A Cadaveric Knee Study of the Kinematics of the Tibiofemoral and Patellofemoral Joints in Total Knee Replacement.

Abstract

Arthroplasty of the knee has become one of the commonest orthopaedic procedures performed today. In the UK alone over 75,000 were performed in 2011. Patients requiring arthroplasty are getting younger and have higher demands on their replaced joints leading to continued evolution of prosthetic design. This biomechanical work has compared two different designs of Total Knee Arthroplasty (TKA) in relation to each other and the native un-resurfaced knee. The TKAs differed from each other in design of the femoral component. One had a single radius design and a trochlea that ran from the lateral side proximally, to the medial side distally, and the other prosthesis had a multi radius design with a symmetrical trochlea, essentially an unsided femoral prosthesis. The principal areas of study were the kinematics of the tibiofemoral articulation (TF), the patellofemoral joint (PFJ), the stability of the patella in the replaced knee joint and contact pressures of the tibiofemoral articulation. This was a cadaveric study using a knee navigation system to record the kinematic data for analysis. All the experiments involved cadaveric left legs of different genders and sizes. All the work was carried out at the same laboratory at Imperial College, London between July 2006 and October 2008. Both TKAs allowed significantly greater laxity than the intact knee with an anterior drawer force applied as the knees moved from 40 degrees of flexion to full extension. No significant difference was found between the two TKAs used in this study in the TF work. For the PFJ, the multiradius design was significantly more stable when the patella was displaced medially than the intact knee (p=0.016) at 30 degrees of flexion. It was also more stable than the single radius design from 0-30 degrees of flexion. There were no significant differences found between the single radius TKA and the intact knee during any of the PFJ work. Both TKAs appeared to behave differently when assessing patellar flexion with marked differences shown graphically but no statistically significant difference shown on post testing.In conclusion, both designs of TKA replicated the intact knee very well throughout all the experiments, apart from the differences noted above. This study was unable to show any significant advantage of using the newer single radius design when compared to the established multi-radius design. The single radius design did not appear to mimic the kinematics of the intact knee any closer than the established multiradius design.