Design of asymmetric prosthesis and mechanical analysis of total knee arthroplasty

doi:10.12307/2025.122

Abstract

Abstract: BACKGROUND: Total knee arthroplasty serves as an effective intervention for the treatment of late-stage knee joint disorders. However, prosthetic liners are prone to wear and failure due to internal stress variations, resulting in limited lifespan and decreased postoperative patient activity. Addressing how to enhance prosthetic design to meet a broader range of patient needs constitutes a significant focus in prosthesis research.
OBJECTIVE: Based on the morphological design of the meniscus, we propose an asymmetric design prosthesis and compare it with a symmetric posterior stabilized prosthesis. The stress distribution patterns and variations in the contact area of the liners for both prostheses were analyzed to explore whether the asymmetric prosthesis design offers advantages over the symmetric design.

METHODS: Using the finite element method, we simulated the osteotomy and prosthesis assembly in a knee osteoarthritis patient. Two different prostheses (asymmetric design and posterior stabilized) were employed to establish post-total knee arthroplasty knee joint models. Under flexion conditions at 0°, 10°, 20°, and 30°, we investigated the Mises stress on the femoral and tibial components as well as the liner. Additionally, by comparing the contact area on the inner and outer sides of the liner, we aimed to explore the changes in biomechanics and alterations in motion behavior in the post-total knee arthroplasty knee joint.
RESULTS AND CONCLUSION: (1) Throughout the flexion range from 0 to 30 degrees, the Mises stress peak on the liner exhibited a trend of initial decrease followed by an increase, with the stress on the medial side consistently surpassing that on the lateral side. (2) In comparison to the posterior stabilized prosthesis, the asymmetrically designed prosthesis demonstrated smaller stress peaks. At a flexion angle of 30 degrees, the Mises stress peak values of the medial and lateral parts of the asymmetric prosthesis were 15.81 MPa and 11.95 MPa, and those of the posterior stabilization prosthesis were 16.70 MPa and 13.76 MPa. The difference of Mises stress on the medial part was 5.33%, and the difference of Mises stress on the lateral part was 13.15%. Comparing the peak Mises stress on the femoral and tibial components, the asymmetric component was always lower than the posterior stable component during knee flexion.
(3) In the upright position at 0 degrees, the medial contact area of the posterior stabilization prosthesis was 17.96 mm2, and the lateral contact area was
34.10 mm2. The contact area on the inner and outer sides of the asymmetric design prosthesis liner was 105.47 mm2 and 107.80 mm2, respectively, indicating a larger contact area with a smaller difference between the inner and outer sides. (4) These results suggest that the biomechanical performance of the asymmetric prosthesis is superior, contributing to the maintenance of knee joint stability and improved joint mobility. This design, to a certain extent, mimics the rotational motion mechanism of the knee joint about the medial condyle as an axis, making it a more effective choice for knee joint prosthesis selection.

Key words: knee joint, total knee arthroplasty, asymmetric design prosthesis, biomechanics, finite element analysis

CLC Number:

Su Dejun, Dong Wanpeng, Dong Yuefu, Zhang Jichao, Zhang Zhen. Design of asymmetric prosthesis and mechanical analysis of total knee arthroplasty[J]. Chinese Journal of Tissue Engineering Research, 2025, 29(3): 510-516.

Figures/Tables 4

2.2 非对称型假体的有限元分析结果非对称型假体衬垫在屈膝时的内、外侧Mises应力峰值分别为：0°时为10.76 MPa和9.46 MPa，10°时为9.55 MPa和7.39 MPa，20°时为16.03 MPa和7.41 MPa，30°时为15.81 MPa和11.95 MPa。衬垫内外侧应力峰值的最高值分别出现在屈膝20°和屈膝30°时；股骨假体在0°，10°，20°，30°屈膝时的应力峰值分别为11.77，18.68，20.25，25.75 MPa；而胫骨假体的应力峰值数值分别为124.40，35.34，70.11，76.07 MPa。非对称型假体各角度下的应力分布情况如图7所示。 2.3 后稳定型衬垫和非对称型衬垫的对比分析通过后稳定型衬垫和非对称型衬垫上的Mises应力峰值对比可以看出，二者的变化趋势有一定的相似性，如图8所示。在0°-30°的屈膝变化中，屈膝10°时应力最小，随着屈膝角度的增加，应力峰值不断提高，应力峰值的最大值大部分出现在屈膝30°时。且在整个屈膝过程中，2种衬垫内外侧的应力峰值都保持着内侧大于外侧的趋势，这与已有的文献中对站立位下的研究结果类似[25-26]。从10°屈膝到20°屈膝的变化过程中，2种衬垫内外侧的应力峰值都有着较为明显的增长，后稳定型假体衬垫内侧增幅58.1%，外侧增幅45.2%；非对称型假体衬垫内侧增幅67.9%，而外侧仅增幅不到3%，这种较为平稳的应力变化，有助于维持膝关节在屈膝过程中的稳定性。同时，非对称型假体的整体应力水平更低，生物力学表现更好，对于延缓假体磨损更有优势。结合衬垫内外侧接触面积的变化也可以观察出屈膝过程中应力的变化规律。图9为0°-30°屈膝过程中2种假体衬垫接触面积的变化情况。在0°站立位时，后稳定型假体衬垫的内侧接触面积为17.96 mm2、外侧为34.10 mm2。衬垫内侧的接触面积变化规律表现出随屈膝角度的增加不断增大的趋势，而外侧则是在站立位时接触面积最大，屈膝10°时接触面积最小并随屈膝角度的增加而增大。非对称型假体衬垫在站立位时内外侧的接触面积分别为105.47 mm2和107.80 mm2，其设计是与股骨假体下表面高度吻合的，使得在屈膝过程中的接触面积更大。且在10°-30°的屈膝过程中，非对称型假体内侧的接触面积始终维持在46 mm2左右，接触位置一直保持在中部靠后的位置，没有较大的改变，形成了类似于自然膝关节中以内侧髁为轴心旋转的运动方式。这种接触方式很好地展现了屈膝过程中膝关节假体内侧维持稳定性的作用，符合非对称型假体衬垫的设计理念。"

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