upper limb Flashcards

Question

A 13-year-old boy is brought to the emergency department after losing control during a motorbike race in which he was run over by several of the other racers. Physical examination reveals several cuts and bruises. He is unable to extend the left wrist, fi ngers, and thumb, although he can extend the elbow. Sensation is lost in the lateral half of the dorsum of the left hand. Which of the following nerves has most likely been injured to result in these signs, and in what part of the arm is the injury located? ⃣ A. Median nerve, anterior wrist ⃣ B. Median nerve, arm ⃣ C. Radial nerve, midhumerus ⃣ D. Ulnar nerve, midlateral forearm ⃣ E. Ulnar nerve, midpalmar region

Answer 1

C. The radial nerve innervates the extensor compartments of the arm and the forearm. It supplies the triceps brachii proximal to the spiral groove, so elbow extension is intact here. It also provides sensory innervation to much of the posterior arm and forearm as well as the dorsal thumb, index, and middle fi ngers up to the level of the fi ngernails. Symptoms are described only in the distal limb due to the midhumeral location of the lesion. The median nerve innervates fl exors of the forearm and thenar muscles and provides sensory innervation to the lateral palmar hand. The ulnar nerve supplies only the fl exor carpi ulnaris and the medial half of the fl exor digitorum profundus in the forearm. Additionally, its sensory distribution is to both the palmar and dorsal aspects of the medial hand. It does not supply extensor muscles. GAS 713, 724; GA 361

Answer 2

D. The musculocutaneous nerve innervates the brachialis and biceps brachii muscles, which are the main fl exors at the elbow. The biceps inserts on the radius and is an important supinator. Because the musculocutaneous nerve is damaged in this case, it leads to loss of sensory perception to the lateral forearm, which is supplied by the distal portion of the musculocutaneous nerve (known as the lateral antebrachial cutaneous nerve). Adduction and abduction of the fi ngers are mediated by the ulnar nerve and would not be affected in this instance. The fl exor pollicis brevis fl exes the thumb and is mainly innervated by the recurrent branch of the median nerve. Flexion of the fi ngers is performed by the long fl exors of the fi ngers and lumbrical muscles, innervated by the median and ulnar nerves. Sensory innervation of the medial forearm is provided by the medial antebrachial cutaneous nerve, a branch of the medial cord of the brachial plexus. GAS 744; GA 424-425

Answer 3

E. The deep radial nerve courses between the two heads of the supinator and is located just medial and distal to the lateral epicondyle. It can be irritated by hypertrophy of the supinator, which compresses the nerve, causing pain and weakness. The ulnar nerve courses laterally behind the medial epicondyle and continues anterior to the fl exor carpi ulnaris. The median nerve passes into the forearm fl exor compartment; the superfi cial radial nerve courses down the lateral aspect of the posterior forearm and would not cause pain due to pressure applied to the posterior forearm. GAS 747; GA 390

Answer 4

B. The lunate is the most commonly dislocated carpal bone because of its shape and relatively weak ligaments anteriorly. Dislocations of the scaphoid and triquetrum are relatively rare. The trapezoid and capitate bones are located in the distal row of the carpal bones. GAS 752-754; GA 392, 394, 422

Answer 5

A. The medial antebrachial cutaneous nerve carries sensory fi bers derived from the C8 and T1 levels. The lateral antebrachial cutaneous nerve is the distal continuation of the musculocutaneous nerve, carrying fi bers from the C5, C6, and C7 levels. The deep branch of the ulnar nerve and the anterior interosseous nerves carry predominantly motor fi bers. The sensory fi bers coursing in the radial nerve are derived from the C5 to C8 levels. GAS 700-709; GA 361, 369-371

Answer 6

C. The contraction of the extensor mechanism produces extension of the distal interphalangeal joint. When it is torn from the distal phalanx, the digit is pulled into fl exion by the fl exor digitorum profundus. The proper palmar digital branches of the median nerve supply lumbrical muscles and carry sensation from their respective digits. Vincula longa are slender, bandlike connections from the deep fl exor tendons to the phalanx that can carry blood supply to the tendons. The insertions of the fl exor digitorum superfi - cialis and profundus are on the fl exor surface of the middle and distal phalanges, respectively, and act to fl ex the interphalangeal joints. GAS 745-747; GA 378, 401

Answer 7

E. In a Smith fracture, the distal fragment of the radius deviates palmarward, often displacing the lunate bone. The other listed bones are unlikely to be displaced in a palmar direction by a Smith fracture. GAS 752-754; GA 392, 394, 422

Answer 8

B. The abductor pollicis longus and extensor pollicis brevis are the occupants of the fi rst dorsal compartment of the wrist. The extensor carpi radialis longus and brevis are in the second compartment. The extensor digitorum is in the third compartment, as is the extensor indicis proprius. The extensor carpi ulnaris is located in the sixth dorsal compartment. GAS 748-749; GA 401-402, 412-413

Answer 9

E. The medial cord has been injured by traction on the lower trunk of the brachial plexus. The medial cord is the continuation of the inferior (lower) trunk of the brachial plexus, which is formed by C8 and T1. C5 and C6 are typically associated with the superior (upper) trunk level and thus the lateral cord. C7 forms the middle trunk. An injury to the posterior cord would usually involve the C7 spinal nerve. This is a typical Klumpke paralysis. GAS 700-709; GA 361, 369-371

Answer 10

A. The fl exor carpi ulnaris muscle is not innervated by the radial nerve but rather by the ulnar UPPER LIMB 195 nerve. The brachioradialis, extensor carpi radialis, and supinator muscles are all innervated by the radial nerve distal to the spiral groove. GAS 737-739; GA 378, 390, 397, 398

Answer 11

A. Injury to the radial nerve in the spiral groove will paralyze the abductor pollicis longus and both extensors of the thumb. This injury will also lead to wrist drop (inability to extend the wrist). Weakness of grip would also occur, although this is not mentioned in the question. If the wrist is fl exed, fi nger fl exion and grip strength are weakened because the long fl exor tendons are not under tension. Note how much your strength of grip is increased when your wrist is extended versus when it is fl exed. GAS 661, 709, 722-724; GA 366, 371

Answer 12

C. The superior ulnar collateral branch of the brachial artery accompanies the ulnar nerve in its path posterior to the medial epicondyle and is important in the blood supply of the nerve. The profunda brachii passes down the arm with the radial nerve. The radial collateral artery arises from the profunda brachii and anastomoses with the radial recurrent branch of the radial artery proximal to the elbow laterally. The inferior ulnar collateral artery arises from the brachial artery and accompanies the median nerve into the forearm. The anterior ulnar recurrent artery arises from the ulnar artery and anastomoses with the inferior ulnar collateral anterior to the elbow. GAS 743, 767-769; GA 368

Answer 13

C. Adduction of the fi fth digit is produced by contraction of the third palmar interosseous muscle. All of the interossei are innervated by the deep branch of the ulnar nerve. Flexion of the proximal interphalangeal joint is a function of the fl exor digitorum superfi cialis, supplied by the median nerve. Opposition of the thumb is a function of the opponens pollicis, supplied by the recurrent branch of the median nerve. GAS 729, 772-774; GA 414

Answer 14

C. The radial nerve is the most likely nerve compressed to cause these symptoms. This type of nerve palsy is often called “Saturday night palsy.” One reason for this nickname is that people would supposedly fall asleep after being intoxicated on a Saturday night with their arm over the back of a chair, thereby compressing the nerve in the spiral groove. The radial nerve innervates all of the extensors of the elbow, wrist, and fi ngers. Paralysis of the lateral cord of the brachial plexus would result in loss of the musculocutaneous nerve and the pectoral nerves, which do not mediate extension of the forearm or hand. The medial cord of the brachial plexus branches into the median nerve and ulnar nerve. Neither of these nerves innervates muscles that control extension. The median nerve innervates fl exors of the forearm and the thenar muscles. The lateral and median pectoral nerves do not extend into the arm and innervate the pectoralis major and minor muscles. GAS 789-790; GA 366, 371

Answer 15

A. The basilic vein can be used for dialysis, especially when the cephalic vein is judged to be too small, as in this case. The basilic vein can be elevated from its position as it passes through the fascia on the medial side of the arm. The cephalic vein passes more laterally up the limb. The lateral cubital vein is a tributary to the cephalic vein, and the medial cubital vein joins the basilic vein—both rather superfi cial in position. The medial antebrachial vein courses up the midline of the forearm (antebrachium) ventrally. GAS 663, 697, 720, 770; GA 350, 360, 377

Answer 16

A. The patient exhibits the classic “benediction attitude” of the thumb and fi ngers from injury to the median nerve proximally in the forearm. The thumb is somewhat extended (radial supplied abductor and extensors unopposed); digits 2 and 3 are extended (by intact interossei); digits 4 and 5 are partially fl exed (by their intact fl exor digitorum profundus). A lesion of the median nerve would result in weakened fl exion of the PIP joints of all digits (fl exor digitorum superfi cialis), loss of fl exion of the interphalangeal joint of the thumb, the DIP joints of digits 2 and 3 (fl exor digitorum profundus), and weakened fl exion of the metacarpophalangeal joints of the second and third digits (fi rst and second lumbricals). A lesion of both the ulnar and median nerves would cause weakness or paralysis of fl exion of all of the digits. A lesion of the ulnar nerve would mostly cause weakness in fl exion of the DIP of the fourth and fi fth digits and would affect all of the interosseous muscles and the lumbricals of the third and fourth digits. A lesion of the radial nerve would cause weakness in extension of the wrist, thumb, and metacarpophalangeal joints. GAS 724, 789-790; GA 371, 376

Answer 17

C. The head of the humerus is displaced inferiorly because in that location it is not supported by rotator cuff muscle tendons or the coracoacromial arch. It is also pulled anteriorly beneath the coracoid process by pectoralis and subscapularis muscles. It would not be displaced posteriorly because it is supported by the teres minor and infraspinatus muscle tendons. It would not be displaced superiorly because the acromioclavicular ligament and supraspinatus reinforce in that direction. A medial dislocation is blocked by the subscapularis tendon. GAS 667; GA 355

Answer 18

A. The anterior axillary (or anterior pectoral) nodes are the fi rst lymph nodes to receive most of the lymph from the breast parenchyma, areola, and nipple. From there, lymph fl ows through central axillary, apical, and supraclavicular nodes in sequence. Rotter’s nodes lie between the pectoral muscles and are, unfortunately, an alternate route in some patients, speeding the rate of metastasis. The parasternal nodes receive lymph from the medial part of the breast and lie along the internal thoracic artery and vein. GAS 709; GA 63

Answer 19

D. The left spinal accessory nerve has been injured distal to the sternocleidomastoid muscle, resulting in paralysis of the trapezius, allowing the shoulder to droop and the superior angle to push out posteriorly. The sternocleidomastoid muscles are intact, as demonstrated by symmetry in strength in turning the head to the right and left. There is no indication of paralysis of the lateral rotators of the shoulder or elbow fl exors (suprascapular nerve or upper trunk). Thoracodorsal nerve injury would result in paralysis of the latissimus dorsi, an extensor, and medial rotator of the humerus. GAS 667, 973-974; GA 370

Answer 20

C. Inability to extend MCP joints. The tendons of the extensor digitorum and extensor digiti minimi, innervated by the radial nerve, are responsible for extension of the MCP, and to a much lesser degree, the PIP and DIP joints. Abduction and adduction of the MCP joints are functions of the interossei, all of which are innervated by the deep ulnar nerve. Extension of the PIP and DIP joints is performed by the lumbricals and interossei. The fi rst two lumbricals are supplied by the median nerve; the other lumbricals and the interossei, by the deep branch of the ulnar nerve. GAS 655; GA 395

Answer 21

C. Fracture of the surgical neck of the humerus often injures the axillary nerve, which innervates the deltoid and teres minor muscles. Abduction of the humerus between 15 ° and the horizontal is performed by the deltoid muscle. Lateral rotation of the humerus is mainly performed by the deltoid muscle, teres minor, and the infraspinatus. The deltoid and teres minor are both lost in this case. Fracture of the glenoid fossa would lead to drooping of the shoulder. Fracture of the anatomic neck of the humerus will similarly lead to a drooping of the shoulder but would not necessarily affect abduction of the humerus. It is also quite unusual. Fracture of the middle third of the humerus would most likely injure the radial nerve. The ulnar nerve would be potentially compromised in a fracture of the medial epicondyle of the humerus. GAS 667, 668; GA 355

Answer 22

B. When cutaneous lymphatics of the breast are blocked by cancer, the skin becomes edematous, except where hair follicles cause small indentations of the skin, giving an overall resemblance to orange peel. Shortening of the suspensory ligaments or retinacula cutis leads to pitting of the overlying skin, pitting that is intensifi ed if the patient raises her arm above her head. Invasion of the pectoralis major by cancer can result in fi xation of the breast, seen upon elevation of the ipsilateral limb. Inversion of areolar skin with involvement of the ducts would also be due to involvement of the retinacula cutis. GAS 709; GA 381

Answer 23

D. The subclavian vein traverses between the clavicle and fi rst rib and is the most superfi cial structure to be damaged following a fracture of the clavicle. The subclavian artery runs deep to the subclavian vein, and though it is in the appropriate location, it would likely not be damaged because of its deep anatomic position. The cephalic vein is a tributary to the axillary vein after ascending on the lateral side of the arm. Its location within the body is too superfi cial and lateral to the site of injury. The lateral thoracic artery is a branch from the axillary artery that runs lateral to the pectoralis minor. It courses inferior and medial from its point of origin from the axillary artery, and it does not maintain a position near the clavicle during its descent. The internal thoracic artery arises from the fi rst part of the subclavian artery before descending deep to the costal cartilages. Its point of origin from the subclavian artery is lateral to clavicular injury. Furthermore, its course behind the costal cartilages is quite medial to the clavicular fracture. GAS 697, 952, 961, 973, 978; GA 37

Answer 24

A. Colles’ fracture is a fracture of the distal end of the radius. The proximal portion of the radius is displaced anteriorly, with the distal bone fragment projecting posteriorly. The displacement of the radius from the wrist often gives the appearance of a dinner fork, thus a Colles’ fracture is often referred to as a “dinner fork” deformity. A scaphoid fracture results from a fracture of the scaphoid bone and would thus not cause displace- ment of the radius. This fracture usually occurs at the narrow aspect (“waist”) of the scaphoid bone. Bennett’s and boxer’s fractures both result from fractures of the metacarpals (fi rst and fi fth, respectively). Volkmann’s ischemic contracture is a muscular deformity that can follow a supracondylar fracture of the humerus, with arterial laceration into the fl exor compartment of the forearm. Ischemia and muscle contracture, with extreme pain, accompany this fracture. GAS 734; GA 392

Answer 25

B. In shoulder separation, either or both the acromioclavicular and coracoclavicular ligaments can be partially or completely torn through. The acromioclavicular joint can be interrupted and the distal end of the clavicle may deviate upward in a complete separation, while the upper limb droops away inferiorly, causing a “step off” that can be palpated and sometimes observed. Displacement of the head of the humerus is shoulder dislocation, not separation. The coracoacromial ligament is not torn in separation (but it is sometimes used in the repair of the torn coracoclavicular ligament). Disruption of the glenoid labrum often accompanies shoulder dislocation. GAS 669; GA 354

Answer 26

A. The nail was fi red explosively from the nail gun and then pierced the ulnar nerve near the coronoid process of the ulna trochlea of the humerus. Paralysis of the medial half of the fl exor digitorum profundus would result (among other signifi cant defi - cits), with loss of fl exion of the distal interphalangeal joints of digits 4 and 5. Ulnar trauma at the wrist would not affect the interphalangeal joints, although it would cause paralysis of interossei, hypothenar muscles, etc. Median nerve damage proximal to the pronator teres would affect proximal interphalangeal joint fl exion and distal interphalangeal joint fl exion of digits 2 and 3 as well as thumb fl exion. Median nerve injury at the wrist would cause loss of thenar muscles but not long fl exors of the fi ngers. Trauma to spinal nerve root C8 would affect all long fi nger fl exors. GAS 729, 771; GA 376, 390

Answer 27

C. The injury has occurred just beyond the third part of the axillary artery. The only collateral arterial channel between the third part of the axillary artery and the brachial artery is that between the posterior humeral circumfl ex and the ascending branch of the profunda brachii—and this anastomotic path is often inadequate to supply the arterial needs of the limb. The posterior humeral circumfl ex arises from the third part of the axillary artery. It typically anastomoses with a variably small, ascending branch of the profunda brachii branch of the brachial artery. The suprascapular artery anastomoses with the circumfl ex scapular deep to the infraspinatus. The dorsal scapular artery (passing beneath the medial border of the scapula) has no anastomosis with thoracodorsal within the scope of the injury. The lateral thoracic artery has no anastomoses with the brachial artery. The supreme thoracic artery (from fi rst part of axillary) has no helpful anastomoses with the thoracoacromial (second part of axillary). GAS 683, 696, 697; GA 368

Answer 28

E. The scaphoid (or the older term, navicular) bone is the most commonly fractured carpal bone. GAS 752-754; GA 392, 394, 422

Answer 29

E. The anterior interosseous nerve is a branch of the median nerve that supplies the fl exor pollicis longus, the lateral half of the fl exor digitorum profundus, and the pronator quadratus. If it is injured, fl exion of the interphalangeal joint of the thumb will be compromised. The median nerve gives rise to the anterior interosseous nerve but is not a direct enough answer as injury to it would result in more widespread effects. The posterior interosseous nerve supplies extensors in the forearm, not fl exors. The radial nerve gives rise to the posterior interosseous nerve and is not associated with the anterior interosseous nerve; therefore, it would not have any effect on the fl exors of the forearm. The recurrent median nerve is also a branch of the median nerve but supplies the thenar eminence muscles, and its injury would result in problems with opposable motion of the thumb. GAS 743, 751; GA 400

Answer 30

C. The tendon of the long head of the biceps brachii muscle passes through the glenohumeral joint, surrounded by synovial membrane. The glenohumeral is a ligament that attaches to the glenoid labrum. The long head of the triceps arises from the infraglenoid tubercle, beneath the glenoid fossa. The infraspinatus tendon passes posterior to the head of the humerus to insert on the greater tubercle. The coracobrachialis arises from the coracoid process and inserts on the humerus. GAS 694, 715-716, 735; GA 370

Answer 31

E. The suprascapular artery passes over, and the suprascapular nerve passes under, the superior transverse scapular ligament. This ligament bridges the suprascapular notch in the upper border of the scapula. The artery and nerve then pass deep to the supraspinatus muscle, thereafter supplying it and then passing through the spinoglenoid notch to supply the infraspinatus. The subscapular artery is a branch of the third part of the axillary artery; it divides into circumfl ex scapular and thoracodorsal branches. The transverse cervical artery courses anterior to this site. The dorsal scapular artery and nerve pass deep to the medial border of the scapula. The posterior humeral circumfl ex branch of the axillary artery passes through the quadrangular space with the axillary nerve. GAS 696, 697; GA 366, 368

Answer 32

A. The patient has suffered injury to the radial nerve in the midhumeral region. The nerve that provides sensation to the dorsum of the hand proximal to the thumb and index fi nger is the superfi cial branch of the radial nerve. The posterior interosseous nerve supplies a strip of skin on the back of the forearm and wrist extensors. The lateral antebrachial cutaneous nerve is a continuation of the musculocutaneous nerve and supplies the lateral side of the forearm. The medial antebrachial cutaneous is a direct branch of the medial cord and supplies skin of the medial side of the forearm. The dorsal cutaneous branch of the ulnar nerve supplies the medial side of the dorsum of the hand. GAS 772-774; GA 417

Answer 33

C. The seventh cervical nerve makes a major contribution to the radial nerve, and this nerve is the prime mover in wrist extension. The dermatome of C7 is in the region described. GAS 700-709; GA 361, 369-371

Answer 34

B. As the radial artery passes from the ventral surface of the wrist to the dorsum, it crosses through the anatomic snuffbox, passing over the scaphoid bone. The ulnar artery at the wrist is located on the medial side of the wrist, passing from beneath the fl exor carpi ulnaris to reach Guyon’s canal between the pisiform bone and the fl exor retinaculum. The anterior interosseous and posterior interosseous arteries arise from the common interosseous branch of the ulnar artery and pass proximal to distal in the forearm between the radius and ulna, in the fl exor and extensor compartments, respectively. The deep palmar branch of the ulnar artery passes between the two heads of the adductor pollicis to anastomose with the radial artery in the palm. GAS 759; GA 422

Answer 35

D. The patient is suffering from subacromial or subdeltoid bursitis. (If the pain on palpation is less when the arm has been elevated to the horizontal, the bursitis may be thought of as being more subacromial, that is, associated more with the supraspinatus tendon perhaps, for such a bursa may be drawn back under the acromion when the limb is abducted.) The subscapular bursa, beneath the subscapularis muscle, would not present as superfi cial pain. It can communicate with the glenohumeral joint cavity. Infl ammation or arthritic changes within the glenohumeral joint present as more generalized shoulder pain than that present here. The teres minor muscle and tendon are located inferior to the point of marked discomfort. GAS 670; GA 358

Answer 36

E. The axillary sheath is a fascial continuation of the prevertebral layer of the deep cervical fascia extending into the axilla. It encloses the nerves of the neurovascular bundle of the upper limb. Superfi cial fascia is loose connective tissue between the dermis and the deep investing fascia and contains fat, cutaneous vessels, nerves, lymphatics, and glands. The buccopharyngeal fascia covers the buccinator muscles and the pharynx mingles with the pretrachial fascia. The clavipectoral muscle invests the clavicle and pectoralis minor muscle. The axillary fascia is continuous with the pectoral and latissimus dorsi fascia and forms the hollow of the armpit. GAS 700-709; GA 361, 369-371

Answer 37

C. The spinal accessory nerve arises from the ventral rootlets of C1 to C4 and ascends through the foramen magnum to then exit the cranial cavity through the jugular foramen. It innervates the sternocleidomastoid and trapezius muscles, which function in head rotation and raising of the shoulders. The suprascapular nerve receives fi bers from C5-6 (occasionally from C4 if the plexus is “prefi xed”) and innervates the supraspinatus muscle, which is responsible for the fi rst 15 ° of arm abduction. Erb point of the brachial plexus is at the union of C5-6 spinal nerves. The long thoracic nerve arises from plexus routes C5, 6, and 7, and supplies the serratus anterior. GAS 700-706; GA 361, 369-371

Answer 38

D. The acromioclavicular ligament connects the clavicle to the coracoid process of the scapula. Separation of the shoulder (dislocation of the acromioclavicular [AC] joint) is associated with damage to the acromioclavicar ligament (capsule of the AC joint) and, in more severe injuries, disruption of the coracoclavicular ligaments (conoid and trapezoid portions). The glenohumeral ligament may be injured by an anterior dislocation of the humerus but is not likely to be injured by a separated shoulder. The coracoacromial ligament, transverse scapular ligament, and tendon of the long head of triceps brachii are not likely to be injured by separation of the shoulder. GAS 669; GA 354, 363

Answer 39

A. The quadrangular space is bordered medially by the long head of the triceps, laterally by the surgical neck of the humerus, superiorly by the teres minor and subscapularis muscles, and inferiorly by the teres major muscle. Both the axillary nerve and posterior humeral circumfl ex vessels traverse this space. The other structures listed are not contained within the quadrangular space. The cephalic vein is located in the deltopectoral triangle, and the radial nerve is located in the triangular interval. GAS 700-709; GA 361, 369-371

Answer 40

B. Froment’s sign is positive for ulnar nerve palsy. More specifi cally it tests the action of the adductor pollicis muscle. The patient is asked to hold a sheet of paper between the thumb and a fl at palm. The fl exor pollicis longus is innervated by the anterior interosseous branch of the median nerve. The fl exor digiti minimi is innervated by the deep branch of the ulnar nerve and would not be used to hold a sheet of paper between the thumb and palm. The fl exor carpi radialis is innervated by the median nerve, and the extensor indicis is innervated by the radial nerve. GAS 763-765; GA 410, 412

Answer 41

C. The recurrent branch of the median nerve innervates the thenar muscles (opponens pollicis, abductor pollicis brevis, and fl exor pollicis brevis) and is not responsible for any cutaneous innervation. Damage to the palmar cutaneous branches of the median nerve or to the ulnar nerve would not cause weakness of opposition of the thumb for they are principally sensory in function. The deep branch of the ulnar nerve supplies the hypothenar muscles, adductor and abductor muscles of digits 2–5, and does not innervate the abductor policis brevis. GAS 770-771; GA 414

Answer 42

D. Injury to the deep branch of the ulnar nerve results in paralysis of all interosseous muscles and the lumbrical muscles of digits 4 and 5. Extension of the metacarpophalangeal joints is intact, a function of the radial nerve. Interphalangeal extension of digits 4 and 5 is absent, due to the loss of all interosseous muscle and the lumbricals of digits 4 and 5. Some weak interphalangeal joint extension is still present in digits 2 and 3 because the lumbricals of these two fi ngers are innervated by the median nerve. The radial nerve and the median nerve appear to be intact in this case. If the ulnar nerve were injured in the midforearm region, there would be sensory loss in the palm and digits 4 and 5 and on the dorsum of the hand. The recurrent branch of the median nerve supplies the thenar muscles; it does not supply lumbricals. Moreover, paralysis of this nerve would have no effect on the interphalangeal joints. GAS 770-771; GA 415

Answer 43

A. The circumfl ex scapular artery passes through the triangular space after arising from the subscapular artery. It provides superfi cial branches to the overlying latissimus dorsi, whereas its deep portion passes into the infraspinous fossa to anastomose with the suprascapular artery. The dorsal scapular artery passes between the roots of the brachial plexus and then deep to the medial border of the scapula. The transverse cervical artery arises from the thyrocervical trunk at the root of the neck and can provide origin for a dorsal scapular branch. The lateral thoracic and thoracoacromial arteries are branches of the second part of the axillary artery and provide no supply to the latissimus dorsi. GAS 683, 684, 697; GA 368

Answer 44

C. The surgical neck of the humerus is a typical site of fractures. The fracture line lies above the insertions of the pectoralis major, teres major, and latissimus dorsi muscles. The supraspinatus muscle abducts the proximal fragment, whereas the distal fragment is elevated and adducted. The elevation results from contraction of the deltoid, biceps brachii, and coracobrachialis muscles. The adduction is due to the action of pectoralis major, teres major, and latissimus dorsi. GAS 139-140, 659, 686-687; GA 374, 492

Answer 45

B. The fracture line of the upper third of the radius lies between the bony attachments of the supinator and the pronator teres muscles. The distal radial fragment and hand are pronated due to unopposed contraction of pronator teres and pronator quadratus muscles. The proximal fragment deviates laterally by the unopposed contraction of the supinator muscle. The brachioradialis inserts distally on the radius. The brachialis inserts on the coronoid process of the ulna and would not be involved in the lateral deviation of the radius. GAS 736, 747-749; GA 390

Answer 46

A. The palmaris longus passes along the midline of the fl exor surface of the forearm. The fl exor carpi radialis is seen in the lateral portion of the forearm superfi cially, passing over the trapezium to insert at the base of the second metacarpal. The abductor pollicis longus tendon is laterally located in the wrist, where it helps form the lateral border of the anatomic snuffbox. The fl exor carpi ulnaris tendon can be seen and palpated on the medial side of the wrist ventrally. The fl exor pollicis longus tendon passes deep through the carpal tunnel. GAS 737-739; GA 374, 390, 398

Answer 47

B. The student had broken the neck of the fi fth metacarpal when hitting the machine with his fi st. This is the more common type of “boxer’s fracture.” Neither a fracture of the ulnar styloid nor a Colles’ fracture nor a Smith fracture of the distal radius would present with the absence of a knuckle as observed here. Bennett’s fracture involves dislocation of the carpometacarpal joint of the thumb. Indications are that the injury is on the medial side of the hand, not the wrist, nor the lateral side of the hand or wrist. GAS 769; GA 392, 394

Answer 48

E. Scoliosis (severe, lateral curvature of the spine) in the patient is causing compression or stretching of the T1 spinal nerve root by the fi rst rib as the nerve ascends to join C8 and form the lower trunk of the brachial plexus. T1 provides sensation for the medial side of the forearm, via the medial antebrachial cutaneous nerve from the medial cord of the brachial plexus. T1 is the principal source of motor supply to all of the intrinsic muscles in the palm. Its dysfunction affects all fi ne motor movements of the digits. Long fl exors of the fi ngers are intact; therefore, the median nerve and ulnar nerve are not at fault. The extensors of the wrist are functional; therefore, the radial nerve is not paralyzed. The only sensory disturbance is that of the T1 dermatome. GAS 700-709; GA 361, 369-371

Answer 49

D. Interestingly, “gamekeeper’s thumb” was a term coined because this injury was most commonly associated with Scottish gamekeepers who, it is said, killed small animals such as rabbits by breaking their necks between the ground and the gamekeeper’s thumb and index fi nger. The resulting valgus force on the abducted MCP joint caused injury to the ulnar collateral ligament. These days this injury is more commonly seen in skiers who land awkwardly with their hand braced on a ski pole, causing the valgus force on the thumb as is seen in this patient. Whereas the term “skier thumb” is sometimes used, “gamekeeper’s thumb” is still in common usage. GAS 755; GA 395

Answer 50

A. The long head of the biceps assists in shoulder fl exion and during a tendinopathy would cause pain in the anterior compartment of the shoulder, where it originates at the supraglenoid tubercle. Also, forced contraction would cause more of a greater tension force on the tendon. GAS 694, 715-716; GA 370

Answer 51

C. The common extensor tendon originates from the lateral epicondyle, and infl ammation of this tendon is lateral epicondylitis, nicknamed “tennis elbow” because the tendon is often irritated during the backhand stroke in tennis. Because the extensors of the wrist originate as part of the common extensor tendon, extension of the wrist will exacerbate the pain of lateral epicondylitis. GAS 691; GA 380

Answer 52

C. The axillary nerve passes dorsally around the surgical neck of the humerus (accompanied by the posterior humeral circumfl ex artery) and can be injured when the humerus is fractured at that location. The axillary nerve provides sensation to the skin over the upper, lateral aspect of the shoulder. Therefore, although the patient might not be able to abduct the arm because of the injury, a simple test of skin sensation can indicate whether there is associated nerve injury of the axillary nerve. Shrugging the shoulders can help assess trapezius function, thereby testing the spinal accessory nerve. Intact sensation of the skin on the medial aspect of the axilla or arm is an indication that the radial or intercostobrachial nerves are functional. Pushing against an immovable object tests the serratus anterior muscle and the long thoracic nerve. GAS 667; GA 355

Answer 53

E. The surgeon took the distal segments of the median nerves from both forearms, mistakenly believing them to be palmaris longus tendons. Both of the structures lie in the midline of the ventral surface of the distal forearm and are often of similar appearance in color and diameter. The nerve is located deep to the tendon, when the tendon is present, but when the tendon is absent, the nerve appears to be where the tendon belongs. There is no evidence of rib fractures; even so, a fractured rib would not explain loss of sensation on the lateral portion of the palm. Lower plexus trauma (C8, T1) would result in paralysis of forearm fl exor muscles and all intrinsic hand muscles and sensory loss over the medial dorsum of the hand, in addition to palmar sensory loss. Dupuytren’s contracture is a fl exion contracture of (usually) digits 4 and 5 from connective tissue disease in the palm. Radial nerve injury in the posterior forearm would affect metacarpophalangeal joint extension, thumb extension, etc., not palmar disturbances. GAS 743-744; GA 400

Answer 54

C. Trauma both to the median and ulnar nerves at the wrist results in total clawing of the fi ngers. The metacarpophalangeal joints of all digits are extended by the unopposed extensors because the radial nerve is intact. All interossei and lumbricals are paralyzed because the deep branch of the ulnar nerve supplies all of the interossei; lumbricals I and II are paralyzed, for they are innervated by the median nerve; lumbricals III and IV are paralyzed, for they receive supply from the deep ulnar nerve. The interossei and lumbricals are responsible for extension of the interphalangeal joints. When they are paralyzed, the long fl exor tendons pull the fi ngers into a position of fl exion, completing the “claw” appearance. If the median nerve were intact, the clawing would be less noticeable in the index and long fi nger because the two lumbricals would still be capable of some degree of extension of those interphalangeal joints. If the median nerve alone is injured in the carpal tunnel, there would be loss of thenar opposition but not clawing. If the median and ulnar nerves are both transected at the elbow, the hand appears totally fl at because of the loss of long fl exors, in addition to intrinsic paralysis. GAS 726; GA 400

Answer 55

D. Colles’ fracture is a fracture of the distal radius with the distal fragment displaced dorsally. Smith’s fracture involves the distal fragment displaced in a volar direction. Smith’s fracture is sometimes referred to as a reverse Colles’ fracture. GAS 756; GA 392

Answer 56

E. The extensor tendons of the fi ngers insert distally on the distal phalanx of each digit. If the tendon is avulsed, or the proximal part of the distal phalanx is detached, the distal interphalangeal joint is pulled into total fl exion by the unopposed fl exor digitorum profundus. This result gives the digit the appearance of a mallet. In boutonnière deformity, the central portion of the extensor tendon expansion is torn over the PIP joint, allowing the tendon to move palmarward, causing the tendon to act as a fl exor of the PIP joint. This causes the DIP joint to be hyperextended. Swanneck deformity involves slight fl exion of MCP joints, hyperextension of PIP joints, and slight fl exion of DIP joints. This condition results most often from shortening of the tendons of intrinsic muscles, as in rheumatoid arthritis. Dupuytren contracture results from connective tissue disorder in the palm, usually causing irreversible fl exion of digits 4 and 5. Clawhand occurs with lesions to the median and ulnar nerves at the wrist. In this clinical problem all intrinsic muscles are paralyzed, including the extensors of the interphalangeal joints. The MCP joint extensors, supplied by the radial nerve, and the long fl exors of the fi ngers, supplied more proximally in the forearm by the median and ulnar nerves, are intact and are unopposed, pulling the fi ngers into the “claw” appearance. GAS 760; GA 392, 394, 422

Answer 57

A. Because the median nerve is injured within the cubital fossa, the long fl exors are paralyzed, including the fl exor pollicis longus. Flexor pollicis longus would not be paralyzed if the median nerve were injured at the wrist. Lateral palm sensory loss con- fi rms median nerve injury. If only the anterior interosseous nerve were damaged, there would be no cutaneous sensory defi cit. The radial nerve supplies wrist extensors, long thumb abductor, and metacarpophalangeal joint extensors. The ulnar nerve does not supply sensation to the lateral palm. GAS 651, 729, 731; GA 400

Answer 58

D. In a lesion of the lower trunk, or the C8 and T1 nerve roots, there is sensory loss on the medial forearm and the medial side of hand (dorsal and ventral). The medial cord is the extension of the lower trunk. The medial cord gives origin to the medial antebrachial cutaneous nerve, which supplies the T1 dermatome of the medial side of the antebrachium. The lower lateral brachial cutaneous nerve arises from the radial nerve, C5 and C6. The musculocutaneous nerve arises from the lateral cord, ending in the lateral antebrachial cutaneous nerve, with C5 and C6 dermatome fi bers. The intercostobrachial nerve is the lateral cutaneous branch of the T2 ventral primary ramus and supplies skin on the medial side of the arm. The median nerve distributes C6 and C7 sensory fi bers to the lateral part of the palm, thumb, index, long fi nger, and half of the ring fi nger. GAS 743-745, 771-772; GA 384

Answer 59

C. The fi rst branch of the lateral pectoral nerve is typically the only source of motor supply to the clavicular head of the pectoralis major. If it is injured (as in this case of an iatrogenic injury when the infraclavicular nodes were removed), this part of the muscle undergoes atrophy, leaving an infraclavicular cosmetic defi cit. The remainder of the lateral pectoral nerve joins the medial pectoral nerve in a neural arch that provides motor supply to the remaining parts of the pectoralis major and the pectoralis minor. Physical examination reveals no obvious motor or sensory defi cits. Loss of the medial pectoral nerve would have no effect on the clavicular head of pectoralis major and might not be discernible. Injury to the lateral cord would lead to loss not only of all of the lateral pectoral nerve but also the musculocutaneous nerve, resulting in biceps and brachialis paralysis and lateral antebrachial sensory loss. GAS 688, 702, 706; GA 370

Answer 60

B. The C6 spinal nerve is primarily responsible for the brachioradialis refl ex. C5 and C6 are both involved in the biceps brachii refl ex; C5 for motor, C6 for the sensory part of the refl ex arc; C7 is the key spinal nerve in the triceps refl ex. GAS 700-709; GA 361, 369-371

Answer 61

C. C7 is the main spinal nerve that contributes to the radial nerve and innervates the triceps. Absence of the triceps refl ex is usually indicative of a C7 radiculopathy or injury. GAS 700-709; GA 361, 369-371

Answer 62

B. Ginglymus joint is the technical term to describe a hinge joint. It allows motion in one axis (fl exion and extension in the case of the elbow) and is therefore a uniaxial joint. The other types of joints listed allow motion in more than one axis. GAS 79-81; GA 372

Answer 63

C. A fracture of the humerus just proximal to the epicondyles is called a supracondylar fracture. This is the most common cause of a Volkmann ischemic fracture. The sharp bony fragment often lacerates the brachial (or other) artery, with bleeding into the fl exor compartment. Diminution of arterial supply to the compartment results in the ischemia. Bleeding into the compartment causes greatly increased pressure, fi rst blocking venous outfl ow from the compartment, then reducing the arterial fl ow into the compartment. The ischemic muscles then undergo unrelieved contracture. A humeral fracture is sometimes placed in a cast from shoulder to wrist, often concealing the ischemia until major tissue loss occurs. Cold, insensate digits and great pain are warnings of this compartmental problem, demanding that the cast be removed and the compartment opened (“released”) for pressure reduction and vascular repair. Fracture of the surgical neck endangers the axillary nerve and posterior humeral circumfl ex artery, although not ischemic contracture. Fracture of the humerus in the spiral groove can injure the radial nerve and profunda brachii artery. Fracture of the olecranon does not result in Volkmann’s contracture, although the triceps brachii can displace the distal fractured fragment of the ulna. GAS 728; GA 355

Answer 64

D. Normally, the distal part of the ulna articulates only with the radius at the distal radioulnar joint at the wrist, a joint that participates in pronation/ supination. The head of the ulna does not articulate with any of the carpal bones; instead, it is separated from the triquetrum and lunate bones by the triangular fi brocartilage complex between it and the radius. The pisiform articulates with the triquetrum. The carpal articulation of the radius is primarily that of the scaphoid (old name is navicular) bone. GAS 713, 714, 731-733; GA 391

Answer 65

A. The force of the woman’s fall on the outstretched hand was transmitted up through the forearm, sometimes resulting in dislocation of the olecranon at the elbow, putting traction on the ulnar nerve as it passes around the medial epicondyle of the humerus. Ulnar trauma at the elbow can cause weakness in medial fl exion (adduction) at the wrist, from loss of the fl exor carpi ulnaris. Ulnar nerve injury also results in sensory loss in the medial hand and paralysis of the interossei and medial two lumbricals, with clawing especially of digits 4 and 5. Injury of the ulnar nerve at the pisiform bone would not affect the fl exor carpi ulnaris, nor would it produce sensory loss on the dorsum of the hand because the dorsal cutaneous branch of the ulnar branches off proximal to the wrist. Carpal tunnel problems affect median nerve function, which is not indicated here. The ulnar nerve passes medial to the cubital fossa between the heads of the fl exor carpi ulnaris, not between the heads of the fl exor digitorum superfi cialis. Injuries at the radial neck affect the site of division of the radial nerve, and its paralysis would not result in the clinical problems seen in this patient. GAS 727-728; GA 386

Answer 66

D. The interossei are the most important muscles in extension of the interphalangeal (IP) joints because of the manner of their insertion into the extensor expansion of the fi ngers, which passes dorsal to the transverse axes of these joints. The lumbrical muscles assist in IP extension, in addition to fl exing the metacarpophalangeal joints. Ulnar nerve injury at the wrist results in paralysis of all the interossei and the medial two lumbricals. Extensors of the MCP joints are innervated by the deep radial nerve. Unopposed extension of the MCP joints causes them to be held in extension whereas unopposed long fl exors of the fi ngers (supplied by median and ulnar nerves proximally in the forearm) cause them to be fl exed into the “claw” position. The lumbricals of digits 2 and 3 are still intact because they are supplied by the median nerve, so clawing is not seen as much on these digits. Loss of opposition would result from median or recurrent nerve paralysis. If the ulnar nerve is cut at the wrist, its dorsal cutaneous branch to the dorsum of the hand is unaffected. GAS 655, 755; GA 395

Answer 67

B. In boutonnière deformity, the central portion of the extensor tendon expansion is torn over the PIP joint, allowing the tendon to move palmarward, causing the tendon to act as a fl exor of the PIP joint. This causes the DIP joint to be hyperextended. The tear in the extensor tendon is said to resemble a buttonhole (“boutonnière” in French), and the head of the proximal phalanx may stick through the hole. GAS 732-755; GA 395

Answer 68

D. Swan-neck deformity involves slight fl exion of MCP joints, hyperextension of PIP joints, and slight fl exion of DIP joints. This condition results most often from shortening of the tendons of intrinsic muscles, as in rheumatoid arthritis. When asked to straighten the injured fi nger, the patient is unable to do so and the curvature of the fi nger somewhat resembles the neck of a swan. GAS 732-755; GA 395

Answer 69

C. The long thoracic nerve was injured during the axillary dissection, resulting in paralysis of the serratus anterior. The serratus anterior is important in rotation of the scapula in raising the arm above the level of the shoulder. Its loss results in protrusion of the inferior angle (“winging” of the scapula), which is more obvious when one pushes against resistance. The long thoracic nerve arises from brachial plexus roots C5, C6, and C7. The upper trunk (C5, C6) supplies rotator and abductor muscles of the shoulder and elbow fl exors. The posterior division of the middle trunk contains C7 fi bers for distribution to extensor muscles; likewise, the posterior cord supplies extensors of the arm, forearm, and hand. The lateral cord (C5, C6, and C7) gives origin to the lateral pectoral nerve, the musculocutaneous nerve, and the lateral root of the median nerve. There is no sensory loss in the limb in this patient; injury to any of the other nerve elements listed here would be associated with specifi c dermatome losses. GAS 700-709; GA 361, 369-371

Answer 70

B. Dupuytren contracture or deformity is a result of fi bromatosis of palmar fascia, resulting in irregular thickening of the fascial attachments to the skin, which causes gradual contraction of the digits, especially digits 4 and 5. In 50% of cases, it is bilateral in occurrence. Ape hand, or fl at hand, is a result of loss of the median and ulnar nerves at the elbow, with paralysis of all long fl exors of the fi ngers and all intrinsic hand muscles. Clawhand results from paralysis of interphalangeal joint extension by interossei and lumbricals, innervated primarily by the ulnar nerve. Wrist drop occurs with radial nerve paralysis and loss of the extensors carpi radialis longus and brevis. Mallet fi nger results from detachment of the extensor mechanism from the distal phalanx of a fi nger and unopposed fl exion of that distal interphalangeal joint. GAS 758; GA 398

Answer 71

A. The axillary nerve is a direct branch of the posterior cord and wraps around the surgical neck of the humerus to innervate the teres minor and the deltoid muscles. With this anatomic arrangement, the axillary nerve is tightly “tethered” to the proximal humerus. When the head of the humerus is dislocated, it often puts traction on the axillary nerve. GAS 674; GA 631

Answer 72

A. The long head of the biceps brachii muscles runs in the intertubercular groove on the proximal humerus as it changes direction and turns medially to attach to the supraglenoid tubercle of the scapula. This change in direction within an osseous structure predisposes the tendon to wear and tear, particularly in people who overuse the biceps muscle. This type of injury presents with a characteristic sign called the “Popeye sign.” GAS 694, 715-716, 735; GA 370

Answer 73

C. The supraspinatus muscle inserts on the greater tubercle of the humerus and is said to initiate abduction of the arm at the shoulder. It is supplied principally by spinal nerve C5. The subscapularis muscle is the only muscle that inserts on the lesser tubercle. The subscapularis muscle is innervated by the upper and lower subscapular nerves. The teres minor takes origin from the lateral border of the scapula; the teres major takes origin from the region of the inferior angle and the lateral border of the scapula. GAS 678-679; GA 369

Answer 74

E. During a fall on an outstretched upper limb, the forces are conducted through the hand on up through the bones of the limb in succession. Often these bones do not fracture but rather pass the compressive forces proximally. The appendicular skeleton joins with the axial skeleton at the sternoclavicular joint. The forces are not suffi ciently transferred to the sternum, causing the clavicle to absorb the force, resulting in fracture of this sigmoidalshaped bone. GAS 673; GA 4, 6-7, 56-57, 65, 108, 351

Answer 75

C. The patient is suffering from thoracic outlet syndrome, involving neural and vascular elements. This results from any condition that decreases the dimensions of the superior thoracic aperture. It could be a result of a cervical rib, accessory muscles, and/or atypical connective tissue bands at the root of the neck. In this case, symptoms involve the arm, forearm, and hand. Paraesthesia along the medial forearm and hand and atrophy of long fl exors and intrinsic muscles point to a possible compression or traction problem of the lower trunk (C8, T1) rather than a lesion of either the median or ulnar nerve. The lateral palm has no sensory problem, which tends to rule out median nerve involvement. Changes in the radial pulse point to vascular compression. Erb-Duchenne paralysis of the upper trunk would affect proximal limb functions, such as arm rotation, abduction, etc. This lesion is on the left side, so the brachiocephalic artery could not be involved because it arises from the right side of the aortic arch; moreover, it would not compress the brachial plexus. Carpal tunnel syndrome would not explain the problems of the forearm and medial hand, or the long fl exor atrophy. An isolated medial cord lesion would not explain the atrophy of all long fl exors and intrinsic muscles and does not explain the radial pulse characteristics. The ischemic pain in the arm is due to vascular compression. GAS 147; GA 370

Answer 76

A. The ulnar nerve enters the forearm by passing between the two heads of the fl exor carpi ulnaris and descends between and innervates the fl exor carpi ulnaris (for medial wrist deviation) and fl exor digitorum profundus (medial half) muscles. Injuring the ulnar nerve results in clawhand. It enters the hand superfi cial to the fl exor retinaculum and lateral to the pisiform bone, where it is vulnerable to damage. The ulnar nerve also enters Guyon’s canal, but damage to it here would not present with the aforementioned symptoms. The median nerve enters the carpal tunnel and the radial nerve passes deep to the brachioradialis. GAS 737; GA 398

Answer 77

B. During a breech delivery as described here, downward traction is applied to the shoulders and upper limbs as the baby is forcibly extracted from the birth canal. This exerts traction on the upper cord of the brachial plexus, often causing a traction injury from which the baby can often recover. If the roots of C5 and C6 are avulsed from the spinal cord, the injury is permanent. GAS 700-709; GA 361, 369-371

Answer 78

E. Striking the concrete blocks with the medial side of her hand has injured the ulnar nerve in Guyon’s canal. This is the triangular tunnel formed by the pisiform bone medially, the fl exor retinaculum dorsally, and the deep fascia of the wrist ventrally. This injury would result in loss of sensation to the medial palm and the palmar surface of the medial one and a half digits and motor loss of the hypothenar muscles, the interossei, and the medial two lumbricals. The median nerve is not involved, for the thenar muscles and lateral palmar sensations are intact. The dorsal ulnar nerve arises proximal to the wrist, thus it would not be lost. Carpal dislocation is unlikely. If the lunate bone were dislocated, it would not cause compression of the ulnar nerve at the wrist. There is no indication of fi fth metacarpal fracture, the so-called boxer’s fracture. GAS 744; GA 417

Answer 79

E. The common fl exor sheath encloses the long fl exor tendons of the fi ngers. This sheath is usually continuous with the fl exor sheath of the little fi nger, which continues within the palm, having no connection with sheaths of the other digits, which do not extend into the palm. GAS 755; GA 410

Answer 80

C. The infectious agent was introduced into the synovial sheath of the long tendons of the little (fi fth) fi nger. Proximally, this sheath runs through the midpalmar space, and infl ammatory processes typically rupture into this space unless aggressively treated with the appropriate antibiotics. GAS 768; GA 410

Answer 81

A. Axillary-subclavian vein thrombosis is becoming much more common in recent years because of the extensive use of catheters in cancer patients and other chronic medical conditions. Effort-induced thrombosis is seen with strenuous use of the dominant arm with hyperabduction and external rotation of the arm or backward and downward rotation of the shoulder as in playing cricket, volleyball, or baseball or chopping wood. Because the symptoms of subclavian stenosis are fairly dramatic, most patients present promptly, usually within 24 hours. They complain of a dull ache in the shoulder or axilla, the pain worsened by activity. Conversely, rest and elevation often relieve the pain. Patients with catheter-associated axillary-subclavian deep vein thrombosis report similar symptoms at the arm or shoulder on the side with the indwelling catheter. GAS 722; GA 377

Answer 82

C. The injury is at the second part of the axillary artery. The suprascapular artery is a branch of the thy- rocervical trunk off the subclavian artery, proximal to the axillary artery. The subscapular artery is the major branch of the third part of the axillary artery, giving of the thorocodorsal and the circumfl ex scapular. In this case blood would be fl owing from the circumfl ex scapular artery in a retrograde direction into the axillary artery, supplying blood distal to the injury. GAS 695; GA 368

Answer 83

A. This proximal injury to the median nerve would paralyze all of the long fl exors of the digits, except for the DIP fl exors of digits 4 and 5, thereby swinging the “balance of power” to the muscles that extend the digits, all of which are innervated by the radial nerve. The intrinsic hand muscles can aid in fl exion of the MCP joints, and they are innervated by the ulnar nerve. However, they are of insuffi cient size to compensate for the extensor forces exerted on fi ngers. GAS 518, 611, 612; GA 395

Answer 84

C. The winged scapula results from a lesion of the long thoracic nerve, which supplies the serratus anterior muscle. This muscle is responsible for rotating the scapula upward, which occurs during abduction of the arm above the horizontal. The long thoracic nerve comes off the C5 to C7 roots of the brachial plexus. The diaphragm is supplied by the phrenic nerve, which comes off the spinal nerve roots C3 to C5. GAS 700-709; GA 361, 369-371

Answer 85

A. The median nerve supplies sensory innervation to the thumb, index, and middle fi nger as well as to the lateral half of the ring fi nger. The median nerve also provides motor innervation to muscles of the thenar eminence. Compression of the median nerve in the carpal tunnel explains these defi cits in conjunction with normal functioning of the fl exor compartment of the forearm. The ulnar nerve is not implicated in these symptoms. Compression of the brachial plexus could not be attributed to pressure from hypertrophy of the triceps, it is located distal to the plexus. In addition, symptoms would include several upper limb defi cits rather than the focal symptoms described in this instance. Osteoarthritis of the cervical spine would also lead to increasing complexity of symptoms. GAS 764, 788; GA 406

Answer 86

B. The lunate bone is the most commonly dislocated bone. Displacement is always anteriorly. Dislocation of the lunate bone can precipitate the signs associated typically with carpal tunnel syndrome. GAS 752-754; GA 392, 394, 422

Answer 87

D. A cervical rib (found at C7) typically causes thoracic outlet syndrome, which is a condition characterized by weak muscle tone in the hand and loss of radial pulse when the upper limb is abducted above the shoulder. The mechanism of injury with the gun being fi red overhead suggests a lower trunk injury to the brachial plexus. The axillary artery supplies the shoulder muscles, and there is no loss of function to these muscles. The upper trunk of the brachial plexus also supplies innervation to the shoulder muscles, which are unaffected based on the patient’s presenting abnormalities. The subclavian artery is located anterior to the brachial plexus until it separates the cords as it passes under the clavicle. The brachiocephalic artery and lower trunk of the brachial plexus is only partially correct; the brachiocephalic artery is not directly associated with the brachial plexus due to its location at the midline of the body behind the sternum. GAS 700-709; GA 61, 369-371

Answer 88

A. A synarthrosis joint is a fi brous connection that allows minimal to no movement. In this case, virtually no movement is allowed by the interosseous membrane joint between the radius and ulna. Symphysis joints are permanent fi brocartilaginous fusions between two bones; pubic symphysis is an example. Synchondrosis is a temporary joint made of cartilage that transitions to bone typically after growth completes (i.e., epiphyseal plate). Trochoid joints are pivot joints, and the humeral-radial portion of the elbow joint is an example. Ginglymus joints are hinge joints located at the interphalangeal junctions in the hand and foot (PIPs and DIPs). GAS 731, 734-735; GA 396

Answer 89

B. The radial pulse is best located on the anterior forearm (antebrachium) just proximal to the wrist joint. At this point the radial artery travels on the distal radius between the fl exor carpi radialis and brachioradialis tendons. The palmaris longus tendon travels more medially to the radial artery and above the fl exor retinaculum. The fl exor pollicis longus tendon is a deeper structure in the antebrachium and is also located medially to the radial artery. GAS 785; GA 374, 390

Answer 90

B. The radial artery enters the palm through the anatomic snuffbox. The artery then moves on to pierce through the two heads of the fi rst dorsal interosseous muscle and enter the deep aspect of the palm. The fl exor pollicis longus tendon runs on the palmar aspect of the hand and the radial artery runs on the dorsal aspect of the hand before entering the UPPER LIMB 206 deep aspect of the palm, and therefore the radial artery does not run below this tendon. The radial artery does not run between the fi rst and second interosseous muscle and therefore cannot be used as a landmark to identify the artery. Finally, the artery does not run between the fi rst interosseous muscle and the adductor pollicis longus. GAS 781; GA 422

Answer 91

D. The median nerve provides innervation to the fl exor compartment of the forearm; cutaneous innervation of the second, third, and fourth digits and palmar and dorsum aspects of the hand; and innervation of four intrinsic hand muscles: fi rst and second lumbricals, abductor pollicis brevis, opponens pollicis, and fl exor pollicis brevis. The thenar compartment contains the muscle abductor pollicis brevis, opponens pollicis, and fl exor pollicis brevis, and these muscles are innervated by the recurrent branch of the median nerve. The patient has weakening of the fi rst two lumbricals and not simply the thenar muscles, so the median nerve is most likely to be compressed. Another indication that the median nerve is compressed is the vigorous shaking of the wrist. Because the median nerve traverses the carpal tunnel, carpal tunnel compression could lead to this action on part of the patient. The ulnar nerve provides innervation for part of the fl exor digitorum profundus and fl exor carpi ulnaris. These muscles are not weakened in this patient. The radial nerve provides cutaneous supply to the dorsum of the hand and forearm as well as extensor muscles of the forearm. The posterior interosseous nerve is a branch of the radial nerve and provides innervation of the extensor muscles in the forearm. GAS 724-731; GA 361

Answer 92

B. Radial nerve at the distal third of the humerus. The patient can extend his forearm, which suggests that the triceps muscle is not weakened. Supination appears to be weak along with hand grasp and wrist drop. This would indicate that part of the radial nerve has been lost below the innervation of the triceps and above the branches to the supinator and extensors in the forearm. However, sensation on the forearm and hand is intact, indicating that the superfi cial branch of the radial nerve is intact. The superfi cial branch of the radial nerve divides from the deep radial nerve at the distal third of the humerus. The posterior cord of the brachial plexus is responsible for providing innervation of the axially and radial nerves. This patient does have some radial nerve innervation and no loss of axillary nerve function. The patient does not have weakened adduction of the wrist, indicating that the ulnar nerve is not injured. If both the radial and musculocutaneous nerves are injured, supination would not be possible as the supinator muscle and biceps provide supination of the forearm. GAS 750; GA 376

Answer 93

B. The posterior interosseous nerve is an extension of the deep branch of the radial nerve. It is responsible for innervation of several muscles in the extensor compartment of the posterior aspect of the forearm, including extension of the metacarpophalangeal joints. The posterior interosseous nerve courses laterally around the radius and passes between the two heads of the supinator muscle and is thus likely to be compressed by a hematoma between the fractured radius and the supinator muscle. Though the radial nerve gives rise to the posterior interosseous nerve, this answer choice is too vague and would not indicate the precise injured branch of the radial nerve. Both the deep branch of the ulnar nerve and the median nerve traverse the medial and anteromedial aspect of the arm, respectively. These nerves primarily supply the fl exor compartment of the arm. The anterior interosseous nerve is a branch of the median nerve and supplies the fl exor digitorum profundus, fl exor pollicis longus, and the pronator quadratus. GAS 750; GA 403

Answer 94

A. The superior trunk of the brachial plexus includes C5 and C6, which give rise to the suprascapular nerve, which innervates the supraspinatus muscle. The supraspinatus muscle is the primary muscle involved in abduction of the arm from 0 ° to 15 ° . The deltoid muscle, supplied primarily by C5, abducts the arm from 15 degrees to 90 degrees. The middle trunk is just C7 and has nothing to do with the muscle involved in initial abduction of the arm. The inferior trunk is C8-T1 and does not supply the supraspinatus muscle; therefore, it is not the right answer. The cords are distal to the branching of the supraspinatus muscle; therefore, neither lateral cord nor medial cord is the correct answer. GAS 700-709; GA 361, 369-371

Answer 95

C. The radial nerve acts to extend the forearm at the elbow. This nerve is derived from all the roots of the brachial plexus C5 to T1. None of the other answers include all the roots and are therefore incorrect. GAS 700-709; GA 361, 369-371

Answer 96

A. The suprascapular artery arises as a major branch of the thyrocervical trunk from the subclavian artery. It has rich anastomoses with the circum- fl ex scapular artery and could provide essential blood supply to the scapula. The dorsal scapular artery would be lost with the graft. None of the other vessels listed is in position to provide adequate supply to the scapula. GAS 696, 697; GA 366, 368

Answer 97

C. The scaphoid and lunate carpal bones are in closest articulation with the radius, which is fractured in a Colles’ fracture; therefore, they would most likely be disrupted or fractured. The other carpal bones listed do not have direct contact with the radius and have a more distal location; therefore, they would not be as likely to be injured with a Colles’ fracture. GAS 734; GA 392

Answer 98

C. This type of dislocation is common in children and results when the radius is dislocated and slips out from the anular ligament, which holds it in place, articulating with the ulna and the capitulum of the humerus. In adults the anular ligament has a good “grip” at the radial neck, but in young children the radial head is not fully developed, leading to an indistinct neck. Compression of the median nerve is not likely due to its medial position in the cubital fossa. The radius does not articulate with the trochlea of the humerus; the ulna articulates at this position. The ulna is not likely to be dislocated because it is more stable than the radius, which has only the anular ligament for its support. The radial nerve does not pass behind the medial epicondyle; rather, the ulnar nerve does this, so this is not the correct answer. GAS 735; GA 391

Answer 99

C. Injury to the radial nerve can be caused by a blow to the midhumeral region since the nerve winds around the shaft of the humerus. The symptoms described include the loss of wrist and fi nger extension and a loss of sensation in an area of skin supplied by the radial nerve. GAS 751; GA 380

Answer 100

A. The ulnar nerve innervates the dorsal and palmar interossei, which act to abduct and adduct the fi ngers and assist the lumbricals in their actions of fl exing the metacarpophalangeal joints and extending the interphalangeal joints. The recurrent branch of the median nerve innervates the thenar muscle group that functions in the movement of the thumb. The radial and musculocutaneous nerves do not innervate any muscles in the hand. The anterior interosseous innervates the fl exor pollicis longus and the pronator quadratus. GAS 770-771; GA 417

Answer 101

C. The triceps brachii muscle is innervated by the radial nerve (primarily C7), which comes off C5 to T1 spinal nerves. Because the patient’s only motor defi cit involves the triceps brachii muscles, one can rule out C5 and C6, which supply fi bers to the axillary, musculocutaneous, and upper subscapular nerves. Damage to either of these roots would result in additional motor defi cits of the shoulder and fl exor compartment of the arm. One can also rule out C8-T1 because these roots form the medial pectoral nerve and the medial brachial and antebrachial cutaneous nerves. Damage to these roots would result in loss of pectoral muscle function and cutaneous sensation over the medial surface of the upper limb. GAS 700-709; GA 361, 369-371

Answer 102

D. Mallet fi nger, also known as baseball fi nger, is a deformity in which the fi nger will be permanently fl exed at the distal interphalangeal joint, due to avulsion of the insertion of the extensor tendon at the distal phalanx. GAS 760; GA 392, 394, 422

Answer 103

B. Injury to the superior trunk of the brachial plexus can damage nerve fi bers going to the suprascapular, axillary, and musculocutaneous nerves. Damage to the suprascapular and axillary nerves causes impaired abduction and lateral rotation of the arm. Damage to the musculocutaneous nerve causes impaired fl exion of the forearm. A winged scapula would be caused by damage to the long thoracic nerve. The long thoracic nerve is formed from spinal cord levels C5, C6, and C7, so the serratus anterior muscle would be weakened from the damage to C5 and C6, but the muscle would not be completely paralyzed. The intrinsic muscles of the hand are innervated by the ulnar nerve, which would most likely remain intact. Paraesthesia in the medial aspect of the arm would be caused by damage to the medial brachial cutaneous nerve (C8- T1; inferior trunk). Loss of sensation on the dorsum of the hand would be caused by damage to either the ulnar or radial nerves (C6 to T1). GAS 700-709; GA 361, 369-371

Answer 104

D. The supinator muscle attaches to the radius proximally and when fractured would cause a lateral deviation. The pronator teres originates on the medial epicondyle and coronoid process of the ulna and inserts on the middle of the lateral side of the radius, pulling the radius medially below the fracture. Pronator quadratus originates on the anterior surface of the distal ulna and inserts on the anterior surface of the distal radius, pulling the radius medially. Brachioradialis originates on the lateral supracondylar ridge of the humerus and inserts at the base of the radial styloid process, far below the fracture. Brachialis originates in the lower anterior surface of the humerus and inserts in the coronoid process and ulnar tuberosity, hence not causing an action on the radius. GAS 715; GA 379

Answer 105

A. Lymph from the lateral side of the hand drains directly into humeral (epitrochlear) nodes then to the central (axillary) nodes. Pectoral nodes receive lymph mainly from the anterior thoracic wall, including most of the breast. Subscapular nodes receive lymph from the posterior aspect of the thoracic wall and scapular region. Parasternal nodes receive lymph from the lower medial quadrant of the breast. GAS 710; GA 381

Answer 106

C. Compartment syndrome is characterized by increased pressure within a confi ned space by a fascial compartment, which impairs blood supply, resulting in paleness. Venous thrombosis would not cause pain but could cause death from a pulmonary embolism. Thoracic outlet syndrome affects nerves in the brachial plexus and the subclavian artery and blood vessels between the neck and the axilla, far above the cast. Raynaud’s disease affects blood fl ow to the limbs when they are exposed to temperature changes or stress. The fracture at the radial groove probably resulted in a radial nerve injury but would not be responsible for these symptoms. GAS 744; GA 381

Answer 107

E. The deep branch of the ulnar nerve arises at the level of the pisiform bone and passes between the pisiform and the hook of the hamate, hence the ulnar is the nerve most likely to be injured in this patient. The median nerve enters the forearm between the humeral and ulnar heads of the pronator teres muscle then becomes superfi cial near the wrist. The recurrent median enters the palm through the carpal tunnel. The radial nerve divides into superfi cial and deep branches when it enters the cubital fossa. GAS 771; GA 417

Answer 108

A. The supraspinatus initiates abduction of the arm during the fi rst 15 ° of abduction; palpation of the tendon during this phase would result in pain from a tendinopathy of the supraspinatus. GAS 678; GA 361, 364

Answer 109

A. The hallmark fracture caused by a fall on an outstretched hand is a scaphoid-lunate fracture; the scaphoid and lunate are the two wrist bones most proximal to the styloid process of the radius. All the other wrist bones are less likely to be affected by this injury. GAS 786; GA 392

Answer 110

C. Bennett’s fracture is a carpometacarpal fracture at the base of the thumb. Smith’s fracture is also called a reverse Colles’ fracture and is caused when the distal fragment of the radius angles forward. Colles’ fracture is also called “silver fork deformity” because the distal fragment is displaced posteriorly. Boxer’s fractures of the necks of metacarpal bones are fractures to the fi ngers. A scaphoid fracture would be indicated by pain in the anatomical snuffbox. GAS 756; GA 392

Answer 111

A. Interestingly, “gamekeeper’s thumb” was a term coined because this injury was most commonly associated with Scottish gamekeepers who, it is said, killed small animals such as rabbits by breaking their necks between the ground and the gamekeeper’s thumb and index fi nger. The resulting valgus force on the abducted MCP joint caused injury to the ulnar collateral ligament. These days this injury is more commonly seen in skiers who land awkwardly with their hand braced on a ski pole, causing the valgus force on the thumb as is seen in this patient. Whereas the term “skier thumb” is sometimes used, “gamekeeper’s thumb” is still in common usage. Bennett fracture is a fracture at the base of the metacarpal of the thumb. Scaphoid fracture occurs after a fall on an outstretched hand, involving the scaphoid and lunate bone. Colles’ fracture is also called silver fork deformity because the distal fragment of the radius is displaced posteriorly. Boxer’s fracture is a fracture of the necks of the second and third (and sometimes the fi fth) metacarpals. Smith’s fracture is also called a reverse Colles’ fracture and is caused when the distal radius is fractured and the distal radial fragment is angled forward. GAS 755; GA 395

Answer 112

B. The biceps brachii refl ex involves C5 and C6 spinal nerves. C5 provides the motor component; C6 the afferent side of the refl ex arc. GAS 700-709; GA 361, 369-371

Answer 113

B. The brachioradialis refl ex is performed by tapping the tendon of the brachioradialis muscle. The refl ex involves spinal nerves C5, C6, and C7. The major contribution is from C6. GAS 700-709; GA 361, 369-371

Answer 114

D. Volkmann’s contracture is a fl exion deformity of the fi ngers and sometimes the wrist from an ischemic necrosis of the forearm fl exor muscles. Bennett’s fracture is a fracture at the base of the metacarpal of the thumb. Scaphoid fracture occurs after a fall on an outstretched hand and involves the scaphoid and lunate bones. Colles’ fracture is also called silver fork deformity because the distal fragment of the radius is displaced posteriorly. Boxer’s fracture is a fracture of the necks of the second and third (and sometimes the fi fth) metacarpals. Smith’s fracture is also called a reverse Colles’ fracture and is caused when the distal radius is fractured, with the radial fragment angled forward. GAS 762; GA 398

Answer 115

D. The ulnar nerve enters the forearm by passing between the two heads of the fl exor carpi ulnaris and descends between and innervates the fl exor carpi ulnaris and fl exor digitorum profundus (medial half) muscles. It enters the hand superfi cial to the fl exor retinaculum and lateral to the pisiform bone, where it is vulnerable to damage and provides the deep ulnar branch. The deep branch of the radial nerve arises proximally in the forearm. GAS 771; GA 417

Answer 116

B. “Benediction attitude” of the hand with the index and long fi ngers straight and the ring and little fi ngers fl exed is caused by an injury to the median nerve. The long fl exors of the digits are supplied by the median nerve; the unopposed radial nerve and deep ulnar nerve supply the extensors of the digits 1–3, causing them to be in the extended position. Digits 4 and 5 are slightly fl exed, because the fl exors of the PIP joints are supplied by the ulnar nerve. GAS 724; GA 371, 376

Answer 117

A. The Allen test involves compression of the radial and ulnar arteries at the wrist with the fi ngers fl exed tightly. Pressure is then released on either vessel successively to determine the degree of supply to the hand by either vessel and the patency of the anastomoses between them. The usefulness of the radial artery for bypass can thereby be assessed. The other tests have nothing to do with the patency of the radial artery. GAS 770; GA 400

Answer 118

E. The ulnar nerve enters the hand superfi cial to the fl exor retinaculum and lateral to the pisiform bone and innervates all the interossei via the deep branch. These muscles are responsible for adduction and abduction of the fi ngers. Flexion of the fi ngers is spared because the fl exor digitorum superfi cialis and most of the fl exor digitorum profundus are innervated by the median nerve, which is unaffected by this injury. Had the median nerve been compressed in the carpal tunnel, one would have diffi culty with motion of the thumb as a result of a lack of innervation of the thenar muscles. An injury of the radial nerve in the arm will result in extension defi cit in the forearm and hand. GAS 744; GA 417