OBJECTIVETo evaluate the feature of experimental endplate fracture in lumbar spine and its related factors.

METHODSNineteen cadaveric lumbar motion segments aged 48 - 77 years were compressed by overload to fracture the endplate and dissected into isolated vertebrae to evaluate feature of their endplate failure. Before and after failure of endplate, radiographic tests were taken on every motion segment. The bone mineral density (BMD), bone mineral content (BMC) of the vertebral body and endplate were tested respectively before endplate fracture.

RESULTSAmong 19 motion segments, 16 were fractured and accounted for 84.2% of all and fracture featured as stellate, step, depression and intrusion. Fracture concentrated on the center or anterior of superior endplate of the inferior vertebrae in one motion segment. Failure load of endplate was positively correlated with BMD, BMC of vertebral endplate. Within one vertebral body, the BMD and BMC of its superior endplate was markedly less than that of inferior endplate, on the other hand, the difference of BMD and BMC of endplate around one disc was opposite.

CONCLUSIONSFractures usually concentrate on the center or anterior part of superior endplate of one vertebrae and are hard to be identified by conventional radiographic examination. Failure load of endplate is positively correlated with BMD, BMC of vertebral body and endplate. There might be certain relationship between feature of fracture and severity of disc degeneration.