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Arterial Latex Injection for Medical Student Anatomical Instruction Christian Shafer, OMS-II1; Edie Sperling, PT, DPT, OCS, CMPT1,2; William Merbs, MS3

1Western University of Health Sciences COMP-Northwest, Lebanon OR2Department of Medical Anatomical Sciences, COMP-Northwest

3Western Michigan University

ABSTRACTAnatomy lab with donor patients has always been a hallmark of pre-clinical medical school education. While some medical schools choose to explore the option of virtual labs, others continue to look for ways to enhance the learning experience for students within the patient donor anatomy lab1,2,3. The purpose of this study is to explore the value of adding latex injection of human vasculature as another tool to enhance learning and perspective. Latex injection has been used by specialists and surgeons to study details of arterial trees, and this same model could add to medical student education4,5,6,7. As many of these smaller arteries are often discarded and unnoticed as students dissect larger structures, this study is of specific interest in the medical education setting. Red, laboratory grade latex was obtained and injected into the femoral, radial, and ulnar arteries. The latex was allowed three days to set and solidify. Dissection of the structures of interest was then performed and documented photographically. We found clearer visualization of larger arteries in addition to the smaller arteries, specifically those intimate with subcutaneous fat, fascia, and periosteum. Our findings suggest value in utilizing at least one donor patient injected with latex to help students appreciate the smaller and variable arteries that may not typically appear in anatomy textbooks or atlases.

OBJECTIVEInvestigate visible vascular anatomy using latex injection of specific arterial structures and consider its value in medical education.

STUDY DESIGNThis study used a frozen patient donor (cadaver) with injection of the right femoral artery, left radial artery, and left ulnar artery. Red latex injection medium in an ammonia solution was injected through a thick gauge syringe and allowed 48 hours to solidify. Careful dissection of arteries distal to the injection sites was accomplished after the solidifying time. Specific care was taken in dissecting left hand vasculature with general dissection of the right leg. Smaller arteries were elucidated and documented during dissection.

This study was also aimed at understanding the difficulty of latex injection and the possibility of its use in medical education to teach medical students or residents about details of specific vascular structures that may be too small to appreciate through a standard dissection session.

RESULTS

CONCLUSIONLatex injection of patient donor bodies can be a valuable avenue for teaching anatomy to medical students when used in conjunction with standard modes of instruction, such as the standard dissection, x-ray films, CT/MRI scans, and 3D anatomy atlases. This study revealed additional value in providing a relatively simple preparation and procedure to highlight arteries to guide students as they study vascular anatomy both generally with larger named arteries and with smaller arteries.

ACKNOWLEDGEMENTSWe would like to thank the Willed Body Program at Western University of Health Sciences COMP-NW: Michael Osborne, Thomas Schlundt, and Kelly Mack.

REFERENCES1. Estai M, Bunt S. Best teaching practices in anatomy education: A critical review. Ann Anat. 2016;208:151-157. doi:10.1016/j.aanat.2016.02.0102. Ghosh SK. Cadaveric dissection as an educational tool for anatomical sciences in the 21st century. Anat Sci Educ. 2017;10(3):286-299. doi:10.1002/ase.16493. Darras KE, Spouge R, Hatala R, et al. Integrated virtual and cadaveric dissection laboratories enhance first year medical students' anatomy experience: a pilot study. BMC Med Educ. 2019;19(1):366. Published 2019 Oct 7. doi:10.1186/s12909-019-1806-54. Doomernik DE, Kruse RR, Reijnen MM, Kozicz TL, Kooloos JG. A comparative study of vascular injection fluids in fresh-frozen and embalmed human cadaver forearms. J Anat. 2016;229(4):582-590. doi:10.1111/joa.125045. Alvernia JE, Pradilla G, Mertens P, Lanzino G, Tamargo RJ. Latex injection of cadaver heads: technical note. Neurosurgery. 2010;67(2 Suppl Operative):362-367. doi:10.1227/NEU.0b013e3181f8c2476. MacArthur FJ, McGarry GW. The arterial supply of the nasal cavity. Eur Arch Otorhinolaryngol. 2017;274(2):809-815. doi:10.1007/s00405-016-4281-17. An X, Yue B, Lee JH, Lin C, Han SH. Arterial anatomy of the gracilis muscle as determined by latex injection and glycerin transparency. Clin Anat. 2012;25(2):231-234. doi:10.1002/ca.21217

General By utilizing latex injection, arteries were clearer throughout the left hand and right lower limb.

Left Wrist and Hand The left hand latex injection required a balance between radial and ulnar arteries by tying one while injecting latex in the other. This encouraged the latex to perfuse the smaller vessels instead of following the anastomoses route away from the hand. This revealed clear dorsal digital arteries and dorsal metacarpal arteries (Fig. 1,2).

Right Lower Extremity Of note in the right lower extremity, smaller arteries were specifically highlighted: throughout subcutaneous fat, intimate with pre-tibial periosteum (Fig. 3), and running anterior to the anterior cruciate ligament (ACL) of the knee (Fig. 4).

Limitations and ConsiderationsInjection was performed on a patient donor that had been frozen for more than two years and was lightly embalmed as the specimen thawed. This may have contributed to poor latex perfusion of smaller vessels near the dermis (Fig. 5) and in other locations.

Judging the time for the latex to solidify was difficult due to the varied states of the donor patient, but longer than the 48 hours of this study would be warranted based on the resulting leaks of liquid latex and subsequent staining (Fig. 6,7).

Future investigation is warranted to compare preparations of non-embalmed to embalmed and reveal if additional structures can be seen with other injection locations.

Figure 3: Dissected view of right tibia with overlying periosteum and vasculature.

Figure 1: Dorsal surface of left hand.

Figure 4: Right knee with direct visualization of anterior cruciate ligament (ACL) and small artery overlying it

Figure 2: Dorsal surface of left hand with extensor digitorum tendon to second digit reflected.

Figure 5 (left): Dermal and subcutaneous fat border of right leg.Figure 6 (right): Dorsum of right foot with multiple latex leaks

Figure 7: Superior view of right tibial plateau showing pink tissue stained by latex

DISCUSSIONIn medical school programs where dissection is performed, using latex injections is both a way to practice injection skills and a way to illuminate the vast quantity of vessels present in tissues. For detailed regional arterial dissections, medical students could be assigned or volunteer to perform certain dissections; for example, one table group could inject and dissect the arterial supply to the hand while another could look at an IT fossa. These dissections could be viewed by all the students that use the anatomy lab. Additionally, use of latex injections could be used during specific courses, for example, into the brain would be of particular interest and value during medical student neuroscience courses. Outside of themedical school curriculum, latex arterial injections would also be potentially useful in providing residents dissection opportunities and continuing medical education to illuminate surgical anatomical variations for practicing physicians.