1、Rare and high misdiagnosis ratio
Bosworth fracture-dislocation is rare in the clinic, with few and insidious imaging features which poses challenges to even senior doctors when making an immediate diagnosis. Cho et al.5 sampled 15 cases with Bosworth fracture-dislocation, while only 5 patients were diagnosed with Bosworth fracture-dislocation according to the initial imaging examination. The primary diagnosis rate was 33.3%. Yougun et al.2 retrospectively analyzed 51 patients with Bosworth fracture-dislocation in 4 university hospitals. According to statistical analysis, 22 patients were not diagnosed with Bosworth fracture-dislocation before surgery; 10 of them were diagnosed with Bosworth fracture-dislocation during surgery. Twelve patients failed to receive a diagnosis, and the initial diagnostic rate was 43.1%. Consequently, the primary diagnosis rate of Bosworth fracture-dislocation is low, and the clinical misdiagnosis rate is high.
Improving the efficiency of clinical diagnosis is a top priority, and one needs to understand the injury mechanism of Bosworth fracture-dislocation. Schatzker et al6 believed that the mechanism of injury is a posterior lateral dislocation of the talus, which leads to an injury of the lower tibiofibular ligament and results in a fibula fracture followed by further external rotation of the talus. Currently, most scholars agree that the mechanism of injury is external rotation, which corresponds with the Maisonneuve mechanism of injury. On this basis, Bosworth injury will occur after suffering from a strong continued external rotation.7 The characteristic indication can be divided into two points: 1. The ankle joint is in extreme external rotation; 2. Manipulative reduction is difficult.
X-ray imaging has many typical features for the diagnosis of Bosworth fracture-dislocation, including the Axilla sign on the mortise view, posterior dislocation of the talus on the lateral view, and the distance between fibula and talus on the external oblique view.8–10 The Axilla sign is mainly due to the continuous internal rotation of the tibia, and the axilla of the medial tibial plate can be seen on the X-ray. The mortise view of the ankle is a 15-25-degree internal rotation projection position. Clinically, due to the patient's pain, it is often impossible to obtain a standard projection position. Incarceration of the tibial tendon and fragments also appears an axilla syndrome. Khan et al.10 retrospectively analyzed 10 patients with Bosworth fracture-dislocation. X-ray imaging revealed an axilla sign. Therefore, the axilla sign cannot be used as a diagnostic criterion, but it has high sensitivity and specificity for predicting Bosworth fracture-dislocation.
On the lateral radiograph of Bosworth fracture-dislocation, the posterior dislocation of the talus can be clearly observed. For general ankle fractures and dislocations, manual reduction is usually effective. In Bosworth fracture-dislocation, it is difficult to reset the fracture and dislocation because of the incarceration, which leads to separation after restoration, and this is similar to the key sign of acromioclavicular joint dislocation.
External oblique X-rays show that the fibula is located in the middle of the talus. Kyu et al.8 divided the talus into two parts on the external oblique view. With the fibula as the boundary, the anterior part was α, and the posterior part was β. α/(α + β) was used to judge the Bosworth fracture and dislocation. As a result of the location of the fibula in the middle of the talus on the external oblique view, α/(α + β) is close to 0.5. Therefore, the position or measurement of the fibula relative to the talus on the lateral oblique film is the favorable evidence for diagnosis.
The characteristic indicators are concealed due to severe pain and lack of an X-ray in the standard position, although X-ray has more imaging features, Therefore, for suspected patients, CT and three-dimensional reconstruction are recommended. Not only can a clear diagnosis be made as early as possible, but it can also reduce the risk of further injury and complications, and it can lead to effective diagnosis and early treatment.
2、Difficulty in manipulative reduction
The reduction of Bosworth fracture-dislocation is difficult, which is why it is called an irreversible ankle fracture dislocation.11 Cho et al.5 collected data on about 15 patients with Bosworth fracture-dislocation. The average number of manual restorations was 2.24, and only 1 case was successfully reset by manual restoration. Jan et al.12 analyzed 88 cases from the literature, and only 5 patients were successfully reset by manual manipulation. A total of 6 cases have reported to our hospital since 2011, and only 1 case underwent successful repair with plaster fixation. In this case, the tibiotalar joint was closed during the surgery, and there was an obvious sound which indicated that the tibiotalar joint has been successfully reset. However, the proximal fibula fracture is still inserted in the fractured end of the posterior malleolus. The tibia can dislocate again due to the fracture at the distal fibula, just like the acromioclavicular key sign. The key to intraoperative reduction is to resolve the incarceration of the fibula. First of all, surgical treatment will reset the fibula fracture. Afterwards the posterior malleolus fracture, the medial malleolus fracture, the lower tibiofibular joint, and the medial collateral ligament are resolved.13
For Bosworth fracture-dislocation, it is generally recommended to adopt the posterolateral approach to the ankle joint, which can fully expose the lateral ankle fracture and resolve the posterior ankle fracture. If only the posterolateral approach is selected, the prone position can be used routinely. If accompanied by a fracture of the medial malleolus, floating positions are generally used. In cases where patients fall sideways, patients are positioned on the healthy side, and the back of the buttocks is fixed with baffles. The posterolateral approach was used to deal with the lateral malleolus and posterior malleolus fracture, and the posterior baffle is removed for supine positioning to treat a medial malleolus fracture. Since there was no medial malleolus fracture, the prone position was selected. After intraoperative reduction and the fixation, conventional C-arm fluoroscopy was performed. The intraoperative ankle radiographs showed that the ankle points were in place, the inferior tibia and fibula were in place, and the fracture ends were in good alignment. The intraoperative lateral radiograph only indicated that the anterior space of the ankle was too large because the standard lateral radiograph could not be taken. Considering the rupture of the joint capsule and ligament, the first surgery was unsuccessful. In the second surgery, the floating position and the posterolateral approach were used to reset the fibular fracture in front of the peroneus longus and brevis, which could fully expose the fractured end and the inferior tibiofibular joint. In addition, the floating position can be used to routinely photograph the lateral ankle joint, which is more conducive in deciding on reduction. Another advantage is that the floating position can simultaneously handle medial malleolus fractures, saving time in secondary disinfection and other surgeries. Therefore, it is suggested that the floating position and the posterolateral approach should be adopted to avoid the failure of surgical reduction and expose the posterior ankle fracture in the gap between the peroneus longus muscle and flexor pollicis longus.
Compared with conventional ankle fracture and dislocation, the incidence of complications in Bosworth fracture-dislocation is high including skin necrosis, wound infection, osteofascial compartment syndrome, traumatic arthritis, talus necrosis, and joint stiffness.7,12,14−18 In addition, Bosworth fracture-dislocation is often accompanied by severe soft tissue injuries, and improper manipulative reduction can also aggravate the injury.2 Won et al.2 retrospectively analyzed 51 patients with Bosworth fracture-dislocation including 36 emergency surgeries and 15 delayed surgeries. After 1 year of follow-up, it was found that the American Orthopedic foot and ankle society (AOFAS) score of emergency surgery patients was significantly higher than that of delayed surgery patients. Besides, swelling in patients with delayed surgery had not improved significantly, and the complications of nonunion and osteoarthritis were significantly higher than patients who had emergency surgery. Cho et al.5 conducted a follow-up study on 16 patients and found that the prognosis of patients undergoing one or two closed reductions was significantly better than that of patients with three or more closed reductions, and the prognosis of patients who undergo surgery within 24 hours after injury was obviously better. In conclusion, early diagnosis and reduction of Bosworth fracture-dislocation can significantly reduce complications.19–21 Most scholars2,12,20,21 suggested that early open reduction and internal fixation is the first choice due to the difficulty associated with manual reduction.