Is Conversion Total Knee Arthroplasty a Distinct Surgical Procedure? A Comparison to Primary and Revision Total Knee Arthroplasty.

Conversion total knee arthroplasty (TKA) is suggested to incur similar complication rates to revision arthroplasties. However, current billing codes do not allow for the differentiation between this operation and primary TKAs. Therefore, the purpose of this study was to compare outcomes of these two surgeries, as well as revision TKAs. Specifically, we analyzed (1) medical complications, (2) surgical complications, and (3) revision rates at 90 days and 1 year. We queried a national, all-payer database to identify patients who underwent TKA without prior implants ( = 1,358,767), required conversion TKA ( = 15,378), and who underwent revision TKA ( = 33,966) between January 1, 2010, and April 30, 2020. Conversion TKA patients (prior implant removal) were identified using the Current Procedural Terminology (CPT) codes. Outcomes studied included 30-day readmission rates and 90-day, as well as 1-year, medical and surgical complications. Conversion TKAs had greater 30-day readmission rates and incidences of most of the complications studied when compared with primary TKAs. The majority of outcomes when comparing between primary, conversion, and revision TKAs were significantly different ( < 0.01). In contrast, conversion TKA complications were similar to revision TKA. Conversion TKAs have higher postoperative complications than primary TKAs and share more similarities with revision TKAs. Thus, the lack of billing codes differentiating conversion and primary TKAs creates a challenge for orthopaedic surgeons.