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Surgical site infections after arthroscopy: Outbreak investigation and case control study
Hilary M Babcock1, Cathy Carroll, Matthew Matava
1Infectious Disease Division, Department of Internal Medicine, Washington University School of Medicine, St Louis, Missouri, USA. hbabcock@im.wustl.edu
Purpose:
The goal of this study was to determine the causes of increased post-arthroscopy surgical site infections (SSIs) and to define risk factors for infection.
Type Of Study:
Outbreak investigation and case control study at a university-affiliated community hospital from 1994 to 1996, with surveillance through 1999.
Methods:
Demographic, clinical, and microbiological data were collected on 27 post-arthroscopy SSIs from 1994 through 1999. Risk factors for SSI were identified by case-control analysis and presented as odds ratios (OR) and 95% confidence intervals (CI).
Results:
Initial investigation revealed an increased annual rate of post-arthroscopy SSIs in 1995 (1.3%). Infection control deficiencies were identified, and feedback was provided to surgeons and staff. Instrument sterilization was standardized, flash sterilization prohibited, and preoperative shaving discouraged. Case-control analysis of 10 cases (from 1994 to 1996) found a statistically significant increase in risk of SSI with intra-articular corticosteroid joint injection (OR, 9.33; 95% CI, 1.6 to 64.9); other risk factors did not reach statistical significance. SSI rates dropped after feedback and education (0.34% in 1996). Continued surveillance revealed 2 smaller outbreaks, in December 1997 (1997 rate, 1.13%) and September 1998 (1998 rate, 1.09%). Case-control analysis of the 17 cases occurring in 1997 through 1999 was also performed. The 1997 outbreak appeared to be related to preoperative razor shaving (P =.003), which was then prohibited by hospital policy. One scrub nurse was also associated with 75% of these cases, which were culture-positive for coagulase-negative Staphylococcus. The cases in the 1998 outbreak shared prolonged procedure duration and conversion to arthrotomy. Of 27 cases, 24 required repeat hospitalization and repeat surgery, at an average excess cost of $9,154.84 per case. All received prolonged courses of intravenous or oral antibiotics.
Conclusions:
Post-arthroscopy SSIs are associated with significant morbidity and cost. Although small numbers make finding statistical significance difficult in case-control studies, infection control and CDC-recommended interventions can lower SSI rates. Careful definitions, ongoing surveillance, and long-term follow-up are helpful in reporting results of infection control interventions.