Anatomy Session 17: Shoulder and Brachial Plexus
What are the parts of the axillary artery?
1st part is medial to pectoralis minor 2nd part is posterior (deep) to pectoralis minor 3rd part is lateral to pectoralis minor
Where does the latissimus dorsi attach? innervation?
Back region - floor of intertubercular sulcus crosses shoulder joint thoracodorsal n
What kind of joint is the Glenohumeral (shoulder) joint?
Ball & socket (most mobile joint of the body - also one of the least stable) Head of humerus and glenoid cavity of scapula Main source of stability: rotator cuff muscles and tendons
If the second part of the axillary artery was interrupted, collateral blood flow could pass from branches of the thyrocervical trunk into which artery?
Circumflex scapular One branch of the thyrocervical trunk is the suprascapular artery. This artery contributes to the scapular anastamosis with the dorsal scapular artery and the circumflex scapular artery. The circumflex scapular artery is a branch of the subscapular artery, which comes from the third part of the axillary artery. So, blood could flow from the suprascapular artery, through the scapular anastamosis, into the circumflex scapular artery, travel retrograde through the circumflex scapular artery and the subscapular artery, and reach the third part of the axillary artery. This would bypass any problems in the second part of the axillary artery.
What is the glenoid cavity?
Glenoid cavity is very shallow (accepts ~1/3rd of the humeral head)
Where does the infraspinatus attach? innervation?
Infraspinous fossa of scapula - greater tubercle of humerus' crosses shoulder joint suprascapular n
Where does the teres minor attach? innervation?
Lateral border of scapula - greater tubercle crosses shoulder joint axillary n
Where does the deltoid attach? innervation?
Lateral third of clavicle, acromion, spine of scapula - deltoid tuberosity of humerus axillary n
Where does the supraspinatus attach? innervation?
Lateral third of clavicle, acromion, spine of scapula - deltoid tuberosity of humerus suprascapular n
What are medial rotators of the arm?
Latissimus dorsi, teres major, subscapularis and pectoralis major
What is the Subacromial (subdeltoid) bursa?
Located deep to the acromion process, coraco-acromial ligament, and deltoid m. and superficial to the supraspinatus tendon and joint capsule facilitates movement of the supraspinatus tendon under the acromion process, coraco-acromial ligament, the deltoid m. It does not typically communicate with the joint capsule
Where does shoulder dislocation occur?
Most dislocations occur inferiorly (due to a weak point in the musculotendinous rotator cuff) Clinically described as: anterior (most frequent), or posterior dislocations
In a fracture of the surgical neck of the humerus, which artery may be injured?
Posterior circumflex humeral The posterior and anterior circumflex arteries wrap around the humerus near its surgical neck. A fracture to the surgical neck could damage either of these arteries or the axillary nerve. (Remember--the posterior circumflex humeral artery and the axillary nerve cross through the quadrangular space together.)
Where does the subscapularis attach? innervation?
Subscapular fossa of scapula - lesser tubercle of humerus crosses shoulder joint upper and lower subscapular nn
In a case of Erb's palsy, where roots C5 and C6 of the brachial plexus are avulsed (torn out) which muscle is paralyzed?
Supraspinatus The C5 and C6 roots make the superior trunk of the brachial plexus. So, all the muscles innervated by nerves from the superior trunk of the brachial plexus will be denervated following the avulsion. Supraspinatus is innervated by the suprascapular nerve, which comes off of the superior trunk of the brachial plexus.
An elderly patient complains of shoulder pain and has difficulty abducting his arm. Arthroscopy is done in which a dye is injected into the shoulder joint and an X-ray taken. The radiologist notes that the dye has leaked from the shoulder joint into the subacromial bursa. What tendon would need to be ruptured for this to occur?
Supraspinatus- shoulder joint is separated from the subacromial bursa by the supraspinatus tendon, which is inserting on the greater tubercle of the humerus the supraspinatus tendon is ruptured, dye injected into the shoulder joint will not just stay in the shoulder joint--instead, it will diffuse and leak into the area around the joint, including the subacromial bursa
What are the T1 C8 dermatomes?
T1 and C8 dermatomes cover the medial side of the arm, with C8 extending to the tip of the little finger
A man riding a motorcycle hit a wet spot in the road, lost control, and was thrown from his bike. He landed on the right side of his head and the tip of his shoulder, bending his head sharply to the left and stretching the right side of his neck. Subsequent neurological examination revealed that the roots of the 5th and 6th cervical nerves had been torn away from the spinal cord. Following the above injury, which of the movements of the arm at the shoulder would you expect to be totally lost?
abduction Injuries to the upper roots of the brachial plexus (C5 and C6) are the most common types of injuries--resulting in a condition known as Erb-Duchenne Palsy
After initial examination, a patient is sent to radiology. Radiographs reveal that the portion of the scapula forming the tip or point of the shoulder has been fractured. This bone is the
acromion The acromion is the part of the scapula that forms the point of the shoulder--if a patient can't raise this, that means that there is a problem with either trapezius or the accessory nerve!
What is the acromioclavicular ligament?
acromion to lateral clavicle strengthens superiorly
Which nerves are terminal branches of the posterior cord?
axillary and radial
What is the blood supply to the shoulder?
blood supply to the shoulder is comprised of several anastomosing arteries typical of high mobility joins- extensive collateral supply arteries come from subclavian and axillary
While treating the patient (in the preceding question) the doctor observes, "You were fortunate that the panel did not sever the large artery running down the medial side of your arm." The large artery referred to lies in the neurovascular compartment and supplies most everything below the elbow; this artery is the:
brachial The brachial artery runs down the medial side of the arm, near the basilic vein and the median nerve.
What is the Transverse humeral ligament?
connects the greater & lesser tubercles Forms a tunnel for the tendon of biceps brachii m., long head
In old age, the supraspinatus tendon is sometimes ruptured where it blends with the capsule of the shoulder joint. Following this kind of injury one might expect
difficulty in abducting the arm.
What is the clinical importance of the AC joint?
disruption of this joint is referred to as shoulder separation
If you have a C5, C6 injury, can you still have flexion and extension?
extension: tricpes, radial nerve- YES flexion- partially lost bc pectoralis major is not completely lost
What is the coracoacromial ligament?
forms an arch over shoulder joint region Prevents superior dislocation
Following the above injury (c5, c6 injury) there would most likely be diminished cutaneous sensation over what part of the upper limb?
he top of the shoulder and the lateral side of the arm The C5 and C6 dermatomes cover the top of the shoulder and lateral side of the arm
An elderly man complained of pain in his shoulder when he brought his forearm and hand behind his back while dressing. It was determined that the pain was caused by stretching of the lateral rotators of his arm during this motion. Which muscle was most likely involved?
infraspinatus Infraspinatus and teres minor are the two lateral rotators of the arm. These were probably the muscles that this patient had strained. Latissimus dorsi, teres major, subscapularis and pectoralis major are all important medial rotators of the arm. Supraspinatus is the muscle that initiates abduction of the arm through the first 15 degrees.
What are the 2 lateral rotators of the arm?
infraspinatus and teres minor
What is Klumpkes palsy?
injuries to the inferior parts (C8 & T1) of the brachial plexus. These types of injuries are less frequent than those of the superior parts of the brachial plexus -muscles of the hands are commonly affected (claw hand)
What is the Subtendinous bursa of the subscapularis muscle?
located between the tendon of the subscapularis muscle and the scapula protects the tendon of subscapularis as it passes across the neck of the scapula typically communicates with the cavity of the glenohumeral synovial joint through an opening in the joint capsule
What are the boundaries of the quadrangular space?
medial= long head of triceps tendon lateral= humerus superior= teres minor inferior= teres mejor
While putting metal panels on the roof of a barn, one of the panels slips out of the hands of the man on the roof. During an attempt to catch the panel, a worker below is struck by its sharp edge. The panel hits across the anterior surface of his right arm at midlength and the impact severs all of the tissue to the bone. When examined in the emergency room it is noted that the patient can only weakly flex his elbow and the lateral side of his forearm is numb. In addition to the muscles, which nerve is injured?
musculocutaneous The musculocutaneous nerve innervates biceps brachii and coracobrachialis--muscles which flex the arm. Since this man cannot flex his arm, it appears that the musculocutaneous nerve has been damaged. He had also lost sensation over the lateral part of his forearm, indicating that the lateral antebrachial cutaneous nerve has been damaged. This nerve is a branch of the musculocutaneous nerve.
What does the lateral cord give off?
musculocutaneous nerve and contributes a branch to the median nerve
What kind of joint is the AC joint?
plane joint: gliding and sliding of the scapula
What arteries wrap around the humerus near its surgical neck?
posterior and anterior circumflex arteries
A person riding a mountain bike on a rustic trail hits a rut, the fork of the bike breaks and the person is thrown into a tree, severely fracturing the upper end of his humerus. During the repair the surgeon ties off the artery traveling through the quadrangular space to stop the hemorrhage. Which artery did he ligate?
posterior circumflex humeral quadrangular space is bounded medially by the long head of the triceps tendon, laterally by the humerus, superiorly by teres minor, and inferiorly by teres major. It is traversed by the axillary nerve and the posterior humeral circumflex artery
The axillary nerve arises directly from which part of the brachial plexus?
posterior cord The axillary nerve and radial nerve are both terminal branches from the posterior cord.
What does it mean if a patient cannot lift their acromion?
problem with trapezius or accessory nerve
Due to the bleeding, the surgeon ligated (tied off) the suprascapular artery as it crossed the top of the scapula. There was no concern however, as she knew that direct collateral branches of which artery would supply the normal distribution of the suprascapular artery.
scapular circumflex The scapular circumflex artery, which is a branch of the subscapular artery, contributes to a scapular anastamosis with the suprascapular artery and the dorsal scapular artery. So, if one of these arteries needs to be ligated, the other ones will supply the scapula. The anterior and posterior circumflex humeral arteries anastomose with each other, but they do not contribute to the blood supply of the scapula. The thoracodorsal artery is another branch of the subscapular artery (just like the scapular circumflex artery). It supplies latissimus dorsi.
What is the coracoclavicular ligament?
strongest ligament of the AC joint severe shoulder separations include tear of this ligament
What muscles make up the rotator cuff?
subscapular supraspinatus infraspinatus teres minor SSIT
What branches off the 3rd part of the axillary artery?
subscapular a. -thoracodorsal a. -circumflex scapular a. anterior circumflex humeral a. posterior circumflex humeral a.
What are the 2 angles of the scapula?
superior angle, formed by the union of the superior and medial borders and an inferior angle formed by the union of the medial and lateral borders
What branches off the 1st part of the axillary artery?
superior thoracic a.
During a strenuous game of tennis a 55 year old woman complained of severe shoulder pain that forced her to quit the game. During physical examination it was found that she could not initiate abduction of her arm, but if her arm was elevated to 45 degrees from the vertical (at her side) position, she had no trouble fully abducting it. Injury to which muscle was responsible?
supraspinatus Supraspinatus is responsible for initiating abduction of the arm, while deltoid is responsible for continuing abduction of the arm past the first 15 or 20 degrees. Since this patient can abduct her arm when it is lifted to 45 degrees, deltoid seems to be intact. But, she can't initiate the motion, so you know that she has probably injured supraspinatus.
What inserts on the greater tubercle of the humerus?
supraspinatus infraspinatus teres minor SIT
What are the 4 muscles of the rotator cuff?
supraspinatus, infraspinatus, teres minor, and subscapularis SITS
What does injury to C5 C6 affect?
the suprascapular, axillary, and musculocutaneous nerves, which causes paralysis of the rotator cuff muscles, biceps, brachialis, coracobrachialis, and deltoid It also knocks out the upper and lower subscapular nerves, denervating subscapularis and teres major. It knocks out most of the lateral pectoral nerve, but the majority of pect major is innervated by medial pectoral nerve, so it is only weakened.
What branches off the 2nd part of the axillary artery?
thoraco-acromial a. (supplies pectoralis major & minor mm., deltoid m., shoulder joint) lateral thoracic a. (supplies serratus anterior m.)
Where are bursae in the shoulder?
typically located where tendons rub against bone, or ligaments, or other tendons in order to reduce friction between these structures
What does the medial cord of the brachial plexus terminate with?
ulnar nerve and a branch to the median nerve; it also gives off the medial pectoral nerve, the medial cutaneous nerve of the arm, and the medial cutaneous nerve of the forarm
What does a C5, c6 injury look like?
upper limb hangs limply, medially rotated by an unopposed latissimus and pectoralis major muscles, and pronated due to a loss of biceps basically: ADDUCTED AND MEDIALLY ROTATED
What is Erb-Duchenne palsy?
uries to the superior parts (C5 & C6) of the brachial plexus -upper limb typically presents with an adducted shoulder (deltoid affected), medially rotated arm (rotator cuff mm. and latissimus dorsi m. affected), pronated forearm (biceps brachii m. affected), and extended elbow (anterior compartment of arm affected)
