Bosworth ankle fracture-dislocation: current concept review

Abstract

• Bosworth fracture (BF) is a special type of locked ankle fracture-dislocation, characterized by displacement of a fragment of the fractured fibula from the fibular notch behind the posterior surface of the distal tibia.

• BF is a complex injury affecting multiple structures of the ankle joint, which is still frequently misjudged even today, potentially leading to severe complications.

• CT examination, including 3D reconstructions, should be the diagnostic standard in BF, as it provides a complete picture of the fracture pathoanatomy, most prominently the morphology of the frequently associated posterior malleolar fracture.

• BF requires early reduction of the displaced fibular fragment without repeated attempts on closed reduction. Non-operative treatment of BF almost always fails. The standard treatment procedure is early open reduction internal fixation.

• Due to the relative severity and paucity of the injury, BF seems to be particularly prone to soft tissue complications, including compartment syndrome.

• The results of operative treatment are mixed. Many studies report persistent pain even after a short time interval, with limitations of the range of motion or even stiffness of the ankle joint, and development of degenerative changes. Larger studies with long-term results are still missing.

Introduction

Bosworth fracture (BF) is a special type of locked ankle fracture-dislocation, characterized by displacement of a fragment of the fractured fibula from the fibular notch (FN) behind the posterior surface of the distal tibia (Fig. 1). The eponym Bosworth fracture refers to David March Bosworth (1897–1979), who, in 1947, described five cases of this injury (1). The term ‘Bosworth fracture’ was initially used by Simonovich (2) in an article written in Spanish. In the English literature, it was mentioned for the first time by Mayer (3) in 1978. BF presents a rare but severe injury that is still frequently misjudged even today, potentially leading to severe complications (4). The aim of the following review is to raise awareness of this injury and its potential complications.

Figure 1.

Typical Bosworth fracture on 3D CT reconstructions. With a Weber type B fibular fracture, the proximal fibular fragment is entrapped behind the distal tibia. In this particular case, it is locked between distal tibia and fractured posterior malleolus.

Definition

Bosworth originally described a fracture-dislocation of the ankle with the fibular fracture starting at the level of the joint line, i.e. Weber type B, and the proximal fibular fragment locked behind the posterior aspect of the tibia (1). Hamilton (5), in 1984, published a BF case with a fracture of the fibula between its proximal and middle thirds, i.e. Weber type C. Chan et al. (6), in 1995, reported a ‘Bosworth dislocation’ associated with a Maisonneuve fracture (MF).

Bartoníček et al. (7), in 2007, analyzed 60 injuries to the ankle with displacement of an intact or fractured fibula from the FN behind the posterior surface of the distal tibia (‘Bosworth lesion’). They identified three basic patterns of this injury. The first, very rare, type affected adolescents with a mean age of 11 years, where displacement of the intact fibula was associated with a Salter–Harris type I physeal injury of the distal tibia. The second type was an isolated posterior dislocation of an intact fibula in young adults with a mean age of 23 years. The third type, a true BF, which is dealt with in the present article, was characterized by a fracture of the fibula and associated injuries to other structures of the ankle. This type was observed in adult patients with a mean age of 41 years.

Until 2014, all BFs were classified as ankle fracture-dislocations (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44). In 2015, Petersen et al. (45) described a ‘Bosworth displacement’ of the fibular fragment in a partial fracture of the tibial pilon (anterior part), while Capuccio et al. (46), in 2017, reported a BF in combination with a partial posteromedial pilon fracture.

Literature review

We conducted an extensive literature review without time or language restrictions using relevant databases and web browsers (PubMed, Scopus, Web of Science, Google Scholar, and Google). We found a total of 179 cases reported in 72 studies dating from 1947 to 2022 (1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73). These studies were published in eight languages by authors from 18 countries. Until 1975, BF cases were reported by North American authors only. The first European BF case was published as late as 1989, and the first Asian BF case in 2001. Since then, the number of recorded BFs has increased considerably, most likely due to an increased awareness of these injuries (4).

Almost all of these studies were case reports with a detailed description, including radiological documentation, which allowed for a critical analysis of each fracture. Two exceptions were Cho et al. (54), who published a summary of outcomes in a series of 15 BFs, with radiological and CT documentation available only in one case, and Won et al. (55), who reported a series of 51 BFs, both in 2019. The latter estimated the incidence at 1.6% of all ankle fractures.

Mechanism of injury

The mechanism of injury was originally described by Bosworth himself (1) in 1947. ‘As the foot twists under the talus, with the leg continuing to push forward and rotate outward, the lateral collateral ligaments draw the intact fibula behind the tibia. Continuation of the force rotating the talus backward and out from its position beneath the tibia causes further force on the lateral collateral ligaments; finally, the fibula is broken off against the posterior tibial border’.

This issue was dealt with in detail by Simonovich (2) in 1975, but his study was ignored by other authors. In the literature, the most frequently cited concept of the BF fracture mechanism was published by Perry et al. (8) in 1983, with external rotation being the prevalent mechanism of injury.

Pathoanatomy

The BF is a complex injury affecting multiple structures of the ankle joint, with the specific common feature being the displacement of the fractured fibula from the FN behind the posterior aspect of the distal tibia.

Fracture of the fibula

A ‘classic’ BF is associated with a Weber type B fracture of the distal fibula (1), with displacement of the proximal fibular fragment from the FN behind the posterior aspect of the distal tibia. This pattern dominates in the literature, occurring in 168 (94%) cases.

A Weber type C fracture of the fibula is observed only rarely in BF. A total of 11 cases (6%) were reported, including four MFs (6, 23, 50, 62), four fractures in the middle third of the fibula (5, 7, 57), and only one fracture involving the distal third of the fibula (40) (Fig. 2). In two cases, the location of the fibular fracture was not specified (54). The case published by Molinari et al. (74) as a BF, documented by a radiograph showing a fracture of the distal third of the fibula (Weber type C), is actually not a BF, but severe dissociation of the tibiofibular mortise (‘logsplitter injury’) (75).

Figure 2.

Atypical Bosworth fracture. With a high fíbular fracture, the distal fibular fragment is entrapped behind the distal tibia. In this case, a subcapital fibular fracture (Maisonneuve fracture) occurred (see Fig. 5 for whole length lower leg radiograph). White arrow, fractured posterior malleolus.

Injuries to medial ankle structures

These injuries include a rupture of the deltoid ligament or a fracture of the medial malleolus, typically bicollicular (8, 50). Rarely, the medial structures remain intact (62).

Fractures of the posterior malleolus and partial tibial pilon fractures

An associated fracture of the posterior distal tibial rim was already mentioned by Bosworth (1), and later dealt with in detail by several other authors (2, 7, 13, 14), prompted recently by CT imaging (59, 76).

The first detailed analysis of the incidence and morphology of posterior malleolus (PM) fractures associated with BF was published by Kostlivý et al. (59) as late as 2020. Among 97 BF cases reported in the literature and documented by radiological findings, they found a PM fracture in 61 of cases (63%). This coincidence is probably even higher as the PM fragment could not always be properly identified due to the quality of the provided radiographs. A precise assessment of the pattern of PM fractures was possible only in 17 cases documented by CT scans. In two cases, dislocation of the fibula behind the posterior tibial rim was associated with extraincisural (Bartoníček–Rammelt type 1) PM fractures and in one case with an undisplaced Bartoníček–Rammelt type 3 (77). Displacement of the fibula between the displaced PM fragment and the tibia was associated with Bartoníček–Rammelt types 2 and 3 PM fractures in 14 cases (Fig. 3). This entrapment was first described by Meyers (13) in 1957. The most frequently observed PM morphology was type 2 of the Bartoníček–Rammelt classification (posterolateral fragment), while type 4 (large triangular PM fracture) was never observed in BF (59).

Figure 3.

Typical radiological characteristics of a Bosworth fracture. Overlap of the distal tibia and proximal fibular fragment in the AP view, posterior subluxation of the talus and tibiofibular diastasis in the lateral view. CT scans verified the diagnosis. Red arrow, proximal fibular fragment; blue arrow, distal fibular fragment; yellow arrow, displaced posterior malleolus.

CT examination showed that in some cases the PM fracture (Bartoníček–Rammelt type 3) extended as far as the anterior colliculus of the medial malleolus, while in other cases, the medial malleolus was fractured as a whole (Fig. 4). According to the definition published by Bartoníček et al. (77), the dividing line between PM fractures and partial posteromedial pilon fractures connects the center of the FN and the intercollicular groove. The first such cases of BF associated with posterior pilon fractures were recorded in 2017 by Capuccio et al. (46) and Bartoníček et al. (50). Another two cases were reported by Ren et al. (56) and one case by Martin-Somoza et al. (63), i.e. a total of five cases were published.

Figure 4.

Posteromedial pilon fracture in a Bosworth fracture. Red arrow, anterior colliculus forming part of the posteromedial partial pilon fragment; white arrow, distal fibular fragment; yellow arrow, Wagstaffe fragment (C and D are adapted with permission from Bartoníček et al. (50)).

Injury to the anterior tibiofibular ligament

Injury to the anterior tibiofibular ligament (ATFL) is a typical component of BF. Only Han et al. (65) reported a BF with an intact ATFL and deltoid ligament but with a ruptured interosseous tibiofibular ligament. Martin-Somoza et al. (63) and Žofka et al. (73), during surgical exploration, observed an intact ATFL, but a ruptured deltoid ligament.

A bony equivalent of ATFL injury is an avulsion or fracture at its insertions. A fracture of the anterolateral distal tibia (Tillaux–Chaput tubercle, anterior malleolus (78)) in BF was reported for the first time by Perry et al. (8) in 1983, and later by other authors (7, 41, 54). Cho et al. (54) found a fractured Tillaux–Chaput tubercle in 20% (3/15) of their patients with BF. A fracture of the Wagstaffe tubercle, i.e. avulsion of the ATFL from the distal fibula, was recorded by Delasota (41), Cho (54), Hoblitzell et al. (18), and He et al. (62).

Other associated injuries

An osteochondral fracture of the talus associated with BF was reported by Lui et al. (33), Schepers et al. (36), and Saraiva et al. (49). Lui et al. (33) noted a concomitant osteochondral fracture of the tibial pilon, and He et al. (62) found osteochondral fragments in the articular cavity. Hoblitzell et al. (18) found a loose intercalary fragment from the PM displaced into the articular cavity. Delasota et al. (41) described the interposition of the extensor hallucis longus and the extensor digitorum longus between the tibia and the fibula.

Clinical examination

Clinical examination in BF is the same as in other ankle fractures and fracture-dislocations. Visual inspection may reveal a marked external rotation and/or posterior dislocation of the foot, with tenting of the skin or open wounds. Of great importance is palpation of the fibula along its whole length, because BF may be associated with a proximal or subcapital fracture of the fibula. It is mandatory to regularly check the soft tissues and neurovascular status of the foot because BF carries an increased risk of neurovascular compromise and the development of a compartment syndrome (CS) (70).

Imaging

The basic radiographic examination of the ankle includes anteroposterior, mortise, and lateral views. When there is a suspected MF, anteroposterior and lateral radiographs of the entire lower leg, including the knee joint, should be added.

In the AP view, a pathognomonic sign of the BF is tibiofibular overlap, primarily in fractures of Weber type B. In the lateral view, specific signs include posterior subluxation of talus, tibiofibular dissociation (the fibula is displaced posteriorly to the tibia), angulation of fibular fragments in Weber type B. An AP radiograph of the whole lower leg, including the knee joint, may in certain BF cases show the foot in a lateral view (Fig. 5). This ‘knee anterior–foot lateral’ sign, however, is not specific for BF.

Figure 5.

“Knee anterior – foot lateral” sign. The knee is seen in an antero-posterior view, the foot in a lateral view. (A)Example of a Weber type B fibular fracture. (B) Example of a Maisonneuve fracture (same patient as in Fig. 2).

Khan et al. (31) described an ‘axilla sign’ in the mortise view, based on only one case of their own and several cases reported in the literature. The relevance of this sign is limited as its evaluation depends on the accuracy of the performed radiograph and cannot be used in the case of a fracture of the medial malleolus.

CT examination, including 3D reconstructions, should be the diagnostic standard in BF, as it provides a complete picture of the pathoanatomy (76). It shows displacement of the fibular fragment from the FN, which is important for confirming the diagnosis of BF, particularly in fibular fractures of Weber type C (62). It also reveals the type of PM fracture, entrapment of the fibular fragment between the posterior tibia and the displaced PM, fracture of the Tillaux–Chaput and/or Wagstaffe tubercle, which is not always visible on plain radiographs (78), osteochondral fractures of the talus, and loose intraarticular fragments (18, 62).

Treatment

The standard treatment procedure is early open reduction and internal fixation. In the majority of patients, BF is markedly displaced, which increases the risk of further damage to the soft tissues and neurovascular complications. If the patient cannot be operated on immediately, it is necessary to reduce the fracture, primarily the displaced fibula back into the FN.

Attempts at closed reduction are, however, mostly unsuccessful. Although radiographs may show an improved position of the subluxed talus with respect to the tibia and the relationship between the talar dome and the medial malleolus, the locked displacement of fibular fragment from the FN and, consequently, the tibiofibular dissociation persists (Fig. 6). This is typically the case in Weber type B fractures (70), where the displaced proximal fibular fragment has no ligamentous connection to the foot. The only option for closed reduction is direct manual pressure on the proximal fibular fragment from behind and simultaneous internal rotation of the foot (3). This procedure was used successfully only by a few authors, in a total of six reported cases (3, 10, 61, 67). On the contrary, Choi et al. (66) and Bartoníček et al. (70) cautioned against repeated reduction attempts that may deteriorate the soft tissue conditions.

Figure 6.

Unsuccessful attempt at closed reduction of a Bosworth fracture. (A) Postinjury radiographs; (B) postreduction radiographs with persisting mild posterior subluxation of the talus and persisting tibiofibular diastasis. White arrow, fractured posterior malleolus (A is adapted with permission from Bartoníček et al. (50)).

In Weber type C fibular fractures, closed reduction with manipulation of the foot is successful more frequently because the entrapped distal fibular fragment is connected to the foot via the talofibular and calcaneofibular ligaments and is, therefore, easier to handle (23).

To avoid additional soft tissue damage, the primary reduction should be preferably performed under general anesthesia and an image intensifier. If closed reduction is impossible, a short posterolateral incision is made by a sharp elevator or a bone hook. When using spinal or regional anesthesia, care must be taken not to overlook the potential development of a CS. Recently, Patel et al. (79) described closed reduction of the fibular fragment with a percutaneous threaded pin.

Operative treatment

With a few exceptions (3, 10, 61, 67), operative treatment is the preferred treatment method for BF. The technique is described in detail in the recent AO Manual of Fracture Management – Foot and Ankle (58).

The surgical procedure depends on the individual pathoanatomy of the fracture. It is mandatory to reduce the entrapped fibular fragment in the first step. In a second step, reduction and fixation of the PM, if indicated, should follow. In general, reduction and fixation are recommended for Bartoníček and Rammelt types 2–4 PM fractures (77) with displacement, intercalary fragment(s), or tibial plafond impaction (80). Reduction and fixation of displaced PM fragments will, in turn, recreate the FN and stabilize the posterior syndesmosis. Reduction of the fibula into the FN and the subsequent reduction and fixation of the fractured PM is preferably performed via the posterolateral approach (Fig. 7).

Figure 7.

Successful reduction of Bosworth fracture from a short posterolateral incision.

Of vital importance is a careful revision of the joint cavity and removal of all loose osteochondral fragments. Anatomic reduction of the PM is confirmed by lateral fluoroscopic views. Only then, reduction and internal fixation of Weber type B fibular fractures are performed in a third step from the same approach. The correct position of the fibula within the FN is checked visually.

Fractures of the medial malleolus may be treated via a medial approach either before or after internal fixation of the fibula. The deltoid ligament is revised only in case of a persisting widening of the medial clear space or spontaneous valgus tilt of the talus (81). An associated displaced fracture of the Tillaux–Chaput tubercle of Rammelt type 2 or 3 (78) or a displaced Wagstaffe fragment, if present, is reduced and fixed via a small, separate anterolateral incision (82). In the last step, the stability of the tibiofibular mortise is checked after fixation of all fractures and bony avulsions with stress testing. Any residual instability of the tibiofibular mortise is addressed by the additional insertion of a syndesmotic screw or flexible implant. In Weber type C fibular fractures in the middle and proximal thirds, only the distal fibular fragment is reduced into the FN and stabilized by syndesmotic screw(s).

The sequence of reduction is continuously controlled with an image intensifier (or intraoperative 3D imaging). Postoperative CT scanning is advised in case of syndesmotic stabilization if there are doubts about the accuracy of the reduction of the PM and reduction of the distal fibula into the FN (76). The immediate postoperative protocol must include control of the peripheral neurovascular status and exclude the development of a CS. Further, postoperative management aims at functional rehabilitation under protected weight-bearing.

Complications

Probably because of the severity and a still limited awareness of the injury, BF may be associated with severe complications. BF seems to be particularly prone to neurovascular and soft tissue complications. Bosworth (1), in his pioneer article, reports one case where ‘the foot circulation was shut off’. Fahey et al. (11), in 1956, described cyanosis, numbness, and decreased temperature in two patients treated operatively for BF, after repeated attempts at closed reduction had failed. CS associated with BF was for the first time described by Szalay and Roberts in 2001 (25). Since then, a total of nine cases were reported, accounting for 5.4% of all published BF cases, which is a high percentage given the extreme paucity of reported CSs in malleolar fractures (70). Prevention of this complication consists in a timely and eventually open reduction of the fracture, careful examination, and follow-up of the patient.

Other soft tissue complications associated with BF include skin necrosis (38), infection (37), and ankle stiffness, particularly after delayed reduction (7, 33, 54, 70), or deep peroneal palsy after repeated reductions (66).

Wang et al. (64) described a rare complication after PM reduction and internal fixation from the posterolateral approach when postoperative CT revealed persisting dislocation of the fibula from the FN.

Results

Little is known about the outcome of BF because the majority of authors followed their patients merely for several weeks or months, and some did not present any results at all (1, 2, 3, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71). Only 14 patients were followed up for 2.5 years, and 10 patients for more than 4 years (7, 11, 33, 72, 73). The longest follow-up period was 13 years following open reduction and internal fixation in a 35-year-old male patient (73). He had some limited range-of-motion at the ankle but an anatomic alignment without signs of chronic instability or posttraumatic arthritis.

There are only anecdotal reports on the results of nonoperative treatment. Good short-term results after a successful nonoperative reduction were reported only anecdotally by Fleming and Smith (10) with a follow-up period of 7 months, and Ji et al. (67) with a follow-up period of 30 months. Fan (61) followed up with a patient for only 6 weeks, and Mayer (3) specified neither the follow-up period nor the results in three patients treated nonoperatively. It appears logical that nonoperative treatment of BF carries the risk of residual instability and/or incongruity with subsequent development of posttraumatic arthritis. Ankle arthrodesis within 2 years post injury was performed by Bosworth (1) himself in two patients referred to him late after nonoperative treatment, and by Bartoníček et al. (7) in one patient after a failed closed reduction, who had rejected surgery at the first presentation.

The results of operative treatment are mixed. Many authors, particularly in earlier publications, report persistent pain even after a short time interval (48), with limitation of the range of motion or even stiffness of the ankle joint (5, 16, 18, 22, 29, 33, 34, 57), and development of degenerative changes (1, 11, 45, 50). This may reflect the complex nature of the injury with considerable accompanying soft tissue trauma. Won et al. (55), in the largest available study, found significantly better 1-year results after early reduction compared with delayed surgery (more than 24 h).

Risk factors for poor results include the severity of the injury, i.e. the presence of a partial pilon fracture (45, 50), and failed closed reduction of the fibula into the FN (1, 7). More detailed information could be provided by postoperative CT imaging which, however, is currently employed by a few authors only (50, 73, 76). Overall, there is a need for clinical studies reporting the medium- and long-term results of BF treatment in a larger number of patients (83).

Conclusion

BF presents a rare but severe variant of a locked ankle fracture-dislocation. One of the main causes of complications and/or poor results seems to be low awareness of this fracture pattern and minimal experience in its treatment at a given institution. BF requires an active approach with early reduction of the displaced fibular fragment without repeated attempts at closed reduction, and CT examination, including 3D reconstructions, allowing to plan an optimal surgical procedure. The aim of operative treatment is the restoration of ankle congruence and stability. This requires reduction and fixation of all bony components of the fracture including displaced or impacted fractures of the PM, Tillaux–Chaput tubercle, and/or Wagstaffe fragment, as well as anatomic reduction of the distal fibula into the FN. The quality of reduction should be confirmed by postoperative CT imaging. Future studies should include larger patient cohorts with a longer follow-up (minimum of 5 years).

ICMJE Conflict of Interest Statement

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding Statement

This work was supported by the Ministry of Health of the Czech Republic, grant no. NU22-10-00240: Severe types of ankle fracture-dislocations (Maisonneuve and Bosworth fractures) – diagnostics, pathoanatomy, treatment, and complications. All rights are reserved.