Presentation, outcome, and cause of septic arthritis after anterior cruciate ligament reconstruction: a case control study.

PURPOSE: The objective of this study was to examine clinical presentation and medium-term outcome of patients with septic arthritis of the knee after anterior cruciate ligament (ACL) reconstruction. TYPE OF STUDY: Matched case control study.
METHODS: From a consecutive case series of 575 patients who underwent ACL reconstruction from 1996 through 1999, we report on 10 patients (1.7%) with postoperative septic arthritis. These patients were compared with individually matched patients without infection, on average, 3 years after surgery. The examination included physical and radiographic evaluation, functional testing, KT-1000, Lysholm and Tegner scales, and the International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) form.
RESULTS: The predominant clinical presentation among patients with septic arthritis was modest classic signs of local infection. However, all had fever and elevated sedimentation rate or high C-reactive protein. Bacterial cultures showed coagulase-negative Staphylococcus species in 6, Staphylococcus aureus in 1, and Propionibacteriaceae species in 1 patient. The diagnosis was established with a delay of approximately 5 days. All patients underwent arthroscopic debridement and lavage (2 cases) or continuous irrigation (8 cases), as well as antibiotic treatment. One experienced graft rupture caused by the infection. At the end of the follow-up evaluation, the infected patients reported significantly lower activity levels than the control subjects (mean Tegner score, 5.3 v 7.2, P =.03). No statistically significant differences were noted in mean Lysholm, IKDC, or KOOS scores, or in KT-1000 difference. Two infected patients scored lower on the Tegner and Lysholm scales postoperatively than they did preoperatively. When examining the causes of infection, we found contamination by coagulase-negative Staphylococcus on supposedly sterile suture clamps on 3 graft preparation boards.
CONCLUSIONS: In cases of suspected septic arthritis after ACL reconstruction, laboratory studies and aspiration followed by culture testing should be performed liberally to avoid the otherwise frequently delayed diagnosis. The inferior postoperative activity level noted in infected patients appeared not to be secondary to graft failure but may be related to arthrofibrosis, cartilage damage, or recurring postinfectious meniscal tears.