Acromioclavicular joint dislocation is commonly seen in young and active adults. Various treatment modalities, including trans- and extra-articular stabilization methods, have been proposed for acute and chronic AC joint dislocation, with respective clinical results and complications [19, 24]. According to a survey made in Germany, hook plate and arthroscopy-assisted TightRope technique are the popular treatment of choice . However, the majority of orthopedic trauma surgeons do not prefer arthroscope-assisted surgery, for the lack of experience in the specialist. Hook plate is also very popularly used in China. The technique is quite simple and the outcome is effective. However, transarticular fixation with HP can induce bony erosion, shoulder impingement and rotator cuff damage, which can result in unsatisfactory functional results . Moreover, removal of HP is recommended as a secondary surgical intervention. The place of transarticular stabilization with hook plate is challenged by extraarticular anatomical or functional CC reconstruction. In the past decade, materials to reconstruct CC joint evolve significantly, including autologous ligament, LARS, absorbable PDS sling, screw and multistrand titanium cable. It is difficult to define an overwhelming material, because of the difference of surgical methods and lack of persuasive randomized controlled study. Orthopedic trauma surgeons are familiar to MSTC, which is usually used in tension band technique for patellar and olecranon fractures. MSTC conceives of better mechanical property than conventional cable and steel wire. In a recent study conducted by Ye and colleagues, double MSTCs were used to pass through two holes drilled in clavicle, to stabilize the CC joint. The Constant scores were 95.3 on average at final evaluation . Nevertheless, risk of iatrogenic fracture was increased due to two neighboring holes in the mid clavicle. Chen and colleagues described their technique, using a tape to pass through the inferior base of the coracoid process and the clavicular tunnel in a figure-of-8 fashion . The optimal position of the clavicular tunnel is difficult to be determined, due to CC ligament is not a point-like structure.
In the current study, we made a comparative study between two widely used surgical techniques for acute AC joint dislocation, transarticular stabilization with HP and extraarticular stabilization with a single MSTC. Although we believe single MSTC technique might be superior to HP according to our experience, there is no persuasive case–control study previously. As expected, extraarticular stabilization with MSTC yields better functional results, especially in sub-terms of pain, ROM and ADL, revealed by the Constant Scoring system. In detail, we found ranges of motion, including posterior extension, abduction and internal rotation, were significantly worse in patients with AC dislocation treated by hook plate, when compared to those treated by suture loop. For anterior extension, adduction and external rotation, the superiority of MSTC was not statistically significant.
Known shortcomings induced by HP include bony erosion, shoulder impingement and rotator cuff damage, which can lead to persisted pain and restricted ROM in combination or singly. Moreover, rigid and static stabilization of AC joint by HP does not reproduce the primary dynamic unit of lateral clavicle, which contributes significantly to the free motion of shoulder. Degenerative change of AC joint is persistent complication even following removal of HP. In contrast, CC stabilization by MSTC is elastic, although there are no data to show micromotion of lateral clavicle currently. We do not make osseous tunnel for MSTC for two reasons, one is to reduce risk of iatrogenic clavicle fracture, and the other is to improve the position of MSTC over clavicle. During MSTC tightened, it can slide over the clavicle and cease at an optimal position. MSTC is then locked following evaluation of AC joint reduction. In this way, the step to determine the position of clavicular tunnel could be skipped. However, it should be noted that MSTC suture loop is not flawless and perfect. Jerosch et al. once reported that suture loop could lead to anterior displacement of the distal clavicle in relation to the scapula in a biomechanical cadaveric study . Increased stress by MSTC can induce bone resorption, however, it is not significant in our patients probably due to good bone quality and short time of ligamentous healing.
The limitation of current study is the number of patients is not large enough, although we believe a case–control study might be persuasive. The axillary view, which is helpful to determine anterior or posterior dislocation of the lateral clavicle, is not routinely adopted in our study. One-year follow-up after implant removal is a short time to evaluate clinical and radiological results. Moreover, maintenance of hook plate is a little too long in the current study, which might deteriorate the degenerative changes of AC joint. Additionally, the current study is retrospective, but not in a prospective and randomized fashion.