New Smart Sensors Developed to Aid Joint Implant Positioning

New smart sensors, which assist in the soft tissue balancing and correct positioning of an orthopedic implant during hip replacement, are expected to prolong implant lifetimes and reduce the chances of patients needing difficult revision surgery.
 
Currently, implant survival rates are 89% after 15 years, but drop to 58% after 25 years (Sodhi & Mont, Lancet 2019). Thus, for the younger patient in particular, it is crucial to improve implant survival lifetimes to reduce the need for multiple revision surgeries when they grow older.  
 
New microfluidic force sensors are being developed within the University of Cambridge laboratory of Professor Sohini Kar-Narayan, in close collaboration with Vikas Khanduja, a consultant orthopedic surgeon at Addenbrooke’s Cambridge University Hospitals NHS Trust. This initiative has won the Armourers and Brasiers Venture Prize.  
 
“This is a key clinical unmet need, particularly for the hip joint,” explained Khanduja. “Improper implant positioning, where forces on the implant are not balanced, can lead to premature wear and necessitating complex and expensive revision procedures.  Integrating sensors within the trial liners during surgery will provide real-time objective feedback to facilitate soft tissue balancing and accurate implant placement, thereby potentially prolonging the longevity of the implant.”
 
To facilitate the sensors’ commercialization, the team has incorporated a spin-out company called ArtioSense Limited.
 
ArtioSense’s smart sensor-embedded trial liners that fit in the hip implant will aid surgeons in determining the optimum, force-balanced positioning of the implant via real-time measurements obviating the sole reliance on ‘feel’ for positioning and balance. Once the optimum position is set, the surgeon removes the ArtioSense sensor-embedded liners, and fit in the final liner. The ArtioSense product is only used as a trial during surgery, and is not left in the patient.
 
Market data predicts that more than 2.1 million hip replacements are performed annually worldwide. This number is expected to grow further due to the increasing global life expectancy and a growing proportion of younger patients opting for elective joint replacement. In the United Kingdom, the 80,000 hip replacemnents performed in 2020 is expected to swell to roughly 96,000 by 2035. The number of U.S. total hip replacement procedures is expected to increase from 498,000 in 2020 to 850,000 in 2030 and 1.42 million in 2040. 
 
The ArtioSense sensors are integrated directly into trial inserts that are already used during surgery. There is no need to change the surgical process and the sensors add functionality to the existing surgical workflow to improve outcomes. 
 
“This makes our technology attractive to both the surgeon, as well as the implant manufacturers, who simply need to integrate our technology into an already existing manufacturing workflow, ” explained Kar-Narayan. “In addition, the sensors will be fabricated from inexpensive materials so will not add significantly to costs. Our primary focus is on developing our smart trial liners for hip implants. However, the technology is versatile and customisable, and can be applied to similar use in other joints such as the knee, shoulders and ankles and could be adapted for use in veterinary surgery as well.”
 
ArtioSense is showing how research and innovation has the potential to improve the quality of life of patients receiving joint replacements,” said Professor Bill Bonfield, chairman of the Armourers and Brasiers Venture Prize judging panel. “Our prize looks to encourage scientific entrepreneurship in the U.K. and provide funding to help innovative developments like this realise their potential.”   
 
Along with Kar-Narayan and Khanduja, ArtioSense co-founders include Dr. Jehangir Cama, a biophysicist specializing in microfluidics, and Dr. Alexander Samoshkin, a biomedical technology transfer specialist. ArtioSense is combining the £25,000 Venture Prize win with its planned seed-funding round to support the development and finalization of product specifications for the hip implant prosthesis, in advance of first-in-human trials. 
 
A patent application covering ArtioSense’s microfluidic force sensing technology has been filed through Cambridge Enterprise (CE), the commercialisation arm of the University of Cambridge, which is also assiting Artiosense with its commercialisation plans
 
The Armourers and Brasiers’ Company supports materials science education and research in the U.K.  Its Venture Prize is aimed at helping scientists commercialize early stage research and the exploitation of new and exciting ideas. 
 
Kar-Narayan is a professor of Device & Energy Materials in the Department of Materials Science. Khanduja is a consultant orthopedic surgeon and research lead (elective) at Addenbrooke’s – Cambridge University Hospital, specializing in hip surgery and has a particular interest in hip arthroscopic surgery. He has been instrumental in setting up and developing the tertiary referral service for Young Adult Hip Surgery in Cambridge and also leads the Cambridge Young Adult Hip Research Group. Khanduja is the recipient of the Arnott Medal presented by the RCS of England in 2013, the Insall Fellowship presented by the American Knee Society and Insall Foundation in 2014, and the Hunterian Professorship by RCS England in 2021. He also sits on the Executive Committee of the British Hip Society as president and ESSKA as chair of European Hip Preservation Associates.

Cama is a biophysicist with expertise in the development of microfluidic technologies for a range of biomedical applications. Samoshkin currently works as a translational technology manager at the University of Cambridge (School of Clinical Medicine). He has previous experience in biomedical research laboratories in the United States and Canada.

ArtioSense’s smart sensor-embedded trial liners operate by monitoring the change in capacitance of the electrodes as the fluid in the microfluidic channel is displaced in response to an applied force. Using a bespoke mechanical testing rig, it calibrates the capacitance change of these sensors based on known applied forces, and this calibration data is used to determine the forces applied to the sensors when they are embedded in the implant prosthesis. Importantly, the capacitance response to forces is linear over a wide range, aiding reliability.