V), diagnosed in our trauma department between 2001 and 2018, were included in this study. After determining the CC distance, a side-comparative determination of the positions of both the clavicle and shoulder girdle, with reference to the spinal column, was conducted. Results: In total, 245 bilateral plain anteroposterior views were evaluated (RW III, n = 116; RW V, n = 129). All patients showed a side-comparative clavicle elevation (mean ± SD: RW III, 5 ± 14 mm; RW V, 11 ± 17 mm) in weighted and nonweighted views. While no depression of the shoulder girdle was measured in RW III injuries (weighted and nonweighted views, 0 ± 11 mm), dropping of the shoulder girdle in RW V lesions on nonweighted views was observed (–5 ± 11 mm). Conclusion: Vertical dislocation is mostly associated with clavicle elevation in RW III injures, while in high-grade AC joint dislocations (RW V), a combination of clavicle elevation and shoulder girdle depression is present. A significantly greater superior displacement of the clavicle in RW V injuries was seen in weighted views, while a depression of the shoulder girdle could be detected in nonweighted views. For the first time, these results include the dislocation direction in the classification of an AC joint injury. Further studies are needed to investigate the extent to which dislocation types differ in optimal therapy and outcome.

Kinematic Alterations in the Shoulder Complex in Rockwood V Acromioclavicular Injuries During Humerothoracic and Scapulothoracic Movements: A Whole-Cadaver Study

“…Regarding elevation of the clavicle, a significantly increased elevation was seen in the starting position in the lesioned condition (Figure 3B). Together with the simultaneous inferior translation of 10 mm of the scapula compared with the clavicle, the presence of a combined elevation of the clavicle and depression of the shoulder girdle in a Rockwood V lesion can be confirmed, as reported by Azar et al 2 (Figure 7). Again, Oki et al 21 also found an increased elevation in a Rockwood V injury but, in contrast to our findings, not at the start but only between 95° and 110° of coronal plane elevation.…”

“…26 The 3-dimensional kinematics of the SC, ST, and AC joints were measured. A total of 6 movements were analyzed: 3 humerothoracic movements ( [1] elevation in the coronal plane, [2] elevation in the sagittal plane, [3] horizontal adduction) and 3 ST movements ([4] protraction, [5] retraction, and [6] shrug). Coronal plane elevation started with the arm at the side and was performed with the elbow extended and the thumb pointing up until complete elevation.…”

The Role of the Acromioclavicular Ligament in Acromioclavicular Joint Stability: A Cadaveric Biomechanical Study

“…We should include examination of the AC joint to diagnose the dislocation correctly. For example, magnetic resonance imaging 1 and weighted radiographs with checking bilateral CC distance 2 would better discriminate between type 2 and 3 injuries. The AC ligament is said to help the horizontal stability of the AC joint; our results demonstrate that it also aids in superior stability.…”

Imaging of the Acromioclavicular Joint: Anatomy, Function, Pathologic Features, and Treatment

“…The deltoid muscle normally acts as a clavicular depressor, counteracting the elevation produced by the sternocleidomastoid and trapezius muscles (5,35). When the clavicular attachments of this muscle are disrupted, the elevators are unopposed, enabling superior clavicular migration while the remaining shoulder girdle sags inferiorly, resulting in wide diastasis of the CC space (58,65).…”