SURGERY Article sponsored by Petcam ®
Prevention of Implant Failure
After Osteosynthesis Procedures for
Appendicular Fractures
Image taken from Steeples Vet Clinic http :// steeplesvetclinic . com /
Dr . Adriaan Kitshoff BVSc ( Hons .), MSc , Dipl . ECVS
Implant failure relates to any factor the leads to loss of fracture stability or fracture alignment in the post-operative period after successful osteosynthesis .
The factors can be better characterised as either a failure at the bone implant interface or mechanical failure of the implant .
The bone implant interface is defined as the shared boundary between the implant and the bone . The interaction between the two surfaces is extremely dynamic , constantly changing from the time of implant placement until the time of healing . Bone repair around the implant is reliant on the local cellular activity . If excessive trauma ( thermal or mechanical ) occurs during insertion of the implant fibrous tissue will form and if vascularisation has not been established necrotic bone will develop next to the implant . Micro-motion ( due to inadequate fixation or external forces transposed to the interface ) can additionally lead to bone resorption and the formation of fibro-osseus tissue and predispose to failure of the implants . Various forces ( Van der Waals forces , hydrogen bonding , ionic bonding and covalent bonding ) play a role in the bond between the implant and the bone . The interaction of water with the mineral and collagen phase of bone significantly impacts on the mechanical behaviour of bone and is involved in the toughening of the bone tissues . Bone resorption due to micromotion and infection will affect these forces .
The material implanted might also affect the long term outcome . Implants can be classified as biotolerant , bioinert or bioactive . Implants made from stainless steel are biotolerant meaning that these implant will always have some soft tissue that forms in the interface between bone and implant which will always predisposing these implants to micromotion . Titanium implants on the other hand , are classified as bioactive as they allow for full bony integration . The strength of each one of these materials is the ability of that material to resist the forces applied to that material . These forces can be compressive , tensile or shear .
As soon as a force is applied to a material the material starts to deform . The deformation can be reversible vet360
Issue 06 | DECEMBER 2017 | 16