Multivariable Analysis of the Relationship Between Pain Referral Patterns and the Source of Chronic Low Back Pain

Background: Discogenic, facet joint, and sacroiliac joint mediated axial low back pain maybe associated with overlapping pain referral patterns into the lower limb. Differences betweenpain referral patterns for these three structures have not been systematically investigated.Objective: To examine the individual and combined relationship of age, hip/girdle pain, legpain, and thigh pain and the source of internal disc disruption (IDD), facet joint pain (FJP), orsacroiliac joint pain (SIJP) in consecutive chronic low back pain (CLBP) patients.Design: Retrospective chart review.Setting: Community based interventional spine practice.Patients: 378 cases from 358 consecutive patients were reviewed and 157 independentcases from 153 patients who underwent definitive diagnostic injections were analyzed.Methods: Charts of consecutive low back pain patients who underwent definitive diagnosticspinal procedures were retrospectively reviewed. Patients underwent provocation lumbardiscography, dual diagnostic medial branch blocks, or intra-articular diagnostic sacroiliacjoint injections based on clinical presentation. Some subjects underwent multiple diagnosticinjections until the source of their chronic low back pain (CLBP) was identified.Main Outcome Measurements: Based on the results of diagnostic injections, subjectswere classified as having IDD, FJP, SIJP, or other. The mean age/standard deviation and thecount/percentage of patients reporting hip girdle pain, leg pain, or thigh pain were estimatedfor each diagnostic group and compared statistically among the IDD, FJP, SIJP, and other sourcegroups. Next, the 4 predictor variables were simultaneously modeled with a single multinomiallogistic regression model to explore the adjusted relationship between the predictors and thesource of CLBP.Results: The mean age was significantly different among the source groups. IDD cases weresignificantly younger than FJP, SIJP, and other source groups and FJP cases were significantlyyounger than other sources. The age by thigh pain interaction effect was statistically significant(P = 0.021), indicating that the effect of age on the source of CLBP depends on thigh pain, andsimilarly, that the effect of thigh pain on the source of CLBP depends on age.Limitations: Retrospective study design.Conclusions: The presence or absence of thigh pain possesses a significant correlationon the source of CLBP for varying ages, whereas the presence of hip/girdle pain or legpain did not significantly discriminate among IDD, FJP, or SIJP as the etiology of CLBP.Younger age was predictive of IDD regardless of the presence or absence of thigh pain.Key words: low back pain, intervertebral disc, zygapophyseal joint, sacroiliac joint, painreferral patterns