Paper of the week: Humidity a potential risk factor for prosthetic joint infection in a tropical Australian hospital. Armit D, Vickers M, Parr A, Van Rosendal S, Trott N, Gunasena R, Parkinson B. ANZ J Surg. 2018 Dec;88(12):1298-1301. doi: 10.1111/ans.14916. Epub 2018 Oct 24.
This study aims to determine the role of humidity as a risk factor for the development of prosthetic joint infection (PJI) in total knee replacement patients. In this single-center retrospective study researchers looked at the incidence of deep PJI and correlated with daily weather data. Deep PJI was diagnosed using the Australian Commission on Safety and Quality in Health Care criteria for deep incisional organ space infection. Weather variables used for analysis was relative humidity and apparent temperature on the day of the primary procedure. Results showed humidity more than 60% (OR 1.4) and apparent temperature more than 30-degree centigrade (OR 2.4) are possible potential risk factors for the development of deep PJI. However, these variables were not statistically significant.
A Study by Parkinson et al. based on Australian Orthopaedic Association National Joint Replacement Registry, have shown higher PJI incidence in tropical regions (0.73%) compared to the non-tropical areas (0.37%).  Their results also showed seasonal variation in the tropical areas with a higher incidence in summer/fall (0.98%) compared to winter/spring (0.51%). Hot and humid weather increases sweating and provide conditions to bacterial growth which might explain the reason behind the increase in infection. One issue with the above study is that weather variables were recorded on the day of surgery, where the patient is indoors, and air conditioning would provide a constant stable environment inside the hospital.
 Parkinson B, Armit D, McEwen P, Lorimer M, Harris IA. Is Climate Associated With Revision for Prosthetic Joint Infection After Primary TKA? Clin Orthop Relat Res 2018;476:1200–4. doi:10.1007/s11999.0000000000000144.