The overall alignment of one’s knee can be very important to the success of several different types of operative procedures. This includes articular cartilage resurfacing procedures, meniscal transplants, and different types of knee ligament reconstructions, especially for chronic injuries or for revision surgeries.
One’s alignment is obtained by drawing a line from the center of the femoral head to the center of the ankle (the talus). The point where this line crosses the knee determines alignment. Normal alignment is felt to be between the apexes of the medial and lateral tibial eminences. Alignments that fall medial to this point are felt to be bow-legged, or genu varus alignment, for those that fall lateral to this point are knock-kneed and are called genu valgus alignment.
In addition to assessing what we call a frontal plane of the knee for overall alignment, it is also important to look at sagittal plane alignment, which looks at the side of the knee. This is especially important for localized areas of arthritis or for ligament reconstructions.
Description of Biplanar Osteotomy
A proximal tibial osteotomy involves making a surgical cut (or fracture) parallel to the tibial joint line followed by the insertion of a surgical plate with a predetermined insert size to act as a spacer to hold the osteotomy open. The plate is then secured with the use of surgical screws. Intraoperative x-rays are required to determine the correct placement of the surgical “fracture” and to verify that the plate and screws are in the desired location.
In patients with an ACL deficient knee or who have a flexion contracture that undergo an osteotomy, there is a desire to try to decrease the tibial slope. This will help to improve patient’s extension in patients with knee flexion contractures, and concurrently help to provide further stability to the knee in patients with an underlying ACL tear. This is especially important in patients who may have so much arthritis that an ACL reconstruction would not felt to be indicated. Thus, the biplanar osteotomy can help to tighten up the knee without the need for a further ACL reconstruction. Concurrent with this, in patients who have hyperextension of the knee (genu recurvatum), or a chronic PCL tear, there would be a desire to try to increase the tibial slope to both prevent the knee hyperextension and also to try to improve the stability of the PCL deficient knee.
In addition to the role of a biplanar osteotomy for these ligament conditions, a biplanar osteotomy may also be indicated in patients with an underlying arthritic knee for which a proximal tibial osteotomy is performed for medial compartment arthritis. In patients who have had a previous medial meniscectomy and who have most of the arthritis on their medial compartment of the knee along the posterior aspect, a biplanar osteotomy to try to decrease the tibial slope may be indicated to try to place more of the stress on the remaining more normal cartilage in the anterior part of the medical compartment.
The rehabilitation program for biplanar osteotomies is similar to that performed solely for the medial compartment arthritis. The patients are sent to physical therapy soon after surgery to try to decrease swelling and improve their overall muscle activation. This greatly helps with decreasing the need for narcotic pain medications. They also are allowed unlimited range of motion. The patients are kept non-weight-bearing for 8 weeks and than progress per our standard osteotomy protocol.
In patients who have the osteotomy performed for ligament reconstruction purposes, we generally have them perform rehabilitation between months 4 and 6 postoperatively and then determine if they are having continued ligament instability to determine if a second stage ligament reconstruction is necessary. For patients who have chronic posterolateral injury and who undergo a proximal tibial opening wedge biplanar osteotomy for genu varus alignment, we have found through our outcome studies that about 40% of patients do not need a second stage reconstruction. In general, these are usually patients who had a low velocity injury or who have an isolated posterolateral corner injury. Thus, patients who had a multiligament or high velocity injury have a higher risk of needing a second stage multiligament reconstruction after the osteotomy heals.