Bosworth ankle injuries (BAIs) occur infrequently with a prevalence of 1.6% among all ankle fractures [1]. It was first described by Bosworth in 1947 [2] as an irreducible dislocation of the ankle with fractured fibula getting incarcerated behind the distal tibial metaphysis [4]. In this challenging injury, open reduction of the talocrural dislocation is inevitable to achieve reduction that prevents pressure necrosis of the anterior skin, vascular damage, neurologic impairment, and chondral damage. The supination external rotation injury [3, 4] may often result in disrupted syndesmosis in addition to fibular fracture. Perry [4] showed a sequential tear of the tibiofibular ligament in addition to the capsule and interosseous membrane. Downey [7] described an irreducible posterior dislocation with an intact fibula an atypical variant of BAI. X-rays can be studied for the initial diagnosis. Khan and Borton described the Axilla sign [5] for these uncommon injures. BAI is one of the exceptional conditions, where the pre-reduction computed tomography (CT) scan can be an useful tool [8]. The orthopedic instinct of repeated closed reduction often worsens the swelling and compromises the situation. The better outcome of BAI with the early intervention (1) needs diagnostic suspicion in irreducible [6] ankle dislocations.

Retrospective study of five cases reported between 2016 and 2020 with delayed presentation of BAI. The age range was 25–62 years (Table 1. patient demographics) with a time delay (2–28 days, mean 11.2 days) for definitive treatment. The chronic neglected case had 7 months delay. The mechanisms of injury were twist and fall, and RTA resulting in isolated closed fracture-dislocation in all these cases. Clinical symptoms were pain, swelling, and reduced mobility of their ankle for daily activities. On assessment, they had signs of ankle fracture dislocation with no signs of associated compartment syndrome. Chronic lipodermatosclerosis was encountered in the neglected case. The neurovascular status were intact.

The X-ray on presentation (Fig. 1a, 2a, 3a) showed bi- or trimalleolar fracture with joint disruption and the proximal end of fracture fibula behind the posterior tibia. All these patients had a single

attempt of closed reduction at their initial consultation. In view of the delayed presentation, we avoided reattempts for closed reduction. After optimization, open reduction and operative stabilization was achieved in all the four cases except in the chronic neglected presentation. The posterolateral approach favored the reduction and a Hohmann retractor helped in the disimpaction of the incarcerated fibula. The Weber B, C fracture was stabilized with a lateral buttress plate and an additional tricortical syndesmotic screw through the plate to increase the screw pull-out strength, a modification (Figs. 1b and 2b), we consistently followed in this series of cases.

The curvilinear medial incision exposed the medial fragment. Deltoid ligament interposition was found in two cases. Medial reducibility was checked even before fixing the lateral side in every single case. Lag screw principle was used on the medial side using 4 mm partially threaded compression screws where feasible and in one case due to the fragment size simply k-wires were used for fixation.

The neglected case of BAI with 7 months delay was diagnosed in a 53-year-old non diabetic lady. She had an isolated closed injury to her left ankle following a road traffic accident. After native splinting for 12 weeks she developed superficial ulceration over the medial malleolus. She became wheelchair-bound for her activities of daily living. Except for a high BMI of 39, a local examination showed a healed ulcer over the medial malleolus. The surrounding skin had secondary lipodermo sclerosis with the ankle in equino-valgus deformity. ROM at her ankle was 20° with further plantar flexion of 20° in the non-anatomical plane. She had severe stiffness of subtalar movements, but no distal neurological or vascular deficit. X-rays of the left ankle AP and lateral view (Fig. 3a-c) confirmed the posterolateral unreduced talocrural dislocation with trimalleolar fracture.

The lateral side was a Weber C type with posteriorly incarcerated fibular fracture behind the tibia. Attempted callus response was noticed on the lateral side. The talus appeared to have normal radiological features with no signs of subtalar joint pathology. Charcot’s neuropathy was excluded using the nerve conduction studies. Her distal arterial flow studies were normal and a venous Doppler excluded deep vein thrombosis. Pre-operative calcaneal pin traction was a sham reduction procedure that helped to reduce the soft-tissue tension.

Antero medial approach was used to address the dislocated ankle, as the distal part of tibia was entirely stuck in front of the talus. The non-anatomical plane of tibiotalar interface blunted the distal tibial plafond to become a convex surface. Additional posterior soft-tissue contracture plus the proximal migration of the talus posed a greater challenge for reduction. A reverse dome osteotomy of the talus allowed reduction of the convex distal tibial surface. With foot in plantigrade position, primary ankle arthrodesis was achieved with three partial threaded screws (Fig. 3d).

The post-operative plaster cast was changed over to weight-bearing air cast boot at 6 weeks and extended for 6 months.

Following open reduction and stabilization, patients gained back full weight-bearing mobility at an average of 12 weeks (range 8–16 weeks). Range of movement was average dorsiflexion of 20° (range 10–25), plantar flexion 20° (range 20–30°). Ankle fusion case with plantigrade foot gained back mobility at 6 months post-operative period. The VAS score for pain improved. Mobility and ankle stability were restored in all these cases.

BAI and its pathoanatomy were first described by D M Bosworth. A dislocation occurs in 21–36% of ankle injury cases but only the BAI are inherent for irreducibility [1]. Posterior displacement of fibula occurs after both osseous and ligamentous injury [4]. In the sequential damage [4], rotational forces continue, to cause weber B [2] or C type fracture. In addition to syndesmotic diastasis [1], the fractured fibula gets incarcerated behind the posterior tibia. About 70% of BAI have associated posterior malleolus fracture and an avulsion type of medial malleolus, rarely an adduction type of medial malleolar fracture [7] or a pilon fracture [11]. Atypical variant of BAI also includes intact fibular posterior displacement with ankle dislocation [12]. Patients with a displacement of the fibula behind the posterior tibial rim can have associated extra-incisural (Bartoníček/Rammelt) type 1 injury. The displacement between the posterior malleolar fragment and the tibia were associated with type 2 and 3 posterior malleolar fractures [11, 20]. Other various soft-tissue causes for irreducibility includes interposition of the deltoid ligament on the medial side, tibialis posterior tendon on the fibular fracture site, in the syndesmotic joint or through the interosseous membrane [10, 11] .

BAI, when presented with delay, open reduction still remains feasible and stabilization restores ankle joint mobility. When salvage is near impossible, primary ankle fusion is a viable option. Reverse talar dome osteotomy achieves reduction in neglected posterolateral ankle dislocation with BAI scenario. It restores plantigrade foot, redesign the articular surface for fusion and regain stability for weight-bearing mobility.