Surgical Simulation in Spine Surgery

Spine surgery is constantly evolving due to advancements in surgical techniques, such as minimally invasive surgery, and technological improvements, such as the advent of computer-assisted and robot-assisted navigation. Such advancements, in combination with the complex anatomy of the spine and the proximity of the spine to major neurovascular structures, makes mastering the many spine surgical techniques of utmost importance.[1] Commonly used techniques such as anatomic placement of pedicle screws, if performed poorly, can have devastating consequences for patients.[2] A steep learning curve of at least 60-80 pedicle screws and 25 cases have been reported for spine surgery fellows to accurately place freehand pedicle screws in traditional open procedures.[3,4] Placing screws in a minimally invasive manner adds an additional layer of complexity and increases the learning curve.[5] The current method of spine surgical training through mentorship is effective but limited by the ever-changing nature of the field, short duration of residency and fellowship training, and workplace duty-hour restrictions.[2] Surgical simulation can supplement traditional surgical training and increase efficiency and performance in the operating room while decreasing complications and errors.[1,6] Surgical simulation with the use of cadaveric models, synthetic models, and virtual and mixed reality simulators have been used in spine surgery.[1,2] Cadaveric models, especially fresh frozen cadavers, are the most realistic surgical simulation model because they most closely represent normal human tissue and haptics, as well as the normal relationships of the spine with adjacent neurovascular structures.[1,2] They can be used to create a surgical experience similar to a real operating room. A team-based cadaveric training model has been shown to increase resident confidence in their surgical ability, understanding of anatomy, and satisfaction with training.[1,7] It has also been shown to be more helpful than sawbones, web-based, or virtual-based training programs.[7] Similarly, cadaveric models have been used to teach pedicle screw placement. A study comparing accuracy of thoracic pedicle screw placement by residents demonstrated an improvement in accuracy from 44% to 58% between 2 resident cadaver training sessions that were supplemented with didactics.[8] Despite these benefits, the use of cadaveric models is limited by the high cost and availability of cadavers, the costs of maintaining a cadaver laboratory, as well as the deterioration of tissues and differences in tissue quality.[9]

Synthetic models, such as sawbones, plastic, or synthetic bone models, are an alternative to cadaveric models because of their low cost and wide availability.[1] The low cost and availability of such models, especially sawbones, is offset by the lack of realistic anatomy and soft tissues. While sawbones can be used to teach anatomy and instrumentation, the haptic feedback necessary to mimic bone is lacking in such models.[9] Improvements in synthetic technology have enabled the creation of advanced spine models with synthetic skin, muscle, dura, and cerebrospinal fluid.[10] Such models, can allow for a more realistic simulation when performing a variety of different techniques.[10]

Virtual reality simulators utilize computer software to create a 3-dimensional (3D) surgical environment. They can allow anatomy to be visualized in 3D and certain surgical techniques to be visualized and practiced without requiring cadavers or a surgical laboratory.[1,11] Unlike cadaveric and synthetic models, these simulators can be used repeatedly by multiple trainees. Whether repeated use can justify the cost of these simulators and their upkeep is still unknown. Virtual reality simulators can also be used to track a trainee’s progress and accuracy, and, depending on the program, they can be adjusted to a trainee’s level of training and ability.[11] Multiple studies have reported on the use of virtual reality simulation in spine surgery. A systematic review of 19 articles that used virtual reality simulation to teach spine techniques such as pedicle screw placement, reported that despite variability in study designs, all studies reported that participants in the stimulator group outperformed those in the non-simulator group with respect to knowledge and skill. The impact of such simulators on trainee behaviors and any correlation to patient outcomes have not been studied.[11]

Mixed and augmented reality simulators combine virtual reality with synthetic or cadaveric models to add an aspect of physical reality.[11] Such simulators allow trainees to visualize 3D anatomy and experience haptic feedback simulataneously.[10] A study of 15 orthopedic and neurosurgical trainees who were enrolled in a standardized curriculum consisting of lectures followed by two sessions on a mixed virtual reality and synthetic spine model reported improvements in resident proficiency and time with pedicle screw placement.[12] Mixed reality models can also utilize computer-assisted navigation technology to stimulate spine surgery. A simulation training study for lateral mass cervical screw placement by 15 orthopedic residents reported that the addition of 3D computer-assisted navigation to cadaver and sawbones use improved accuracy in screw placement compared to groups that utilized cadavers alone.[13] Such studies suggest that mixed reality stimulators can improve resident technical skills by combining 3D or navigation imaging with physical models.

Spine simulators can be utilized to supplement spine training in residency and fellowship programs. They can allow for various techniques and procedures to be practiced and performed in a safe environment. While many different simulators exist, ranging from synthetic and cadaveric models to mixed reality models, they all have their benefits and limitations. An ideal spine simulator would be one that is low cost, easy to use, and replicable; would be able to monitor a trainee’s progress; and would provide accurate anatomic and haptic feedback. Such a simulator would greatly augment spine training and education. n

1. Wang Z, Shen J. Simulation training in spine surgery. J Am Acad Orthop Surg. 2022;30(9):400-408.

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3. Gonzalvo A, Fitt G, Liew S, et al. The learning curve of pedicle screw placement: how many screws are enough? Spine (Phila Pa 1976). 2009;34(21):E761-765.

4. Gang C, Haibo L, Fancai L, Weishan C, Qixin C. Learning curve of thoracic pedicle screw placement using the free-hand technique in scoliosis: how many screws needed for an apprentice? Eur Spine J. 2012;21(6):1151-1156.

5. Sharif S, Afsar A. Learning curve and minimally invasive spine surgery. World Neurosurg. 2018;119:472-478.

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7. Calio BP, Kepler CK, Koerner JD, Rihn JA, Millhouse P, Radcliff KE. Outcome of a resident spine surgical skills training program. Clin Spine Surg. 2017;30(8):E1126-E1129.

8. Tortolani PJ, Moatz BW, Parks BG, Cunningham BW, Sefter J, Kretzer RM. Cadaver training module for teaching thoracic pedicle screw placement to residents. Orthopedics . 2013;36(9):e1128-1133.

9. Atesok K, Mabrey JD, Jazrawi LM, Egol KA. Surgical simulation in orthopaedic skills training. J Am Acad Orthop Surg. 2012;20(7):410-422.

10. Coelho G, Defino HLA. The role of mixed reality simulation for surgical training in spine: phase 1 validation. Spine (Phila Pa 1976). 2018;43(22):1609-1616.

11. Pfandler M, Lazarovici M, Stefan P, Wucherer P, Weigl M. Virtual reality-based simulators for spine surgery: a systematic review. Spine J. 2017;17(9):1352-1363.

12. Gardeck AM, Pu X, Yang Q, Polly DW, Jones KE. The effect of simulation training on resident proficiency in thoracolumbar pedicle screw placement using computer-assisted navigation. J Neurosurg Spine . 2020:1-8.

13. Gottschalk MB, Yoon ST, Park DK, Rhee JM, Mitchell PM. Surgical training using three-dimensional simulation in placement of cervical lateral mass screws: a blinded randomized control trial. Spine J. 2015;15(1):168-175.