Practice Questions [Sectional Anatomy & Diagnostic Imaging]

Six P’s of Compartment Syndrome

A compartment syndrome occurs when injured tissue swells within the fascia and connective tissues inside of a limb causing an increase in the pressure within that “compartment”. Our muscles are split and divided by connective tissue. These, fibrous layers of connective tissue, known as fascia, surround our muscles and form a septum that divides the compartments.

Here is how it happens; the deep fascia that covers the muscles form an INTERMUSCULAR SEPTUM that penetrates and attaches to the bones.

In the case of the forearm, these septa will form an anterior or flexor compartment, and a posterior or extensor compartment. But besides their function it is important to understand that these compartments are in some way isolated from each other and they have their own neurovascular supply.

When damage occurs to the a muscle or muscle group within the fascial compartment, the resulting swelling and bleeding can create an increased pressure that, if left untreated, can choke off circulation, eventually leading to localized cellular hypoxia and death. The pressure within the closed fascia “compartment” becomes a tourniquet for the surrounding tissue  and distal structures supplied by the same neurovascular elements. When left unrecognized or untreated, compartment syndrome can lead to loss of limb function and even loss of the limb itself.

For our physical assessment, there are 6 P’s to consider. These six signs are often associated with compartment syndrome.

1] Pain

 

Pain is the universal symptom in compartment syndrome. While significant pain is almost always present as the pressure within the limb compartment rises, we may mistakenly attribute it solely to the injury itself. When pain seems dramatically out of proportion for the severity of the mechanism, consider the possibility of a compartment syndrome and look a little closer.

The pain typically felt with compartment syndrome is a dull, deep aching that is difficult to localize. Pain that increases upon manipulation of the muscle is also suspect for compartment syndrome.

2] Paresthesia

This is that hallmark “pins-and-needles” sensation that we feel when one of our limbs has been without adequate circulation for a period of time. If you’ve ever had a crossed leg become temporarily numb while you were sitting down and then felt a rush of pin-prick sensations as circulation returned, you’ve felt two different types of paresthesia (numbness and tingling).

Numbness isn’t typically associated with our run-of-the-mill limb injuries. It can indicate nerve damage or it might suggest a progressing compartment syndrome.

3] Pallor

Pale, shiny skin distal to the injury should raise our suspicion of compartment syndrome. Bruising may also be present.

4] Paralysis

More common in crush injuries, the total inability to move the limb distal to the injury might suggest compartment syndrome. If the limb is still intact, some movement should be possible in the distal extremity. If the limb is lifeless we should suspect significant muscle and nerve disruption and, possibly compartment syndrome.

5] Pulselessness

 

We normally associate pulelessness with the severely angulated limb or massive soft tissue damage. But the absence of a pulse distal to the extremity can be caused by any mechanism that produces a tourniquet type effect.

6] Poikilothermia

In the context of compartment syndrome it refers to the finding of differing temperatures between the affected limb and the uninjured limb. Place a hand on the painful limb just distal to the injury or the site of pain. Then place your other hand on the opposite limb in the same location. If the affected limb feels cooler than the unaffected limb, this suggests that the injured limb is unable to thermoregulate.

When treating limb injuries, compartment syndrome is definitely a possibility that you should add to your differential diagnosis bag. Acute compartment syndrome is a limb threatening issue that requires surgical intervention.  

A 15 year-old male sustained high energy injury to forearm. X-ray showed proximal comminuted ulnar fracture. Physical exam revealed severe painof the entire forearm and hand, pallor, paralysis, and lack of distal pulses. A Stryker intercompartmental device revealed increased compartment pressure.

 

Picture shows a fasciotomy [compartment release] of the flexor compartment that was indicated to release the pressure.

The definitive surgical therapy for compartment syndrome is emergent fasciotomy (compartment release), with subsequent fracture reduction or stabilization and vascular repair, if needed. The goal of decompression is restoration of muscle perfusion within 6 hours.

Identify the Structure!!!

Look closely at this picture; of course this is a delicious piece of beef. All of you might think, what's up with this guy?. Well, I could not resist to let a teaching moment go away. Look at the picture again, and bear in mind  "What could it be?", could be the psoas muscle, maybe the intercostals, aside from what it is,  you just know that all of the sudden the identification is almost impossible. Well, let's go to the point. Let's consider  a hypothetical situation. You too are dissecting, and suddenly  a structure pops up, and you ask yourself, "What could this be?" and of course, I asked this question myself. How do I cope with such a dilemma? I look for IDENTIFIERS. Identifiers are two or more structures or features that will reveal information that will help you to identify the anatomical structure in question.  Here is how this work:

1. Look at the whole pictures. Never narrow your field of vision. Philadelphia is full of horses with blinders!!!
2. Look for landmarks. Are you familiar with something in the field?
3. Is this a vessel or a nerve? From where this structure is coming from or going towards?.
4. What is posterior to it? What is in front?

I know, too many questions, but this is the way it is and you will get use to it. Try to see as many structures as possible, is all about practice.

Muscle origin and insertion are terms that describe where the muscle attaches to the bones  or connective tissues, but these are relative terms. Generally, the origin is where the muscles "originates" on the body (usually a bone, but not always) of the stationary part. The insertion in the other hand is where the muscle attaches on the bone of the moving lever across a single, or multiple, joint lines. When the muscle contracts, it pulls the insertion to the origin.

Some authors don't use the aforementioned  nomenclature, but use a slightly different one. They refer to the origin as the proximal attachment. This is generally considered the least movable part or the part that attaches closes to the midline or center of the body while the insertion is the distal attachment. This generally considered the most movable part or the part that attaches farthest from the midline or center of the body.In any event consider the following picture.

Figure 1

Figure 2

The insertions are represented by blue and the origins by red. Now, let's talk about an example- "subscapularis" and think about the previously mentioned definition [origin Vs. insertion]. Just imaging the muscle fibers, crossing laterally and inserting at the lesser tubercle of the humerus [take a quick look at Figure 1]. Picture this; subscapularis [the muscle] pulling the insertion [the lesser tubercle], toward the origin [the scapula]. The movement is an internal rotation of the glenohumeral joint. As a practice, do the same with all the muscles and have some fun!!!




Note: For practical purposes use these pictures [above] to learn the origins and insertions of interest. 

You can Do Well!!!

Okay, I know!!! gross anatomy is absolutely a lot of material, but if you follow this hints you will increase the possibilities of succeeds.

1. Relax, be positive, you can do it.
2. Read the dissector and spend quality time in the dissection room. Remember, quality!!!
3. Get the BRS Gross Anatomy [Review for the Boards] 7th ed. This is a great resource to have. Hugh-yield concepts, and practice questions.
4. See the Lecture videos. These will give you high-yield material needed to understand core concepts.
5. Ask for assistance if needed!!!

If after all these steps you have some concepts that you can't grasp, go back and read your textbook. In all honesty any textbook will have the same information.  I recommend Gray's Anatomy for Students.

Feel free to contact us!!!

lopezh@rowan.edu

CMSRU Clinical Anatomy

Dear Students,

The following suggestions will help all of you to be successful in your clinical anatomy studies:

1. Read all the dissector instructions plus your textbook before each laboratory. Plan every step to avoid and/or mitigate  damage to structures in question. Being prepared is a crucial step for success.

2. Study with your atlas at all times. The atlas is your map! Have in mind that these are diagrams based on an artist idealization of the dissection field.

3. Complete each dissection using the "Three amigos system"; one dissecting, one reading out loud [from the dissector], as well as one navigating with the atlas [the GPS]

4. As soon as you find a structure, correlate it with all others, it is all about relationships!!! use the Visible Human Dissector to visualize these relationships. Identify each structure using the axial, coronal, and sagittal plane.

5. Practice, Practice, Practice... find the structures in your cadaver and then look at these structures in other cadavers. The more you get use to it, the better chances to cope with variations. Believe me, you do not need surprised.

Have a great discovery time!!!

All the best...

H&E

Introduction to Diagnostic Imaging

X-rays (roentgen rays):

• are produced by creating a large potential difference between a filament (cathode) and a tungsten target (anode) in a vacuum.

• at ~125,000 volts (125 kV), the filament reaches a high temp.

• electrons boil off cathode and are accelerated as a beam which strikes the tungsten anode producing X-rays
• X-rays penetrate people or objects to variable degrees, depending on thickness or density, to reaching the film or detector placed on the side opposite the beam source.

• Use ionizing radiation (rays) of very short wavelength and very high energy, produced and directed as a beam in a particular direction.

• produce images as a result of their systematic attenuation – their selective removal from the beam by absorption and scatter (reflection) – as they pass through structures of various thicknesses and variable densities.
• ➢ Air causes very little attenuation – nearly all the X-rays passing through it reach the film (a plastic sheet coated w/ an emulsion of silver bromide and a little silver iodide sensitive to light and radiation, producing a chemical change causing the emulsion to turn black) or beam detector

• ➢ Bone--being much denser than air—causes nearly all the x-rays to be absorbed or reflected (scattered), so that very few reach the film/detector, leaving the emulsion/screen white.

• NOTE: “Density” is used 2 ways by radiologists discussing radiographs: physical density (just referred to – as in air vs. bone) and radiographic density, which refers to the degree of “whiteness” on the film. The effect on film is paradoxical: structures of high physical density produce less photographic density (the film is less exposed) and vice versa. The difference in radiographic densities (range from nearly pure black through a wide range of grays to nearly pure white) is referred to as radiocontrast. Structures which produce more blackening on the film (i.e., structures which cause less attenuation of the x-rays, such as air) are radiolucent; those which produce less blackening (ie, which cause more attenuation of the beam) are radiodense or radiopaque.

Radiographs are “shadow-grams”! Therefore the same principles apply:

• They are two dimensional; because of the absence of the 3rd dimension (depth):

• structures nearer the source and farther from the surface (wall or film tray) onto which the shadow is cast produces a larger but less sharp shadow than structures farther from the source and nearer to the surface onto which the shadow is cast. Thus patients are positioned with the area under study closest to the film to reduce distortion and maximize sharpness of features.

• Each radiograph presents a composite view of the tissues penetrated by the beam; thus structures overlap (are projected on top of) each other. Because of this overlapping and the absence of depth, more than one view is usually necessary to detect and localize an abnormality accurately. Whenever you are baffled (except during a gross anatomy exam), call for an additional view!

More terms and definitions:

Projection: refers to the direction in which the beam penetrates the body

• PA (posteroanterior) projection: source (X-ray tube) is posterior, film anterior; beam traverses the body posterior to anterior. This is the projection usually used for chest films if the patient is capable of standing, since it puts the heart closest to the film, making it sharper, less magnified.

• AP (anteroposterior) projection: source is anterior, film is posterior; beam traverses anterior aspect first, posterior aspect last. This is the projection used for patients that must remain supine, or for vertebrae studies, since it places vertebrae closest to film.

• View: refers to the direction from which the body or body part is viewed. By convention, both PA and AP projections are examined in an AP view, as if you were facing the patient. The view is thus often opposite the projection (normal chest studies are AP views of PA projections).

• Plain film: conventional radiology without use of enhancing contrast media; depends on the natural contrast between air, soft tissue (water), fat and bone to define structures and abnormalities (eg, chest films, skeletal studies).

• Contrast studies: Due to an absence of inherent contrast difference from surrounding tissue, contrast agents (media) are employed to enhance the contrast. This technique is applied most often to hollow, tubular structures or systems – the vast majority of contrast studies are of the G.I. tract (including the hepatobiliary tract), urinary tract and blood vessels. Most common is barium sulfate administered by mouth (swallow, antegrade) or rectum (enema, retrograde), which may be enhanced by the use of gas (“air contrast”).

Angiography is the non-specific term for any contrast study of the vascular system, and includes arteriography, venography (the venous phase of an arteriogram), cardiography, and lymphangiography (iodinated oil is injected into the lymph vessels on the dorsum of the hand or foot, and x-rays are taken of lymph nodes after a delay).


Myelography involves the injection of radiopaque dye into the subarachnoid space to examine for cord or nerve root compression.


Computerized tomography (CT scanning):

• uses X-rays to produce planar images that resemble (mostly transverse) anatomical sections. The x-ray tube and detectors (electronic x-ray sensors or receivers that replace the film tray of conventional radiography) move in an arc or circle around the body, assigning each volume element or unit (voxel) an absorption value or attenuation number (expressed in Hounsfield units). The attenuation number of each voxel in the mosaic slice is converted to a pixel of a particular gray-scale value on a television monitor screen. The picture produced is equivalent to an x-ray of an anatomical slice of the living patient: air is black, bone is white, soft tissues as a variety of gray tones. Radiologists initially referred to the transverse sections produced as “transaxial sections” since they intersect the axis of body and limbs at right angles; unfortunately, this has been shortened to “axial” sections, which is actually a contradictory term since they are perpendicular to the axes. By convention, transverse sections are viewed inferiorly, as if you were standing at the foot of the bed of a supine patient, looking toward their head

• Three-dimensional CT: 3-D CT images are created through computerized “stacking” of contiguous CT slices. No additional scanning is required. With suitable software, the 3-D model can be rotated, sliced and “dissected”

Magnetic resonance imaging (MRI):

• A noninvasive technique which does not use ionizing radiation; it has no known health hazard. Patients are placed in the bore of a powerful magnet which aligns the body’s free protons (hydrogen atoms in fat and water molecules) with the magnetic field, like a compass needle in the earth’s magnetic field. Radiowaves of a particular radiofrequency (RF) are passed through the body in a particular sequence of very short pulses, the energy of which excites the protons, and they flip out of alignment. The hydrogen atoms eventually flip back to become realigned (“relax”); as they do, they emit the radiofrequency wave they absorbed. The distribution of the emitted radiofrequency waves is mapped by computer to produce images on a monitor. A variety of techniques or algorithms (spin-echo sequences) can be applied to enhance the visualization of difference tissues and disease processes which involve altering the pattern in which the radiopulses are administered (repetition time or TR) and the signals are returned (echo time or TE). Thus MRI is in essence a display of where the body’s fat and water is and is not located. Thus various body tissues emit characteristic MR signals: well-hydrated tissues, such as fat and brain, emit strong signals (have high signal strength) and appear white; relatively dehydrated tissues (eg, compact bone) emit little or no signal and appear black; moderately hydrated tissues, such as muscle, appear in a variety of gray tones. Usually rapidly-moving blood appears black because the it has moved out of the section being imaged by the time it emits its RF signal, being replaced with blood which was not subjected to the exciting signal.

• One of the great advantages of MR over CT imaging is that MR is able to produce primary images in almost any plane. Further, greater differentiation of soft-tissue structures, such as between the gray and white matter of the CNS, is possible with MR. MR is also able to demonstrate blood vessels without the use of contrast media.

Ultrasonography (US):

• Like MR, US does not utilize ionizing radiation, and most US procedures are non-invasive. US uses the same principles as sonar: recording the attenuation of pulses of high frequency sound (ultrasonic) waves as they are reflected, slowed, or freely transmitted during their attempt to pass through the body, demonstrating especially the reflection which occurs at the interfaces between the organs, tissues and substances of the body. Among its advantages are its low cost, the relatively compact, portable nature of the machine—allowing its use in the office and in the operating room -- and especially its ability to demonstrate the body’s structure in “real time”, i.e., in motion. Through the Doppler effect, it also yields information about the flow and velocity of blood. Thus it has become especially useful in cardiology. Small transducers have been developed which enable trans-esophageal, trans-vaginal and trans-rectal US for “up close” examination of surrounding structures. Because of its non-ionizing, non-invasive nature, it is especially suited for obstetrical study of the gravid uterus, placenta and developing fetus