Antibiotic in the graft: a 1,100-patient test of a habit many units already have

Design

International, randomised, double-blind, placebo-controlled trial protocol

Population

1,100 patients undergoing total hip arthroplasty requiring bone grafting, excluding revision for active infection

Primary outcome

Time to reoperation for infection or diagnosis of prosthetic joint infection

Effect

Not reported; the trial is powered to detect a 50% relative risk reduction

Local antibiotic delivery in arthroplasty has spread ahead of its evidence. Antibiotic-loaded cement is standard in much of the world; loading morsellised bone graft with antibiotics is done in some units on the strength of small series and a plausible mechanism, and not done in others for exactly the same reason.

ABOGRAFT is designed to settle it. It is an international, randomised, double-blind, placebo-controlled drug trial enrolling 1,100 patients undergoing total hip arthroplasty who require bone grafting, excluding revisions for ongoing infection. Patients are randomised 1:1 to graft impregnated with tobramycin and vancomycin or to placebo-impregnated graft. The primary outcome is time to reoperation for infection or to a diagnosis of prosthetic joint infection, and the trial treats a 50% relative risk reduction as the clinically relevant threshold. Secondary outcomes run to five years and include the organisms cultured and their susceptibility patterns, which is the part most likely to matter beyond this question. Safety outcomes include revision for aseptic loosening — the concern being that antibiotic loading might impair graft incorporation.

Nothing changes today; no results exist. The reason to note it now is the susceptibility endpoint. If local vancomycin and tobramycin shift the organisms that cause the infections that still occur, that is a stewardship finding with implications well outside hip surgery, and it will be reported from this trial whichever way the primary outcome falls.

• Keep systemic prophylaxis timing and dosing tight — that evidence is not in question.
• If your unit loads graft with antibiotics, record it in the operation note so outcomes are traceable.
• Watch the susceptibility endpoint, not only the infection rate, when this reports.
• Do not adopt the practice now on the basis of a trial designed because the practice is unproven.

Why it matters

A widespread surgical habit is finally being tested against placebo rather than against opinion.

Don't overread it

This is a protocol — it reports no outcomes and demonstrates no benefit.

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