Effect of ultrasound therapy on bone healing of lateral malleolar fractures of the ankle joint fixed with bioabsorbable screws

Background We investigated the effect of low-intensity ultrasound on bone healing in bioabsorbable self-reinforced poly-l-lactic acid (SR-PLLA) screw-fixed lateral malleolar fractures. The study design was prospective, randomized, double-blind, and placebo-controlled.Methods A total of 22 fractures were fixed with one SR-PLLA screw. All the patients were instructed to use an ultrasound device 20 min daily for 42 days without knowing whether it was active or inactive. Eleven patients had active and eleven sham ultrasound devices. The causes of error during treatment with head module placement and attachment to the convex surface of the lateral distal fibula were minimized by careful targeting and using coupling gel. Radiological fracture healing was assessed by radiographs and multidetector computed tomography (CT) scans in a blinded manner by a radiologist and orthopedic surgeons.Results The overall compliance to the daily ultrasound treatments was good. All wounds healed uneventfully, and no foreign body reactions were observed. No difference was observed between the groups regarding either fracture line visualization or callus formation assessed by plain radiographs. In the CT images at 9 weeks, the share of the endosteal united fracture line compared to the non-united fracture line was slightly higher in the active ultrasound device group than in the sham ultrasound device group, but the difference was not statistically significant.Conclusion The study indicates that the biocompatibility of ultrasound therapy and bioabsorbable SR-PLLA screw fixation is good. There was no obvious effect of low-intensity ultrasound on lateral malleolar fracture healing. However, the relatively small number of patients must be kept in mind when interpreting our results. It is also important to limit any conclusions based on the present study to malleolar fractures fixed with the SR-PLLA screw.