Sequence of 305,996 total hip and knee arthroplasties in patients undergoing operations on more than 1 joint

Background and purpose - Patient-specific data on multiple total arthroplasties (TA) of the lower limbs due to osteoarthritis (OA) are limited. We investigated the sequence of surgical procedures and risk factors for additional surgery in such patients. Patients and methods - 305,996 patients operated with a TA of the hip and/or knee due to OA were extracted from the Swedish National Hip (SHAR) and the Swedish Knee Arthroplasty Register (SKAR). 177,834 total hip arthroplasty (THA, 56% women, mean age 69 years) and 128,162 total knee arthroplasty (TKA, 60% women, mean age 69 years) procedures constituted the index operations. The mean, median, and maximum follow-up was 8, 6, and 23 years. Multivariable Cox regression analysis was used and Kaplan-Meier survival curves were constructed. Results - Right-sided primary TA (34%) was most frequent. Subsequent surgery was most frequent after primary left-sided TKA (33%). The time interval to a second TA procedure was 3.1 (SD 3.2) years after TKA and 4.0 (SD 3.9) years after THA. After the index TA the probability of no subsequent surgery amounted to 64% (SD 0.3) for THA and 58% (SD 0.4) for TKA over 20 years. Lower age, female sex, left side, and TKA at index operation were associated with a higher probability for subsequent TA. Interpretation - Delineation of factors that influence risk and the size of the risk for subsequent TA in 1 of the 3 major remaining joints is of value for clinicians and healthcare providers in the decision-making process for future resource allocation.