Peroneal Tendon Dislocation With Talus Fracture and Subtalar Joint Dislocation: A Case Report

Abstract

Graphical Abstract

Introduction

Peroneal tendon dislocation is uncommon, representing 0.3% to 0.5% of traumatic ankle injuries. ¹ It typically results from disruption of the superior peroneal retinaculum (SPR), the primary restraint preventing subluxation or dislocation of the peroneus longus and brevis tendons. Regarding frequency, isolated peroneal tendon dislocation remains poorly quantified in the literature. By contrast, in a series of talus fractures evaluated with computed tomography, peroneal tendon dislocation was identified in 21.1% overall, with a higher rate of 39% in lateral process fractures. ² In intraarticular calcaneal fractures, a 28% prevalence has been shown in a multicenter study using computed tomography. ³ For subtalar dislocations, robust estimates of concomitant peroneal tendon dislocation are lacking, but the injury often coexists with fractures around the talus. Peroneal tendons contribute to ankle eversion, subtalar stabilization, and initiation of plantarflexion. Given these important functions, peroneal tendon instability may lead not only to pain and mechanical snapping but also to recurrent sprains and chronic tendon disorders. ⁴ Conservative treatments such as immobilization and rehabilitation may be attempted but are associated with higher redislocation rates and progression to chronic instability. ⁵ Because the presentation can mimic a lateral ankle sprain, misdiagnosis and delayed treatment are frequent. Moreover, associated osseous injuries around the hindfoot may mask the soft tissue lesion. In a prior study of calcaneal fractures, Toussaint et al ³ reported that peroneal tendon dislocation was frequently missed on initial imaging studies, highlighting the need to routinely evaluate the peroneal tendons on CT scans. A case of peroneal tendon dislocation associated with a talar fracture and subtalar joint dislocation is reported, and diagnostic pitfalls and the effectiveness of surgical repair with fracture fixation are emphasized.

Case Presentation

A 39-year-old man crashed when driving at approximately 70 km/h while depressing the accelerator. He was alert, complaining of right ankle pain with deformity and swelling. Distal pulses were palpable with brisk capillary refill; sensation and motor function in the toes were intact.

Initial radiographs and computed tomography (CT) demonstrated a distal tibial fracture, a lateral process fracture of the talus, and a subtalar joint dislocation (Figure 1). Closed reduction of the subtalar dislocation was performed under ketamine and propofol with longitudinal distraction (Figure 2). Post-reduction CT reconfirmed the fractures; the ankle was splinted and the patient admitted (Figure 3).

Figure 1.

Computed tomography on admission demonstrates a distal tibia fracture, a lateral process fracture of the talus, and a subtalar joint dislocation (yellow arrow). Views from (A) anterolateral, (B) medial, and (C) posterolateral. (D) Axial images at the level of the distal fibula: on the injured side, the peroneal tendons appear positioned anterior to the fibula (white arrow), whereas on the contralateral side they lie posterior to the fibula (black arrow outlined in white).

Figure 2.

Radiograph after closed reduction in the emergency department.

Figure 3.

Computed tomography scan after closed reduction shows anterolateral fragment of distal tibial fracture (red arrow) and talar lateral process fracture (white arrowhead).

After 2 weeks, soft tissue swelling had subsided to an acceptable level to perform surgery. Under general anesthesia with a thigh tourniquet, visible and palpable peroneal tendon dislocation was elicited by plantarflexion-eversion. Through an anterior approach using the interval between the peroneal muscles and the toe extensors, the anterolateral distal tibial avulsion fragment was reduced and fixed with 2 partially threaded 4.0-mm cannulated titanium screws. A 10-cm longitudinal incision was made on the posterolateral ankle, and a posterolateral approach was used. Intraoperatively, a disrupted peroneal tendon sheath posterior to the fibula was identified, and peroneal tendon dislocation was elicited with a maneuver combining plantarflexion and eversion (Figure 4A). The lateral process of the talus was reduced and fixed with a partially threaded 4.0-mm cannulated screw. The peroneal tendons were relocated into the retrofibular groove, and the torn sheath (SPR) was repaired anatomically with triclosan-coated absorbable sutures (Figure 4B). After reduction and fixation of fractures, fluoroscopic stress examination showed residual subtalar laxity. Therefore, temporary transarticular fixation was performed to maintain the subtalar joint’s reduction while the soft tissues healed.

Figure 4.

(A) Intraoperative image shows the dislocated peroneal tendon (white arrow) and superior peroneal retinaculum tear (yellow arrowheads). (B) After the superior peroneal retinaculum repaired (yellow arrowheads), the peroneal tendons remain reduced posterior to the fibula throughout an arc of ankle motion.

Instability of the subtalar joint was noted on intraoperative fluoroscopy. A 3.0-mm Kirschner wire (K-wire) was inserted from the posterior plantar aspect toward the center of the talus to stabilize the joint. Postoperative images are shown in Figure 5.

Figure 5.

Postoperative radiographs show reduction of fractures and satisfactory screw and wire positioning. (A) Anteroposterior radiograph, (B) lateral radiograph, (C) 3-dimensional computed tomography from the anterolateral side.

A below-knee splint was applied for 4 weeks with nonweightbearing during this period, followed by partial weightbearing for 2 additional weeks. The K-wire was removed at 4 weeks. Gradual range-of-motion exercises and peroneal strengthening were introduced as pain allowed. Recovery was uneventful, and at 10 months the patient was symptom-free, fully weightbearing, and had returned to preinjury activity.

Discussion

A rare case of peroneal tendon dislocation with a talus fracture and subtalar joint dislocation following a high-energy mechanism is reported. Peroneal tendon dislocation accounts for only 0.3% to 0.5% of ankle injuries and typically occurs when a dorsiflexed foot is subjected to a forceful contraction of the peroneal muscles, rupturing the superior peroneal retinaculum and allowing the tendons to dislocate anteriorly over the lateral malleolus.^1,5 Moreover, injury mechanisms proposed for subtalar joint dislocation and related foot fractures commonly involve a dorsiflexed, everted foot subjected to external rotation and axial compression. Although malleolar fractures are frequently seen in similar ankle injuries, in this young male with good bone quality the energy was absorbed by soft tissues including the peroneal tendon sheath and by a subtalar dislocation, and no malleolar fracture was identified. The presence of a subtalar dislocation warrants surveillance for chronic subtalar instability and later post-traumatic arthrosis.

Because the clinical presentation resembles a lateral ankle sprain, peroneal tendon dislocation is often misdiagnosed. Delayed recognition can lead to recurrent dislocation and chronic pain. It should be considered in patients presenting with swelling, tenderness, and a snapping sensation over the lateral malleolus after a dorsiflexion injury. Although the examination is occasionally made difficult by swelling and pain, careful palpation to determine whether peroneal tendon dislocation or subluxation is present is important.

Peroneal tendon dislocation is frequently accompanied by an avulsion fracture of the fibula, known as the “fleck sign,” indicating collapse of the superior peroneal retinaculum. This sign implies small avulsion fleck at the posterior ridge of the distal fibula, consistent with avulsion of the superior peroneal retinaculum; the reported sensitivity is 44.4% and specificity is 88%. ⁶ Although not present in this case, intraoperative inspection confirmed tearing of the anterior SPR fibers. Magnetic resonance imaging (MRI) delineates tendon pathology and retinacular integrity but may miss dynamic instability; reported sensitivity is 66% and specificity is 100% compared with intraoperative findings. ⁷ Prior work has demonstrated that peroneal tendon dislocation may be overlooked on initial assessment. Toussaint et al reported that, in a CT series of 421 intra-articular calcaneal fractures, peroneal tendon displacement was present in 118 (28.0%) but recognized in only 12 (10.2%) initially. This reinforces the importance of routinely reviewing the peroneal tendons on CT, including soft tissue windows, when evaluating hindfoot trauma. ³ The injury-time CT in our case showed findings suspicious for anterior dislocation of the peroneal tendons (Figure 1). Moreover, dynamic ultrasonography offers superior functional assessment: Neustadter et al ⁸ reported a positive predictive value of 100% for detecting subluxation in 13 patients, and Rockett et al ⁹ found ultrasound sensitivity of 100%, specificity of 89.9%, and accuracy of 94.4%, whereas MRI sensitivity was 23.4% with specificity of 100%. Provocative dorsiflexion and eversion during ultrasonography enhances diagnostic yield, although acute pain may limit testing.

Surgical management of peroneal tendon dislocation is generally categorized into soft tissue and bony procedures. The most common soft tissue approach is anatomical repair of the superior peroneal retinaculum. Bony procedures, such as retromalleolar groove deepening, aim to increase tunnel volume and improve stability. A systematic review comparing SPR repair alone vs repair plus groove deepening showed improved American Orthopaedic Foot & Ankle Society (AOFAS) scores and redislocation <1.5% in both, with higher return-to-sport rates after groove deepening. ¹⁰ Thus, anatomical retinaculum repair remains the cornerstone of surgical treatment, with groove deepening reserved for athletes or recurrent cases. In this patient, isolated retinaculum repair with fracture fixation resulted in full functional recovery.

Conclusion

This case underscores the importance of considering peroneal tendon dislocation in ankle injuries, especially when associated with talus fractures and subtalar joint dislocation. Peroneal tendon dislocation is rare, and delayed recognition can lead to chronic pain or recurrent dislocation. Awareness of this injury mechanisms and the use of dynamic imaging can help avoid misdiagnosis and improve outcomes.

Supplemental Material

sj-pdf-1-fao-10.1177_24730114261421602 – Supplemental material for Peroneal Tendon Dislocation With Talus Fracture and Subtalar Joint Dislocation: A Case Report

Supplemental material, sj-pdf-1-fao-10.1177_24730114261421602 for Peroneal Tendon Dislocation With Talus Fracture and Subtalar Joint Dislocation: A Case Report by Yuya Furusho, Sadaki Mitsuzawa, Shinnosuke Yamashita, Tadashi Yasuda and Shuichi Matsuda in Foot & Ankle Orthopaedics