Development of a biomechanically optimized multi-component fiber-reinforced composite implant for load-sharing conditions.

Zhao DS, Moritz N, Laurila P, Mattila R, Lassila LVJ, Strandberg N, Mäntylä T, Vallittu PK, Aro HT.

An intramedullary implant made of unidirectional fibre-reinforced composite with S53P4 bioactive glass granule coating was tested in a preclinical experiment. Control implants were made of surface-roughened titanium. Surgical stabilation of bone metastasis in the subtrochanteric region of the femur was simulated in rabbits. An oblong subtrochanteric defect was created and either the intramedullary composite or titanium implant was inserted.

The follow-up time was 12 weeks. Finite element modelling (FEM) was used in order to analyse stress-shielding effects of the implants. The functional recovery was normal in both groups and no adverse reactions were observed. However, two healed undisplaced peri-implant fractures were found in composite implant group. Biomechanical tests revealed that the torsional strength of the operated femurs had returned the level of the intact femurs. Both groups showed ongrowth of intramedullary new bone. FEM simulation demonstrated that composite implants caused less stress-shielding than titanium implants. 

Med Eng Phys 2009;31:461-469.