What is an Osteotomy and Why Are They Done?
Osteotomies, or bone cutting procedures, have been used by orthopedic surgeons for decades to realign crooked joints and bones. Osteotomies can be done around any joint, but they are most commonly done around the knee. The main indication for an osteotomy around the knee is to change the knee alignment in order to unweight an arthritic and painful area of the knee. Today, osteotomies are most often performed in people who are too young and active to have a knee replacement surgery, as they would prematurely wear out their replacement parts. Osteotomies are done in order to extend the life of a young person’s native knee that is arthritic on one side. Following an osteotomy, one can return to all activities without restriction as there is no concern of wearing out knee replacement parts.
How to Know if your Knee is Out of Place?
In order to assess the mechanical alignment of the lower extremity, a special x-ray is obtained whereby the hip, knee and ankle joint are all imaged together with the patient standing. A line can then be drawn from the center of the hip to the center of the ankle to determine whether the patient’s knee is in neutral, varus (bow legged), or valgus (knock kneed) alignment. If the weightbearing line travels through the outer portion of the knee, the patient is in valgus alignment and more of their weight is being transmitted through the outer portion of the knee. The opposite is true in the case of a varus aligned knee, where more weight is being transmitted through the inner portion of the joint. After years of being malaligned and also being active, a patient will start to preferentially wear out the cartilage on the portion of the knee that is overloaded. Patients with valgus malalignment overload and wear the cartilage on the outside of the knee joint. Those with varus malalignment overload and wear out the cartilage on the inside of the knee.
Knee cap (patella) malalignment is also common. Instead of tracking centered in the femoral groove (trochlea), the patella may track laterally or to the outside of the groove. This is often associated with someone being in valgus. Patients with a knee cap that tracks to the outside of the knee wear the cartilage on the underside of the knee cap over time at a faster rate. Furthermore, knee caps that track to the outside are more likely to dislocate out of the groove.
Wearing out the articular cartilage of the knee joint in the setting of malalignment can be compared to wearing out the tread on your tires of your car when the wheel is out of alignment. Fortunately, these knee malalignment issues can be corrected with an osteotomy procedure. Pain relief is good but there may still be some pain as the arthritic areas of the knee are still present, but they are unweighted.
What are the Symptoms of Malalignment in the Knee?
Over time, a malaligned knee starts to prematurely wear the cartilage that is being overloaded. This wearing of the coating cartilage on the ends of the bones (articular cartilage) is called osteoarthritis. On the medial or lateral side of the knee, the meniscus shock absorber cartilage prematurely tears as well. Meniscus tears further accelerate the arthritis. Patients commonly report locking, catching, swelling and pain with this cartilage wear and tear. The pain is often localized over that area of the knee that is being overloaded by malalignment.
What Are the Non-Surgical Treatments for Malalignment and the Arthritis Associated With It?
Please see Dr. Cunningham’s article on knee arthritis, but briefly, patients can take a non-steroidal anti-inflammatory medication. Natural anti-inflammatory supplements such as Curcumin or Turmeric can also be tried. Injections such as steroid, viscosupplementation, PRP, and stem cell may be considered. Physical therapy may be used to stretch out the contracted soft tissues. Finally, there are special knee braces that act to unweight the area of the knee being overloaded. These are called unloader braces.
How is Osteotomy Surgery Performed?
The anesthesiologist administers a general anesthetic in conjunction with a nerve block. The nerve block takes away most of the pain, such that patients do not have much pain when they awake from surgery. In surgery, the patient’s leg is sterilely prepped and draped. The affected bone is exposed through an incision. A live xray machine is used to position a specialized cutting guide on the bone. The bone is then cut using a precision saw blade. If a patient’s knee is in valgus (knock kneed), typically the osteotomy is made across the bottom of the femur bone. If a patient’s knee is in varus (bow legged), typically the osteotomy is made across the top of the tibia bone. After making the bone cut, the bone is gently wedged open a certain amount (10mm is a common amount of opening). For a valgus knee, the outer aspect of the femur bone is wedged open, thus unweighting the outside of the knee where there is arthritis and transferring more of the load to the inside of the knee where there is still good cartilage. For a varus knee, the inner aspect of the tibia bone is wedged open, thus unweighting the inside of the knee where there is arthritis and transferring more of the load to the outside of the knee where there is still good cartilage. Donor bone graft is placed in the void left by wedging the bone open. A special plate and screws are used to secure the bone’s new alignment while it heals. Unweighting the arthritic areas of the knee can alleviate much of the patient’s pain allowing them to resume the activities they enjoy.
For a knee cap that is maltracking to the outside of the knee, the portion of the tibia bone upon which the patellar tendon attaches is undercut and this bone is then slid toward the inside of the knee thus moving the knee cap into the center of groove so the patella tracks properly.
What is the Recovery Following Osteotomy Surgery?
Most osteotomies are done in an outpatient setting with patients able to go home the same day. Patients are instructed to ice and elevate the lower extremity. Pain medications are prescribed as well as an aspirin a day to serve as a blood thinner. Patients are placed in a telescoping knee brace and on crutches. It can be 6 weeks until patients are able to put full weight on the leg. Physical therapy is started immediately after surgery with patients being allowed to start gentle range of motion of the knee right away. At 8 weeks, there is some bone healing, but it can take several months for the bone to be solidly healed. It can also take 4-6 months for a patient to have full strength and be able to resume all sports. Dr. Cunningham is a knee surgeon at Vail Summit Orthopedics and Neurosurgery. He is an expert at diagnosing and treating a wide range of knee injuries for patients in Vail, Summit County, Aspen, and Denver, CO.