For knee arthroplasty, there is consistent evidence that surgical procedures in morbidly obese patients; associated with numerous concerns, including longer length of stay; higher odds of being discharged to a facility, longer operative time; and having lower absolute physical function improvement; in addition to 30-day mortality and surgical site infection. Several institutions have implemented formal or informal cutoff thresholds for performing total knee arthroplasty in patients with high BMI; usually at the morbid obesity level.
We sought to determine whether different levels of preoperative weight loss; among morbidly obese patients undergoing total knee arthroplasty, were associated with postoperative length of stay, discharge to a facility; operative time, and physical function improvement (Patient-Reported Outcomes Measurement Information System [PROMIS]-10 physical component score [PCS]).
Morbidly obese patients
They retrospectively reviewed our institutional data repository from an U.S. tertiary academic medical center; with data prospectively collected from April 2011 to July 2016. Of 2,308 applicable total knee arthroplasties among 2,157 patients; patients undergoing 1,541 surgical procedures (66.8%) had clinical measurements of BMI (height and weight) at least 90 days before the surgical procedure. Of those 1,541 surgical procedures, 208 (13.5%) occurred among 206 patients who were morbidly obese; with a clinically measured BMI of ≥40 kg/m2.
Among the 208 surgical procedures, 203 patients undergoing 203 surgical procedures (97.6%); had BMI clinically measured again at the preoperative visit before the total knee arthroplasty and included; allowing us to determine the extent of weight loss among morbidly obese patients before the total knee arthroplasty occurred. There were 203 morbidly obese patients who had height and weight clinically measured; at least 90 days before the surgical procedure and repeated these measurements at the preoperative visit.
Among those 203 patients, 83 (41%) lost at least 5 pounds, 59 (29%) lost at least 10 pounds; and 29 (14%) lost at least 20 pounds. The mean age (and standard deviation) was 59.6 ± 8.5 years, and 146 patients (71.9%) were female. Forty-five % of patients had no comorbidities, 28% of patients had 1 comorbidity; and 27% of patients had at least 2 comorbidities. Specifically, 31% of patients had diabetes and 21% had chronic obstructive pulmonary disease.
Total knee arthroplasty
In unadjusted analyses, there was no difference in the ability of patients with diabetes; to lose weight at each threshold compared with other morbidly obese patients without diabetes (results not shown). The mean baseline BMI was 45.8 ± 5.4 kg/m2, the preoperative BMI was 44.9 ± 5.9 kg/m2, and the 1-year postoperative BMI was 45.0 ± 5.6 kg/m2.
They investigated whether preoperative weight loss among morbidly obese patients undergoing total knee arthroplasty; had any association with improved outcomes. Although 5-pound and 10-pound weight loss did not impact any outcomes; losing at least 20 pounds associated with a significantly shorter length of stay and lower odds of extended length of stay and facility discharge; even though the mean BMIs after weight loss remained in the morbidly obese category and patients largely returned to their baseline BMI postoperatively.