So far there has been little agreement about the management of replaced mid-shaft clavicle fracture. Both conservative and operative treatment has been recommended when reviewing previous studies. In this study, we have found that surgical fixation has higher union rate, shorter union time and takes less time to resume strength, movement and working ability when compared with conservative therapy. Also, operative treatment helps avoid malunion and asymmetry.

In the non-operative group, patients experienced a longer healing time, indicating that internal fixation might be helpful to maintain stability and fracture fragment contact and accelerate process of union, This consequence is consistent with the findings of Kumar (2022) [7], who reported a union rate of 60% within 12 weeks for operative patients, compared to only 28% for conservative patients.

In this study, we found that the rate of non-union in non-operative patients was significantly higher compared to operative patients, which aligns with previous research [9,10,11,12]. A displacement distance of more than 2cm has been considered a relative indication for surgery [13], but in our centre, conservative treatment was always an option regardless of the degree of displacement. Through strict immobilization in the early stages and a well-designed rehabilitation strategy, we were able to achieve a controlled non-union rate of 12.7%, which is lower than previously reported data [4]. It is worth noting that none of the non-operative patients with non-union opted for surgery, suggesting that the negative impact of this issue may be limited.

Given the nature of Robinson 2B type clavicle fractures, malunion is almost inevitable [14]. In our study, all non-operative patients who achieved bone healing showed signs of malunion. However, not all patients noticed this malformation, and less than half of the non-operative patients reported shoulder asymmetry. There is a limited amount of literature focusing on the cosmetic issues of clavicle fractures, but it is generally believed that cosmetic problems are mainly caused by incision wounds, particularly poor healing [15]. Incision scars can cause cosmetic problems and dissatisfaction among patients, but cosmetic problems of asymmetric shoulder caused by malunion has been ignored for a long time. In our research, we found no superior cosmetic satisfaction in conservative groups at the final follow-up. It is important to note that less than half of non-operative patients noticed shoulder asymmetry, while all operative patients had incision scars. This suggests that the cosmetic problem caused by malunion may have been underestimated.

The incidence of complications varies among different studies mainly due to the vague definition of “complication”, and the conclusion could differ among studies [16]. In our study, complications of conservative and operative group were discussed separately, and common complications were investigated further to reveal possible mechanism. For a long time, complications of surgery have been primarily associated with grafts and incisions, with skin numbness being rarely reported [17]. Skin numbness occurs as a result of damage to the supra-clavicle and cutaneous nerves during the operation, which can occur around the surgical site or in other areas of the shoulder, but it can theoretically be caused by the bump pressure of malunion as well [18]. Despite efforts to protect the nerves, it is challenging to keep them intact due to anatomical variations and the need for surgical field exposure. In our study, nearly half of operative patients had decreased sensation of shoulder skin, which is not seen in non-operative group, suggesting that this complication is mainly the consequence of iatrogenic injury instead of mechanical pressure. Among those cases with numbness, some recovered after one year, while others persisted. We have not yet found convinced evidence of its negative effect on satisfactory, and this field leaves much for further study.

At the finial follow-up, patients in both groups had similar function scores, including Quick-DASH and Constant-Murley. The former scale focus on the performance in daily life, and another none mainly reflects motion of shoulder. Scores in both groups were quite high, indicating that both conservative and operative treatment for mid-shaft clavicle fracture could achieve a satisfactory consequence. This conclusion is consistent with some previous literature [19,20,21]. However, some other studies have declared that surgical treatment brings better outcomes than conservative treatment [17, 22]. We would like to attribute this difference to different length of follow-up in various researches, as the advantage of surgery is typically reflected in the early stages [23]. In our study, as the follow-up time is relatively longer than most of previous articles, we suppose that the advantage in clinical function of operative might be eliminated by time.

This study also examined three main areas that reflect the impact on daily life and the operative group showed significant faster recovery. Nowadays, intelligent office technology has reduced reliance on the shoulder, allowing most patients with mildly limited shoulder motion to be competent for work tasks, but this seemed still difficult for conservative patients. The shorter gap between injury and returning to work give the patients competitive edge in this highly efficient society. Our study showed that the main challenge in regaining ROM was supination, and the reasons differed between the two groups. Non-operative patients experienced shoulder constraint, likely due to the shortening of the affected clavicle, while operative patients could not identify the reason and often attributed it to the plate, even though the hardware was not prominent. According to our investigation, patients faced difficulties in strength training were primarily concerned about the risk of a second fracture (non-operative patients) or plate breakage (operative patients). We suppose that difference in time required for recovery was due to the longer immobilization and severe pain in early stage for non-operative patients and shoulder stiffness thus caused.