Mechanics of post-cam engagement during simulated dynamic activity.
Bottom Line: Flexion angle and post-cam velocity at engagement demonstrated considerable ranges among designs (23°-89°, and 0.05-0.22 mm/°, respectively).Post-cam velocity was correlated (r = 0.89) with tibiofemoral condylar design features.Condylar geometry, in addition to post-cam geometry, played a significant role in minimizing engagement velocity and forces and stresses in the post.
Affiliation: Center for Orthopaedic Biomechanics, University of Denver, 2390 S. York St., Denver, Colorado 80208, USA.Show MeSH
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Mentions: External femoral torque imposed by the loading condition resulted in loading of the medial edge of the post and high ML force in Vanguard, Journey, Scorpio, and Sigma; Figs. 7 and 8). For Vanguard, the femoral box contacted with the anterior face of the post in early flexion, resulting in a net posterior force on the post until the cam made contact in later flexion. ML force on the post correlated well (r = 0.78) with the ML spacing between the post and femoral box; designs with a wider gap (Attune, NexGen) had lower ML force. An association between AP position of the posterior post surface and peak AP force on the post was found, but did not reach significance (r = 0.57, p = 0.1). The SI position (relative to the insert dwell point) at which initial contact occurred was correlated with flexion angle at engagement (r = −0.73) and post-cam velocity at engagement (−0.72); superior contact position on the post was related to an earlier engagement and slower velocity.
Affiliation: Center for Orthopaedic Biomechanics, University of Denver, 2390 S. York St., Denver, Colorado 80208, USA.