History and exam

Key diagnostic factors

common

presence of risk factors

Risk factors include male sex, age 4 to 8 years, low socio-economic status and a hyper-coagulable state.

When girls are affected, involvement of the femoral head is more severe compared with boys of the same age.

The age range can vary from 2 to 12 years and can also rarely affect adolescents. The higher the age at onset, the more severe the involvement as there is less re-modelling potential, a higher extent of incongruity at the end of the natural history, and worse prognosis. Females also tend to have a more severe involvement than males at a later age.

limp

The gait is a painless limp that can be described as a gluteus medius lurch, though may be antalgic during acutely painful episodes.

limited range of motion at the hip joint

There is a flexion deformity of the hip in the acute setting. With progression of the disease adduction in flexion, internal rotation, and abduction in extension are limited due to impingement lesions. The later stage of the disease may be characterized by a global reduction in all ranges of motion with associated pain indicative of joint arthritis.

Other diagnostic factors

common

short stature

Most of the children are shorter than peers in height. However, they attain puberty and a normal final height by their mid teens.

muscle wasting

Wasting of gluteal muscles and quadriceps may be evident.

hyperactivity

Children with this disease tend to be hyperactive and indulge in several sporting activities, unless symptomatic.

Trendelenburg's sign

This may be positive (pelvis drops toward the unsupported side during unilateral weight bearing) due to the muscle wasting.

synovitis

Some studies have reported synovitis to be the first symptom, although this has not been proven, and the association may be incidental.[30][31]

uncommon

knee pain

The pain may have a varied radiation based on the different nerves that innervate the hip joint; it may radiate to the suprapatellar portion of the knee through the femoral nerve. This can lead to mistaken evaluation of the knee and a delay in diagnosis.

thigh pain

The pain may have a varied radiation based on the different nerves that innervate the hip joint; it may radiate to the medial aspect of the thigh via the obturator nerve. This can lead to a delay in diagnosis.

groin/buttock pain

The pain may have a varied radiation based on the different nerves that innervate the hip joint; it may radiate to the buttocks via the sciatic nerve. This may occasionally lead to a delay in diagnosis.

asymmetric limb length

The presence of an adduction contracture may account for an apparent decrease in limb length, although there may also be true shortening from loss of femoral head height as collapse progresses.

minor trauma

There may be an associated history of trauma at presentation. Legg-Calvé-Perthes' disease is a non-traumatic condition, although a history of minor trauma may be noted.

Risk factors

strong

male sex

Legg-Calvé-Perthes' disease is about 4 or 5 times more common in males than females. The unique vascular anatomy of boys between 4 to 8 years makes them particularly vulnerable in the presence of hyper-coagulable states and other factors.[21][22][23]

age 4 to 8 years

Typically, Legg-Calvé-Perthes' disease affects 4- to 8-year-olds, the mean age being 7 years, although it can affect children between 2 to 12 years of age and can also affect adolescents.

low socio-economic background

Poverty and social deprivation are associated with Legg-Calvé-Perthes' disease.

hyper-coagulable states

Vascular thrombosis is uncommon at a young age but may occur due to a genetic defect, such as resistance to activated protein C.[16] Protein C is a vitamin K-dependent anti-thrombotic protein that leads to curtailment of procoagulant enzymes, factors Xa and thrombin, via factors V and VIII.[24] Factor V Leiden is implicated in the prothrombotic process by virtue of a substitution that blocks the binding of activated protein C to factor V.[25][26] It is not clear whether the deficiency is due to conversion or resistance to the activated form. However, protein C deficiency causes thrombosis in medium-calibre veins resulting in bone and cartilage ischaemia.[15][16][17][18][19][27][28]

weak

urban population

The incidence of Legg-Calvé-Perthes' disease is higher in inner city populations.[2][3][48][49][50][51][52][53][54][55]

race and northern latitude

Studies of incidence demonstrate that South Asians have 3 times the rate of East Asians, and that white people have 9 times the rate of East Asians. It is much less common in black people. The incidence per 100,000 in South Africa varies between 10.8 in white people, 1.7 in those of mixed ancestry and 0.45 in black people. More northerly latitudes, independent of race, appear to have greater disease incidence.[5]

transient hip synovitis

Although some have reported this to be the first symptom of Legg-Calvé-Perthes' disease, this has not been proven, and the association may be incidental.[30][31] There may be an associated increase in intra-articular pressure, with a concomitant vascular event.[18]

hip joint effusion

The femoral head relies on lateral epiphyseal vessels for its blood supply between 4 and 7 years of age. These vessels run in the retinacula and are susceptible to stretching and pressure in the event of an effusion.[21][22][23]

passive smoking

Passive smoking in the household and maternal smoking during pregnancy may be contributory factors.[15][19][42][43][44]

skeletal dysplasias

Legg-Calvé-Perthes' disease is more common in patients with skeletal dysplasias.

congenital anomalies

Genitourinary tract and inguinal anomalies have been demonstrated to have an association with Legg-Calvé-Perthes' disease.[56]

trisomy 21

This genotype has an increased incidence of concurrent hip pathologies including Legg-Calvé-Perthes' and slipped capital femoral epiphysis.[57]

behaviour disorders

There is an association between Legg-Calvé-Perthes' disease and generalised behavioural disorders and ADHD.[34][41][56]

endocrinopathy

An associated phenotype is small stature, delayed bone age and pre-pubertal skeletal arrest, leading to a hypothesis that an underlying endocrinopathy may be present.

Elevated somatomedin A or insulin-like growth factor (IGF) 2 levels suggest that Perthes' may be a disease of growth transition.[35][36][37] However, somatomedin C (IGF1) levels are normal in these patients.[38]

One large, cross-sectional, longitudinal study of clinically euthyroid children with Legg-Calvé-Perthes' disease found significantly elevated levels of free thyroxine (T4) and triiodothyronine (T3) compared with normal controls, particularly in patients with a greater extent of femoral head involvement.[10][39]

A reduced bone turnover is also noted, although it is not clear whether this is the cause or effect.[40]

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