In vivo osseointegration of a randomized trabecular titanium structure obtained by an additive manufacturing technique

The additive manufacturing techniques (AM) are able to realize three-dimensional trabecular structures that mimic thetrabecular structure of the bone. An in vivo study in sheep was carried out with the aim of assessing the bone response andthe trend of osteointegration of a randomized trabecular titanium structure produced by the AM technique. In 6 sheep wereimplanted 84 specimens with a trabecular titanium structure (4 implants in the femur distal epiphysis; 4 implants in the tibialplate; 6 implants in the tibial shaft). Sheep were sacrificed at 3 postoperative time-points: 6 weeks, 10 weeks, 14 weeks.Histomorphometric analysis was performed for the evaluation of Bone Implant Contact, and Bone Ingrowth. A standardpush-out test was used to analyze the mechanical characteristics of the bone-implant interface. The histomorphometric dataand biomechanical tests showed a fast osseointegration of the specimens both in the cancellous and in the cortical bone. Thequantitative analysis of osseointegration data in cancellous bone showed the percentage of the surface of the implant in directcontact with the regenerated bone matrix significantly improved from 28% at 6 weeks to 54% at 14 weeks. An earlyosseointegration occurred in cortical bone showing that 75% of surface of implant was in direct contact with regeneratedbone after 6 weeks; this value increased to 85% after 14 weeks. Mechanical tests revealed an early improvement of meanpeak load of implants at 10 weeks (4486 N ± 528 N) compared to values at 6 weeks (2516 N ± 910 N) confirming the highrate of progression of osseointegration in the cortical bone. The non-mineralized matrix followed an increasing process ofmineralization almost completely after 14 weeks. The results of this study have showed a rapid osseointegration andexcellent biocompatibility for a randomized trabecular titanium structure that should be confirmed by clinical investigations