Perthes Disease

Perthes disease is a childhood hip condition where blood supply to the ball-shaped head of the thigh bone is temporarily interrupted, causing the bone to break down and then gradually heal over several years.

Table of contents

• What is Perthes disease?
• Disease identification codes and names
• Affected parts of the body
• Who gets Perthes disease?
• Signs and symptoms
• What causes Perthes disease?
• The four stages of Perthes disease
• How is Perthes disease diagnosed?
• Treatment options
• Long-term outlook

What is Perthes disease?

Perthes disease is a childhood condition that affects the hip joint. It occurs when the blood supply to the rounded head of the thigh bone (the part that fits into the hip socket) is temporarily disrupted^[1]. Without an adequate blood supply, the bone cells cannot get oxygen and nutrients, so they begin to die^[2]. This process is called avascular necrosis, which means bone death due to lack of blood flow^[3].

As the condition progresses, the weakened bone at the top of the thigh bone (called the femoral head) gradually begins to collapse and break apart^[2]. Over time, the blood supply returns to the bone and it begins to grow back. The body removes the dead bone cells and replaces them with new bone^[5]. However, during this healing process, the shape of the femoral head can change and become flattened or misshapen rather than staying round^[3].

The hip is a ball-and-socket joint. The rounded head of the thigh bone (femur) fits into a cup-shaped socket (called the acetabulum) in the hip bone^[1]. For the hip to move properly and without pain, the ball needs to stay round and fit smoothly into the socket^[2]. Treatment for Perthes disease focuses on helping the bone grow back into a shape that is as round as possible, so the hip joint can move normally and prevent problems in adulthood^[2].

Disease identification codes and names

Legg-Calve-Perthes disease, Legg-Perthes disease, LCPD, coxa plana, aseptic necrosis of the capital femoral epiphysis, osteochondrosis of the capital femoral epiphysis

The disease is named after the three doctors who first described the condition: Legg, Calvé, and Perthes^[2].

Affected parts of the body

• Hip joint
• Femur (thigh bone)
• Femoral head (ball-shaped top of the thigh bone)
• Acetabulum (hip socket)

Who gets Perthes disease?

Perthes disease is a rare condition that most commonly affects children between the ages of 4 and 10 years, though it can occur in children as young as 2 or as old as 15^[2][3]. The condition is most often diagnosed between ages 5 and 7^[3]. About one out of every 12,000 children develop Perthes disease^[5].

Boys are much more likely to develop Perthes disease than girls. The condition affects boys about five times more often than girls^[2][5]. However, when girls do develop the condition, it tends to be more severe^[5].

Children with Perthes disease are often very physically active and tend to be small for their age^[5]. The condition appears to be more common in children who have been exposed to second-hand smoke^[5].

In most cases, only one hip is affected. However, in about 10 to 15 percent of children with the condition, both hips are involved, though usually not at the same time^[2][5].

Signs and symptoms

The first signs of Perthes disease are often quite subtle. Many children begin walking with a limp before they even notice any pain^[3]. Parents typically first notice that their child walks with a limp or complains of pain^[1]. When questioned, the child usually cannot remember injuring the hip^[14].

Common symptoms include^[1][3][4]:

• Limping, which may be painless at first
• Pain or stiffness in the hip, groin, thigh, or knee
• Limited range of motion in the hip joint
• Pain that gets worse with activity and improves with rest
• Difficulty rotating the hip, especially turning the leg inward or spreading the legs apart
• Leg cramps or muscle spasms in the muscles connected to the hip

As the condition progresses, later symptoms may develop^[3]:

• Thinner thigh muscles on the affected leg (called muscle atrophy) from lack of use
• One leg appearing shorter than the other
• An unusual walking pattern where the pelvis tilts down on the affected side
• Worsening pain and limping over time

It is important to note that pain from the hip may be felt in other areas, a phenomenon called referred pain. Some children feel pain in their knees, thighs, pelvis, or belly instead of in the hip itself^[3][6]. Because of this, any complaints of persistent hip or knee pain should be evaluated by a doctor^[14].

What causes Perthes disease?

The exact cause of Perthes disease is not known^[1][5]. What doctors do know is that the condition happens when something disrupts or stops the blood supply to the head of the thigh bone^[1][4]. Without blood flow, the bone cannot receive oxygen and nutrients, so the bone cells die^[4].

Blood flow can be interrupted if a blood vessel is blocked or squeezed^[3]. A blood clot or artery disease might block the vessel from inside. Swelling around the hip from sudden trauma or repeated strain injury might compress a blood vessel from the outside, cutting off blood flow^[3].

Some researchers have suggested that the condition is multifactorial, meaning it is caused by a combination of factors including genetics, lifestyle, environment, and metabolism^[8]. Joint stress, blood clotting problems, poor nutrition, obesity, and exposure to cigarette smoke may all contribute to the development of Perthes disease^[8].

With current medical knowledge, Perthes disease cannot be prevented^[4].

The four stages of Perthes disease

Perthes disease is really a complex process that progresses through four distinct stages. The complete process of bone death, breakdown, and healing can take several years^[1][2].

Stage 1: Initial stage or Necrosis

In this stage, the blood supply to the femoral head is disrupted and bone cells begin to die^[2][5]. The hip joint becomes inflamed and irritated, and the area becomes intensely swollen^[2]. Your child may begin to show signs of the disease, such as limping or walking differently^[2]. On x-rays, the femoral head may appear smaller and less round^[5]. This initial stage may last from several months up to one year^[2][5].

Stage 2: Fragmentation

Over a period of 6 months to 2 years, the body removes the dead bone and quickly replaces it with softer, new bone^[2][5]. It is during this phase that the bone is in a weaker state and the head of the femur is at greatest risk of collapsing into a flatter position^[2]. The femoral head in this stage may look like it is breaking into different pieces on x-rays^[2][5]. The joint is usually irritated and painful, and limping is common^[7].

Stage 3: Reossification

In this stage, new, stronger bone develops and begins to take shape in the head of the femur^[2]. The femoral head continues to remodel itself back into a round shape once blood flow is restored^[5]. The reossification stage is often the longest stage of the disease and can last from one to three years^[2][5].

Stage 4: Healed or Remodeling

In this final stage, bone regrowth is complete, and the femoral head has reached its final shape^[2]. Normal bone cells replace the new bone cells^[5]. How close the shape is to round will depend on several factors, including the severity of the blood supply interruption and how much the bone was used during the earlier stages when it was weak^[2][3]. This phase can last a few years as the bone continues to heal and remodel^[5].

How is Perthes disease diagnosed?

Diagnosis of Perthes disease involves several steps. Your doctor will want to understand your child’s medical history and will ask when you first noticed the symptoms, what makes them worse or better, and if there are any other health issues^[4].

During a physical examination, the doctor will move your child’s legs through their range of motion to check for stiffness and to see which positions cause pain^[4][9]. This helps identify any movements that are limited or uncomfortable.

Several imaging tests are vital for diagnosing Perthes disease^[9]:

X-rays are the most common imaging test used. However, initial x-rays may not show changes in the hip right away. It can take 1 to 2 months after symptoms begin for the changes related to Perthes disease to become clear on x-rays^[9]. Your doctor will likely recommend several x-rays over time to track how the disease is progressing^[9].

MRI (Magnetic Resonance Imaging) uses radio waves and a strong magnetic field to create very detailed images of bone and soft tissue inside the body^[9]. MRI scans can often show bone damage caused by Perthes disease more clearly than x-rays, though they are not always needed^[9].

Other tests that may be used include^[4]:

• Bone scans
• Ultrasound
• Blood tests to rule out infection

These tests help give your doctor a complete picture of what is happening inside your child’s hip joint^[4].

Treatment options

The goal of treatment is to help the femoral head grow back into a shape that is as round as possible, so the hip joint can move normally and prevent problems later in life^[2][9]. Treatment recommendations depend on the child’s age when symptoms began, the stage of the disease, and the amount of hip damage^[9].

Treatment for children under age 6

Most children who are diagnosed with Perthes disease before age 6 have a favorable long-term outcome regardless of treatment^[16]. Most doctors recommend activity restrictions, avoiding high-impact activities like running and jumping, while still allowing swimming and biking^[4][16]. Physical therapy may be recommended to help with stretching and to minimize muscle weakness^[16]. Anti-inflammatory medications may be used occasionally to help decrease pain, though daily use may hinder bone formation^[16].

In more serious cases with a very stiff hip, surgery may be recommended, which might involve cutting a tight tendon in the groin (called a tenotomy) followed by placing the child in special casts that help increase hip mobility^[16].

Treatment for children ages 6 to 8

This age group has the greatest variety in treatment options and outcomes^[16]. Milder cases may be treated with activity restrictions, physical therapy, and anti-inflammatory medication. Temporary bed rest or decreased weight-bearing with a wheelchair or crutches can also help reduce pressure on the hip^[16].

In more moderate cases with a very stiff hip, soft tissue surgery to increase hip joint mobility and casting may be recommended^[16].

Many children in this age group benefit from more extensive surgery called an osteotomy, which involves cutting one of the bones around the hip to reposition it for better healing^[16]. The goal is to keep the ball part of the joint held snugly in the socket, which acts as a mold to help the fragmented femoral head heal in a rounder shape^[1][9]. An osteotomy can be done either on the thigh bone (femoral osteotomy) or on the hip socket bone (pelvic osteotomy)^[16]. Plates and screws are commonly used to hold the cut bones in place, and a cast may be placed to protect the surgery area^[16].

Treatment for children age 8 and older

Children diagnosed at age 8 or older often have more severe disease and worse outcomes^[16]. These children typically require surgical treatment to try to improve the outcome. The types of surgery used are similar to those for younger children but may need to be more extensive^[16].

Non-surgical treatments

Non-surgical approaches include wearing a special type of leg brace or cast that spreads the legs widely apart to keep the ball portion of the hip joint snugly positioned in the socket^[9]. Physical therapy helps maintain range of motion and strengthen muscles. Activity restrictions help protect the weakening bone from further collapse.

The healing process can take anywhere from 18 to 24 months of treatment, and in some cases several years^[2][4].

Long-term outlook

The long-term outlook for children with Perthes disease is generally good in most cases^[2]. After treatment, most children return to daily activities without major limitations^[2]. Most children with Perthes disease eventually recover, but it can take anywhere from 2 to 5 years for the femoral head to regrow and return to normal or close to normal^[4][18].

The final outcome depends on several factors. The age at which the child developed the disease is important—younger children tend to have better outcomes because they have more time for the bone to remodel and grow^[2]. The severity of involvement also matters; children with less of the femoral head affected generally do better than those with more extensive damage.

Without proper treatment, the femoral head may heal in a flattened or misshapen form rather than staying round^[1][14]. If the femoral head does not heal in a round shape, it may not fit properly in the hip socket, which can lead to problems. An improperly shaped femoral head can cause the hip to wear out more quickly, leading to pain and stiffness^[1].

Some people with poorly healed Perthes disease may develop osteoarthritis (a painful joint disorder where the cartilage in the joint breaks down) in mid-adult life^[2][5]. In severe cases, a hip replacement may be needed later in life^[14].

It is important to see a doctor if your child begins limping or complains of hip, groin, or knee pain^[1]. If your child has a fever or cannot bear weight on the leg, seek emergency medical care immediately^[1].