In patients with osteoarthritis that will undergo high tibial osteotomy, does the use of two different techniques produce the same change their gait mechanics?

In patients with symptomatic medial compartment (inner side), knee osteoarthritis (OA) and associated genu varum (bowing of the lower limb) performing a high tibial osteotomy (HTO) can provide pain relief by changing the shape of the limb. The shape changes the point at which compressive load crosses the knee. This unloads the painful arthritic side of the knee and transfer load to the undamaged lateral compartment (outside)of the knee. There are two widely used HTO techniques. These are the medial opening wedge (MO) and the lateral closing wedge (LC) HTO. Intraoperative computer navigation can increase the accuracy and precision of the intended correction but has not been used for the LC technique. It is unclear in the literature, which approach yields the highest patient satisfaction as very few studies have been done that compare the two techniques. Additionally, there are even fewer studies that have examined the changes to gait mechanics that take effect as a result of the described procedures. To detect a difference between the two procedures, patients will undergo preoperative and postoperative radiographic (x-ray) and functional joint assessments. In addition, investigators will assess changes to the patients' gait by performing analysis at a Gait Laboratory. Aims and Hypothesis: 1) That the same correction achieved intraoperatively using two different osteotomy techniques will produce the same correction to standing limb shape and gait mechanics 2) Computer navigated LC wedge is as accurate as computer navigated MO wedge HTO. Research Design: The design of this project is a single centre, multi-surgeon, prospective, randomised controlled trial. (Evidence Level II) Materials and Methods: Patients planned to undergo a HTO procedure at the investigators' clinic who fit study inclusion criteria, may be approached to voluntarily participate in the study. Patients will be randomised to the MO wedge HTO group or LC wedge HTO group at time of consent. Alignment corrections associated with the procedure will be standardised to 3.5 degrees of valgus. Patients will undergo assessments preoperatively, and postoperatively for followup in clinic at six weeks, six months and yearly.The intervention/procedure that will be performed is called a high tibial osteotomy (HTO). The operation involves changing the shape of the tibia (shin bone) by performing a bone cut (osteotomy) that does not completely finish and then separating the edges with a hinge at one end. The change in shape of the tibia results in changing the way force is transmitted through the knee joint. This accuracy and precision of this surgery is increased by the use of a computer navigation system. The corrections are held in place using a plate and screw fixation device. Arm 1: Medial Opening Wedge (MO) High Tibial Osteotomy. This procedure makes the aforementioned osteotomy on the medial side (inside edge) of the tibia and separates the edges from each other thus "opening" a wedge of bone. This is the commonest procedure done and will act as the control. Arm 2: Lateral Closing Wedge (LC) Hight Tibial Osteotomy: This procedure makes two cuts and removes a wedge of bone from the lateral side (outside edge) of the tibia and then the two ends are brought closer together. The surgical time for each procedure varies, both procedures take similar time from start (knife to skin) to completion (surgical wound closure). Both procedures can take from 45 minutes up to 1 hour each to complete.