Short-term Outcomes of Unrestricted Kinematic Alignment: Total Knee Arthroplasty With a Medial Pivot Implant: A...

This study investigated the short-term postoperative radiological and clinical results of unrestricted kinematic alignment (unKA)-total knee arthroplasty (TKA) using medial pivot (MP) knee prosthesis in a Japanese population.

This multicenter prospective study included 1950 knees (from 384 males and 1566 females; mean age 74.7 years) with complete radiographs, range of motion (ROM) measurements, and minimum 1-year follow-up from a cohort of 2388 knees (462 males and 1926 females; mean age 74.3 years) that underwent unKA-MP-TKA. We classified all patients into the R group (n = 876) within safe ranges (177°≤ hip-knee-ankle angle ≤183°; 85°≤ medial proximal tibial angle ≤95°; 85°≤ lateral distal femoral angle ≤95°) and O group (n = 1074) outside those ranges. Postoperative radiographic and clinical outcomes were compared.

The coronal plane alignment of the knee classification changed in 1053 knees (53.1%) preoperatively and postoperatively. Type I to type II was most common (350 knees; 33.8%). ROM significantly improved from -9.2 ± 7.7° and 120.6 ± 16.2° preoperatively to -1.2 ± 3.1° and 122.5 ± 11.8° at the 1-year follow-up. Three knees required reoperation because of patellofemoral joint problems within 1-year postoperatively. ROM outcomes were similar in both groups. Revision surgery owing to tibiofemoral joint complications was not required.

UnKA-MP-TKA resulted in the femoral component being placed in valgus, the tibial component in varus, and lower-limb alignment in varus. No revision surgery owing to tibiofemoral joint complications was needed. The short-term postoperative outcomes of unKA-MP-TKA in the Japanese population, who exhibit a high prevalence of varus knee alignment, were favorable whether within or outside the safe ranges. However, the follow-up period was only 1-year, and continued long-term observation is crucial and necessary.

IV.