The use of a force-controlled dynamic knee simulator to quantify the mechanical performance of total knee replacement designs during functional activity

The experimental evaluation of any total knee replacement (TKR) design shou ld include the pre-implantation quantification of its mechanical performanc e during tests that simulate the common activities of daily living. To date , few dynamic TKR simulation studies have been conducted before implantatio n. Once in vivo, the accurate and reproducible assessment of TKR design mec hanics is exceedingly difficult, with the secondary variables of the patien t and the surgical technique hindering research. The current study utilizes a 6-degree-of-freedom force-controlled knee simulator to quantify the effe ct of TKR design alone on TKR mechanics during a simulated walking cycle. R esults show that all eight TKR designs tested elicited statistically differ ent measures of tibial/femoral kinematics, simulated soft tissue loading, a nd implant geometric restraint loading during an identical simulated gait c ycle, and that these differences were a direct result of TKR design alone. Maximum ranges of tibial kinematics over the eight designs tested were from 0.8 mm anterior to 6.4 mm posterior tibial displacement, and 14.1 degrees internal to 6.0 degrees external tibial rotation during the walking cycle. Soft tissue and implant reaction forces ranged from 106 and 222N anteriorly to 19 and 127N posteriorly, and from 1.6 and 1.8 Nm internally to 3.5 and 5.9 Nm externally, respectively. These measures provide valuable experiment al insight into the effect of TKR design alone on simulated in vivo TKR kin ematics, bone interface loading and soft tissue loading. Future studies uti lizing this methodology should investigate the effect of experimentally con trolled variations in surgical and patient factors on TKR performance durin g simulated dynamic activity. (C) 2000 Elsevier Science Ltd. All rights res erved.