Coracoclavicular ligament reconstruction: coracoid tunnel diameter correlates with failure risk

The current study compared tunnel diameter as an independent risk factor for fixation failure from the coracoid after transcoracoid coracoclavicular reconstruction. The effect of variation in coracoid size and scapular bone density on fixation failure was also studied. Sixty-two cadaveric scapulae were randomized into 1 of 4 groups: a control group with no coracoid hole, a group with a 4-mm transcoracoid tunnel, a group with a 6-mm transcoracoid tunnel, and a group with a socket technique using a 6-mm hole superiorly with a 4-mm hole inferiorly. Bone density measures for all specimens were performed. Coracoid dimensions were quantified. Using a cortical button device, all specimens were loaded to failure with an Instron servohydraulic testing machine (Instron Corp, Canton, Massachusetts). All drilled specimens failed by button pullout, and all control specimens failed by coracoid fracture. Average pullout strength for each tunnel subgroup was as follows: 4 mm, 296.9 N; 6 mm, 146.2 N; 6-4 socket, 261.8 N; control, 762.9 N. No difference was found with respect to tunnel subgroups in base height (P=.25) or bone density (P=.44). Load to failure for the control group was significantly higher than for the other 3 techniques. The 4-mm tunnel load to failure was significantly higher than that for the 6-mm tunnel (P=.006). No difference was found between the 4-mm tunnel and the 6-4 socket technique (P=.853). Although it was not statistically significant, a very strong trend was seen toward increased strength of the 6-4 socket over the 6-mm tunnel (P=.051). The study results show that when employing a transcoracoid reconstruction technique, a 4-mm tunnel technique is significantly stronger than a 6-mm tunnel technique. None of the coracoids drilled with the various tunnels approached the strength of the native coracoid controls using a looped wire technique.