From the invention of the magnifying glass, one of the very first medical devices, by Roger Bacon in 1250 to contemporary novels and cutting edge medical devices/procedures in robotic surgery, technology continues to play a critical role in medicine and patient care. As such, spine surgery is amongst one of the many medical specialties that adopts and employs such advancement in biomedical engineering for the benefits of lesser complication rates, reduced infection, faster recovery time and shorter hospital length of stay with newer surgical techniques and medical devices.
There remains a growing patient-centered and commercial interest for more precise surgical devices, implants and techniques in spine surgery. One such area of heavy scientific research is the optimization of the implant and hardware materials to mitigate the undesirable complication of instrumentation failure. For instance, recent data in implant surface technology has demonstrated that titanium nanotextured implant surfaces stimulate bone morphogenic protein and vascular growth factors, thus enhancing a successful physiological local bone formation compared to polyetheretherketone implants1,2.
A recent review by Slosar et al deemed a nanotextured surface technology as an emerging option for improved clinical outcomes through direct local cell interaction with implants1.
Surgeons and biomedical engineers alike have sought to extend the therapeutic functionality of surgical implants further into diagnostics with the advent of smart implants (S.I). A biomedical engineering concept that has been widely tested in other surgical specialties, S.I provides the additional benefits of personalized medicine, improved clinical outcomes, and mitigation of the undesirable complications of implant failure due to early detection of impending hardware malfunction.
S.I technology in spine surgery has been primarily based on gage-based microsensors for measuring pressure, force, strain, and displacement amongst other parameters. Implementation of S.I in the spine was first researched in 1966 by Waugh et al in Harrington rods. Many modifications and newer generations of spine S.I have since been tested in posterior fixtures to provide data on the biomechanical environment surrounding the implants. Interbody and corpectomy implants have been the recent areas of focus as they provide somewhat of an accurate insight on spinal forces by virtue of their implantation in series with the spine. Preliminary data have demonstrated that the forces of the spine are highly dynamic relative to the intensity of the subject’s activity and posture. Combined motions such as flexion and lateral rotation of the spine are associated with the greatest forces on the spine and hence implants.
Spine S.I may also hold the solution in assessing bone formation and maturation after fusion for the purposes of early detection of pseudoarthrosis and postoperative interbody load measurement. S.I have been proposed to pave the way in providing objective and real time diagnostic information on the dynamic biomechanical parameters of implants in spine to access healing and bone formation post procedure. This could serve a better alternative to traditional imaging techniques. Ferrara et al sought to address this challenge by investigating the use of pressure and load on implants as biomechanical determinants of bone healing to evaluate progression of bone formation in fusion3. Results from this study showed promising signs the possible utilization of S.I to assess fusion status in vivo.
Though S.I presents the opportunity of optimizing clinical practice, refining implant designs and mitigating post-surgical complications due to a real-time hardware assessment, the adoption of this technology as a standard of practice in spine surgery still remains in early stages despite modifications and newer introduced generations of S.I in research. As the number spinal fusion in the USA continues to increase, more research would be necessary in this field to accelerate the integration of S.I into daily surgical and clinical practice given its prospective benefits.