DISSECTION OF THE BACK AND SCAPULAR REGION

SKIN INCISIONS (Look at the following slide for reference.) In the midline make a vertical skin incision from the external occipital protuberance to the approximate level of the posterior superior iliac spines (A to B). Make a transverse incision across the iliac crest (B to C). Make transverse incisions at the level of the inferior scapular angle (D to E). Make an incision from the external occipital protuberance to the mastoid process (A to F). Make a transverse incision from the mastoid process superior to both scapulae extending to the tip of the acromion, and then extending inferiorly to midarm (F to G).

D A B F E C G

Reflect the skin flaps laterally and remove the superficial fascia.

Trapezius m. Latissimus dorsi m. Teres major m. Deltoid m. Clean the area so that you can very clearly define the borders of the latissimus dorsi, trapezius, deltoid, and teres major mm..

Trapezius m. Latissimus dorsi m. Teres major m. Deltoid m. Note the “triangle of auscultation”. The triangle of auscultation is bordered by the trapezius muscle, latissimus dorsi muscle, and the medial border of the scapula. At this location, the intercostal space between ribs 6 and 7 and is relatively free of overlying mm., making it easier for auscultation of lungs sounds with a stethoscope.

Middle trapezius muscle Upper trapezius muscle Lower trapezius muscle Note the trapezius muscle actually is made of three parts, as it attaches to the acromion and spine of the scapula.

Cut the trapezius m. near its attachment to the spinous processes, beginning at the level of T12 and proceeding superiorly to the level of the external occipital protuberance. Reflect this muscle laterally, detaching it from the spine and acromion process of the scapula.

As you reflect the trapezius m As you reflect the trapezius m., you should also observe its innervation, the spinal accessory nerve (CNXI) as well as vessels (the transverse cervical artery and veins).

Rhomboid minor m. Rhomboid major m. Levator scapula m. Supra- spinatus m. Infraspinatus m. Teres minor m. Teres major m. Further clean the area so that you can now clearly define the borders of the rhomboid major and minor, supraspinatus, infraspinatus, levator scapula and teres minor mm..

Next, cut the latissimus dorsi muscle near its origin from the thoracolumbar fascia and reflect it latetally. On the deep surface of the latissimus dorsi muscle, near its upper border, attempt to locate the thoracodorsal nerve and blood vessels which supply it.

Identify the rhomboid major and rhomboid minor muscles. Detach the rhomboid major and minor muscles from their attachments to the spinous processes of the C7 to T5 vertebrae and reflect them laterally (ONLY if you have been told to do so). Rhomboid major m. Rhomboid minor m. Finally, try to find the dorsal scapular nerve and the accompanying branches of the transverse cervical vessels that lie on the deep surfaces of the levator scapulae and rhomboid muscles.

Levator scapulae m. At this time, you should also see the levator scapulae muscle attaching to the superior aspect of the medial border of the scapula.

This is a better view of these three muscles.

you should be able to see the serratus posterior inferior m. The serratus posterior superior m. is best seen deep to the rhomboid major m., but may sometimes be seen just inferior to it. Deep to the latissimus, you should be able to see the serratus posterior inferior m.

Recall that the serratus posterior muscles are inspiratory muscles and are innervated by intercostal nerves. The serratus posterior superior arises from the inferior part of the ligamentum nuchae in the neck, and from the spinous processes of C7 and T1 to T3. It inserts into the superior border of the second or fourth or fifth ribs.

Now you need to dissect the erector spinae muscles Spinalis mm. Longissimus mm. Iliocostalis mm. Now you need to dissect the erector spinae muscles of the thoracic and lumbar region. Recall that this muscle mass is made up of three “columns” of muscles that run parallel to the spinal cord.

Spinalis mm. Longissimus mm. Iliocostalis mm.

Iliocostalis thoracis m. cervicis m. Iliocostalis lumborumm. Iliocostalis thoracis m.

Longissimus thoracis m. Longissimus capitus m. Longissimus thoracis m. Longissimus cervicis m.

Now you need to identify and dissect the dorsal aspect of the neck. Levator scapula m. Sternocleidomastoid m. Splenius capitus m. Trapezius m. Ligamentum nuchae Semispinalis capitus m.

If the trapezius m. is not already reflected, do so now so that you can clearly observe the splenius capitus and splenius cervicis mm. Splenius cervicis m. Splenius capitus m.

The dissected posterior neck should look something like this. Rhomboid minor m. Rhomboid major m. Levator scapula m. Splenius cervicis m. Splenius capitus m. Semispinalis capitus m. Serratus posterior superior m.

Now abduct the arm as much as possible.

Do NOT cut the deltoid muscle unless you are specifically told to do so. However, if this muscle is detached from the acromion process and spine of the scapula, you will be able to see the axillary nerve supplying it. You should also be able to see the posterior humeral circumflex artery.

Axillary nerve, which is a branch off the posterior cord of the brachial plexus

Posterior humeral circumflex artery that arose from the axillary artery

The posterior humeral circumflex artery is one of three main branches that arise from the third part of the axillary artery. Here we are looking at it before it reaches the deltoid muscle.

In order to reach the deltoid muscle, the axillary nerve and posterior humeral circumflex artery pass through a four-sided space, called the quadrangular space.

superior - the inferior border of teres minor m. lateral – surgical neck of humerus Quadrangular space medial – long head of triceps brachii m. inferior - the superior border of teres major m.

In this same region you can see the triangular space through which the circumflex scapular artery passes. .

superior - the inferior border of teres minor m. triangular space lateral – long head of triceps brachii m. inferior - the superior border of teres major m.

Long head of the triceps brachii muscle Teres minor muscle Teres major muscle Long head of the triceps brachii muscle Since the long head of the triceps brachii muscle (located between the teres major and teres minor muscles) attaches to the infraglenoid tubercle of the scapula, it is the only head of the triceps muscle that functions in the movement of the shoulder joint.

To best see the four muscles arising from the dorsal aspect of the scapula, you should reflect the deltoid muscle from its attachment on the spine of the scapula. However, do NOT do this unless you are specifically told to do so.

Teres major m.

Teres minor m.

Infraspinatus m.

Supraspinatus m.

Transverse scapular (suprascapular) ligament In order to identify the nerve and blood supply to supraspinatus muscle you will need to cut through the muscle. Do NOT make this cut unless you have been specifically told to do this. If you make the cut, you can then clean the vessels and nerves which lie deep to the muscle. Suprascapular nerve Transverse scapular (suprascapular) ligament Suprascapular artery

Transverse scapular (suprascapular) ligament Note that the suprascapular artery runs superior to the ligament, and the suprascapular nerve runs inferior to it. This nerve is sometimes compressed at this site which would result in significant problems with abduction due to the weakened suprasoinatus muscle. Suprascapular nerve Transverse scapular (suprascapular) ligament Suprascapular artery

If you have been told to cut the infraspinatus, cut it near its attachment along the medial border of the scapula.

Suprascapular nerve and artery Reflect the infraspinatus muscle laterally to reveal the continuation of the suprascapular nerve and artery as they pass through the scapular (greater) notch.) Suprascapular nerve and artery