Association of Obesity With Hospital Readmission After Inpatient Rehabilitation for Primary Total Hip Arthroplasty

PURPOSE: Given the increase in life expectancy, the current epidemic of obesity, the expected increase in arthritis, and the increase in joint replacement procedures in the United States, it is necessary to study whether obesity status affects the outcome of hospital readmission after inpatient rehabilitation for elective hip replacement. Obesity is known to be associated with increased hospital length of stay and the risk of being discharged to long–term care after total hip arthroplasty (THA; Ledford et al., 2014). Obesity is also known to increase operative time for surgical procedures, which greatly influences development of surgical site complications and systemic complications (Bradley et al., 2014). Obesity is also associated with long–term complications after THA such as deep vein thrombosis and pulmonary embolism (Wallace et al., 2014). This study examined the association of obesity with risk of 30–day postrehabilitation all–cause hospital readmission and with either systemic or local/procedure‐related reasons for these readmissions after elective THA.

DESIGN: This retrospective study involved secondary analyses of Medicare claims data. The data sources were the Medicare Provider Analysis and Review file and the Inpatient Rehabilitation Facility (IRF) Patient Assessment Instrument. The inclusion criteria were Medicare beneficiaries who were aged 65 or older, who underwent elective THA for a primary diagnosis of osteoarthritis, who were living in the community prior to the THA, and who had a minimum of 3 days of IRF stay immediately after the THA.

The independent variable, obesity status, was defined using the International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes recorded during either the hospital or the IRF stay. Obesity status was categorized as normal weight, overweight and obesity, or morbid obesity. The covariates included age, gender, race/ethnicity, social support, disability status, Medicare–Medicaid dual eligibility, and comorbid conditions.

The outcome variable, 30‐day hospital readmission, was recorded as all hospital readmissions occurring within 30 days from the day of discharge from the IRF to the community, excluding direct transfers from the IRF back to the hospital. Among those readmitted, reasons for readmission were identified and classified using Medical Severity–Diagnosis Related Groups codes as local/procedure‐related, systemic, or unrelated.

Multivariable logistic regression was used for the binary variable of 30‐day all‐cause hospital readmission. Multinomial logistic regression was used for the three‐level outcome of reason for readmission.

RESULTS: Morbid obesity was significantly associated with greater risk for 30‐day hospital readmission. Morbid obesity was also significantly associated with greater odds for local/procedure–related reason for readmission.

CONCLUSION: This unique study contributes valuable scientific information regarding differences, based on obesity status, in 30‐day hospital readmissions and in the reasons for readmissions after an IRF stay for elective primary THA. This study provides new insights on the effect of obesity status on the adverse outcome of hospital readmission. This is the first study to evaluate the association of obesity with reasons for readmission among Medicare beneficiaries who underwent THA. By using big data, this study makes a significant contribution with respect to sound findings. This is also a timely study identifying potential gaps in care that may be contributing to adverse outcomes that increase burden of care and health care costs, given the Comprehensive Care for Joint Replacement model, effective April 2016, for reducing health care costs and improving quality of care and health outcomes in this population (Centers for Medicare & Medicaid Services, 2017).

References

Bradley, B. M., Griffiths, S. N., Stewart, K. J., Higgins, G. A., Hockings, M., & Isaac, D. L. (2014). The effect of obesity and increasing age on operative time and length of stay in primary hip and knee arthroplasty. Journal of Arthroplasty, 29, 1906–1910. https://doi.org/10.1016/j.arth.2014.06.002

Ledford, Centers for Medicare & Medicaid Services. (2017). Bundled Payments for Care Improvement (BPCI) Initiative: General information [updated November 20, 2017]. Retrieved from https://innovation.cms.gov/initiatives/bundled-payments/ C. K., Ruberte Thiele, R., Appleton, J. S., Jr., Butler, R. J., Wellman, S. S., Attarian, D. E., . . . Bolognesi, M. P. (2014). Percent body fat more associated with perioperative risks after total joint arthroplasty than body mass index. Journal of Arthroplasty, 29(Suppl. 2), 150–154. https://doi.org/10.1016/j.arth.2013.12.036

Wallace, G., Judge, A., Prieto‐Alhambra, D., de Vries, F., Arden, N. K., & Cooper, C. (2014). The effect of body mass index on the risk of post‐operative complications during the 6 months following total hip replacement or total knee replacement surgery. Osteoarthritis and Cartilage, 22, 918–927. https://doi.org/10.1016/j.joca.2014.04.013