Chiropractic spinal manipulation and the risk for acute lumbar disc herniation: a belief elicitation study.

Purpose: Chiropractic spinal manipulation treatment (SMT) is common for back pain and has been reported to increase the risk for lumbar disc herniation (LDH), but there is no high quality evidence about this. In the absence of good evidence, clinicians can have knowledge and beliefs about the risk. Our purpose was to determine clinicians' beliefs regarding the risk for acute LDH associated with chiropractic SMT.

Methods: Using a belief elicitation design, 47 clinicians (16 chiropractors, 15 family physicians and 16 spine surgeons) that treat patients with back pain from primary and tertiary care practices were interviewed. Participants' elicited incidence estimates of acute LDH among a hypothetical group of patients with acute low back pain treated with and without chiropractic SMT, were used to derive the probability distribution for the relative risk (RR) for acute LDH associated with chiropractic SMT.

Results: Chiropractors expressed the most optimistic belief (median RR 0.56; IQR 0.39-1.03); family physicians expressed a neutral belief (median RR 0.97; IQR 0.64-1.21); and spine surgeons expressed a slightly more pessimistic belief (median RR 1.07; IQR 0.95-1.29). Clinicians with the most optimistic views believed that chiropractic SMT reduces the incidence of acute LDH by about 60% (median RR 0.42; IQR 0.29-0.53). Those with the most pessimistic views believed that chiropractic SMT increases the incidence of acute LDH by about 30% (median RR 1.29; IQR 1.11-1.59).

Conclusions: Clinicians' beliefs about the risk for acute LDH associated with chiropractic SMT varied systematically across professions, in spite of a lack of scientific evidence to inform these beliefs. These probability distributions can serve as prior probabilities in future Bayesian analyses of this relationship.