Perthes disease is a condition that affects the hip in children between the ages of four and eight. The condition is also referred to as Legg-Calve-Perthes disease in honor of the three physicians who each separately described the disease. In this condition, the blood supply to the growth center of the hip (the capital femoral epiphysis) is disturbed, causing the bone in this area to die. The blood supply eventually returns, and the bone heals. How the bone heals determines what problems the condition will cause in later life. Perthes disease may affect both hips. In fact, 10 to 12 percent of the time the condition is bilateral (meaning that it affects both hips). This condition can lead to serious problems in the hip joint later in life.
What part of the hip is affected?
The capital femoral epiphysis is somewhat unique. It is one of the few epiphyses in the body that is inside the joint capsule. (The joint capsule is the tissue that surrounds the joint.) The blood vessels that go to the epiphysis run along the side of the femoral neck and are in danger of being torn or pinched off if something happens to the growth plate. This can result in a loss of the blood supply to the epiphysis.
Causes of Perthes Disease
How does this problem develop?
Children who have abnormal blood clotting (a condition called thrombophilia) may have a higher risk of developing Perthes disease. These children have blood that clots easier and quicker than normal. This may lead to blood clotting that blocks the small arteries going to the femoral head. As a result of new evidence, the certainty of thrombophilia as a cause of Perthes is now under debate. This will remain an area of study until scientists clear up the significance of thrombophilia as a possible cause of Perthes.
There is some new evidence that Perthes disease is genetic as a result of a mutation (abnormal change) in the type II collagen (fibers that make up soft tissue structures). Previously there was no known increase in risk for children whose parent had Perthes disease as a child. But this belief may no longer be accurate.
Studies among Asian families who have many members with this disease have been found with this mutation in the type II collagen gene. Scientists think that the mutation results in weakening of the hip joint cartilage that also affects the blood vessels within the cartilage.
Whatever the true cause of ischemia (lack of blood to the area), the result is bone death (called necrosis) of the femoral head. Without a normal blood supply, the bone loses its strength and shape. The loss of bone density and softening of the head result in a misshapen head. With the hip supporting the weight of the body, tiny microfractures in the soft, necrotic bone fail to heal. This is another reason why normal wear and tear results in deformity.
Symptoms of Perthes Disease
What does this problem feel like?
Most children with Perthes disease develop discomfort in the hip and walk with a limp. Children will not usually complain of pain unless specifically asked. The most common way that the disease is discovered is when someone, usually a parent, notices the limp and consults a physician.
When the doctor examines the hip, the motion of the hip is abnormal and restricted. Turning the leg inward produces pain. This usually indicates that the hip is inflamed and may have inflammatory fluid (called an effusion) present in the hip joint.
Interestingly, problems in the hip sometimes do not cause pain in the hip itself. The knee is where the pain is felt. This can be confusing both to patients and physicians. In general, a child with knee pain (who has no clear-cut reason to have knee pain), or an abnormal gait, should be examined for possible Perthes disease. This usually includes X-rays of the hips to make sure that Perthes disease is not missed.
In general, the most common problem later in life is the development of arthritis in the hip joint. The type of arthritis that develops in the hip is osteoarthritis (also known as wear and tear arthritis). Just like a machine that is out of balance, the hip joint wears out and becomes painful.
Diagnosis of Perthes Disease
How do doctors identify the problem?
The history and physical examination are usually enough to make the doctor highly suspicious about the diagnosis of Perthes disease. X-rays are usually necessary to make the diagnosis.
It is usually not necessary to get an MRI scan to make the diagnosis. However, this test may be useful to determine whether the other hip is involved in the disease. A special MRI using a dye called gadolinium may help show changes in blood supply before anything shows up on an X-ray.
In planning treatment another test, called an arthrogram, may be required. In this test, dye is injected into the hip joint to outline the cartilage surface of the joint. Much of the child’s hip joint is made up of cartilage. Cartilage does not usually show up on X-rays. The dye is necessary to see what the hip will actually look like when the cartilage turns to bone.
Treatment of Perthes Disease
What treatment options are available?
The primary goal of treatment for Perthes disease is to help the femoral head recover and grow to a normal shape. The closer to normal the femoral head is when growth stops, the better the hip will function in later life. The way that surgeons achieve this goal is using a concept called containment.
Containment is a simple concept. The femoral head can be molded as it heals. This is very similar to molding plastic. Plastic is poured into a molded and held in the mold as it cools. It then holds the shape of the mold. The hip socket, or acetabulum, is not affected when the femoral head loses its blood supply. It can be used as a mold to shape the femoral head as it heals. The trick is that the femoral head must be held in the joint socket (acetabulum) as much as possible. It is better if the hip is allowed to move and is not held completely still in the joint socket. Joint motion is necessary for nutrition of the cartilage and for healthy growth of the joint.
All treatment options for Perthes disease try to position and hold the hip in the acetabulum as much as possible. This healing process can take several years.
Many children who are diagnosed with Perthes disease do not require any treatment except careful watching. When the condition is mild, the results of not doing anything are often as good as aggressive treatment. The majority of children who are treated for Perthes disease these days require only a program for maintaining a near-normal range of motion. This may include nighttime splinting, home traction, and physical therapy. The surgeon will determine treatment based on the classification of the severity of the disease. The classification is determined by the X-ray findings.
Hip motion, as near to normal as possible, is critical to the successful treatment of Perthes disease. The disease causes inflammation in the joint. This leads to loss of motion and contracture (tightening) of the muscles surrounding the hip joint. Treating these problems to restore normal motion is common.
Anti-inflammatory medications may be prescribed. Antiresorptive agents may also protect the bone and help decrease deformity. Studies are being done to fully test the effect of these medications in children with Perthes.
Physical therapy is used to restore the hip motion as the inflammation comes under control. This process usually takes about a week. Home traction may also be an option.
In some cases, surgery will be required to obtain adequate containment. Sometimes, adequate motion cannot be regained with traction and physical therapy alone. If the condition is longstanding, the muscles may have contracted or shrunk and cannot be stretched back out. To help restore motion, the surgeon may recommend a tenotomy of the contracted muscles. When a tenotomy is performed, the tendon of the muscle that is overly tight is cut and lengthened. This is a simple procedure that requires only a small incision. The tendon eventually scars down in the lengthened position, and no functional loss is noticeable.
Surgical treatment for containment usually consists of procedures that realign either the femur (thighbone), the acetabulum (hip socket), or both.
In severe cases, both femoral osteotomy and pelvic osteotomy may be combined to obtain even more containment.
Rehabilitation of Perthes Disease
What should I expect from treatment?
Follow-up visits are used to monitor the symptoms, hip mobility, and to make sure that the condition is not deteriorating. The surgeon will take X-rays during the recheck visits to follow the healing of the femoral head.
Patients with Perthes disease are always at higher risk of developing osteoarthritis of the hip. The end result is that most patients with Perthes disease will require an artificial hip at some point in the future. Most patients do not develop problems for 40 years or more. How soon patients have problems with their hip is directly related to how much deformity is present once the condition heals. In general, the more round the femoral hip is at that time, the longer the hip will stay free of pain.