Post cam mechanism of Posterior Stabilized (PS) knee prostheses is useful to realize intrinsic stability for cases with severe degeneration. However, some retrieval studies report severe failure of the polyethylene tibial post. We thought that severe failures were caused by high loads during daily activities. In the current study, we performed a compression test and a finite element analysis of the mechanical forces produced in the tibial post in posterior-stabilized knee prostheses in order to develop a specification for the tibial posts found in the polyethylene inserts of PS knee prostheses. Anterior tibial post impingement and posterior tibial post impingement were simulated. The surface pressure values detected in the compression test were consistent with those obtained in the FE analysis. Of the three designs, the lowest von Mises stress values were generated inside the round tibial post; therefore, tibial posts should be round. The risk of tibial post failure was low when 500 or 1000 N was loaded onto the knee joint. It was suggested that tibial post failure occurs when the shear strain at the base of the tibial post exceeds 0.1.
References
[1]
Kumar, N., Yadav, C., Raj, R. and Yadav, S. (2015) Fracture of the Polyethylene Tibial Post in a Posterior Stabilized Knee Prosthesis: A Case Report and Review of Literature. Journal of Orthopaedics, 12, 160-163.
https://doi.org/10.1016/j.jor.2015.01.002
[2]
Lim, H.C., Bae, J.H., Hwang, J.H., Kim, S.J. and Yoon, J.Y. (2009) Fracture of a Polyethylene Tibial Post in a Scorpio Posterior-Stabilized Knee Prosthesis. Clinics in Orthopedic Surgery, 1, 118-121.
https://doi.org/10.4055/cios.2009.1.2.118
[3]
Jung, K.A., Lee, S.C., Hwang, S.H. and Kim, S.M. (2008) Fracture of a Second-Generation Highly Cross-Linked UHMWPE Tibial Post in a Posterior-Stabilized Scorpio Knee System. Orthopedics, 31, 1137.
https://doi.org/10.3928/01477447-20081101-10
[4]
Bal, B.S., Greenberg, D., Li, S., Mauerhan, D.R., Schultz, L. and Cherry, K. (2008) Tibial Post Failures in a Condylar Posterior Cruciate Substituting Total Knee Arthroplasty. The Journal of Arthroplasty, 23, 650-655.
https://doi.org/10.1016/j.arth.2007.08.002
[5]
Chiu, Y.S., Chen, W.M., Huang, C.K., Chiang, C.C. and Chen, T.H. (2004) Fracture of the Polyethylene Tibial Post in a NexGen Posterior-Stabilized Knee Prosthesis. The Journal of Arthroplasty, 19, 1045-1049.
https://doi.org/10.1016/j.arth.2004.04.013
[6]
Bartel, D.L., Rawlinson, J.J., Burstein, A.H., Ranawat, C.S. and Flynn, Jr., W.F. (1995) Stresses in Polyethylene Components of contemporary Total Knee Replacements. Clinical Orthopaedics Related Research, 317, 76-82.
[7]
Hamai, S., Miura, H., Matsuda, S., Shimoto, T., Higaki, H. and Iwamoto, Y. (2010) Contact Stress at the Anterior Aspect of the Tibial Post in Posterior-Stabilized Total Knee Replacement. The Journal of Bone and Joint Surgery America, 92, 1765-1773. https://doi.org/10.2106/jbjs.i.00479
[8]
Li, G., Papannagari, R., Most, E., Park, S.E., Johnson, T., Tanamal, L. and Rubash, H.E. (2005) Anterior Tibial Post Impingement in a Posterior Stabilized Total Knee Arthroplasty. Journal of Orthopaedic Research, 23, 536-541. https://doi.org/10.1016/j.orthres.2004.09.005
[9]
Akasaki, Y., Matsuda, S., Shimoto, T., Miura, H., Higaki, H. and Iwamoto, Y. (2008) Contact Stress Analysis of the Conforming Post-Cam Mechanism in Posterior-Stabilized Total Knee Arthroplasty. Journal of Arthroplasty, 23, 736-748. https://doi.org/10.1016/j.arth.2007.05.023
[10]
Nakayama, K., Matsuda, S., Miura, H., Higaki, H., Otsuka, K. and Iwamoto, Y. (2005) Contact Stress at the Post-Cam Mechanism in Posterior-Stabilised Total Knee Arthroplasty. The Journal of Bone and Joint Surgery British, 87-B, 483-488. https://doi.org/10.1302/0301-620x.87b4.15684
[11]
Nagura, T., Dyrby, C.O., Alexander, E.J. and Andriacchi, T.P. (2002) Mechanical Loads at the Knee Joint during Deep Flexion. Journal of Orthopaedic Research, 20, 881-886. https://doi.org/10.1016/s0736-0266(01)00178-4
