Comparing Costs and Complications Associated with Primary versus Conversion THA

    In a study accepted for publication, conversion total hip arthroplasty (THA) was found to be associated with increased costs and more perioperative complications than primary THA. These findings suggest that the MS-DRG for THA should be reclassified to prevent the expense disparity from becoming a barrier to patient care.


    Jessica M. Hooper, MD, and Ajit J. Deshmukh, MD


    Ryan SP, DiLallo M, Attarian D, Jiranek W, Seyler T. Conversion vs. Primary Total Hip Arthroplasty: Increased Cost of Care and Perioperative Complications. J Arthroplasty 2018. [Epub ahead of print] doi: 10.1016/j.arth.2018.03.006.


    Several studies have reported an increased rate of perioperative complications associated with conversion total hip arthroplasty (THA) compared with primary THA. However, the current literature lacks robust data on cost differences associated with conversion versus primary THA. In the current healthcare economic climate, close attention must be paid to patient outcomes, complications, and costs of care to justify reimbursement and maintain access to care for more complicated patients.

    In this retrospective case control study, 163 patients who underwent THA after prior hip surgery (conversion THA group) were matched for age, BMI, and ASA score to 163 patients who underwent primary THA alone (comparison group). The conversion THA group was sub-stratified based on whether or not hardware was placed at the time of the index procedure.

    The authors analyzed the following data points using Chi-square, Fisher’s exact test, or Student’s T test:

    • Outcome variables
      • Operative time
      • Estimated blood loss (EBL)
      • Intraoperative or postoperative complications
      • Length of stay
      • Discharge disposition
      • Need for revision surgery
    • Cost variables
      • Direct labor costs
      • Other direct costs (supplies, drugs, and equipment expenses) 

      • Intermediate nursing services
      • Pharmacy
      • Other diagnostic/therapy services
      • Surgery services
      • Respiratory care
      • Physical/occupational/speech therapy
      • Radiology
      • Laboratory
      • Blood
      • Medical/surgical supply
      • Total direct costs

    Three comparisons were made for patient outcomes:

    • Conversion THA versus primary THA
    • Hardware conversion THA versus primary THA
    • Non-hardware conversion THA versus primary THA

    Primary THA was compared with conversion THA for cost variables, and subgroup analysis was performed comparing hardware versus non-hardware conversion THA. Additional cost analysis was performed comparing the 3 most-common index procedures in the conversion THA group: open reduction internal fixation of the hip, hip arthroscopy, and free vascularized fibula graft for osteonecrosis.

    Compared with primary THA, conversion THA had a significantly greater cost – approximately 19% greater – due to higher costs for all cost variables listed above except pharmacy and respiratory care. The conversion THA group also had significantly greater operative times, estimated blood loss, length of stay, intraoperative complications, and postoperative complications.

    When considered separately, conversion THA with and without hardware were both associated with increased operative time, EBL, greater length of stay, and surgical site infection. The hardware conversion THA patients also had an increased rate of intraoperative complications, transfusion rates, dislocations, rates of revision, and discharge to a skilled nursing facility.

    Clinical Relevance

    Medicare is currently the primary payer for THA in the United States. The Centers for Medicare and Medicaid Services (CMS) has defined Medicare Severity-Diagnosis Related Groups (MS-DRGs) to guide hospital reimbursement for hospital acute care inpatient services, including THA. The DRGs for THA have evolved to recognize revision THA as distinctly different from primary THA and to account for medically complex patients requiring more involved care.

    At the same time, the number of hip preservation procedures performed annually is rapidly increasing, and the indications for THA are expanding, which is precipitating exponential growth in the incidence of conversion THA surgeries.

    The results of this study demonstrate clear differences between conversion THA and primary THA. Conversion THA is not equivalent to primary THA, with respect to clinical outcomes, associated costs, or resource utilization. The conclusion that CMS should update the MS-DRG classification to recognize conversion THA as a unique entity is valid and would likely prevent barriers to patient care. If reimbursement is the same for primary and conversion THA, community orthopaedic surgeons may be forced to preferentially refer out conversion THA patients due to consideration for the resources required to care for these patients, which will disproportionately burden tertiary referral centers.

    There are few limitations to this study, namely that it is a single institution study with a relatively small sample size and that post-acute care costs were unavailable for analysis. However, none of these limitations take away from the study’s conclusion.

    A multi-center study would be ideal to validate this study’s conclusions and strengthen the argument for reclassification of the MS-DRGs for THA.

    Author Information

    Jessica M. Hooper, MD is an orthopaedic surgery resident at NYU Langone Orthopaedic Hospital, New York, New York. Ajit J. Deshmukh, MD is an Assistant Professor of Orthopaedic Surgery, Division of Adult Reconstruction, Department of Orthopaedic Surgery, at NYU Langone Orthopaedic Hospital, New York, New York. He is also an orthopaedic surgeon at the VA New York Harbor Healthcare System, New York, New York.


    The authors have no disclosures relevant to this article.