The association between disk degeneration (DD) on MRI and low back pain (LBP) remains controversial and different studies report conflicting findings. There are many possible reasons for the conflicting findings including the setting or patient population, study design, analysis used and, probably most importantly, how both DD and back pain status are measured. A key issue for almost all studies in this area is how to define DD and rate an individual as having it or not. Most studies use a scale such as that reported by Pfirrmann et al. to quantify DD at each lumbar level; however, there is no agreed threshold (e.g., 3/5 or 4/5) before someone is considered to have clinically relevant DD. It is also not known if the association between DD and LBP is significantly stronger when DD is measured on a continuous scale (e.g., 1 to 5), than when dichotomized at any single threshold. A related issue is whether DD for an individual should be based on the single worst level or on a summary score from multiple levels. For example, is a person with minimal DD at all levels apart from one level with severe DD more or less likely to have LBP than a person who has three levels with moderate DD? Both the worst single level and summary score approach to rating DD are used in the literature and it is possible that one approach is more strongly related to the presence of LBP. Therefore, the aims of this secondary exploratory analysis were as follows: (1) assess different thresholds of the Pfirrmann et al1 scale to determine if an optimal threshold exists for differentiating people with and without LBP, (2) compare findings obtained from different thresholds to a continuous score from the Pfirrmann scale, and (3) compare findings based on an individual's worst DD score at any level to summary scores from multiple levels.
Hancock, M., Maher, C., Macaskill, P., Latimer, J., Kos, W., & Pik, J. (2012). Does the criterion used to measure disk degeneration alter the association between disk degeneration and low back pain. Global Spine Journal, 2(Suppl. 1), 1. https://doi.org/10.1055/s-0032-1319872