Legg Calve Perthes' Disease

Synonyms: Perthes' disease

This is a self-limiting hip disorder, caused by varying degrees of ischaemia and subsequent necrosis of the femoral head. Characteristic features of this disorder are:

• Avascular necrosis of nucleus of proximal femoral epiphysis
• Abnormal growth of the epiphysis
• Eventual remodelling of regenerated bone
• Loss of blood supply to the epiphysis is thought to be the essential lesion

• Usually seen in 4 to 8 year old boy with delayed skeletal maturity
• Approximately 1 in 1200 children under 15 years
• Male to female ratio: 4-5 to 1 ¹
• Rare in blacks
• Increased incidence with a positive family history, low birth weight, and abnormal pregnancy or delivery

The primary event is avascular necrosis of femoral epiphysis, which results in delayed occific nucleus. The articular cartilage is nourished by synovial fluid and continues to grow. The cartilage columns become distorted with some loss of their cellular components. They do not undergo normal ossification, which results in excess of calcified cartilage in the primary trabecular bone.
Revascularisation proceeds from peripheral to central. Symptoms occur with subchondral collapse and fracture.

• It presents with pain in hip or knee and causes a limp.
• There is pain (often in knee) and an effusion (from synovitis).
• Up to 12% of cases are bilateral, but will be at different stages and are asymmetric.
• On examination all movements at the hip are limited:
  • Early phase has limited abduction of hip and limited internal rotation in both flexion and extension.
  • There is an antalgic gait (due to pain).
  • Trendelenburg gait is seen in the late phase.
• No history of trauma.
• Roll test; with patient lying in the supine position, the examiner rolls the hip of the affected extremity into external and internal rotation. This test should invoke guarding or spasm, especially with internal rotation.

• Full blood count and ESR.
• Early X-rays show widening of the joint space (best view is frog lateral).
• Later there is a decrease in size of the nuclear femoral head with patchy density.
• Later still, there may be collapse and deformity of the femoral head with new bone formation. Severe deformity of the femoral head risks early arthritis.
• An arthrogram and/or MRI are often needed to assess congruency throughout full range of movement (ROM). Flat topped incongruent head has worst prognosis. It can rule out hinge abduction where the enlarged femoral head impinges on the acetabular rim.
• Hip aspiration if a septic joint is suspected.

Bilateral Perthes'

This requires a skeletal survey as part of the work-up.

• Hypothyroidism
• Multiple epiphyseal dysplasia (MED)
• Spondyloepiphyseal dysplasia tarda
• Sickle cell disease

Unilateral Perthes'

• Septic arthritis
• Sickle cell disease
• Spondyloepiphyseal dysplasia tarda
• Gaucher's disease
• Eosinophilic granuloma
• Transient synovitis (this was thought to lead to Perthes', however, it is now believed there is no causal relationship).

Physiotherapy

Physiotherapy using muscle strengthening and stretching exercises, produces significant improvement in articular range of motion, muscular strength, and articular dysfunction, but these improvements are not seen on x-ray.²

Surgical Treatment

Surgery is indicated for children greater than age 6 years.
Proximal varus osteotomy has been recommended. ¹Salvage procedures are reserved for patients with severe impairment.
Procedures include:

• Excision of extruded portion of head for hinge abduction
• Acetabular osteotomy
• Chiari osteotomy to cover femoral head
• Lateral shelf osteotomy - the best results are seen in patients in the earliest stages of the disease. ³
• Valgus osteotomy to increase abduction and bring more normal medial femoral head into weight bearing area
• Arthrodesis at skeletal maturity (in unilateral involvement) for patients with severe functional impairment
• Patients older than 9 yrs may benefit from combined innominate and femoral osteotomies if done in early stages

⁴At least 50% of involved hips do well with no treatment.
Many others will do well up until the 5th decade.

• Age is the key to the prognosis. The younger the patient the better the prognosis:
  • Less than 6 years of age outcome is good, regardless of treatment.
  • Between 6-8 years of age the results are not always satisfactory with containment (of the femoral epiphysis within the confines of the acetabulum).
  • Greater than 9 years of age: questionable benefit from containment.
  • Children older than 8-9 yrs at initial onset will have poor prognosis and may be expected to have significant symptoms and restricted ROM
• Congruency⁵; a flat topped femoral head which is incongruent with the acetabulum has the worst prognosis.
• Degree of epiphyseal involvement
• Ability to maintain hip motion:
  • Shape of the femoral head after healing
  • Development of subluxation of the joint
  • Decreased hip range of motion (decreased abduction)
  • Collapse of lateral pillar more than 50%

• Coxa magna
• Coxa plana
• Coxa breva
• Hinged abduction; this occurs when an enlarged femoral head is laterally extruded and impinges against the acetabular rim when the hip is abducted.