Assessing Residual Moisture After Sterilization as an Overlooked Source of Intraoperative Bacterial Contamination in Knee Intra-articular Reconstructions: Evaluating the Reliability of Routine Procedures and Tests
Authors: Malinowski Konrad , Bawor Michalina , Woon Kim Dong , Pękala Przemysław A. , Skowronek Paweł , Hirschmann Michael T. , Domżalski Prof. Marcin , LaPrade Robert F. , Mostowy Marcin 
Published: January 2025

Background: Contamination of sterilized surgical instruments is not a typically suspected source of increased infection rate, especially if no abnormalities in the sterilization process are detected. Purpose/Hypothesis: The purpose of this study was to report increased infection rates after knee ligament reconstructions due to undetectable sterilization process errors leading to residual moisture, not limited to a specific surgical tool. It was hypothesized that (1) residual moisture on surgical tools due to autoclave overloading would not be detected by autoclave self-diagnostics, chemical and biological tests, or organoleptic assessment and (2) this kind of contamination may elevate infection rates, especially in knee intra-articular reconstruction procedures. Study Design: Case series; Level of evidence, 4. Methods: A retrospective analysis of increased postoperative knee infection rate between January 2013 and January 2015 was performed. The inclusion criteria were all articular procedures. The exclusion criteria were joint arthroplasties, fractures, and open joint wounds. Criteria defining postoperative joint infections were as follows: (1) pain and effusion relapse and loss of achieved range of motion; (2) opaque/cloudy fluid on arthrocentesis; (3) fever >37.5°C lasting ≥3 days; and (4) ≥2-fold elevation in C-reactive protein levels, with symptoms onset within 21 days postoperatively. A negative culture result did not exclude a postoperative joint infection diagnosis and treatment. The data were summarized, and the infection rates of given subgroups were compared with a 2-tailed Fisher exact test. A risk ratio (RR) with 95% CIs was calculated. Results: Out of 533 orthopaedic procedures screened for inclusion, 4 joint arthroplasties, 7 fractures, and 2 open joint wounds were excluded. The remaining 520 articular procedures were included in the study—118 knee cruciate ligament reconstructions, 130 knee nonreconstruction arthroscopies, and 272 knee extra-articular/other joints arthroscopic and sports procedures. A total of 21.2% of knee intra-articular ligament reconstructions were complicated by postoperative joint infections, compared with 1.5% of knee nonreconstruction arthroscopies (RR, 13.8 [95% CI, 3.3-56.9]; P < .001) and 0.4% of knee extra-articular/other joints arthroscopic and sports procedures (RR, 57.6 [95% CI, 7.9-420.4]; P < .001). The source of the increased infection rate was identified as residual moisture on surgical tools due to autoclave overloading. This residual moisture was not detected by autoclave self-diagnostics, chemical and biological tests, or organoleptic assessment. After reducing the insert of surgical tools in the autoclave, the infection rate in the next 2 years after knee reconstructive procedures returned to <1% ( P < .001). Conclusions: Our study demonstrated that residual moisture after the sterilization process may be an underestimated source of postoperative joint infections, undetectable in routine procedures and tests. Overcrowding of surgical equipment in the autoclave may be a root cause of this residual moisture identified. This kind of contamination may elevate the infection rate, especially in knee intra-articular reconstruction procedures.