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A 30-year-old soccer player presents with a painful left ankle
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A 30-year-old man sustained a twisting injury to his left ankle while playing soccer and had immediate pain and deformity. He was diagnosed with a fracture-dislocation of the left ankle by the emergency department physician, and a closed reduction was attempted under conscious sedation. Post-reduction X-rays showed persistent deformity with the talus posteriorly dislocated (Figure 1).
The orthopedic department was consulted, and the patient underwent another attempted reduction, with subsequent improvement of the tibiotalar joint (Figure 2). Post-reduction, the patient developed decreased sensation to his great, second and third toes, and was noted to have persistent posterior displacement of the fibula.
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Anteroposterior (a), mortise (b) and lateral (c) views of left ankle after the first attempt at closed reduction are shown. In Figure 1b, the “axilla sign” is present, represented by the arrow.
Images: Lieder C and colleagues
Anteroposterior (a) and lateral (b) of left ankle after the second attempt at closed reduction is shown.
Bosworth fracture
The patient had undergone two reductions that were unsuccessful in reducing the fracture-dislocation of the left ankle. This was due to the fibula fixed behind the posterior tibia, which resulted in two unsuccessful closed reduction attempts (Figure 3).
CT of left ankle demonstrates the fibula trapped behind the posterior tibial tubercle (a and b).
Background and work-up
First described by Bosworth in 1947, the Bosworth ankle fracture-dislocation is characterized by a fracture of the distal fibula with a fixed dislocation of the proximal fibula fragment posterior to the posterior tibial tubercle. The injury is rare, with approximately 60 cases reported in the literature from 1947 to 2011 and 15 cases reported from 2000 to 2012. Variants with an intact fibula may occur, and associated injuries may include ruptured deltoid ligaments, fractures of the medial malleolus or posterior tibial tubercle, compartment syndrome and vascular injuries. A common mechanism has been proposed, involving a significant external rotation force applied to the supinated foot. Using a biomechanical cadaver model, Perry and colleagues demonstrated that the tibiofibular ligaments fail first, followed by the anteromedial capsule, and then the interosseous ligament. With further external rotation, the fibula is pulled posteriorly by an intact lateral ankle ligament complex and is trapped behind the posterolateral ridge of the tibia. In 88% of cases, a Weber-B fibula fracture is observed; however, occasionally Weber C fractures or isolated fibular dislocations with no fracture are witnessed. Given the energy required for this injury, Bosworth fracture-dislocations are usually accompanied by a medial-sided injury involving either the medial malleolus or deltoid ligament.
A high index of suspicion is critical for diagnosing a Bosworth fracture-dislocation, as this diagnosis is commonly missed. History should focus on the mechanism of injury, energy of trauma, and any associated neurovascular symptoms. Beekman discussed, although rare, how a Bosworth fracture went on to a four-compartment fasciotomy. On examination of the patient with a Bosworth fracture-dislocation, one typically witnesses a marked external rotation deformity of the foot. Examination should also involve careful assessment of the patient’s compartments, as there are multiple reports in the literature of compartment syndrome in association with the Bosworth fracture-dislocation. In addition to standard ankle radiographs, full-length knee-to-ankle films should be obtained. Khan and Borton identified the “Axilla sign,” an en face view of the axilla between the anterior and posterior tibial colliculi on AP radiograph, as a hallmark of these injuries (Figure 1B). This finding is seen because the posteriorly dislocated fibula locks the tibia in internal rotation, producing a lateral view of the distal tibia when the ankle is positioned for a typical AP radiograph. This is further demonstrated with full-length knee-to-ankle radiographs, which may concurrently show an anteroposterior view of the knee and lateral view of the talus. If uncertainty of the diagnosis persists following plain radiographs, a CT scan should be obtained, as this will clearly demonstrate the posteriorly dislocated fibula and, in some cases, associated fracture of the posterior malleolus. Wright and Davies recommend routine CT scans for Bosworth fractures for visualizing the fracture pattern and surgical planning.
This intraoperative photo of the left ankle shows the proximal aspect of the fibula fracture is trapped posterior to the tibia.
Treatment options
Although rare cases of successful closed reduction have been reported, closed reduction of a Bosworth fracture-dislocation is challenging and often impossible (>70% of cases) due to the presence of an intact interosseous membrane and entrapment of the distal fibula behind the posterior tibial tubercle (Figure 4). If closed reduction is successful, patients may be treated with delayed open reduction and internal fixation. However, in most cases, early open reduction and internal fixation, within a few hours of injury, minimizes soft-tissue trauma and obviates the need for repeated closed reduction attempts. The lateral ankle is generally approached first. Using an elevator, the fibula can usually be easily levered into its normal position using the tibia as a fulcrum. Another technique involves disimpacting the fibula from the posterior tibia with reduction forceps for added control of the fibula. The lateral malleolus is fixed in the standard fashion with either a lag screw and neutralization plate or posterior antiglide plate. Similarly, the syndesmosis and medial malleolus are assessed intraoperatively and are also managed according to surgeon preference. Syndesmotic fixation is almost universally required, as most syndesmotic ligaments must fail prior to fibular dislocation.
Management of our patient
Postoperative AP and lateral X-rays of the patient’s left ankle demonstrate satisfactory reduction of the Bosworth fracture.
After failure of two attempts at reduction in the emergency department, the decision was made to proceed with urgent open reduction in the OR. Preoperatively, the patient’s foot was also noted to be cool and pulseless, and an emergent CT angiogram of the leg and ankle was performed. This demonstrated tapering of the flow of the anterior tibial, posterior tibial, and peroneal arteries at the distal third of the lower leg, and no visualization of the dorsalis pedis or plantar arteries. The vascular surgery department was consulted, and they recommended urgent open reduction with re-assessment of vascular status, as the vessels were thought to be compressed by the displacement of the fracture and in spasm rather than ruptured.
The patient was administered general anesthesia, positioned supine, and a standard lateral approach to the fibula was used. The fibula was completely displaced posteriorly. A medial incision was also utilized to clean fragments from a small chip fracture of the medial malleolus from the medial gutter. During the initial exposure, the anterior ankle capsule and soft tissues were noted to be completely stripped from the anterior tibia. Once the fracture was adequately exposed and debrided, the fibula was disimpacted from the posterior tibia and reduced. This was accomplished with the use of reduction forceps to control the fibula while flexing the knee to relax the gastrocnemius.
Intraoperative mortise view of the left ankle demonstrates reduction of the fibula fracture and restoration of the ankle mortise.
Once disimpacted, the remaining reduction and fixation of the fibula was similar to a routine acute supination-external rotation injury. A small area of compressed anterior fibular cortex was noted that did not prevent anatomic reduction of the primary fracture. A 2.7-mm lag screw was used in addition to an eight-hole one-third-tubular neutralization plate for fixation of the fibula. The syndesmosis was reduced under direct visualization with fluoroscopic assistance and fixated with two quadricortical 4-mm screws. The incisions were closed, and the patient was found to have intact dorsalis pedis and posterior tibial Doppler signals. The patient was placed in a post-mold splint and admitted to the hospital for neurovascular and compartment checks. His postoperative neurologic exam demonstrated continued grossly decreased sensation over the dorsal and plantar aspects of the foot, but intact motor function of tibialis anterior, extensor hallucis longus and flexor hallucis longus. The patient was discharged home on postoperative day 2 with a stable neurovascular exam. Postoperative AP and lateral X-rays of the patient’s left ankle demonstrate satisfactory reduction of the Bosworth fracture.
At the 2-week postoperative visit, the patient was converted to a short-leg cast after removal of his sutures and splint. He reported some improvement of the diminished sensation and paresthesia over the medial aspect of the plantar surface and the dorsum of the foot. By 10 weeks, a palpable dorsalis pedis pulse was present, but he reported only slight improvement in his sensation. Radiographs demonstrated excellent bony alignment and healing. He was converted to a CAM walker boot to begin ankle range of motion exercises; however, he was told to remain non-weight bearing.
At 14-weeks postoperatively, the patient’s ankle range of motion was limited to 10° of dorsiflexion and 20° of plantar flexion. He continued to have diminished sensation to the dorsum of the foot. The patient had weakness of his extensor hallucis longus and had developed a flexion contracture of the great toe; therefore, he was sent for physical therapy and an EMG but he refused the test. He was advanced to full weight-bearing in the boot.
Between 14 weeks and 9 months, the patient experienced some improvement in his sensation and motion. He continued to work with physical therapy. Despite two treatments with injections of botulinum toxin to his flexor hallucis longus, the flexion deformity of the great toe persisted. At 11-months postoperatively, the patient reported restoration of sensation in his foot. Despite continued great toe deformity, he was asymptomatic and declined further intervention. The patient was told he could follow up on an as needed basis.
References:
Bartonícek J. J Orthop Trauma. 2007;doi:10.1097/BOT.0b013e31815affb7.
Bosworth DM. J Bone Joint Surg.1947;29(1):130-135.
Perry CR. J Bone Joint Surg.1983;65(8):1149-1157.
Khan F. Foot & Ankle International. 2008;doi:10.3113/FAI.2008.0055.
Szalay MD. J Orthop Trauma. 2001;15(4):301-303.
Wright SE. Injury. 2012;doi:10.1016/j.injury.2011.09.017.
Yeoh CS. J Orthop Surg (Hong Kong). 2013;21(2):249-252.
For more information:
Charles Lieder, DO, can be reached at Department of Orthopaedics, 1969 W. Ogden Ave., Chicago, IL 60612; email: charlie.lieder@gmail.com.
Andrew Riff, MD, can be reached at 1611 W. Harrison St. #400, Chicago, IL 60612; email: ariff8@gmail.com.
Patrick Johnston, DO, can be reached at email: cyyclist@gmail.com.
Jan P. Szatkowski, MD, can be reached at Orthopaedic Trauma & Fracture Care, Andrews Institute for Orthopaedics & Sports Medicine, 1717 North E St., Suite 208, Pensacola, FL 32501; email: szatkowski@gmail.com.
Disclosures: Lieder, Riff, Johnston and Szatkowski have no relevant financial disclosures.