Abstract
Purpose: Medial Opening Wedge High Tibial Osteotomy (MOWHTO) is a joint preserving procedure of the knee. Currently we understand the anatomical changes occurring in the varus/valgus plane, but our understanding of other anatomical changes are limited. The objective of this study is to determine immediate anatomical changes occurring about the knee following MOWHTO. Our hypothesis is that anatomical changes occur in all planes of motion. More specifically, we hypothesize that posterior tibial slope is increased and patellar height is decreased immediately following the osteotomy.
Methods: This study was prospective in design. Patients with knee OA were evaluated according to strict inclusion and exclusion criteria. Pre-operative clinical assessment, radiographic evaluation, and patient assessment scores were performed. Intraoperatively, patients had radiostereometric analysis (RSA) beads placed in a predetermined pattern. Intraoperative radiographs were taken. The MOWHTO was then performed. A second radiograph was then taken following the osteotomy. The radiographs were analysed using dedicated RSA computer software to determine anatomical changes.
Results: Eleven patients were included in this study. Average age was 50 years. Mean error and condition number were 0.70 and 74 respectively, indicating highly accurate and reliable results. Analysis of the proximal tibia showed an average valgus correction angle of 8.69 degrees. The average osteotomy size was 12.5mm (9–17.5). Posterior tibial slope increased on average by 2.07 degrees (+5.91–−1.56). Analysis of the patella revealed anatomical changes occurred in all planes. However, the only consistent alteration was a decrease in patellar height by an average of 8.16mm (1.79–13.17). Additionally, there was a consistent increase in patellar tendon length by 5.30mm (2.38–7.34).
Conclusions: Using RSA in MOWHTO for the first time, we were able to demonstrate a useful and accurate measurement tool for this procedure. We found there were many immediate anatomical changes following MOWHTO that are inconsistent and not well understood. There were, however, several anatomical changes that remained consistent among all subjects. Patellar height decreased, patellar tendon length increased, and posterior tibial slope demonstrated an average increase.
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
