Younger adults (65 or younger) who want to delay or avoid a total knee replacement may have other treatment options. One of these options is a surgical procedure called opening-wedge high tibial osteotomy. In this procedure, a pie-shaped wedge of bone is removed from the inside edge of the tibia (lower leg bone). The osteotomy is done at the upper end of the tibia just below the knee. The goal is to change the angle of the knee and thus alter the weight-bearing pattern.
Who can benefit from this approach? Well, as the technique describes, patients who put too much weight on the inner (medial) compartment of the knee might do well with this type of osteotomy. By shifting the weight more towards the middle of the knee, ground forces up through the foot when walking are evened out. The result can be to prevent medial compartment arthritis and put off (or even eliminate) the need for a joint replacement.
In this study, patients were not included who had already lost 20 or more degrees of knee extension (their knees were stuck in a bent or flexed position). This surgery was also not recommended if the patient couldn’t bend the knee past 70 degrees or who had an unstable knee joint. Instability was judged by how much the tibia could slide back and forth under the femur (thigh bone). More than a one-centimeter subluxation (movement toward dislocation) was considered a reason to exclude patients. These findings are more suggestive of someone who really needs a joint replacement and wouldn’t benefit from an osteotomy.
There were a total of 20 adults (men and women between the ages of 36 and 67) in this study. All met the inclusion criteria and were treated by the same surgeon. To be included in the study, patients had to have a confirmed diagnosis of medial compartment arthritis. This also meant they had an abnormal alignment of the knee called varus (too much angle putting too much weight on the inside edge of the knee). They all agreed to stay in the study and follow all recommendations made by the surgeon to avoid having a knee replacement.
Results were measured by comparing tests administered before surgery to after surgery values for the same tests. This information was obtained through before and after X-rays and gait (walking) using video data and computer software analysis. Patients walked on a 10-meter long walkway that had a force plate to record the weight-bearing pattern. Several well-known tests (e.g., Lysholm knee scale, Hospital for Special Surgery knee rating system) were used to assess symptoms, function, motion, strength, deformity, and stability.
Of course, the surgery took place between the two sets of measurements. First, the surgeon performed an arthroscopic exam. By inserting a scope inside the knee, he was able to look the joint over carefully for any defects in the cartilage. At the same time, the integrity of the ligaments and joint cartilage were assessed.
Once the arthroscopic exam was completed, then the surgeon performed the osteotomy. The surgeon made the correction to the knee angle and tested it by putting pressure through the heel up into the knee. The osteotomy opening was determined based on the weight-bearing line of the knee joint. [They made sure the weight-bearing line went through the lateral compartment (outside half) of the knee]. The exact steps for this operation are described in this article with X-rays to show the before and after knee angles. The new knee position was maintained with a metal plate and screws. Bone graft material was also placed in and around the opening made by the wedge cut.
Everyone was followed through regular appointments with the surgeon. When X-rays showed signs of solid bone forming at the osteotomy site, then the patients could start to put weight on that leg. Physical therapy was a part of the post-operative recovery plan. By the end of the two-year follow-up period, correction was still maintained for all patients. Not everyone was able to avoid having a knee replacement. About one-fourth of the group had a total knee replacement much later.
Overall, patients improved significantly in terms of decreased pain and improved function. There was evidence of improved gait patterns (returning to normal weight-bearing and load distribution across the knee). All patients were able to remain highly active without any restrictions on their activities.
The authors report medial opening-wedge high tibial osteotomy can provide good results in younger adults who want to avoid knee replacement yet still remain active. They suggest that correcting knee alignment is easier to obtain and control with this type of osteotomy compared with lateral closing-wedge osteotomy, for example.
Results of this study provide short- to mid-term outcomes. Because other studies of osteotomies show breakdown over time, it will be necessary to continue following these patients much longer to see the long-term results. Finding the optimal amount of correction is another area for future study. The authors used the weight-bearing line (making sure it passed through the lateral compartment) to unload the arthritic medial compartment. This may be an ideal method of determining the angle of alignment but future results will be needed to verify this approach.