Osteonecrosis of distal tibia in open dislocation fractures of the ankle

Open ankle dislocation fractures are one of the most severe injuries of the ankle. Development of posttraumatic arthrosis is well known. However, there are just a few case reports describing evidence of posttraumatic osteonecrosis (PON) of distal tibia. The pathophysiological mechanism remains unclear and the question of morphologic or personal risk factors cannot be answered. The goal of this study was to evaluate the morphologic characteristics of open dislocated ankle fractures in correlation with the development of PON to facilitate early identification of patients with higher risk of posttraumatic osteonecrosis.

In this study data from 28 patients with open dislocation fractures of the ankle between 1975 and 2006 found at our databases were evaluated retrospectively. For each patient we documented personal data, mechanism of injury, type of lateral malleolar fracture, severity of open fracture, degree of tibiotalar dislocation, presence of medial malleolar fracture, presence of deltoid ligament rupture, time until joint reduction and kind of surgical treatment. We also documented clinical complications and number of surgeries. Presence of PON was examined by radiographs, magnetic resonance imaging (MRI) or histological analysis.

Within 12 out of 28 patients with open ankle dislocation fractures a PON of the distal tibia could be found. Nine out of 15 patients with high-energy trauma and 12 out of 19 patients with type C fibular fracture developed PON. 73% of male patients and 88% of the patients with type III soft tissue damage according to Gustillo developed PON. However, if patients suffered from type C fibular fracture, total talus dislocation and grade III soft tissue damage ("necrotic triad") PON was developed in 100% of cases. Other patient's characteristics like late joint reduction, postoperative infection or bimalleolar fracture showed no higher proportion of patients with PON.

In this study we were able to identify clinical manifestations and risk factors for the development of PON of the distal tibia. All indentified risk factors were associated with heavy fracture mechanisms leading most likely to a serious devascularisation of at least parts of the distal tibial epiphysis. With regard to presented results early identification of patients with higher risk of PON might be possible and maybe additional treatment options can be initialised to protect patients from this process.