Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs
- 884 Downloads
Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs.
All prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30° and 130° of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras.
The post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle.
Post-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs.
KeywordsIn vitro study Posterior-stabilized TKA Post-cam failure Kinematics
- 4.Blackburne JS, Peel TE (1977) A new method of measuring patellar height. J Bone Joint Surg Br 59-B:241–242Google Scholar
- 20.O’Rourke MR, Callaghan JJ, Goetz DD et al (2002) Osteolysis associated with a cemented modular posterior cruciate substituting total knee design: five to eight -year follow-up. JBJS 84:1362–1371Google Scholar
- 21.Puloski SK, Mc Calden RW, Mac Donald SJ et al (2001) Tibial post wear in posterior stabilized total knee arthroplasty. An unrecognized source of polyethylene debris. JBJS 83:390–397Google Scholar
- 22.Sharkey PF, Hozack WJ, Booth RE et al (1992) Posterior dislocation of total knee arthroplasty. Clin Orhop Rel Res 278:128–133Google Scholar
- 27.Verra WC, van den Boom LG, Jacobs W, Clement DJ, Wymenga AA, Nelissen RG (2013) Retention versus sacrifice of the posterior cruciate ligament in total knee replacement for treatment of osteoarthritis and rheumatoid arthritis, Cochrane reviewGoogle Scholar