Intramedullary nailing is a routine orthopedic procedure used for treating fractures of femoral or tibial shafts. A critical part of this procedure involves the drilling of pilot holes in both ends of the bone for the placement of the screws that will secure the IM rod to sections of the fractured bone. This step introduces a risk of soft tissue damage because the drill bit, if not stopped in time, can transverse the bone-tissue boundary into the overlying muscle, causing unnecessary injury and prolonging healing time due to periosteum damage. In this respect, detecting the bone-tissue boundary before break-through can reduce the risks and complications associated with intramedullary nailing. Hence, in the present study, a two-wavelength diffuse reflectance spectroscopy technique was integrated into a surgical drill to optically detect bone-tissue boundary and automatically trigger the drill to stop. Furthermore, Monte-Carlo simulations were used to estimate the maximum distance from within the bone at which the bone-tissue boundary could be detected using DRS. The simulation results estimated that the detection distance, termed the “look-ahead-distance” was ∼1.5 mm for 1.3 mm source-detector fiber separation. Experimental measurements with 1.3 mm source-detector fiber separation showed that the look-ahead-distance was in the order of 250 µm in experiments with set drill rate and in the range of 1 mm in experiments where the holes were drilled by hand. Despite this difference, the automated DRS enhanced drill successfully detected the approaching bone tissue boundary when tested on samples of bovine femur and muscle tissue.

In most developed countries, orthopedic surgery represents one of the most common surgical procedures.¹ The number of patients and procedures will only increase with aging populations. Many surgical procedures have been developed successfully to treat common degenerative conditions, including total knee or hip replacement and spinal fusion, which are the most common hospital discharge procedures in the United States with about 1.5 million cases per year. Other procedures, such as partial and total shoulder replacement, partial hip replacement, kyphoplasty/vertebroplasty, and lumbar decompression, are also regularly performed by orthopedic surgeons as well as other specialists (neurosurgeons and interventional radiologists). Minimally invasive surgery (MIS) and percutaneous techniques have gradually been introduced to reduce complications and improve recovery times:^{2 – 4} examples in spinal surgery include pedicle screw placement, spinal fusion, vertebroplasty/kyphoplasty, and decompression. There has been more recent adoption in total hip arthroplasty, with renewed interest in anterior hip approaches.^{5 – 7} Other hip arthroplasty techniques have included bone resurfacing, which has been controversial with several large registries highlighting concerns over premature wear and metallosis.^8,9

This work is an overview of silicon photomultipliers (SiPMs) with a view to defining their importance for bio-photonic and clinical applications. SiPMs are benchmarked against other common photodetectors, namely, PIN diodes and avalanche photodetectors (APDs) and are compared with respect to important circuit design parameters. It will be shown that careful selection of the design bias voltage, overvoltage, gain defining components and device integration to micro-optics can allow SiPM detectors to achieve considerable sensitivity for auto-fluorescence (AF) detection and a wide dynamic range at low optical powers (~1 pW to ~4 μW). The SiPM has a manageable bias voltage (~25 V to ~30 V DC) for systems integration, and with optimised sensitivity it will enhance bio-photonic research in the area of AF to detect intraoperatively, for example, brain tumour margins.

The translation of light-based technologies into the clinic has been growing over the past decades. Biophotonics tools are starting to account for a larger proportion of next-generation diagnostic and therapeutic modalities, given that they provide information of tissue functionality and composition with minimal invasiveness. One of the major challenges in advancing biophotonics-based medical devices is transforming signals into useful information that can assist the clinicians in the treatment and diagnosis of diseases.¹ In this work, we contribute to the understanding of a potential application of an existent light-based technology for localized air volume assessment in lung tissue.

The design of mechanically clutched cranial perforators, used in craniotomy procedures, limits their performance under certain clinical conditions and can, in some cases, impose the risk of severe brain injury on patients undergoing the procedure. An additional safety mechanism could help in mitigating these risks. In this work, we examine the use of diffuse reflectance spectroscopy as a potential fallback mechanism for near real-time detection of the bone-brain boundary. Monte Carlo simulation of a two layer model with optical properties of bone and brain at 530 and 850 nm resulted in a detectable change in diffuse reflectance signal when approaching the boundary. The simulated results were used to guide the development of an experimental drill control system, which was tested on 10 sheep craniums and yielded 88.1% success rate in the detection of the approaching bone-brain boundary.

Surgical procedures involving osteotomies pose risks of breaching into critical neurovascular and musculoskeletal structures, often leading to operative morbidity or potential mortality. One related clinical situation involves total hip and knee arthroplasty (THA/TKA) where periprosthetic fracture is considered a major complication that requires revision. Studies found that 40% and 54% of primary THA and TKA patients, respectively, encountered at least one major complication, such as fracture or one minor complication, such as neurovasculature damage, or both.^1,2 Furthermore, with population ageing leading to rapidly growing incidence of primary arthroplasty, the number of revision surgeries will continue to increase substantially due to limited implant survivorship. The advanced surgical complexity and higher rates of associated complications have become a prevalent concern that remains to be improved. Within orthopedics, incidence projections of revision THA/TKA (rTHA/rTKA) to 2030 in the United States alone have indicated an increase of 43% to 70% and 78% to 182%, respectively, relative to the 50,000 rTHA and 72,000 rTKA cases in 2014. In particular, the patient group aged $>55$ years is anticipated to undergo the highest increase, suggesting that multiple revision surgeries would become necessary in the coming decades. Some common causes for rTHA include instability (28%), aseptic loosening (24%), periprosthetic fracture (18%), and prosthetic joint infection (18%).³