Use of large databases for orthopaedic research has increased exponentially. Each database represents unique patient populations and vary in methodology of data acquisition. The purpose of this study was to evaluate differences in reported demographics, comorbidities and complications following total hip arthroplasty (THA) amongst four commonly used databases.

Patients who underwent primary THA during 2010–2012 were identified within National Surgical Quality Improvement Programs (NSQIP), Nationwide Inpatient Sample (NIS), Medicare Standard Analytic Files (MED) and Humana Claims Database (HAC). NSQIP definitions for comorbidities and surgical complications were queried in NIS, MED, and HAC using coding algorithms. Age, sex, comorbidities, inpatient and 30-day postoperative complications were compared (NIS has inpatient data only).

Primary THAs from each database were 22,644 (HAC), 371,715 (MED), 188,779 (NIS) and 27,818 (NSQIP). Age and gender distribution were similar between databases. There was variability in the prevalence of comorbidities and complications depending upon the database and duration of post-operative follow-up. HAC and MED had twice the prevalence of COPD, coagulopathy and diabetes than NSQIP. NSQIP had more than twice the obesity than NIS. HAC had more than twice the rates of 30-day complications at all endpoints compared to NSQIP and more than twice the DVTs, strokes and deep infection as MED at 30-days post-op. Comparison of inpatient and 30-day complications rates demonstrated more than twice the amount of infections and DVTs are captured when analysis is extended from inpatient stay to 30-days post-op.

Amongst databases commonly used in orthopaedic research, there is considerable variation in complication rates following THA depending upon the database. It will be important to consider these differences when critically evaluating database research. Additionally, with the advent of bundled payments, these differences must be considered in risk adjustment models.