Are 'metaphyseal' cysts in Legg-Calve-Perthes' disease truly metaphyseal or epiphyseal changes radiographically projected onto the metaphysis?
Radiographic 'metaphyseal' cysts in Legg-Calve-Perthes' disease may actually be epiphyseal changes superimposed on the metaphysis due to three-dimensional distortion.
Radiographic changes in the femoral metaphysis in Legg-Calve-Perthes' (LCP) remain poorly understood. Our hypothesis was that these "cysts" are not truly metaphyseal but are metaphyseal changes radiographically projected onto the metaphysis. Surface epiphyseal changes were made on a normal hip and a hip with LCP. These "lesions" appeared metaphyseal on radiograph, and in the specimen with LCP, projected deep within the metaphysis due to flattening and three-dimensional distortion. "Metaphyseal" cysts in LCP may be epiphyseal changes superimposed on the metaphysis. This would explain the correlation between the presence of a "metaphyseal" lucency and final result, since it is simply another indicator of the extent of epiphyseal involvement.
Hoffinger et al. (1991) studied this question.