The Effect of Ultrasound-Guided PRP Injection Versus Corticosteroid Injection on Pain Relief and Functional Improvement in Patients with Low Back Pain due to Lumbar Facet Joint Involvement: A Double-Blind, Non-Inferiority Clinical Trial

Evaluation and comparison of the effects of PRP and corticosteroid injections on pain reduction and functional improvement in patients with lumbar facet joint syndrome, using the Visual Analog Scale, Oswestry Disability Index, and Roland–Morris Disability Questionnaire at baseline, 1 month, and 3 months after the intervention

A Phase III randomized, double-blind, controlled clinical trial with parallel groups, conducted on 30 patients. Restricted randomization (block randomization) was used for allocation, and random number–generation software such as R was employed to randomly select the generated blocks

After obtaining informed consent, patients are randomly assigned to two groups: A (triamcinolone) and B (PRP). VAS, ODI & RDQ assessments are performed at baseline and at 1 and 3 months after the intervention. Periarticular injection of the affected lumbar facet joint is performed by a specialist in Physical Medicine and Rehabilitation at Shariati Hospital, Tehran, under ultrasound guidance. Blinding is ensured by uniform blood sampling, prone-position injections, and identical injection volume and technique, with data analyzed using coded groups (A/B) to maintain analyst blinding.

Adults 18–65 years with chronic low back pain (>3 months), VAS >4, failure of conservative treatment, normal lower limb strength, unilateral lumbar facet–origin pain, and single-level facet involvement are included; those outside this age range, with pain <3 months, VAS ≤4, lower limb weakness, or multilevel facet involvement are excluded.

A(Control): Periarticular injection of 1 mL triamcinolone (40 mg) combined with 2 mL of 2% lidocaine B: Periarticular injection of 2.5 mL platelet-rich plasma combined with 0.5 mL of 2% lidocaine

Pain intensity, functional disability, physical disability

We will use restricted randomization, specifically block randomization, in this study. Blocking is commonly used to achieve balance in the number of participants allocated to each study group. This feature helps researchers ensure equal group sizes, particularly when interim analyses are required during the sampling process. All blocks will be of equal size, and in this two-arm trial we will have three blocks of size 10, each consisting of 5 participants in the intervention group and 5 participants in the control group. Random selection of the generated blocks will be performed using random number–generation software such as R, and three random numbers from 1 to 3 will be generated to select the blocks. For allocation concealment, we will use allocation concealment, which refers to the method used to implement the random sequence among study participants in such a way that the assigned group is not known prior to allocation. This will be achieved using sequentially numbered, sealed, opaque envelopes (SNOSE). In this method, each generated random sequence is recorded on a card, and the cards are placed sequentially inside envelopes. To preserve the random sequence, the envelopes are numbered in the same order on their outer surface. The envelopes are then sealed and placed sequentially in a box. At the start of participant enrollment, based on the order of entry of eligible participants into the study, the envelopes are opened sequentially, and the allocated group for each participant is then revealed.

This study is a double-blind randomized clinical trial with two parallel groups, in which both the patients and the data analyst are blinded to group allocation. To ensure patient blinding, blood samples will be taken from all patients (with a smaller volume drawn from the corticosteroid group), and all patients will receive the injection in the prone position. Patients will remain unaware of the substance being injected. To maintain blinding of the analyst—who is an individual other than the physician/investigator and the data collection personnel—the data will be provided for analysis coded only as Group A and Group B, without revealing the actual group assignments.