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.