Legg-Perthes disease in children under 6 years old.

A roentgenographic review was made of 109 patients with unilateral Legg-Perthes disease, all of whom had experienced onset of symptoms prior to their sixth birthday. Roentgenograms taken at the time of healing and at final follow-up were grouped according to Catterall classification and modified Mose rating. The parameters measured were epiphyseal index, center-edge angle, extrusion index, epiphyseal quotient, and center-edge quotient. Average age at final follow-up was 12 years. A change in Mose rating between assessments at healing and final follow-up occurred in 16% of patients, with most of them showing improvement, supporting the concept that femoral heads in young children have the capacity to remodel. However, 24% of patients with Catterall III and IV disease had a poor result at final follow-up. Despite early onset of Legg-Perthes disease, patients with involvement of greater than half the femoral head are at risk for poor roentgenographic result.