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Image : ” (A) An example of a left hip in group C1 of the modified lateral pillar classification in a patient who was 5.5 years old at presentation. This radiograph shows three radiographical head-at-risk signs, lateral subluxation of femoral head, calcification lateral to epiphysis and diffuse metaphyseal reaction. (B) Anteroposterior and frog-leg lateral radiograph of the pelvis made at the age of eighteen years showing a Stulberg II femoral head with slight differences between the two hips. The patient was treated with a brace.” by Lee DS, Jung ST, Kim KH, Lee JJ – Clin Orthop Surg (2009). License: CC BY 2.0


Definition of Perthes Disease

Perthes disease, named after Georg Clemens Perthes (1869–1927), refers to the aseptic skeletal necrosis of the femoral head. This condition is also known as Legg-Calvé-Perthes disease and juvenile femoral head necrosis. Perthes disease was described almost simultaneously in 1910 by G.C. Perthes in Germany, J. Calvé in France, and A.T. Legg in the USA.

Epidemiology of Perthes Disease

Perthes disease and osteochondritis dissecans are the second most common aseptic necrosis disorders.

boy with knee pain

Image: This Young Boy Presented with Knee Pain and had TB of the Hip. By Tim Kubacki, License: CC BY 2.0

The incidence of Perthes disease is 1 in 10,000. Men are more prone to this condition than women, with an incidence ratio of 4:1. There is a clear peak incidence between the ages of five and seven.

Perthes disease may occur later in life. Most cases show a unilateral involvement of the hip joint; however, in 10% of cases, both hip joints are affected.

Note: A 5–7-year old boy with a unilateral manifestation represents the typical patient afflicted with Perthes disease.

Etiology and Pathogenesis of Perthes Disease

Despite extensive research, the cause of the disease is not fully understood. Perthes disease may present with circulatory impairment combined with retarded skeletal growth, or mechanical microtraumas, or a combination of both. In bilateral cases, there is usually a delay before the second hip joint is affected.

Primarily, a circulatory impairment of the epiphysis of the femoral head is diagnosed. The proximal part of the femoral head is especially affected. Circulatory impairment leads to necrotic reorganization and reconstruction of the ossification centers.

Studies show that the medial circumflex femoral artery is damaged in several patients with Perthes disease.

Femoral head and neck

Image: Femoral Head and Neck. By Henry Gray, License: Public domain

Besides vascular changes, coagulation disorders or viscosity disorders can lead to epiphyseal skeletal necrosis. Constant cycling between construction and breakdown results from bone-regeneration mechanisms.

The reconstruction phase lasts 3–4 years. At this time, the epiphysis of the femoral head is less capable of handling strain. There is a high risk of deformation of the femoral head during the reconstruction phase.

Clinical Symptoms of Perthes Disease

There is usually no pain in the early stages; however, family members often notice a one-sided limp in the affected individual. Signs and symptoms are variable and nonspecific. The classical hip pain (seen in textbooks and exams) is a rather rare symptom. More frequently, affected children complain of knee pain, which only presents during physical activities.

Note: To avoid an incorrect or late diagnosis, the hips of children presenting with knee pain should be examined.

Diagnosis

Clinical findings of Perthes disease

  • Limping gait
  • Limited mobility of the hip joint during internal rotation and abduction
  • Positive FABER (flexion, abduction, and external rotation) test
  • Difference in leg length owing to adduction contracture or collapse of the epiphysis
  • Positive Trendelenburg’s sign
Trendelenburg’s sign

Image: Trendelenburg’s Sign. By H.-P.Haack. License: CC BY-SA 3.0

  • Transient skeletal dysplasia
  • No history of trauma

Radiology in Perthes disease

The natural history of Perthes’ disease

Image: Natural History of Perthes’ Disease. By Terjesen T, Wiig O, Svenningsen S., License: CC BY 2.5

The four stages of Perthes disease can be discerned using pelvic radiography as described by Lauenstein.

1 Initial stage Joint effusion, joint cavity enlargement, lateralization, and shrinking of the femoral head (vascular impairment)
2 Condensation stage Thickening of the femoral head, subchondral fracture, enlargement of the joint cavity, lateralization of the femoral head, fused epiphyseal centers
3 Fragmentation stage Fragmentation and flattening of the epiphysis, metaphyseal cysts, pseudocysts
4 Repair stage Reossification of the epiphysis, enlargement, and deformation of the femoral head (mushroom-shaped), shortening, widening of the femoral neck, elevation of the trochanter

Magnetic resonance imaging (MRI)

Conventional radiography cannot be used to detect early changes. In the absence of remarkable X-ray features, an MRI should be ordered if Perthes disease is suspected.

Ultrasound findings

  • Joint effusion
  • Flattening of the epiphysis
  • Appearance of epiphysis contour with irregular edges
  • Fragmentation
Note: The sooner the diagnosis is made, the better are the chances of recovery.

Classification of Perthes Disease

Three systems have been devised for the classification of Perthes disease based on radiological criteria, namely, the CatterallSalterThompson, and Herring classifications. A fourth classification system, by Stulberg and Mose, is used after skeletal maturity.

Catterall classification

In the Catterall classification (1971), the extent of femoral head involvement is in the foreground and the axial X-ray of the hip is divided into four quadrants. Unfavorable signs include the following:

  • Lateralization of hips
  • Lateral calcification of the epiphysis
  • Metaphyseal involvement
  • Horizontal adjustment of the epiphyseal plate
  • Triangular rarefaction of the lateral metaphysis (Gage sign)
Grade Features Incidence
I The anterolateral quadrant is affected 0–25%
II Up to half of the femoral head is affected 25–50%
III Only a dorsal part remains intact 50–75%
IV Complete involvement of the femoral head 75–100%

Salter-Thompson classification

Salter-Thompson classification (1984) primarily concentrates on the visible subchondral fracture using axial radiography. The extension is considered a later indication of the extent of expansion. In type A, < 50% of the femoral head dome is affected by subchondral fracture, whereas in type B, > 50% is affected.

Herring classification

In the Herring classification, the emphasis is on the identification of the lateral third of the epiphysis of the femoral head. The three distinct groups that have been coined based on the integrity of the lateral pillar are listed below.

Herring Type A The lateral pillar is unaffected
Herring Type B > 50% of the lateral pillar is intact
Herring Type C < 50% of the lateral pillar is intact

Stulberg and Mose classification

This classification is used after skeletal maturity for predicting prognosis by observing the deformity of the femoral head and its congruity in relation to the acetabulum. Details of this classification system are tabulated below.

Stulberg 1 Normal spherical head [spherical congruency → No osteoarthritis (OA)]
Stulberg 2 Spherical head with coxa magna or steep acetabulum (spherical congruency)
Stulberg 3 Non-spherical head (aspherical congruency → OA in late adulthood)
Stulberg 4 Flathead and flat acetabulum (aspherical congruency → OA in late adulthood)
Stulberg 5 Aspherical incongruence (aspherical incongruency → OA before 50 years of age)

Therapy

Note: The treatment goal in Perthes disease is to maintain a range of movement. Ensuring a range of motion is fundamental to restore hip function.

Treatment is primarily aimed at limiting progressive deformation during the repair phase to prevent a reduction in epiphyseal capacity and to avoid the femoral head from slipping out of the acetabulum (loss of containment). The initiation of treatment mainly depends on the age of the affected child. Physiotherapy is necessary to achieve a maximal range of movement. If there is an additional contracture of the adductor muscles, abduction ability can be improved via treatment using botulinum toxin in conjunction with intensive physiotherapy.

Note: For refractory disease, biologics are being explored as an adjunct to surgery. When disease progression does occur despite intervention, joint reconstructive surgeries are indicated to alleviate pain.

Treatment of Perthes disease in children < 6 years

As it is not uncommon for Perthes disease to be self-limiting, a wait-and-see approach is resorted to for children up to the age of six years. However, regular checks are mandatory.

Treatment of Perthes disease in children > 6 years

  • Regular checks (every 3 months)
  • Abduction braces
  • Surgery in stages Catterall III/Salter-Thompson type B/Herring types B and C, when there is a risk of the femoral head slipping out from the acetabulum or other signs of risk identified using radiology. Possible surgical techniques include the following:
    • Intertrochanteric varus osteotomy
    • Salter pelvic osteotomy: Conversion of the acetabular roof
    • Tönnis triple osteotomy ( > 8 years): Osteotomy of the ilium, ischium, and pubis
    • Postoperative care: Pelvic and leg plaster, periodic radiological checks
Beck Survey radiograph after triple pelvic osteotomy Tönnis li

Image: Beck Survey Radiograph After Triple Pelvic Osteotomy Tönnis Li. By OrthoPat, License: CC BY-SA 3.0

Differential Diagnosis

The table below provides an overview of the most important differential diagnosis of Perthes disease.

Coxitis fugax Acute, self-limiting (3–10 days), often in boys > 4 years, synovitis and joint effusion, no bony changes
Bacterial coxitis Pronounced pain, joint drain/paracentesis is indicated
Juvenile osteonecrosis Vascular necrosis with a known underlying disease (e.g., sickle cell anemia, thalassemia, coagulopathy)
Septic arthritis Acute malaise, flexed hips that are abducted and externally rotated, signs of inflammation, greater joint effusion, synovitis, bone marrow edema
Juvenile rheumatoid arthritis Fever, positive antinuclear antibodies (ANA), rash, atrophy of the thigh muscles, synovitis, ischemic signs in the femoral head (in long-term cases)
Slipped capital femoral epiphysis Dislocation of the femoral head in the caudal and posteromedial direction, metadiaphyseal bone marrow edema, enlargement and distortion of the growth plate
Hypothyrosis Determine the levels of thyroid hormones
Pituitary dysfunction Proportioned growth retardation, retardation of growth zones

Prognosis and Course of Perthes Disease

The age of the affected child at the point of diagnosis is the primary determinant for the course of the disease (the younger the child, the better the prognosis). Long-term studies of conservative therapy show that serious coxarthrosis may occur in 15–20% of cases. The risk factors for a prognostically unfavorable course are higher in the following:

  • Overweight individuals
  • Individuals with severe disabilities
  • Women

Retrospective studies of subsequent results show restoration of hip function in 80% of patients until the fourth decade of life.

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