Knee osteotomy
Definition
Knee osteotomy is surgery that removes a part
of the bone of the joint of either the bottom of the femur (upper leg bone) or
the top of the tibia (lower leg bone) to increase the stability of the knee.
Osteotomy redistributes the weight-bearing force on the knee by cutting a wedge
of bone away to reposition the knee. The angle of deformity in the knee dictates
whether the surgery is to correct a knee that angles inward, known as a varus
procedure, or one that angles outward, called a valgus procedure. Varus
osteotomy involves the medial (inner) section of the knee at the top of the
tibia. Valgus osteotomy involves the lateral (outer) compartment of the knee by
shaping the bottom of the femur.
Purpose
Osteotomy surgery changes
the alignment of the knee so that the weight-bearing part of the knee is shifted
off diseased or deformed cartilage to healthier tissue in order to relieve pain
and increase knee stability. Osteotomy is effective for patients with arthritis
in one compartment of the knee. The medial compartment is on the inner side of
the knee. The lateral compartment is on the outer side of the knee.
The
primary uses of osteotomy occur as treatment for:
• Knee deformities such as
bowleg in which the knee is varus-leaning (high tibia osteotomy, or HTO) and
knock-knee (tibial valgus osteotomy), in which the knee is valgus leaning.
• A torn anterior cruciate ligament (ACL), which is a set of ligaments
that connects the femur to the tibia behind the patella and offers stability to
the knee on the left-right or medial-lateral axis. If this ligament is injured,
it must be repaired by surgery. Many ACL injuries cause inflammation of the
cartilage of the knee and result in bones extrusions, as well as instability of
the knee due to malalignment. Osteotomy is performed to cut cartilage and
increase the fit and alignment of the ends of the femur and tibia for smooth
articulation. As one very common knee injury that often occurs in athletic
activity, HTO is often performed when ACL surgery is used to repair the
ligament. The combination of the two surgeries occurs primarily in young people
who wish to return to a highly athletic life.
• Osteoarthritis that
includes loss of range of motion, stiffness, and roughness of the articular
cartilage in the knee joint secondary to the wear and tear of motion, especially
in athletes, as well as cartilage breakdown resulting from traumatic injuries to
the knee. Surgery for progressive osteoarthritis or injury-induced arthritis is
often used to stave off total joint replacement.
Demographics
According to Healthy People 2000, Final Review,
published by the Centers for Disease Control and Prevention, the various forms
of arthritis the leading cause of disability in the United States affect more
than 15% of the total U.S. population (43 million persons) and more than 20% of
the adult population. Osteoarthritis (OA) is the most common form of knee
arthritis and involves a slowly progressive degenerative disease in which the
joint cartilage gradually wears away. It most often affects middle-aged and
older people. The most common source of ACL injury is skiing. Approximately
250,000 people sustain a torn or ruptured ACL in the United States each year.
Research indicates that ACL injuries are on the rise in the United States due to
the increase in sport activity.
Description
Osteotomy is performed
as open surgery to the knee assisted by pre-operative arthropscopic diagnostic
techniques. Surgery takes place on the tibia end or the femoral end at the knee
according to whether the malalignment to be corrected is varus, or inward
leaning, or valgus, outward leaning. The surgery involves the gaping or wedging
of a piece of bone and its removal to change the pressure points of
weight-bearing activity. The cut surfaces of the bone are held together with two
staples, or a plate and screws. Other devices may be used, especially in tibial
osteotomy where a fracture is involved. After surgery, a small plastic suction
drain is left in the wound during recovery and early postoperative
hospitalization.
Diagnosis / Preparation
Severe or chronic pain
and/or knee instability brings the patient to an orthopedic physician. From
there, the decision is made for surgery or for rehabilitation. Patients will
undergo an examination and history with their physician. Once rehabilitation or
other treatments are ruled out and surgery is indicated, the physician must
assess for three factors: pain, instability, and knee alignment. Osteotomy is
indicated if malalignment is a factor. Debridement, or the shaving of cartilage
on the articulate femur or tibia, can usually resolve pain with instability
problems. It must be determined whether the instability is related to
malalignment and not to other sources such as ACL injury.
Since the goal
of osteotomy is to shift weight from a symptomatic cartilage to an unsymptomatic
area to relieve both an instability and pain due to excessive contact, alignment
of the knee is assessed for pressure distribution along the mechanical axis and
the loading axis. This requires an analysis of gait pattern, range of motion,
localized areas of pain, and neurological factors, as well as other technical
tests for anterior instability. A diagnostic arthroscopy - examination of the
knee joint with a long tube attached to a video camera - is usually indicated
before all knee osteotomies. Cartilage surfaces are examined for degenerative or
late-stage arthritis. Magnetic resonance imaging (MRI) is useful in evaluating
any intra-articular pathology such as bone chips, padding tears, or injuries to
ligaments.
Aftercare
After surgery, patients are placed in a hinged
brace. Toe-touching is the only weight-bearing activity allowed for four weeks
in order to allow the osteotomy to hold its place. Continuous passive motion is
begun immediately after surgery and physical therapy is used to establish full
range of motion, muscle strengthening, and gait training. After four weeks,
patients can begin weight-bearing movement. The brace is worn for eight weeks or
until the surgery site is healed and stable. X rays are performed at intervals
of two weeks and eight weeks after surgery.
Risks
The usual general
surgical risks of thrombosis and heart attack are possible in this open surgery.
Osteotomy surgery itself involves some risk of infection or injury during the
procedure. Combined surgery for ACL and osteotomy has higher morbidity rates.
Normal results
Varus malalignment correction with osteotomy through
the high tibia (HTO) is a proven and satisfactory operation. Success rates are
high when the patient has a small angle deformity (<10°). Knees with more
severe deformity have less satisfactory results. Tibial osteotomy for the less
common valgus deformity is less satisfactory. Research indicates that only a few
individuals are able to return to their previous level of high sports activity
after a knee osteotomy, whether done with an ACL repair or not. However, more
than half of patients in one study were able to return to leisure sports
activities. Reports also indicate that those individuals who had osteotomy
without ACL reconstruction had no differences in results with respect to
measures of stability. It may take up to a year for the knee to be fully aligned
and adapted to its new position after surgery. Most patients, more than 50%,
gain stability and are able to walk further than they could walk before
osteotomy. However, according to one report, 13% of patients had severe pain or
needed a total knee replacement after five years. In one European review, the
results were better. Osteoarthritis was arrested in 105 cases (69%), with 47
cases showing deterioration. The main factors associated with further
deterioration were insufficient correction and persistence of malalignment.
Morbidity and mortality rates
Morbidity rates include bleeding,
inflammation of joint tissues, nerve damage, and infection.
Alternatives
For those individuals suffering from osteoarthritis, muscle-strengthening
exercise, weight loss, and rehabilitation can be helpful in relieving pain and
gaining stability. Anti-inflammatory medications can also be effective in
helping pain and stability. For severe varus or valgus deformities, osteotomy or
knee replacement may be indicated. For those with severe ACL injury with
secondary trauma to knee cartilage, complete knee replacement may be suggested.
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