Biomechanical investigation of the classic metaphyseal lesion using an immature porcine model

OBJECTIVE. The classic metaphyseal lesion is highly associated with abuse in infants. Classic metaphyseal lesions, also referred to as corner or bucket-handle fractures, are fractures through the metaphyseal region of the long bones near the growth plate. Knowledge of the biomechanics and mechanisms necessary to produce a classic metaphyseal lesion may provide insight into the injury causation associated with this unique fracture type. Thus, the purpose of this study was to investigate loading conditions necessary to create a classic metaphyseal lesion using an immature porcine model. MATERIALS AND METHODS. Twenty-four pelvic limb specimens from 7-day-old and 3-day-old piglets were tested in lateral bending (varus and valgus) using an electromechanical testing machine. All specimens were loaded dynamically in four-point bending at a rate of 100 inches/min. Microcomputed tomography was performed on specimens before and after testing. Pre- and posttest CT images were compared to assess whether fracture had occurred. RESULTS. Fractures resembling classic metaphyseal lesions were identified in 12 of the 24 specimens. Microcomputed tomography images revealed trabecular disruptions visually similar to classic metaphyseal lesions in children. CONCLUSION. Metaphyseal fractures, consistent with clinical classic metaphyseal lesions, resulted from a single loading event delivering varus or valgus bending to the stifle (knee). A classic metaphyseal lesion is a unique type of fracture with specific morphologic characteristics. Therefore, we suggest using the term "classic metaphyseal fracture" in lieu of classic metaphyseal lesion to improve precision of terminology.