Goodbye to Cadavers?

First, there was the cadaver. Next came anatomical models, made from wood and ivory and then from plaster, wax and eventually plastic. The computer age brought digital 3-D models.

Now, anatomy training is entering a new era – 3-D printing. Models on a computer screen, which can be customized and manipulated, are being reproduced as tangible objects that medical students can physically examine and potentially even dissect.

This latest advancement, reviewed in-depth in a recent report in Medical Science Educator, could revolutionize how medicine is taught, possibly eliminating the need for cadavers and other physical models.

“There is a lot of interest from researchers and educators at both Cleveland Clinic and Case Western Reserve University in using 3-D printed models to teach anatomy,” says co-author Ryan Klatte, Principal Research Engineer, who oversees 3-D printing at Cleveland Clinic’s Lerner Research Institute.

According to the report, “The technology has advanced tremendously over the past two decades. 3-D printed models may enable anatomy students to learn more precisely and more efficiently than any other modeling method.”

An overview of anatomical models

Human cadavers have long been the paradigm for human anatomy study. “In most cases, all the parts are there in the correct arrangement, the fine membranous and [fascial] elements are intact, and the presentation of structures (soft, hard, smooth, rough, dry, moist) is accurate,” says the report.

However, human cadavers come with financial and logistical concerns, such as storage and proper disposal. Social mores raise other issues. And sometimes cadaveric anatomy doesn’t present consistently, causing confusion for students.

Physical models resolve these issues. What may be too small to view in a cadaver – or hidden by other structures – can be studied in detail on fabricated models. Yet, detail varies, and these models often do not depict the variety of anatomical anomalies. Cost, storage, security and maintenance are other considerations.

Digital 3-D models, viewed on computers or mobile devices, reduce the need for physical models. Also, digital models can be altered (via animation or an interactive format) to depict disease progression or organ development, for example – things physical models can’t show.

With the proper expertise, instructors or other technical personnel can create digital 3-D models in a relatively short period of time, using graphics software or imaging and scanning technology (e.g., CT, MRI, 3-D laser scanners).

“Instructors can create models from specific perspectives, such as disarticulated skull bones, expanded models of the temporal bone, and pulmonary or vascular structures,” says the report. They also can custom-design organ anomalies – including diseases and defects – that may not be depicted in standard physical models.

How to touch a digital object

It’s one thing for medical students to explore custom-designed 3-D organs on a computer screen. It’s another to physically explore them on a lab bench. 3-D printing (also called “additive manufacturing”) makes that possible – while reducing the need for keeping large collections of physical models on hand.

Just as an inkjet printer reproduces a digital image with ink and paper, a 3-D printer reproduces a digital model with resin, thermoplastics, photopolymers or other materials. Detailed physical models can be output within hours.

“3-D printing builds physical objects by stacking material layer by layer,” explains Klatte. “Different materials or colors can be used, allowing the construction of complex models with hard, soft, opaque and transparent components.”

For more than teaching anatomy

In addition to customizing anatomy lessons, 3-D printed models can be used for teaching pathology and radiology, notes the report. For example, comparing CT images to their 3-D-modeled and -printed counterparts allows students to confirm findings and better understand the images’ clinical implications.

Aside from medical education, 3-D printing is gradually finding its role in patient care. Physician researchers have begun studying the use of 3-D printing in preoperative planning for liver transplantation and oral and maxillofacial surgery, for example.

Increasing the use of 3-D printing

Methods of 3-D printing vary by materials used, resolution, accuracy, long-term stability, cost, speed and more. Printers can cost hundreds of thousands of dollars, but the cost is dropping thanks to the introduction of desktop 3-D printers and innovative printing materials (such as recycled plastic bottles). Printer resolution remains a concern, however. Not surprisingly, better resolution comes from higher-cost printers.

According to the report, “The resolution of most desktop printers may be insufficient for printing a faithful replica of a structure as delicate as a sphenoid bone or an atrioventricular valve leaflet, especially if scaled to a smaller size. However, a nice articulated hand skeleton can be printed with attached musculature at these resolutions.”

In order for 3-D printing to become more widely used, costs must be reduced while resolution must continue to improve. And improvements are coming quickly, notes Klatte.

“In many fields, technology has become better, faster and cheaper. We anticipate the same trend in 3-D printing,” he says. “At some point, a patient-specific, 3-D printed model could very well become less expensive than a generic, off-the-shelf model. Instructors could potentially print one model per student, possibly in material that can be dissected. It’s not unlikely that 3-D printing will one day make cadavers obsolete.”