Cementless Total Knee Arthroplasty Using an Ultraconforming Tibial Bearing: Outcomes at Minimum 5-Year Follow-Up

Cementless fixation for primary total knee arthroplasty (TKA) continues to increase in the United States. However, compared to cemented TKA, reports on revision rates have been mixed. A confounding variable may include the tibial insert design. This study aimed to assess the minimum 5-year survivorship and outcomes of a cementless TKA using an ultracongruent (UC) articulation.

A consecutive series of 242 cementless TKAs were implanted at two institutions between 2017 and 2019 using an UC kinematic tibial insert. Of the patients, 56% were men. The average age was 60 years. Patients were followed using Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) and Knee Society clinical and radiographic scores. Preoperative and postoperative radiographs were classified according to the Coronal Plane Alignment of the Knee (CPAK) type. The average follow-up was 5.6 years (range, five to 7.5).

At the final follow-up, KOOS-JR scores averaged 84.0. Knee Society scores averaged 94. Flexion averaged 116°. There were seven manipulations (2.9%), one patella fracture, and no deep infections. There were seven knees (2.9%) revised (three for flexion instability, one for pain, one for femoral fibrous ingrowth, one for distal femur fracture, and one for arthrofibrosis). At 5 years, survivorship free from aseptic loosening was 99.6%. Change in CPAK type did not correlate with final KOOS-JR, pain, University of California Los Angeles activity score, or satisfaction scores.

Cementless TKA using this conforming design has provided excellent clinical results out to 5 years. Once initial component stability is achieved, the UC nature of this articulation does not appear to adversely influence the durability of implant fixation, regardless of whether the CPAK type was changed.