Charnley tracked deep infection across 5,800 THRs at Wrightington over 10 years, systematically varying OR air cleanliness through four phases. The central question: how much of prosthetic joint infection is truly air-borne, and what is the theoretical floor achievable with maximal OR asepsis? No antibiotic prophylaxis was used, making this a pure study of environmental control.
Surgeons in 1960 suspected acrylic cement was causing THR infections through chemical toxicity or blood-borne seeding — neither was testable without first controlling for the OR environment. Charnley's decade-long natural experiment, deliberately avoiding antibiotics, made the operating room itself the only variable.
The practical rule from this paper: when you see a reported THR infection rate under 1% in a series of 300–500 cases with under 2 years of follow-up, discount it. The statistics don't support it, and late-manifesting infections have not yet declared themselves.
When counseling patients or reviewing institutional data, apply the 25% correction: infection rates at 18 months will rise by at least a quarter over the next 3–4 years. A center reporting 0.5% at 1 year may be reporting 0.7–1.0% at 5 years.
This paper is the direct foundation for ultraclean air enclosures, body-exhaust systems, and impermeable gown materials in arthroplasty. Technology formalized in Lidwell's 1982 MRC RCT and now standard in high-volume centers. The insight that gown permeability (not air) is the binding constraint below 1.5% remains the reason modern arthroplasty theaters use laminar flow in combination with specialized surgical attire, not laminar flow alone.
Charnley tracked deep infection across 5,800 THRs at Wrightington over 10 years, systematically varying OR air cleanliness through four phases. The central question: how much of prosthetic joint infection is truly air-borne, and what is the theoretical floor achievable with maximal OR asepsis? No antibiotic prophylaxis was used, making this a pure study of environmental control.
Surgeons in 1960 suspected acrylic cement was causing THR infections through chemical toxicity or blood-borne seeding — neither was testable without first controlling for the OR environment. Charnley's decade-long natural experiment, deliberately avoiding antibiotics, made the operating room itself the only variable.
The practical rule from this paper: when you see a reported THR infection rate under 1% in a series of 300–500 cases with under 2 years of follow-up, discount it. The statistics don't support it, and late-manifesting infections have not yet declared themselves.
When counseling patients or reviewing institutional data, apply the 25% correction: infection rates at 18 months will rise by at least a quarter over the next 3–4 years. A center reporting 0.5% at 1 year may be reporting 0.7–1.0% at 5 years.
This paper is the direct foundation for ultraclean air enclosures, body-exhaust systems, and impermeable gown materials in arthroplasty. Technology formalized in Lidwell's 1982 MRC RCT and now standard in high-volume centers. The insight that gown permeability (not air) is the binding constraint below 1.5% remains the reason modern arthroplasty theaters use laminar flow in combination with specialized surgical attire, not laminar flow alone.