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A team of scientists and engineers at The Technology Partnership (TTP) have developed a smart surgical nail that promotes fracture healing and tracks how well patients are progressing through recovery. Its design fits into the movement of data-driven, personalized care.
“The nail provides real-time feedback that allows orthopedic surgeons to adjust treatments based on the status of individual patients instead of standardized protocols,” said Simon Calcutt, an electronic engineer and consultant for TTP, an independent organization that invents innovative products.
Fractures typically take four to six months to heal, but the nail was designed to measure and send data over two years to account for breaks that take longer to mend. It features sensing functionality that doesn’t impact the mechanisms of the implant. “The nail itself is made from titanium that provides strength and support as the bone heals around it,” Calcutt said. “All of the device’s sensing components are housed inside the titanium structure to avoid interactions with the body.”
Calcutt and his research team are thrilled by the smart nail’s potential. “This is an exciting time for the development of smart implantable products in orthopedics,” he said. “We have seen this technology progress with knee implants, which have started to gather real-world data that show the benefits of monitoring knee replacement patients through the recovery process. The smart nail brings the same benefits to the trauma market.”
Overcoming Design Challenges
The smart nail uses a strain sensor to accurately measure load force. Digital electronics then sample the strain sensor and transfer the data over a communication link — like the mechanism that allows for contactless payments on smartphones.
“Digital sampling on the implant means it can compensate for tolerances and temperature variations to give accurate and consistent data,” Calcutt said. “A robust error-checking communication link ensures data is transferred reliably in what is a very challenging environment.”
The nail does not run on a battery. Instead, a wireless transfer of power activates the device to take measurements and capture data. “This involves a process very similar to how smartphones are wirelessly recharged, but it is designed to work over much longer distances — up to 12 inches — and through the body, which increases the range of technical challenges,” Calcutt said.
A wireless power transfer means that the implant lifetime is not limited by battery life, so measurements can be taken for much longer than two years if required, according to Calcutt. “It also reduces the risk of patient harm, because the chemicals inside a battery can be toxic if they leach out of the hermetically sealed enclosure,” he said.
The final design of the nail is slick. Calcutt and his research team overcame several hurdles to develop it.
The first big challenge involved understanding how load transferred through the nail. The researchers needed to find a suitable location for the pocket in the titanium that houses the electronics without reducing the nail’s strength. “This required us to minimize the size of the electronics and understand the stresses within the nail structure,” Calcutt said.
The second major obstacle involved finding a way to power the electronics and communicate with the device once it was placed within the titanium enclosure, which significantly attenuates the magnetic fields that transfer power and data. “Solving this issue involved optimizing the antenna design to maximize performance and minimizing the titanium thickness to reduce the attenuation it causes — all while maintaining the required strength of the nail.”
Verification and testing of the nail’s design are also critical in the development process, according to Calcutt. “We need to test it through the full range of conditions it can experience to ensure it is reliable and robust enough to provide accurate and valuable clinical data,” he said.
Benefits Beyond Healing
Personalized monitoring and feedback could provide recovering patients with peace of mind and potentially allow them to return to work or other activities earlier than if they were following a standard prescribed recovery process, according to Calcutt.
“Smart technology gives patients ongoing information throughout their recovery process, not just when they see their surgeons after surgery,” he said. “This supports and engages patients in their care and offers reassurance during their recoveries. They might be less likely to seek follow-up treatment when they think something might be wrong.”
Embedding the technology into implants enables measurements of primary physiological parameters — such as load on the implant — that are otherwise not accessible and relate directly to the quality of recovery, Calcutt said.
The smart surgical nail allows surgeons to track healing progress after they have left their immediate care, allowing for real-time correction when patients are not on an ideal recovery path. It also could enable surgeons to spot potential complications and intervene before they become major issues.
“Earlier identification of problems can enable a wider set of treatment options, such as physiotherapy, and can reduce the risk of further surgery,” Calcutt said. “It could also reduce follow-up visits, freeing up surgeon time and resources for the care of additional patients. This reduces the number of expensive additional interventions that may be required and minimizes the burden on the healthcare system.”
Calcutt acknowledged that the expense sensor technology adds to procedures and emphasized the need to prove its value in clinical trials, which would help unlock reimbursement codes. “Once that happens,” he said, “more orthopedic companies will bring smart devices to market.”
