Abstract
Introduction:
Solid organ transplant patients are living longer than in past decades, largely due to improvements in surgical technique, immunosuppressive regimens, patient selection, and postoperative care. As these patients grow older, many of them present for total hip arthroplasty (THA). However, life-long immunosuppressive therapy, metabolic disorders, and post-transplant medications may place transplant patients at higher risk for complications following THA. The objective of this study was to use a national administrative database to compare morbidity, acute complications, in-hospital mortality, length of stay (LOS), and admission costs for THA patients with and without solid organ transplant history.
Methods:
The Nationwide Inpatient Sample (NIS), the largest all-payer inpatient care database representing a 20% stratified sample of United States hospitals, was retrospectively queried for primary THA (ICD-9-CM 81.51) patients from 1998 to 2009 (n = 2,567,930; weighted national frequency). Cases were excluded (n = 324,837) for the following: age <18 years, pathologic fracture of lower extremity, malignant neoplasm and/or metastatic cancer, primary diagnosis of femoral neck fracture, admission type other than “elective,” previous and/or bilateral arthroplasty. The remaining 2,243,093 THA patients were assigned to transplant (n = 6,319; liver, kidney, heart, lung and/or pancreas transplant history) or non-transplant groups (n = 2,231,446; no history of any transplant including solid organ or tissue). Acute complications included a variety of organ-specific and procedure-related complications (i.e. mechanical implant failure, dislocation, hematoma, infection, pulmonary embolism, venous thrombosis). Multivariable regression and general estimating equations were developed to study the effect of transplant history on outcomes, adjusting for patient/hospital characteristics and comorbidity.
Results:
Between 1998 and 2009, the volume of THA among patients with a history of solid organ transplant grew approximately 40% (444 to 620 cases/year), which was lower than that among non-transplant patients (+102%). Transplant THA patients were significantly sicker than their non-transplant peers, with an elevated Elixhauser comorbidity index (7.69 vs. 1.21; p < 0.001). Transplant and non-transplant patients had similar rates of 1+ inpatient complication(s) following THA (transplant 23.6% vs. non-transplant 24.3%; p = 0.60). There were no in-hospital deaths in the transplant group, while 0.1% (n = 2,855) of non-transplant patients died after THA. Unadjusted trends show that transplant patients have a longer mean LOS (4.5 days) than non-transplant patients (3.9 days; p < 0.001) after THA, although LOS decreased for both groups over time (Figure 1). Also, overall unadjusted mean costs per THA admission were significantly higher for the transplant cohort ($15,518) than the non-transplant group ($14,474; p < 0.001), and both increased over time (Figure 2). After adjusting for confounders, transplant patients had an 8% increase in LOS (0.38 days) compared to non-transplant patients (p < 0.001); however, there were no statistically significant increases in admission costs (p = 0.13) or complications (p = 0.19).
Conclusions:
While the annual volume of THA performed in the United States on patients with a history of solid organ transplant is increasing, the rate is less than half that of non-transplant patients undergoing THA. Transplant patients have a significantly higher number of comorbidities and longer LOS after THA compared to non-transplant patients. Admission costs and acute complications are comparable among these populations, after adjusting for patient and hospital characteristics.
