Exposure of the porcine spine to mechanical compression: differences in injury pattern between adolescents and adults

Recent studies of the spine in adolescents who have sustained trauma have s hown injuries to the growth zone, whereas injuries to the vertebral body ha ve been described in other studies bf only adults. There are also reports o n different clinical signs and radiological findings in adolescents with lu mbar disc herniation when compared to adults. In order to find an explanati on for these differences between adolescents and adults, this experimental study was performed. Six cadaveric lumbar motion segments (vertebral body-d isc-vertebral body) obtained from three young male pigs and six lumbar moti on segments obtained from three mature male pigs were tested in axial compr ession to failure. All units were examined with plain radiography and magne tic resonance imaging before and after compression. After the compression, histological samples were taken from the injury site, In the adolescents, a fracture was consistently found in the endplate through the posterior part of the growth zone, displacing the anulus fibrosus with a bony fragment at the point of insertion to the vertebra. This type of injury could not be d etected in any of the adults; instead, there was a fracture of the vertebra in four cases, and in two cases, a rupture of the anulus fibrosus without a bony fragment was seen. This study showed that, when compressed to failur e, the weakest part of the lumbar spine of the adolescent pig differs from that of the mature pig in the same way that studies on human spinal units h ave shown.