[Dynamic in vitro measurement of pressure and movement with the LCS prosthetic system]

This study measured the femoral inlay pressure and the movement of mobile bearing inlays after implantation of the LCS knee prosthetic system (DePuy,Warsaw, USA). The prostheses were implanted in seven fresh frozen knee specimens. This system offered three different types of inlays [classic (CL), A/P glide (APG), and rotating platform (ROT)] with the same type of femoral component. A pressure-sensitive film (Tekscan,Boston, USA) was attached on the surface of the inlay.T he movement of the inlay was measured by an ultrasonic positioning system (Zebris, Isny,Germany). The specimens were fixed in a hydraulic knee apparatus simulating an isokinetic extension movement from 120 degrees flexion to full extension. The hydraulic cylinder that simulated the musculus quadriceps femoris extended up to 1200 N. The pressure measurement showed a peak pressure of 4.4+/-1.5 MPa (CL),3.6+/-1.0 MPa (APG),and 9.8+/-1.3 MPa (ROT). The mobile bearing inlays moved 1.4+/-2.7 mm (CL) and 2.9+/-5.8 mm (APG) from posterior to anterior during extension of the knee. During the extension the inlays rotated 0.8+/-2.6 degrees (CL), 0.9+/-5.2 degrees (APG), and 3.2+/-6.9 degrees (ROT) internally.