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Home , Axilla, Quadrangular space, Suprascapular artery, Winged scapula

Lab 3— & Skeletal—Questions 1 of 2

1. The inserts on the lateral of this 3. A 52-year-old man is brought to the emergency room after being bone's intertubercular groove: found in the park, where apparently he had lain overnight after a fall. He complains of severe pain in the left arm. A. Ulna suggests a broken that is confirmed radiologically. The pa- B. Radius tient can extend the at the , but supination appears to C. Humerus be somewhat weak; the grasp is very weak compared with the D. uninjured arm. Neurologic examination reveals an inability to extend E. the (wrist-drop). Because these findings point to apparent damage, the patient is scheduled for a surgical reduction of the frac- ture. The observation that extension at the elbow appears normal, but supination of the forearm appears weak, warrants localization of the nerve lesion to which of the following? A. of the in the axilla B. Posterior divisions of the brachial plexus C. at the distal third of the humerus D. Radial nerve in the midforearm E. Radial nerve in the vicinity of the head of the radius

2. The accompanying x-ray below shows the of 4. A 10-year-old boy is brought into your office by his an 11-year-old girl who fell off the monkey bars, extending mother. The boy is supporting his left arm at the elbow by her arm in an attempt to break her fall. The small arrows using his right hand because he thinks he has “broken his indicate the fracture area. The large arrows indicate which arm.” The 10-year-old had been playing tag and tripped of the following? over the curb and landed on the grass, catching himself A. A fracture at the anatomic of the humerus with his . Upon physical examination you note a B. The glenohumeral slight drooping of the left shoulder when unsupported, C. The joint space between the proximal humerus and the and tenderness over the midclavicular region but no pal- of the scapula pable fracture or displacement. The jugular notch appears D. The proximal humeral epiphyseal plate symmetrical. The shoulder has normal movement, but the E. What is commonly called a shoulder separation boy is unwilling to lift his hand above his head because it hurts. Otherwise, hand and arm movements are relatively normal with normal sensation. You order an AP and lat- eral x-rays of the and upper arm because you sus- pect which of the following?

2. A. Colles’ fracture B. Scaphoid fracture C. Fracture of the surgical head of the humerus D. Dislocated sternoclavicular joint E. Greenstick fracture of the clavicle

5. A 7-year-old boy falls from a tree house and is brought to the emergency department of a local hospital. On ex- amination, he has weakness in rotating his arm laterally because of an of a nerve. Which of the following conditions is most likely to cause a loss of this nerve func- tion?

A. Injury to the of the brachial plexus B. Fracture of the anatomic neck of the humerus C. Knife wound on the D. Inferior dislocation of the head of the humerus E. A tumor in the in the shoulder region

1 Lab 3—Arm & Axilla Skeletal—Answers

1. Answer C. (2) The are distinctly 3. Answer C. (7) Radial nerve at the distal third of different. The minor inserts on the coracoid process of the the humerus. The clinical signs and findings in the scapula. The major is involved with horizontal flexion of patient presented in the question indicate radial the humerus; thus, it must insert on the humerus. Re- nerve damage. The evidence that extension ( member a bench press is horizontal flexion of the humer- brachii muscle) at the elbow appeared normal while us and extension of the forearm. People who train using supination appeared weak can be used to localize the bench press have well-developed pectoralis major the lesion. The innervation to the medial and long heads of the triceps brachii, principal extensor of the (and triceps brachii) muscle. arm, arises from the radial nerve (in the axilla) as the medial muscular branches. The innervation to the lateral head, and to a smaller portion of the medial head, arises from the radial nerve as it passes along the musculospiral groove at mid-humerus.

2. Answer D. (7) The large arrows indicate the 4. Answer E. The clavicle is the most frequently proximal humeral epiphyseal plate. The young girl broken bone in body. Greenstick fractures of the was only 11 and still growing. The epiphyseal plates clavicle are extremely common in children as a re- show up on x-rays as radiolucent cartilage and sult of falling on outstretched . Colles’ fracture should not be confused with a fracture. The epiphy- is also common from falling on outstretched arms, sis is located at the anatomic neck of the humerus but there are no physical findings to support a Col- but is notdiscoid-shaped like many epiphyseal plates les’ fracture [(answer a); fracture of the distal radius, in long bones. This plate is tent-shaped, which is occasionally including the ulna] in this boy, [nor why it is not clearly visible all the way across the scaphoid fracture (answer b)]. The sternoclavicular proximal humerus. The fracture at the anatomic joint (answer d) is extremely stable and is rarely dis- neck of the humerus is marked by the small arrows located. Fracture of the surgical head of the humer- (answer a). The glenohumeral joint is more medial us (answer c) is not indicated by the physical find- (answer b). The joint space between the proximal ings. humerus and the acromion of the scapula (answer c) is more superior. The shoulder is not dislocated or separated (answer e).

5. Answer D. (1) Inferior dislocation of the head of the humerus may damage the , which arises from the posterior cord of the brachial plexus, runs through the accompanied by the pos- terior humeral circumflex vessels around the surgical neck of the humerus, and supplies the deltoid and teres minor, which are lateral rotators of the arm

2 Lab 3—Arm & Axilla Muscles; Tendons — Questions 1 of 3

1. Which of the following muscles can perform arm and 5. Which of the muscles listed below is the elbow flexion along with forearm supination? muscle involved in medial rotation of the humerus? A. brachii A. Teres minor B. brachialis B. Latissimus dorsi C. C. Biceps brachii D. coracobrachialis D. Supraspinatus E. supinator E. Subscapularis

2. Which of the following is a small muscle that originates 6. A rock climber falls on his shoulder, resulting in a chip- from the lateral epicondyle of the humerus and inserts on ping off of the lesser tubercle of the humerus. Which of the olecranon? the following structures would most likely have structural A. Biceps brachii and functional damage? B. Brachialis A. C. Brachioradialis B. D. Triceps brachii C. E. Anconeus D. E. Coracohumeral ligament

3. Only its long head is a two-joint muscle: 7. A 10-year-old boy falls off his bike, has difficulty in A. Biceps brachii moving his shoulder, and is brought to an emergency de- B. Brachialis partment. His radiogram and angiogram reveal fracture of C. Brachioradialis the surgical neck of his humerus and bleeding from the D. Triceps brachii point of the fracture. Following this accident, the boy has E. Anconeus weakness in rotating his arm laterally. Which of the follow- ing muscles are paralyzed? A. Teres major and teres minor B. Teres minor and deltoid C. Infraspinatus and deltoid D. Supraspinatus and subscapularis E. Teres minor and infraspinatus

4. This muscle supinates the forearm and originates on 8. A patient has suffered a fracture of the surgical neck of the scapula. the humerus. Which muscle is most likely to have been A. Teres minor weakened? B. Latissimus dorsi A. Deltoid C. Biceps brachii B. Supraspinatus D. Supraspinatus C. Biceps brachii E. Subscapularis D. Teres major E. Latissimus dorsi

3 Lab 3—Arm & Axilla Muscles; Tendons — Answers

1. Answer A. (12) The biceps brachii muscle attaches proxi- 5. Answer E. (2) There are three rotator cuff muscles that mally by its short head to the coracoid process of the scapula stabilize the head of the humerus in the glenoid cavity of the and by its long head to the supraglenoid tubercle. Distally it at- scapula. The subscapularis inserts on the lesser tubercle of the taches by a strong tendon to the tuberosity of the radius and by humerus and medially rotates the humerus. The supraspinatus an aponeurosis to the ulna. It thus can perform arm and elbow abducts and the infraspinatus laterally rotates the humerus. flexion along with forearm supination.

2. Answer E. (2) These requirements mean that the muscle 6. Answer C. (1) The subscapularis muscle inserts on the would need to be an extensor, which rules out the brachioradial- lesser tubercle of the humerus. The supraspinatus, infraspina- is, biceps brachii, and brachialis. The triceps brachii has a much tus, and teres minor muscles insert on the greater tubercle of larger origination. The anconeus is a small muscle, easily pal- the humerus. The coracohumeral ligament attaches to the great- pated during extension, in the gap between the lateral condyle er tubercle. and the olecranon.

3. Answer D. (2) The biceps and triceps brachii are the only 7. Answer B. (1) The lateral rotators of the arm include the two-joint muscles listed. Both heads of the biceps originate on teres minor, deltoid, and infraspinatus muscles, but the infrasp- the scapular, and the muscle inserts on the radius. The long inatus muscle is innervated by the suprascapular nerve. head of the triceps brachii originates at the infraglenoid tubercle of the scapula and inserts on the olecranon. The other two heads originate on the humerus.

4. Answer C. (2) A supinator must insert on the radius. All 8. Answer A. (6) The deltoid is innervated by the axillary but the biceps brachii insert on the humerus, so they cannot nerve, which courses near the surgical neck of the humerus. supinate the forearm. Only the biceps brachii inserts on the radi- us.

4 Lab 3—Arm & Axilla Muscles; Tendons — Questions 2 of 3

9. An 11-year-old boy falls down the stairs. A physician 12. A 24-year-old student is brought to the emergency room examines a radiograph of the boy's shoulder region. If the after being found in a ditch where he had lain overnight after structure indicated by the letter A (Image Below) is calci- being hit by a car. He complains of severe pain in the left arm fied, which of the following muscles is most likely para- and examination reveals a broken humerus. Neurological lyzed? examination reveals that the patient can extend the elbow but A. Deltoid displays inability to supinate the elbow when it is extended. The patient also has and very weak hand grasp. In B. Teres major the above patient, when the elbow is partially flexed, the pa- C. Teres minor tient can supinate the left forearm. This is due to the function D. Infraspinatus of which of the following? E. Subscapularis A. biceps brachii B. C. brachioradialis D. pronator teres E. anconeus

9. 13. A 32-year-old Caucasian woman presents with pain, stiffness, fa- tigue, and swelling of the . These symptoms have been present over the last 6 months. Over period of several visits you rule out any neuromuscular abnormalities. Laboratory work includes complete blood count to rule out infectious . Erythrocyte sedimentation rate is mildly elevated. Thyroid function studies are normal. On physical exam, you note bilateral tenderness to palpation of more than 12 points, includ- ing the upper edge of the trapezii, neck muscle insertion at the occiput, deltoids, infraspinatus, and second costochondral junction, inferior to the lateral (elbow) epicondyles, trochanters, and lower lumbar area, medial fat pads of the , and the medial and lateral insertions of the Achilles tendons reveal 12 or more tender points. What is the most likely diagno- sis? A. B. Fibromyalgia C. Gout D. Polymyalgia Rheumatica E. Reiter's syndrome

10. Fractures of the humerus in different regions have the 14. A 17-year-old boy is injured in an automobile acci- potential to damage different . What muscle inner- dent. He has a fracture of the shaft of the humerus. After vation may be compromised by a fracture of the humerus this accident, supination is still possible through contrac- at the “surgical neck”? tion of which of the following muscles? A. Subscapularis A. Supinator B. Pectoralis major B. Pronator teres C. Teres major C. Brachioradialis D. Deltoid D. Biceps brachii E. Suprascapularis E. Supraspinatus

11. A 34-year-old man is examined in the prison infirmary 15. A Caucasian man presents with edema and pain in his after sustaining a superficial stab wound to the superol- right shoulder. He tells you he plays softball every week- ateral aspect of the thoracic wall at the level of the third end and does a lot of hoeing and shoveling around his . There is little bleeding and no difficulty breathing; however, the medial border of the scapula on the injured house. The shoulder had been sore, but now it hurts to the side pulls away from the body wall when the arm is point where he tries to avoid using it. The drop-arm test is raised. In addition, the arm cannot be abducted above the negative, but the patient is unable to lift his arm up to 90 horizontal. Which of the following muscles is paralyzed? degrees without pain. What is the most likely diagnosis? A. Levator scapulae A. Bursitis B. B. Fibromyalgia C. Rhomboid major D. Serratus anterior C. Gout E. Supraspinatus D. Tears in the rotator cuff E. Tendinitis

5 Lab 3—Arm & Axilla Muscles; Tendons — Answers

9. Answer D. (1) The scapular notch transmits 12. Answer A. (12)The biceps brachii is a strong the suprascapular nerve below the superior trans- supinator of the forearm through its attachment to verse ligament, whereas the suprascapular the radial tuberosity, but it can only function when and run over the ligament. The suprascapular the elbow is partially flexed. The supinator by itself nerve supplies the supraspinatus and infraspinatus IS a weaker supinator muscle: prove it to yourself by muscles. The axillary nerve innervates the deltoid using a screwdriver with your right elbow flexed and teres minor muscles. The subscapular nerves (biceps brachii and supinator) and your right elbow innervate the teres major and subscapularis mus- extended (supinator only). The brachialis (choice B) cles. and brachioradialis (choice C) muscles are flexors of the forearm. The pronator teres (choice D), as its name indicates, pronates the forearm. The an- coneus (choice E) helps in extension of the elbow.

13. Answer B. (2) Fibromyalgia is a soft tissue, non-articular pain disorder characterized by chronic, generalized musculoskeletal aches, pains, and stiff- ness that occur primarily in muscles and their attach- ments. It is associated with specific sites of exagger- ated tenderness. Palpation of the upper edge of the trapezii, neck muscle insertion at the occiput, del- toids, infraspinatus, and second costochondral junc- tion, inferior to the lateral (elbow) epicondyles, tro- chanters, and lower lumbar area, medial fat pads of the knees, and the medial and lateral insertions of the Achilles tendons reveal 12 or more tender points.

10. Answer D. (7) The surgical neck of the humerus is 14. Answer D. (1) A lesion of the radial nerve the narrow area located just distal to the head and ana- causes of the supinator and brachioradial- tomical neck of the humerus (the area marked X in the is. The biceps brachii muscle is a flexor of the elbow radiograph for question 460). The posterior (dorsal as- and also a strong supinator; thus, supination is still pect) of the surgical neck is transversed by the axillary possible through action of the biceps brachii muscle. nerve (C5, C6; posterior/dorsal cord of the brachial plex- us) and the accompanying posterior circumflex humeral Other muscles cannot supinate the forearm. vessels. A fracture of the surgical neck may rupture the posterior circumflex humeral vessels, causing either the compression of the axillary nerve or transection of the same nerve. Injury to this nerve causes weakness (paresis) or paralysis of the deltoid and teres minor mus- cles.

11. Answer D. (4) The serratus anterior plays a 15. Answer E. (2) Tendinitis is an inflammation of major role in holding the scapula against the body the tendon tissue, or the tendon sheath wall. If paralyzed, the primary clinical sign is (tenosynovitis). The cause is often unknown. As the "winging" of the scapula, especially when raising the arm or pushing the body away from a wall. In addi- vascularity of tendons decreases with age, the inci- tion, it aids in rotation of the scapula, raising the gle- dent of Tendinitis will increase. Symptoms usually noid cavity when the arm is abducted beyond the include painful tendons on movement. Swelling can horizontal. The serratus anterior is innervated by the be seen, or just felt, on palpation. Along the tendon, , which runs very superficially on localized tenderness of variable severity is present the superolateral thoracic wall, where it is especially on palpation. prone to injury.

6 Lab 3—Arm & Axilla Nerves — Questions 1 of 10

1. A 21-year-old man injures his right arm in an automo- 5. The largest nerve (that is, innervates the most struc- bile accident. Radiographic examination reveals a fracture tures) of the brachial plexus is the of the medial epicondyle of the humerus. Which of the A. Axillary following nerves is most likely injured as a result of this B. Radial accident? C. Ulnar A. Axillary D. Musculocutaneous B. Musculocutaneous E. Median C. Radial D. Median E. Ulnar

2. A 10-year-old boy falls off his bike, has difficulty in 6. Choose the appropriate nerve that innervates the cora- moving his shoulder, and is brought to an emergency de- cobrachialis, biceps, and brachialis muscles. partment. His radiogram and angiogram reveal a fracture A. Median of the surgical neck of his humerus and bleeding from the B. Radial point of the fracture. Which of the following nerves is most C. Ulnar likely injured as a result of this accident? D. Musculocutaneous A. Musculocutaneous E. Axillary B. Axillary C. Radial D. Median E. Ulnar

3. A 31-year-old carpenter was wounded in his left arm by 7. Refer to the diagram below of the brachial plexus. a utility knife and is brought to a local emergency room. Which nerve arises from the lateral cord of the brachial He complains of numbness on the medial side of his arm. plexus? Which of the following nerves is most likely injured? A. A A. Axillary nerve B. B B. Musculocutaneous nerve C. C C. Medial brachial cutaneous nerve D. D D. Medial antebrachial cutaneous nerve E. E E. Radial nerve

4. A 24-year-old woman enjoys participating in an ama- teur karate class. While taking part in a tournament, she uses her right upper arm to block a high roundhouse kick and is injured. She develops a right wrist drop. What nerve was injured? A. Radial nerve B. C. D. Axillary nerve E. Musculocutaneous nerve

7 Lab 3—Arm & Axilla Nerves — Answers

1. Answer E. (1) The ulnar nerve runs down the medial as- 5. Answer B. (2) In terms of the number of muscles inner- pect of the arm and behind the medial epicondyle in a groove, vated, the radial nerve is the largest nerve of the brachial plex- where it is vulnerable to damage by fracture of the medial epi- us. The radial nerve innervates the triceps, brachialis, and all the condyle. Other nerves are not in contact with the medial epicon- dorsal muscles of the forearm. The axillary controls the deltoids dyle. and the teres minor, while the musculocutaneous controls the biceps brachii, coracobrachialis, and the brachialis. The median controls most of the flexor muscles of the forearm while the ul- nar controls the remaining few.

2. Answer B. (1) The axillary nerve runs posteriorly around 6. Answer D. (2) The musculocutaneous nerve is a branch the surgical neck of the humerus and is vulnerable to injury such of the lateral cord of the brachial plexus. It arises in the axilla as fracture of the surgical neck of the humerus or inferior dislo- and pierces the coracobrachialis. It descends between the bi- cation of the humerus. The other nerves listed are not in contact ceps superficially and the brachialis deeply and reaches the with the surgical neck of the humerus. lateral side of the arm. It supplies the flexors of the arm, which are the coracobrachialis, biceps, and brachialis, before continu- ing as the lateral antebrachial cutaneous nerve.

3. Answer C. (5) The medial brachial cutaneous nerve sup- 7. Answer E. (2) The musculocutaneous nerve (C5, 6, 7) plies the skin on the medial aspect of the arm. Axillary nerve arises from the lateral cord of the brachial plexus and pierces supplies the skin of the lateral side of the arm. The musculocuta- the coracobrachialis. This nerve supplies the coracobrachialis, neous nerve supplies the lateral side of the forearm as the lat- biceps and brachialis muscles then continues as the lateral an- eral antebrachial cutaneous nerve. The medial antebrachial cu- tebrachial cutaneous nerve. taneous nerve supplies the medial aspect of the forearm. The radial nerve gives off the posterior brachial and posterior an- tebrachial cutaneous nerves.

4. Answer A. (2) A radial nerve injury can cause a wrist drop. The radial nerve innervates the skin and posterior surface of the upper extremity. The radial nerve innervates the muscles of the back of arm, forearm, and hand. If the muscles of the pos- terior compartment of the forearm are paralyzed, as occurs with radial nerve damage, there will be wrist drop.

8 Lab 3—Arm & Axilla Nerves —Questions 2 of 10

8. Refer to the diagram below of the brachial plexus. 10. Refer to the diagram below of the brachial plexus. A Which nerve is regarded as the continuation of the poste- rare obstetrical brachial plexus palsy (Klumpke's palsy) rior cord and is the largest branch of the brachial plexus occurs as a result of failure to deliver the upper arm be- A. A fore the head in cases of breech delivery with extended B. B arms. Choose the most appropriate letter from the brachi- C. C al plexus diagram which best locates anatomically where D. D the described injury occurs E. E A. A B. B C. C D. D E. E

9. Refer to the diagram below of the brachial plexus. Which nerve arises from the and if injured results in numbness of the medial aspect of the forearm? A. A B. B C. C D. D E. E

9 Lab 3—Arm & Axilla Nerves — Answers

8. Answer D. (2) The radial nerve is the largest branch of the 10. Answer E. (2) The brachial plexus is formed by the brachial plexus and is the continuation of the posterior cord union of the ventral rami of the lower four cervical nerves ([C5], C5, 7, 8, [T1]). As it leaves the axilla it winds around the (C5, 6,7, 8) and the greater part of the ventral ramus of humerus, pierces the lateral intermuscular septum, descends the first thoracic nerve (T1) but, frequently receives contri- between the brachialis and the brachioradialis and at or below butions from the fourth cervical or the second thoracic the lateral epicondyle it divides into the superficial and deep branches. The radial nerve supplies the triceps, anconeus, bra- nerve or from both. Obstetrical to the brachial chioradialis, extensor carpi radialis longus, and brevis and gives plexus are of great importance. The much more frequent off the posterior brachial and posterior antebrachial cutaneous upper plexus palsy (Erb's palsy) of the fifth and sixth cer- nerves. The deep branch, which often supplies the extensor vical nerves occurs as a result of extreme lateral traction carpi radialis brevis, pierces the supinator which it supplies and on the head of the infant away from the shoulder during continues on as the posterior interosseous nerve and innervates the last phase of delivery. After such an injury, the upper the other muscles of the back of the forearm and well as the tends to lie in medial rotation or in a position referred of the hand. The superficial branch descends deep to the to as the "waiter's -tip hand". The infrequent (0.6%) lower brachioradialis and emerges in the snuffbox where it gives off its plexus palsy (Klumpke's palsy) of the eighth cervical and digital branches. first thoracic nerves ensues as a result of failure to deliver the upper arm before the head in cases of breech delivery 9. Answer B. (2) The medial antebrachial cutane- with extended arms. The forcible abduction of the arm as ous nerve (medial cutaneous nerve of the forearm) the infant is delivered puts the C8 and T1 nerve roots on arises from the medial cord of the brachial plexus. It a stretch which can result in a "claw hand" or "main en lies between the and vein, and de- griffe" deformity. scends medial to the brachial artery. Below the mid- dle of the arm it pierces the , becomes subcu- taneous and divides into anterior and ulnar branch- es. The anterior branch supplies the skin on the an- terior and medial side of the forearm and the ulnar branch supplies the skin on the medial and postero- medial aspects of the forearm.

10 Lab 3—Arm & Axilla Nerve —Questions 3 of 10

11. The musculocutaneous nerve arises from what 14. Refer to the diagram below of the brachial plex- spinal nerves? us. The most frequent obstetrical occurs at what level? A. C5-C7 B. C5-T1 A. A C. C7-T1 B. B D. C3-C5 C. C D. D E. E

12. Innervation to the rotator cuff muscle that medi- 14. ally rotates the arm is provided by which of the fol- lowing?

A. Axillary nerve B. Suprascapular nerve C. D. Upper and lower subscapular nerves

13. The radial nerve arises from what spinal nerves? 15. The musculocutaneous nerve has been dam- aged. Which of the following is likely to be impaired? A. C5-C7 B. C5-T1 A. Shoulder flexion C. C7-T1 B. Forearm flexion only D. C3-C5 C. Forearm flexion and supination D. Forearm flexion and pronation E. Forearm extension

16. A 12-year-old boy walks in; he fell out of a tree and fractured the upper portion of his humerus. Which of the following nerves are intimately related to the humerus and are most likely to be injured by such a fracture? A. Axillary and musculocutaneous B. Radial and ulnar C. Radial and axillary D. Median and musculocutaneous E. Median and ulnar

11 Lab 3—Arm & Axilla Nerve — Answers

11. Answer A. (2) The musculocutaneous arises 14. Answer A. (2) Upper brachial plexus palsy from C5-C7. The median and radial nerves arise (Erb's palsy) involves C5, C6, and sometimes C7. from C5-T1. The ulnar arises from C7-T1. The The mechanism of action is the result of extreme , which supplies the diaphragm mus- lateral traction on the head of the infant away from cle, originates from C3, 4 and 5. the shoulder during the last phase of delivery. Paral- ysis of the upper roots is the most common obstetri- cal brachial plexus injury. Complete paralysis may occur with involvement of all of the roots of the bra- chial plexus. Klumpke's paralysis, with isolated in- volvement of the distal roots (C8, T1), occurs in 0.6% of cases. Lower obstetrical brachial plexus pal- sy occurs as a result of failure to deliver the upper arm before the head in cases of breech delivery with extended arms. This forcible abduction of the arms 12. Answer D. (7) The upper and lower subscapular puts the C8 and T1 nerve roots on the stretch as the nerves. The upper and lower subscapular nerves inner- infant is delivered. vate the subscapularis muscle, which is the only muscle of the rotator cuff group that medially rotates the arm. The lower subscapular nerve also innervates the teres major muscle, which is not part of the rotator cuff group. The suprascapular nerve (answer b) innervates the suprasp- inatus and infraspinatus muscles that abduct and laterally rotate the arm, respectively. The teres minor muscle, in- nervated by the axillary nerve (answer a), also laterally rotates the arm. The thoracodorsal nerve (answer c), orig- inating from the posterior cord between the upper and lower subscapular nerves, innervates the .

13. Answer B. (2)The median and radial arise 15. Answer C. (2) The primary muscle that the from C5-T1. The musculocutaneous arises from C5- musculocutaneous nerve innervates is the biceps C7. The ulnar arises from C7-T1. There is no nerve brachii, brachialis, and the coracobrachialis. There- that arises from C3-C5. fore, the main joint to be effected is the elbow. Be- cause it innervates both the brachialis and biceps brachii, forearm flexion is affected, but supination is also affected because the biceps brachii is affected.

16. Answer C. (1) The axillary nerve passes posterior- ly around the surgical neck of the humerus, and the radial nerve lies in the radial groove of the middle of the shaft of the humerus. The ulnar nerve passes behind the medial epicondyle, and the median nerve is vulnerable to injury by supracondylar fracture of the humerus, but these nerves lie close to or in contact with the lower portion of the humerus. The musculocutaneous nerve is not in direct contact with the humerus.

12 Lab 3—Arm & Axilla Nerve —Questions 4 of 10

17. An 18-year-old boy involved in an automobile accident 21. A 53-year-old African American man involved in a mo- presents with arm that cannot abduct. His paralysis is tor vehicle accident sustains a severe mid-shaft fracture caused by damage to which of the following nerves? of the right humerus. Vitals are Temp-100.0F, BP- A. Suprascapular and axillary 120/88mm/Hg, - 118/min, and RR- 14/min. Exami- B. Thoracodorsal and upper subscapular nation reveals wrist drop and no ulnar or radial in C. Axillary and musculocutaneous the right arm. Examination reveals decreased sensation D. Radial and lower subscapular over the dorsal aspect of the lateral 3½ digits. The rest of E. Suprascapular and dorsal scapular the physical exam is otherwise unremarkable. What nerve is most likely injured given the findings in this patient? A. Musculocutaneous nerve B. Axillary nerve C. Median nerve D. Ulnar nerve E. Radial nerve

18. A 42-year-old man awakens to find his entire left arm 22. A 30-year-old lawyer was involved in a car accident in and hand numb and paralyzed. He slept sitting with his which he suffered a fracture of the humerus at the spiral arm draped over the back of a straight-backed chair at the groove. If this man had instead suffered a fracture at the armpit. What is most likely to have been injured? surgical neck of the humerus, which of the following A. Ulnar nerve nerves would MOST likely be damaged? B. Radial nerve A. radial C. Median nerve B. axillary D. Brachial plexus C. musculocutaneous E. Musculocutaneous nerve D. ulnar E. median

19. A 38-year-old homebuilder was involved in an acci- 23. A 17-year-old boy is injured in an automobile acci- dent and is unable to supinate his forearm. Which of the dent. He has a fracture of the shaft of the humerus. Which following nerves are most likely damaged? of the following nerves is most likely damaged? A. Suprascapular and axillary A. Axillary nerve B. Musculocutaneous and median B. Radial nerve C. Axillary and radial C. Musculocutaneous nerve D. Radial and musculocutaneous D. Median nerve E. Median and ulnar E. Ulnar nerve

20. A patient with a stab wound receives a laceration of 24. A 64-year-old man with a history of liver cirrhosis has the musculocutaneous nerve. Which of the following con- been examined for hepatitis A, B, and C viruses. In an ditions is most likely to have occurred? attempt to obtain a blood sample from the patient’s medi- A. Lack of sweating on the lateral side of the forearm an cubital vein, a registered nurse inadvertently procures B. Inability to extend the forearm arterial blood. During the procedure, the needle hits a C. Paralysis of brachioradialis muscle nerve medial to the artery. Which of the following nerves D. Loss of tactile sensation on the arm is most likely damaged? E. Constriction of blood vessels on the hand A. Radial B. Median C. Ulnar D. Lateral antebrachial E. Medial antebrachial

13 Lab 3—Arm & Axilla Nerve —Answers

17. Answer A. (1) The abductors of the arm are the deltoid 21. Answer E. (2) This patient has a mid-shaft fracture of the and supraspinatus muscles, which are innervated by the axillary humerus. The most likely nerve injured, given the constellation and suprascapular nerves, respectively. The thoracodorsal of findings, is the radial nerve. The presentation of wrist drop is nerve supplies the latissimus dorsi, which can adduct, extend, highly suggestive of radial nerve injury. There is also numbness and rotate the arm medially. The upper and lower subscapular and a reduction of sensation on the back surface of the forearm nerves supply the subscapularis, and the lower subscapular and hand. nerve also supplies the teres major; both of these structures can The musculocutaneous nerve provides mainly sensation to the adduct and rotate the arm medially. The musculocutaneous upper arm. These patients have elbow flexion weakness. nerve supplies the flexors of the arm, and the radial nerve sup- Ulnar nerve injury usually causes loss of sensation of the little plies the extensors of the arm. The sup- and usually the ulnar side of the will be im- plies the levator scapulae and rhomboid muscles; these muscles paired. elevate and adduct the scapula, respectively. Median nerve injury leads to weak pronation of the forearm, weak flexion, & radial deviation of wrist. It also leads to atrophy of the , as well as an inability to oppose or flex the . In addition, sensory loss involves the thumb and radi- al 2½ fingers.

18. Answer D. (2) This injury and its sequelae, sometimes 22. Answer B. (2) Fractures of the surgical neck of the hu- called "the Saturday Night Syndrome", are caused by the chair merus and inferior dislocations of the glenohumeral joint are two back pressing into the apex of the axilla and compressing the ways the axillary nerve is commonly damaged. Loss of ability to brachial plexus. All areas of innervation of the , motor abduct the arm due to paralysis of the will be and sensory, are affected. Although all the nerves listed are obvious with injury to the axillary nerve. An easy way to test the branches of the brachial plexus, each has its own area of motor axillary nerve is to observe cutaneous sensation over the lateral and sensory supply. Since the functions of all nerves are affect- aspect of the upper arm (e.g., using a pinprick). This is a much ed the injury must be higher than their separate origins from the better approach than asking a patient with a fractured arm and/ plexus. or dislocated shoulder to attempt to abduct his arm in order to test function of the axillary nerve.

19. Answer D. (1) The supinator and biceps brachii muscles, 23. Answer B. (1) The radial nerve runs in the radial groove which are innervated by the radial and musculocutaneous on the back of the shaft of the humerus with the profunda brachii nerves, respectively, produce supination of the forearm. This is artery. The axillary nerve passes around the surgical neck of the a question of two muscles that can supinate the forearm. humerus. The ulnar nerve passes the back of the medial epicon- dyle. The musculocutaneous and median nerves are not in con- tact with the bone, but the median nerve can be damaged by supracondylar fracture.

20. Answer A. (1) The musculocutaneous nerve contains 24. Answer B. (1) The median nerve is damaged because it sympathetic postganglionic fibers that supply sweat glands and lies medial to the brachial artery. The lies blood vessels on the lateral side of the forearm as the lateral on the brachial artery and the median nerve. The V-shaped cu- antebrachial cutaneous nerve. The musculocutaneous nerve bital fossa contains (from medial to lateral) the median nerve, does not supply the extensors of the forearm and the brachiora- brachial artery, biceps tendon, and radial nerve. The ulnar nerve dialis. This nerve also supplies tactile sensation on the lateral runs behind the medial epicondyle; the lateral and medial an- side of the forearm but not the arm and supplies blood vessels tebrachial cutaneous nerves are not closely related to the bra- on the lateral side of the forearm but not the hand. chial artery.

14 Lab 3—Arm & Axilla Nerve — Questions 5 of 10

25. Following a circus accident, a man is unable to abduct 29. Young Johnny was playing on the playground at his left arm from a 90 degree position to 180 degrees. school when he fell and struck his arm against the swing Impairment of which of the following nerves could explain set. He ran to the school nurse, complaining of which of this finding? the following conditions as a result of injuring the radial A. Axillary nerve nerve in the spiral groove of the humerus? B. Long thoracic nerve A. Numbness over the medial side of the forearm C. Musculocutaneous nerve B. Inability to oppose the thumb D. Radial nerve C. Weakness in pronating the forearm E. Thoracodorsal nerve D. Weakness in abducting the arm E. Inability to extend the hand

26. A football player is examined by the team physician 30. A 17-year-old young man comes to the ER complaining of following a shoulder injury during a game. Preliminary x- limitation of movement in his right arm. He says that he was ray films show an inferior dislocation of the humerus. On drinking last night with his friends. When he woke up this morn- further examination, there is weakness in lateral rotation ing, his was not able to move his arm, which was completely normal yesterday. His past medical history is negative. During and abduction of the arm. The nerve most likely affected Physical Exam (PE), he has difficulty extending the elbow, the is the wrist, and the digits. He also has sensory abnormalities on the A. axillary posterior part of his arm, forearm, and hand. The rest of the PE B. dorsal scapular is normal. His symptoms are suggestive of what type of injury? C. radial A. Median nerve at the elbow D. suprascapular B. Radial nerve at the axilla E. thoracodorsal C. Median nerve at the wrist D. Ulnar nerve at the elbow E. Ulnar nerve at the wrist

27. A football player experiences an anterior dislocation of 31. A 16-year-old girl is brought into your orthopedic office be- the shoulder. Cutaneous sensation over the lower half of cause she fell off her bicycle while riding down a steep hill. You the deltoid muscle is impaired. These findings suggest examine her left arm and can palpate a displaced midshaft damage to which of the following nerves? break of her humerus. You note that she can not extend her wrist, but you do not feel any distal broken bones. She has lim- A. Axillary ited ability to extend and abduct her arm at the shoulder. Her left B. Median forearm and hand feel slightly colder than her right arm and you C. Musculocutaneous note she seems to have lost some sensation on the posterior D. Radial lateral portion of her left hand, though she says she can feel E. Ulnar with all her fingertips. You are concerned that she has damaged which of the following? A. Axillary nerve B. Axillary nerve and posterior humeral circumflex artery C. Radial nerve D. Radial nerve and deep artery of the arm E. Median nerve and brachial artery

28. A young man is brought to the emergency room after 32. A 20-year-old man stated that he was unable to raise being mugged. He has been stabbed in the shoulder after his right arm. Questioning revealed that he had been in- refusing to give his wallet to his assailant. If the stab volved in a motorcycle accident, at which time he had wound lacerated the posterior humeral circumflex artery been thrown from the motorcycle and had hit his shoulder passing through the quadrangular space on the shoulder against a tree. The patient held his upper limb limply at region, which of the following nerves might be injured? his side, with the arm medially rotated and the hand pro- A. Radial nerve nated. Muscles covering the showed signifi- B. Axillary nerve cant wasting. The most likely site of the injury is the C. Thoracodorsal nerve A. lower trunk of the brachial plexus D. Suprascapular nerve B. upper trunk of the brachial plexus E. C. posterior cord of the brachial plexus D. axillary nerve E. radial nerve

15 Lab 3—Arm & Axilla Nerve — Answers

25. Answer B. (3) The long thoracic nerve innervates the 29. Answer E. (5) The radial nerve innervates the extensor , which- among its other functions- up- , hence Johnny could not extend his hand wardly rotates the scapula allowing the arms to reach a 180 because of an injury to the radial nerve. Numbness would occur degree position. The thoracodorsal nerve innervates the latissi- on the posterior aspects of the arm and forearm because of an mus dorsi, which has no function in arm abduction. The axillary injury to the radial nerve. The skin on the medial side of the fore- nerve innervates the deltoid, which abducts the arm to 90 de- arm is innervated by the medial antebrachial cutaneous nerve; grees. The radial nerve innervates the posterior muscles of the thus, numbness over the medial side of the forearm would not arm and forearm, which are not involved in arm abduction. The occur. The opponens pollicis, pronator teres, and pronator quad- musculocutaneous nerve innervates muscles of the anterior ratus muscles are innervated by the median nerve. Therefore, arm, which are not involved in arm abduction. inability to oppose the thumb or weakness in pronating the fore- arm would not occur. The abductors of the arm (deltoid and su- praspinatus muscles) are innervated by the axillary nerve and upper trunk of the brachial plexus, respectively.

26. Answer A. (4) Because of the proximity of the axillary 30. Answer B. (2) Lesion of the radial nerve at the axilla pro- nerve to the glenohumeral joint, a fracture of the surgical neck of duces loss of extension at the elbow, wrist, and digits. Limitation the humerus or an inferior dislocation of the humerus could of supination and alteration of the sensation over the posterior damage the nerve. The axillary nerve innervates the deltoid surface of the arm, forearm, and hand are also seen. The typical muscle. The deltoid abducts, adducts, flexes, extends, and ro- sign is the wrist drop. It can be caused by prolonged pressure tates the arm medially. The axillary nerve also innervates the on the floor of the axilla, for example in drunken people teres minor, which rotates the arm laterally. (Saturday night palsy).

27. Answer A. (4) The axillary nerve can be damaged during 31. Answer D. (7) Breaks of the midshaft of the humerus are anterior dislocation of the shoulder, causing loss of sensation in most likely to damage the radial nerve and deep artery of the the skin overlying the lower half of the deltoid muscle. The medi- arm (profunda brachii artery). The radial nerve (answer c) runs an nerve (choice B) supplies sensation to the anterior arm, within the radial groove on the posterior surface of the humerus palm, and distal aspects of the lateral three-and-a-half fingers. (midshaft) along with the deep artery of the arm. Because the The musculocutaneous nerve (choice C) supplies sensation to radial nerve innervates all the extensors of the arm and forearm, the lateral surface of the arm and forearm. The radial nerve the observation that the teenager suffers from wrist drop is ex- {choice D) supplies sensation to the back of the arm, forearm, pected. Normally the nerve to the posterior compartment of the and hand. The ulnar nerve (choice E) supplies sensation to the arm, the extensors of the elbow joint, will be spared in such an medial side of the arm, forearm, and hand. injury. Since the left forearm and hand felt slightly cooler than the right this suggests that the deep artery of the arm is also compromised by the displaced fracture. The axillary nerve dam- age (answers a and b) would result in reduced shoulder move- ment, which is normal. The median nerve and brachial artery (answer e), run along the medial aspect of the arm.

28. Answer B. (5) The axillary nerve runs posteriorly to the 32. Answer B. (6) The upper trunk of the brachial plexus has humerus, accompanying the posterior humeral circumflex artery been lesioned, producing a waiter's tip position of the upper through the quadrangular space and innervating the teres minor limb. Proximal musculature in the upper limb has been most and deltoid muscles. None of the other nerves pass through the affected. quadrangular space.

16 Lab 3—Arm & Axilla Nerve — Questions 6 of 10

33. A football player is examined by the team physician 37. The sensory nerve supply to the skin over the point of following a shoulder injury during a game. Preliminary x- the shoulder to halfway down the deltoid muscle is the ray films show an inferior dislocation of the humerus. On further examination, there is weakness in lateral rotation A. Upper lateral cutaneous nerve of the arm and abduction of the arm. The nerve most likely affected B. Lower lateral cutaneous nerve of the arm is the C. Supraclavicular nerves A. axillary D. Medial cutaneous nerve of arm B. dorsal scapular E. Posterior cutaneous nerve of the arm C. radial D. suprascapular E. thoracodorsal

34. A 24-year-old student is brought to the emergency room 38. A 45-year-old garbage collector has severe neck pain after being found in a ditch where he had lain overnight after and weakness in his left upper extremity. He has gotten being hit by a car. He complains of severe pain in the left arm no relief from over-the-counter medications. He denies and examination reveals a broken humerus. Neurological any history of trauma. On examination the patient is thin examination reveals that the patient can extend the elbow but and walks with his neck tilted to the left side. The patient displays inability to supinate the elbow when it is extended. The patient also has wrist drop and very weak hand grasp. The neu- has limited neck flexion and extension secondary to pain. rological lesion is likely localized at which of the following loca- The patient has a normal motor and sensory examination tions? of all extremities, with the exception of the left upper ex- A. posterior cord of the brachial plexus tremity. His left radial forearm and thumb are numb to the B. posterior divisions of the brachial plexus touch (decreased sensation to light touch). The patient C. radial nerve at the distal third of the humerus has a decreased brachioradialis reflex and slight weak- D. radial nerve at the midforearm ness of his wrist extensors. Plain radiographs appear nor- E. radial nerve at the wrist mal. Which of the following is the most likely diagnosis?

A. Compression of his left C6 nerve root B. Compression of his left thoracic first nerve root (Tl) 35. A 25-year-old man comes to the emergency room (ER) C. Compression of his right Tl nerve root 2 hours after a motorcycle accident. At physical exam (PE), D. A tumor in his lumbar spine patient has difficulty adducting and abducting the digits, E. A tumor in his sacral spine weakness for flexion of the wrist, and Froment's sign. What is the most likely injury? A. Median nerve at the elbow B. Radial nerve at the axilla C. Median nerve at the wrist D. Ulnar nerve at the elbow E. Ulnar nerve at the wrist

36. A 21-year-old patient has a lesion of the upper trunk 39. A 29-year-old man comes in with a stab wound, can- of the brachial plexus (Erb–Duchenne paralysis). Which not raise his arm above horizontal, and exhibits a condi- of the following is the most likely diagnosis? tion known as “.” Which of the following A. Paralysis of the rhomboid major structures of the brachial plexus would most likely be B. Inability to elevate the arm above the horizontal damaged? C. Arm tending to lie in medial rotation D. Loss of sensation on the medial side of the arm A. Medial cord E. Inability to adduct the thumb B. Posterior cord C. Lower trunk D. Roots E. Upper trunk

17 Lab 3—Arm & Axilla Nerve — Answers

33. Answer A. (4) Because of the proximity of the axillary nerve 37. Answer C. (2) The sensory nerve supply to the to the glenohumeral joint, a fracture of the surgical neck of the humer- skin over the point of the shoulder to halfway down the us or an inferior dislocation of the humerus could damage the nerve. The axillary nerve innervates the deltoid muscle. The deltoid abducts, deltoid muscle is supraclavicular nerves (C3 and C4). Up- adducts, flexes, extends, and rotates the arm medially. The axillary per lateral cutaneous nerve of the arm, a branch of the nerve also innervates the teres minor, which rotates the arm laterally. The dorsal scapular nerve (choice B) innervates both the major and axillary nerve (C5 and C6) supplies the skin over the low- minor rhomboid muscles. These muscles raise the medial border of er half of the deltoid. The skin over the lateral surface of the scapula upward and retract the scapula. The radial nerve (choice C) innervates muscles involved in extension of the forearm and hand. the arm below the deltoid is supplied by the lower lateral The suprascapular nerve (choice D) innervates the supraspinatus and cutaneous nerve of the arm, a branch of the radial nerve infraspinatus. The supraspinatus abducts the arm, whereas the in- (C5 and C6). The skin of the armpit and the medial side of fraspinatus rotates the arm laterally. This nerve travels along the pos- terior aspect of the scapula and would not easily be subjected to inju- the arm is supplied by the medial cutaneous nerve of the ry in a dislocation of the shoulder joint. The thoracodorsal nerve arm (T1), and the skin of the back of the arm is supplied (choice E) innervates the latissimus dorsi, which adducts, extends, and rotates the arm medially. by the posterior cutaneous nerve of the arm, a branch of

34. Answer B. (C) (12) Wrist drop and weak hand grasp indi- 38. Answer A. (4) This patient has decreased sensa- cate that the patient has a lesion of the radial nerve, most likely tion in his C6 and an asymmetric brachioradi- at the distal third of the humerus, sparing the innervation of the triceps brachii but affecting the supinator. Because the patient alis reflex (C6). Although the C6 root contributes to many can extend the elbow, the integrity of the posterior cord (choice different motor functions, wrist extension and elbow flex- A) and posterior divisions (choice B) of the brachial plexus is ion are included among them. Motor findings are unilat- preserved. Lesion of the radial nerve at the midforearm (choice D) and wrist (choice E) would spare the innervation of the supi- eral for this patient, so only the left C6 root is being com- nator. pressed. There are other causes of radicular findings, but compression by a cervical disc is by far the most com- mon.

35. Answer D. (2) The lesion of the ulnar nerve at the elbow causes the loss of adduction (palmar interosseous) and abduction (dorsal interosseous) of the fingers and diffi- culty of the flexion the wrist (flexor carpi ulnaris), clawing of ulnar two fingers is not seen, because extrinsic muscles producing IP joint flexion are also denervated. Froment's sign can be seen. Patients with ulnar nerve injury below midforearm, have characteristic claw hand appearance, in which there is flexion at the IP joints and extension at the MCP joints of the 5th and 4th digits. There is also sensory alteration of the 5th finger and half of the 4th finger.

36. Answer C. (1) A lesion of the upper trunk of the brachial 39. Answer D. (1) Winged scapula is caused by paral- plexus results in a condition called “waiter’s tip hand,” in which ysis of the serratus anterior muscle that results from dam- the arm tends to lie in medial rotation because of paralysis of lateral rotators and abductors of the arm. The long thoracic age to the long thoracic nerve, which arises from the roots nerve, which arises from the root (C5–C7) of the brachial plexus, of the brachial plexus (C5–C7). innervates the serratus anterior muscle that can elevate the arm above the horizontal. The dorsal scapular nerve, which arises from the root (C5), innervates the rhomboid major. The medial side of the arm receives cutaneous innervation from the medial brachial cutaneous nerve of the medial cord. The adductor polli- cis is innervated by the ulnar nerve.

18 Lab 3—Arm & Axilla Nerve — Questions 8 of 10

40. (See Figure below) A rock hits a 10-year-old child on 42. (See Figure Below) The nerve to the latissimus dorsi the chest wall just below the axilla. Several days later, muscle originates from which cord of the brachial plexus? during gym class, the child has difficulty doing push-ups. Which letter in the figure below identifies the injured neu- A. A ral structure? B. B C. C D. D E. E

40. 43. (See Figure Below) Winging of the scapula indicates injury to which nerve of the brachial plexus?

A. A B. B C. C D. D E. E

41. A football player experiences an anterior dislocation of 42 & the shoulder. Cutaneous sensation over the lower half of 43. the deltoid muscle is impaired. These findings suggest damage to which of the following nerves?

A. Axillary B. Median C. Musculocutaneous D. Radial E. Ulnar

44. An 18-year-old boy involved in an automobile accident presents with arm that cannot abduct. His paralysis is caused by damage to which of the following nerves?

A. Suprascapular and axillary B. Thoracodorsal and upper subscapular C. Axillary and musculocutaneous D. Radial and lower subscapular E. Suprascapular and dorsal scapular

19 Lab 3—Arm & Axilla Nerve — Answers

40. Answer A. (6) The injured nerve is at " A," the long 42. Answer C. (2) The brachial plexus is formed by the union of thoracic nerve, which results in a winged scapula at rest, the ventral rami of the lower four cervical nerves and the first thorac- a severe weakness in the ability to protract the scapula. ic nerve. The ventral rami of the fifth and sixth cervical nerves unite to form the upper trunk; the seventh forms the middle trunk; and the eighth cervical and the first thoracic unite to form the lower trunk. Each trunk divides into an anterior and a posterior division. The anterior divisions of the upper and middle trunks unite to form the lateral cord. The anterior division of the lower trunk remains single as the medial cord. The three posterior divisions unite to form the posterior cord. Finally the cords divide into terminal branches. From the posterior cord arises the upper and lower subscapular nerves, articular branches to the shoulder, radial and axillary nerves, and the thoracodorsal nerve, which innervates the latissimus dorsi mus- cle.

43. Answer B. (2) If injured, the long thoracic nerve produces paralysis of the serratus anterior with resultant winging of the scapula. This nerve usually arises by three roots from the fifth, sixth, and seventh cervical nerves. The upper two roots pierce, and the lowest passes in front of the scalenus medius. The nerve descends behind the brachial plexus and the first part of the axillary artery and then runs on the external surface of the serratus anterior to which it gives numerous branches. This nerve may be injured during performance of a mastectomy.

41. Answer A. (4) The axillary nerve can be damaged during anterior dislocation of the shoulder, causing loss of sensation in the skin overlying the lower half of the deltoid muscle. The median nerve (choice B) supplies sensation to the anterior arm, palm, and distal aspects of the lateral three-and-a-half fin- gers. The musculocutaneous nerve (choice C) supplies sensa- tion to the lateral surface of the arm and forearm. The radial nerve (choice D) supplies sensation to the back of the arm, forearm, and hand. The ulnar nerve (choice E) supplies sensation to the medial side of the arm, forearm, and hand.

44. Answer A. (1) The abductors of the arm are the deltoid and supraspinatus muscles, which are innervated by the axillary and suprascapular nerves, respectively. The thoracodorsal nerve supplies the latissimus dorsi, which can adduct, extend, and rotate the arm medially. The upper and lower subscapular nerves supply the sub- scapularis, and the lower subscapular nerve also supplies the teres major; both of these structures can adduct and rotate the arm medially.

20 Lab 3—Arm & Axilla Nerve — Questions 9 of 10

45. (See Figure Below) Section of which nerve will result 47. A victim of an automobile accident is unable to abduct her in the paralysis of the deltoid and the teres minor muscles left arm. This indicates damage to which of the following parts and loss of sensation of a small patch of skin overlying of the brachial plexus? the deltoid muscle A. Middle trunk and posterior cord B. Middle trunk and lateral cord C. Lower trunk and lateral cord D. Upper trunk and posterior cord E. Lower trunk and medial cord

45. 48. A ballet dancer falls to the floor and hurts herself dur- ing a practice session before opening night. She sustains an injury to the thoracodorsal nerve that would probably affect the strength of which of the following movements? A. Adduction of the scapula B. Elevation of the scapula C. Abduction of the arm D. Extension of the arm E. Lateral rotation of the arm

46. A 51-year-old man suffers an injury to the right shoul- 49. A 21-year-old man celebrating his birthday gets a little der during an automobile accident. An AP radiograph of carried away with his friends and starts a bar fight. He is the right shoulder reveals an anterior shoulder dislocation stabbed with a knife that severs the roots of C5 and C6 of in which the head of the humerus lies in a subglenoid po- the brachial plexus. Which of the following muscles is like- sition (Figure E2.14). Which nerve is MOST likely to be ly to be paralyzed? injured by the inferior displacement of the humeral head? A. Infraspinatus A. axillary nerve B. Flexor carpi ulnaris B. median nerve C. Palmar interossei C. musculocutaneous nerve D. Adductor pollicis D. radial nerve E. Palmaris brevis E. ulnar nerve

46.

21 Lab 3—Arm & Axilla Nerve — Answers

45. Answer C. (2) The axillary (circumflex) nerve is a 47. Answer D. (5) Both the upper trunk and posterior terminal branch (C5, 6) of the posterior cord of the brachi- cord of the brachial plexus are damaged. The abductors al plexus. It passes through the quadrilateral space, sup- of the arm are the deltoid and supraspinatus muscles. plies the shoulder joint, teres minor, and the deltoid and The deltoid is innervated by the axillary nerve, which aris- gives off the upper lateral brachial cutaneous nerve. Sec- es from the posterior cord of the brachial plexus. The su- tion of this nerve results in loss of sensation of a small praspinatus is innervated by the suprascapular nerve, area of skin overlying the deltoid muscle and paralysis of which arises from the upper trunk of the brachial plexus. the deltoid and teres minor muscles. The middle and lower trunk give rise to no branches. The lateral and medial cords supply no abductors of the arm.

48. Answer D. (5) The thoracodorsal nerve innervates the latissimus dorsi, which adducts, extends, and medially rotates the arm. The arm is abducted by the supraspina- tus and laterally rotated by the infraspinatus, teres minor, and deltoid (posterior part) muscles. The scapula is ele- vated by the trapezium and levator scapulae muscles and adducted by the rhomboid and muscles.

46. Answer A. (2) The close relation of the axillary 49. Answer A. (5) In Erb-Duchenne paralysis (or upper nerve to the inferior aspect of the shoulder joint capsule in trunk injury), the nerve fibers in the roots of C5 and C6 of the quadrangular space renders the axillary nerve espe- the brachial plexus are damaged. The infraspinatus, a cially susceptible to injury from shoulder dislocations in lateral rotator muscle, is innervated by the suprascapular which the humeral head is inferiorly displaced. The close nerve (C5 and C6). All the other muscles, including the relation of the axillary nerve to the surgical neck of the flexor carpi ulnaris, palmar interossei, adductor pollicis, humerus in the quadrangular space renders the axillary and palmaris brevis muscles, are innervated by the ulnar nerve especially susceptible to injury from fractures of the nerve (C8 and T1). surgical neck.

22 Lab 3—Arm & Axilla Vessels — Questions 1 of 1

1. A 17-year-old boy is injured in an automobile accident. 5. An occlusion of the axillary artery does not result in a He has a fracture of the shaft of the humerus. Which of total loss of blood supply to the upper limb because of the following may be damaged? anastomoses around the scapula. The artery that arises A. Brachial artery B. Posterior humeral circumflex artery from the axillary artery and contributes in a significant way C. Profunda brachii artery to this anastomosis is D. Radial artery E. Radial recurrent artery A. Transverse cervical artery B. C. Dorsal scapular artery D. E. Profunda brachii artery

2. A patient comes in with a gunshot wound and requires 6. A 17-year-old boy with a stab wound received multiple injuries surgery in which his thoracoacromial trunk needs to be on the upper part of the arm and required surgery. If the brachial ligated. Which of the following arterial branches would artery were ligated at its origin, which of the following arteries maintain normal blood flow? would supply blood to the profunda brachii artery? A. Acromial B. Pectoral A. Lateral thoracic C. Clavicular B. Subscapular D. Deltoid C. Posterior humeral circumflex E. Superior thoracic D. Superior ulnar collateral E. Radial recurrent

3. A 10-year-old boy falls off his bike, has difficulty in 7. If the structure indicated by the letter B (Image Below) moving his shoulder, and is brought to an emergency de- is fractured, which of the following structures is most likely partment. His radiogram and angiogram reveal fracture of injured? the surgical neck of his humerus and bleeding from the point of the fracture. This accident most likely leads to damage of which of the following arteries? A. Musculocutaneous nerve A. Axillary B. Radial nerve B. Deep brachial C. Deep brachial artery C. Posterior humeral circumflex D. Posterior humeral circumflex artery D. Superior ulnar collateral E. Scapular circumflex artery E. Scapular circumflex

4. A 35-year-old man receives a stab wound in his axilla. 7. Which of the following arteries is a branch of the axillary artery that would not be affected by an injury to the thora- coacromial artery? A. Acromial artery B. Clavicular artery C. Deltoid artery D. Pectoral artery E. Supreme thoracic artery

23 Lab 3—Arm & Axilla Vessels — Answers

1. The answer is C. (1) The radial nerve accompanies 5. Answer D. (2) The subscapular artery is a large branch the profunda brachii artery in the radial groove on the coming off the third part of the axillary artery. It anastomoses posterior aspect of the shaft of the humerus. The posteri- with the transverse scapular artery that carries blood to the or humeral circumflex artery accompanies the axillary scapular region. Branches from the transverse cervical artery, nerve around the surgical neck of the humerus. Other suprascapular artery, and dorsal scapular artery also contribute arteries are not associated with the radial groove of the to the scapular anastomosis but these arteries are from the sub- humerus. clavian artery. The profunda brachii (deep brachial) artery is a branch of the brachial artery and is not a part of the scapular anastomosis.

2. The answer is E. (1) The is 6. Answer C. (1) The posterior humeral circumflex artery a direct branch of the axillary artery. The thoracoacromial anastomoses with an ascending branch of the profunda brachii trunk has four branches: the pectoral, clavicular, acromial, artery, whereas the lateral thoracic and subscapular arteries do and deltoid. not. The superior ulnar collateral and radial recurrent arteries arise inferior to the origin of the profunda brachii artery.

3. The answer is C. (1) The posterior humeral circumflex 7. Answer D. (1) Fracture of the surgical neck of the hu- artery accompanies the axillary nerve that passes around merus occurs commonly and damages the axillary nerve the surgical neck of the humerus. None of the other arter- and the posterior humeral circumflex artery. ies are involved.

4. The correct answer is E. (UN) The supreme thoracic artery is a branch of the axillary artery that supplies inter- costal muscles in first and second anterior intercostal spaces and nearby muscles. It is not a branch of the . The acromial artery, clavicu- lar artery, deltoid artery and pectoral artery are all branch- es of the thoracoacromial artery.

24 Lab 3—Arm & Axilla Vessels — Questions 2 of 2

8. The axillary artery has become progressively occluded deep to the pectoralis minor muscle. Which pair of blood vessels would most likely provide a significant collateral circulation around the blockage?

A. Posterior humeral circumflex artery and anterior humeral circumflex artery

B. Subscapular artery and posterior humeral circumflex artery

C. Subscapular artery and suprascapular artery

D. and supreme thoracic artery

E. Posterior humeral circumflex artery and profunda brachial artery

25 Lab 3—Arm & Axilla Vessels — Answers

8. Answer C. (6) An anastomosis between the su- prascapular artery-a branch of the and the subscapular, which branches from the axillary distal to the site of the blockage-will provide collateral circulation around the blockage.

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