Quadriceps force after non- hinged and hinged TKA

Patients who received total knee arthroplasty §frequently show problems during §knee extension exercises due to biomechanical §alterations. Hinged knee prostheses, which §provide higher stability than non-hinged designs, §were supposed to minimize them. §Therefore we investigated the quadriceps force §required to extend the knee after non-hinged and §hinged total knee arthroplasty. Human knee specimens §were tested in a kinematic knee simulator in §physiologic conditions, after implantation of two §types of non-hinged cruciate retaining prosthesis §and a hinged prosthesis. During simulation of an §extension cycle, the change of quadriceps force to §produce the constant extension moment of 31 Nm was §measured using a load cell attached to the §quadriceps tendon. After implantation of the non-§hinged prostheses maximum quadriceps force increased §up to 1257 N in knee extension. Following the §implantation of the hinged prosthesis quadriceps §extension force decreased to 690 N in §extension. Hinged knee prostheses improve the lever §arm in knee extension due to higher knee joint §stability. This would offer a potential advantage §for patients.