Modification of tibial slope after medial opening wedge high tibial osteotomy: clinical study and mathematical modelling

A prospective non-randomized non-comparative study involved 30 patients who underwent a medial opening wedge high tibial osteotomy for medial knee osteoarthritis using a specific surgical procedure. The tibial slope was calculated pre-operatively and at a mean follow-up of 14 months. A mathematical model of the surgical procedure was developed in order to plan the height of the medial opening wedge and to predict tibial slope changes. Tibial-slope measurements accuracy was good (0.04A degrees A A +/- A 0.92A degrees). There was no significant difference for the mean tibial slope before and after surgery (9.2A degrees A A +/- A 5.6A degrees vs. 9.1A degrees A A +/- A 5.6A degrees, P = 0.47). There was a perfect agreement between the model and the real values for the HKA angle (0.85) and the tibial slope (0.98). The surgical technique used did not modify the tibial slope. Our mathematical model for pre-operative planning was validated with very good accuracy.