Innovate UK funding is supporting the next stage in development of the Smart Spacer from implant manufacturers MatOrtho and the Wallwork Group.

Smart Spacer applies a chromium-nitride silver coating (CrN-Ag) directly to an existing cobalt-chromium total knee replacement (TKR) implant for use as a temporary spacer device during two-stage treatment of peri-prosthetic infection. It will directly treat antibiotic-resistant infections such as methicillin-resistant staphylococcus aureus and staphylococcus epidermis, presenting significant advantages over current treatments and for the future of a coated prosthesis as long-term primary treatment.

Wallwork specializes in hard coating developments and applications providing a coating process service using the company’s physical vapor deposition (PVD) machines. The company provides nano-composite coatings that improve surface characteristics and performance in a range of industries.

The Wallwork CrN-Ag coating to be applied to the Smart Spacer has two initial functions – the release of silver ions can actively reduce infection and the coating provides a barrier to the device, protecting the surface and preventing the leaching of metal ions into the patient. Initial trials have shown ion leakage to be virtually nil at 200x less than that for uncoated devices. The coating will be engineered to work in two stages with movement and loading of the knee joint triggering an initial boost of silver ions from the sacrificial surface layer to counter infection immediately after implantation. The device will release lower levels of silver ions as recovery progresses.

Initial development work will focus on accelerated life testing of the coated knee joints by mechanical simulation so that the engineering of the coating can be perfected. The expectation is that the coated Smart Spacer will facilitate speedier stabilization of the infection and may reduce the reliance on large doses of antibiotics. Success as a spacer will then create a pathway for similarly coated TKR devices to proceed for further trials as a primary knee replacement.

Significant support is being provided by the Royal National Orthopaedic Hospital, University College London, and Queen Mary University London.,,