There are several factors which increase the instability and complications associated with fixation in unstable distal clavicle fractures. First, there is upward displacement of the medial fragment by the trapezius muscles due to ruptured CC ligament and downward displacement of the lateral fragment by the weight of the arm. Second, the lateral fragment is usually small, comminuted, and consists of soft cancellous bone, which may be not long enough to hold at least two bi-cortical screws[7, 12]. Third, the fracture is located near the AC joint. Because of the particular anatomy and biomechanics of joints in unstable distal clavicle fracture, non-operative treatment cannot reduce and fix the fracture site, which often leads to high non-union or malunion rates[3, 4]. Thus, surgical treatment is widely accepted as the necessary choice. Although many operative techniques including K-wire fixation, anatomic locking plate, hook plate fixation, tension band wiring, CC screw, CC sling, and arthroscopic TightRope, have been used alone or in combination to treat these unstable fractures[5–10], no “gold standard” exists. Most of these techniques have disadvantages which can lead to specific complications, such as fixation failure, metal breakage, migration, secondary clavicle or coracoid fracture, acromial erosion, impingement, or rotator cuff injury.[8–11, 17] In a meta-analysis, Stegeman et al. even recommended avoiding using hook plate due to the high rate and severity of the complications. Moreover, second operations for implant removal are usually needed.
Because the fracture mechanism of a Neer type Ⅱb distal clavicle fracture is the same as in AC joint dislocation (Rockwood classification type-Ⅲ or higher), it is important to perform CC ligament stabilization and recent surgical approaches have focused on improving this method[17, 19–21]. Previous studies have aimed to provide anatomic augmentation of the CC ligaments using open or arthroscopic approaches. Although arthroscopic TightRope is an excellent procedure for CC reconstruction with minimal invasion, it requires a high level of arthroscopic skill and can be complicated by coracoid and clavicle fracture. The method reported here is based on our previous work,which has shown satisfactory clinical and radiographic outcomes in the treatment of acute AC joint dislocation by reconstruction of CC with LARS artificial ligament. Likewise, Yagnik GP et al. described a new technique to treat distal clavicle fractures using cortical button fixation with CC ligament reconstruction, although we note that this method involves more complex devices and materials as well as more steps than the method reported here.
The LARS ligament is regarded as a new generation of artificial ligaments due to its unique design and material. It is made of industrial-strength polyester fibers and has excellent biomechanics in terms of resisting tension, flexion, and torsion load [24, 25]. Since native CC ligaments can withstand tensile forces of up to 621 ± 209 N, the LARS artificial ligament has sufficient strength as a graft for CC reconstruction, 2,500 N or 3,600 N corresponding to 60 fibers or 80 fibers. The high biocompatibility of the LARS ligament has been demonstrated in vitro and in vivo, with the observation of complete cellular and connective tissue growth into the artificial ligament after six months. Thus, the stable joint environment and the “scaffold” function of the LARS ligament can promote the healing process.
In this study, we reported a new surgical technique for the treatment of unstable distal clavicle fractures (type Ⅱb) with modified CC stabilization using LARS artificial ligament, and we evaluated the clinical and radiographic outcomes and complications. The aim of this technique was to restore a strong and stable anatomical reduction and provide sufficient strength to hold the distal clavicle to the coracoid process, thereby promoting CC ligament and fracture healing. Results indicated successful fracture union in an anatomic position, with relatively little soft tissue damage during the operation, which may lead to this high rate of bony union. Follow-ups revealed anatomical reduction in 15 patients and slight loss of reduction in 3 patients, with no loss of reduction cases at follow-up. This is the first report of this fixation method for unstable distal clavicle in the English literature.
Our technique uses only one LARS artificial ligament and two interference screws, reducing the risk of hardware irritation and the need for a second operation. There is no risk of coracoid fracture because there is no drilling through the coracoid during the procedure. As mentioned above, the lateral fragment is usually small and comminuted, so it is difficult to obtain purchase. CC reconstruction using LARS ligament around the coracoid indirectly reduces the medial fracture fragment and leads to a completed CC ligament healing process, which solves the “lateral problem” perfectly.
Although Choi S et al.  reported high union rate and good functional outcome in the treatment of unstable distal clavicle fracture with modified tension band fixation and CC stabilization, their results indicated the possibility of clavicle erosion or fracture. The risk of iatrogenic clavicle fracture also rises while drilling two tunnels through the clavicle for the fixation of LARS artificial ligament in our technique. The clavicle is weakened due to erosion of the clavicle cortex by the implants or a bigger drill hole in the clavicle. In the current study, a reoperation was performed for one patient as a result of clavicular osteolysis around screws, four months postoperatively. No iatrogenic clavicle fracture occurred. At the final follow-up, the Constant scores were 91.2 ± 6.9, and VAS scores were 0.6 ± 1.4, respectively. All 18 patients had returned to their normal daily activities. Similar results were also reported by Kanchanatawan W et al. , who treated distal clavicle fracture with a modified CC stabilization technique using a bidirectional CC loop system, and found that 100% of cases displayed clinical union and good to excellent shoulder function. This excellent success rate suggests that modified CC stabilization techniques similar to ours can also provide good outcomes.
Despite satisfactory clinical and radiographic outcomes in the treatment of unstable distal clavicle fractures, our study also has some limitations. First, the sample size was small and may bring a statistical bias in the evaluation of the results. Second, a control group was not included to demonstrate the advantages of this procedure over other fixation techniques or even non-operative treatment. Third, the average follow-up was 31.8 months, which is a relatively short evaluation period, and thus some complications such as posttraumatic arthritis or clavicle erosion would not have developed yet. Future research to confirm the benefits of this approach should include a larger sample size, control group, and longer follow-up. We are confident our technique is worth further study because of its high union rate and good functional outcome.