Advanced Grinding Solutions (AGS), Coventry, has supplied a GPA Innova Dlyte polishing machine to Implants International, a Thornaby-on-Tees-based bio-engineering specialist serving the arthroplasty, trauma and spinal implant sectors.
The machine is being used in the production of Implants International's ROTOglide artificial toe joint, a product that demands exceptionally high-quality mirror finishes on its cobalt chrome articulating surfaces. Originally designed by Implants International together with Professor Hakon Kofoed and launched in Denmark in 1998, the ROTOglide remains the world's only three-part artificial mobile meniscus toe joint.
Meeting the medical challengeThe ROTOglide implant is designed to treat Hallux Rigidus, an arthritic condition affecting the big toe joint that causes pain, stiffness and limited movement. The condition can significantly reduce mobility and alter the natural distribution of pressure through the foot.
As an uncemented, non-hinged surface-replacement arthroplasty, the implant is designed to replicate the natural torque and mobility of the first metatarso-phalangeal (MTP) joint. Its design restores anatomical movement while preserving as much primary bone stock as possible. Achieving this performance depends on highly polished articular surfaces, making surface finishing a critical manufacturing requirement.
The potential market for first MTP joint replacement is substantial. Across developed countries, Hallux Rigidus affects an estimated 2.5% of adults over the age of 50. In the United States alone, this could represent around 400,000 patients presenting annually. While many patients with severe symptoms continue to undergo joint fusion procedures because of the poor track record of earlier implant designs, Implants International says the ROTOglide has demonstrated long-term success with an unchanged design that has been in use for more than 25 years.
Delivering superior resultsDlyte polishing systems are widely used across numerous industrial sectors, with medical device manufacturing representing one of the most important application areas. Unlike traditional polishing methods, Dlyte technology maintains the original geometry of a component while producing a highly polished and homogeneous surface finish across the entire part.
The technology can process complex geometries without introducing micro-scratches and is capable of delivering mirror-like finishes in a single operation. This performance is achieved through GPA Innova's patented DryLyte technology, the world's first dry electropolishing process to use solid media rather than liquid electrolytes.
The process has proven biocompatibility and has been shown to be non-cytotoxic, attributes that make it particularly well suited to the production of medical devices where compliance with demanding regulatory and safety standards is essential.
DryLyte technology can reduce surface roughness by more than 80%, compared with conventional liquid electropolishing, which typically achieves less than a 50% reduction before risking unwanted effects such as pitting or orange-peel surface defects. The process also eliminates the need for hazardous chemical solutions and does not generate hazardous waste, providing both environmental and workplace safety benefits. Depending on the material and the condition of the surface prior to polishing, Dlyte systems can achieve final surface finishes of 0.05µm Ra or better.
A compact solutionFollowing an assessment of the application, AGS recommended the Dlyte 10L HF system. The compact machine provides a working envelope of 140mm diameter by 75mm high, enabling multiple ROTOglide implants to be processed simultaneously. Despite its capacity, the machine occupies a minimal footprint, measuring just 820mm long by 675mm wide.
Larger systems are also available within the Dlyte range, including the Dlyte Pro500, which can polish up to 24 artificial knee implants in a single batch.
AGS worked closely with Implants International and GPA Innova's application engineering team in Barcelona to validate the process before implementation. Much of the development work was carried out by Implants International's own engineers, who also installed the machine. Since entering production at the beginning of the year, the system has consistently met the demanding surface-finish requirements of the ROTOglide implant.
Headquartered in Barcelona, GPA Innova developed and patented the DryLyte process in 2016 and has since expanded internationally with operations in the USA, Hong Kong, China, Mexico and Poland. The company is represented in the UK by Advanced Grinding Solutions.
AGS will showcase a range of medical components produced using Dlyte polishing systems, together with other advanced manufacturing technologies, on Stand 49 at Medical Technology Ireland in Galway on 23 and 24 September.