Previous knee injury requiring surgical intervention increases the rate of future arthroplasty. Coding modifiers for removal of previous hardware or increased complexity offer inconsistent results. A Current Procedural Terminology code for knee conversion does not currently exist as it does for conversion hip arthroplasty. We investigate the extra time associated with conversion knee arthroplasty.
Sixty-three total knee arthroplasty (TKA) cases in the setting of previous knee hardware were identified from our institution between 2008 and 2015. Knee conversions were matched to primary TKA by age, gender, body mass index, Charlson Comorbidity Index, and surgeon, in a 3:1 ratio. Patients who underwent knee conversions were compared to matched TKA with regard to operative time, length of stay, discharge destination, readmission, and repeat procedures within 90 days from index procedure.
The mean operating room time for primary TKA was 71.7 minutes (range 36-138). The mean operating room time for knee conversion was significantly greater by an additional 31 minutes; mean 102.1 minutes (range 56-256 minutes, P < .0001). Rates of readmission, 0.5% vs 3.2%, and repeat procedures, 5.3% vs 12.7%, within 90 days were greater for knee conversions. There was no difference in length of stay or discharge destination.
Total knee conversion results in a 43% increase in operative time and more than twice the rate of readmission and repeat procedures within 90 days compared to TKA. This suggests the need for an additional Current Procedural Terminology code for knee conversion arthroplasty to compensate surgeons for the extra time required for conversions.