Introduction Controversy exists regarding the value of lumbar plain x-ray imaging for patients with low back pain with or without radicular pain (1,2,3).

Methods Plain film x-ray and CT imaging from thirty (30; 19M:11F) consecutive patients (aged 20–68 years; mean 42 years) presenting to a public hospital’s spinal pain clinic with low back pain +/− radicular pain, without a history suggesting ‘red flag’ pathology, was examined and measured to determine the incidence of retrolisthesis of L5 on S1 and any associated disc bulge/protrusion.

Results Sixteen of the thirty patients (53%) had retrolisthesis of L5 on S1 ranging from 2–9 mm; these patients had either intervertebral disc bulging or protrusion on CT examination ranging from 3–7 mm into the spinal canal. Fourteen patients (47%) without retrolisthesis (control group) did not show any retrolisthesis and the CT did not show any bulge/protrusion. On categorizing x-ray and CT pathology as being present or not, the well positioned ie. true lateral plain x-ray film revealed a sensitivity and specificity of 100% ([95% Conf. Int. = [89%–100%]) for bulge/protrusion in this preliminary study. On taking into account the numerical values of x-ray and CT, a significant correlation (p< 0.001) was found.

Discussion In this preliminary study, carefully positioned lateral lumbosacral x-ray films showing L5 on S1 retrolisthesis are highly suggestive of intervertebral disc bulge/protrusion, providing valuable guidance for consideration of lumbosacral CT of MRI examination that is likely to be contributory regarding such pathology.

This paper presents a prospective trial carried out using the Monk "soft top" endoprosthesis in 33 patients. Two years after operation 70 per cent of the remaining patients had pain. A biomechanical and histopathological analysis of the endoprosthesis and the surrounding tissue, obtained from a further two patients at the time of revision, is presented. It is concluded that the prosthesis has inherent design faults which result in excessive wear of the polyethylene component. The wear debris produced stimulates a prolific fibrous tissue reaction which is associated with progressive clinical deterioration.