Tibialis posterior tendon entrapment in posterior malleolar and pilon injuries of the ankle: a retrospective analysis

J. Aamir, A. Syziu, L. Andritsos, R. Caldwell, L. Mason

Background: The Tibialis Posterior tendon (TPT) is the only tendon to come into contact with the distal tibia and is therefore at greatest risk of injury in fractures of the distal tibia. Although TPT injury has been reported rarely with injuries around the ankle they often have been missed and present late.

Aim: Our aim was to analyse the rate to TPT entrapment in fractures involving the posterior tibia i.e. Pilon and posterior malleolar fractures (PMF).

Methods: A retrospective analysis of Pilon and PMFs over a 10-year period was undertaken. Patients who had undergone surgical fixation of their PMF or Pilon fractures were identified from our prospectively collected database between 2012 and 2022. Any fracture which had undergone a preoperative CT was included. Analysis of their pre-operative CT imaging was utilised to identify TPT entrapment, where if ≤50% of the tendon cross section was present in the fracture site this was denoted as a minor entrapment and if >50% of the tendon was present in the fracture site was denoted as major.

Results: A total of 207 patients were identified for further analysis, 158 had a Pilon injury and 56 who had a PMF. The incidence of TPT entrapment was 20.77% (n = 43) with 39 minor and 4 major entrapments. If the fracture entered the TPT sheath, there was a 43.30% (42/97) of entrapment as compared to 0.91% (1/110) in fractures not entering the sheath (p<.001). TPT was significantly more common in PMF as compared to Pilon fractures (p=.001).

Conclusion: In our assessment, there was a significant risk of TPT entrapment when the CT images display the fracture line entering the tendon sheath. We recommend that surgeons consider pre-operative imaging in Pilon and PMFs and to actively look for TPT entrapment intraoperatively where entrapment does occur on CT.