"The most likely source of infection not under control by standard aseptic precautions appeared to be the air of the operating room. It was therefore decided to build a clean-air operating enclosure."

Early operations at Wrightington were performed in a standard operating enclosure. With the infection rate at over 7%, Charnley knew it was imperative to find ways of reducing the rate and he set out to develop a clean air operating environment.

The clean air operating enclosure or "Greenhouse" as it was first known was developed, prototyped and built at Wrightington in 1962 by Charnley in co-operation with Hugh Howorth of Howorth Engineering. The objective was to provide filtered particles and thus bacteria-free air in a unidirectional downward flow pattern at a high enough rate to overcome particle carrying up-currents. After detailed testing over the next few years the infection rate reduced to 1.3%.

The total body exhaust system was the extension of the principle: to contain the operating team within the comfort of fresh air under negative pressure and thus minimise the risk of wound contamination.

The Instrument tray concept became part of the system with a fresh set of instruments available for each stage of the operation.

By 1972 with improvements in the design of the operating enclosure and surgical gowns the infection rate was 0.3%.

But: "Deep infection after this operation can never be overlooked... if sufficient time is allowed to elapse."

Click here to visit the manufacturer of the clean-air operating enclosure, Howorth Medical.