Review Question - QID 220411

Posterior tibial (PT) tendon entrapment is a well-described but often overlooked complication of high-energy pilon fractures, mainly when posteromedial fracture lines are present (answer choice 4).

Posterior tibial (PT) tendon entrapment is a known but rare complication of pilon fractures. This occurs when the PT tendon becomes interposed within the fracture site, primarily when posteromedial fracture extension is present. This entrapment can lead to persistent pain, limited ankle motion, and dysfunction of the PT muscle, causing decreased foot inversion and weakened medial arch support. Failure to recognize and release the tendon during fracture fixation may contribute to chronic symptoms and impaired recovery. Early identification is possible intraoperatively when a posteromedial fracture gap is persistent. Preoperatively, CT imaging with soft-tissue windows has been found to be the most efficient and consistent method of diagnosis. Treatment involves tendon mobilization and surgical reduction to restore proper biomechanics and minimize post-traumatic dysfunction.

Eastman et al. published a retrospective study analyzing 420 pilon fractures over a six-year period. Preoperative radiographs and CT images were obtained and reviewed for entrapped posteromedial structures. The posterior tibialis tendon was the most common entrapped structure in 95% of cases, with the posterior tibial neurovascular bundle entrapped in 10% of cases. The authors note that despite adequate preoperative imaging, interposition may still be missed preoperatively. Therefore, the authors recommend a posterior-based approach when posteromedial entrapment is suspected.

Labrum et al. published a review of cases and techniques for identifying and treating posterior tibial tendon entrapment in pilon fractures. Specifically, the authors note posteromedial fracture fragments to be the particular variant that can involve a PT tendon incarceration. The authors recommend CT imaging on all pilon fractures due to their complexity, but recommend evaluation of CT imaging on soft-tissue windows to evaluate for PT entrapment. The authors highlight the underappreciated phenomenon of PT incarceration and recommend increased scrutiny when evaluating these fracture patterns. Regarding treatment, the authors performed posteromedial incisions and gentle manipulation of the PT tendon with a penrose drain before the anatomic fixation of the posteromedial fracture fragment.

Figures A and B are the AP and lateral preoperative radiographs of a high-energy pilon fracture. A posteromedial fracture fragment is appreciated on these radiographs.

Incorrect Answers:
Answer choice 1: Deltoid injury is common in high-energy pilon fractures. However, this would not cause ankle inversion weakness or entrapment of the posteromedial fracture line causing gapping.
Answer choice 2: Flexor hallucis longus (FHL) entrapment is much less common than PT tendon entrapment on the posteromedial ankle due to the more posterior position of FHL relative to the posteromedial fracture fragment.
Answer choice 3: The peroneus brevis is a laterally based structure around the ankle joint and would not cause posteromedial fracture gapping, as seen in this patient.
Answer choice 5: A tibial nerve entrapment can occur with posteromedial fracture fragments with obvious entrapped soft tissue. However, this is less common than PT tendon entrapment. Furthermore, tibial nerve entrapment at this level would cause sensory loss in the plantar foot and weakness of intrinsic muscles rather than isolated inversion weakness.