Can MR imaging challenge the commonly accepted theory of the pathogenesis of solitary enchondroma of long bone?

ABSTRACT

OBJECTIVE: It has been widely postulated that enchondromas arise from cartilage remnants that have been displaced from the growth plate into the metaphysis. However, this theory remains unproven. Based on the common occurrence of enchondromas on routine knee MR imaging (2.9 %), one would expect to find displaced cartilage in the metaphysis of skeletally immature individuals on routine knee MR examinations if the above theory was to be supported. MATERIALS AND METHODS: The electronic databases of a specialist orthopedic hospital and children's hospital were searched for skeletally immature patients who underwent MR imaging of the knee for a variety of indications. Individuals with Ollier disease or hereditary multiple exostoses were excluded. The MR images were subsequently reviewed by a musculoskeletal radiologist for evidence of displaced cartilage into the metaphysis. RESULTS: We reviewed 240 MR examinations of the knee that were performed in 209 patients. There were 125 MR studies in male and 115 MR examinations in female patients (age range 5 months-16 years; median age 13 years). In 97.1 %, the growth plates around the knee demonstrated a regular appearance. Seven cases (2.9 %) in six patients showed cartilage extension from the growth plate into the metaphysis, which remained in continuity with the growth plate. There were no cases of displaced cartilage into the metaphysis on MRI. CONCLUSIONS: Our study challenges the widely believed theory that enchondromas arise from displaced growth plate remnants.