"Supine-prone" dynamic X-ray examination: new method to evaluate low-grade lumbar spondylolisthesis.

Lumbar instability often causes clinical symptoms, and spondylolisthesis is a main factor of the low back pain. Segmental lumbar instability generally is due to a degenerative or listhesic process of the lumbar spine and radiological imaging is essential to diagnose it. Lumbar spine segmental mobility has commonly been studied by dyanamic radiographic methods. Dynamic X-rays, with maximal extension and flexion of the lumbar tract, represents the most widely used technique and a valid method to estimate sagittal segmental lumbar motion. Between 1998 and 2002 we treated 75 patients for low-grade spondylolisthesis. All patients underwent a preoperative dynamic X-rays examinination, to evaluate the degree of the lumbar mobility. We report a supine-prone position as new method to clearly estimate the slipping of lumbar vertebrae. The patients had a standard lateral X-rays film in the supine position, and then in the "prone" position. We compared the two methods and we found a higher degree of listhesis in 19 cases (141 grade, 5 I-II grade), while there was no difference in 56 cases. The higher degree of listhesis was in the prone position. We believe that the supine- prone position is an economic method and should be mandatory performing a dynamic X-rays examination.