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Purpose: To evaluate different stabilisation techniques for acromioclavicular (AC) joint separations, including direct AC repair, and to compare the properties of the stabilised and native joints., Methods: An established in vitro testing model for the AC joint was used to analyse joint stability after surgical reconstruction [double TightRope (DTR), DTR with AC repair (DTR + AC), single TR with AC repair (TR + AC), and PDS sling with AC repair (PDS + AC)]. Twenty-four human cadaveric shoulders were randomised by age into four testing groups. Joint stiffness was measured by applying an axial load during defined physiological ranges of motion. Similar tests were performed for the native joints, after dissecting the coracoclavicular and AC ligaments, and after surgical reconstruction. Cyclic loading was performed for 1000 cycles with 20-70 N and vertical load to failure determined after cyclic testing., Results: Axial stiffness for all TR groups was significantly higher than for the native joint (DTR 38.94 N/mm, p = 0.005; DTR + AC 37.79 N/mm, p = 0.015; TR + AC 45.61 N/mm, p < 0.001 vs. native 26.05 N/mm). The axial stiffness of the PDS + AC group was similar to that of the native joint group (21.4 N/mm, n.s.). AC repair did not significantly influence rotational stiffness. Load to failure was similar and >600 N in all groups (n.s.)., Conclusion: Reconstruction of AC dislocations with one or two TRs leads to stable results with a higher stiffness than the native joints. For the PDS + AC group, axial stiffness was similar to the native situation, although there might be a risk of elongation. Direct AC repair showed no significantly increased stability in comparison with reconstructions without direct AC repair. Thus, a direct AC repair seems to be dispensable in clinical practice, while TRs or PDS cerclages appear to provide sufficiently stable results.

Purpose: The aim of this cadaveric study was to evaluate the accuracy, feasibility, and operation time of a novel electromagnetic navigation system (ENS) and procedure for transclavicular-transcoracoid tunnel placement compared with a standard minimally invasive (SMI) reconstruction method for minimally invasive arthroscopically assisted anatomic acromioclavicular joint reconstruction., Methods: Ten arthroscopically assisted electromagnetic-navigated transclavicular-transcoracoid drilling procedures and 10 SMI procedures were performed on 10 human cadavers using 2 TightRope reconstructions (Arthrex, Naples, FL) for each site. Postoperative computed tomography scans were acquired to determine tunnel placement accuracy. Optimal coracoid tunnel placement was defined according to the anatomic insertions of the trapezoid and conoid ligaments with the oblong button placed in a center-base position at the coracoid undersurface without cortical breach or fracture. Both reconstruction procedures were performed without fluoroscopy., Results: Successful tunnel placement was accomplished in 98.8% using the ENS method and in 83.8% using the SMI procedure (P = .087). The mean overall operation time was 28.5 ± 6.6 minutes for the ENS method and 35.2 ± 3.9 minutes for the SMI method (P = .012). The ENS procedure required no directional readjustments or restarts. Drill misguidance with subsequent cortical breach occurred twice in the SMI group. In both groups no fractures were documented., Conclusions: In this descriptive laboratory study, both the ENS and the SMI techniques achieved the desired anatomic reconstruction. Compared with the SMI method, the ENS procedure showed higher accuracy, required a shorter operation time, and was associated with no complications., Clinical Relevance: Length of surgery, drilling accuracy, and reduction of radiation exposure in acromioclavicular joint reconstruction procedures affect the safety of both patients and surgeons., (Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background: Traumatic acromioclavicular (AC) joint dislocations can be addressed with several surgical stabilization techniques. The aim of this in vitro study was to evaluate biomechanical features of the native joint compared with 3 different stabilization methods: locking hook plate (HP), TightRope (TR), and bone anchor system (AS)., Hypothesis: The HP provides higher stiffness than the anatomic reconstruction techniques., Study Design: Controlled laboratory study., Methods: A new biomechanical in vitro model of the AC joint was used to analyze joint stability after surgical repair (HP, TR, and AS). Eighteen cadaveric specimens were randomized for bone density and diameter in the midclavicle section. Joint stiffness was measured by applying an axial load and a defined physiological range of motion for internal and external rotations and upward and downward rotations. Data were recorded at 3 stages: for the native joint after dissecting the AC ligaments, directly after repair, and after axial cyclic loading (1000 cycles with 20 and 70 N at 1 Hz). To evaluate which implant mimics physiological joint properties best, axial stiffness of vertical stability was assessed in combination with rotation. Finally, static loading in the superior direction was applied until failure of the joints occurred., Results: Axial stiffness of the TR and AS groups was 2-fold higher than for the HP group and the native joint (67.1, 66.1, and 22.5 N/mm, respectively; P < .004). Decreased load-to-failure rates were recorded in the HP group compared with the TR and AS groups (248.9 ± 72.7, 832.0 ± 401.4, and 538.0 ± 166.1 N, respectively). The stiffness of the rotations was not significantly different between the treatment methods but was lower in horizontal and downward rotations compared with the native state. Thus, native AC ligaments contributed a significant share to joint stiffness., Conclusion: The TR and AS groups demonstrated higher vertical load capacity. Compared with the TR and AS, the HP demonstrated an axial stiffness closest to the native joint. For restoring physiological properties, reconstruction of the AC ligaments may be necessary., Clinical Relevance: The results show different biomechanical properties of the HP and anatomic reconstructions.