Editor’s note: The following content was published in the AAOS Now Special Edition and distributed in June 2020. The content was originally scheduled for the AAOS Now Daily Edition, which publishes each year onsite at the AAOS Annual Meeting but this year’s meeting in March was canceled due to COVID-19. Despite the cancellation, members can access virtual content from the Annual Meeting by visiting the Academy’s Annual Meeting Virtual Experience webpage.

A study found that patients who have knee arthroscopy then primary total knee arthroplasty (TKA) in the same knee are at a greater risk of developing surgical site infections (SSIs). Nipun Sodhi, MD, of Long Island Jewish Medical Center at Northwell Health, presented the data as part of the Annual Meeting Virtual Experience.

“Some studies in the current literature indicate that previous arthroscopy does not impact post-surgical outcomes or TKA survivorship, while other studies argue the contrary,” Dr. Sodhi told AAOS Now. “Understanding the association between previous knee arthroscopy and post-surgical infection has become increasingly important as more patients undergo TKA following these more conservative procedures.”

Researchers retrospectively queried an administrative claims database from Jan. 1, 2005, to March 31, 2015, and identified patients who underwent knee arthroscopy within one year prior to primary TKA via Current Procedural Terminology codes.

The researchers took TKA patients who had a history of arthroscopy (n = 85,615) and matched them 1:3 based on age, sex, and Elixhauser Comorbidity Index (ECI) to control TKA patients without a history of arthroscopy (n = 256,842). ECI is a well-validated tool comprised of 31 comorbidities and was used to ensure that the cohorts were appropriately matched to reduce the effects of potential confounders, according to the authors. The mean (± standard deviation) ECI for both cohorts was 7 ± 4.

Researchers assessed 90-day risks of SSIs and periprosthetic joint infections (PJIs), as well as readmission rates.

Patients who had knee arthroscopy followed by primary TKA had greater incidence and odds of SSIs (0.95 percent versus 0.84 percent; odds ratio [OR], 1.11; 95 percent confidence interval [CI], 1.03–1.21; P = 0.006) within 90 days of primary TKA compared to matched controls.

“Orthopaedic surgeons should take these findings into account when considering knee arthroscopy as management for isolated osteoarthritis and should reserve this procedure for patients who have other knee pathologies,” said Dr. Sodhi. “Additionally, prior knee arthroscopy within one year can be part of a patient’s risk stratification for postoperative infection following TKA.”

Compared to matched controls, patients who had knee arthroscopy within the prior year also had greater incidence and odds of developing PJIs (0.68 percent versus 0.64 percent; OR, 1.07; 95 percent CI, 0.97–1.17; P = 0.163) within 90 days of primary TKA, although this was not statistically significant. “It might have been expected that PJIs would also have been significantly increased given that knee arthroscopy violates the joint capsule; however, these data reveal this may not necessarily be the case,” said Dr. Sodhi.

“Future studies should aim to identify the time interval most associated with infections following TKA in patients who have had prior knee arthroscopy,” said Dr. Sodhi. “Future analyses should also explore prophylactic algorithms that may reduce infection risk through patient optimization. Importantly, more studies are needed to determine whether knee arthroscopy should be considered a safe and effective method of delaying TKA.”

The study is limited by its retrospective nature and use of claims data. In addition, the study did not control for certain factors, such as the specific arthroscopy procedure performed, surgeon experience, or hospital volume.

Dr. Sodhi’s coauthors of Poster 394, “Knee Arthroscopy Prior to Total Knee Arthroplasty Increases the Risks for Surgical Site Infections and Periprosthetic Joint Infections: An Analysis of 342,457 Patients,” are Rushabh Vakharia, MD; Hiba K. Anis, MD; Joseph O. Ehiorobo, MD; Peter A. Gold, MD; Luke J. Garbarino, MD; Peter M. Bonutti, MD; Michael A. Mont, MD; and Martin W. Roche, MD.

Kerri Fitzgerald is the managing editor of AAOS Now. She can be reached at kefitzgerald@aaos.org.