Biomechanical Comparison of Arthroscopic Repairs for Acromioclavicular Joint Instability

Abstract

Background: Arthroscopic procedures for reconstruction of acromioclavicular (AC) joint separations are increasingly used in clinical practice. Multiple surgical techniques exist, but there are still few data on biomechanical performances of commonly used arthroscopic techniques and fixation methods. Hypothesis: Single and double clavicular tunnel reconstructions show comparable primary stability with a modified Weaver-Dunn procedure, and double tunnel constructs show superior horizontal stability. Study Design: Controlled laboratory study. Methods: The AC joints of 40 cadaveric shoulders were tested for anterior, posterior, and superior translation (70-N load) and maximal load to failure (superior) with the MTS 858 Bionix II Servohydraulic testing system. Shoulders were assigned to 4 groups: (1) native (n = 18), (2) coracoclavicular (CC) reconstruction with 1 clavicular and 1 coracoid tunnel (SCT) fixed with a suture pulley and 2 buttons (n = 8), (3) CC reconstruction with 2 clavicular and 1 coracoid tunnel (DCT) fixed with a suture pulley and 3 buttons (n = 8), and (4) modified Weaver-Dunn reconstruction (n = 6). Results: Native specimens showed a mean anterior translation of 7.92 mm (±1.69 mm), a mean posterior translation of 7.84 mm (±2.09 mm), and a superior translation of 4.28 mm (±1.81 mm). Maximal load to failure was 579.44 N (±148.01 N). The SCT technique showed a mean anterior translation of 5.81 mm (±1.16 mm), posterior translation of 8.30 mm (±1.94 mm), and a superior translation of 2.28 mm (±0.52 mm). The maximal load to failure was 591.35 N (±231.17 N). Anterior and superior translations were significantly less compared with the native specimen ( P = .005 and P = .003). The DCT technique had an anterior translation of 4.68 mm (±0.6 mm), posterior translation of 6.85 mm (±0.83 mm), and superior translation of 2.09 mm (±0.86 mm). The mean maximal load to failure was 651.16 N (±226.93 N). Anterior and superior translations were significantly less compared with the native specimens ( P = .000 and P = .001). No statistically significant differences were shown between SCT and DCT reconstruction for all measurements ( P > .05). One reconstruction of the modified Weaver-Dunn procedure failed directly after mounting it into the testing device. The remaining 5 showed a mean anterior translation of 11.36 mm (±3.17 mm), a mean posterior translation of 13.51 mm (±2.21 mm), and a mean superior translation of 3.31 mm (±0.47 mm). Anterior and posterior translations were significantly increased compared with the native specimen ( P = .019 and P = .000). The mean maximal load to failure measured 311.13 N (±52.2 N) and was significantly less compared with the native specimen ( P = .000). The Weaver-Dunn technique showed significantly less maximal load to failure and more anterior and posterior translation compared with SCT and DCT ( P ≤ .05). Conclusion: Isolated reconstruction of the CC ligaments using single and double clavicular tunnel techniques results in a high load to failure for superior translation, which is equal to the native stability, and less translation in all 3 directions as well as higher superior stability when compared with the modified Weaver-Dunn procedure. A potential drawback is the risk of coracoid fracture, as the high load to failure of the device may exceed load to failure of cortical bone prior to device breakage. Clinical Relevance: Single clavicular tunnel arthroscopic reconstructions of the coracoacromial ligaments show good biomechanical results.