Irreducible ankle fracture dislocation: a case report of posterior tibial tendon entrapment

INTRODUCTION

Ankle fracture-dislocations are among the most severe ankle injuries, often lacking specific treatment guidelines.^1-3 Rarely, displaced bony and soft tissue structures around the distal tibiofibular joint, such as anterior and posterior fibular dislocation, deltoid ligament incarceration, or tendon entrapment (e.g., extensor digitorum or posterior tibial tendon PTT), can obstruct reduction.^2,4-9 In most cases of PTT dislocation, the tendon dislocates anteriorly over the medial malleolus through a ruptured flexor retinaculum.^4,10-12 However, in rare instances, the PTT can become incarcerated within the tibiofibular space through a ruptured syndesmosis.^4-6,12,13 This atypical positioning forces anterolateral talar subluxation and medial joint space widening, preventing closed anatomical reduction.^4,7,8,13,14 If undiagnosed, this condition can lead to significant functional instability, tendon damage, stiffness, arthritis, equinovarus deformity, and clawing of the first ray.^3,4,10,12,14 Prompt recognition and early surgical intervention are crucial to prevent long-term complications and restore ankle function.^2,5,10,14

CASE REPORT

A 61-year-old man was transferred to our institution 8 weeks after sustaining an open fracture-dislocation of the right ankle in a traffic accident. Initial reports noted an 11 cm open wound with medial extrusion of the distal tibial plafond (Gustillo Anderson IIIA). Radiographs revealed a Denis-Weber C type fracture and a pronation-external rotation injury per Lauge-Hansen classification (Figure 1). Urgent wound debridement and temporary stabilization with an external fixator were performed, followed by definitive osteosynthesis of the fibular fracture. Postoperative radiographs showed persistent anterolateral displacement of the talus and widening of the medial clear space (Figure 2). A later CT scan failed to detect posterior tibial tendon (PTT) entrapment. Revision surgery using an anteromedial approach revealed a complete rupture of the deltoid ligament and difficulty in reducing the tibiotalar joint. The PTT was found traversing from posterior to anterior between the tibiofibular interosseous space (Figure 3).

Once repositioned behind the medial malleolus, minimal effort was required for tibiotalar reduction. Osteosynthesis of the fibula was revised, with concomitant stabilization of the syndesmosis. Additionally, repair of the flexor retinaculum and deltoid ligament reinsertion were performed. The patient was immobilized in a neutral position with a posterior splint and remained non-weight-bearing for 6 weeks. Radiographs confirmed maintained alignment without hardware issues (Figure 4). At 12 weeks post-rehabilitation, he achieved full weight-bearing, 5/5 PTT strength, and complete ankle range of motion.

DISCUSSION

Irreducible ankle fracture-dislocations have been widely reported. However, only a few cases report PTT entrapment within the tibiofibular interosseous space.^1-6,10-15 Several factors may contribute to the persistence of dislocation, including displaced bony and soft tissue structures surrounding the distal tibiofibular joint.^2,4,5,7-9,15 Soft tissue involvement is often seen with the PTT and deltoid ligament, though less commonly, the flexor hallucis longus (FHL) tendon, flexor digitorum longus (FDL) tendon, and neurovascular bundle may also be involved.^1-3,8,13-15

PTT entrapment has been reported in different anatomical locations correlated with the amount of energy applied during the injury, ranging from the fracture site, either at the medial or posterior malleolus, anterior to the medial malleolus through a ruptured flexor retinaculum, to the interosseous space between the tibia and fibula.^{2-4,6,10,13,14}

Intraoperatively the tibiofibular syndesmosis and retromalleolar groove should be explored.^1-3,5,6,14 CT analysis has proven to have diagnostic utility in confirming PTT displacement.^3,4,12-15 Unfortunately, CT investigations may not detect all dislocations or tendon entrapment. If a PTT involvement is suspected, a stepwise analysis of the CT images using the soft tissue window is recommended.^2,3 Magnetic resonance imaging (MRI) may also be considered for tendon and ligament injuries investigation. However, MRI is often less accessible in the acute traumatic setting.^1-4,7,14

Heini et al and Trividi et al both described cases of high-energy ankle fractures-dislocations showing persistent widening of syndesmosis and medial clear space after initial surgical procedure.^13,15 In Heini's case, PTT entrapment in the tibiofibular interosseous space was diagnosed 8 months after the initial injury and the patient was submitted to PTT reduction through a Z-shape tenotomy and subsequent open reduction and internal fixation.¹⁵ Similarly, Trividi et al reported a Maisonneuve fracture-dislocation with PTT dislocation occurring through the syndesmosis, draping over the talar dome.¹³

Sato et al, reported a case in which recognition and reduction of the PTT incarceration was successful only after a third attempt at open reduction, 3 months after the initial surgery.¹² In this case, suspicion of persistent PTT dislocation arose due to the patient's reported difficulty in performing ankle inversion.

Most recently, Amaro et al described a case in which arthroscopic reduction of the tibialis posterior tendon was successfully performed.¹⁴ In the described case, the undiagnosed interposition of the PTT led to an irreducible ankle syndesmosis. X-rays revealed a distal tibiofibular dislocation with syndesmotic diastasis, lateral subluxation of the talus and a widened medial clear space. Careful examination of the CT could have also confirmed PTT dislocation earlier.

In summary, when faced with a challenging or inadequate reduction of an ankle fracture, TTP interposition should be considered as a potential cause.^1-6,9,12-14 Proper management and successful outcomes rely on an early diagnosis, careful intraoperative assessment and accurate surgical technique to address the interposed tissues.^{1-3,5,6,10,14} If misdiagnosed, it could lead to failed reductions, persistent pain, functional instability, tendon damage and dysfunction, as well as progressive arthritic changes.^{2-5,7,10,12,14-15}

CONCLUSION

This case highlights the crucial need to consider soft tissue interposition, particularly posterior tibial tendon incarceration, in cases of persistent ankle subluxation after high-energy fractures. Early recognition and intervention are essential, as missed diagnoses can lead to failed reductions, chronic instability, tendon dysfunction, and debilitating long-term complications.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

REFERENCES

1. 1. Lacasse JS, Laflamme M, Penner MJ. Irreducible fracture-dislocation of the ankle associated with interposition of the tibialis posterior tendon in the syndesmosis: A case report. J Foot Ankle Surg. 2015;54(5):962-6.
2. 2. Thoreau L, Kaminski L, Putineanu DC. Irreducible ankle fracture dislocation due to posterior tibialis tendon interposition: Diagnostic and clues for early management – A case report. Trauma Case Rep. 2019;20:100175.
3. 3. Tschudi S, Wittauer M, Hirschmann A, Eckardt H. Avoiding pitfalls in ankle fracture-dislocations: A case report of a dislocated tibialis posterior tendon causing persistent ankle subluxation. Foot Ankle Surg. 2021;27(6):700-9.
4. 4. Colomb E, Muscatelli SG, Morash JG, Crawford EA, Holmes JR, Walton DM. Irreducible fractures and dislocations of the ankle associated with entrapment of the posterior tibial tendon within the tibiofibular interosseous space: A case series and literature review. Foot Ankle Orthop. 2021;6(2):24730114211000297.
5. 5. Connors JC, Coyer MA, Hardy MA. Irreducible ankle fracture dislocation due to tibialis posterior tendon interposition: A case report. J Foot Ankle Surg. 2016;55(6):1276-81.
6. 6. Nguyen Van L, Nguyen Nang G. Ankle fracture-dislocation with the interposition of the tibialis posterior tendon in the ankle syndesmosis and tibiotalar joint – A case report and systematic literature review. Int J Surg Case Rep. 2023;110:108710.
7. 7. Seiça EC, Mendes D, Sousa MR, Vide J. Deltoid ligament injuries: When and how to repair. Knee Surg Sports Traumatol Arthrosc. 2024;32(1):1-10.
8. 8. Seiça MC, Armada L, Peixoto D, Thusing M, Mendes D, Sousa MR, Vide J. Rehabilitation and return to sport after ankle injuries in athletes. Fuß Sprunggelenk. 2023;21(14):67.
9. 9. Walker RH, Farris C. Irreducible fracture-dislocations of the ankle associated with interposition of the tibialis posterior tendon: Case report and review of the literature of a specific ankle fracture syndrome. Clin Orthop Relat Res. 1981;160:212-6.
10. 10. Anderson JG, Hansen ST. Fracture-dislocation of the ankle with posterior tibial tendon entrapment within the tibiofibular interosseous space: a case report of a late diagnosis. Foot Ankle Int. 1996;17(2):114-8.
11. 11. Lohrer H, Nauck T. Posterior tibial tendon dislocation: A systematic review of the literature and presentation of a case. Br J Sports Med. 2010;44(6):398-406.
12. 12. Sato R, Tsuchida Y, Murakami H, Shirakawa T, Futamura K, Hasegawa M, Suzuki T, Tsuihiji K. Fracture dislocation of the ankle with posterior tibial tendon entrapment within the tibiofibular interosseous space: A case report. Trauma Case Rep. 2019;23:100235.
13. 13. Trividi M, Brown E, Lese A, Katz LD. Lateral dislocation and incarceration of the posterior tibial tendon through the distal tibiofibular syndesmosis. Skeletal Radiol. 2014;43(8):1175-8.
14. 14. Amaro P, Ferreira J, Viegas R, Protásio J, Vide J, Mendes D. Posterior tibial tendon entrapment after fracture dislocation of the ankle. J Clin Orthop Trauma. 2022;2(1):100125.
15. 15. Heini PF, Ganz R. Anterolateral subluxation of the talus after overlooked dislocation of the tibialis posterior tendon. J Orthop Trauma. 1994;8(5):449-53.
16. 16. Seiça EC, Gamelas J, Canhoto J, Vide J, Cardoso A. Anatomical retinaculum repair and pseudo-pouch closure: surgical technique for management of posterior tibial tendon dislocations. Int J Res Orthop. 2024;11(1):218-24.