Biomechanical Analysis of Different Operative Techniques for Complete Acromioclavicular Joint Disruptions

The goal of this study was to evaluate three different operative techniques for acromioclavicular joint fixation: trans-articular K-wire fixation; ligament reconstruction along with a synthetic augmentation device (LARS®); and coracoclavicular Bosworth screw. Mechanical properties were tested in a cadaver study in order to determine the primary mechanical stability during repetitive passive motion. Eighteen fresh cadavers were used to test a cyclic load (50 000 cycles). Secondary joint dislocation and the rate of implant loosening were monitored by standard AP stress X-ray. Metal markers in the coracoid, the acromion, and the lateral clavicle were used to measure the acromioclavicular distance increase (Δ-AC) and the coracoclavicular distance increase (Δ-CC). The range of motion was set on 30-90° of abduction for the first 25 000 cycles and then was raised to 60-120°. The least amount of vertical dislocation was seen in the K-wire and the LARS® group (mean Δ-CC 0.3 mm; range: 0-1.3 mm and 1.5 mm; range 0-6.7 mm, respectively). The Bosworth group showed significantly higher dislocation rates (4.2 mm; range 2.3-7.1 mm; p = 0.005). This was true especially when the abduction range was extended to a maximum of 120°. The rate of implant loosening in the K-wire group was higher than that in the other two groups. This study shows that the LARS® procedure and the K-wires technique give equal results concerning stability after repetitive passive motion, but with a high rate of implant loosening in the K-wire group. According to our findings, abduction should be limited to 90° after implanting a Bosworth screw in order to prevent loosening or failure of the hardware.