Comparing the efficacy of intra-articular injection of Platelet Rich Plasma (PRP) with corticosteroids (CS) in patients with chronic zygapophyseal joint low back pain confirmed by double intra-articular diagnostic blocks: A triple-blinded randomized multicentric controlled trial with a 6-month follow-up.

Objective: To compare the safety and effectiveness in improving function and reducing pain of autologous PRP to corticosteroid (CS) zygapophyseal (Z-joint) intra-articular (IA) injections at six months for patients with chronic osteoarthritis Z-joint mediated low back pain (LBP). Design: Prospective triple-blinded multicentric randomized controlled trial. Methods: Fifty participants with radiological signs of Z-joint OA and chronic Z-joint mediated LBP confirmed by a ≥80 % pain improvement after two IA local anesthetic injections were randomized into PRP and CS groups, using a 1:1 ratio. Participants completed questionnaires at baseline, and at 1-, 3- and 6-month post-treatment, with adverse effect data collected at 1 month. Function (Oswestry disability index (ODI)), pain (Numeric Rating Scale (NRS)), treatment satisfaction (modified MacNab criteria), and quality of life (Short Form survey 36 (SF-36)) were assessed at each follow-up. The primary outcome was the percentage of participants improving their function (ODI score) above the minimal clinically important difference (MCID) of 17 points. The secondary outcomes were the percentage of participants with a >50 % NRS improvement, satisfaction to treatment and mean score improvement. Proportions were compared between groups using a chi-square test. Mean scores were compared using a two-way ANOVA or the nonparametric Brunner & Langer test. Results: Both groups were similar at baseline, no major adverse effects occurred, and no participants were lost at follow-up. The proportion of participants improving their ODI scores above the MCID, the proportion of participants with a >50 % NRS improvement, and mean ODI scores were significantly different between groups in favor of PRP at 6 months. Modified MacNab satisfaction scale, NRS and SF36 mean scores were not statistically different between groups, but all followed the same pattern: the CS groups had a greater improvement a one month, both groups were equivalent at three months and the PRP group had a greater improvement at six months. Conclusion: This first triple-blinded multicentric RCT demonstrates the safety of PRP IA Z-joint injections and its superiority in improving pain and function at six months post-treatment compared to CS for patients with chronic OA Z-joint mediated LBP. To perform a blinded control study, two intra-articular treatments were compared. However, knowing that radiofrequency neurotomy (RFN) of the medial branch diagnosed by branch blocks has been standard of care for pain originating from Z-joints, further studies comparing PRP to RFN are still needed. Clinicaltrials gov registry number: NCT05188820.