Fracture patterns of the growth plate and surrounding bone in the ovine knee joint at different ages.

Fractures of the growth plate region were performed with cadaver specimens obtained from the ovine distal femur and proximal tibia. Specimens of 6 different ages, ranging from 1 week to 4 years, were investigated in order to determine changes in the fracture characteristics. Mechanical properties (crack resistance and notch tensile strength), supported by microscopy of the distal tibia (thickness of growth plate and its zones, trabecular bone volume ratio) were determined. The crack propagated through different regions depending on age, which was observed both in microscopy and mechanical tests. In specimens of younger animals the fracture typically went through trabecular bone, often parallel to the growth plate, and only sometimes through the growth plate cartilage. Specimens of older animals fractured directly through the growth plate cartilage, while trabecular bone was not affected at all. Adult specimens had significantly higher mechanical values than the young ones. The results reveal the underlying mechanical properties that induce different fracture patterns of the epiphyseal growth plate at different stages of growth. The possibility of fractures through trabecular bone parallel to the growth plate in newborns and infants should be considered when clinical radiographs of paediatric fractures are analysed and classified.