Do glycemic markers predict occurrence of complications after total knee arthroplasty in patients with diabetes?

BACKGROUND: Patients with diabetes have increased risk of infections and wound complications after total knee arthroplasty (TKA). Glycemic markers identifying patients at risk for complications after TKA have not yet been elucidated.

QUESTIONS/PURPOSES: We aimed to determine the correlations among four commonly used glycemic markers and to identify the glycemic markers most strongly associated with the occurrence of surgical site infections and postoperative wound complications in patients with diabetes mellitus after undergoing TKA.

METHODS: Our retrospective study included 462 patients with diabetes, who underwent a total of 714 TKAs. Blood levels of glycemic markers, including preoperative fasting blood glucose (FBG), postprandial glucose (PPG2), glycated hemoglobin (HbA1c), and levels obtained from random glucose testing on postoperative days 2, 5, and 14, were collected on all patients as part of a medical clearance program and an established clinical pathway for patients with diabetes at our center. Complete followup was available on 93% (462 of 495) of the patients. Correlations among markers were assessed. Associations between the markers and patient development of complications were analyzed using multivariate regression analyses of relevant cutoff values. We considered any of the following as complications potentially related to diabetes, and these were considered study endpoints: surgical site infection (superficial and deep) and wound complications (drainage, hemarthrosis, skin necrosis, and dehiscence). During the period of study, there were no fixed criteria applied to what levels of glycemic control patients with diabetes needed to achieve before undergoing arthroplasty, and there were wide ranges in the levels of all glycemic markers; for example, whereas the mean HbA1c level was 7%, the range was 5% to 11.3%.

RESULTS: There were positive correlations among the levels of the four glycemic markers; the strongest correlation was found between the preoperative HbA1c and PPG2 levels (R = 0.502, p < 0.001). After controlling for potential confounding variables using multivariate analysis, the HbA1c cutoff level of 8 (odds ratio [OR], 6.1; 95% confidence interval [CI], 1.6-23.4; p = 0.008) and FBG 200 mg/dL or higher (OR, 9.2; 95% CI, 2.2-38.2; p = 0.038) were associated with superficial surgical site infection after TKA.

CONCLUSIONS: In general, there is a positive correlation among the various available glycemic markers among patients with diabetes undergoing TKA, and patients undergoing surgery with HbA1c ≥ 8 and/or FBG ≥ 200 mg/dL were associated with superficial surgical site infection. These findings should be considered in patient selection and preoperative counseling for patients with diabetes undergoing TKA.

LEVEL OF EVIDENCE: Level III, prognostic study.