Application of an interlocking nail in comminuted fractures of the femoral shaft is challenging for orthopedic surgeons. The far displaced fragments make closed reduction impossible, even if a percutaneus wire passer or bone hook is used through a mini-open incision. Thus, open cerclage wiring is the preferred method for achieving and maintaining the reduction for further reaming and nail application. However, open cerclage wires involve the risk of disruption of soft tissue and periosteal blood flow. This study aimed to identify the roles of augmented cerclage wires used in patients with comminuted fractures of the femoral shaft treated with intramedullary nails, especially the timing, effect, and drawbacks.
The first result of the study is that augmented open cerclage wires are usually used in severe comminuted fractures and they effectively reduce the fractures. Thus, cerclage wires could be used not only for reducing long spiral and torsional fractures [22–23] but also for effectively treating severe comminuted fractures with far displaced fragments (Fig. 2). Moreover, Scharf et al.  proved that fixation stability was superior with a combination of cerclage wiring and interlocking nailing in a femur model. Therefore, cerclage wiring could both simplify the surgery and improve the stability of fixation.
The second result is that the open cerclage wiring technique would not decrease the union rate and union time in comminuted femoral shaft fractures. In the past, open cerclage wiring was criticized for extensively dissecting the soft tissue while approaching the fracture site; thus, it is a dilemma whether to preserve the soft tissue or to obtain improved reduction. However, the literature [25–27] has failed to document the significant difference between open and closed nailing for femoral shaft fractures. Furthermore, by using the directly open approach, surgeons could see the fracture line directly to bring the fragments together and to achieve anatomic reduction with less fluoroscopy exposure . The presented results suggest that open nailing to comminuted femoral shaft fractures would not disturb callus formation and bone healing.
The other concern with using the open cerclage wire technique is the risk of blood supply disruption by cerclage wires. Blood supply may be disrupted through the strangulation of blood vessels [28–29] and the contact between cerclage and the bone surface. The risk of vascular injury due to the cerclage passer was 1.59% in proximal femur shaft fractures and 7.14% in distal femur shaft fractures. However, previously reported cases of vascular injury mostly occurred due to the percutaneous cerclage wiring technique. With the percutaneous technique, it is difficult to ensure that the cerclage passer is passed extremely subperiosteally and the vessel is outside the cerclage loop. However, by using the open wiring technique, surgeons were able to ensure the wire is placed subperiosteally and thus prevent the strangulation of the vessel.
Furthermore, the contact between the cerclage wire and bone surface impedes blood supply, especially when the endosteal blood supply might have been disrupted by reaming and application of interlocking nails. However, the histologic and anatomical study of femoral vascularity by Pazzaglia et al. suggested that the periosteal vascular supply is circumferential, rather than longitudinal, with multiple musculo-periosteal vessels nourishing the periosteal layer. Moreover, Apivatthakakul et al. and Kennedy et al. proved that cerclage wiring resulted in minimal disruption of the femoral blood supply despite the location of the cerclage wire and the distance between the wire loops.
Moreover, our results implied that the cerclage wire is beneficial in severe comminuted fractures of the femoral shaft. Lin et al. and Lee et al. observed that the large fragment size and great distance of fragment displacement in comminuted femoral shaft fractures were associated with nonunion. In our study, the Wire group had significantly larger fragment sizes and greater distance of fragment displacement than the No wire group; thus, it theoretically had an inferior union rate. However, these two groups showed a similar union rate. The benefit of anatomic reduction and augmented fixation seems to overcome the extensive soft tissue and periosteal blood disruption. Although this is not a reasonable statistical analysis, it suggests that the cerclage wire is safe and might be beneficial.
Regarding the final result of the study, we failed to identify risk factors for nonunion, including smoking, BMI, and preoperative and postoperative fragment number and displacement. The risk factor for nonunion in femoral shaft fracture treatment with interlocking nail remains controversial. Taitsman et al.  found that open fracture, tobacco use, and delayed weight bearing are risk factors for femoral nonunion. By contrast, Metsemakers et al. , Lin et al. , and Lee et al.  documented that the severity of the fracture comminution, including AO/OTA classification and preoperative displacement of the fragment, is the only risk factor for nonunion. Therefore, the eligible fractures in our study were all comminuted (AO/OTA 32B/32C) and theoretically had more displacement of the fragment. This can explain the reason that the union rate (65%) in our study was lower than that reported previously . Moreover, no significant difference was observed between union rate and preoperative size and displacement of the fragment. This might be explained by the decreasing fracture gaps after cerclage wiring, and thus improving fracture healing.
This study had some limitations. First, we attempted to obtain samples with similar fracture patterns in the two groups by excluding simple fractures, but we failed. Thus, we were unable to obtain an objective conclusion from the presented results. Second, data were collected retrospectively, where surgeries were performed by different surgeons. Individual surgeons may follow different indications for the use of interlocking nailing or plating, mini-open reduction or closed reduction, and lateral decubitus position or supine position on fractures when in the operating room. The postoperative rehabilitation programs of different surgeons were slightly different, which may have affected the study outcomes, particularly for fixation failure. We identified some possible confounding variables, such as fracture classification. However, some related factors that could not be controlled for, such as bone quality or patient compliance, may have had an influence. Third, this study primarily focused on radiologic results and a simple review of medical records. Further investigation is required, and precise measurements of functional results, such as range of motion, knee score, or an injury-specific questionnaire, should be used in future research.
In conclusion, an augmented open cerclage wire is indicated in comminuted fractures of the femoral shaft treated with intramedullary nails even when the fragments are large or far displaced. By using the open cerclage wiring technique, fractures could be reduced better without decreasing the union rate. We advocate that augmented open cerclage wiring is safe in treating comminuted femoral shaft fractures with interlocking nails.