Medical Exhibits - Demonstrative Evidence Expert Blog - MediVisuals

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations,MediVisuals Incorporated

Long before science had advanced to allow imaging of the body in sectional views by computed tomography (CT) and magnetic resonance imaging (MRI), medical illustrators were illustrating the body in sectional views because these views are the best way to appreciate some anatomical relationships. 

Medical illustrators, physicians, and others who have studied anatomy are familiar with sectional views of the body and appreciate the value of these views in explaining the relationship of anatomical structures. However, accomplished and well respected jury consultants and non-medical illustrator legal graphics experts have expressed concerns that sectional views may be difficult for some jury members to understand. These individuals' opinions are valuable to those of us in the legal graphics business, and I agree with their opinions that, when other views can communicate a particular relationship message equally as well or better, sectional views should be avoided. I also believe most of these experts will agree that there are times and places in which sectional views of anatomy are the best way to appreciate some anatomical relationships. Granted, there have been times when we have been working on specific cases and experts have insisted that sectional views be absolutely and unconditionally avoided. Unfortunately, in these situations the experts were unable to suggest a more effective view to communicate the relevant anatomical relationships (at least in a way that was practical in terms of time and expense). That being the case, sometimes the sectional views were used despite the input of the experts, and at other times, the relationships of the structures had to be explained without the benefits of graphics.

A way to perhaps explain how sectional views help decision makers appreciate relevant anatomical and pathological relationships is to compare them to aerial views or photographs of the scene of a collision.  Space is defined in three planes. Only two of these planes can effectively be demonstrated in a two-dimensional rendering. For example, aerial views have long been used to help explain the positions of vehicles and structures that simply can't be appreciate from "street views". When viewing the scene of a collision from a "street view", one can appreciate vertical and horizontal distances, but not depth; distances close to and far from the viewer's perspective are very difficult to appreciate (see the below figures). By comparison, when viewing an operative site through a "surgeon's view", vertical and horizontal distances can be appreciated, but the depth of the incision and the relationships of the various structures within and around the incision are very difficult or impossible to appreciate.

The "aerial view" of the collision scene allows the viewer to appreciate distances in two geographical planes as well (distances right and left, and toward and away from the "street view," but the ability to appreciate up and down is lost). Also, the locations of relevant structures or vehicles that may have been obstructed by nearby structures (such as buildings trees, signs, or other vehicles) can now be appreciated. Similarly, a sectional view of anatomy can help decision makers appreciate depth relationships of structures. Or, a sectional view of a step in a surgical illustration can allow the viewer to appreciate the depth of the surgery as well as the additional structures that may have been injured (or at risk of injury) during the invasive procedure.  These specific depth  relationships could not be appreciated from the "surgeon's view" of the same surgery shown in the above illustration.

Exhibits developed to help explain the invasive nature of a surgery and the disruption of the soft tissues during operative procedures are critical. For that reason, sectional views are critical in aiding a testifying physician to explain these issues. For example, the exhibit panel that demonstrates an anterior cervical discectomy and fusion (ACDF) that does not include a cross-section through the neck fails to emphasize the depth of the incision and disruption of tissues (essentially all the way to the center of the neck). This depth simply cannot be appreciated in a "surgeon's view".

In order to appreciate cross-sections, orientation views that show the level and direction of the section are helpful (see below), or when time, budget, and presentation format (digital as opposed to a physical panel) allow, a short animation showing the sectional view actually coming out of the orientation view such as MediVisuals' "Scan Selector^TM" can be used.

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated

Individuals who develop new or suddenly worsening symptoms consistent with nerve root or spinal cord impingement following a traumatic event are sometimes diagnosed with “disc-osteophyte complexes”. The term “disc-osteophyte complex” generally refers to abnormal extension of intervertebral disc material that accompanies immediately adjacent osteophyte formation at the vertebral body margin (see the below figure). It is important to note (as shown in the illustrations) that the disc almost always extends further than the osteophytes into the neural foramen or spinal canal to irritate or impinge upon nerve roots or the spinal cord.

Occasionally, individuals who are evaluated shortly after a traumatic event are found to have disc-osteophyte complexes. Because a minimum of several weeks is required for osteophytes to form as a result of a traumatic event, defendant insurance companies may argue that the presence of osteophytes so soon after the traumatic event in question may prove that the plaintiff’s injuries preexisted the traumatic event. Since it is the disc pathology extending beyond the osteophytes that is the actual cause of the nerve root or spinal cord irritation and inflammation, the defense’s arguments are not valid. As shown in the illustrations below, the sequence of events that typically takes place in these cases is that the plaintiff had minimally symptomatic or asymptomatic disc osteophytes prior to the traumatic event in question. During the traumatic event, the disc sustains trauma that results in worsening of the disc pathology while the osteophyte portion of the osteophyte/disc complex remains essentially unchanged. This worsening of the disc pathology in turn results in new or increased irritation or impingement of the neural elements.

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated

It is difficult to appreciate the subtle differences between the various types or severities of intervertebral disc injuries that result in them being defined as bulges, herniations, protrusions, extrusions, etc.  The way disc pathology is defined may even vary from physician to physician—perhaps primarily due to the fact that, prior to 1995, many physicians’ professional societies used different criteria to define the various classifications of disc injuries.  In 1995, a joint undertaking by representatives from the North American Spine Society, the American Society of Spine Radiology, and the American Society of Neuroradiology worked together to develop a more widely accepted and used system to define disc pathology as published in "Nomenclature and Classification of Lumbar Disc Pathology”.

This will be the first of three blogs dedicated to helping explain the definitions of disc pathology as recommended by the 1995 combined task force. This blog will focus on the difference between "bulges" and "herniations". Topics to be discussed in future articles are differences between a "Herniated Disc" and an "Annular Tear" and the difference between "Protrusions" and  "Extrusions".

In the image below, a normal disc is shown in comparison to the two types of intervertebral disc injuries covered in this article: "Bulges" and "Herniations". Disc "Bulges", in general, are defined by the presence of disc material beyond the normal margins around at least 50% of the disc's circumference. A "Herniation" is defined as displacement of disc material beyond the limits of the intervertebral disc space that extends less than 50% around the circumference of the disc. The displacement material can consist of the nucleus, the annulus, or parts of both. This is significant in personal injury litigation because the defense often places a great deal of emphasis on whether disc pathology is defined as a "bulge" or "herniation" when determining the severity of an injury. However, a "bulge" can actually impinge nerve roots or the spinal cord to a more severe degree than a "herniation".

The next image compares the normal disc to two different types of disc "Bulges". A "Bulge" is defined as "Symmetrical" when the right and left sides of the herniation more or less mirror each other.  A bulge is "Asymmetrical" when the bulge is more severe on one side when compared to the other.

Finally, the below image shows a normal disc as compared to two types of "Herniations". A "Broad-Based" herniation is defined as disc material extending beyond its normal limits in an area between 25 and 50% of the disc's circumference.  A "Focal" herniation is one involving extension of disc material beyond its normal limits in less than 25% of its circumference.

By: Robert Shepherd, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated

In determining if a person's pain may be related to some sort of intervertebral disc pathology, a great deal of emphasis is placed upon imaging studies showing evidence of mechanical compression of a nerve root by abnormal posterior displacement of a disc (i.e. bulge, protrusion, herniation, etc.) as portrayed in the below illustration. 

In cases where clear mechanical compression of the nerve roots is not shown in imaging studies, some are quick to argue that any pain emanating from the area is either exaggerated or entirely contrived. However, a person can experience pain consistent with mechanical compression of a nerve root without having any significant disc pathology. This is because the spine is encircled with a meshwork of nerves that are much too small to be seen on CT or MRI (see the below figure). The sinuvertebral nerves surround and penetrate the intervertebral discs.

When injuries to a disc are more subtle, the sinuvertebral nerves may detect the injuries and send pain signals to the brain where they are interpreted as pain (see figure). The pain may be limited to the area of the back, or a pain perception phenomenon know as "pain referral" (confusion of the origin of pain signals by the brain) may result in the person experiencing very real pain consistent with radicular pain from mechanical nerve root compression by a severely herniated disk.

Another common cause of pain consistent with nerve root mechanical compression is chemical irritation or inflammation of the nerve root. Chemical irritation of a nerve root often results from the release of chemicals following a more subtle disc injury (see the below figure). These chemicals irritate and inflame the nerve root and surrounding tissues, resulting in the perception of pain consistent with an injury to the disc and mechanical compression of the nerve root. Even after resolution of chemical irritation and inflammation, scar tissue may develop that binds the nerve root (often undetectable on CT or MRI). This scarring can cause permanent debilitating pain that may require surgical intervention.

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated

On occasion, it is uncertain exactly which intervertebral disc may be causing a plaintiff’s pain.  Physicians may conduct a discography study prior to surgery in these cases.

This procedure involves advancing needles into the discs in question and injecting contrast material that serves two purposes:  (1) The contrast material makes it possible to better analyze the exact defects (if any) in the discs when X-rays or CTs are taken after the administration of the contrast material. (2) The contrast material also increases the pressure within the disc causing it to expand and subsequently compress the nearby nerve roots.  If     the pain corresponds to the patient’s normal pain, then that disc is determined as the     “problem disc”.

When pain is thought to be associated with irritation or inflammation of the nerve root(s) or surrounding tissues, epidural injections can be performed. As shown in the animation below, epidural injections involve administering anesthetics and steroids around the nerve root(s).  These injections can be used as a diagnostic tool as well as a treatment.

If the epidural injections are ineffective, the cause of the pain may not be related to the nerve root(s).  If the injections are effective, it confirms the nerve root(s) as the source of the pain. Repeated treatments may resolve the pain; if not, more aggressive treatments may be necessary.

Sometimes the facet joints themselves can be the source of pain. One of the terms used to refer to this condition is “facet arthropathy”.  This condition results from the breakdown of the normal, healthy joint spaces. With the breakdown of these articular surfaces, the joints become painful with each movement.

Each facet joint is supplied by a small dorsal branch of the adjacent nerve root [see illustration below].  Injections in or around the facet can again serve to determine the painful facet(s) and help resolve the pain.

If facet joint injections are unsuccessful at resolving the pain, the nerves to the facets can be destroyed by a procedure known as ablation. Ablation involves advancing a needle adjacent to the facet nerve and destroying it, thereby eliminating the pain.

By: Robert Shepherd MS, Certified Medical Illustrator, Vice President and Director of Eastern Region Operations, MediVisuals Incorporated 

Injuries to the spinal and paraspinal ligaments and muscles can result from violent side-to-side motions or by violent excessive flexion and extension. The illustration below shows the major ligaments of the neck (anterior longitudinal and interspinal ligaments) in hyperflexion and hyperextension, which can be injured grossly or microscopically.

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The series of three illustrations in the bottom right corner (which is shown in more detail below), show a close-up view of the spinal anatomy in 1.) the Normal condition, 2.) during Excessive Stretching and 3.) After Healing. In the Normal condition, one can appreciate the close relationship between the muscles, nerves and blood vessels. During Excessive Stretch, small tears occur, which causes bleeding in the muscle fibers. After Healing, scar tissue and inflammation entrap blood vessels and nerves resulting in a permanent state of compromised, painful movement.

The same is true for the lower lumbosacral spine and pelvic regions. In the illustration below, the spinal nerves and their posterior branches are seen in close approximation to the ligaments and joint capsules, which are often involved in the injury. During hyperflexion of the lumbar spine, transient bulging of the intervertebral discs can occur. 

Click to enlarge

The series of illustrations in the lower right corner of the above image, show the normal lumbosacral and pelvic muscles and tendon fibers, which insert on the bones near the associated posterior spinal nerve branches. During Excessive Stretch, a segmental artery and its branches may be involved in hemorrhaging, scarring and occlusion. After Healing, scar tissue and adhesions form, entrapping nerves and blood vessels, causing chronic pain.

In these next illustrations, muscle is shown in sequentially higher magnifications, which can be used to explain excessive stretch injuries in any area of the body.  In the Normal series, the bottom illustration depicts nerves and small body vessels intertwined in muscle with its tendinous attachment to the bone.  The middle illustration shows a magnified view of an individual muscle fiber and the top illustration depicts the relationship of the microscopic myofilaments (actin and myosin) in their normal relaxed position.

In the Excessive Stretch series, the bottom illustration shows the muscle, tendon, blood vessels and nerves as they are excessively stretched. Small hemorrhages are seen escaping from the stretched and torn blood vessels. In the middle illustration, blood is shown escaping into surrounding spaces, reducing oxygen exchange to the muscle and irritating the delicate structures of the muscle fiber. The top illustration depicts the myofilaments, showing the actin and myosin fibers torn and stretched past the point of normal interdigitation.

In the After Healing series, the bottom illustration shows the irregular outline of the scarred and inflammed muscle fiber with small adhesions seen between the blood vessels, nerves and muscle fibers. The middle illustration shows scar tissue and inflammation occluding blood vessels and adhering the delicate structures of the muscle fibers together, limiting motion and causing chronic pain. Lastly, the top illustration depicts the damaged myofilaments. Their normally well-organized, interdigitating arrangement is left destroyed, limiting muscle movement at the most basic level.