Proposed procedural algorithm for the cost-effective use of cadaveric torsos in the training of neurosurgical residents

Introduction

Educational adjuncts in the training of neurosurgical residents have become an important part of residency programme curricula due to the requirements of clinical duties and the institution of work hour restrictions.^{1 2} Cadaveric simulation is a prevalent method for teaching neurosurgical trainees basic and complex procedures.^{3 4} Cadaveric handling requires a dedicated centre for tissue storage and care, which increases institutional costs in order to support personnel and equipment for maintenance of laboratory space.^{4 5} Cadaveric tissue is relatively expensive and has limited repeated use. Because of these limiting factors, procedures that require significant disruption of the intrinsic anatomy may negate the capacity for subsequent anatomical landmarks or procedures to be demonstrated. In this manuscript, we propose a stepwise and ordered operative curriculum to provide the most efficient use of cadaveric torso specimens in the training of neurosurgical residents. This curriculum was developed at our institution and is currently in practice for trainees.

Methods

Five frozen human cadaveric torsos devoid of extremities were acquired for the purposes of neurosurgical training. Each specimen had a complete sacral, lumbar and thoracic spine. A stepwise algorithm was developed for maximal use of the cadaveric tissue based on desired procedures to be performed and the potential disruption of cadaveric anatomy required for each procedure and dissection. The curriculum was implemented on all specimens to determine if the order of procedures performed prevented encroachment on the learning objectives or relevant anatomy of subsequent procedures. The details of the proposed curriculum algorithms are outlined in figure 1.

Figure 1.

Stepwise curricular algorithm for cadaveric torso dissection and procedural instruction with instrumentation available. If instrumentation is not available, this step can be skipped.

Results

Instrumentation in the form of pedicle screws was available for this experiment. All listed surgical procedures according to the previously outlined curricular structure were successfully performed. The lumbar and thoracic dissections were performed in two sessions. During the first session, the posterior elements of the sacral and lumbar spine were completely exposed. Pedicle screw insertion was performed at S1, then L1–L5. The screws were then removed. Bilateral exposure of the nerve roots and disc space in an extraforaminal manner was performed at each level in order to simulate a far lateral diskectomy. A bilateral pars-sparing lumbar laminectomy was performed at each level of the lumbar spine. Bilateral facetectomies and transforaminal exposure of the disc space and nerve roots at each level was then performed. The lateral and anterior portions of the vertebral body at each lumbar level were then exposed, and a pedicle subtraction osteotomy was performed at each lumbar level. Tracing the skeletonised lumbar roots to the psoas and retroperitoneal space then easily exposed the lumbar plexus and facilitated an educational dissection.

During the second session, the entire thoracic spine, posterior elements, costotransverse and costovertebral joints were exposed. Bilateral pedicle screw insertion was then performed at each thoracic level, T1–T12. The screws were then removed, and a bilateral thoracic laminectomy was then performed at four consecutive levels on each specimen, T6–T9. After this was completed, the rib heads of the four levels were resected, and the extracavitary exposure of the lateral and anterior vertebral bodies was performed at T6–T9 on each specimen. Ligation of the thoracic nerve roots was performed at each exposed level. Thoracic vertebrectomies were then performed at each of the four levels. In both the lumbar and thoracic sessions, there were no barriers to completing any of the previously mentioned procedures according to our proposed curriculum.

Discussion

Cadaveric dissections and simulation have become an integral part of the training of neurosurgical residents. Our method represents the first neurosurgical spine curriculum that separates cadaveric procedures by order based on bony removal required to complete each individual procedure and the amount of disruption of the native anatomy. In the lumbar spine, pedicle screw placement does not significantly impact the trainee’s learning opportunities in a far lateral diskectomy exposure. If instrumentation is not available, this step can be skipped without downstream procedural consequence. In kind, a far lateral foraminal exposure of the lumbar nerve root does not interfere with the principles of performing a standard laminectomy. Sparing the pars and inferior facet during this procedure allows for exposure of the exiting lumbar nerve root and disc space in the same manner as a transforaminal interbody placement after facetectomy. Pedicle subtraction osteotomies can then be performed at each level if desired. The lumbar plexus can be easily identified at this point, as the psoas and retroperitoneal space have already been exposed during skeletonisation of the lateral vertebral bodies, and the lumbar roots skeletonised from the previous extraforaminal and transforaminal approaches. In regards to the proposed order of thoracic procedures, placing pedicle screws in the specimen first does not interfere with subsequent laminectomy. The remainder of the proposed procedures reflects on the separate steps of a lateral extracavitary approach to the thoracic vertebral body and may be tailored based on the individual trainees’ needs or the instructors’ goals for the session. This level of organisation in the order of procedures performed allows for maximisation of tissue use.

Conclusion

Neurosurgical training is greatly enhanced by the use of cadaveric specimens for the instruction of anatomy and operative techniques. In this manuscript, we propose the first curriculum for the cost-effective use of cadaver torsos based on an ordered and algorithmic procedural list. This curriculum is currently in practice at our institution, with metrics being generated to determine the educational benefits to participating trainees. This curriculum can be implemented at any institution that is able to support cadaveric tissue and dissections. By performing anatomical and procedural instruction in a stepwise and organised manner, the utilisation of education resources can achieve maximum efficiency and cost-effectiveness for neurosurgical training programmes.