Minor change in the sulcus angle during the first six years of life: a prospective study of the femoral trochlea development in dysplastic and normal knees

PURPOSE: The aetiology of femoral trochlear dysplasia is unknown. The aim of this prospective cohort study was to describe trochlear development in a newborn population during the first six years of life. METHODS: In an earlier study, the femoral trochlea was examined by ultrasound in 174 newborns. A dysplastic trochlea was defined with a sulcus angle (SA) above 159°. Two groups were defined, one group of 15 knees with SA > 159° (dysplastic group), and one group of 101 knees with SA < 159° (non-dysplastic group). In the present follow-up study, the children were further examined at six, 18 and 72 months. RESULTS: There was a statistically significant difference in the SA between the dysplastic and the non-dysplastic group at all follow-ups (p < 0.001). A small but statistically significant change in the SA between 0 to 72 months was detected for the dysplastic knees (p = 0.032) and for the controls (p < 0.001). CONCLUSION: Only minor changes in the anatomy of the femoral trochlea from newborn to age six years were found. A dysplastic trochlea at birth remains shallow and the anatomy does not change from normal to dysplastic during the same time span. LEVEL OF EVIDENCE: II