In this study, we made two important clinical observations. First, results of this study indicated that osteosynthesis using Scorpion plates constitute a promising surgical treatment for unstable distal clavicle fractures. Second, this study suggested that delaying the surgical intervention for more than six days after injury is associated with the increased occurrence of delayed union one year after surgery in distal clavicle fractures.
First, our present results demonstrated that osteosynthesis using Scorpion plates for unstable distal clavicle fractures led to high bone union and low complication rates even though trainees, and not shoulder specialists, performed the surgeries, suggesting that this plate can compensate for the lack of surgical expertise. In this study, six patients (5.7%) experienced delayed bone union and one patient was symptomatic. However, bone union was ultimately achieved in all patients within 1.5 years after surgery. Previous studies investigating the clinical outcomes of at least 30 patients with distal clavicle fractures showed a bone union rate of 94–100% with hook plates [10,12,14] and 97–100% with plates not fixed across the acromioclavicular joint [13,14]. Our findings suggest that the postoperative bone union rate observed with Scorpion plates can be equivalent to that of other plates. In distal clavicle fractures, distal fragments are fragile and often comminuted; therefore, stable fixation with screws is not always obtained. Scorpion plates can be used to fix distal fragments in a manner such that its arms wrap them with soft tissue en bloc. However, plate loosening was observed in four patients (3.8%), presumably because Scorpion plates do not have locking screws. In all these patients, the loosening of screws inserted into distal bone fragments was observed, and the length of the distal screw was considered insufficient. These observations indicate that when performing fixation with the Scorpion plate, it is crucial to select the optimal distal screw length since distal bone fragments were fixed with only one or two screws in addition to the plate arm.
Second, this study demonstrated that the rate of delayed union was significantly higher when surgery was delayed for seven days or more after injury. In addition, although the difference in frequency was not significant, plate loosening and stiffness were only seen in the delayed surgery group. These results suggest that delaying the surgical intervention for seven or more days after injury may be associated with an increase in prostoperative complications. Regarding the timing of distal clavicle fracture surgery, postoperative complications have been reported to increase in subjects that undergo surgery more than four weeks after injury [1, 21]; however, the timing of surgery for acute fractures remains unclear. Recently, proximal humerus fracture fixation within five days of the fracture event was recommended, since a delayed intervention (six or more days after the injury) is related to a significant increase in complications , which is similar to the results of this study. Furthermore, a delayed surgical intervention is thought to complicate the anatomical fracture reduction and increase soft tissue dissection, which may result in a longer fracture union time . This hypothesis raised by Tang et al. can explain our finding of a higher delayed union rate in the delayed surgery group. In this study, one patient who experienced delayed bone union one year after the operation was symptomatic (16.6%), but reoperation was not required, and bone union was finally obtained 1.5 years after surgery. However, considering that some cases of nonunion or plate loosening associated with delayed union were reported to require reoperation with iliac bone [18, 19] grafting, performing surgery for acute distal clavicle fractures within six days after the injury would be preferable.
There are two major strengths to this study. Whereas a majority of previous studies on the surgical outcomes for distal clavicle fractures had a sample size of 50 or less, we were able to perform a large clinical study on more than 100 patients over 10 years. Second, we used Scorpion plates for all unstable distal clavicle fractures and the surgical procedure was standardized during the period, suggesting that the generalization of clinical results using Scorpion plates is possible. On the other hand, there are several major limitations to this study. First, it is difficult to accurately evaluate the superiority or inferiority of Scorpion plate to other implants since this study was not a comparative study between different implants. Second, because of this study’s observational design, biases from unobserved differences may have affected the results. For example, the procedures were performed by 14 surgeons; however, the influence of the abilities of the surgeons or the assistants were not evaluated. Although smoking was reported as a risk factor for nonunion of distal clavicle fractures , smoking status was adjusted between the early and delayed groups in this study. Finally, since questionnaire surveys were not administered in this study, it was not possible to determine additional objective functional outcomes.