A pilot study to assess the safety and radiological performance of a new low-profile locking plate for high tibial osteotomy.

BACKGROUND: We report the first results of a new low-profile titanium locking plate for fixation of opening wedge high tibial osteotomy (OWHTO). Short spacer plates have been associated with a high hardware complication rate, whilst fixed angle locking plates have been associated with a high incidence of soft tissue irritation. This plate aims to achieve stable fixation whilst maintaining a low profile, allowing space for combined procedures. METHODS: All patients undergoing OWHTO with the Activmotion plate were retrospectively reviewed. Patients were allowed to progress to full weight bearing after two weeks. Radiographic assessment included the medial proximal tibial angle (MPTA) and posterior tibial slope at six weeks and then three monthly until union. All complications were recorded. RESULTS: Thirty-seven patients with 40 OWHTOs were included in the study. The mean MPTA increased from 85.2 preoperatively to 91.9 postop. Tibial slope changed from 5.2 to 4.2°. The correction was sustained until union with no loss of correction in the MPTA (median change 0.0, 95% CI for median (-0.25, 0.4)) or tibial slope (mean increase 0.32, 95% CI (-0.02, 0.67)). CONCLUSIONS: In this pilot study the Activmotion plate raised no safety concerns with regard to implant related adverse events or loss of initial correction. Early rehabilitation with immediate partial weight bearing was possible and all cases proceeded to osteotomy union with the exception of one case that needed to undergo bone grafting with implant retention. Premature removal of the implant was necessary in four cases due to symptomatic hardware irritation.