What is an internervous planes?

Have you ever heard the concept "internervous plane?. This plane lies between muscles supplied by different peripheral nerves. These  planes are helpful, mainly because they can be used [along their entire length] to approach bone or joints without a risk to denervate any of the involved muscles. Virtually all the traditional extensile surgical approaches to bone   use internervous planes.  For example; an anterior [deltopectoral] surgical  approach to the shoulder   will use the deltoid muscle, innervated by the axillary nerve and  Pectoralis major, innervated by both medial and lateral pectoral nerves. In an anterior approach to the hip [Smith-Peterse], an internervous plane between the Sartorius muscle (femoral n) and the tensor fasciae latae (superior gluteal n.) is utilized.

Scar from shoulder arthroplasty due to severe arthritis. 

 

 

 

AP shoulder X-ray showing a hemiarthroplasty. Identify the bony elements for practical purposes.

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