Time course of bone screw fixation following a local delivery of Zoledronate in a rat femoral model – A micro-finite element analysis

Abstract

Hydrogel BisphosphonateScrew fixation microCT microFE a b s t r a c t A good fixation of osteosynthesis implants is crucial for a successful bone healing but often difficult to achieve in osteoporotic patients. One possible solution to this issue is the local delivery of bisphosphonates in direct proximity to the implants, A critical aspect of this method, that has not yet been well investigated, is the time course of the implant fixation following the drug release. Usual destructive mechanical tests require large numbers of animals to produce meaningful results. Therefore, a micro-finite element (microFE) approach was chosen to analyze implant fixation. In vivo micro computed tomography (microCT) scans were obtained, first weekly and later bi-weekly, after implantation of polymeric screws in the femoral condyles of ovariectomized rats. In one half of the animals, Zoledronate was released from a hydrogel matrix directly in the peri-implant bone stock, the other animals were implanted only with screws as control. The time course of the implant fixation was investigated with linear elastic microFE models that were created based on in vivo microCT scans. The numerical models were validated against experimental pullout-tests measurements in an additional cadaver study. The microFE analysis revealed a significant increase in force at yield of the Zoledronate treated group compared to the control group. The force of the treated group was 28% higher after 17 days of screw implantation, 42% higher after 31 days. The significant difference persisted until the end of the in vivo study at day 58 (po0.01). The early onset and prolonged duration of the implant anchorage improvement that was found in this study indicates the great potential of Zoledronate-loaded hydrogel for an enhancement of osteosynthesis implant fixation in impaired bone.

Relative effects of age on implant integration in a rat model: A longitudinal in vivo microct study

“…Our model enables longitudinal, time‐dependent measurements of bone distribution, changes and of the resulting implant fixation. Since this approach was first reported it was successfully used to describe bone dynamics around bisphosphonate‐releasing implants, around infected implants and in osteoporotic animals . But to acquire images with high enough quality, BaSO 4 loaded PEEK screws are used, instead of more standard stainless steel or titanium screws, which would generate metallic artifacts in tomographic reconstructions .…”

Importance of trabecular anisotropy in finite element predictions of patellar strain after Total Knee Arthroplasty

“…We evaluated octahedral shear strain of all patellae [18] , for the isotropic and anisotropic models, and for the non-resurfaced and resurfaced cases. To compare isotropy to anisotropy, we calculated for the two cases the volume of bone with a strain above a threshold value.…”

Fixed and mobile-bearing total ankle prostheses: Effect on tibial bone strain

“…The octahedral shear strain invariant was evaluated within the tibial bone (Nagaraja et al 2005;Kettenberger et al 2015). Within the manuscript, strain always refer to this invariant.…”