Bush 1991.

Methods	Placebo‐controlled trial Source: hospital rheumatology department Country: UK
Participants	23 patients randomised (Group 1 = 12, Group 2 = 11); Diagnosis: clinical assessment Mean age (SD): Group 1 = 38.2 years (13.4), Group 2 = 37.3 years (8.0); Duration of symptoms: acute (< 1 month)
Interventions	Group 1: epidural injection of 25 mL containing triamcinolone acetonide (80 mg) plus procaine hydrochloride (0.5%) plus saline Group 2: epidural injection of saline (25 mL)
Outcomes	Pain intensity: overall pain (VAS); Adverse events: proportion of patients experiencing adverse events Follow‐ups: 4 and 52 weeks
Notes	Epidural approach: caudal without the use of imaging guidance. Patients received 2 injections: first at admission to the trial and a second after 2 weeks. Anaesthetist's experience: not specified Co‐interventions: additional analgesics allowed.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"… the patients were randomised to receive either active or placebo treatment."
Allocation concealment (selection bias)	Unclear risk	Not mentioned.
Blinding of participants (performance bias)	Low risk	Patients were blinded to the interventions (placebo‐controlled trial using epidural approach).
Blinding of personnel/care providers (performance bias) All outcomes	High risk	The procedures are clearly different which confirm that the care providers were not blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐report outcomes with patients blinded to the treatment allocation.
Incomplete outcome data (attrition bias) All outcomes	Low risk	23 out of 28 (82%) completed the short‐term and long‐term follow‐up. Loss to follow‐up at short‐term and long‐term follow‐up were below the proposed threshold.
Intention‐to‐treat analysis (attrition bias)	Unclear risk	Not mentioned.
Selective reporting (reporting bias)	Unclear risk	The protocol of the trial was not registered by the authors.
Group similarity at baseline (selection bias)	High risk	"Statistical difference between the two groups in SLR ability".
Co‐interventions (performance bias)	Low risk	"Additional measures in the form of bed rest analgesics corsets and manipulation were allowed, only analgesics were permitted in the first four weeks."
Compliance (performance bias)	Low risk	Compliance in both groups 100%.
Timing of outcome assessment (detection bias)	Low risk	"Assessments were made at baseline 4 weeks and 1 year".
Other bias	Unclear risk	Funding and conflict of interest were not reported.