The sample size was estimated using the mean difference in VAS scores for aLBP between the experimental and control groups.
The recorded secondary outcomes included patient-generated measurements of function, global rating of change, satisfaction with the intervention, whether they would accept the same treatment for a future episode of aLBP, the number of patients using intramuscular injection of parecoxib sodium for additional treatment, and adverse events.
On the first post-injection day, the patients were asked to complete a questionnaire regarding whether they would accept the same treatment during a future episode of aLBP.
The percentage of participants using intramuscular injection of parecoxib sodium for additional treatment, the percentage of adverse events, and the percentage of participants who accepted the same treatment during a future episode of aLBP in each group were calculated and compared using the chi-square test or Fisher's exact test.
The median duration of current aLBP episodes in participants at the time of enrollment was 5.4 days.
More patients in the experimental group (64%) claimed that they would want to use the same pain relief method in a future episode of aLBP than those in the control group (35%; P=0.024).
This study shows the safety and efficacy of ISWI versus placebo (isotonic saline) in patients with aLBP. ISWI provided a higher degree of pain relief and functional improvement than did placebo injections.
In aLBP, sometimes there is a brief "hyperacute" period of 24-48 h during which patients are essentially immobilized and motion is hampered by pain and intense spasm.
Notably, our study was performed in patients with various special clinical features, and this group may be different to the whole patient population that has aLBP. Therefore, these results may not be directly extrapolated to other types of patients.
Other limitations include rigorous entry criteria for aLBP, no intermediate-term and long-term follow-up, and the patients' expectations and the successfulness of the blinding attempts were not assessed.
In future studies, the maximum duration of pain relief and the effectiveness of repeated injections of sterile water in patients with aLBP should be determined.