Biomechanical Comparison of Fracture Risk Created by 2 Different Clavicle Tunnel Preparations for Coracoclavicular Ligament Reconstruction.

Acromioclaviclular (AC) joint injuries are common, especially in athletes.8,12 For injuries involving complete disruption of the coracoclavicular (CC) ligaments and greater than 100% increase in the CC distance, surgical intervention is often indicated. Currently, there are multiple surgical techniques utilized to address these injuries, which includes reconstruction of the CC ligaments with tendon grafts. The important role of the anatomic reconstruction of the CC ligaments in AC joint separations has been increasingly recognized. Anatomic CC ligament reconstruction techniques have been shown to be biomechanically superior to other, nonanatomic, methods in several studies.3,9 From a biomechanical perspective, the importance of the CC ligaments in controlling superior and horizontal translations has been well elucidated.5,7 An anatomic reconstruction technique popularized by Mazzocca et al9 requires drilling 2 tunnels from superior to inferior, each at a fixed distance from the distal end of the clavicle, in an attempt to reproduce the native CC ligaments. The tendon graft is looped around the coracoid and passed through the 2 tunnels drilled in the clavicle, and fixation of the graft is maintained with 2 biotenodesis screws. This relatively straightforward technique has demonstrated good results in several biomechanical and clinical studies and has been widely adopted in recent years.1,3 However, as awareness of the anatomic CC ligament reconstruction method increases and as more surgeons have adopted this technique, it has become evident that there is the potential for complications.2,14 Many of the complications have in part been attributed to malposition of the clavicle tunnels. In a study performed by Rios et al,11 the position of the clavicle tunnels established by Mazzocca et al9 was refined, based on further evaluation of clavicular anatomy. These authors established ratios of the total clavicular length for each of the CC ligament attachments. They recommended placing the conoid tunnel at 30% of the clavicular length in the posterior half on the superior clavicle and the trapezoid tunnel at 17% of the clavicular length centered in the midportion of the clavicle. Although these ratios are widely utilized by surgeons, there is recent evidence to suggest that using a 30% ratio for the conoid tunnel may not yield an anatomic conoid.13,16 Xue et al16 performed an anatomic study similar to Rios et al11 that was specific to a Chinese population. Ratios were calculated that represented the distance from the clavicular landmarks to each footprint center divided by clavicular length. They determined the ratios of the distance to the conoid center and to the trapezoid center divided by clavicular length to be 25.5% and 15.6%, respectively. In a recent study, Cook et al2 reported early failure of anatomic CC ligament reconstructions in 28% of patients. They determined that conoid tunnel placement at a ratio of 30% was a significant risk factor in the reconstructions that failed. There were no failures in their study when the conoid ratio was less than 25%. The authors further emphasized the importance of the conoid ligament over the trapezoid for maintenance of reduction. This conclusion has been supported by other biomechanical studies that have shown the conoid to be the most important ligament resisting translation.5 A method of drilling clavicle bone tunnels that better reproduces the anatomic footprint of the conoid ligament while avoiding the risk of posterior wall blowout would be optimal. The purpose of this study was to evaluate the feasibility of a novel single-tunnel technique and compare the biomechanical properties of matched pairs of human cadaveric clavicles to the accepted standard of a 2-tunnel technique for CC ligament reconstruction. The hypothesis was that the single-tunnel technique will yield similar loads to failure as the 2-tunnel technique and better reproduce the anatomic footprint of the conoid ligament.