Introduction:
The skeleton or the bones provide the structural framework for the human body. A good blood supply to the bones is essential to maintain their integrity, size, shape, and structure. A compromised blood supply to the bone usually results in bone loss or tissue necrosis (death), thereby causing temporary or permanent loss of function. Bone diseases may be congenital or acquired and vary depending on the site affected. Legg-Calve-Perthes disease is a childhood condition primarily affecting the hip bones.
What Is Legg-Calve-Perthes Disease?
Legg-Calve-Perthes disease is a rare condition affecting children between four to ten years of age. As widely known, Perthes disease occurs when the blood supply to the hip joint is temporarily affected. The joint where the hip connects the leg to the trunk of the body is known as the hip joint, and it primarily comprises the thigh bone, pelvic bone, and hip joint. The hip joint, also known as the ball and socket joint, is the region where the head of the thigh bone inserts into a socket formed by the pelvic bone. This joint aids in leg motion and provides stability to the entire body.
When the blood supply to the thigh bone is affected, it results in necrosis of the hip joint. This results in weakened bone; eventually, the joint loses its shape and may even fracture. However, the body tends to restore the blood supply to the joint, and bone healing may occur, but the shape is compromised. The ball joint of the hip tends to reform in different shapes, but they no longer move or fit smoothly into the pelvic socket. This results in pain, stiffness, and limited mobility, thus compromising the quality of life. Progressively it may result in degenerative bone diseases such as osteoarthritis.
What Causes Legg-Calve-Perthes Disease?
A temporary disruption of blood supply to the thigh bone is the most common cause of Legg-Calve-Perthes disease. However, the reason for the loss of blood supply is not clearly defined. Few studies indicate a genetic association, while others suggest trauma and increased physical activity as contributing factors. This condition is also very commonly observed in children who have been subjected to second-hand smoke.
What Are the Risk Factors Associated With Legg-Calve-Perthes Disease?
The risk factors associated with Legg-Calve-Perthes disease are mentioned below:
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Age: Though Legg-Calve-Perthes disease can affect any age group, it is most commonly found in children between four and ten years old.
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Sex: This disease is mainly found in boys as compared to girls.
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Race: This condition is more commonly found in white children.
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Family History: Research has shown that children whose parents are positive for the disease are more likely to inherit the condition.
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Genetic Mutations: Certain studies indicate that children with genetic mutations can develop this disease.
What Are the Symptoms of Legg-Calve-Perthes Disease?
Signs and symptoms of this condition are:
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Limping or limited mobility.
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Pain and stiffness in the hip joint, thigh, or legs.
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Decreased mobility of the hip joint.
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Muscle spasm.
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Physical activity worsens the pain while rest improves.
What Are the Complications Associated With This Condition?
The most common complication of Legg-Calve-Perthes disease is the risk of developing osteoarthritis of the hip joint in adulthood. The younger the child at the time of diagnosis, the lower the risk of developing any complications, as the bone tends to heal better and assume standard shape. Hip problems are more common if the child is diagnosed after six years of age. Late diagnosis results in abnormal healing and shape and early wear out of the bone. The concerned leg may lose some of its function and may even be shorter than its normal counterpart.
When to Seek Medical Help?
Seek emergency care if the child complains of the following symptoms:
What Are the Stages of Legg-Calve-Perthes Disease?
There are four phases in this condition:
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Phase 1 (Necrosis) - When the blood supply to the hip joint is hindered, it results in necrosis (dead bone tissue). Swelling and pain are the most common symptoms associated with this phase. This phase may last for several months to a year.
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Phase 2 (Fragmentation) - The body produces certain scavenger cells that clean the dead tissue and replace them with new healthy bone cells. The bone begins to assume its original shape, and this phase may last up to two years. Pain may still be present.
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Phase 3 (Reossification) - The blood flow to the bone and joint is restored, and the bone ossifies, ultimately assuming its original ball shape. This phase may last up to three years.
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Phase 4 (Remodeling) - Complete bone healing occurs.
How Is Legg-Calve-Perthes Disease Diagnosed?
The diagnostic workup for Legg-Calve-Perthes disease is as mentioned below:
1. Physical Examination and Medical History: A pediatric orthopedist can assess the symptoms of the child, such as the movements of the hip, rotation of the leg, range of motion, and pain. The leg will be moved into various positions to assess the range of motion and pain. This condition primarily limits the movement of the leg away from the body and the internal rotation of the leg.
2. Radiography: X-rays are the preferred diagnostic tool to detect bone diseases. They are efficient, quick, and noninvasive. X-rays are highly beneficial in staging the disease and assessing complications such as osteoarthritis in the bone.
Early radiographic findings of the disease are:
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Decreased size of the femoral head (thigh bone)
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Increased density of the femoral head.
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Collapse and separation of the necrosed bone.
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A slight widening of the joint space.
Late radiographic findings of the disease are:
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Delayed bone maturation, along with a radiolucent crescent line, indicates a subchondral fracture.
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Femoral head fragmentation.
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Femoral neck cysts due to intramedullary bleeding.
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The femoral head becomes wider and flatter, representing the remodeling phase.
3. Computed Tomography (CT): Though CT is more sensitive than plain radiographs in diagnosing Legg-Calve-Perthes disease, it is not widely recommended considering the side effects of radiation. Early bone collapse, sclerosis, and even subtle changes in the bone pattern can be precisely observed in CT.
4. Magnetic Resonance Imaging (MRI): MRI uses magnetic fields and radio waves to produce images of the bone and soft tissues. MRI is more precise in evaluating the shape, size, and position of the femoral head and its associated soft tissues.
5. Nuclear Imaging: A radionuclide scanning involving technetium-99m diphosphonate also plays an essential role in diagnosing Legg-Calve-Perthes disease. The uptake is initially decreased in the femoral head because of disrupted blood supply. However, the uptake is later increased due to revascularization, bone repair, and degenerative changes.
6. Ultrasonography: Ultrasound though not routinely recommended, is the best available tool for staging the disease and observing its course. Negligible radiation and low-cost render ultrasound the most effective diagnostic tool for the follow-up of patients. It also helps in sonography-aided aspiration of the joint fluid for laboratory analysis. Based on the ultrasound features, a 4-part staging reflecting the degree of flattening and fragmentation and the remodeling of the femoral head has been proposed.
7. Angiography: Angiography is rarely performed. It may show interruption and a decrease in blood supply in the early stages. Revascularized osseous segments may characterize the progressive disease.
8. Arthrography: Arthrography is an imaging procedure specific to the joints. A contrast material is injected into the joint and imaged using an x-ray or MRI. MR arthrogram is mainly preferred.
Conclusion:
Legg-Calve-Perthes disease is an uncommon childhood condition that usually carries a good prognosis if diagnosed and treated earlier. The two most crucial factors determining the outcome are the age of onset of treatment (ideally, the younger, the better) and the severity of damage to the femoral head. Several studies suggest that a few children may need hip replacement therapy later. Imaging is vital not only to diagnose but also in the follow-up of patients affected with Legg-Calve-Perthes disease.
