Anatomy Practice questions

Following a complicated hip replacement surgery, your 77-year-old patient is having difficulty walking up stairs although he can walk fairly normally on flat surfaces. You suspect the surgery likely injured which of the following nerves?

-Inferior gluteal The answer is inferior gluteal. The inferior gluteal nerve innervates the gluteus maximus, which is very important for walking uphill and climbing but less critical for level walking.

Compression of the median nerve in the carpal tunnel affects which hand muscle(s)?

Flexor pollicis brevis The recurrent branch of the median nerve innervates the thenar compartment of the hand, including flexor pollicis brevis, abductor pollicis brevis, and opponens pollicis. So, if the median nerve was compressed, all of these muscles might be affected. The dorsal interossei, palmar interossei, and opponens digiti minimi are all muscles of the hand which are innervated by the deep branch of the ulnar nerve. Flexor pollicis longus is innervated by the median nerve, but it is a forearm muscle which is proximal to the carpal tunnel. Therefore, it would not be affected by compressing the median nerve in the carpal tunnel.

During an industrial accident, a sheet metal worker lacerates the anterior surface of his wrist at the junction of his wrist and hand. Examination reveals no loss of hand function, but the skin on the thumb side of his palm is numb. Branches of which nerve must have been severed?

The median nerve provides sensory innervation to the skin of the radial 3.5 fingers of the palm. So, the patient's loss of cutaneous sensation is suggestive of a median nerve injury. The location of the injury also implies that there has been an injury to the median nerve--this nerve enters the hand by crossing under the flexor retinaculum on the anterior side of the wrist. The lateral and medial antebrachial cutaneous nerves provide cutaneous innervation to the anterior side of the forearm--the symptoms here are not consistent with an injury to these nerves. The radial nerve innervates the radial side of the dorsum of the hand but does not innervate the palmar side of the hand. The ulnar nerve innervates the medial (ulnar) side of both the dorsum and palm of the hand.

The police bring in a murder suspect who has been in a gunfight with a police officer. The suspect was struck by a bullet in the arm; his median nerve has been damaged. Which of the following symptoms is likely produced by this nerve damage?

-Ape hand The answer is ape hand. Injury to the median nerve produces the ape hand (a hand with the thumb permanently extended). Injury to the radial nerve results in loss of wrist extension, leading to wrist drop. Damage to the upper trunk of the brachial plexus produces waiter's tip hand. A claw hand and flattening of the hypothenar eminence or atrophy of the hypothenar muscles result from damage to the ulnar nerve.

A 27-year-old baseball player is hit on his forearm by a high-speed ball during the World Series, and the muscles that form the floor of the cubital fossa appear to be torn. Which of the following groups of muscles have lost their functions?

-Brachialis and supinator The answer is brachialis and supinator. The brachialis and supinator muscles form the floor of the cubital fossa. The brachioradialis and pronator teres muscles form the lateral and medial boundaries, respectively. The pronator quadratus is attached to the distal ends of the radius and the ulna.

A college student goes to the student health center complaining that he badly hurt his right hand during an intramural rugby game. Initial examination indicates a fracture dislocation of the distal phalanx of the thumb. Further, the normally distinct medial wall of the anatomical snuff box is not apparent. Which of the following muscle tendons is most likely ruptured in this injury?

-Extensor pollicis longus The answer is the extensor pollicis longus. The extensor pollicis longus inserts into the distal phalanx of the thumb. Its tendon forms what is normally the pronounced medial wall of the anatomical snuff box on the lateral side of the wrist. The combination of specific fracture point plus loss of definition of the medial wall of the snuff box indicate damage to this muscle tendon. The abductor pollicis longus and extensor pollicis brevis muscles, which form the lateral wall of the snuff box, insert into the first metacarpal bone and proximal phalanx of the thumb, respectively. Abductor pollicis brevis is incorrect. The abductor pollicis brevis is one of the small muscles forming the thenar eminence. It attaches to the proximal phalanx of the thumb and does not form a boundary of the anatomical snuff box. Extensor carpi radialis longus is incorrect. The extensor carpi radialis longus attaches to the posterior base of the second metacarpal bone. It lies medial to the anatomical snuff box. Extensor indicis is incorrect. The long tendon of the extensor indicis runs into the dorsal (extensor) expansion of the second digit. It is located medial to the snuff box. Flexor pollicis longus is incorrect. The flexor pollicis longus does insert into the distal phalanx of the thumb. However, it emerges from the anterior compartment of the forearm and runs through the anterior (palmar) aspect of the hand to its insertion. It is not related to the anatomical snuff box.

As part of a physical examination to evaluate muscle function in the hand, a physician holds the proximal interphalangeal joint of his patient's index finger in the extended position and instructs him to try to flex the distal interphalangeal joint, as shown below. Which of the following muscles is the doctor testing?

-Flexor digitorum profundus (FDP) The answer is flexor digitorum profundus (FDP). Flexion of the distal interphalangeal joint in digits 2 to 5 is produced by the FDP. The actions of this muscle are being tested in this illustration. Extensor indicis is incorrect. The extensor indicis extends the index finger (digit 2), which enables this finger to extend independent of the other fingers. Because the muscle arises from the distal third of the ulna and the interosseous membrane, it also acts to extend the hand at the wrist. The extensor indicis muscle is not involved in flexion of the distal interphalangeal joint, which is being tested in this patient. First lumbrical is incorrect. The first lumbrical muscle extends the interphalangeal joints of the index (second) finger and flexes the metacarpophalangeal joint of the same finger. The first lumbrical is an intrinsic hand muscle that arises off the tendon of the flexor digitorum profundus and inserts into the extensor expansion of the index finger. This muscle is not involved with flexion of the distal interphalangeal joint. First dorsal interosseous is incorrect. The primary movement of the first dorsal interosseous is abduction of the index finger. However, because it inserts into the extensor expansion, it also extends the interphalangeal joints of the index (second) finger and flexes the metacarpophalangeal joint of the same finger. This muscle is not involved with flexion of the distal interphalangeal joint. Flexor digitorum superficialis (FDS) is incorrect. The FDS acts at the proximal interphalangeal joint in digits 2 to 5 and influences the distal interphalangeal joint by binding the tendons of the FDP. However, when the proximal interphalangeal joint is held in extension, the influence of the FDS is eliminated, allowing testing of only the FDP.

Young Johnny was playing on the playground at school when he fell and struck his arm against the swing set. He ran to the school nurse, complaining of which of the following conditions as a result of injuring the radial nerve in the spiral groove of the humerus?

-Inability to extend the hand The answer is inability to extend the hand. The radial nerve innervates the extensor muscles of the hand; hence, Johnny could not extend his hand because of an injury to the radial nerve. Numbness would occur on the posterior aspects of the arm and forearm because of an injury to the radial nerve. The skin on the medial side of the forearm is innervated by the medial antebrachial cutaneous nerve; thus, numbness over the medial side of the forearm would not occur. The opponens pollicis, pronator teres, and pronator quadratus muscles are innervated by the median nerve. Therefore, inability to oppose the thumb or weakness in pronating the forearm would not occur. The abductors of the arm (deltoid and supraspinatus muscles) are innervated by the axillary nerve and upper trunk of the brachial plexus, respectively.

A 17-year-old boy comes to the emergency room after a hard fall onto the lateral aspect of his left shoulder during a high school basketball game. He complains of generalized pain during shoulder motion. On physical examination, the distal end of the clavicle is prominent and distinctly palpable. Radiological findings confirm the diagnosis of a severe (grade 3) shoulder separation. Which of the following features is a component of this condition?

-Torn coracoclavicular ligament The answer is torn coracoclavicular ligament. "Shoulder separation" describes a dislocation of the acromioclavicular joint. In its most severe form (grade 3), the condition includes a tearing of both the intrinsic acromioclavicular ligament and the extrinsic coracoclavicular ligament. As a result, the scapula separates from the clavicle and falls away due to the weight of the upper limb. Thus, the distal end of the clavicle is prominent. Dislocated head of the humerus is incorrect. Dislocations of the GH joint easily occur inferiorly due to its lack of muscular and ligamentous support. Thus, damage to the axillary nerve often occurs following inferior displacment of the head of humerus from the GH joint. However, the acromioclavicular joint, which is more proximal, was injured in this patient. Dislocations of the glenohumeral joint in other directions are more difficult (but not impossible) because of the support of the rotator cuff muscles (anteriorly and posteriorly) and the coracoacromial arch (superiorly). Fractured clavicleis incorrect. Radiological imaging would have detected a fractured clavicle, but these tests confirmed a shoulder separation and not a fractured clavicle. Dislocated sternal end of the clavicle is incorrect. Due to its intrinsic strength, dislocation of the sternoclavicular (SC) joint is rare. Most dislocations of the SC joint occur in persons less than 25 years of age following a fracture of the epiphysial plate of the clavicle. The epiphysis at the proximal end of the clavicle does not close until approximately age 25. Though this patient was under the age of 25, his injury was localized to the acromioclavicular joint. Torn anterior gleno- humeral (GH) ligament is incorrect. Three GH ligaments reinforce the anterior part of the joint capsule; however, the GH joint was not involved in this patient.

During a violent domestic argument, a young woman slips and falls onto some broken glassware. She sustains a shallow laceration on the front of her right wrist, superficial to the flexor retinaculum. Which of the following structures is most likely to be lesioned in this injury?

-Ulnar nerve The answer is the ulnar nerve. The ulnar nerve crosses the anterior aspect of the wrist, superficial to the flexor retinaculum and just lateral to the pisiform bone. It lies immediately adjacent to the ulnar artery, which is also highly vulnerable in the described injury. This flexor digitorum superficialis tendons crosses the front of the wrist. However, the tendons are located deep to the flexor retinaculum, within the carpal tunnel. The large median nerve passes through the carpal tunnel, deep to the flexor retinaculum, and alongside the flexor digitorum longus tendons. The long tendon of the flexor pollicis longus is another structure that crosses the front of the wrist within the carpal tunnel and deep to the flexor retinaculum. This deep branch of the median nerve runs along the front of the interosseous membrane and ends in the carpus. Its terminal end and articular branches are quite deep to the flexor retinaculum.

A 31-year-old professional baseball pitcher suffers a torn medial collateral ligament of the elbow in his throwing arm. Two weeks later, he undergoes "Tommy John surgery," in which the tendon of the palmaris longus muscle is transplanted into the elbow to reconstruct the damaged ligament. During the operative procedure, the surgeon must be keenly aware of the close relationship of which of the following structures to the medial collateral ligament?

-Ulnar nerve The answer is the ulnar nerve. The ulnar nerve crosses the elbow by passing behind the medial epicondyle of the humerus in close apposition to the medial collateral ligament (ulnar collateral ligament; UCL). The nerve must be treated with care during any reconstructive procedure at the medial side of the elbow. It may be involved in postoperative scar tissue formation, especially if transposed during the procedure. Brachial artery is incorrect. The brachial artery crosses the anterior aspect of the elbow. The vessel lies on the surface of the brachialis muscle and terminates at approximately the neck of the radius. Cephalic vein is incorrect. The cephalic vein is a subcutaneous vessel that crosses the elbow along the anterolateral side of the biceps brachii. It is far removed from the medial collateral ligament. Radial nerve is incorrect. The radial nerve winds around the back of the arm in the spiral (radial) groove of the humerus. The nerve pierces the lateral intermuscular septum and crosses the anterolateral aspect of the elbow between the brachialis and brachioradialis muscles. Ulnar artery is incorrect. The ulnar artery originates in the cubital fossa, anterior to the elbow, at the level of approximately the neck of the radius. It is one of the terminal branches of the brachial artery, and at its origin lies on the front of the tendon of the biceps brachii.

As a result of chronic stress associated with an intense high school weight-lifting program, a 15-year-old boy suffers an avulsion fracture of the greater tubercle of the humerus. In the ER, he displays difficulty initiating abduction of the upper limb. Which of the following muscles was involved in this fracture?

-supraspinatus The answer is supraspinatus. The greater tubercle of the humerus is the insertion site of three (of the four) rotator cuff muscles: supraspinatus, infraspinatus, and teres minor. Avulsion of this structure could result in detachment of any of these rotator cuff muscles, depending upon the size and scope of the fracture. However, the wrestler is unable to initiate abduction of the upper limb, which implies damage to the supraspinatus muscle. Long head of biceps brachii is incorrect. This muscle originates from the supraglenoid tubercle of the scapula and passes between the greater and lesser tubercles of the humerus, in the intertubercular (bicipital) groove. Detachment of the tendon of this muscle causes the biceps brachii to bulge in the anterior arm. Avulsion of the biceps brachii muscle is not related to the greater tubercle of the humerus. Long head of triceps is incorrect. The long head of the triceps brachii muscle originates from the infraglenoid tubercle of the scapula and inserts on the olecranon process of the ulna. It would not be involved in avulsion of the greater tubercle of the humerus.Subscapularis is incorrect. The fourth rotator cuff muscle, subscapularis, inserts onto the lesser tubercle of the humerus, so it would not be directly involved with this avulsion injury.Infraspinatus is incorrect. The infraspinatus muscle does insert onto the middle aspect of the greater tubercle of the humerus; however, damage to this muscle would result in weakness in external rotation at the shoulder joint, not the problems with abduction seen in this patient.

Supination of the hand and forearm would be diminished by loss of radial nerve function. But one very powerful supinator would remain intact and unaffected, namely:

Biceps brachii Biceps brachii supinates the arm, but it is not innervated by the radial nerve--instead, it is innervated by the musculocutaneous nerve. So, it would not be affected by a radial nerve injury. Brachialis is also innervated by the musculocutaneous nerve, but it is only involved with flexing the forearm--it is not a supinator. Brachioradialis flexes the elbow and assists in pronation and supination--it is innervated by the radial nerve and would be paralyzed after a radial nerve injury. Flexor carpi radialis is a flexor, not a supinator--it is innervated by the median nerve. Finally, supinator is innervated by the deep radial nerve.

The victim of multiple shrapnel wounds to the upper limb must have his forearm amputated at midlength. Because of concomitant damage in the patient's arm, the surgeon must ligate the main artery at some point. The best chance of saving collateral circulation to the stump of the forearm would be when the ligature is placed just below which of the following?

Bifurication of the brachial artery The brachial artery bifurcates near the elbow. It forms two branches that become the radial and ulnar arteries. If these arteries were ligated after this bifurcation, there would be a chance at saving collateral circulation to the forearm because the ulnar artery might have already given off its common interosseous branch, which could carry blood to the forearm through the anterior and posterior interosseus arteries. Ligating near the beginning of the brachial artery would stop blood from flowing through the rest of the upper limb. Ligating near the origin of the deep artery, by the origin of the superior ulnar collateral artery, or near the origin of the inferior ulnar collateral artery might preserve enough collateral circulation to supply the elbow. However, there would not be collateral circulation to the forearm. For a better picture of these arterial connections, see Netter Plate 434.

Interruption of the median nerve in the cubital fossa affects what movement(s) of the thumb?

Flexion and opposition The recurrent branch of the median nerve innervates the thenar compartment of the hand. This nerve innervates opponens pollicis, which opposes the thumb, and flexor pollicis brevis, which helps to flex the thumb. So, disrupting the median nerve would impair both flexion and opposition of the thumb.

What muscle is innervated by branches of both the median and ulnar nerves?

Flexor digitorum profundus The median and ulnar nerve both innervate flexor digitorum profundus. Flexor carpi ulnaris is innervated by the ulnar nerve only. Flexor digitorum superficialis and flexor pollicis longus are innervated by the median nerve. Pronator quadratus is innervated by the anterior interosseus nerve, which is a branch of the median nerve.

A worker doing repetitive lifting develops an inflammation in the tendon of origin of the extensor carpi radialis brevis muscle, commonly called "tennis elbow". The focal point of pain would most likely be near which palpable bony landmark?

Lateral epicondyle of the humerus. The extensor carpi radialis brevis muscle originates from the common extensor tendon off the lateral epicondyle of the humerus. So, an injury to this tendon would result in pain near the lateral epicondyle. Tennis elbow is due to the repetitive use of superficial extensor muscles of the forearm--the pain is often felt at the lateral epicondyle and it radiates down the posterior surface of the forearm. None of the other bony landmarks are associated with the common extensor tendon, although the medial epicondyle is the origin of the common flexor tendon.

The anterior interosseous is a branch of which nerve?

Median nerve The anterior interosseous nerve is a branch of the median nerve that provides motor innervation to the deep muscles in the flexor compartment, including flexor pollicis longus, the radial half of flexor digitorum profundus, and pronator quadratus. The other related nerve to think about is the posterior interosseous nerve, which is the terminal branch of the deep radial nerve. It provides sensory innervation to the wrist area.

Structures within the carpal tunnel include the:

Radial and Ulnar bursa The radial bursa and ulnar bursa are both found in the carpal tunnel. These bursae are complex synovial coverings that protect the flexor tendons. The carpal tunnel is formed where the flexor retinaculum spans from the scaphoid and trapezium to the hamate and pisiform, deep and slightly distal to the palmar carpal ligament. This creates a canal that covers the flexor digitorum superficialis tendons, the flexor digitorum profundus tendons, the tendon of flexor pollicis longus, and the median nerve. These tendons in the carpal tunnel are covered by the ulnar and radial bursae. The flexor digitorum superficialis and flexor digitorum profundus tendons are covered by the ulnar bursa, and the tendon of flexor pollicis longus is covered by the radial bursa. So, both bursae are in the carpal tunnel.

A patient is severely limited in extension at the wrist joint after several months in a cast following a Colles fracture. Which joint would be especially important in therapy to regain full extension?

Radiocarpal The radiocarpal joint is the joint commonly known as the wrist joint--it is a condyloid (oval) type of synovial joint that allows for flexion and extension, abduction and adduction, and circumduction. A Colles fracture is a fracture of the distal end of the radius--this is why this sort of break would limit movement between the radius and carpals. The carpometacarpal joint is found between the distal row of carpals and the metacarpals--these joints are mobile for the thumb and little finger, allowing extension, flexion, abduction, and adduction. However, the carpometacarpal joints are quite immobile for the middle three fingers. The distal radioulnar joint is located between the distal ends of the radius and ulna--this joint allows the radius and ulna to rotate around each other during pronation and supination. The midcarpal joint is located between the proximal and distal row of carpals--this joint is important for flexion and extension of the hand. As for the "ulnocarpal joint," the ulna does not articulate with the carpal bones--it articulates with the distal end of the radius only.