One week of systemic antibiotics was non-inferior to four after bone infection surgery with local antibiotics

Design

Multicentre, open-label, randomised non-inferiority trial with blinded adjudication

Population

500 adults after surgery for orthopaedic infection with a local-antibiotic carrier

Primary outcome

Definite treatment failure by 12 months

Effect

11.1% vs 14.1%; risk difference −3.0 points (95% CI −9.0 to 3.0)

SOLARIO randomised 500 adults who had surgery for orthopaedic infection — including fracture-related infection, osteomyelitis and prosthetic joint infection — with an implanted local-antibiotic carrier to a short (7 days or fewer) or long (4 weeks or more) course of postoperative systemic antibiotics. A blinded committee judged treatment failure.

Definite failure by 12 months occurred in 11.1% of the short group and 14.1% of the long group (risk difference −3.0 percentage points, 95% CI −9.0 to 3.0), within the 10-point non-inferiority margin. Per-protocol and sensitivity analyses agreed. By six weeks, symptoms possibly related to treatment affected 17.2% on the short course against 45.2% on the long course.

The key condition is the local antibiotic carrier with thorough surgical debridement. Where that is in place, weeks of systemic therapy add side effects, line complications, cost and resistance pressure without a detectable gain. The 10-point margin is wide, so this is not proof of equivalence, but the point estimate favoured the short course.

• After debridement with a local-antibiotic carrier, discuss stopping systemic antibiotics at 7 days rather than 4–6 weeks.
• This applies only when a local-antibiotic carrier was implanted; it does not cover surgery without one.
• Expect far fewer drug side effects: under one in five on the short course versus nearly half on the long course.
• Agree the duration jointly with the orthopaedic team and document it at the time of surgery.
• Keep 12-month follow-up for signs of relapse whatever the course length.

Why it matters

It challenges the long-held belief that bone infection always needs six weeks of systemic antibiotics.

Don't overread it

The result depends on an implanted local-antibiotic carrier and does not apply to surgery without one.

The statistics, in plain English

Non-inferiority asks whether a short course is 'not unacceptably worse'. The margin was 10 percentage points; the worst-case estimate was 3.0 points worse, well inside it, and the best estimate was 3.0 points better. A 10-point margin is generous, so the trial cannot exclude a small disadvantage.

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