The future of biologic coatings for orthopaedic implants

Abstract

Implants are widely used for orthopaedic applications such as fixing fractures, repairing non-unions, obtaining a joint arthrodesis, total joint arthroplasty, spinal reconstruction, and soft tissue anchorage. Previously, orthopaedic implants were designed simply as mechanical devices; the biological aspects of the implant were a byproduct of stable internal/external fixation of the device to the surrounding bone or soft tissue. More recently, biologic coatings have been incorporated into orthopaedic implants in order to modulate the surrounding biological environment. This opinion article reviews current and potential future use of biologic coatings for orthopaedic implants to facilitate osseointegration and mitigate possible adverse tissue responses including the foreign body reaction and implant infection. While many of these coatings are still in the preclinical testing stage, bioengineers, material scientists and surgeons continue to explore surface coatings as a means of improving clinical outcome of patients undergoing orthopaedic surgery.

Figure 1

(A) Layer-by-Layer deposition is formed through the sequential deposition of positive and negative charged polyelectrolytes. Biomolecules are entrapped within the polyelectrolyte layers and are released through degradation of the layers [56] (B) Micro-CT data showing ectopic bone formation following implantation of layer-by-layer coated scaffolds in the hind limbs of mice. Control scaffolds (vehicle) show very little radio opacity indicating that BMP-2 is necessary for bone formation. (C) Quantitative measurement of bone mineral density at the same time points chosen for micro-CT analysis [42]. Images have been adapted from [56] and [42].