This practice set contains high-yield board review questions covering key concepts in 7. Hand and Wrist. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 3321
Topic: 7. Hand and Wrist
During a deep dissection of the palm for a complex tumor resection, the surgeon encounters the deep palmar arch. This vascular structure is primarily formed by the continuation of which artery, and it typically passes deep to which structure?
Correct Answer & Explanation
. Radial artery; flexor tendons
Explanation
The deep palmar arch is primarily formed by the terminal continuation of the radial artery and is completed medially by the deep palmar branch of the ulnar artery. It lies deep to the flexor tendons and their synovial sheaths, and superficial to the bases of the metacarpals and the interosseous muscles. In contrast, the superficial palmar arch is primarily formed by the ulnar artery and lies superficial to the flexor tendons.
Question 3322
Topic: 7. Hand and Wrist
A cyclist presents with weakness of the intrinsic hand muscles and numbness limited to the volar ulnar aspect of the hand. You suspect entrapment of the ulnar nerve within Guyon's canal. At which specific anatomic landmark does the deep motor branch of the ulnar nerve diverge from the superficial sensory branch?
Correct Answer & Explanation
. Just distal to the pisiform and proximal to the hook of hamate
Explanation
Guyon's canal is divided into three zones. Zone 1 is proximal to the bifurcation of the ulnar nerve. The bifurcation into the deep motor branch and superficial sensory branch occurs just distal to the pisiform and proximal to the hook of hamate. The deep motor branch then dives between the abductor digiti minimi and flexor digiti minimi origins (Zone 2), while the sensory branch continues superficially (Zone 3).
Question 3323
Topic: 7. Hand and Wrist
A 30-year-old carpenter sustains a volar laceration over the proximal phalanx of his index finger (Zone II). Which of the following accurately describes the relationship of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons at the level of the A2 pulley?
Correct Answer & Explanation
. The FDP bifurcates to allow the FDS to pass superficial to it.
Explanation
At the level of the A2 pulley (proximal phalanx, zone II), the flexor digitorum superficialis (FDS) tendon splits to form Camper's chiasm. The two slips wrap around the flexor digitorum profundus (FDP) tendon to insert on the volar aspect of the middle phalanx. The FDP passes through this split to continue distally to the distal phalanx.
Question 3324
Topic: Nerve & Tendon
During the volar (Henry) approach to the proximal radius, the surgeon develops an internervous plane to safely expose the underlying structures. Which of the following describes the correct proximal internervous interval and the respective nerve supply to the bordering muscles?
Correct Answer & Explanation
. Brachioradialis (radial nerve) and pronator teres (median nerve)
Explanation
The proximal portion of the volar (Henry) approach to the radius utilizes the internervous plane between the brachioradialis (innervated by the radial nerve) radially and the pronator teres (innervated by the median nerve) ulnarly. Distally, the interval transitions to between the brachioradialis and the flexor carpi radialis (median nerve). It is critical to identify and ligate the recurrent radial artery branches in this plane to safely mobilize the brachioradialis radially.
Question 3325
Topic: 7. Hand and Wrist
During a late anatomical repair of a complex flexor tendon injury, the surgeon must evaluate the lumbrical muscles to prevent a 'lumbrical plus' finger deformity. Which of the following statements correctly describes the normal anatomy and innervation of the lumbrical muscles in the hand?
Correct Answer & Explanation
. They originate from the flexor digitorum profundus tendons; the radial two are unipennate and innervated by the median nerve.
Explanation
The lumbricals originate from the tendons of the flexor digitorum profundus (FDP). The first and second (radial) lumbricals are unipennate and innervated by the median nerve. The third and fourth (ulnar) lumbricals are bipennate and innervated by the deep branch of the ulnar nerve. They insert onto the radial side of the extensor expansions, enabling flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal (IP) joints.
Question 3326
Topic: Nerve & Tendon
A 30-year-old female presents with an isolated laceration to the ulnar nerve at the level of the wrist (Zone 1 of Guyon's canal). Clinical examination demonstrates complete anesthesia over the volar small finger and ulnar half of the ring finger. Surprisingly, she retains strong, normal motor function in all the dorsal and volar interossei. Which of the following neural anatomic variants best explains this clinical finding?
Correct Answer & Explanation
. Martin-Gruber anastomosis
Explanation
The Martin-Gruber anastomosis is a communicating nerve branch from the median nerve (or anterior interosseous nerve) to the ulnar nerve in the proximal forearm. It typically carries motor fibers that ultimately innervate the intrinsic muscles of the hand (often those usually supplied by the ulnar nerve). Consequently, a complete ulnar nerve laceration at the wrist may not result in complete intrinsic paralysis if these bypassing motor fibers re-entered the ulnar nerve distal to the injury, or if they travel with the median nerve entirely to the palm. Note that the Riche-Cannieu anastomosis occurs in the palm between the deep branch of the ulnar nerve and the recurrent motor branch of the median nerve.
Question 3327
Topic: 7. Hand and Wrist
A 35-year-old male presents with an inability to actively extend his fingers at the metacarpophalangeal joints following a proximal radius fracture. Wrist extension is preserved but deviates radially. Sensation in the hand is completely normal. Where is the most likely site of nerve compression or injury?
Correct Answer & Explanation
. At the Arcade of Frohse
Explanation
The Arcade of Frohse is the most common site for Posterior Interosseous Nerve (PIN) compression or injury. The PIN is a motor branch of the radial nerve. Injury leads to loss of extension of the digits at the MCP joints and thumb extension/abduction. Wrist extension is preserved (since extensor carpi radialis longus and brevis are innervated by the radial nerve proximal to the PIN branch) but deviates radially due to the loss of the extensor carpi ulnaris (innervated by the PIN). The ligament of Struthers and pronator teres are associated with median nerve compression.
Question 3328
Topic: Nerve & Tendon
Following a complete laceration of the median nerve at the level of the antecubital fossa, a patient retains some motor function of the intrinsic muscles of the hand normally innervated by the ulnar nerve. Electrodiagnostic testing confirms an anomalous nerve communication. The Martin-Gruber anastomosis most commonly involves nerve fibers crossing from the:
Correct Answer & Explanation
. Median nerve to the ulnar nerve in the forearm
Explanation
The Martin-Gruber anastomosis is an anatomical variant present in approximately 15% to 20% of individuals. It is defined by nerve fibers crossing from the median nerve (or its anterior interosseous branch) to the ulnar nerve in the proximal forearm. This connection allows median nerve motor fibers to innervate intrinsic hand muscles (most commonly the first dorsal interosseous) that are traditionally supplied by the ulnar nerve.
Question 3329
Topic: Nerve & Tendon
A 28-year-old avid cyclist presents with significant weakness of the interosseous muscles and adductor pollicis, but normal sensation over both the volar and dorsal aspects of the little finger. Compression of the ulnar nerve is suspected. At which of the following anatomic locations is the compression most likely occurring?
Correct Answer & Explanation
. At the hook of the hamate in the deep palmar space (Zone II)
Explanation
The patient exhibits an isolated motor deficit of the ulnar nerve with preserved sensation. Ulnar nerve compression at Guyon's canal is classified into three zones. Zone I compression affects both motor and sensory branches. Zone II contains only the deep motor branch, which passes between the hook of the hamate and the pisiform, and compression here yields isolated motor deficits. Zone III contains only the superficial sensory branch. A cubital tunnel syndrome would typically present with both sensory and motor deficits.
Question 3330
Topic: 7. Hand and Wrist
A 35-year-old woman requires a dorsal approach to the wrist for a proximal row carpectomy. The surgeon meticulously releases the extensor retinaculum over the third dorsal compartment to protect its contents. Which structure is contained entirely within this compartment, and around what bony landmark does it pivot?
Correct Answer & Explanation
. Extensor pollicis longus; Lister's tubercle
Explanation
The third dorsal compartment of the wrist contains a single tendon: the extensor pollicis longus (EPL). The EPL tendon takes a sharp, angled turn around Lister's tubercle (the dorsal tubercle of the radius), using it as a fulcrum to direct its vector towards the thumb.
Question 3331
Topic: 7. Hand and Wrist
A 40-year-old female presents with a deep space infection of the hand after a puncture wound to the palmar aspect of her index finger. The infection has spread proximally from the flexor tendon sheath. Which of the following anatomical structures serves as the primary conduit for this spread into the deep palmar spaces?
Correct Answer & Explanation
. The lumbrical canal
Explanation
The lumbrical canals act as potential anatomic spaces linking the digits to the deep palmar spaces. An infection in the flexor tendon sheath (purulent flexor tenosynovitis) can rupture proximally into the lumbrical canal. From there, infections from the index finger typically spread into the thenar space, whereas those from the middle, ring, and small fingers spread to the midpalmar space.
Question 3332
Topic: 7. Hand and Wrist
A 24-year-old man sustains a fall onto an outstretched hand. Radiographs demonstrate a fracture through the proximal pole of the scaphoid. He is informed that this specific fracture pattern is at a high risk for avascular necrosis due to the unique retrograde blood supply of the scaphoid. The predominant blood supply to the scaphoid enters at which location and originates from which artery?
Correct Answer & Explanation
. Dorsal ridge; radial artery
Explanation
The primary blood supply to the scaphoid is retrograde. The major arterial supply (70-80%) comes from the dorsal carpal branch of the radial artery, which enters the scaphoid at the dorsal ridge (near the waist) and supplies the proximal pole in a retrograde fashion. A smaller volar branch supplies the distal 20-30%. Fractures through the proximal pole are highly prone to avascular necrosis due to interruption of this retrograde flow.
Question 3333
Topic: 7. Hand and Wrist
De Quervain's tenosynovitis involves the first dorsal extensor compartment of the wrist. During surgical release, the surgeon must carefully decompress all subcompartments. Which of the following describes the most common anatomical arrangement of the tendons within the first dorsal compartment?
Correct Answer & Explanation
. The APL frequently has multiple tendon slips, while the EPB is usually a single tendon.
Explanation
In the first dorsal compartment, the Abductor Pollicis Longus (APL) typically has multiple tendon slips (often 2 to 4), while the Extensor Pollicis Brevis (EPB) is generally a single tendon. A distinct intracompartmental septum separating the APL and EPB is found in about 40-60% of patients, and failure to recognize and release it is a primary cause of persistent symptoms postoperatively. The EPB inserts onto the base of the proximal phalanx, and the superficial branch of the radial nerve runs superficial to the compartment.
Question 3334
Topic: 7. Hand and Wrist
A 45-year-old avid cyclist reports progressive numbness in the volar aspect of the small finger and ulnar half of the ring finger, along with weakness in finger abduction. Suspecting compression of the ulnar nerve at the wrist, the surgeon plans a release of Guyon's canal. Which of the following structures forms the true floor of Guyon's canal?
Correct Answer & Explanation
. Transverse carpal ligament
Explanation
Guyon's canal (the ulnar tunnel) contains the ulnar nerve and artery. Its boundaries are defined as follows: the roof is formed by the volar carpal ligament and the palmaris brevis muscle; the floor is formed by the transverse carpal ligament (flexor retinaculum) and the pisohamate ligament; the ulnar border is the pisiform; and the radial border is the hook of the hamate. Compression here typically affects ulnar nerve function without affecting the median nerve.
Question 3335
Topic: Nerve & Tendon
A 32-year-old competitive cyclist presents with intrinsic muscle weakness in his right hand. He has noticeable clawing of the ring and small fingers but maintains intact sensation over the hypothenar eminence and the palmar aspect of the ulnar digits. At which anatomical zone of Guyon's canal is the ulnar nerve most likely compressed?
Correct Answer & Explanation
. Zone 2 (deep motor branch)
Explanation
Guyon's canal is divided into three zones. Zone 1 contains both motor and sensory fibers; compression here causes mixed deficits. Zone 2 surrounds the deep motor branch; compression here causes isolated motor weakness of the ulnar-innervated intrinsic hand muscles. Zone 3 contains the superficial sensory branch; compression here yields isolated sensory deficits. The patient's intact sensation but isolated intrinsic weakness points to a Zone 2 compression.
Question 3336
Topic: Nerve & Tendon
When performing the volar (Henry) approach to the proximal radius for fracture fixation, the deep dissection requires careful positioning of the forearm to protect a major nerve. The forearm should be placed in full supination to protect which of the following structures?
Correct Answer & Explanation
. Posterior interosseous nerve
Explanation
During the anterior (Henry) approach to the proximal radius, the forearm is supinated during the deep dissection. Supination rotates the bicipital tuberosity and the insertion of the supinator muscle laterally. This displaces the posterior interosseous nerve (PIN), which runs within the supinator muscle, further away from the medial surgical field, thus reducing the risk of iatrogenic injury.
Question 3337
Topic: Wrist & Carpus
The Triangular Fibrocartilage Complex (TFCC) is the major stabilizer of the distal radioulnar joint (DRUJ). Which specific component of the TFCC provides the primary restraint to dorsal translation of the distal radius relative to the ulna during active forearm pronation?
Correct Answer & Explanation
. Dorsal radioulnar ligament
Explanation
The dorsal and volar radioulnar ligaments are the primary stabilizers of the DRUJ. During forearm pronation, the radius crosses over the ulna, and the dorsal radioulnar ligament stretches over the ulnar head and tightens. Thus, the dorsal radioulnar ligament prevents dorsal subluxation of the radius (or volar subluxation of the ulna) in pronation. Conversely, the volar radioulnar ligament tightens in supination.
Question 3338
Topic: Nerve & Tendon
A 28-year-old carpenter sustains a volar laceration over his dominant index finger, resulting in complete transection of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons in Zone II. While retrieving the retracted FDP tendon, the surgeon visualizes the attached lumbrical muscle. Which of the following statements accurately describes the typical anatomy of the first lumbrical?
Correct Answer & Explanation
. It is unipennate, originates from the radial side of the index finger FDP tendon, and is innervated by the median nerve.
Explanation
The lumbrical muscles are unique in that they originate from tendons (the flexor digitorum profundus) and insert onto the extensor expansions of the digits. The first and second lumbricals (acting on the index and middle fingers) are unipennate, originate strictly from the radial sides of their respective FDP tendons, and are innervated by the median nerve. Conversely, the third and fourth lumbricals are bipennate, originate from the adjacent sides of the FDP tendons, and are innervated by the deep branch of the ulnar nerve.
Question 3339
Topic: Nerve & Tendon
A 20-year-old collegiate baseball pitcher undergoes ulnar collateral ligament (UCL) reconstruction using the modified Jobe (figure-of-8) technique.
Compared to the docking technique, the modified Jobe technique is associated with a higher incidence of which of the following postoperative complications?
Correct Answer & Explanation
. Ulnar neuropathy
Explanation
The modified Jobe (figure-of-8) technique requires more extensive dissection and handling of the ulnar nerve, often involving obligatory ulnar nerve transposition. Consequently, it has historically been associated with a higher rate of postoperative ulnar neuropathy compared to the docking technique, which typically allows the ulnar nerve to be left in situ or involves less manipulation.
Question 3340
Topic: Nerve & Tendon
A 19-year-old collegiate baseball pitcher is undergoing ulnar collateral ligament (UCL) reconstruction utilizing a palmaris longus autograft. Following the procedure, what is the most commonly reported postoperative complication?
Correct Answer & Explanation
. Ulnar neuropathy
Explanation
Ulnar neuropathy is the most common complication following UCL reconstruction, reported in up to 10-15% of cases. It can manifest as transient numbness, tingling, or weakness in the ulnar nerve distribution. Management of the ulnar nerve during the procedure (e.g., in situ decompression versus subcutaneous or submuscular transposition) remains debated, but neuropathy remains the leading complication regardless of technique.
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