## 4 Discussion  
Fixation stability is one of the important concerns for bone fracture treatment [30]. In fact, the bone healing time is strongly influenced by the fixation stability [31]. In the present study, the maximum displacement of the clavicle treatments was used to evaluate their fixation stability. The numerical approach showed that the plate fixation techniques demonstrate a better fixation stability than the nail fixation technique. This finding was validated by [PERSON] et al. [29], who concluded that the TEN provides less stability compared to a reconstruction plate for the treatment of simple displaced fractures of the midshaft clavicle. In addition, [PERSON] et al. [14] also found that the patients in the plate-fixation group recovered faster than the patients in the intramedullary nailing group during the first six months after surgery. Therefore, when considering the fixation stability, the present study suggests the use of a plate fixation for the treatment of a middle-third clavicle fracture. More specifically, both the ACP and CAS can provide the required fixation stability as compared to the SCP and TEN. A fixation strategy with a better fixation stability has smaller displacement, larger rigidity, and higher stiffness. The correlation study (Figure 7A-D) showed that a negative correlation was found between the past studies and the present study. Those results supported the feasibility of the simplified single-clavicle models and the complete human upper-body skeleton models (Figure 7E,F). A peri-implant fracture is one possible complication of a clavicle treatment [9; 32]. Peri-implant stress has been applied to investigate the risk of a peri-implant fracture [16; 28; 33]. In the present research, the maximum von Mises stress of the clavicle bone was calculated. The results showed that all plate fixations demonstrated a higher clavicle bone stress compared to the nail fixation. This finding is inconsistent with the results by [PERSON] et al. [34], who found that the locking plate fixation shows lower bone stress than that of the Sonoma intramedullary nail and Rockwood clavicle pin. The inconsistency between these studies is due to an assumption of the locking screw geometry. [PERSON] et al. modeled the locking screws as 3.5-mm diameter solid cylinders. However, the present study considered locking screws with a real thread geometry. This means that the threads of the locking screws can cut into the clavicle bone and create a stress riser effect in the bone. In addition to the fixation stability and a peri-implant fracture, an implant failure is another important issue regarding a clavicle fracture fixation [6; 8; 35]. In the present study, the maximum von Mises stress of the fixation devices was calculated. The results show that the implant stress of the SCP is higher than that of the ACP in a single-clavicle model under bending and combined loads. This result was verified by [PERSON] et al. [23], who constructed a superior plate, an anterior plate, and a spiral plate with identical cross-sectional features, and found that the implant stress of the superior clavicle plate was higher than that of the anterior clavicle plate. This means that the stress of a clavicle plate is affected significantly by the different fixation positions. However, the stress of a spiral clavicle plate was shown by [PERSON] et al. to be higher than that of an anterior clavicle plate. Their results are inconsistent with the present study, however, in that the CAS has a lower implant stress compared with the ACP, which occurs because [PERSON] et al. constructed all clavicle plates with identical cross-sectional features, whereas the present study did not control for this factor. Although an inconsistency between these two studies was found, an important fact was deduced, namely, increasing the number of locking screws for a spiral clavicle plate can reduce the implant stress and may also decrease the risk of an implant failure.