clavicle [18]. As a common shoulder injury, AC dislocation accounted for about 9% [1]. When acromion was in the statement of an adducted shoulder, the mechanism of AC joint injury was usually a direct impact, which produced a series of injury: AC ligament failure, then failure of the CC ligaments, even the muscular attachments of the trapezius and deltoid in the clavicle [2]. AC dislocation could not only cause AC joint pain and inconvenient movement, but also impair the quality of the patient's normal life or work.
Fixation of the AC joint and reconstruction of the coracoclavicular (CC) ligament have become extremely fundamental surgical methods [2, 3, 4]. Anatomic CC ligament reconstruction could help restore arm function by rectification of the deformity for the acquisition of static and dynamic stability [19]. In CC reconstruction method, the Modified Weaver-Dunn technique was the most widely adopted [20]. But postsurgical complications contained sustainable weakness, pain, and clavicular osteolysis [18]. The Weaver-Dunn technique, may be much weaker and more compliant than the native one with high failure rate [21]. Screws, hook plates and wires, which were usually as AC joint fixation techniques, can easily lead to fracture, osteolysis and related complications [2, 3].
In 2007, for the treatment of complete AC joint dislocations, double endobutton technique was first used and proved effective [5]. Since then, with the application of the double endobutton technique, postoperative complications have been significantly improved [6, 7]. In the AC joint, the double endobutton technique could display stronger load to-failure characteristics and yield less translation than the cerclage sling reconstruction, which was better to restore native AC–CC biomechanics for reducing post-operative pain and preventing recurrent subluxation and dislocation than an allogenic graft [7]. The proposed mini-open technique using the double-button fixation system could be recommend for all type IV injuries and type III injuries in heavy manual labors and high demand upper extremity players [6]. Arthroscopy-assisted reconstruction of the CC ligament by endobutton fixation proved a safe and easy way for the treatment of AC joint dislocation, which can provide reliable fixation, a fast recovery and cause less trauma [8]. The continuous loop device can eliminate the possibility of knot breakage or slippage, and MRI suggested a robust healing response, which can be recommended both for chronic and acute dislocations [9]. Although the use of double endobutton plate technique for the treatment of Rockwood III-VI dislocations has been widely recognized, the improvement of the double endobutton technique has never stopped [8, 9, 10]. According to reset requirement during operation, our novel double endobutton can adjust loop length for satisfying different individual operative methods.
With this limited exposure of the coracoid and minimally invasive approach, a surgeon can place the suture anchors by using the bone tunnel to maintain AC joint well [22]. The 3-tunnel reconstruction technique faithfully restored these insertion points on the clavicle and dominated the movement of the graft on the coracoid process, which was closer to restoring the natural movement of the shoulder than the CC sling technique [11]. Furthermore, for the treatment of AC dislocation, the CC reconstruction using either tendon grafts or cortical fixation buttons produced an overall complication rate of 27.1% [12]. The anatomic CC reconstruction were related with complications such as coracoid and clavicle fractures, and coracoid fracture was more caused from drilling in the coracoid [13]. It was crucial to place the coracoid button centrally under the coracoid base for preventing failure, which also suggested how vital to determine the ideal tunnel location [3, 8, 13-14].
By using 3D navigation, the accuracy of AC joint reconstruction could be improved [23], and image-free navigated CC may help find a precise anatomic position of the bone tunnel drilling with higher first-pass accuracy than conventional drill [15]. Meanwhile, compared to conventional operation, three-dimensional (3D) printing technology had more advantages on the operative time and intraoperative blood loss [24]. The study adapted the centered tunnels in the distal coracoid, which provided more strength for reducing the risk of coracoid process fracture. And make the individualized 3D navigation module for reconstruction of CC ligament tunnel, which can improve the accuracy of bone tunnel location and decrease the risk of the complications. Then 3D print navigation module, which compared with virtual model in Mimics software. The outcome suggested that no differences existed between a real bone tunnel and a virtual bone tunnel for a novel double endobutton in AC joint reconstruction. The accuracy of bone tunnel location for CC reconstruction in adult shoulders based on 3D printing navigation module technology was reliable.
The present study had some limitations. First, in this study, the samples were restricted to the western part of China and gender were unknown. The inferences about the 3D printing navigation module were also limited, especially referring to the treatment of AC joint dislocation. A professional researcher only measured all the samples once carefully, and some observational errors could not be avoided. Finally, this study was an experimental research not a clinical trial, so no sufficient clinical data to prove that the accuracy of bone tunnel location for CC reconstruction in adult shoulders based on 3D printing navigation module technology was reliable and reduced the risk of related complications.