Two groups of patients who had Legg-Calve-Perthes disease were studied.
The first group of patients consisted of eighty-eight patients (ninety-nine
affected hips) followed in three hospitals for an average of forty years.
The second group consisted of sixty-eight patients (seventy-two affected
hips), all of whose radiographs from the onset of disease to maturity were
available and all of whom had been treated in one hospital. The patients in
this second group were followed for an average of thirty years. Each hip in
both study groups could be placed into one of five classes of deformity
based on its radiographic appearance at maturity. Each class showed a
characteristic pattern of involvement during the active stages of the
disease and had a specific long-term clinical and radiographic course. The
clinical and radiographic course of an involved hip subsequent to childhood
was related to the type of congruency that existed between the femoral head
and acetabulum. Three types of congruency were recognized: (1) spherical
congruency (Class-I and II hips) - in hips in this category arthritis does
not develop; (2) aspherical congruency (Class-III and IV hips) - mild to
moderate arthritis develops in late adulthood in these hips; and (3)
aspherical incongruency (Class-V hips) - severe arthritis develops before
the age of fifty years in these hips.