Modified Frailty Index Is an Effective Risk Assessment Tool in Primary Total Knee Arthroplasty

"Frailty" is a marker of physiological decline of multiple organ systems, and the frailty index identifies patients who are more susceptible to postoperative complications. The purpose of this study is to validate the modified frailty index (MFI) as a predictor of postoperative complications, reoperations, and readmissions in patients who underwent primary total knee arthroplasty (TKA).

The American College of Surgeons National Surgical Quality Improvement Program database from 2005 to 2014 was queried by the Current Procedural Terminology code for primary TKA (27447). A previously described MFI was used to summate 11 variables in 5 organ systems. Bivariate analysis was performed for postoperative complications. A multiple logistic regression model was used to determine the relationship between MFI, American Society of Anesthesiologists score, and 30-day reoperation, controlling for age, gender, and body mass index.

A total of 90,260 patients underwent primary TKA during the study period. As MFI score increased, 30-day mortality significantly increased (P < .001). In addition, significantly higher rates of postoperative complications (all P < .001) were observed with increasing MFI: infection, wound, cardiac, pulmonary, and renal complications; and any occurrence. More frail patients also had increasing odds of adverse hospital discharge disposition, reoperation, and readmission (all P < .001). Length of hospital stay increased from 3.10 to 5.16 days (P < .001), while length of intensive care unit stay increased from 3.47 to 5.07 days (P < .001) between MFI score 0 and ≥0.36. MFI predicts 30-day reoperation with an adjusted odds ratio of 3.32 (95% confidence interval, 1.36-8.11; P < .001). Comparatively, MFI was a stronger predictor of reoperation compared with American Society of Anesthesiologists score and age with adjustment for gender and body mass index.

Utilization of the MFI is a valid method in predicting postoperative complications, reoperations, and readmissions in patients undergoing primary TKA and can provide an effective and robust risk assessment tool to appropriately counsel patients and aid in preoperative optimization.