MetS-OA Linked to More RTKA Complications and Charges
Key Takeaways
- Among more than 1.3 million U.S. revision total knee arthroplasty hospitalizations, 16.1% met the study definition of metabolic syndrome-associated osteoarthritis (MetS-OA), and that share increased over the study period.
- The MetS-OA group had a heavier baseline illness burden, with 28.9% having at least two comorbid conditions versus 22% in the comparison group.
- Several adjusted in-hospital complications were more common with MetS-OA, with the strongest relative increases seen for prolonged mechanical ventilation and acute renal failure.
- Hospitalization charges were higher for MetS-OA RTKA admissions, while in-hospital mortality did not differ significantly.
The final analytic cohort comprised 1,330,099 RTKA hospitalizations, including 214,448 admissions with metabolic syndrome-associated osteoarthritis (MetS-OA) and 1,115,651 without MetS-OA. The authors defined MetS-OA as osteoarthritis with obesity and at least two of hypertension, diabetes mellitus, and hyperlipidemia, and analyses used NIS discharge weights with multivariable logistic regression.
Over the study period, the MetS-OA phenotype became more common among RTKA admissions and was associated with an older, more often male, less often White, and more often urban- and teaching-hospital inpatient profile. These admissions also carried a heavier baseline comorbidity burden, including more chronic pulmonary disease, depression, hypothyroidism, and renal disease.
Resource use was higher among MetS-OA admissions, with median total hospitalization charges of $50,649.50 versus $49,204.00, a difference of $1,445.50. In adjusted analyses, prolonged mechanical ventilation was more likely with MetS-OA at OR 2.09 (95% CI 1.96-2.22), and acute renal failure was also more likely at OR 1.69 (95% CI 1.65-1.74). Higher adjusted odds were also reported for acute myocardial infarction, severe malnutrition, acute cerebrovascular disease, postoperative delirium, acute respiratory distress syndrome (ARDS), urinary tract infection, and lower extremity nerve injury. In-hospital mortality did not differ significantly, and pneumonia was not significant after adjustment.
Because this was a retrospective administrative-database study, the findings support association rather than causation, and complication capture ended at hospital discharge. Body mass index, operative duration, and post-anesthesia sedation depth were unavailable, and coding or reporting bias may have affected case identification.
Clinician Questions
How was metabolic syndrome-associated osteoarthritis defined in revision total knee arthroplasty hospitalizations?
In this U.S. RTKA hospitalization analysis, metabolic syndrome-associated osteoarthritis was defined operationally as osteoarthritis plus obesity and at least two of hypertension, diabetes mellitus, and hyperlipidemia. This was a coding-based inpatient phenotype used to build comparison groups in the database rather than a directly adjudicated clinical phenotype.
Does this analysis apply to primary total knee arthroplasty or only to revision total knee arthroplasty?
This cohort included adults undergoing revision total knee arthroplasty hospitalizations in the Nationwide Inpatient Sample, so the findings speak directly to RTKA admissions. The dataset did not study primary knee arthroplasty as the target population, so the reported associations do not directly extend to primary procedures.
What postoperative time window was captured for complications in the MetS-OA RTKA analysis?
The reported complications were limited to the index inpatient hospitalization through discharge in U.S. RTKA admissions. Post-discharge events were not systematically captured, so this was not a long-term follow-up cohort and the complication pattern reflects the inpatient stay.