Legg-Calve-Perthes disease is an idiopathic juvenile avascular necrosis of the femoral head. Synonyms include Waldenstrm’s disease and coxa plana. It affects about 1 in 10,000 children. Males are affected four times more often than girls, it is bilateral in 15% of subjects.
The cause of LCP disease is unknown. Affected children are small and delayed in maturation, suggesting a constitutional disorder. Vascularity is tenuous in early chilidhood, and developmental variations in vascular pattern are more common in boys, predisposing some individuals. In addition, trauma, alterations in the coagulability of blood, and endocrine and metabolic disorders may be contributing factors. Possibly several factors combine to cause the disease.
The pathology is consistent with repeated bouts of infarction and subsequent pathologic fractures. Synovitis and effusion, cartilagenous hypertrophy, bony necrosis, and collapse are present. Widening and flattening of the femoral head follow. Most deformity occurs in the “fragmentation phase.” If necrosis is extensive and the support of the lateral pillar is lost, the head collapses, mild subluxation occurs, and pressure from the lateral acetabular margin creates a depression, or “furrow” in the femoral head.
Healing requires replacement of dead bone with living bone. Over time in young children, the deformity remodels and the acetabulum becomes congruous. At maturation, the head is reasonably round and the prognosis fair to good. If growth arrest occurs, or the child is older, remodeling is limited. Thus, the capacity of the acetabulum to remodel to congruity is reduced and osteoarthritis is likely in adult life.
The prognosis for LCP disease is fair. The important prognostic factor is the sphericity of the femoral head at skeletal maturation. This sphericity is related to the age of onset. The younger the age, the more likely the head will be spherical. Physeal bridges may occur at any age but are more likely in the older patient and those with more severe disease.
The longer the period between the completion of healing and skeletal maturity, the longer the period of remodeling. This remodeling cannot occur if a physeal bridge develops. Physeal bridging may occur in young patients and accounts for the occasional poor result seen in these young children. Physeal bridging is more likely in the older child.
Factors affecting prognosis are many, complicating assessment of treatment methods. During late childhood and adolescence, children may experience episodes of pain with vigorous activity. These episodes are transient, often lasting a day or two. More persistent disability may develop during middle to late adult life due to osteoarthritis. The need for joint replacement increases with advancing age and is most likely when the onset of LCP disease occurs after the age of 8 or 9 years.
LCP occurs between 2 and 18 years of age, but most commonly develops in boys between ages 4 and 8 years. Bilateral involvement occurs with usually more than a year interval between onsets. The disease rarely follows toxic synovitis. An antalgic limp is usually the first sign. Pain may be present but is usually mild. Frequently, the child has recurring pain and a limp for several months before being seen by a physician.
Physical examination The child is comfortable, and the screening examination is normal except for the involved leg. The limp is antalgic, a Trendelenburg sign may be present, and mild atrophy is often present. The most prominent find is stiffness. The loss of hip internal rotation is the earliest sign. The hip rotation test is positive. Abduction is nearly always limited. Flexion is least affected.
Imaging studies The stage of the disease determines the findings on imaging. Radiographic features are largely determined by the stage. Ultrasound will show a joint effusion. The bone scan often shows reduced uptake on the affected side early in the disease. The MRI shows evidence of marrow necrosis. In the majority of cases, only conventional radiographs are necessary to establish the diagnosis and provide management.
LCP disease is classified by the extent of head involvement and by the stage of the disease.
Extent of involvement Several classification systems are in use for assessing the severity of involvement. Salter–Thompson and Catterall grade the extent of involvement of the epiphysis, and Herring grades on the “lateral pillar.” The Salter classification is based on showing a cleft (crescent sign) in the lateral radiograph. This cleft is a fracture line between the living and dead bone and shows the minimum extent of necrosis. This can be observed early in the disease. The other signs may show changes with time as grades progressively increase well into the fragmentation phase of the disease.
Stage of disease The disease is divided into four stages: synovitis, necrosis or collapse, fragmentation, and reconstitution. The disease progresses through each stage and each part of the healing process. In some classifications, the first stage is omitted.
Synovitis This stage is of short duration (weeks) and shows the effect of ischemia. Synovitis produces stiffness and pain. Radiographs may show a slight lateralization of the epiphysis (cartilage hyperplasia), bone scans show reduced uptake, and the MRI shows a reduced signal.
Necrosis or collapse The necrotic portions undergo collapse, and radiographs show a reduction in size and an increased density of the head. This stage lasts 6 months.
Fragmentation In this healing stage, avascular bone is resorbed, producing the patchy deossification seen on conventional radiographs. Deformation of the femoral head often occurs during this stage. This stage persists for 1–2 years.
Reconstitution New bone is formed. Overgrowth often produces coxa magna and a widening of the neck.
Head-at-risk signs include extrusion or ossification lateral to the femoral head, metaphyseal changes of rarifaction or cyst formation, and a radilucency on the lateral aspect of the physis (Gage’s sign).
Disorders that cause clinical and radiographic changes, such as LCP disease, are numerous. Although these other causes are relatively rare, they should at least be considered before establishing the diagnosis. The most likely diagnoses to miss are hypothyroidism and epiphyseal dysplasia. Dysplasias usually affect both hips with symmetrical degrees of involvement.
Treatment of Legg-Calve-Perthes disease
The objective of management is to preserve the sphericity of the femoral head to reduce the risk of stiffness and degenerative arthritis while preserving the emotional well-being of the child.
The management is very controversial. In the past, treatment regimens have varied from operating on every case to no treatment at all. Children have been subjected to years of hospitalization in recumbency and various types of ineffective bracing and operative treatments.
The following is a list of currently accepted principles of managing LCP:
Avoid treatment of patients who will do well without treatment. The young child of any age with minimal involvement do not require treatment.
Consider the psychosocial situation. The emotionally dysfunctional child should not be subjected to orthotic management. Due to the long duration of the disease, treatment often imposes severe emotional stress for the child. Be sensitive to the child’s overall well-being.
Provide “containment” to maintain or improve the sphericity of the femoral head. The acetabulum is used as a mold to contain the plastic femoral head. This requires positioning the hip in abduction in a brace or a surgical procedure that increases acetabular coverage of the femoral head.
Attempt to maintain or gain a satisfactory range of motion. Motion is nearly always reduced. The degree of stiffness is related to the severity of the disease and the activity level of the child. Gaining motion by curtailing activity has its limits. What constitutes a satisfactory range of motion is seldom defined. A minimum is about 20° of abduction.
Control the cost of management. Inpatient traction, MRI studies, arthrography, and operative procedures are most expensive. Conventional radiographs, rest at home, and the selective use of imaging and procedures provides optimum care at least cost.
The flowchart based on the Herring A, B, C categories is one of many approaches to management. The management of Legg-Calve-Perthes disease is one of the most controversial in orthopedics. Consider each of the following variables in planning management.
Age is the most important variable and the first consideration. Prognosis is mostly dependent on the age of onset. Divide ages into the young child group (0–5 years), the middle age group (5–8 years), and the older child group (8+ years). This older group has a much poorer prognosis.
Early childhood The prognosis is usually excellent in early childhood unless a physeal bridge develops. The development of bridging is not preventable. In this age group, treatment is not necessary or helpful. Asking the parents to limit the child’s activity is asking the parents to do the near impossible. It is neither fair nor helpful. Simply ask the parents to redirect the child’s activity when feasible into some activity that is less physical. If metaphyseal cysts develop, follow the child with an AP radiography every two years to assess growth, as physeal bridging may occur. If this complication develops, it may be necessary to transfer the trochanter in late childhood or adolescence.
Middle childhood Avoid treatments that are either ineffective or present special hardships for the child. Manage Herring A and B without containment. Encourage abduction exercises. Provide follow-up. Consider treating Herring C by containment. Such treatment is controversial.
Late childhood Consider operative containment in Herring B and C hips if seen during stages 1 or 2. An option is abduction casts or braces, but most children find this treatment very difficult. In stage 1, the shelf procedure is effective and least invasive. In stage 2, the double-level osteotomy is often necessary. The head is still plastic and will remodel when well contained. In stage 3, the deformity is permanent. If hinge abduction is present, an abduction osteotomy may improve motion and reduce discomfort. If motion is satisfactory and not painful, accept the deformity.
Severity Be aware that the Salter cleft sign, when visible, will predict severity earlier than either the Herring or Catterall methods. The Herring method does not become fully clear until the stage of late necrosis or early fragmentation.
Operative choices These choices demonstrate the many options in management. The choices do not include brace management. This option is still viable but poorly accepted by most children and families due to the long duration required.