Clin Orthop Surg.  2024 Aug;16(4):570-577. 10.4055/cios23356.

Load-Dependent Characteristics of Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty: A Biomechanical Study

Affiliations
  • 1Southern California Permanente Medical Group, Department of Orthopaedics, Fontana Medical Center, Los Angeles, CA, USA
  • 2New York University Langone Orthopedic Hospital, New York, NY, USA
  • 3Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA
  • 4Department of Internal Medicine, Highland Hospital, Oakland, CA, USA

Abstract

Background
Increased load bearing across the patellofemoral and tibiofemoral articulations has been associated with total knee arthroplasty (TKA) complications. Therefore, the purpose of this study was to quantify the biomechanical characteristics of the patellofemoral and tibiofemoral joints and simulate varying weight-bearing demands after posterior cruciate ligament-retaining (CR) and posterior-stabilized (PS) TKAs.
Methods
Eight fresh-frozen cadaveric knees (average age, 68.4 years; range, 40–86 years) were tested using a custom knee system with muscle-loading capabilities. The TKA knees were tested with a CR and then a PS TKA implant and were loaded at 6 different flexion angles from 15° to 90° with progressively increasing loads. The independent variables were the implant types (CR and PS TKA), progressively increased loading, and knee flexion angle (KFA). The dependent variables were the patellofemoral and tibiofemoral kinematics and contact characteristics.
Results
The results showed that at higher KFAs, the position of the femur translated significantly more posterior in CR implants than in PS implants (36.6 ± 5.2 mm and 32.5 ± 5.7 mm, respectively). The patellofemoral contact force and contact area were significantly greater in PS than in CR implants at higher KFAs and loads (102.4 ± 12.5 N and 88.1 ± 10.9 N, respectively). Lastly, the tibiofemoral contact force was significantly greater in the CR than the PS implant at flexion angles of 45°, 60°, 75°, and 90° KFA, the average at these flexion angles for all loads tested being 246.1 ± 42.1 N and 192.8 ± 54.8 N for CR and PS implants, respectively.
Conclusions
In this biomechanical study, CR TKAs showed less patellofemoral contact force, but more tibiofemoral contact force than PS TKAs. For higher loads across the joint and at increased flexion angles, there was significantly more posterior femur translation in the CR design with a preserved posterior cruciate ligament and therefore significantly less patellofemoral contact area and force than in the PS design. The different effects of loading on implants are an important consideration for physicians as patients with higher load demands should consider the significantly greater patellofemoral contact force and area of the PS over the CR design.

Keyword

Total knee arthroplasty; Cruciate retaining; Posterior stabilized; Contact area; Contact force
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