Design: Multicentre, open-label, randomised non-inferiority trial (SOLARIO)
Population: 500 adults after surgery for orthopaedic infection with implanted local-antibiotic carrier
Primary outcome: Definite treatment failure by 12 months, blinded adjudication
Effect: 11.1% vs 14.1%, difference −3.0 points (95% CI −9.0 to 3.0); margin 10 points

SOLARIO was a multicentre, open-label, non-inferiority trial. Adults who had surgery for orthopaedic infection and had a local-antibiotic carrier implanted at operation were randomised to postoperative systemic antibiotics for at least four weeks or at most seven days.

Among 475 analysed, definite treatment failure by 12 months (judged by a blinded committee) was 11.1% with the short course and 14.1% with the long (difference −3.0 points, 95% CI −9.0 to 3.0), inside the 10-point margin. Per-protocol and sensitivity analyses agreed. Symptoms potentially related to treatment by week 6 fell from 45.2% to 17.2%.

Orthopaedic infection has been treated with weeks of systemic antibiotics largely by convention. This trial shows that when surgery is done well and local antibiotics are placed, a week is enough — with far less toxicity and exposure to resistance. The finding applies to that setting; it does not cover infections managed without surgical debridement or local antibiotics.

After debridement with a local-antibiotic carrier, plan systemic antibiotics for about seven days rather than four to six weeks.
Expect fewer side-effects: treatment-related symptoms fell from 45% to 17%.
The result applies only when a local-antibiotic carrier was implanted at surgery.
Agree the stop date with the orthopaedic and microbiology teams at the time of surgery.
Shorter courses reduce line complications and antimicrobial resistance pressure.

Why it matters

It challenges one of the longest default antibiotic courses in hospital medicine.

The statistics, in plain English

Non-inferiority was shown because the worst plausible result for the short course (3 points more failure) sits well within the 10-point margin the investigators set in advance. The drop in side-effects (28 points, 95% CI 19.6–36.4) is a clear, separate benefit.