Carette 1991

This initial phase was designed to identify patients with chronic low back pain who would likely respond to facet-joint injections.
Patients underwent an initial diagnostic injection of lidocaine into the affected facet joints.
Only those patients who experienced a significant pain reduction (at least 50 percent) after this lidocaine injection were considered eligible to proceed to the next phase.
Out of 190 patients who entered Phase I, 110 (58 percent) reported a pain reduction of 50 percent or more. From these, 101 patients proceeded to Phase II after some exclusions.

This phase was a randomised, controlled, blind-observer trial.
It was designed to evaluate the efficacy of methylprednisolone injections into the facet joints.
Patients who met the criteria from Phase I were randomly assigned to receive either methylprednisolone acetate or isotonic saline placebo injections into their facet joints.
Both patients and the assessing investigators were unaware of the treatment being administered.

This was a single-centre study, conducted at the Centre Hospitalier de l'Université Laval in Quebec City, Canada.

Randomised, controlled, and blind-observer, meaning patients, the injecting physician, and the assessing investigator were unaware of the treatment received.

Injections were performed into the L5-S1, L4-L5, and L3-L4 facet joints, unilaterally or bilaterally, guided by the location of pain.
All injections were administered under fluoroscopic or computed tomographic (CT) guidance to ensure intraarticular placement.
The study aimed for a series of injections, with a mean of 7.2 injections for the methylprednisolone group and 7.1 for the placebo group over 14 weeks.

Average total number of separate injection procedures that each patient in that respective group received throughout the study period

Patients referred to a rheumatology outpatient clinic.
Age between 18 and 65 years old.
History of chronic low back pain and/or buttock pain lasting at least six months.
Pain intensity of at least 50 mm on a 100-mm visual analogue scale (VAS).
Radiologic confirmation of facet joint arthropathy corresponding to the area of pain.
Demonstrated reduction of pain by at least 50 percent after an initial injection of lidocaine into the affected facet joints (to confirm the facet joint as the pain source).

Presence of radicular pain.
Other medical conditions that could interfere with findings of nonradicular low back pain, such as medical illness, tumour, infection, or spondylolisthesis.
Previous facet joint injection within six months.
Pregnancy.
Known allergy to local anaesthetic or radiologic contrast media.
Presence of a blood coagulation disorder.

Both the methylprednisolone and placebo groups showed a marked decrease in initial pain severity.
At the 2-month interval, pain decreased by 49 percent in the methylprednisolone group and 52 percent in the placebo group.
At the 6-month interval, pain decreased by 50 percent in the methylprednisolone group and 53 percent in the placebo group.
There was no significant difference between the two groups in VAS scores for pain at 1, 2, 3, or 6 months. For instance, at 6 months, the mean VAS score was 5.0 for methylprednisolone versus 4.9 for placebo.

Secondary efficacy endpoints: Changes in functional status and back pain disability.
Assessed using the McGill Pain Questionnaire (MPQ), Sickness Impact Profile (SIP), and other measures like number of days of bed rest, restricted main activity, and finger-to-floor distance.
Results:

No significant difference was observed between the methylprednisolone and placebo groups on any secondary outcomes at 1, 2, 3, or 6 months.
For example, at 6 months, the MPQ score improved by 29 percent in the methylprednisolone group and 24 percent in the placebo group (P=0.79).
The SIP physical dimension improved by 28 percent in the methylprednisolone group and 12 percent in the placebo group at 6 months (P=0.42).
The authors concluded that "neither clinical nor statistically significant differences were observed between the two study groups" for functional status or back pain disability.

Injections of methylprednisolone into facet joints are of "little value" in the treatment of patients with chronic low back pain.
The study found no measurable benefit or earlier improvement with methylprednisolone compared to placebo.
The results for pain, functional status, and back pain disability were not significantly different from placebo.
The long-term benefit of methylprednisolone was not demonstrated.

It was a randomised, controlled, blind-observer clinical study, a robust design for evaluating treatment efficacy.
Careful patient selection using a diagnostic lidocaine injection aimed to ensure that the facet joints were the likely source of pain in enrolled patients.
Fluoroscopic or CT guidance was used for all injections, ensuring accurate intraarticular placement of the study medications.
The study used validated and widely accepted scales (VAS, MPQ, SIP) for comprehensive outcome assessment.
It included a relatively long follow-up period of up to six months, allowing for assessment of sustained effects.

It was a single-centre study, which may limit the generalisability of the findings to a broader population.
The study found no significant difference between the active treatment (methylprednisolone) and placebo, indicating a lack of efficacy for corticosteroid injections in this context.
A high placebo effect was observed, with a significant proportion of patients in the placebo group also reporting marked improvement, making it difficult to demonstrate a superior effect of the active treatment.
A substantial number of screened patients (42 out of 100) did not enter the randomised trial after the initial lidocaine injection phase.
The authors noted that the patient selection method based on lidocaine response "may not ensure an objectively verifiable diagnosis".