Stability of acromioclavicular joint reconstruction: biomechanical testing of various surgical techniques in a cadaveric model.

BACKGROUND: Despite reports of excellent results with the Weaver-Dunn coracoacromial ligament transfer, many authors recommend augmenting the transfer with supplemental fixation. The authors of this study sought to determine whether there is a biomechanical basis for this assertion and which augmentative method, if any, most closely restored acromioclavicular motion to normal.

HYPOTHESIS: Augmentative coracoclavicular fixation provides better restoration of normal acromioclavicular joint laxity and an increased failure load when compared with the Weaver-Dunn reconstruction alone.

STUDY DESIGN: Controlled laboratory cadaveric study.

METHODS: Native acromioclavicular joint motion was measured using an infrared optical measurement system. Acromioclavicular and coracoclavicular ligaments were then cut, and 1 of 6 reconstructions was performed: Weaver-Dunn, suture cerclage, and 4 different suture anchors. Acromioclavicular joint motion was reassessed, a cyclic loading test was performed, and the failure load was recorded.

RESULTS: After Weaver-Dunn reconstruction, mean anteroposterior laxity increased from 8.8 +/- 2.9 mm in the native state to 41.9 +/- 7.6 mm (P < or = .01), and mean superior laxity increased from 3.1 +/- 1.5 mm to 13.6 +/- 4.4 mm (P < or = .01). Weaver-Dunn reconstructions failed at a lower load (177 +/- 9 N) than all other reconstructions (range, 278-369 N) (P < or = .05). Reconstruction using augmentative fixation allowed less acromioclavicular motion than Weaver-Dunn reconstruction (P < or = .05) but more motion than the native ligaments (P < or = .05). Specifically, mean superior laxity after reconstruction ranged between 6.5 and 9.0 mm compared with the native ligaments (3.1 +/- 1.5 mm) and the Weaver-Dunn reconstructions (13.6 +/- 4.4 mm). Mean anteroposterior laxity after the reconstructions tested ranged between 21.8 and 33.2 mm, compared with the native ligaments (8.8 +/- 2.9 mm) and the Weaver-Dunn reconstructions (41.9 +/- 7.6 mm).

CONCLUSION: Although none of the augmentative methods tested restored acromioclavicular stability to normal, all proved superior to the Weaver-Dunn reconstruction alone.

CLINICAL RELEVANCE: This study suggests that when performing acromioclavicular reconstruction, supplemental fixation should be used because it provides more stability and pull-out strength than the Weaver-Dunn reconstruction alone.