This technology, that is able to provide screw-strength fixation that can be tuned to different bone properties, whilst allowing non-axisymmetric/multiple fixation features, could enable new/improved orthopaedic treatments.

Proposed use

Various orthopaedic treatments

Problem addressed

Metal implants are used to treat orthopaedic trauma and disease around the body and include spinal fixators, bone fracture fixation plates, tendon repair anchors, ligament reconstruction fixation screws, chondral repair implants and total joint replacement implants. These implants are used in high volumes – it is estimated that 7 million Americans are currently living with a joint replacement.

Modern implants typically rely on press fit or screw fixation. However, because screws must be rotated about their own axis to achieve fixation, they are of no use for non-axisymmetric/ multiple fixation features.  Such designs either require modularity or press fit fixation. Modularity between screw fixation bases and other components can lead to problems with intraoperative assembly and fretting and corrosion wear; the subsequent soft tissue reactions to the resulting metal debris can cause a severe revision burden. Press fit fixations enable non-axisymmetric/multiple fixation features and are frequently used for arthroplasty components.  However, they are hard to tune to different bone types and provide lower initial fixation strength than screws.

Indeed, loosening is a primary reason for failure of joint replacement implants. A robust Implant fixation mechanism is critical to success of these procedures.

Technology overview

Our active fixation technology provides a mechanism to improve both the initial and long-term fixation as it has small, hook-like directionally biased features on the surface of an implant. Being directionally biased, these struts can flex into the implant upon insertion providing low push-in resistance whist they can then flex outwards and grip onto the bone upon providing a high stabilising force under pull-out.

Benefits

• A fixation surface that is easier to insert than to remove, halving the insertion force whilst doubling the anchoring forces compared to conventional press fit technology.
• Lower insertion force requires less implant impaction whilst guaranteeing fixation, benefiting minimally invasive/ robotic surgery and lowering impaction fracture risk
  Increased anchoring force offers new options for less invasive, smaller implant designs utilising low profile fixation.
• Combined with the inherent advantage of push-fit technology, not requiring rotational symmetry/ modularity, active fixation could simplify existing procedures whilst also enabling new treatment paradigms

Intellectual property information

EP3515366A1 – SURGICAL IMPLANT

US PATENT PENDING

Inventor information

Dr Jonathan Jeffers

Reader in Mechanical Engineering. He leads a team PhD students, research associates and registrar surgeons within the Biomechanics Research Group.  His research activity is to translate new treatments and implant technology to clinical use in the orthopaedic field.

Dr Richard Jan Van Arkel

Lecturer in the Department of Mechanical Engineering.  He applies engineering methodology to study orthopaedic systems, determining the impact of surgical interventions on joint biomechanics, the function of implants, and how new technologies, such as additive manufacturing, can improve treatments.

Dr Shaaz Ghouse

Research Associate in the Biomechanics group in the Department of Mechanical Engineering at Imperial College London, focusing on additive manufacturing (3D printing) of metal materials.

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