Related Experiment Video
Updated: Jan 18, 2026
Three-Dimensional Preoperative Virtual Planning in Derotational Proximal Femoral Osteotomy
Published on: February 17, 2023
Geometric optimization of femoral rotational alignment in total knee arthroplasty using minimal surface theory versus
Horacio Rivarola1, Cristian Collazo1, Marcos Palanconi1
1Department of Orthopaedic Surgery, Division of Knee Surgery, Hospital Universitario Austral, Pilar, Buenos Aires, Argentina.
Background:
Femoral rotational alignment is a critical determinant of contact mechanics, kinematics, and long-term survivorship in total knee arthroplasty (TKA). Traditional techniques rely on anatomical landmarks, which exhibit substantial inter-patient variability and may not reliably optimize tibiofemoral load distribution. This study introduces a geometric, anatomy-independent framework using minimal surface theory (MST) to identify an energy-minimizing femoral rotational alignment based on curvature equilibrium rather than fixed bony reference axes.
Methods:
A three-dimensional finite element model of the tibiofemoral articulation was constructed from computed tomography-derived anatomy. Posterior-stabilized TKA components were virtually implanted, and femoral rotation was varied from 5° internal to 5° external relative to the surgical transepicondylar axis. Simulations were performed at 0°, 45°, and 90° of flexion under a 700-N axial load. Willmore surface energy, mean contact pressure, peak shear stress, and contact area were quantified for each alignment. Sensitivity analyses evaluated robustness to posterior tibial slope (±3°) and insert conformity.
Results:
Across all flexion angles and model conditions, the MST-derived minimum energy state occurred consistently at 2°-3° of external rotation. Compared with neutral alignment, this optimized orientation reduced Willmore energy by 38.6 %, mean contact pressure by 18.7 %, and peak shear stress by 30.8 %, while increasing contact area by 13.1 %. Internal malrotation resulted in abrupt curvature transitions, elevated stress concentrations, and reduced load-sharing capacity. Findings remained stable across sensitivity analyses, indicating that the energy-optimal configuration is reproducible and not dependent on specific anatomical landmarks.
Conclusion:
Minimal surface theory identifies a narrow and consistent external rotational target that optimizes congruence and reduces mechanical stress in TKA. This framework provides a mathematically grounded, anatomy-independent alternative to conventional landmark-based alignment strategies and may support future computational or robotic applications for patient-specific rotational planning.
Level Of Evidence:
Computational simulation study (Level V).
