Biomechanical Analysis of a spacer for knee neoplasms in terms of resection extension by means of finite elements

Abstract

When knee bony tumors appear, arthrodesis is one terapeutic option after tumor block resection. The implant is composed of an intramedular nail with four interlocking pins. The whole implant is manufactured using a titanium alloy (Ti-6Al-4V). The spacer has the capability of be extended from 20 cm up to 30 cm, and it is used as a definitively treatment. The use of this item reports good result despite the fact that affected limb is arthrodesed. However, it has a great interest to study the influence of bone tumor resection size on the implant integrity. To perform this research work, we developed a finite element model of the complex femur-implant-tibia, by means of Ansys software version 11 (Ansys, Inc). The loading conditions used during modeling process correspond to those occurring during midstance phase of gait. We analyzed six cases, varying spacer length: 20 cm, 22 cm, 24 cm, 26 cm, 28 cm and 30 cm. Our results indicate that there is no fracture failure risk within the implant when varying spacer length over the range previously stated, since we did not find significative difference on stress levels within the implant. However, stress levels of inter locking tibial pins are increased considerably for a resection of 24 cm or higher, this fact could lead us to implant loosening.

Keywords

• spacer
• arthrodesis
• finite Element