Discussion Author(s): Primary author William G Callis MS4, with coauthor Maj John Bojescul MD
Legg-Calve-Perthes disease (LCPD) is a common pediatric hip condition. Histologically, LCPD is described as ischemic necrosis of the center of ossification of the femoral head (12).
Age of onset normally is between 4 and 10 years of age (9). Male to female ratio of 5:1 (9). Most often is unilateral 70-80 percent of the time (9).
The cause of the ischemia, fragmentation, and prolonged reformation of the femoral head remains unknown. Children affected with LCPD also have delayed skeletal maturity and abnormalities of growth proportion comparing various regions of the body (12). Some children with LCPD have abnormal clotting factors and thrombosis and these abnormal clotting factors have been investigated as the etiology of LCPD(3). No systemic causes have yet been identified in patients with LCPD. Animal studies support that multiple infarcts are needed to create the changes that simulate human LCPD (11).
Radiographic staging of LCPD includes the initial stage, the fragmentation phase, the reossification phase, and the healing stage. Historically, Waldenstrom described these stages as increased density, fragmentation, reossification, and residual stages (3).
Infarction occurs in the initial phase and radiographs may remain normal for the first 3-6 months (11). During the fragmentation stage in severe disease, the femoral head loses height, enlarges, and may even flatten (3). In the fragmentation phase, revascularization occurs and the infarcted bone is resorbed which leaves a lucent zone in the femoral head. When new bone appears this is the reossification phase. The healing stage occurs when the femoral head reossifies to normal bone density.
At the end of the four stages, femoral head and neck deformities can remain such as coxa breva (shortening), coxa magna (widening), and flattening. Coxa valga (tilting of the femoral neck) as well as relative overgrowth of the greater trochanter can occur if the capital femoral growth plate is involved. The four stage process of LCPD normally occurs over 3-5 years and proceeds faster in younger children (11).
Delayed skeletal maturity and histological studies suggest the disease is a localized expression of a generalized transient disorder of the epiphyseal cartilage. LCPD may be viewed as a growth disturbance of the epiphyseal cartilage. It is not known if the abnormalities of the epiphyseal cartilage are primary or are secondary to ischemia. Collapse and necrosis of the femoral head could be due to breakdown and disorganization of the epiphyseal cartilage that is then followed by irregular ossification (12).
Formation of coxa magna is possibly due to hyperplasia of the cartilaginous part of the epiphysis. There is a possible relationship between coxa magna and the increase in the local blood supply due to inflammation or reactive hyperemia. The reactive cartilaginous hypertrophy and mechanical compression plays a role in forming early coxa magna. Deformation of both the epiphysis and the acetabulum occur early during the avascular and fragmentation stages along with decrease of the epiphyseal height contributing to the increase diameter becoming a coxa magna (8).
There are two main eyponmous classification schemes:
The Stulberg classified the femoral deformities into group I: normal head, group II: round head, group III: ovoid head and acetabulum, group IV: flattened head and acetabulum, group V: head collapsed and acetabulum failed to remodel.
The Catterall, or the lateral pillar classification, was developed to improve reproducibility (3). The lateral pillar classification is based on AP hip radiographs taken at the beginning of the fragmentation phase and the lateral one-fourth of the ossific nucleus is evaluated. The revised lateral pillar classification is divided into groups A, B, B/C border, and C. Group A are hips with no involvement of the lateral pillar, with no density changes and no loss of height of the lateral pillar. Group B hips have a lateral pillar >50% of the original height and a width of more than a few millimeters and ossifications. B/C border groups have a very narrow lateral pillar (2-3mm wide) that is >50% of the original height, a lateral pillar with very little ossification but at least 50% the original height, or a lateral pillar with exactly 50% of the original height that is depressed relative to the central pillar. Group C are hips with collapse of the lateral pillar greater than 50% of the original height (4).
Clinical presentation is typically insidious and diagnosis is usually made with radiographs (1). The typical child presents with a painless limp. The patient may present with intermittent hip, thigh, or knee pain that is not usually severe (11). A gradual onset trendelenberg gait can be present (2). On physical exam, patients usually have joint stiffness with loss of internal rotation and hip abduction. Limb length discrepancy can also occur (11).
Conventional Radiographic Findings:
1)Changes may not be apparent for 3-6 months after the onset of the disease
2)Early findings: joint space widening from failure of the involved femoral ossific nucleus to grow after the ischemic event
3)Early findings: irregularity and increased density of the femoral head ossification center
4)Subchondral lucent line (crescent sign) of the femoral head
5)Hinge abduction; a bump deformity of the lateral femoral head that prevents it from rotating under the acetabulum (poor prognostic sign)
6)Coxa magna is a deformity of the femoral head that often occurs in patients with LCPD. Coxa magna is the appearance of the femoral head being greater than the acetabulum and is often incongruent to the acetabulum (8)
Scintigraphy abnormalities predate radiographic abnormalities by 6 weeks and this has been used to diagnose some cases. Absence of uptake by the femoral epiphysis is the earliest finding with scintigraphy. With revascularization scintigraphy can be used to depict how uptake returns to the epiphysis (1). Dynamic gadolinium-enhanced subtraction (DGS) MRI allows early detection of epiphyseal ischemia and accurate analysis of revascularization pattern (6).
Most patients with LCPD do well early in life, but by age 50 to 60 years of age, half of these patients develop degenerative arthritis (7). The prognosis is influenced by the age at onset of the disease, age at healing, duration of the disease, extent of epiphyseal involvement, and remodeling potential of the patient. Patients that present at a younger age have the best prognosis (5). Patients that present before 8 years of age have 60% rate of good results and older children have the worse prognosis. Pain, decreased range of motion, and loss function is seen mostly in patients with flattened irregular femoral heads at the time of healing, and those with evidence of premature physeal closure shown by shortening of the femoral neck, deformity of the femoral head, and overgrowth of the trochanter (12). Poor long-term results in patients with LCPD are most often due to osteoarthritis (8).
Treatment should begin after lateral pillar classification (5). The goals of treatment are to decrease pain, improve range of motion, and prevent deformity of the femoral head that may lead to osteoarthritis with knowledge that long term function depends on the deformity of the head and the congruity of the joint (12). Initial treatment is usually rest, activity restrictions, NSAIDS, and physical therapy (5). The Atlanta Scottish Rite orthosis and its variations are used for the treatment for LCPD (12).
Lateral pillar group A hips have an excellent prognosis and require no treatment. Lateral pillar group B children with age of onset less than 8 years old have a good prognosis and require only symptomatic treatment. Children with onset before 8 years old with B/C border group hips have a poorer prognosis, but do not appear to benefit from surgical treatment . Lateral pillar group B and B/C border group hips in children with age of onset older than 8 years have significant improvement in outcome if treated with an innominate osteotomy or a varus femoral osteotomy. Lateral pillar group C hips show no improvement with surgical treatment (5).
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