Finite element analysis of tibio-femoral contact mechanics of a customised knee spacer

With one-third of patients having osteoarthritis predominantly in one compartment of the knee, unicompartmental knee spacers have been introduced as a less invasive alternative to total knee replacement. However, patients with the knee spacer implanted were seen to have persistent pain, resulting in high revision rates. A static finite element model of the knee and its interaction with a knee spacer implant at full extension and 90° flexion was used to investigate the tibio-femoral contact mechanics of the knee joint after a knee spacer surgery. Three different knee spacer designs (contoured, flat and C-shaped) were modelled and prescribed with cobalt-chrome, ultra-high molecular polyethylene and polyurethane material properties. The results suggested that a softer spacer is generally preferred as this helps in the conformity of knee spacer to the condyle, effectively distributing the load subjected to the implant. Flat spacers that result in high stresses resulting from lower contact areas should be avoided.