Optical detection for orthopedic surgery


image: Concept of a “smart” optical drill for total hip arthroplasty.
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Credit: Fisher et al., doi 10.1117/1.JBO.27.1.010601.

Knees and hips wear out. The back and neck become unstable. Fortunately, orthopedic surgeons specialize in musculoskeletal repair. And surgeries that previously required open exposure are now performed with minimally invasive techniques. Surgical risks are reduced, as are postoperative pain and recovery time.

Orthopedic surgery is one of the most common types of surgery, especially in developed countries with an aging population. In the United States alone, spinal fusion and knee or hip replacement surgeries account for more than one million cases each year.

Imaging methods such as endoscopy, computed tomography and infrared navigation facilitate surgical planning and provide visual or spatial guidance, but the full potential of optical sensing in orthopedic surgery remains to be explored. Researchers from the Biophotonics@Tyndall group at the Tyndall National Institute (TNI) in Ireland joined co-authors from Sunnybrook Health Sciences, the University of Toronto, South Infirmary Victoria University Hospital and University College Cork, to offer a perspective on the integration of optical sensing into orthopedic surgical devices, published in the Journal of Biomedical Optics. They describe how optical detection, via spectroscopy or imaging, could address unmet clinical needs in orthopedic surgery.

There are many types of optical sensing, and their use depends on the type of information required. For example, optical coherence tomography (OCT) allows imaging of tissue microstructures, while Raman spectroscopy can report molecular signatures of tissues. Such techniques can be applied to help guide a surgical procedure, alone or in combination, at the working tip of a surgical instrument. For example, by sensing the inherent optical properties of bone and its surrounding tissues, an optically equipped surgical drill would allow discernment of bone/tissue interfaces to increase surgical precision. Surgeons would benefit from visual cues provided by the optical sensor, such as a green light to indicate when a drill is in the right bone area, or a warning light when it is approaching a limit, for example the collagen, blood, myelin or lipids. . Currently, auditory or sensory feedback provides this information.

What is needed for optical detection in a drill? Routine hip surgery involves a drill with a flexible, hollow core, which is a convenient location for fiber optics, but the glass fibers commonly used for optical sensing are not as flexible. The soft fibers could be plastic, but how long would they last in such an environment? This is just one of the many challenges that must be overcome to enable the integration of optical sensing for delicate surgical instruments.

The team envisions several scenarios in which optical sensing would increase accuracy and improve results. Reviewing recent developments in optics-based orthopedic technologies and unmet clinical needs for surgical instruments, the authors provide pragmatic guidance for innovation. Sub-millimeter precision is an optimal objective, necessary for spine surgery.

According to lead author Carl Fisher, “Any optical approach that could approximate CT guidance would be beneficial, as it would reduce CT and radiation exposure requirements.” The identification and incorporation of tissue-specific optical properties for bone and soft tissues, as well as connective and neurovascular tissues, is an important groundwork.

The horizon of opportunities and challenges is vast and inspiring for biomedical engineers. Ultimately, optical devices will improve outcomes in orthopedic surgery and could also support AI-based robotics to guide less experienced surgeons through complex techniques. Of course, before becoming routine tools, next-generation surgical devices must undergo rigorous evaluation. With sufficient investment of time and energy, technology will advance rapidly and the repair of musculoskeletal systems will increasingly benefit from advances in optical sensing.

Read the open access article by Carl Fisher et al., “Perspective on integrating optical sensing into orthopedic surgical devices“, J. Biomed. Opt. 27(1), 010601 (2022), doi 10.1117/1.JBO.27.1.010601.

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