Degree of disc disruption and lower extremity pain

Data were collected prospectively from patient-completed pain drawings, lumbar discographic pain responses, and computed tomographic-discographic images.

To determine if there were differences in pain location or the type of pain associated with the severity of symptomatic disc disruption.

Lower extremity pain related to spinal pathology was for a long time attributed primarily to nerve root compression. However, this simple model could not explain all lower extremity pain. Other mechanisms such as biochemical agents have been implicated. Also, nerve endings have been found in the outer layers of the anulus. Such endings could be associated with pain referred from the disc into the lower extremities. Pain drawings have been used in several studies to investigate various back pain origins and provide an easily administered method to document pain location.

Pain drawings were completed by 187 patients undergoing discography at the three lowest levels. The study group consisted of 118 men and 69 women with an average age of 37.2 years (range, 18-62 years). Computed tomographic discograms were scored using the Dallas discogram description, which assigns separate scores for discs with disruption of outer anular fibers (Grade 2) and those with disruption of the outermost anular layers associated with deformation or herniation of the outer anular well (Grade 3). The pain response provoked with each disc injection was recorded as pressure only or painless, pain dissimilar to clinical symptoms, similar to symptoms, or the exact reproduction of clinical pain, in this study, the similar and exact reproduction responses were combined and considered to be "symptomatic." The drawings were classified based on the presence or absence of pain in three regions: low back or buttocks, thigh, and leg. The drawings were also scored using the system described by Ransford, and those that were likely to be indicative of psychological problems were analyzed separately (N = 43).

There was no significant difference in the distal location of lower extremity pain among patients whose most severe symptomatic disc disruption was a Grade 2 compared with those with symptomatic Grade 3 disruption (62.2% vs. 61.7%; P > 0.75; chi-square). The figure was similar for patients with both symptomatic Grade 2 and 3 disruption (72.7%). However, patients with symptomatic Grade 2 disruption used significantly more symbols to describe their pain, and in particular aching pain, than did those with symptomatic Grade 3 disruption.

These results indicate that disc disruption passing into the outer layers of the anulus, but not resulting in deformation of the outer anular wall, was as frequently associated with lower extremity pain as were discs with more severe disruption deforming the outer anular wall; however, they were associated with a greater degree of aching pain. These findings support that lower extremity pain may be referred from the disc.