CORR Insights®: Using Laser Range-finding to Measure Bore Depth in Surgical Drilling of Bone
Year: 2019
Type: article
Abstract: Where Are We Now? In the current study, Demsey and colleagues [3] developed a laser range finder prototype that can be attached to an existing drill to measure the depth holes drilled in bone. The device consists of two laser displacement sensors mounted on the sides of a conventional surgical drill that measure displacement relative to a custom drill guide held against the bone surface in standard fashion. The protype calculated the distance and depth to the bone surface from the difference between the initial position and the breach of the second cortex. The device had acceptable accuracy (within 1 mm to 2 mm) and good precision (within 1 mm). The authors correctly noted that most of the internal fixation systems currently available rely on mechanical depth gauges that are essentially unchanged since the original description in 1948 [5]. Surgeons who have performed osteosynthesis procedures understand well the challenges of reproducing the drill path to insert the depth gauge, the struggles to “hook” the far cortex, especially when soft tissue constraints intervene, and the difficulty visualizing the numbers, which seem to inevitably be on the side facing opposite the surgeon. This all adds up to increased surgical time or improper implant selection, which can lead to wasted implants or complications from screws that are too short or too long. For these reasons, the work of Demsey and colleagues [3] and others [6, 7] seems important. Device manufacturers have developed drills with built-in depth measurement based on drilling force measurements or other proprietary methods [6, 7]. And while these drill systems are already available for clinical use, the user must purchase a new drill system, which may be cost-prohibitive. Demsey and colleagues [3] used laser displacement as an “add-on” measurement tool that could be applied to existing drill systems, allowing for accurate depth measurement without an additional step. Where Do We Need To Go? Despite its potential, the laser range finder studied by Demsey and colleagues [3] is still just a prototype, and so it needs to be refined in at least three areas: (1) Improving its durability (there were some lost measurements due to movement or disassembly of components), (2) enabling sterilization, and (3) providing instantaneous read-out (the range-finding data was recorded during the drilling but analyzed later to yield the actual depth measurement). Indeed, accurate depth measurement is important for implant selection and placement to avoid wasted time, wasted implants, and complications from screws that are too long [1] or loss of fixation from screws that are too short. Besides the currently available drill systems [6, 7] and the laser displacement measurement used in the current study [3], other technologies are known to differentiate tissue types and could potentially measure depth [2, 8]. For example, electrical impedance varies among tissue types and can be used to determine cortical penetration [2]. This approach has been previously used in a commercial medical device application [8], but adapting this technology to existing drill systems in a sterilizable manner may prove difficult. Another possibility could be the use of diffuse reflectance spectroscopy, which takes advantage of differing tissue spectral absorption and scattering properties to detect boundaries between tissue types. A previous study group developed a prototype that incorporated diffuse reflectance spectroscopy into a specialized drill bit to detect bone/tissue boundaries with promising results [4]. Still, while incorporating this technology into the drill bit may improve compatibility, it could also lead to increased costs associated with single-use items. It would be desirable to have a system that could be used with existing drill systems similar to what was done in the current study [3]. Such an “add-on” depth measurement device would ideally need to meet the following criteria: (1) Compatible or adaptable to many or most currently in-use drill systems; (2) easy to assemble; (3) capable of real time measurements without an added step; (4) accurate to within the increments of implant availability (currently 1 mm to 2 mm); (5) sterilizable or suitable for a sterile cover; (6) durable; and (7) reasonable cost. How Do We Get There? The authors of the current study have developed a prototype that currently meets two of the above criteria: Compatible or adaptable and reasonably accurate. The authors have speculated in their discussion that the prototype could be refined relatively easily. It seems reasonable that existing technology could be used to make real-time measurements (which requires software to interpret the data), to accommodate a sterile clear plastic cover, and to make the device more durable by improving fit and attachment security. Although we do not know the costs of these potential upgrades, compared to other medical devices, the refinements would likely not require the use of expensive technology or manufacturing processes. Investing in potential upgrades to existing length determination technology is justifiable because of potential benefits of lowering complications, decreasing surgical time, and lowering costs associated with wasted implants.
Author: Shawn R. Gilbert
Institution: University of Alabama at Birmingham
Language: English
Subfield: Epidemiology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2976056727