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A large percentage of adults suffer from knee arthritis. Arthritis may be the result of a degenerative condition, hereditary, or may have been caused by an earlier sports injury or accident to the knee area. Patients who experience osteoarthritis often strive for ways to improve knee function, limit pain, and for many, put off knee replacement surgery. One surgery to postpone knee replacement surgery and improve function is a knee osteotomy.
A knee osteotomy is a surgical procedure that Dr. LaPrade performs on patients who have a single compartment of their knee affected by osteoarthritis. While this surgery for knee arthritis is usually effective for most patients, it is not a long-term fix for the problem. The significance of having the surgery is that for many patients, the procedure can offer years, and often a decade or more, of improvement and possibly continue to delay the need for knee replacement surgery. Osteotomies of the knee have been validated to be effective for decreasing pain and improving patient movement in most instances.
Many people who undergo a knee osteotomy will eventually need a total knee replacement. However, research studies have reported knee replacements are more successful in patients over 60 years of age. Therefore, patients in their 30’s, 40’s and 50’s are ideal candidates for knee osteotomies.
During a knee osteotomy, Dr. LaPrade will add a wedge of bone graft to the upper shinbone (tibia) or lower thighbone (femur). In essence, this helps shift a body’s weight off the damaged area of the knee joint onto the more normal cartilage area on the opposite side of the knee.
During an opening wedge osteotomy, Dr. LaPrade may use hardware, such as screws and plates, to hold the bones of the knee to their new aligned position and add bone graft to help the osteotomy heal faster. Most patients who undergo a knee osteotomy will stay in the hospital for two days for pain control and to initiate physical therapy.
Patients are generally sent to physical therapy immediately after surgery to work on swelling control, muscle reactivation, and knee motion. In general, patients are non-weight bearing on crutches for 8 weeks and progressively wean off crutches over the next month. This is achieved by slowly increasing weight bearing on the leg at ¼ body weight per week. Patients are only allowed to progress their rehabilitation program with weight bearing after review of x-rays. In general, most patients are able to wean off of crutches at 3 months after surgery. A low impact exercise program to include walking, cycling, and aquatic therapy is progressed at this time. Most patients note significant improvement of their function by 4-6 months after the knee osteotomy.
An osteotomy involves basically a surgical fracture, to change the alignment and weightbearing of structures at the knee. There are three main types of osteotomies of the knee, proximal tibial osteotomies, distal femoral osteotomies, and tibial tubercle osteotomies. All of them are performed for different reasons.
A tibial tubercle osteotomy involves creating a surgical fracture and moving the tibial tubercle, which is where the patellar tendon attaches on the tibia. Tibial tubercle osteotomies are usually performed for either helping to balance one’s kneecap stability better or to offload an area of arthritis at the kneecap.
Proximal tibial osteotomies are usually performed for patients who are bowlegged and to either offload an area of arthritis or to offload a cartilage resurfacing procedure or a meniscus transplant. The most common type of proximal tibial osteotomy is an opening wedge proximal tibial osteotomy where the bone is fractured to about 1 cm of the opposite side, usually from the inside part of the tibia, and the bone is held open with either a plate and wedge or a bone graft and screws. Proximal tibial opening wedge osteotomies are the most common ones and are usually performed for osteoarthritis. Other types of pathologies to treat knee malalignment at the tibia include chronic knee ligament injuries, such as a chromic posterolateral corner injury with somebody who is bowlegged, a chronic PCL tear with a flat slope which needs to be increased, or a chronic ACL tear with an increased tibial slope which needs to be decreased.
The other main type of osteotomy performed at the knee is a distal femoral osteotomy. These are usually performed in patients who are knock-kneed, or in valgus alignment. The most common type is an opening wedge technique, where an incision is made on the outside of the knee, the femur is broken at an oblique angle to within 1 cm or so of the opposite medial cortex, and then the bone is jacked open and held with a plate and screws or other devices. This is usually done to try to bring the knee back to where the weightbearing goes from being knock-kneed back through the center of the joint. Distal femoral osteotomies in patients who are knock-kneed, or in valgus alignment, can be performed for patients who have arthritis of their outside, or lateral, compartment of the knee, concurrent with a meniscus transplant or cartilage resurfacing procedure in the lateral compartment in patients who are knock-kneed, or for patients who have a chronic MCL tear.
Because distal femoral and proximal tibial osteotomies are basically a surgical fracture, they can be quite painful and one needs to work with the surgical team on anesthesia nerve blocks and appropriate pain medicines to ensure that they appropriately progress in their rehabilitation program. We usually keep patients in the hospital for two days after proximal tibial or distal femoral osteotomies, because we find that these patients often have breakthrough pain which requires an emergency room visit within the first few days after surgery if they are discharged early.
One way to help mitigate a difficult postoperative course is for one to start physical therapy and a program of icing of their knee immediately after surgery. This is because swelling often causes a lot of the pain around an osteotomy at the knee, and trying to minimize swelling, working on reactivation of the muscle, and working on knee motion often helps to decrease the pain and get one off of narcotic pain medications sooner.
It is important to recognize that a proximal tibial osteotomy is a controlled fracture which is performed to realign one’s weightbearing line between the center of their hip and the center of their ankle. This weightbearing line is often carefully calculated to ensure that the surgery lasts and is durable for as long a period of time as possible.
Therefore, initiation of weightbearing prior to proper healing, or before the surgical plate and fixation may allow it, may result in some settling of the osteotomy amount, or could result in breakage of the screws. Therefore, the different types of weightbearing protocols after surgery can be as diverse as the types of fixation for osteotomies and surgical techniques. For patients who have a proximal tibial osteotomy with an external fixator distraction frame, weightbearing is often started almost immediately. However, these patients need to dial in the amount of separation of the bone over time and this can be quite painful, and also the surgical pin tracks have a high rate of infection. Therefore, we have generally gone away from this type of osteotomy because most patients do not tolerate them well.
There are some big and bulky osteotomy plates that do allow for early weightbearing, but the ability to change the tibial slope is less with these types of plates and almost all the time these plates have to be removed after surgery because they cause pain with activities.
It is my belief, from an analysis at a post-graduate level of treatment, almost every proximal tibial osteotomy needs to have a change in the tibial slope. This is because the inside part of the knee usually does not wear out uniformly, the back of the knee wears out faster after a medial meniscus is taken out, and the associated injuries with an osteotomy require either an increase or decrease in tibial slope. For example, ACLs do much better with leveling of a tibial slope, whereas PCLs do better with an increase in tibial slope. The same is true for a patient who has increased heel height or genu recurvatum, where an increase in tibial slope will be effective at decreasing the recurvatum. In general, the plates that allow for a change in slope do not allow for early weightbearing, so one needs to be on crutches for up to eight weeks to minimize the risk of settling of the osteotomy to maximize one’s ultimate outcome.
The amount of time that one “gets” from a proximal tibial osteotomy is dependent upon many factors. This can include the baseline amount of arthritis, the correction angle, the amount of stiffness in one’s knee, and the status of the cartilage and amount of cushion (the meniscus) in the lateral compartment. All of these factors together are factors that can determine how long one would benefit from a proximal tibial osteotomy. In addition, it has been shown that patients that are heavier, with a higher body mass index (BMI) tend to wear out their knees faster.
In general, the estimated rates for obtaining benefit from a proximal tibial osteotomy are that about 70% to 80% of patients will get 10 years out of it. However, all of the above factors, as well as one’s activities after surgery, contribute to this.
Probably the best way that one can ensure that they get the most benefit from a proximal tibial osteotomy are to minimize one’s weight gains, or maximize one’s weight losses, and to work on a low-impact exercise program on a regular basis. This allows one to have good absorption of their lower extremity, which should help to minimize any progression of osteoarthritis.