For chronic back pain, there is no usable paracetamol trial left
A Cochrane search found three placebo-controlled trials in low back pain. The only one covering chronic pain has since been withdrawn, and none was ever found for the subacute form.
What the study found
Chronic back pain's only paracetamol trial has been retracted
A Cochrane search for placebo-controlled trials of paracetamol in non-specific low back pain found three. One covered chronic pain and has since been withdrawn from the record, so nothing can be concluded there. For the subacute form no trial was ever found in the first place.
The caveat · Strict rules excluded most trials
A retracted trial leaves an absence of evidence, not evidence that the drug fails, and only the first of those is true here. Cochrane's inclusion rules were strict, which is why three trials survived a search of a much larger literature. This covers low back pain with no identified cause, not back pain traced to a known injury or disease.