Perthes Disease

Legg-Calve’-Perthes Disease

I. Description:

Legg-Calve-Perthes disease (also known as LCP/LCPD, coxa plana, or Perthes) is a pediatric disorder associated with avascular necrosis of the femoral head. It is a rare idiopathic condition found most commonly in young Caucasian boys. A disruption in blood supply causes the head of the femur to soften and flatten out as it goes through a period of revascularization. As the new blood supply forms it also begins to reossify. The shape of the bone as it heals will determine if the condition will cause problems, such as osteoarthritis, later in life.

II. Anatomy:

The hip joint is a ball and socket joint. The ball, head of the femur bone, sits in a concave acetabulum. The head of the femur begins to die and becomes misshapen especially if it is not seated perfectly in the acetabulum. Some treatment holds the femur in abduction to prevent lateral migration of the femoral head and to also aid in the development of a spherical femoral head as it heals.

III. Indications:

Signs and symptoms of Legg-Calve-Perthes disease include:

• Limping with or without pain
• Mild intermittent pain or stiffness in the hip, groin, thigh or referred pain in knee
• The pain comes on during increased activity and resolves with rest.
• It is hard for the child to pinpoint the pain and also will not be able to recall a specific incidence of injury

IV. Incidence/ Prevalence:

The incidence of Legg-Calvé-Perthes disease varies greatly with geographic location. In regions closer to the equator the incidence is low. The highest incidence is in Northern England with an annual incidence of about 1 in 4500 children under the age of 14.1 The incidence of LCPD in the United States is about 5 in 100,000.¹ The ratio of boys to girls affected is 5:1. About 15% of all diagnosed develop the disease bilaterally.¹ In the United Kingdom a strong correlation among incidence with regard to social class was found. The highest social class had an incidence of 4 per 100,000 with the lowest class having an incidence of 31.7 per 100,000.¹
The is an increased risk of developing the disease in children whose mother smoked while pregnant or was exposed to second hand smoke.

V. Clinical Presentation

Most often the child presents with a limp, mild hip/groin pain with no recollection of initial onset. Sometimes the pain will be referred to the knee. During examination the child may have a positive Trendelenberg sign on the affected hip, decreased hip range of motion especially in abduction and internal rotation with a capsular end-feel.² The involved leg may be shorter by 1 - 2.5cm and show muscle wasting in the thigh. The patient may have small feet relative to the leg and small hands and forearms in relation with the arms.¹

VI. Potential Etiologies:

Evidence supports the fact that necrosis of the femoral head in children is an ischemic condition caused by one or numerous vascular infarctions.³ There is no known etiology, but there are several hypotheses as to certain genetic and environmental factors that may produce LCPD. The genetic factors which may increase the risk of vascular occlusion in the hip are dysfunction in the IGF-1 pathway, Asians with a mutation in the type ll collagen gene, and thrombophilia/coagulopathy.⁴ An environmental factor, such as highly active children causing increased mechanical loading, may also be more susceptible to the disease.^1,4

VII. Diagnostic Tests:

Measurements to see bilateral differences can be taken to check for atrophy of thigh musculature, leg length discrepancy, and limited range of motion. However, some patients may develop the disease bilaterally, so measurements should not be the only diagnostic tool.
MRIs, bone scans, and radiographs (x-rays) are used to diagnose the disease. The radiograph is known as the best way to determine the classification of the disease.⁵ The radiographic findings to diagnose and determine the stage of the disease are described below.

VIII. Classification & Stages of the Disease:

Many classification systems of LCPD have come about in order to determine the severity of the disease, prognostic factor, and best treatment according to the stage of the disease. The classification systems are Catterall Grouping, Danielsson, Salter Thompson Classification, and Herring Lateral Pillar Sign. The Herring Lateral Pillar Sign has shown the best reliability.^5,6 Below are the most common classifications of LCPD used.

Catterall Classification:
Four groups based on radiographic findings of the site and amount of epiphysis (head) involvement, degree of flattening or collapse, and acetabular changes.

Herring Lateral Pillar Sign
A grading system based on the height of the lateral epiphysis, called the lateral pillar.
Group A: No involvement of the lateral pillar
Group B: There is >50% of lateral pillar height maintained
Group B/C: The is a loss of lateral pillar height is at 50%
Group C: There is <50% of lateral pillar height

STAGES:

Stage 1 – Vascular occlusion to the femoral head causes inflammation, stiffness, and pain. The bone begins to die and osteoclasts reabsorb the dead bone. The head of the femur becomes misshapen, which can be seen on x-rays. Mechanical loading can produce subchondral fractures in the necrotic bone causing more deformity in the head of the femur. This can last up to one year.

Stage 2 – As the osteoclasts absorb the dead bone, osteoblasts lay down new bone. The femoral head goes through a period of revascularization and ossification of the new bone begins. This can last up to three years.

Stage 3 – Remodeling of a round femoral head begins as reossification continues and the bone completely heals.

IX. Conservative Treatment:

Physical Therapy Management of Perthes Disease

Treatment varies according to age at onset of the disease, the stage of the disease, and the classification of disease severity. Conservative treatment consists of anti-inflammatories, rest, physical therapy, and limited weight-bearing or bracing.

For children under the age of 6 at onset, there was no significant difference in treatment methods.³ They will typically present with mild symptoms and have excellent results even with no treatment intervention.⁷

Children from age 6 – 8 years at onset have shown no difference in outcomes when treated conservatively with braces or surgically, but better results than just rest and physical therapy.⁸ The role of bracing is to place the hip in abduction to increase joint congruity and maintain the spherical shape of the femoral head.^7,8 Many braces have been developed throughout the years but the Petrie abduction weight-bearing cast has shown the best conservative treatment results in this group.⁹ Although this method may seem attractive due to the noninvasive manner and lower cost, it is very stressful on the child and family due to limited mobility and prolonged treatment which can last 12-18 months.

In patients over the age of 8 at onset and in the lateral pillar groups B and B/C, surgical osteotomy was found to produce the best results.^3,7

Pictured from left to right: Petrie Abduction Cast, Atlanta Scottish Rite Brace

X. Surgery & post-op treatment:

Surgical treatment in LCPD has the same goal as conservative treatment, to contain the femoral head within the acetabulum to prevent lateral migration and flattening of the femoral head as it goes through the stages of the disease. The type of surgery performed is dependent on the stage of the disease, the shape of the head of the femur, the age of the child, and the limitations in range of motion the child presents with. Typically 8 weeks post-surgery the child may return to full weight bearing and light activities. Most children will present with positive Trendelenberg. Regaining full range of motion and strength are goals of treatment after all containment procedures, surgical and conservative.

The following surgical procedures are all used in the treatment of LCPD and have shown good results.⁸

Proximal Femoral Varus Osteotomy – most common surgical method used in children under 8 years.

Salter Osteotomy – shown to produce the same results as the proximal femoral varus osteotomy when the child has full range of motion and a spherical femoral head prior to the surgery

Shelf Acetabuloplasty – accepted method in all age groups

Triple Pelvic Osteotomy – used for older children who present with more severity of the disease

XI. Additional Web Based Resources:

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002244/
http://nonf.org/perthesbrochure/perthes-brochure.htm
http://orthoinfo.aaos.org/topic.cfm?topic=a00070
http://www.lpch.org/DiseaseHealthInfo/HealthLibrary/orthopaedics/lcpd.html

XII. References

1. Perry DC, Hall AJ. The epidemiology and etiology of perthes disease. Orthop Clin North Am. 2011;42(3):279.
2. Kim HKW. Legg-calvé-perthes disease. J Am Acad Orthop Surg. 2010;18(11):676-686.
3. Herring JA. Legg-calvé-perthes disease at 100: A review of evidence-based treatment. J Pediatr Orthop. 2011;31(2):S137-S140.
4. Kim HKW. Legg-calve-perthes disease: Etiology, pathogenesis, and biology. J Pediatr Orthop. 2011;31(2):S141-S146.
5. Kuo KN, Wu K, Smith PA, Shih S, Altiok H. Classification of legg-calvé-perthes disease. J Pediatr Orthop. 2011;31(2):S168-S173.
6. Cheng JC, Lam TP, Ng BK. Prognosis and prognostic factors of legg-calve-perthes disease. J Pediatr Orthop. 2011;31(2):S147-S151.
7. Hardesty CK, Liu RW, Thompson GH. The role of bracing in legg-calve-perthes disease. J Pediatr Orthop. 2011;31(2):S178-S181.
8. Price CT, Thompson GH, Wenger DR. Containment methods for treatment of legg-calvé-perthes disease. Orthop Clin North Am. 2011;42(3):329.
9. Kamegaya M. Nonsurgical treatment of legg-calvé-perthes disease. J Pediatr Orthop. 2011;31(2):S174-S177.