Biomechanical study on the combined effects of femoral component rotational malalignment and osteoporosis in unicompartmental knee arthroplasty_Journal of Biomedical Engineering

Authors：

 ZHOU Taoyong ¹ , LIU Pai ¹ , LU Ning ² , SUN Zhihang ² , TIAN Jiaxin ¹ , DIAO Caijia ¹

1. Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500, P. R. China;
2. Department of Orthopedics, the Second Affiliated Hospital of Kunming Medical University, Kunming 650101, P. R. China;

Corresponding?author：

ZHOU Taoyong, Email: kmzty@163.com

Keywords：

Unicompartmental knee arthroplasty; Femoral component rotation; Osteoporosis; Prosthesis subsidence; Biomechanics; Finite element analysis; Malrotation

DOI：

10.7507/1001-5515.202601021

Video：

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Mobile-bearing unicompartmental knee arthroplasty (UKA) is prone to rotational malalignment of the femoral component. Moreover, existing biomechanical studies frequently overlook the mechanical impact of patients’ bone quality on such surgical errors. To investigate the coupling effect of femoral component transverse rotation and bone quality on the biomechanical environment, a finite element model incorporating intact soft tissues was constructed. Based on bone mineral density variations, three models were established: normal bone (B1), osteopenia (B2), and osteoporosis (B3). Nine rotational conditions ranging from –14° to 14° in the transverse plane were simulated. Quantitative analysis revealed that external rotation significantly elevated the contact pressure on the polyethylene liner. Conversely, internal rotation (–14°) increased the lateral meniscus stress by approximately 16.8% compared to the neutral alignment (0°) via a “linkage mechanism”. Group B3 exhibited a pseudo “cushion effect”, wherein the peak strain of the tibial cancellous bone reached 5 883.9 με, exceeding the pathological threshold of 4 000 με; additionally, compared with Group B1, their average strain in the cortical bone increased by approximately 79.7%. In conclusion, transverse rotational malalignment of the femoral component serves as a direct mechanical trigger disrupting the biomechanical balance in UKA, and osteoporosis significantly amplifies this risk of failure. Therefore, for patients with compromised bone mass, strict neutral alignment must be pursued intraoperatively to circumvent cancellous bone microfractures and early prosthesis subsidence.

Citation： ZHOU Taoyong, LIU Pai, LU Ning, SUN Zhihang, TIAN Jiaxin, DIAO Caijia. Biomechanical study on the combined effects of femoral component rotational malalignment and osteoporosis in unicompartmental knee arthroplasty. Journal of Biomedical Engineering, 2026, 43(2): 242-249. doi: 10.7507/1001-5515.202601021 Copy

1.	Ren J L, Yang J, Hu W. The global burden of osteoarthritis knee: a secondary data analysis of a population-based study. Clin Rheumatol, 2025, 44(4): 1769-1810.
2.	Hansen E N, Ong K L, Lau E, et al. Unicondylar knee arthroplasty has fewer complications but higher revision rates than total knee arthroplasty in a study of large United States databases. J Arthroplasty, 2019, 34(8): 1617-1625.
3.	Murray D W, Goodfellow J W, O'Connor J J. The Oxford medial unicompartmental arthroplasty: a ten-year survival study. J Bone Joint Surg Br, 1998, 80(6): 983-989.
4.	Hamilton T W, Pandit H G, Maurer D G, et al. Anterior knee pain and evidence of osteoarthritis of the patellofemoral joint should not be considered contraindications to mobile-bearing unicompartmental knee arthroplasty. Bone Joint J, 2017, 99-B(5): 632-639.
5.	Bayoumi T, Kleeblad L J, Borus T A, et al. Ten-year survivorship and patient satisfaction following robotic-arm-assisted medial unicompartmental knee arthroplasty: a prospective multicenter study. J Bone Joint Surg Am, 2023, 105(12): 933-942.
6.	Johal S, Nakano N, Baxter M, et al. Unicompartmental knee arthroplasty: the past, current controversies, and future perspectives. J Knee Surg, 2018, 31(10): 992-998.
7.	Thoreau L, Marfil D M, Thienpont E. Periprosthetic fractures after medial unicompartmental knee arthroplasty: a narrative review. Arch Orthop Trauma Surg, 2022, 142(8): 2039-2048.
8.	Houskamp D J, Tompane T, Barlow B T. What is the critical tibial resection depth during unicompartmental knee arthroplasty? A biomechanical study of fracture risk. J Arthroplasty, 2020, 35(8): 2244-2248.
9.	Lingard E A, Mitchell S Y, Francis R M, et al. The prevalence of osteoporosis in patients with severe hip and knee osteoarthritis awaiting joint arthroplasty. Age Ageing, 2010, 39(2): 234-239.
10.	Zhuang Z K, Huang C Y, Chen X Y, et al. Prevalence of osteoporosis in patients awaiting unicompartmental knee arthroplasty: a cross-sectional study. Front Endocrinol, 2023, 14: 8.
11.	Hollensteiner M, Sandriesser S, Bliven E, et al. Biomechanics of osteoporotic fracture fixation. Curr Osteoporos Rep, 2019, 17(6): 363-374.
12.	劉蒙飛, 馬鵬程, 尹燦, 等. 不同骨密度對膝關節單髁置換后關節內各結構影響的三維有限元分析. 中國組織工程研究, 2024, 28(24): 3801-3806.
13.	Ma P C, Muheremu A, Zhang S P, et al. Biomechanical effects of fixed-bearing femoral prostheses with different coronal positions in medial unicompartmental knee arthroplasty. J Orthop Surg Res, 2022, 17(1): 12.
14.	Innocenti B, Pianigiani S, Ramundo G, et al. Biomechanical effects of different varus and valgus alignments in medial unicompartmental knee arthroplasty. J Arthroplasty, 2016, 31(12): 2685-2691.
15.	Scheele C B, Pietschmann M F, Schr?der C, et al. Effect of bone density and cement morphology on biomechanical stability of tibial unicompartmental knee arthroplasty. Knee, 2020, 27(2): 587-597.
16.	Liu M, Jiang K, Ju X. Biomechanical effects of femoral prosthesis misalignment on the structure of the lateral compartment during medial unicompartmental knee arthroplasty in osteoporotic patients. J Orthop Surg (Hong Kong), 2024, 32(2): 10225536241273924.
17.	Kang K T, Kwon O R, Son J, et al. Effect of joint line preservation on mobile-type bearing unicompartmental knee arthroplasty: finite element analysis. Australas Phys Eng Sci Med, 2018, 41(1): 201-208.
18.	Liu W T, Lin B, Zhang X, et al. The effect of femoral component valgus/varus angle on the mid-term efficacy of unicondylar knee arthroplasty. Biotechnol Genet Eng Rev, 2024, 40(1): 1-14.
19.	Koh Y G, Park K M, Lee H Y, et al. Influence of tibiofemoral congruency design on the wear of patient-specific unicompartmental knee arthroplasty using finite element analysis. Bone Joint Res, 2019, 8(3): 156-164.
20.	Chen X D, Xue C G, Li K X, et al. Finite element analysis of anterior cruciate ligament reconstruction techniques: a comparison of the mechanical properties of all-inside fixation and traditional fixation. Front Bioeng Biotechnol, 2024, 12: 10.
21.	Steineman B D, Chastain K L, Letendre S C, et al. In pursuit of quantifying patient knee contact mechanics: finite element model validation of cadaveric knees in axially loaded MRI scans. J Orthop Res, 2025, 43(6): 1132-1143.
22.	Kang K T, Son J, Koh Y G, et al. Effect of femoral component position on biomechanical outcomes of unicompartmental knee arthroplasty. Knee, 2018, 25(3): 491-498.
23.	Kono K, Yamazaki T, Tamaki M, et al. In vivo kinematic analysis of mobile-bearing unicompartmental knee arthroplasty during high flexion activities. J Knee Surg, 2024, 37(9): 649-655.
24.	Van Der List J P, Zuiderbaan H A, Pearle A D. Why do medial unicompartmental knee arthroplasties fail today? J Arthroplasty, 2016, 31(5): 1016-1021.
25.	Campi S, Kendrick B, Kaptein B, et al. Five-year results of a randomised controlled trial comparing cemented and cementless Oxford unicompartmental knee replacement using radiostereometric analysis. Knee, 2021, 28: 383-390.
26.	Frost H M. Bone’s mechanostat: a 2003 update. Anat Rec A Discov Mol Cell Evol Biol, 2003, 275A(2): 1081-1101.
27.	Zhu G D, Guo W S, Zhang Q D, et al. Finite element analysis of mobile-bearing unicompartmental knee arthroplasty: the influence of tibial component coronal alignment. Chin Med J (Engl), 2015, 128(21): 2873-2878.
28.	Sakai S, Kuriyama S, Morita Y, et al. Impact of medial tibial overresection on bone mineral density in unicompartmental knee arthroplasty. J Orthop Res, 2025, 43(11): 1954-1963.
29.	Simpson D J, Gray H, D’Lima D, et al. The effect of bearing congruency, thickness and alignment on the stresses in unicompartmental knee replacements. Clin Biomech, 2008, 23(9): 1148-1157.
30.	Peersman G, Taylan O, Slane J, et al. Does unicondylar knee arthroplasty affect tibial bone strain? A paired cadaveric comparison of fixed-and mobile-bearing designs. Clin Orthop Relat Res, 2020, 478(9): 1990-2000.
31.	Bocchino G, Totti R, Comodo R M, et al. Chronic pain following unicompartmental knee arthroplasty: a narrative review and illustrative case report on genicular artery embolization using imipenem/cilastatin. Appl Sci, 2026, 16(1): 361.

1. Ren J L, Yang J, Hu W. The global burden of osteoarthritis knee: a secondary data analysis of a population-based study. Clin Rheumatol, 2025, 44(4): 1769-1810.
2. Hansen E N, Ong K L, Lau E, et al. Unicondylar knee arthroplasty has fewer complications but higher revision rates than total knee arthroplasty in a study of large United States databases. J Arthroplasty, 2019, 34(8): 1617-1625.
3. Murray D W, Goodfellow J W, O'Connor J J. The Oxford medial unicompartmental arthroplasty: a ten-year survival study. J Bone Joint Surg Br, 1998, 80(6): 983-989.
4. Hamilton T W, Pandit H G, Maurer D G, et al. Anterior knee pain and evidence of osteoarthritis of the patellofemoral joint should not be considered contraindications to mobile-bearing unicompartmental knee arthroplasty. Bone Joint J, 2017, 99-B(5): 632-639.
5. Bayoumi T, Kleeblad L J, Borus T A, et al. Ten-year survivorship and patient satisfaction following robotic-arm-assisted medial unicompartmental knee arthroplasty: a prospective multicenter study. J Bone Joint Surg Am, 2023, 105(12): 933-942.
6. Johal S, Nakano N, Baxter M, et al. Unicompartmental knee arthroplasty: the past, current controversies, and future perspectives. J Knee Surg, 2018, 31(10): 992-998.
7. Thoreau L, Marfil D M, Thienpont E. Periprosthetic fractures after medial unicompartmental knee arthroplasty: a narrative review. Arch Orthop Trauma Surg, 2022, 142(8): 2039-2048.
8. Houskamp D J, Tompane T, Barlow B T. What is the critical tibial resection depth during unicompartmental knee arthroplasty? A biomechanical study of fracture risk. J Arthroplasty, 2020, 35(8): 2244-2248.
9. Lingard E A, Mitchell S Y, Francis R M, et al. The prevalence of osteoporosis in patients with severe hip and knee osteoarthritis awaiting joint arthroplasty. Age Ageing, 2010, 39(2): 234-239.
10. Zhuang Z K, Huang C Y, Chen X Y, et al. Prevalence of osteoporosis in patients awaiting unicompartmental knee arthroplasty: a cross-sectional study. Front Endocrinol, 2023, 14: 8.
11. Hollensteiner M, Sandriesser S, Bliven E, et al. Biomechanics of osteoporotic fracture fixation. Curr Osteoporos Rep, 2019, 17(6): 363-374.
12. 劉蒙飛, 馬鵬程, 尹燦, 等. 不同骨密度對膝關節單髁置換后關節內各結構影響的三維有限元分析. 中國組織工程研究, 2024, 28(24): 3801-3806.
13. Ma P C, Muheremu A, Zhang S P, et al. Biomechanical effects of fixed-bearing femoral prostheses with different coronal positions in medial unicompartmental knee arthroplasty. J Orthop Surg Res, 2022, 17(1): 12.
14. Innocenti B, Pianigiani S, Ramundo G, et al. Biomechanical effects of different varus and valgus alignments in medial unicompartmental knee arthroplasty. J Arthroplasty, 2016, 31(12): 2685-2691.
15. Scheele C B, Pietschmann M F, Schr?der C, et al. Effect of bone density and cement morphology on biomechanical stability of tibial unicompartmental knee arthroplasty. Knee, 2020, 27(2): 587-597.
16. Liu M, Jiang K, Ju X. Biomechanical effects of femoral prosthesis misalignment on the structure of the lateral compartment during medial unicompartmental knee arthroplasty in osteoporotic patients. J Orthop Surg (Hong Kong), 2024, 32(2): 10225536241273924.
17. Kang K T, Kwon O R, Son J, et al. Effect of joint line preservation on mobile-type bearing unicompartmental knee arthroplasty: finite element analysis. Australas Phys Eng Sci Med, 2018, 41(1): 201-208.
18. Liu W T, Lin B, Zhang X, et al. The effect of femoral component valgus/varus angle on the mid-term efficacy of unicondylar knee arthroplasty. Biotechnol Genet Eng Rev, 2024, 40(1): 1-14.
19. Koh Y G, Park K M, Lee H Y, et al. Influence of tibiofemoral congruency design on the wear of patient-specific unicompartmental knee arthroplasty using finite element analysis. Bone Joint Res, 2019, 8(3): 156-164.
20. Chen X D, Xue C G, Li K X, et al. Finite element analysis of anterior cruciate ligament reconstruction techniques: a comparison of the mechanical properties of all-inside fixation and traditional fixation. Front Bioeng Biotechnol, 2024, 12: 10.
21. Steineman B D, Chastain K L, Letendre S C, et al. In pursuit of quantifying patient knee contact mechanics: finite element model validation of cadaveric knees in axially loaded MRI scans. J Orthop Res, 2025, 43(6): 1132-1143.
22. Kang K T, Son J, Koh Y G, et al. Effect of femoral component position on biomechanical outcomes of unicompartmental knee arthroplasty. Knee, 2018, 25(3): 491-498.
23. Kono K, Yamazaki T, Tamaki M, et al. In vivo kinematic analysis of mobile-bearing unicompartmental knee arthroplasty during high flexion activities. J Knee Surg, 2024, 37(9): 649-655.
24. Van Der List J P, Zuiderbaan H A, Pearle A D. Why do medial unicompartmental knee arthroplasties fail today? J Arthroplasty, 2016, 31(5): 1016-1021.
25. Campi S, Kendrick B, Kaptein B, et al. Five-year results of a randomised controlled trial comparing cemented and cementless Oxford unicompartmental knee replacement using radiostereometric analysis. Knee, 2021, 28: 383-390.
26. Frost H M. Bone’s mechanostat: a 2003 update. Anat Rec A Discov Mol Cell Evol Biol, 2003, 275A(2): 1081-1101.
27. Zhu G D, Guo W S, Zhang Q D, et al. Finite element analysis of mobile-bearing unicompartmental knee arthroplasty: the influence of tibial component coronal alignment. Chin Med J (Engl), 2015, 128(21): 2873-2878.
28. Sakai S, Kuriyama S, Morita Y, et al. Impact of medial tibial overresection on bone mineral density in unicompartmental knee arthroplasty. J Orthop Res, 2025, 43(11): 1954-1963.
29. Simpson D J, Gray H, D’Lima D, et al. The effect of bearing congruency, thickness and alignment on the stresses in unicompartmental knee replacements. Clin Biomech, 2008, 23(9): 1148-1157.
30. Peersman G, Taylan O, Slane J, et al. Does unicondylar knee arthroplasty affect tibial bone strain? A paired cadaveric comparison of fixed-and mobile-bearing designs. Clin Orthop Relat Res, 2020, 478(9): 1990-2000.
31. Bocchino G, Totti R, Comodo R M, et al. Chronic pain following unicompartmental knee arthroplasty: a narrative review and illustrative case report on genicular artery embolization using imipenem/cilastatin. Appl Sci, 2026, 16(1): 361.

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