Approach to patients with a potential prosthetic joint infection

Dear Editor,

The practice pointer by Atkin et al on an "Approach to patients with a potential prosthetic joint infection" contains excellent advice on the assessment and investigation of these patients. The authors correctly say that infected joint replacement is an horrendous complication from the patient’s point of view, commonly resulting in many months of pain and disability. The authors quote an NHS treatment cost of around £36,000 for each infection, however the wider cost to society is far larger. Data from clinical negligence settlements would suggest that the total cost to society of infected joint replacements is around £250 million per year.

It was Louis Pasteur who said that he was less interested in treatment than in the prevention of bacterial infections. This lesson has not been learned, as there is a huge amount of effort expended on researching methods of treating these infections, but comparatively little effort on prevention. Deep infection rates for joint replacement surgery have changed very little since the 1970s and there are some suggestions in the literature that infection rates are actually getting worse.

Unfortunately the article contains the suggestion that infections occurring more than two years after joint replacement are likely to be haematogenous infections, not therefore related to the actual surgery. This suggestion is dangerously complacent as it implies that operating theatre technique is of no importance in infections presenting after two years post surgery.

A review of 10,000 joint replacements at our hospital showed that substantial numbers of infections present after two years, with skin organisms such as Staph Epidermidis, which are likely to be theatre acquired. Recent evidence using genomic techniques has shown that operating theatre air is the likely infection source in clean soft tissue surgery, even when implants are not involved.

The classification of infections after 24 months as being haematogenous is derived from observational data in a paper written by Fitzgerald in 1977. This paper has been quoted in multiple subsequent publications, but it is of limited value because it does not contain information on late infection rates from different types of operating theatre, so it only provides very low grade evidence.

There is very little data in the literature to provide more robust evidence, however the original observations of John Charnley are highly relevant. Charnley’s first total hip replacements were carried out in a theatre with a low number of changes, and poor microbiology. His infection rate was greatly improved by increasing the number of changes and improving the microbiology. The patients were meticulously documented up to 5 years post surgery. Improving the air changes from up to 130 per hour to 300 per hour improved the settle plate colony count from between 0.5 and 70 colonies per hour, down to 0.0 to 0.2 per hour.

The key point is that the deep infection rate for infections presenting prior to two years improved from 2.18% to 0.97%. The infection rate for infections presenting between two and five years post surgery however improved from 0.87% to 0.28%, which is a larger improvement. This means that late presenting infections are related to operating theatre technique, unless there is microbiological proof of a different source.

Yours Sincerely,

Andrew Thomas FRCS FRCP
a.m.c.thomas@bham.ac.uk

Aitkin B, et al. Approach to patients with a potential prosthetic joint infection.
BMJ 2022;376:e069502
http://dx.doi.org/10.1136/bmj-2021-069502

Dale H et al. Increasing risk of prosthetic joint infection after total hip arthroplasty.
Acta Orthopaedica 2012; 83 (5): 449–458

Fitzgerald RH et al. Deep wound sepsis following hip arthroplasty.
J Bone Joint Surgery Am. 1977; 59A (7): 847-855

Phillips JE et al. The incidence of deep prosthetic infections in a specialist orthopaedic hospital.
J Bone Joint Surgery Br. 2006 88B (7): 943-948

Stauning MA et al. Genetic relationship between bacteria isolated from intraoperative air samples and surgical site infections at a major teaching hospital in Ghana.
J Hosp Infection. 2020 104: 309-320

Charnley J. Postoperative infection after total hip replacement with special reference to air contamination in the operating room.
Clin Orth Rel Res 1972 (87) 167-187