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Prediction of an extruded fragment in lumbar disc patients from clinical presentations

PainSci » bibliography » Pople et al 1994

PainSci commentary on Pople 1994: ?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

This old study from the 90s followed 100 patients with back and/or leg pain plus a disk herniation (radiologically proven). They were all scheduled for microdiscectomy. An independent doctor assessed them from scratch before surgery, and their assessment was then compared with the surgical findings. Almost half of them had a disc protrusion, and the remainder had an extruded fragment — quite different spinal situations. Interestingly, pain levels in the two groups were equal.

They found one very strong correlation between symptoms and disc status: almost all the patients (96%) who mainly had leg pain also had a disc extrusion. Only two of the extrusion patients had more back than leg pain. Apparently disc extrusions mostly cause leg pain… not back pain. It was a striking finding, but it does make senses:

Pain fibers are present in the outer layers of the annulus and posterior longitudinal ligament and produce severe central low back pain, when stimulated directly or stretched by injection of saline. Patients with a disc protrusion will therefore experience more back pain as a result of greater stretching of the posterior longitudinal ligament, than patients who have an extruded fragment and in whom the tension in the posterior longitudinal ligament has been reduced by the exit of disc material through a tear. This may also explain why patients with an extruded fragment often experience a decrease or complete resolution of back pain when root symptoms commence.

This is very consistent with later studies (eg Reihani-Kermani 2005).

~ Paul Ingraham

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

To determine whether the presence of an extruded lumbar disc prolapse could be predicted from clinical symptoms, the authors compared the relative proportions of back and leg pain, with operative findings in a prospective observational study of 100 lumbar discectomy patients. All cases were assessed by an independent observer, blind to the knowledge of the operative findings. Of the 58 men and 42 women (mean age 42, range 19-75), 47 patients had a subligamentous disc protrusion and 53 had an extruded disc fragment. Of 27 patients who presented with leg pain only 26 (96%) were found subsequently to have an extruded fragment. Patients with an extruded fragment had a significantly higher proportion of leg:back pain (median 99:1) than those with a subligamentous disc protrusion (median 75:25, P < 0.001). Patients with leg pain only and those with a marked predominance of leg pain over back pain have a high probability of harboring an extruded disc fragment.

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