Early weight bearing after posterior malleolar fractures: an experimental and prospective clinical study

Abstract

The distribution of axial load to the lower end of the tibia at different positions of the ankle joint for the anterior, middle, and posterior part of the joint was studied in both photoelastic models and fractured ankle joints in cadaveric specimens. Synthetic models were used to simulate both normal ankle joints and ankles with fractures of the posterior lip of the tibia. Tests were performed with the ankle at dorsiflexed, neutral-flexed, and plantarflexed positions of the ankle joint. The clinical portion of the study evaluated 15 patients with fracture of the posterior malleolus that comprised 0% to 33% of the articular surface. All patients had open reduction and internal fixation through a posterolateral or posteromedial approach, and were allowed full weight bearing in a cast within 7 days of surgery. In the simulated models, the posterior one fourth of the ankle joint remains unloaded in the majority of the cases. The stresses are greatly increased when the load is doubled and are mainly distributed to the 2 central quadrants. With additional axial load, the fourth quadrant sustained little increase in the load bearing. All patients have had an uneventful recovery. By the second postoperative month, they were able to walk normally and had a painless range of motion of the ankle. By the third month, all patients were able to undertake their daily activities, and all fractures were consolidated. The clinical relevance of this study is early weight bearing, after open reduction internal fixation of posterior malleolar fracture of the ankle joint, facilitates recovery, promotes fracture union, and allows the patient to assume normal activity by the third month after surgery.