Biomechanical Analysis of Different Operative Techniques with complete ACJ disruption

Authors: Krenn

References: Osteo Trauma Care 2005 – 154 – 159

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 motions. 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 (-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 0.3mm;
range: 0 - 13mm and 1.5mm; range 0 - 67mm, respectively). The Bosworth group showed significantly
higher dislocation rates (4.2mm; range 2.3 - 7.1mm; 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.