Legg-Calvé-Perthes Disease (Coxa Plana): Understanding Symptoms, Causes, Diagnosis, and Treatment

What is another name for coxa plana?

Coxa plana is most commonly known as Legg-Calvé-Perthes disease, or simply Perthes disease. It is a rare childhood condition affecting the hip joint, where the blood supply to the femoral head is temporarily disrupted, leading to bone death and collapse.

Understanding Legg-Calvé-Perthes Disease (Coxa Plana)

Legg-Calvé-Perthes disease (LCPD) is a pediatric hip disorder characterized by avascular necrosis of the femoral head. This means that the blood supply to the ball of the hip joint (the femoral head) is interrupted, causing the bone cells to die. Over time, the dead bone weakens and can collapse, leading to a flattened or deformed femoral head, which is where the term "coxa plana" (Latin for "flat hip") originates.

The condition typically affects children between 4 and 10 years of age, with a higher incidence in boys (approximately four to five times more common than in girls). While it can affect one or both hips, it is unilateral in about 80-90% of cases. The disease progresses through several phases:

• Initial Phase: Interruption of blood supply and death of bone cells.
• Fragmentation Phase: The dead bone is reabsorbed by the body, and the femoral head begins to fragment and flatten.
• Reossification Phase: New bone begins to form, and the femoral head starts to heal.
• Healed Phase: The bone is fully reossified, but the shape of the femoral head may be permanently altered.

The primary goal of treatment is to maintain the spherical shape of the femoral head as it heals, ensuring it fits well within the hip socket (acetabulum) to prevent long-term complications like osteoarthritis.

Causes and Risk Factors

The exact cause of Legg-Calvé-Perthes disease remains idiopathic, meaning unknown. However, researchers have identified several potential contributing factors and risk associations:

• Genetic Predisposition: While not directly inherited in a simple Mendelian pattern, there may be a genetic component that increases susceptibility.
• Blood Clotting Abnormalities: Some studies suggest an association with hypercoagulable states, where the blood is more prone to clotting, potentially blocking blood flow to the femoral head.
• Environmental Factors: Exposure to passive smoke has been linked to an increased risk.
• Trauma: While not a direct cause, minor trauma might trigger or exacerbate symptoms in a susceptible child.
• Growth and Development: Children with LCPD often have a slightly delayed bone age and may be smaller than their peers.

Symptoms and Clinical Presentation

The symptoms of Legg-Calvé-Perthes disease can vary in severity and often develop gradually. Common signs include:

• Limp: This is often the first noticeable symptom, especially after activity.
• Pain: Pain may be felt in the hip, groin, thigh, or even referred to the knee. It often worsens with activity and improves with rest.
• Limited Range of Motion: Stiffness and reduced movement in the affected hip, particularly difficulty with abduction (moving the leg away from the body) and internal rotation.
• Muscle Atrophy: Wasting of muscles in the affected thigh and buttock due to disuse.
• Leg Length Discrepancy: In some cases, the affected leg may appear shorter than the unaffected leg if the femoral head collapses significantly.

Diagnosis of Legg-Calvé-Perthes Disease

Diagnosing LCPD typically involves a combination of a thorough medical history, physical examination, and imaging studies:

• Physical Examination: The physician will assess the child's gait, hip range of motion, and look for signs of pain or muscle atrophy.
• X-rays: Initial X-rays of the hips, often including an AP (anterior-posterior) view and a "frog-leg lateral" view, are crucial. Early changes may be subtle, but as the disease progresses, fragmentation and flattening of the femoral head become visible.
• Magnetic Resonance Imaging (MRI): MRI is highly sensitive and can detect early changes in blood flow and bone necrosis even before they are visible on X-rays. It also provides a detailed view of the extent of involvement.
• Bone Scans: A technetium bone scan can show areas of decreased blood flow, which may indicate avascular necrosis.

Differential diagnosis is important to rule out other conditions with similar symptoms, such as transient synovitis, septic arthritis, or slipped capital femoral epiphysis.

Treatment and Management Strategies

The primary goals of treatment for Legg-Calvé-Perthes disease are to relieve pain, maintain a good range of motion in the hip, and preserve the spherical shape of the femoral head as it reossifies. Treatment approaches depend on the child's age, the extent of femoral head involvement, and the stage of the disease.

Non-Surgical Management:

• Activity Modification: Limiting high-impact activities and weight-bearing on the affected hip, often involving crutches or a wheelchair during acute phases.
• Pain Management: Non-steroidal anti-inflammatory drugs (NSAIDs) can help manage pain and inflammation.
• Physical Therapy: Crucial for maintaining hip mobility, strengthening surrounding muscles, and preventing stiffness. Exercises focus on range of motion, strengthening, and sometimes traction.
• Bracing/Casting: Historically, braces (e.g., Scottish Rite brace) were used to keep the femoral head contained within the acetabulum. While less common now, they may still be considered in specific cases.

Surgical Management:

Surgery is considered when non-surgical methods fail to maintain femoral head containment or if there's significant deformity.

• Osteotomy: This involves cutting and realigning the bone to improve the coverage of the femoral head by the acetabulum.
  • Femoral Osteotomy: Cutting and reshaping the femur.
  • Pelvic Osteotomy: Cutting and reshaping the pelvis.
• Other Procedures: In some severe cases, procedures like débridement (removing dead bone) or articular cartilage repair might be considered.

Prognosis and Long-Term Outlook

The long-term prognosis for children with Legg-Calvé-Perthes disease varies significantly depending on several factors:

• Age at Onset: Younger children (under 6 years old) generally have a better prognosis because their bones have more growth potential and remodeling capacity.
• Extent of Femoral Head Involvement: The more of the femoral head that is affected by avascular necrosis, the worse the prognosis tends to be.
• Joint Congruity: Maintaining a spherical femoral head that fits well within the acetabulum is key to preventing long-term complications.
• Treatment Adherence: Consistent adherence to prescribed treatments and activity modifications can significantly impact outcomes.

Despite successful healing, some individuals may develop early onset osteoarthritis in the affected hip later in life due to residual deformity or incongruity of the joint surface. Regular follow-up with an orthopedic specialist is essential to monitor hip health.

Implications for Exercise and Rehabilitation

For individuals with a history of Legg-Calvé-Perthes disease, exercise and rehabilitation play a vital role in recovery and long-term joint health.

• Acute Phase: During the active disease and healing phases, the focus is on protecting the hip. Non-weight-bearing exercises like swimming or cycling (with low resistance) are often recommended to maintain cardiovascular fitness and muscle strength without stressing the healing hip.
• Maintaining Mobility: Consistent range of motion exercises are critical to prevent stiffness and contractures. This includes gentle stretches and active movements of the hip.
• Strengthening: Once appropriate, strengthening exercises for the muscles surrounding the hip (e.g., gluteal muscles, core stabilizers, quadriceps, hamstrings) are important for providing support and stability to the joint.
• Avoiding High-Impact Activities: Even after healing, high-impact sports or activities that place excessive stress on the hip joint (e.g., long-distance running, jumping sports) may need to be limited or modified, especially if there's residual deformity.
• Proprioception and Balance: Exercises that improve balance and proprioception (the body's awareness of its position in space) can help improve functional movement patterns and reduce the risk of further injury.
• Individualized Programs: Exercise programs should always be designed and supervised by a qualified physical therapist or exercise physiologist who understands the specific history and current status of the individual's hip.

Conclusion

Coxa plana, more formally known as Legg-Calvé-Perthes disease, is a complex pediatric hip condition that requires careful diagnosis and management. While its exact cause remains elusive, understanding its progression and the importance of preserving the femoral head's shape is paramount. Early diagnosis, appropriate treatment, and consistent rehabilitation are crucial for optimizing outcomes and minimizing the long-term impact on hip function and overall quality of life. For fitness enthusiasts, trainers, and kinesiologists, recognizing the history of LCPD in clients is essential for designing safe, effective, and joint-preserving exercise programs.