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SSN ANATOMY
Workshop 7: Upper Extremity
You’re in good hands with SSN
1. After a six months of partying like a rock star as a 4th year at P&S, you graduate and
begin your internship. You’re in the ER of St. Luke’s for your first three months. You
see is a 16 year old kid who just took a spill on his bike and is holding his shoulder in
extreme pain. You suspect a shoulder dislocation and recommend that he growl as loud
as he can and throw himself up against the nearest wall, a la Mel Gibson in the “Lethal
Weapon” series, to reduce the shoulder. (April 59)
What are the supporting ligamentous structures of the glenohumeral joint?
1. Superior, middle, inferior glenohumeral ligaments
2. Coracohumeral ligament
3. Coracoacromial ligament (“coracoacromial arch”)
What are the supporting muscular/tendinous structures of the glenohumeral joint?
1. Rotator cuff muscles (SITS muscles)
2. tendon of LONG head of biceps brachii—originates from supraglenoid tubercle
What is the most common type of dislocation, and what happens?
Anterior—the head of the humerus lies inferior to the coracoid process, sometimes
injuring the axillary nerve and avulsing the glenoid labrum. Dislocation occurs because
of the mobility of the joint, the shallowness of the glenohumeral joint, and some degree of
lack of support from the rotator cuff muscles.
Upon seeing the xray, you realize that the shoulder is indeed NOT dislocated and tell the
kid to stop throwing himself into walls. However, you now suspect a possible rotator
cuff tear. Which is the most commonly torn of the SITS muscles?
Supraspinatus
2. Then on an ortho rotation at Roosevelt, you see one of the new breed of female
boxers. She had recently been diagnosed with breast cancer and underwent a
mastectomy, and now she wants to go back to boxing, being that she’s a tough lady.
About which nerve was her surgeon particularly concerned? What happens to the patient
if this nerve is injured? From where does this nerve emerge?
Long thoracic nerve (C5, 6, 7 posterior, right off the roots BEFORE the BP) damage
paralyzes the serratus anterior, causing “winging” of the scapula. The serratus anterior,
or “boxer’s muscle,” anchors/rotates scapula against thoracic cage, aka protraction:
anterior/superior sliding of the scapula over the thorax. The arm cannot abduct further
than the horizontal with SA paralysis because it can’t rotate the scapula to raise the
glenoid cavity.
3. Sick of outpatient care and longing for the rush you get from working in the ER, you
go back. A six foot female former basketball player is brought in via ambulance after a
head-on collision on rollerblades with a significantly smaller woman. The collision
resulted in the smaller woman’s cheekbone breaking the basketball player’s clavicle
clean in half. You are assigned to the care of the basketball player while neurology is
called in to care for the other victim. (April 56-9)
What are the four joints of the shoulder?
Sternoclavicular
Acromioclavicular
Glenohumeral
“Scapulothoracic”—the subscapularis moving against the serratus anterior
What structural function does the clavicle serve?
It connects the upper limb to the body, but mainly it’s a strut that holds the upper limb
away from the trunk for maximum freedom of action.
What are your concerns regarding the healing of this patient’s clavicle?
1. Delayed union of fractures due to interruption of blood supply (branches of
subclavian artery)—more serious arterial tears can cause severe blood loss.
2. Sternocleidomastoid elevates the medial fragment while the weight of the arm pulls
down the lateral fragment. Also, the lateral fragment is pulled medially by the adductors
of the arm (specifically the lateralis dorsii and pectoralis major—they pull the shoulder
medially). Therefore, the overriding fragments SHORTEN the clavicle.
What are your neurological concerns for your patient?
The BRACHIAL PLEXUS! The medial cord possibly could have been injured, damaging
the ulnar nerve, the medial cord contribution to the median nerve, the medial pectoral
nerve, and the three subscapular nerves (upper, middle/thoracodorsal, and lower).
4. Another dopey rollerblader comes into the ER, having bit the tasty dust of the Central
Park loop while not wearing the proper protection, specifically wrist guards. He exhibits
tenderness in the snuffbox of the right wrist.
What are the names of the eight carpal bones? (April 85-87, 93)
Starting from the lateral side of the proximal of the two rows,
Scared (scaphoid)
Lovers (lunate)
Try (triquetrium)
Positions (pisiform)
That (trapezium)—note that “trapezium” is alphabetically before “trapezoid,” and
ALSO
They (trapezoid)
that the trapeziUM is closest to the THUMB.
Can’t (capitate)
Handle (hamate)
What is the “anatomical snuffbox”? What is found within the snuffbox? And where the
hell does the name come from? (April 106)
The area on the dorsolateral hand (remember the anatomical position) bounded by the
extensor pollicis brevis and abductor pollicis longus ANTERIORLY and the extensor
pollicis longus POSTERIORLY. It contains the radial artery, but more importantly the
scaphoid and trapeziUM lie in the floor of the snuffbox—the SCAPHOID is the most
frequently fractured carpal bone (by falling on the palm with the hand aBducted), with a
clinical presentation of snuffbox tenderness. I have no idea where the name comes from.
What is deQuervain’s syndrome? (April 88)
Inflammation of the tendons of the extensor pollicis brevis and abductor pollicis longus
(tendons of the FIRST compartment) causing extreme pain with thumb movement.
Also in the differential diagnosis for the source of this patient’s pain is a distal radius
fracture. Describe the possible etiology. (April 85; Moore 555)
A Colles’ fracture could also be caused by a fall onto an outstretched hand. The distal
fragment of the radius is displaced posteriorly, causing the radial and ulnar styloid
processes to be at about the same horizontal level (“dinner fork deformity”--refer them
to figure 6-94 in Moore—great picture!). The anterior angulation of the proximal
fragment can damage the median nerve and radial artery.
5. A young mother brings her child into the ER saying that he seems to have some pain
in his arm and that he’s not using it like he normally does. You note that this is a feisty
kid, and that the mom has a tendency to grab the child’s siblings by the hand and hoist
them up when they are misbehaving. What might you expect to find on examination?
(April 75)
A “pulled elbow”—the head of the radius pulls out of the annular ligament, sometimes
with a concurrent AL tear. This can often be corrected immediately by supination of the
forearm. NOTE: SUPination is a motion similar to scooping up a cup of SOUP.
6. A Columbia College frat boy comes into St. Luke’s on the Saturday morning after
Pi-ki-ki, a traditional luau on campus, always stocked with plenty of ethanol. He looks
worse for the wear, but he specifically complains of weakness in his left posterior
forearm/wrist. What do you think is going on? (April 84; Moore 578, 524)
“Saturday night palsy”—the radial nerve is compressed as it traverses the posterior
humerus, often by an intoxicated person sleeping in a bad position. Can also occur with
cructches, but the mechanism is posterior cord injury caused by improperly fitting
crutches.
Either way, the result is radial nerve damage. If the damage is in the middle of the arm,
likely with this patient, the result is wrist drop with normal function of the triceps. If the
damage is more superior, like in the posterior cord of the brachial plexus, the result is
paralysis of the triceps, anconeus, and wrist extensors.
7. What are the “arches” associated with these arteries? (April 99)
Ulnar artery superficial palmar arch
Radial artery deep palmar arch
8. Anterior forearm
There are EIGHT muscles of the anterior/flexor forearm, divided into THREE anatomical
subgroups (superficial, intermediate, deep) and perform at least one of THREE broad
functions (pronation, hand/wrist flexion, and digit flexion). (April 97)
Muscle
Function
Innervation
Pronator teres
Pronation and weak flexion Median n.
Flexor carpi radialis
Pronation and weak flexion Median n.
Palmaris longus
Wrist flexion
Median n.
Flexor carpi ulnaris
Wrist flexion
ULNAR n.
Flexor digitorum
Flexes PIP joints,
Median n.
superficialis
metacarpal joint, and wrist
Flexor digitorum profundus Flexes PIP and DIP joints,
Radial/lateral head: Median n.
MCP joint, and wrist
Ulnar head: ULNAR n.
Flexor pollicis longus
Flexes thumb, MCP joint,
Median n.
and wrist
Pronator quadratus
Pronates forearm
Median n.
Tell them to remember the general patterns: ALL of the anterior forearm is innervated
by the MEDIAN nerve, EXCEPT the flexor carpi ULNARis and the medial (on the
ULNAR side) head of the FDP.
9. Posterior forearm
There are ELEVEN muscles of the posterior/extensor forearm, divided into superficial
and deep groups anatomically, that perform at least one of THREE broad functions
(hand/wrist extension, extension of the medial four digits, and thumb). (April 91)
Muscle
Function
Innervation
Brachioradialis
Flexes forearm
RADIAL n.
Extensor carpi radialis
Extends/aBducts wrist
Radial n.
longus
Extensor carpi radialis
Extends wrist
Sup or deep br of Radial n.
brevis
Extensor digitorum
Extends MP joint, extends
Post. Inteross br of Radial n.
wrist when hand clenched
Extensor digiti minimi
Extends pinky finger!
Post. Inteross br of Radial n.
Extensor carpi ulnaris
Extends/aDducts wrist
Post. Inteross br of Radial n.
Supinator
Supinates forearm
Deep br of RADIAL n.
Abductor pollicis longus
Abducts thumb/wrist
Post. Inteross br of Radial n.
Extensor pollicis brevis
Extends thumb/abducts
Post. Inteross br of Radial n.
wrist
Extensor pollicis longus
Extends thumb/abducts
Post. Inteross br of Radial n.
wrist
Extensor indicis
Extends first finger and
Post. Inteross br of Radial n.
wrist
Again, tell them to remember the patterns: everything is innervated by the RADIAL
nerve, specifically the posterior interosseus branch except for four muscles. Note that the
brachioradialis and the supinator are included, though they don’t really work on the
hand, because of their radial innervation.
10. Alright, let’s talk about the hand for a little bit.
List the intrinsic muscles of the dorsum of the hand. (April 107)
HA! Trick question! There are none! Only extrinsic—the tendons of the extensor
digitorum, extensor digiti minimi, extensor indicis, abductor pollicis longus, extensor
pollicis longus and brevis—SIX tendons total.
What muscles acting on the thumb are innervated by the ulnar nerve? (April 114)
The deep head of the flexor pollicis brevis, and both the oblique and transverse heads of
the adductor pollicus.
What are the differences between lumbricals I/II and III/IV? And what do these muscles
do, anyway? (April 113)
I and II are unipennate and originate from the flexor digitorum profundus tendons of the
first and second digits, respectively. III and IV are bipennate. III originates from the
profundus tendons of the third and fourth digits, and IV originates from the profundus
tendons of the fourth and fifth digits. All four insert onto the sides of the extensor
aponeuroses of the digits. The lumbricals are the chief flexors of the digits at the MP
joints—they make the hand form an “L” for lumbrical! Sorry—it’s getting late.
11. We can’t avoid talking about it any longer….the brachial plexus. (April 68-71)
Label the parts of the plexus, and describe the consequences of injuries at the various
locations:
See next page for description.