Acromioclavicular joint suture button repair leads to coracoclavicular tunnel widening.

PURPOSE

Biomechanical evaluation of three different suture button devices used in acromioclavicular joint repair and analysis of their effect on post-testing tunnel widening.

METHODS

Eighteen human shoulder girdles were assigned into three groups with a similar mean bone mineral density. Three different single-tunnel acromioclavicular repair devices were tested: (1) AC TightRope with FiberWire; (2) AC Dog Bone Button with FiberTape; (3) Low Profile AC Repair System. Biomechanical testing was performed simulating the complex movement of the distal clavicle as follows. A vertical load of 80 N was applied continuously. The rotation of the clavicle about its long axis was set at 10° anterior and 30° posterior for 2500 cycles at 0.25 Hz. The horizontal translation of the clavicle was set at 6 mm medial and 6 mm lateral for 10,000 cycles at 1 Hz. The coracoclavicular distance was measured before and after testing. After testing, each sample underwent micro-CT analysis. Following 3D reconstruction, the area of the bone tunnels was measured at five defined cross sections.

RESULTS

In TightRope and Dog Bone groups, all samples completed testing, whereas in the Low Profile group, three out of six samples showed system failure. The mean absolute difference of coracoclavicular distance after testing was significantly greater in the Low Profile group compared to TightRope and Dog Bone groups (4.3 ± 1.3 mm vs 1.9 ± 0.7 mm vs 1.9 ± 0.8 mm; p = 0.001). Micro-CT analysis of the specimens demonstrated significant tunnel widening in the inferior clavicular and superior coracoid regions in all three groups (p < 0.05).

CONCLUSION

Significant tunnel widening can be observed for all devices and is primarily found in the inferior parts of the clavicle and superior parts of the coracoid. The Low Profile AC Repair System showed inferior biomechanical properties compared to the AC TightRope and AC Dog Bone devices. Therefore, clinicians should carefully select the type of acromioclavicular repair device used and need to consider tunnel widening as a complication.