Is There Synergistic Effect Between Obesity and Hypoalbuminemia on Postoperative Outcomes Among Primary Total Shoulder Arthroplasty Recipients?

BACKGROUND: Malnutrition and obesity are established predictors of complications following joint replacement surgery. However, the effect of obesity in the setting of albumin deficiency has not been explored in non-weight-bearing upper-extremity joint arthroplasty.

PURPOSE: We sought to determine whether there is a synergistic effect between obesity and hypoalbuminemia among patients undergoing primary total shoulder arthroplasty (TSA) with respect to postoperative outcomes, including (1) mortality rates, (2) composite surgical complications, (3) length of hospitalization, and (4) hospital readmission.

METHODS: We conducted a retrospective cohort study using the National Surgical Quality Improvement Program (NSQIP) database to find patients who underwent primary TSA from January 1, 2006, to December 31, 2019. We grouped these patients as obese (body mass index [BMI] ≥ 30 kg/m2 ) or nonobese (BMI = 18.5-29.9 kg/m2 ) and by serum albumin level (hypoalbuminemia < 3.5 mg/dL or normoalbuminemia ≥ 3.5 mg/dL). We gathered data on readmission and mortality rates, and NSQIP complications were organized into 3 composite variables: wound infection, systemic infection, and cardiac/pulmonary complication. For each outcome, multivariate logistic regression analysis evaluated its association with obesity and hypoalbuminemia, as well as with the interaction of BMI and albumin, while adjusting for covariates.

RESULTS: Of 12,881 patients, 51.8% were obese and 7.0% had hypoalbuminemia; 7.6% of obese patients had hypoalbuminemia versus 6.3% of those who were not obese. Patients with hypoalbuminemia had the longest hospital stays and the highest rates of mortality and systemic infection of all subgroups. Multivariate logistic regression analysis did not show higher complication rates due to obesity or evidence of additive interaction between hypoalbuminemia and obesity.

CONCLUSION: Unlike previous reports in weight-bearing arthroplasty, in this retrospective study of a cohort of patients who underwent TSA, we did not observe greater complications due to obesity alone, nor did we find evidence of additive interaction between obesity and hypoalbuminemia. This distinction may be due to the non-weight-bearing nature of TSA, in which excessive BMI may be less relevant for postoperative healing.