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

This blog is the third in a series referencing language and labels used by health professionals to describe intervertebral disc pathology as defined by a 1995 joint undertaking by representatives from the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology.  As a result of their efforts, a more uniform and widely accepted use of nomenclature to define intervertebral disc pathology was developed and published in "Nomenclature and Classification of Lumbar Disc Pathology".

The first blog in the series dealt with "Bulges" v. "Herniations", "Symmetrical" and "Asymmetrical" disc bulges and "Broad-based" v. "Focal" herniations.  The second blog addressed "Anular Tears and Fissures".  This blog addresses the use of "Protrusion" and "Extrusion" to describe intervertebral disc herniations.

"Protrusion" and "Extrusion" are essentially used to further classify types of disc herniations. The term "Protrusion" refers to a disc herniation in which the portion of disc material that is outside the normal confines of the disc space is equal to or less than its aperture where the disc material extrudes from the parent disc.   Examples of disc "Protrusions" and "Extrusions" are shown in the below images. 

The image to the left shows a disc "Protrusion".  Note how the superior and inferior dimensions of the disc material that protrudes from its normal confines (highlighted by the arrow on the left) is not as great as the area where the protruding disc material actually exits its normal confines and boundaries (represented by the arrow on the right in the image).  By comparison, the two illustrations to the right show two different disc "Extrusions".  Note how the dimensions of the protruding disc material are greater than the point where it exits its normal confines. 

It is important to appreciate that disc "Protrusions" and "Extrusions" are terms that may be used to further describe "Broad-based" or "Focal" herniations.  For example, the disc pathology referred to in the above illustration as a "Protrusion" could also be "Broad-Based," if it extends between 25 and 50% of the distance around the circumference of the vertebral body.  Similarly, the disc pathology shown in the illustrations referred to as "Extrusions" could also be referred to as "Focal" if extending less than 25% of the distance around the circumference of the vertebral body (see blog from 08/24/11 for further clarification between "Broad-based" and "Focal" herniations).

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

A traumatic event causing injury to an intervertebral disc may also cause subtle injuries to the bones around the disc. During an extreme lateral flexion injury (shown in the image below), the edges of the bone are driven together, injuring both the disc and the bone. As the bone/disc junction heals, overgrowths referred to as osteophytes may form.

Osteophytes take weeks or months to develop following a traumatic event; therefore, any osteophytes that are present soon after a traumatic event are likely pre-existing.

The osteophytes themselves may compress the neural elements as in the illustration above; however, in most situations, the osteophytes are a part of an OSTEOPHYTE/DISC COMPLEX. This is when the osteophytes and disc extend beyond their normal limits and compress the neural elements (spinal cord, nerve roots). In cases where osteophytes may have pre-existed a traumatic event, worsening of the disc bulge could occur following the trauma, resulting in new or aggravated symptoms.

Sometimes disc and ligament injuries occur on the same side as the force of impact. Other times, they occur on the opposite side. Injuries to the disc on the same side as the force are the result of stretching and tearing forces. On the opposite side, compression forces result in tears and micro fractures of the tissues and bones. (see illustration below). Osteophytes and facet hypertrophy can also form following injuries to intervertebral discs and ligaments. Injuries to the discs and ligaments result in instability and excessive motion of the joints that, in turn, results in constant trauma to the bone/disc and ligament junctions. This ongoing trauma results in overgrowth of the bones as it continually cycles through episodes of healing and reinjury.

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 

Defense counsel, in personal injury cases involving spinal disc injuries, place a great deal of importance on the large neural structures, such as the nerve roots and spinal cord, but often times fail to appreciate the significance of the many smaller nerves around the spine. As the illustration below demonstrates, the spinal canal and discs are covered with a meshwork of nerves.  In some people, these nerves can be far more sensitive than they are in others.

Direct compression of an exiting nerve root (see illustration below) is widely appreciated to cause local, as well as, radicular pain and weakness.

However, if a physician's interpretation of a plaintiff's radiology films is that the films show only a bulge that does not compress the nerve root, the problem then becomes to prove that the plaintiff’s pain and weakness are not simply "fabricated".

Discogenic pain is a very likely explanation for local and radicular back pain. The disc itself has numerous sensory nerves called the sinuvertebral nerves. (see illustration below) With an injury to and/or a breakdown of the disc, these nerve endings are also damaged and send pain impulses through the spinal nerve roots.

Another explanation for pain and weakness without direct compression is attributable to chemical irritation of the nerve root due to the breakdown of the nearby disc. This occurs because, as the disc breaks down, chemicals and inflammation irritate the nearby nerve root causing pain and weakness, just as if the nerve root were compressed. (see illustration below)

In review, pain signals from the nerve root whether due to:

- Direct Compression

- Injury to the sinuvertebral nerves

- Chemical irritation of the nerve roots

 . . . and are carried to the brain and interpreted in the same way.