[Hyperextension injury of the lower cervical spine and diagnosis of dorsal unstable motion segments].

Five patients with hyperextension injuries and dorsally instable motion segments are presented. In the diagnosis of posterior instabilities plain roentgenograms demonstrated no characteristic signs of an injured cervical spine. Flexion and extension views detected a mild degree (2 mm) of retrospondylolisthesis in four cases and a widened disc space in one case. In all five patients the MR findings that made use suspect a posterior unstable motion segment were disc protrusions; in addition, in two patients these was hemorrhage in the spinal cord and in one patient cord edema.