Perthes Disease: Causes, Symptoms, Diagnosis, and Treatment

What is Perthes Disease?

Perthes disease, also known as Legg-Calvé-Perthes disease (LCPD), is a rare childhood condition characterized by the temporary disruption of blood supply to the femoral head (the ball part of the hip joint), leading to the death of bone tissue (avascular necrosis) and subsequent bone collapse, revascularization, and reshaping.

Understanding Perthes Disease: A Core Definition

Perthes disease primarily affects children, typically occurring between the ages of 4 and 12, though it can manifest outside this range. It is significantly more common in boys than girls and usually affects only one hip (unilateral), but in about 10-15% of cases, both hips may be involved (bilateral), though not always at the same time.

From an anatomical and biomechanical standpoint, the femoral head is a critical component of the hip joint, articulating with the acetabulum (socket) of the pelvis to facilitate a wide range of motion. When the blood supply to this area is compromised, the bone cells die, leading to a weakening and potential collapse of the femoral head. Over time, the body attempts to repair this damage by revascularizing the area and laying down new bone. The ultimate shape and integrity of the femoral head after healing significantly impact the long-term function and health of the hip joint.

Etiology: What Causes Perthes Disease?

The exact cause of Perthes disease remains largely idiopathic, meaning unknown. However, several contributing factors and theories exist:

• Vascular Insufficiency: The most accepted theory points to a temporary interruption of the blood flow to the femoral head. This can be due to various reasons, including trauma, hypercoagulability (increased blood clotting), or repetitive microtrauma.
• Genetic Predisposition: While not directly inherited, there appears to be a familial component in some cases, suggesting a genetic susceptibility.
• Environmental Factors: Low birth weight, passive smoking, and certain socioeconomic factors have been weakly associated with an increased risk.
• Mechanical Stress: While not a direct cause, repetitive stress on a susceptible hip could potentially contribute to microtrauma and vascular disruption.

Clinical Presentation: Signs and Symptoms

The onset of Perthes disease can be insidious, with symptoms often developing gradually. From a kinesiologist's perspective, recognizing these signs is crucial for early referral and intervention:

• Limp: This is often the first noticeable symptom, which may be intermittent and can sometimes be painless initially. The limp typically worsens with activity.
• Pain: While the disease is sometimes painless ("silent Perthes"), pain is a common symptom. It is frequently reported in the groin, thigh, or knee (referred pain), rather than directly in the hip. This referred pain can sometimes lead to misdiagnosis.
• Reduced Range of Motion (ROM): As the femoral head deforms, the hip's ROM becomes restricted. This is particularly noticeable in:
  • Abduction: Moving the leg away from the body's midline.
  • Internal Rotation: Rotating the leg inward.
• Muscle Atrophy: Due to disuse and altered gait patterns, there may be noticeable wasting of the thigh and gluteal muscles on the affected side.
• Leg Length Discrepancy: In later stages, the affected leg may appear shorter due to the collapse of the femoral head.
• Stiffness: The hip joint may feel stiff, especially after periods of rest.

Diagnosis: Identifying Perthes Disease

Diagnosis involves a combination of clinical assessment and imaging studies:

• Physical Examination: A thorough examination will assess gait, hip ROM (especially abduction and internal rotation), muscle strength, and palpation for tenderness.
• Imaging Studies:
  • X-rays: Standard anteroposterior (AP) and frog-leg lateral views of the pelvis are the primary diagnostic tools. Early changes may be subtle, but over time, signs of collapse, fragmentation, and reossification become evident.
  • Magnetic Resonance Imaging (MRI): MRI is highly sensitive and can detect avascular necrosis much earlier than X-rays, often before bone changes are visible. It provides detailed images of soft tissues and blood supply.
  • Bone Scan: A bone scan can identify areas of decreased blood flow to the femoral head.

Staging and Classification

Perthes disease progresses through distinct stages, and various classification systems help clinicians assess the severity and predict prognosis:

• Waldenström Classification (Stages of Disease Progression):
  • Initial Stage: Density changes in the epiphysis, minimal collapse.
  • Fragmentation Stage: Femoral head begins to fragment and collapse. This is typically the most painful stage.
  • Reossification Stage: New bone formation occurs, and the femoral head begins to reform.
  • Healed Stage: The femoral head is fully reossified, though its shape may be deformed.
• Catterall Classification (Extent of Femoral Head Involvement): Categorizes the proportion of the femoral head affected, from Group I (anterior involvement only) to Group IV (entire femoral head involved). Higher groups generally indicate a worse prognosis.
• Herring Lateral Pillar Classification (Prognostic Indicator): This system, based on the height of the lateral pillar of the femoral head on an AP X-ray in the fragmentation stage, is widely used for prognosis:
  • Group A: No loss of lateral pillar height.
  • Group B: Lateral pillar height maintained at >50%.
  • Group B/C Border: Lateral pillar height maintained at 25-50%.
  • Group C: Lateral pillar height maintained at <25% or completely collapsed.

Management and Treatment Strategies

The primary goals of treatment are to maintain the sphericity of the femoral head, prevent further collapse, restore hip range of motion, and promote optimal healing. Treatment approaches vary widely based on the child's age, the stage of the disease, and the extent of femoral head involvement.

• Conservative Management:
  • Observation: For very young children or those with minimal involvement (e.g., Herring Group A), close monitoring and activity modification may be sufficient.
  • Activity Modification: Limiting high-impact activities like jumping, running, and contact sports is crucial during the active stages to reduce stress on the fragile femoral head.
  • Pain Management: Non-steroidal anti-inflammatory drugs (NSAIDs) can help manage pain and inflammation.
  • Physical Therapy: A cornerstone of conservative management, focusing on maintaining and improving hip range of motion, strengthening surrounding musculature, and ensuring proper gait mechanics.
  • Bracing/Casting: Abduction bracing (e.g., Scottish Rite brace, Atlanta brace) or casting may be used to contain the femoral head within the acetabulum, aiming to mold the healing femoral head into a more spherical shape.
• Surgical Intervention:
  • Osteotomy: Surgical procedures, such as femoral osteotomy (cutting and realigning the femur) or pelvic osteotomy (cutting and realigning the pelvis), are performed to improve the coverage of the femoral head by the acetabulum. This "containment" aims to guide the healing femoral head into a more spherical shape and prevent further deformity.
  • Indications for Surgery: Generally considered for older children (e.g., >8 years old) with significant femoral head involvement (e.g., Herring Group B/C or C) and poor prognostic factors, or when conservative measures fail.

Kinesiological Considerations and Rehabilitation

From an exercise science and kinesiology perspective, rehabilitation plays a vital role in optimizing outcomes for individuals with Perthes disease:

• Maintaining Range of Motion (ROM):
  • Passive and Active-Assisted ROM: Gentle, non-weight-bearing exercises are critical to prevent stiffness and contractures. Examples include supine hip flexion, abduction, and internal/external rotation within pain-free limits.
  • Aquatic Therapy: Water provides buoyancy, reducing joint load while allowing for greater freedom of movement, making it ideal for maintaining ROM and gentle strengthening.
• Strength Training:
  • Focus on Hip Stabilizers: Strengthening the hip abductors (gluteus medius, minimus), extensors (gluteus maximus, hamstrings), and core musculature is essential for joint stability and efficient movement patterns.
  • Isometric Exercises: Can be initiated early to activate muscles without joint movement.
  • Low-Load, Controlled Movements: Progress to exercises like glute bridges, clam shells, and controlled leg raises as tolerated. Avoid heavy weights or high-impact loading.
• Gait Retraining: Addressing compensatory limps and promoting a more symmetrical and efficient gait pattern is crucial. This may involve using crutches or walkers initially to reduce weight-bearing stress.
• Proprioception and Balance Training: As the hip joint's sensory input may be altered, incorporating balance exercises (e.g., single-leg standing, wobble board exercises) helps improve neuromuscular control and stability.
• Activity Modification and Safe Participation:
  • Educating patients and parents about which activities are safe during different stages of the disease is paramount.
  • High-impact activities (running, jumping, contact sports) should be avoided during the active stages.
  • Encourage low-impact activities like swimming, cycling (with appropriate bike fit), and elliptical training.
• Long-Term Exercise Prescription: Even after healing, individuals with Perthes disease may have a non-spherical femoral head, predisposing them to early osteoarthritis. Lifelong adherence to low-impact exercise and maintaining hip strength and mobility is crucial for joint preservation.

Prognosis and Long-Term Outlook

The prognosis for Perthes disease is highly variable and depends on several factors:

• Age at Onset: Younger children (under 6 years old) generally have a better prognosis because their bones have greater remodeling potential. Older children (over 8 years old) are at higher risk for significant deformity and poorer outcomes.
• Extent of Femoral Head Involvement: As indicated by classifications like Herring (Group A better than C) and Catterall (Group I better than IV), less involvement leads to better outcomes.
• Quality of Healing: The final shape of the femoral head after healing is the most important determinant of long-term function. A more spherical femoral head leads to better outcomes.
• Range of Motion: Maintaining good hip ROM throughout the disease course is associated with better outcomes.

Potential long-term complications include:

• Osteoarthritis: The most common long-term complication, occurring due to the altered biomechanics and irregular shape of the healed femoral head.
• Leg Length Discrepancy: May require shoe lifts or, in severe cases, surgical correction.
• Chronic Pain: Persistent hip pain can occur, especially with activity.
• Reduced Hip Function: Limited ROM and strength can impact daily activities and sports participation.

Regular follow-up with an orthopedic specialist is essential to monitor hip health and address any emerging issues throughout childhood and into adulthood.