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Cadaver-free Simulation Model Feasible for Improving Residents' Craniotomy Skills

Key findings

  • This six-week pilot study examined the impact and feasibility of incorporating a high-fidelity craniotomy simulator and spaced repetition learning into a neurosurgical residency program to improve anatomical knowledge and technical skills
  • Fifteen neurosurgical residents completed the study. Eight residents used a high-fidelity simulator model to perform a craniotomy, followed by serial interim skills labs, and then repeat simulated craniotomy; seven residents performed the initial and final craniotomy, but did not undergo interim skills training
  • Based on video recordings and assessment of the disposable parts of the model, external reviewers scored the craniotomy, dural opening, and microsurgical exploration on objective prespecified criteria
  • The group that had additional training sessions improved an average of 3 points per evaluation versus 0.57 points in the comparison group; both groups improved significantly in the time taken to perform the craniotomy tasks
  • Spaced repetition learning with simulation and objective performance metrics has the potential to improve surgical education. A larger, multi-institutional study will explore which specific skills improve most during the use of the simulator and the appropriate time course for an iterative training program

There's growing recognition in neurosurgery that mastering a skill requires both frequent and spaced repetition. New tools such as high-fidelity synthetic models and virtual reality have the potential to provide frequent repetition for trainees, and their uniformity should allow objective evaluation of improvement.

Faith C. Robertson, MD, MSc, a senior resident in the Department of Neurosurgery at Massachusetts General Hospital, Brian V. Nahed, MD, MSc, director of the Neurosurgery Residency Program, and colleagues developed a surgical training module that incorporates a simulator of the pterional approach. They evaluated the curriculum in a six-week pilot study.

In the Journal of Neurosurgery, the team says residents who used the simulator for spaced repetition learning demonstrated improved anatomical knowledge and technical skills according to objective criteria.


The study was divided into three phases:

Preliminary evaluation—Participants received online and printed instructions about supraorbital and pterional craniotomy. They performed the procedures using the UpSurgeOn PterionalBox (Assago, Italy), which is anatomically detailed and has a disposable skull cover to permit repeated use.

Trainees then rotated to a separate station where a proctor asked them to use a microscope, a retractor, and bayoneted forceps to identify anatomical structures on the simulator.

Participants were timed, and their work was video recorded for subsequent evaluation by one of three reviewers from outside Mass General. The removable parts of the skull and dura were also reviewed later.

Training phase—Participants received detailed written feedback about their first session. They then attended four laboratory trainings with faculty who provided demonstrations and gave feedback as the residents practiced supraorbital and pterional craniotomy. The trainings also included microscope identification of anatomical structures.

Final evaluation—Participants performed the same tasks as in the initial evaluation while being video recorded.

Fifteen neurosurgical residents at Mass General volunteered for the study. Eight comprised the intervention group and completed all phases of the study; seven served as the comparison group and did not undergo the training phase. Of note, the groups were not randomized, and there were more senior residents in the comparison group.


The reviewers assigned scores via global rating scales (GRSs) and task-specific checklists (TSCs) about craniotomy, dural opening, and microsurgical exploration. The changes between the preliminary and final evaluations were:

  • Time for dural opening—Improved by 6:05 minutes in the intervention group (P=0.07 vs. baseline) and 5:15 minutes in the comparison group (P=0.001)
  • Craniotomy GRS—Improved by 25% (P=0.02) vs. 4% (P=0.19)
  • Craniotomy TSC—84% (P=0.002) vs. 0% (P>0.99)
  • Microscopic exploration GRS—18% (P=0.003) vs. 6% (P=0.07)
  • Microscopic exploration TSC—52% (P=0.037) vs. 31% (P=0.029)

Next Steps

The researchers are designing a larger, multi-institutional study to understand which specific skills improve most during simulator use and the appropriate time course for an iterative training program.

They plan to expand to other models (e.g., spine, complex tumor) so simulation and trackable performance metrics become a core part of technical skill development for neurosurgical trainees.

Learn more about research in the Department of Neurosurgery

Find out more about the Department of Neurosurgery at Mass General


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