Legg-Calve-Perthes Disease

Etiology

The cause of Legg-Calve-Perthes disease is not known. It may be idiopathic or due to other etiology that would disrupt blood flow to the femoral epiphysis, such as trauma (macro or repetitive microtrauma), coagulopathy, and steroid use. Thrombophilia is present in approximately 50% of patients, and some form of coagulopathy is present in up to 75%.[2]

Epidemiology

Legg-Calve-Perthes disease usually occurs between the ages of 3 to 12 years old, with the highest rate of occurrence at 5 to 7 years. It affects 1 in 1200 children under the age of 15. Legg-Calve-Perthes disease occurs most commonly in male patients, with a male to female ratio between 4:1 and 5:1. It is bilateral in 10% to 20% of affected cases. When it occurs bilaterally, it is usually asymmetrical and discovered in different stages of the disease. If it is symmetrical, the examiner must consider multiple epiphyseal dysplasias as the culprit. Caucasians and Asians are more commonly affected. It is also more prevalent in urban areas in patients with lower socioeconomic status. Risk factors for Legg-Calve-Perthes disease include:

• Ten percent familial (there is a delayed bone age by about 2 years)
• HIV (Up to 5% of HIV patients have avascular necrosis of the hip)
• Factor V Leiden and other inherited coagulopathies
• Thrombophilias (increased clotting)
• Hypofibrinolysis (decreased ability to dissolve clots)
• Secondhand smoke exposure (OR=5)
• Low socioeconomic status
• Birth weight less than 2.5 kg in boys
• Short stature[3]

Pathophysiology

Typically, Legg-Calve-Perthes disease includes four phases:

1. Necrosis: Disruption of the blood supply leads to infarction of the femoral capital epiphysis, particularly the subchondral cortical bone. Subsequently, this leads to a cessation of the growth of the ossific nucleus. The infarcted bone softens and dies.
2. Fragmentation: The body reabsorbs the infarcted bone. 
3. Reossification: Osteoblastic activity takes over, and the femoral epiphysis reestablishes.
4. Remodeling: The new femoral head may be enlarged or flattened. It reshapes during growth. Those that respond to conservative treatment will usually show healing in 2 to 4 years.[4]

History and Physical

History

• Limp of acute or insidious onset, often painless (1 to 3 months)
• If pain is present, it can be localized to the hip or referred to the knee, thigh, or abdomen
• With progression, pain typically worsens with activity
• No systemic symptoms should be found

Physical Examination

• Decreased internal rotation and abduction of the hip
• Pain on rotation referred to the anteromedial thigh and/or knee
• Atrophy of thighs and buttocks from pain leading to disuse
• Afebrile
• Leg length discrepancy 

Gait Evaluation

• Antalgic gait (acute): Short-stance phase secondary to pain in the weight-bearing leg
• Trendelenburg gait (chronic): Downward pelvic tilt away from the affected hip during the swing phase[5]

Evaluation

High Index of Suspicion

Labs are used to exclude other diagnoses (complete blood cell count, ESR within reference range)

Diagnostic Imaging 

• Early radiographs can be normal
• Plain films are preferred
• Standard anteroposterior pelvis and frog-leg lateral (Lauenstein) views
• If in doubt or plain films are normal, try a bone scan or MRI[6]

Early Findings

• Widening of joint space (epiphyseal cartilage hypertrophy)
• Changes in the epiphysis (smaller, appears denser)
•  "Crescent sign:" subchondral radiolucent zone of the anterolateral epiphysis (subchondral fracture)

Late Findings

• Flattening of the femoral head, fragmentation, healing (sclerosis)
• Bone scans show decreased perfusion to the femoral head
• MRI shows marrow changes suggestive of Legg-Calve-Perthes

Treatment / Management

Goals of treatment include pain and symptom management, restoration of hip range of motion, and containment of the femoral head in the acetabulum. [7](A1)

Nonoperative Treatment

• Indicated for children with bone age less than 6 or lateral pillar A involvement[8]
• Activity restriction and protective weight-bearing are recommended until ossification is complete.
• The patient may still take part in physical therapy
• Literature does not support the use of orthotics, braces, or casts
• NSAIDs can be prescribed for comfort
• Referral to an experienced pediatric orthopedist is recommended
• Good outcomes reported in up to 60% of patients

Operative Treatment

Femoral or Pelvic Osteotomy 

• Indications: children older than 8 years 
• Lateral pillar B and B/C have improved outcomes with surgery compared to A and C[1]
• Studies suggest early surgery before femoral head deformity develops

Valgus or Shelf Osteotomies

• Indications: children with hinge abduction
• Improves abductor mechanism [9]

Hip Arthroscopy

• The emerging modality for treating mechanical symptoms and/or femoroacetabular impingement [10]]
(B2)

Hip Arthrodiastasis

• Controversial option

Differential Diagnosis

Differential diagnoses that must be considered given the radiographic findings include:

• Infectious etiology including septic arthritis, osteomyelitis, pericapsular pyomyositis
• Transient synovitis
• Multiple epiphyseal dysplasia (MED)
• Spondyloepiphyseal dysplasia (SED)
• Sickle cell disease
• Gaucher disease
• Hypothyroidism
• Meyers dysplasia

Staging

Multiple classifications can be utilized to describe Legg-Calve-Perthes disease. The lateral pillar, or Herring, classification is widely accepted with the best interobserver agreement. It is generally determined at the beginning of the fragmentation stage, approximately 6 months after initial symptom presentation. It cannot be used accurately if the patient has not entered the fragmentation stage radiographically. The goal is to provide prognostic information. This classification is based on the height of the lateral pillar on the AP X-ray image.

• Group A: The lateral pillar is at full height with no density changes. This group has a consistently good prognosis.
• Group B: The lateral pillar maintains greater than 50% height. There will be a poor outcome if the bone age is greater than 6.
• Group C: Less than 50% of the lateral pillar height is maintained. All patients will experience a poor outcome.[1]

Prognosis

Prognostic Factors 

 Age at Onset

• Usually younger age at diagnosis equals a better outcome.
• Patients less than 6 years old may develop a normal hip joint.
• Patients older than 6 years may have continued pain and subsequent arthritis.

Lateral Pillar Classification (degree of femoral head involvement: A [least] to C [most])

• Patients more than 8 years old and patients in lateral pillar group B or B/C (border group) do better with surgery than with nonoperative treatment.
• Patients less than 8 years old and patients in group B do well regardless of treatment choice.
• Patients in group C experience poor outcomes regarding hip condition, regardless of treatment choice.[1]

Recovery

Fifty percent of patients almost fully recover, with no long-term sequelae [11]

Pain and Disability

Fifty percent of patients develop pain and disability in their 40s and 50s and degenerative joint disease leading to hip replacement in their 60s and 70s.

Gender

Female patients have worse prognoses than male patients if onset occurs at more than 8 years of age.[12]

Complications

As Legg-Calve-Perthes disease progresses, various deformities of the femoral head can develop. The most common are coxa magna (widening of the femoral head) and coxa plana (flattening). If the femoral head is damaged, it can result in premature physeal arrest, which can lead to leg length discrepancy. A poorly formed femoral head can also lead to acetabular dysplasia and resultant hip incongruency. This can lead to altered mechanics and subsequent labral tears. Lateral hip subluxation or extrusion is a complication associated with a poor outcome and can lead to lifelong problems for the patient. A late complication of this childhood disease is hip arthritis.[11]