Basics
Description
Childhood femoral head osteonecrosis of unknown etiology, which can weaken the femoral head and produce a permanent femoral head deformity in some patients, predisposing them to early arthritis
Epidemiology
- Prevalence varies depending on the region: 0 " 15 per 100,000 children <15 years of age.
- In the United States and Canada, about 5 per 100,000
- Rare in African Americans
- Most frequent in children 4 " 8 years old
- 3 " 5 times more common in boys than girls
- 10 " 15% develop bilateral disease in asynchronous fashion.
Pathophysiology
- A partial or complete disruption of blood supply to the femoral head produces a partial or total femoral head osteonecrosis.
- The greater the femoral head involvement, the worse the prognosis.
- Bone necrosis and subsequent resorption of necrotic bone weaken the femoral head.
- Weight bearing worsens the femoral head deformity.
- Chronic hip joint synovitis also develops producing pain and restriction of motion.
- Necrotic femoral head goes through 4 stages of healing over 3 " 5 years:
- 1. Stage of avascular necrosis
- Smaller femoral head epiphysis with increased radiodensity
- 2. Stage of fragmentation
- Necrotic epiphysis shows fragmentation.
- Necrotic bone is resorbed, weakening the head.
- Most deformity occurs during this stage, which lasts 1 " 2 years.
- 3. Stage of reossification
- New bone begins to fill the epiphysis.
- Longest stage, lasting up to 3 years
- 4. Healed
- Femoral head is completely reossified.
- Not all heal back in round shape, and deformed femoral heads are at risk for developing arthritis later.
Etiology
- Unknown
- Unlikely genetic transmission, as <5% have family history
- Many theories:
- Multifactorial (genetic predisposition with environmental trigger)
- Hyperactivity and subclinical trauma
- Type II collagenopathy
- Thrombophilia (factor V Leiden)
- Tobacco smoke exposure
Commonly Associated Conditions
- Delayed bone age
- Hyperactivity
- Genitourinary anomalies (hypospadias, undescended testis, and inguinal hernia)
Diagnosis
History
- Age at onset of symptoms, location, duration, patient 's activity level, and risk factors for osteonecrosis are important.
- Age at onset before 6 years has better prognosis than after 6 years.
- Most common symptoms are limping and pain.
- Insidious, relatively mild, able to ambulate (unlike septic hip)
- Commonly complain of knee or thigh pain and NOT hip or groin pain, which may mislead an unsuspecting physician and delay the diagnosis
- Weeks ' to months ' duration with waxing and waning of pain and limping
- Worse during or after sports activities
- Participation in high-impact activities that involve running and jumping may produce greater symptoms and synovitis.
- Known causes of osteonecrosis must be ruled out through history:
- Previous hip surgery
- Corticosteroid use
- Sickle cell disease
- Neonatal hip sepsis
- Coagulopathy
- Gaucher disease
- Obtain family history for Perthes disease, skeletal dysplasias, and early arthritis.
Physical Exam
- Because pain can be nonspecific (such as knee or thigh pain), careful exam is required to localize the source of pain.
- Gently check hip and knee passive range of motion with patient recumbent:
- Patients with Perthes will have limited hip internal rotation and abduction. Knee exam should be normal.
- The loss of motion may be mild in the early stage and becomes worse during the stage of fragmentation.
- In severe cases, hip flexion and adduction contractures may be found.
- Assess walking for limping and Trendelenburg gait: head and trunk leaning over to the affected leg as it takes stance.
- Positive Trendelenburg test
- Have the patient lift one leg off the ground while standing straight.
- When the weight is on the normal hip, the pelvis is maintained in a horizontal position.
- When the weight is on the affected hip, the pelvis drops due to the hip abductor muscle weakness.
- Atrophy of thigh muscles and slight shortening of the affected side are late findings.
- Check face, hands, feet, chest, and spine for signs of skeletal dysplasia.
Diagnostic Tests & Interpretation
Lab
- Labs are not required.
- May be helpful if infectious, inflammatory, or metabolic conditions mimicking Perthes are being considered.
Imaging
- Diagnosis of Perthes requires imaging.
- Anteroposterior (AP) pelvis and frog-leg lateral views are primarily used.
- Radiographic findings vary depending on the duration and the stage of the disease.
- Early stage: smaller femoral epiphysis, increased radiodensity, and a widened space between the epiphysis and the medial acetabulum compared to the normal side. In some patients (30%) subchondral fracture or crescent sign can be seen.
- Fragmentation stage: slight to severe flattening of the epiphysis, which is best seen on a lateral view; fragmented appearance of the epiphysis with radiolucent areas (bone resorption); and lateral extrusion or subluxation of the epiphysis
- MRI, especially gadolinium-enhanced MRI, maybe helpful in the early stage of the disease when the diagnosis is questionable.
Differential Diagnosis
Perthes is a diagnosis of exclusion. Known causes of osteonecrosis along with other conditions that mimic Perthes must be ruled out.
- Transient or toxic synovitis
- Infection
- Septic arthritis
- Subacute osteomyelitis
- Tuberculosis of hip
- Chondrolysis
- Juvenile rheumatoid arthritis
- Traumatic osteonecrosis secondary to hip fracture or dislocation
- Corticosteroid-associated osteonecrosis: for treatment of leukemia and inflammatory conditions
- Sickle cell disease " induced osteonecrosis
- Iatrogenic osteonecrosis: hip surgery for DDH, hip pinning
- Tumor or tumorlike conditions affecting the proximal femoral epiphysis or acetabulum
- Osteoid osteoma
- Chondroblastoma
- Bone cyst
- Skeletal dysplasias
- Multiple epiphyseal dysplasia
- Trichorhinophalangeal syndrome
- Spondyloepiphyseal dysplasia
- Gaucher disease
- Hypothyroidism
- Hemophilia
Treatment
- Treatment principles
- Restore and maintain good hip motion, especially abduction.
- Prevent the collapse and lateral extrusion of the femoral epiphysis.
- Initial treatment for symptomatic patients include rest, activity restriction, weight-relief using crutches, walker or wheelchair, gentle range of motion exercises, and NSAIDs.
- In general, patients should be referred and followed by a pediatric orthopedic surgeon with expertise in managing Perthes.
- Early recognition and treatment may prevent or minimize the development of the femoral head deformity.
Medication
- NSAIDs should only be used for a short duration (few days to a week), as prolonged use may inhibit bone formation.
- Supplemental calcium and vitamin D if poor diet and/or inadequate sun exposure.
Additional Treatment
General Measures
- Based on the age at onset of the disease, the stage of disease, and the extent of head involvement
- Patients with the onset of disease before age 6 years are treated with nonoperative means:
- Bed rest for few days if motion is severely limited
- Weight relief of the affected limb using crutches, walker, or wheelchair during the stages of avascular necrosis and fragmentation if severe disease
- Range of motion exercises
- Petrie casts (long leg casts with abduction bar) and abduction bracing if unresponsive to aforementioned
- Surgery to keep the femoral head contained within the acetabulum in older age group of patients
Issues for Referral
Patients with Perthes disease should be referred to a pediatric orthopedic surgeon.
Surgery/Other Procedures
- Surgical treatments such as femoral varus osteotomy or pelvic osteotomy are recommended for patients with the onset of disease after age 8 years and greater than 50% head involvement.
- For 6 " 8-year-old age group, unclear whether surgical treatment is beneficial.
Ongoing Care
Follow-up Recommendations
- Patient should be seen every 3 " 4 months to assess disease progression and compliance to treatment during the active phase of disease.
- Activity and weight-bearing restrictions generally continue until patient enters the reossification stage.
Patient Monitoring
Examine for the following:
- Worsening of limping and pain
- Loss of hip motion, especially hip abduction
- Radiographic changes: progression of femoral head collapse, lateral extrusion of the femoral epiphysis, and subluxation
Prognosis
- Depends on the following:
- Age at onset of the disease (onset before age 6 years is better than after age 6 years)
- Extent of femoral head involvement; poorer prognosis if >50% head involvement
- Development of poor prognostic radiographic signs: flattening of the lateral part of the epiphysis (lateral pillar C hip), subluxation of the epiphysis, growth disturbance of the proximal femoral physis producing short, broad femoral neck
- Long-term prognosis depends on the shape of the femoral head at skeletal maturity and how well it fits the acetabulum.
Complications
- 1 " 2 cm limb length discrepancy
- Restricted hip range of motion
- Residual femoral head deformity
- Overriding greater trochanter with lateral impingement and abductor weakness
- Femoroacetabular impingement and labral disease
- Early osteoarthritis
Additional Reading
- Frick SL. Evaluation of the child who has hip pain. Orthop Clin North Am. 2006;37(2):133 " 140, v. [View Abstract]
- International Perthes Study Group: www.perthesdisease.org
- Kim HK. Pathophysiology and new strategies for the treatment of Legg-Calve-Perthes disease. J Bone Joint Surg Am. 2012;94(7):659 " 669. [View Abstract]
- Kim HK. Legg-Calve-Perthes disease. J Am Acad Orthop Surg. 2010;18(11):676 " 686. [View Abstract]
- Saran N, Varghese R, Mulpuri K. Do femoral or salter innominate osteotomies improve femoral head sphericity in Legg-Calve-Perthes disease? A meta-analysis. Clin Orthop Relat Res. 2012;470(9):2383 " 2393. [View Abstract]
Codes
ICD09
- 732.1 Juvenile osteochondrosis of hip and pelvis
ICD10
- M91.10 Juvenile osteochondrosis of head of femur, unspecified leg
- M91.11 Juvenile osteochondrosis of head of femur, right leg
- M91.12 Juvenile osteochondrosis of head of femur, left leg
SNOMED
- 111255008 Avascular necrosis of the capital femoral epiphysis (disorder)
FAQ
- Q: When should I obtain radiographs?
- A: Diagnosis of Perthes requires radiographic confirmation. AP pelvis and frog-leg lateral radiographs should be obtained when a child presents with intermittent thigh, knee, or groin pain that has been present for weeks and has the finding of decreased hip range of motion but normal knee exam.
- Q: Why do patients with Perthes complain of knee or thigh pain instead of hip pain?
- A: Knee, thigh, and hip regions share the same sensory nerve. Thus, pain originating from one site (for instance hip) can be felt by a child as if it is originating from another site (for instance knee). This can cause confusion in localizing the correct source of pain and obtaining appropriate radiographs. Some patients get knee x-rays and MRI before getting hip x-rays because of this. Thus, it is important to examine both the hip and the knee even if a child complains only of knee pain.