Combination of Surgical Techniques Restores Multidirectional Biomechanical Stability of Acromioclavicular Joint

Purpose: To measure the multiaxial stability of the acromioclavicular joint before and after transection of the acro-mioclavicular capsule and coracoclavicular ligaments and after sequential repair of acromioclavicular and coracoclavicular ligaments. Methods: Biomechanical testing was performed on fresh-frozen human cadaveric shoulders (N = 6). Translational and rotational stability in the vertical and horizontal planes was measured in intact specimens, after transecting the acromioclavicular and coracoclavicular ligaments, and after sequentially performing the following pro-cedures: single-bundle coracoclavicular repair (CCR), modified Weaver -Dunn procedure (WD), and acromioclavicular stabilization (ACS). Results: Resecting the acromioclavicular and coracoclavicular significantly reduced translational stiffness in the inferior and anteroposterior directions, as well as rotational stiffness about the vertical and anteroposterior axes. All 3 surgical procedures increased inferior translational stiffness relative to the intact condition (Intact: 38 +/- 9 N/ mm, CCR: 54 +/- 23 N/mm (P = .03), CCR+WD 52 +/- 20 N/mm (P = .07), CCR +/- WD+ACS 50 +/- 21 N/mm (P = .17)). However, the combination of CCR, modified WD, and ACS resulted in the greatest increase in stiffness in internal rotation (Intact: 12.5 +/- 7.4 cNm/deg, CCR: 1.2 +/- 1.1 cNm/deg, CCR+WD 7.2 +/- 3.0 N*m/deg [P = .023], CCR+WD+ACS 11.6 +/- 4.9 cNm/deg [P = .055]). Conclusions: The cumulative stability of CCR, WD reconstruction, and ACS appears to be additive. Our findings provide a biomechanical justification for combining all three techniques. Biomechanical studies assessing the performance of various acromioclavicular repairs and reconstructions should therefore incorporate multi-axial testing in their protocols.