Radiostereometric analysis of early anatomical changes following medial opening wedge high tibial osteotomy

Background: The objective of this study was to use radiostereometric analysis (RSA) to evaluate the anatomical changes that occur in the tibia immediately after surgical correction with medial opening wedge high tibial osteotomy (HTO), and the changes that occur over the course of the first twelve. weeks of osseous union. Methods: Patients included nine males and one female, with a mean age of 49.0±5.5years and mean BMI of 28.4±3.8kg/m². The patients underwent HTO using a non-locking plate. RSA marker beads were inserted in the tibia, femur, and patella. RSA exams were first obtained intra-operatively prior to the osteotomy, and subsequently at one, two, four, six, and twelveweeks postoperatively. Results: Patients were corrected from a mean alignment preoperatively of 8.6. ±. 2.5° to 0.3. ±. 1.9° postoperatively, with a mean osteotomy of 12.5. ±. 3.6. mm. Immediate tibia changes surrounding the osteotomy site included 9.2. ±. 2.4° of valgus rotation and 6.2. ±. 2.0. mm of distal translation. Secondary motions included 2.5. ±. 2.4° of internal rotation of the distal tibia, 1.8. ±. 1.4. mm of posterior movement of the femur, and 8.5. ±. 3.4. mm of patella baja. Micromotion between the proximal and distal tibial segments decreased over time. Conclusion: The results suggest that subtle changes to the anatomy occur, beyond what is intended with the procedure, but partial corrections of these phenomena occurred over the twelve. weeks. Micromotion surrounding the osteotomy site decreased with osseous union. Level of evidence: Level IV, case series.