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
C
E
G
Reflect the skin flaps
laterally and remove
the superficial fascia.
Clean the area so that you can very
clearly define the borders of the
latissimus dorsi, trapezius, deltoid,
and teres major mm..
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.
Lower trapezius
muscle
Middle
trapezius
muscle
Upper 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., you should also observe its
innervation, the spinal accessory nerve (CNXI) as well as vessels
(the transverse cervical artery and veins).
Rhomboid
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.
Rhomboid major m.
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 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.
Deep to the latissimus,
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.
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
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.
Longissimus
capitus m.
Now you need to identify and dissect
the dorsal aspect of the neck.
Levator
scapula m.
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
major m.
Rhomboid
minor 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
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.
lateral – long head
of triceps brachii
m.
inferior - the superior border of
teres major m.
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.
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.
Transverse
scapular
(suprascapular)
ligament
Suprascapular
nerve
Suprascapular
artery
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.
Transverse
scapular
(suprascapular)
ligament
Suprascapular
nerve
Suprascapular
artery
If you have been told to cut the infraspinatus, cut it
near its attachment along the medial border of the
scapula.
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