1. Dr. Daniel T. DeGenova – Doctors Hospital Orthopedic Surgery Program
2. Dr. Hunter F. Pharis – Doctors Hospital Orthopedic Surgery Program
3. Dr. John B. Schrock – Doctors Hospital Orthopedic Surgery Program
4. Dr. Iou-Ren E. Chang – Doctors Hospital Orthopedic Surgery Program
5. Dr. J. Tucker Peabody – Doctors Hospital Orthopedic Surgery Program
6. Dr. Jignesh N. Patel – Doctors Hospital Orthopedic Surgery Program
7. Dr. Benjamin C. Taylor – OhioHealth Orthopedic Trauma and Reconstructive Surgeons

Authors
Daniel T. DeGenova, DO^1A, Hunter F. Pharis, DO¹, John B. Schrock, DO¹, Iou-Ren E. Chang, DO¹, J. Tucker Peabody, DO¹, Jignesh N. Patel, DO¹, Benjamin C. Taylor, MD²

1. OhioHealth, Department of Orthopedics, Columbus, OH 43228, United States
2. OhioHealth Orthopedic Trauma and Reconstructive Surgeons, Grant Medical Center, Columbus, OH 43215, United States

A. Corresponding author at: OhioHealth/Doctors Hospital, 5100 West Broad Street, Columbus, OH 43228, United States. E-mail address: [email protected] (D. T. DeGenova).

Abstract

Case
Bosworth fracture-dislocation of the ankle is a rare injury that is often irreducible. These injuries are defined by fibula fragment entrapment behind the posterior tubercle of the distal tibia. They typically occur with complete deltoid ligament injury or medial malleolus fracture. We describe the case of a 49-year-old female who sustained a Bosworth injury with partial deltoid ligament injury that was treated with open reduction internal fixation, deltoid ligament repair, and syndesmotic screw fixation.

Conclusion
We recommend open reduction and internal fixation along with repair of the deltoid ligamentous complex in patients who sustain Bosworth ankle fracture-dislocation injuries.

Keywords: Bosworth, Ankle Fracture, ORIF

Introduction
Ankle fractures are a common presentation of orthopedic trauma with a reported incidence of up to 174 per 100,000 per year in adults (1). Treatment of ankle fractures is often open reduction and internal fixation (2,3). Despite the frequency of this injury, rare variants exist that change perioperative management and surgical planning. One example of this is in the case of elderly fragility fractures (4). Another example of such is the Bosworth fracture. This is a rare fracture-dislocation of the ankle caused by external rotation of a supinated foot, where the proximal part of the fibula fracture becomes trapped behind the posterior tubercle of the distal tibia (5,6). It is reported that this specific variant occurs in 1.62% of all ankle fractures (7).

In the case of a Bosworth fracture, it is common for several different injuries to accompany the fracture, including injury to the deltoid ligament or medial malleolus as well as injury to the syndesmosis (5,6,8,9). To our knowledge there are currently no reports describing a partial tear of the deltoid ligament in adults in the setting of a Bosworth fracture-dislocation. The purpose of this case report is to describe a case of Bosworth ankle fracture-dislocation with partial deltoid injury in an adult treated with open reduction internal fixation and syndesmosis fixation. Exemption from the institutional review board was received from our institution for the submission of this manuscript.

Case Report
A 49-year-old female with past medical history of controlled diabetes mellitus type 2 with oral medication and hypertension presented to the emergency department with left ankle pain after fall while riding a bicycle. Physical examination revealed intact skin and obvious deformity to the left ankle with a grossly intact neurocirculatory examination.

Imaging in the emergency department demonstrated a trimalleolar-equivalent ankle fracture with tibiotalar dislocation (Figure 1). During attempted reduction in the emergency department, it was noted that the fibula was dislocated behind the tibia (Figure 2). A decision was made to undergo open reduction and internal fixation of the right ankle.

Surgical Procedure
The patient was brought to the operating room and positioned in the supine position. A standard lateral approach to the distal fibula was used. The lateral malleolus fracture was reduced, and a 2.7 mm DePuy Synthes (Raynham, MA) distal fibula locking plate was placed. Attention was then turned to the medial side of the ankle where a standard approach was performed. Upon observation of the deltoid ligament, there appeared to be a partial tearing of the ligament. A 2.9 mm Zimmer-Biomet Juggerknot (Warsaw, IN) suture anchor was used to repair the deltoid ligament. An external rotation stress test intraoperatively demonstrated syndesmotic instability. A single DePuy Synthes FibuLink (Raynham, MA) was placed. The patient was placed into a trilaminar splint and there were no perioperative complications.

Postoperative Course
The patient was made non-weight bearing in a splint for six weeks. At the six week follow up visit, the patient was transitioned to a walking boot and allowed to be weight bearing as tolerated. At the three-month follow up, patient was transitioned to an ankle brace. Imaging at three month follow up demonstrated maintained reduction with well approximated fracture cortices, bony callous formation, and no widening of the medial clear space. At one year of follow up, the patient was back to all previous activities with minimal pain. Radiographs demonstrated union of the fracture with intact hardware in no obvious complications (Figure 3).

Discussion
In this case report, a Bosworth-ankle fracture with partial deltoid injury was fixed utilizing a lateral locking plate with syndesmotic fixation and repair of the partial deltoid injury. In a case series of Bosworth injuries by Bartonicek et al., five of six injuries had associated medial malleolus fractures or complete deltoid ligament disruption (5). Injury to the syndesmosis in these fractures is also common and has been reported in several case studies (6,7,10,11).

Perry et al. demonstrated the mechanism of Bosworth fractures using cadaveric specimens in 1983, following the methods described by Lauge-Hanson (6). The authors determined that Bosworth fractures occur due to an external rotation force on a supinated foot (6). The order of injury was anteromedial capsule first, followed by interosseous ligament. With further external rotation, the fibula is pulled posteriorly behind the posterolateral ridge of the tibia and then fractured. Lastly, the medial malleolus or deltoid ligament is disrupted (6). In the case we present, the fibula was fractured, and the deltoid was partially disrupted. This coincides with the staging of injury proposed by Perry et al., as further external rotation force would have likely disrupted the medial malleolus or deltoid ligament as the final stage of injury (6). 

There are several case studies that report various rates of medial malleolus fracture or complete deltoid ligament rupture; however, there are no reports of partial deltoid tears. A review by Won et al. reported deltoid ligament injury in 31/80 cases; however, no study has advocated to routinely examine the deltoid ligament if there is stability with syndesmotic fixation (7,10). In our case, the preoperative radiographs with medial clear space widening prompted the investigation of the deltoid ligament through a medial approach to the ankle. Upon observation of the partial tear, ligamentous repair was performed with a suture anchor before the external rotation stress test and syndesmotic fixation.

Closed reduction was not obtained in the emergency department in this case. Most sources describe these injuries as being irreducible in the adult patient population (5,8,9). Most commonly, successful closed reduction has been described in injuries in adolescents (12-14). Fan et al. describe the successful closed reduction of a Bosworth ankle fracture-dislocation in an adult by placing one hand along the posterior medial surface of the fibular shaft and applying a lateral and anterior force while a second hand applied medial counter force along the tibial shaft (15). An additional set of hands applied traction to the dorsiflexed foot. After successful reduction, the patient was able to be sent home and return for open reduction and internal fixation at a later date. 

In the setting of an irreducible ankle fracture, open reduction and internal fixation in the acute setting allows the pressures to be relived from the soft tissues surrounding the injury thus preventing breakdown and allowing for better healing potential. A study by Won et al. examined 51 cases of irreducible Bosworth fracture dislocations (7). In this group, 36 patients received surgery within 24 hours of admission, while 15 patients had a delayed surgery. The patients with delayed surgical intervention had significantly worse outcome measures including length of stay, acute and chronic complications, and two patients that developed compartment syndrome requiring fasciectomy (7). 

Postoperative management of these injuries follows similar protocols as that of other ankle fractures. After open reduction and internal fixation, our patient was made non-weight bearing in a splint for six weeks followed by transitions to a walking boot and ankle brace thereafter. Bosworth fractures in adults have been reported to have higher overall complication rates than other reducible forms of ankle fractures (7,10,16). Complications can include compartment syndrome, post-traumatic arthritis, and avascular necrosis of the talus (7,10). Our patient had an excellent outcome with radiographic evidence of fracture union at one year with intact hardware. In follow up visits, there was no evidence of medial clear space widening pointing to competence of the repaired deltoid ligament. The patient had minimal pain and had resumed all previous activities.

Conclusion
Bosworth ankle-fracture dislocations are uncommon injuries that infrequently occur without a complete injury to the deltoid ligament or medial malleolus. In this case, a Bosworth type injury occurred with partial deltoid ligament injury. Open reduction and internal fixation with partial deltoid repair was used as a treatment option with an excellent outcome.

Figure 1 | Figure 2 | Figure 3

Figure Legends
Figure 1. Anteroposterior and lateral radiographs of a left ankle demonstrating a Bosworth ankle fracture dislocation.

Figure 2. Post reduction lateral radiograph and axial computerized tomography scan demonstrating posterior dislocation of the fibula from the distal tibial incisura.

Figure 3. Final anteroposterior and lateral radiographs of a left ankle demonstrating union of the fracture with intact orthopedic hardware. 

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