The treatment of acromioclavicular (AC) joint injuries that entail disruption of the coracoclavicular (CC) ligaments remains a question of debate. Several different anatomic reconstruction techniques of the CC ligaments have been described in the literature. Recently, the use of tendon grafts (TGs), both autografts and allografts, has gained increased popularity for reconstructing CC ligaments to treat chronic symptomatic AC joint separation. The TG technique is commonly performed with the 2 limbs of a single graft passed through the two 6.0-mm tunnels in the clavicle and fixed with tenodesis screws. More recently, the TG technique was reported to be performed with smaller tunnel diameters of 5.0 mm. Alternatively, AC reconstruction has been performed by use of cortical fixation buttons (CFBs), for which tunnel sizes were most commonly reduced to 4.0 mm. The tunnel diameter can be reduced to as small as 2.4 mm if the inferior coracoid button is introduced arthroscopically through an anterolateral portal. The CFB technique can be combined with a nonanatomic graft reconstruction by looping the graft around the clavicle and does not require additional tunnels.
Several studies have reported lateral clavicle fractures after CC ligament reconstruction with bone tunnels through the clavicle. Martetschlager recently reported a 4.3% incidence rate of lateral clavicle fractures after CC reconstruction using the TG technique with 6.0-mm tunnels and 5.5-mm tenodesis screws. The fractures in this series all occurred at the medial screw hole. The authors reportedly changed to the CFB technique due to the increased risk of clavicle fractures associated with the TG technique. However, little is known of the biomechanical differences between TG (6.0-mm tunnels) and CFB (2.4-mm tunnels) reconstruction techniques on clavicle strength. Furthermore, no data exist about the potential risk factors for an increased onset of clavicle fractures after CC ligament reconstruction, such as small clavicle diameter.
Therefore, the purpose of this study was to compare the strength of matched-pair cadaveric clavicles after surgical treatment with a TG technique that used 6.0-mm tunnels and a CFB technique that used 2.4-mm tunnels, relative to the intact contralateral side, in response to a 3-point bending force. We hypothesized that the TG technique would significantly weaken the clavicle relative to intact and would cause significantly more reduction in clavicle strength than the CFB technique.