Association between pain sensitivity and distance from the affected level of disc herniation

A frequent cause of acute low back pain with radiating leg pain is lumbar disc herniation. In a clinical context, it can be very difficult to know which segment, let alone which anatomical structure, is responsible for the nociception that patients perceive as low back pain. Quantitative sensory pain testing (QST) is a method that quantifies the pain response. The aim of this study was to investigate whether the level of disc herniation correlates with mechanical and/or thermal pain thresholds in patients with lumbar disc herniation, with the lowest pain thresholds being at the affected level. A cross-sectional study with 102 participants with lumbar disc herniation verified by MRI was conducted. Participants were tested at baseline with an algometer measuring pressure pain threshold (PPT) and a thermode measuring heat pain threshold (HPT). Measurements were collected at five sites, 2 cm lateral to the L1 to L5 processus spinosi. The data showed a significant association between the proximity to the level of disc herniation to the QST test site and the mechanical PPT thresholds with the lowest pain thresholds closest to the level of disc herniation (slope, 6.1; 95%CI 1.79 to 10.4; p = 0.005). There was no association for HPTs. Pain thresholds were associated with the level of disc herniation when measured with mechanical pressure but not with heat.