Seven days of systemic antibiotics after bone and joint infection surgery matched four weeks or more

Design

multicentre, open-label, randomised noninferiority trial with blinded endpoint adjudication (SOLARIO)

Population

500 adults after surgery for orthopaedic infection with implantation of a local antibiotic carrier; 475 in the primary analysis

Primary outcome

definite treatment failure by 12 months

Effect

14.1% (long, 4 weeks or more) vs 11.1% (short, 7 days or fewer); risk difference -3.0 percentage points (95% CI -9.0 to 3.0), within a 10-point noninferiority margin

SOLARIO randomised 500 adults who had undergone surgery for orthopaedic infection — and who had a local antibiotic carrier implanted at the same operation — to postoperative systemic antibiotics for at least four weeks or for no more than seven days. Definite treatment failure at 12 months, adjudicated by a blinded endpoint committee, occurred in 14.1% of the long-course group and 11.1% of the short-course group. Noninferiority was met, and the point estimate favoured the shorter course.

The condition on that result is the local carrier. This trial does not say that a week of antibiotics is enough after orthopaedic infection surgery in general; it says that where antibiotic is delivered directly into the infected site at operation, the systemic course that follows can be a week rather than a month.

The harm figure is the one to carry into the conversation. By week six, symptoms potentially related to treatment had occurred in 45.2% of patients on the long course against 17.2% on the short one — a 28 percentage point difference. Four weeks of systemic antibiotics is not a neutral act of caution, and this quantifies what it costs the patient.

For readers outside orthopaedics, the transferable point is about where the burden of proof now sits. Prolonged courses in bone and joint infection have been conventional rather than evidenced; this is the second area in a decade where a shorter regimen has held up on formal testing.

• Ask whether a local antibiotic carrier was used before assuming a long systemic course is required
• Where one was used, a seven-day systemic course is a defensible plan, not a shortcut
• Count and record antibiotic-related symptoms at follow-up — nearly half the long-course patients had them by six weeks
• Do not extrapolate to orthopaedic infection surgery without a local carrier; that was not the trial population
• Set the stop date at discharge rather than leaving duration to the review appointment

The statistics, in plain English

The risk difference was -3.0 percentage points with a 95% confidence interval from -9.0 to 3.0, against a prespecified noninferiority margin of 10 percentage points. Because the whole interval sits well inside that margin, the short course is established as noninferior; because the interval also crosses zero, the apparent advantage for the short course is not itself a proven superiority. Two sensitivity analyses in different populations gave consistent results, which matters in an open-label trial where knowledge of allocation could otherwise influence who is counted as having failed — here a blinded endpoint committee made that call.

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