Injury patterns of the acromioclavicular ligament complex in acute acromioclavicular joint dislocations: a cross-sectional, fundamental study

Abstract

BackgroundHorizontal instability impairs clinical outcome following acute acromioclavicular joint (ACJ) reconstruction and may be caused by insufficient healing of the superior acromioclavicular ligament complex (ACLC). However, characteristics of acute ACLC injuries are poorly understood so far. Purposes of this study were to identify different ACLC tear types, assess type-specific prevalence and determine influencing cofactors.MethodsThis prospective, cross-sectional study comprised 65 patients with acute-traumatic Rockwood-5 (n = 57) and Rockwood-4 (n = 8) injuries treated operatively by means of mini-open ACJ reduction and hook plate stabilization. Mean age at surgery was 38.2 years (range, 19–57 years). Standardized pre- and intraoperative evaluation included assessment of ACLC tear patterns and cofactors related to the articular disc, the deltoid-trapezoidal (DT) fascia and bony ACJ morphology. Articular disc size was quantified as 0 = absent, 1 = remnant, 2 = meniscoid and 3 = complete.ResultsAll patients showed complete ruptures of the superior ACLC, which could be assigned to four different tear patterns. Clavicular-sided (AC-1) tears were observed in 46/65 (70.8 %), oblique (AC-2) tears in 12/65 (18.5 %), midportion (AC-3) tears in 3/65 (4.6 %) and acromial-sided (AC-4) tears in 4/65 (6.1 %) of cases. Articular disc size manifestation was significantly (P < .001) more pronounced in patients with AC-1 tears (1.89 ± 0.57) compared to patients with AC-2 tears (0.67 ± 0.89). Other cofactors did not influence ACLC tear patterns. ACLC dislocation with incarceration caused mechanical impediment to anatomical ACJ reduction in 14/65 (21.5 %) of cases including all Rockwood-4 dislocations. Avulsion “in continuity” was a consistent mode of failure of the DT fascia. Type-specific operative strategies enabled anatomical ACLC repair of all observed tear types.ConclusionsAcute ACLC injuries follow distinct tear patterns. There exist clavicular-sided (AC-1), oblique (AC-2), midportion (AC-3) and acromial-sided (AC-4) tears. Articular disc size was a determinant factor of ACLC tear morphology. Mini-open surgery was required in Rockwood-4 and a relevant proportion of Rockwood-5 dislocations to achieve both anatomical ACLC and ACJ reduction. Type-specific operative repair of acute ACLC tears might promote biological healing and lower rates of horizontal ACJ instability following acute ACJ reconstruction.

Acromioclavicular Joint Injuries in Professional Ice Hockey Players: Epidemiologic and MRI Findings and Association With Return to Play

“…1,2,3,16,20,23,26 All cases in our cohort group illustrated injury of the superior AC ligament. Similar to findings of a prior surgical prospective study investigating morphologic patterns of AC ligament tears in patients with highgrade ACJ injuries, 14 we observed a majority of superior (79%) and inferior AC ligament tears (88%) anatomically involving their clavicular insertions. This morphologic pattern of AC ligamentous injury, particularly involvement of the anterosuperior AC ligament and implications for anteroposterior stability of the joint, may be an important consideration in precise preoperative planning in the setting of high-grade ACJ injuries where AC ligament disruption and incarceration may prevent anatomic ACJ reduction and necessitate open versus arthroscopic ACJ surgical reduction and reconstruction.…”

Horizontal Instability of the Acromioclavicular Joint: A Systematic Review

“…The authors classified AC ligament lesions into 1 of 4 types based on tear pattern—clavicular-sided, oblique, midportion, or acromial-sided—and hypothesized that understanding the type of tear could lead to improved healing and lower rates of recurrent horizontal instability after reconstruction. 27…”

Reconstruction of the Acromioclavicular Ligament Complex Using Dermal Allograft: A Biomechanical Analysis

“…9 This may not be easily pinpointed intraoperatively, as previous studies have shown the ACLC to have several variations of anatomy and injury pattern (clavicle-sided, oblique, midpoint, and acromion-sided ACLC tear) in an acute AC dislocation. 30,31 Moreover, in chronic and revision cases, the ACLC may be irreparable and reconstruction may be necessary. In contrast to the current technique described, the obvious downside of the dermal allograft include an inherent additional monetary cost, along with the potential for added stress to the distal clavicle to potentially fracture.…”