Osseointegration of acellular and cellularized osteoconductive scaffolds: is tissue engineering using mesenchymal stem cells necessary for implant fixation?

The main issue associated with revision total hip replacements (rTHRs) is how to generate new bone adjacent to implants and achieve fixation of the revision implant. In its simplest form, bone tissue engineering (BTE) combines cells and scaffolds in vitro to replace damaged or lost bone in vivo. Our aim was to develop BTE porous TiAl6V4 constructs with a calcium-phosphate coating without or with mesenchymal stem cells (MSCs) seeded throughout the entire porous structure to enhance new bone formation and which could be used for rTHRs. Porous titanium scaffolds made by selective laser sintering were seeded throughout with autologous bone marrow MSCs and cultured in a perfusion bioreactor. Constructs were implanted in the medial femoral condyle of 20 skeletally mature mule sheep with and without a gap of 2.5 mm between the construct and the host bone. After 6 weeks, the addition of MSCs to the scaffolds did not significantly increase osseointegration or implant-bone fixation strength. However, in the defects with a gap, the cellularized constructs showed higher implant-bone contact area and implant-bone fixation strength. BTE can be applied to develop acellular or cellularized constructs with clinical application in rTHRs where a lack of bone stock is problematic.