The 5-factor modified frailty index (mFI-5) predicts adverse outcomes after elective anterior cervical discectomy and fusion (ACDF).

BACKGROUND: Anterior cervical discectomy and fusion (ACDF) is a reliable procedure commonly performed in older patients with degenerative diseases of the cervical spine. Over 130,000 procedures are performed every year with an annual increase of 5%, and overall morbidity rates can reach as high as 19.3%, indicating a need for surgeons to gauge their patients' risk for adverse outcomes. Frailty is an age-associated decline in functioning of multiple organ systems and has been shown to predict adverse outcomes following various spine procedures. There have been several proposed frailty indices of various factors including the 11-factor modified frailty index (mFI-11), which has been shown to be an effective tool for predicting complications in patients undergoing ACDF. However, there is a paucity of literature assessing the utility of the 5-factor modified frailty index (mFI-5) as a risk stratification tool for patients undergoing ACDF. The purpose of this study was to analyze the predictive capability of the mFI-5 score for 30-day postoperative adverse events following elective ACDF.

METHODS: A retrospective review was performed using the National Surgical Quality Improvement Program (NSQIP) database from 2010 through 2019. Patients older than 50 years of age who underwent elective ACDF were identified using Current Procedural Terminology ([CPT] codes 22554, 22551, 22552, and 63075). Exclusion criteria removed patients under the age of 51, as well as those with fractures, sepsis, disseminated cancer, a prior operation in the last 30 days, ascites, wound infection, or an emergency surgery. Patients were grouped using mFI scores of 1, 2, and 3+. Univariate analysis, using chi-squared and one-way analysis of variance (ANOVA) tests, was conducted to compare demographics, comorbidities, and postoperative complications across the varying cohorts based on mFI-5 scores. Multivariate logistic regression, including patient demographics and preoperative comorbidities as covariates, was performed to evaluate if mFI-5 scores were independent predictors of 30-day postoperative adverse events. Covariates including race, BMI, sex, ASA, and comorbidities were included in regression models.

RESULTS: The 45,991 patients were identified and allocated in cohorts based on mFI-5 score. Rates for superficial surgical site infection (SSI), organ/deep space SSI, pneumonia, progressive renal insufficiency, acute renal failure (ARF), urinary tract infection (UTI), stroke/cardiovascular accident (CVA), cardiac arrest requiring cardiopulmonary resuscitation (CPR), myocardial infarction, bleeding requiring transfusions, deep vein thrombosis/thrombophlebitis, sepsis, septic shock, readmissions, reoperation, and mortality incrementally increased with mFI-5 scores from 0 to 3+. Multivariate regression analysis revealed that mFI-5 scores 1 to 3+ increased the odds, in a stepwise manner, of total complications, cardiac arrest requiring CPR, pneumonia and mortality. MFI-5 scores of 2 and 3+ were independent predictors of readmission (2: OR=1.5, p<.001; 3+: OR=2.0, p<.001) and myocardial infarction (2: OR=3.4, p=.001; 3+: OR=6.9, p<.001). A score of 3+ increased the odds of ARF (OR=9.7, p=.022), septic shock (OR=3.6, p=.036), UTI (OR=2.1, p=.007), bleeding requiring transfusions (OR=2.1, p=.016), and reoperations (OR=1.7, p=.004).

CONCLUSION: mFI-5 score is a quick and viable option for surgeons to use as an assessment tool to stratify high risk patients undergoing elective ACDF, as increasing mFI-5 scores showed significantly higher rates of all adverse outcomes accounted for in this study, except for deep incisional SSI, wound disruption, and PE. Additionally, moderate to severe mFI-5 scores of 2 or 3+ were independent predictors for 30-day postoperative ARF, UTI, MI, bleeding requiring transfusions, septic shock, reoperation, and readmissions following elective ACDF surgery in adults over 50 years old.