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.

Effect of subacromial decompression on laxity of the acromioclavicular joint: biomechanical testing in a cadaveric model.

Subacromial decompression is a well-accepted treatment for impingement syndrome when nonoperative therapies have failed. However, recent clinical data have raised concern that arthroscopic subacromial decompression may lead to laxity of the acromioclavicular joint and, potentially, predispose patients to late postoperative acromioclavicular joint pain. Our goal was to determine whether subacromial decompression with co-planing of the distal clavicle alters the laxity, or compliance, of the acromioclavicular joint in a cadaveric model. Eighteen cadaveric shoulders were dissected and tested in a specially designed rig, driven by a hydraulic materials testing machine. One hundred-Newton loads were applied to the distal clavicle in the superior, posterior, and anterior directions, while acromioclavicular joint motion was recorded with a 3-dimensional infrared optical measurement system. Acromioplasty was performed with a posterior-referenced cutting block technique and included co-planing of the distal clavicle in all specimens. Joint compliance before and after subacromial decompression was compared with the paired t test. Subacromial decompression increased anteroposterior compliance by 13%, from 8.8 +/- 2.9 mm (mean +/- SD) in the intact joint to 9.9 +/- 3.1 mm (P =.001). Subacromial decompression increased superior compliance by 32%, from 3.1 +/- 1.5 mm in the native specimen to 4.1 +/- 1.8 mm (P =.03). These observations may have implications for the technique of acromioplasty. Although the immediate result of acromioplasty with co-planing appears to be an increase in the compliance of the acromioclavicular joint, the clinical significance of these findings has yet to be determined.