Institutional Adherence to the American Association of Hip and Knee Surgeons Body Mass Index Guidelines Lowers Perioperative Emergency Department Visits in Primary Total Knee Arthroplasty

Abstract

Background: In 2013, the American Association of Hip and Knee Surgeons tasked a workgroup to provide obesity-related recommendations in total joint arthroplasty and determined that patients who had body mass index (BMI) ≥ 40 seeking hip/knee arthroplasty were at increased perioperative risk and recommended preoperative weight reduction. Few studies have shown the actual results of instituting this; therefore, we reported the effect of instituting a BMI < 40 threshold in 2014 on our elective, primary total knee arthroplasties (TKAs).

Methods: We queried an institutional database to select all TKAs conducted from January 2010 to May 2020. There were 2,514 TKA pre-2014 and 5,545 TKA post-2014 that were identified. The 90-day emergency department (ED) visits, readmissions, and returns-to-operating room (OR) outcomes were identified. Patients were propensity score weight-matched as per comorbidities, age, initial surgical consultation (consult) BMI, and sex. We conducted 3 outcome comparisons: (1) pre-2014 patients who had a consult and surgical BMI ≥ 40 against post-2014 patients who had a consult BMI ≥ 40 and surgical BMI < 40; (2) pre-2014 patients against post-2014 patients who had a consult and surgical BMI < 40; (3) post-2014 patients who had a consult BMI ≥ 40 and surgical BMI < 40 against post-2014 patients who had a consult BMI ≥ 40 and surgical BMI ≥ 40.

Results: Pre-2014 patients who had a consult and surgical BMI ≥ 40 had more ED visits (12.5% versus 6%, P = .002) but similar readmissions and returns-to-OR than post-2014 patients who had a consult BMI ≥ 40 and surgical BMI < 40. Pre-2014 patients who had a consult and surgical BMI < 40 had more readmissions (8.8% versus 6%, P < .0001) but similar ED visits and returns-to-OR when compared to their post-2014 counterparts. Post-2014 patients who had a consult BMI ≥ 40 and surgical BMI < 40 had fewer ED visits (5.8% versus 10.6%) but similar readmissions and returns-to-OR than patients who had a consult BMI ≥ 40 and surgical BMI ≥ 40.

Discussion: Patient optimization prior to total joint arthroplasty is essential. Enacting BMI reduction pathways prior to total knee arthroplasty seems to afford morbidly obese patients major risk mitigation. We must continue to ethically balance the pathology, expected improvement after surgery, and the overall risks of complications for each patient.

Level of evidence: III.

Keywords: AAHKS; BMI; body mass index; obesity; threshold; total knee arthroplasty.