Graft Preparation with Intraoperative Vancomycin Decreases Infection after Anterior Cruciate Ligament Reconstruction: A Review of 1640 Cases

Abstract

Objectives:Septic arthritis is a rare but devastating complication following anterior cruciate ligament (ACL) reconstruction. Reported infection rates following ACL reconstruction are low, but associated with high morbidity including reoperation and inferior clinical outcomes. The purpose of the current study was to investigate the rate of infection after ACL reconstruction with and without graft preparation with vancomycin irrigant.Methods:All ACL reconstructions performed from May 2009-August 2018 at a single, large academic institution were reviewed and categorized based on vancomycin use. Those with <90-day follow-up, intraoperative graft preparation with an antibiotic other than vancomycin, or previous ipsilateral knee infection were excluded. Infection was defined as a return to the operating room for irrigation and debridement within 90 days of ACL reconstruction. Descriptive and inferential statistical analysis using t-tests and Poisson regression were performed, with statistical significance defined as p<0.05.Results:In total, 1,640 patients (952 males; 58.0%) with a mean age of 27.7 + 11.4 years underwent ACL reconstruction (1,379 primary procedures; 84.1%) and were included for analysis. Intraoperative vancomycin was used in 798 cases (48.7%) while 842 ACL reconstructions (51.3%) were performed without intraoperative vancomycin. There were eleven total infections (0.7%), with ten infections occurring in patients without vancomycin-soaked grafts (1.2%) and one infection occurring in grafts soaked in vancomycin (0.1%; p=0.008). Age (p=0.571), gender (p=0.707), smoking (p=0.407), surgeon (p=0.124), and insurance type (p=0.616) were not associated with postoperative infection. There was an 89.5% relative risk reduction with the use of intraoperative vancomycin. Increased body mass index (BMI) (p=0.029), increased operative time (p=0.001), and absence of ACL graft preparation with vancomycin (p=0.032) independently predicted postoperative infection.Conclusion:The use of vancomycin-soaked grafts was associated with a ten-fold reduction in postoperative infection after ACL reconstruction (0.1% versus 1.2%; p=0.032). Other risk factors for postoperative infection after ACL reconstruction included increased BMI and increased operative time.Table 1.Operative variables of the study groups. *=statistical significance(+) Vancomycinn=798 (48.7%)(-) Vancomycinn=842 (51.3%)p-valueOperative Time (minutes)98.6±42.3130.5±54.3*<0.001Autograft580 (72.7%)536 (63.5%)*<0.001Allograft210 (26.3%)237 (28.2%)0.436Hybrid Autograft/Allograft8 (1.0%)70 (8.30%)*<0.001Revision ACL128 (16.0%)133 (15.8%)0.901Multi-ligament90 (11.3%)61 (7.2%)*0.005Perioperative Cefazolin716 (89.7%)747 (88.6%)0.511Table 2.Demographic and operative variables of patients with and without infection. BMI=body mass index; IRR=incidence rate ratio; CI= confidence interval; *=statistical significance(+) Infectionn=11 (0.7%)(-) Infectionn=1627 (99.3%)IRR (95% CI)p-valueAge (years)30.0±14.027.7±11.3-0.571Male7 (63.6%)945 (58.0%)1.266 (0.371-4.342)0.707BMI (kg/m2)33.9±10.027.5±6.2-*0.029BMI>307 (63.6%)438 (26.9%)4.699 (1.376-16.050)*0.014Diabetes0 (0%)25 (1.5%)-1.000Smoking3 (27.4%)286 (17.6%)1.753 (0.465-6.608)0.407Private Insurance11 (100%)1466 (90.0%)-0.616Caucasian Race8 (72.7%)1337 (82.1%)2.076 (0.551-7.824)0.281Operative Time (minutes)125.6±48.5114.9±51.4-*0.001Tourniquet Use9 (81.8%)1378 (84.6%)1.334 (0.666-15.942)0.800Postoperative Aspirin10 (90.9%)1450 (89.0%)4.211 (0.836-9.474)0.841Vancomycin1 (9.1%)797 (48.9%)0.106 (0.014-0.824)*0.032Autograft4 (36.4%)1112 (68.3%)0.289 (0.079-0.919)*0.045Hamstring Autograft3 (27.3%)761 (46.7%)0.431 (0.114-1.623)0.213Quadriceps Autograft1 (9.1%)35 (2.2%)4.456 (0.570-34.806)0.154Hybrid Autograft/Allograft1 (9.1%)77 (0.6%)2.003 (0.256-15.644)0.508Table 3.Multivariate analysis results with incidence rate ratios (IRR) and 95% confidence intervals (CI). Multiple models were created to evaluate the effect of vancomycin ACL graft preparation on postoperative infection controlling for a single variable to prevent overfitting. Vancomycin use remained associated with decreased postoperative infection in each model. *=statistical significanceVariable Controlled ForIRR (95% CI)p-valueRevision0.117 (0.015-0.923)*0.042Other ligamentous procedure0.010 (0.013-0.782)*0.028BMI0.109 (0.014-0.856)*0.035Operative Time0.179 (0.021-0.450)*0.011Autograft0.119 (0.015-0.931)*0.042Hybrid0.107 (0.014-0.843)*0.034Table 4.Infection rates, total cases, and cases with vancomycin prepared grafts by treating surgeon.InfectionsTotal CasesVancomycin Cases (%)Infection RateSurgeon 131984 (2.0%)1.5%Surgeon 242432 (0.8%)1.7%Surgeon 31552435 (78.8%)0.2%Surgeon 401251 (0.8%)0%Surgeon 503029 (96.7%)0%Surgeon 63492327 (66.5%)0.6%