Repair of the entire superior acromioclavicular ligament complex best restores posterior translation and rotational stability
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The acromioclavicular ligament complex (ACLC) is the primary stabilizer against horizontal translation with the superior ACLC providing the main contribution. The purpose of this study was to evaluate the specific regional contributions in the superior half of ACLC, where the surgeon can easily access and repair or reconstruct, for posterior translational and rotational stability.
The superior half of ACLC was divided into three regions; Region A (0°–60°): an anterior 1/3 region of the superior half of ACLC, Region B (60°–120°): a superior 1/3 region of the superior half of ACLC, and Region C (120°–180°): a posterior 1/3 region of the superior half of ACLC. Fifteen fresh-frozen cadaveric shoulders were used. Biomechanical testing was performed to evaluate the resistance force against passive posterior translation (10 mm) and the resistance torque against passive posterior rotation (20°) during the following the four conditions. (1) Stability was tested on all specimens in their intact condition (n = 15). (2) The ACLC was dissected and stability was tested (n = 15). (3) Specimens were randomly divided into three groups by regions of suturing. Stability was tested after suturing Region A, Region B, or Region C (n = 5 per group). (4) Stability was tested after suturing additional regions: Region A + B (0°–120°), Region B + C (60°–180°), or Region A + C (0°–60°, 120°–180°, n = 5 per group).
The translational force increased after suturing Region A when compared with dissected ACLC (P = 0.025). The force after suturing Region A + B was significantly higher compared to the dissected ACLC (P < 0.001). The rotational torque increased after suturing Region A or Region B compared with dissected ACLC (P = 0.020, P = 0.045, respectively). The torque after suturing the Region A + C was significantly higher compared to the dissected ACLC (P < 0.001).
The combined Region A + B contributed more to posterior translational stability than Region B + C or Region A + C. In contrast, combined Region A + C contributed more to posterior rotational stability than Region A + B or Region B + C. Based on these findings, surgical techniques restoring the entire superior ACLC are recommended to address both posterior translational and rotational stability of the AC joint.
KeywordsAcromioclavicular joint dislocation Acromioclavicular ligament complex Translational stability Rotational stability Biomechanics Cadaver study
Authors DM, JDJ, EO, and BS participated in obtaining the data. Authors ADM and MPC were responsible for the analysis of data. Authors FD, FBI, and KB made substantial contribution in designing the methodology and providing oversight to the conduct of the study. All authors (DM, JDJ, EO, BS, ADM, MPC, FD, FBI, and KB) made significant contributions to the development and revision of the manuscript. In addition, all authors have given final approval for the submitted manuscript.
The University of Connecticut Health Center/UConn Musculoskeletal Institute has received direct funding and material support from Arthrex Inc., Naples, FL, USA. The company had no influence on study design, data collection, or interpretation of the results or the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors DM, FD, JDJ, EO, FBI, BS declare no conflict of interest. MPC received personal fee from the Arthroscopy Association of North America. KB is a consultant for Arthrex GmbH, Germany. ADM received grants to his institution from Arthrex Inc. Naples, Fl, USA. He is a consultant for Arthrex Inc. Naples Fl, USA and Ortho x, Inc., Lewisville, TX, USA.
The above study was conducted using only de-identified cadaveric specimens and is therefore not considered human subjects research. Our institutional review board (IRB) provides a Human Research Determination Form to help investigators determine whether IRB review is needed. While we have confirmed with our IRB that projects conducted in our biomechanics laboratory that utilize de-identified specimens does not constitute human subjects research and therefore no review required.
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