Orthopedic Surgery Board Review MCQs: Hand, Wrist & Nerve

Question 1

A 28-year-old male presents with persistent wrist pain 18 months after a scaphoid waist fracture. Imaging reveals a proximal pole nonunion with avascular necrosis (AVN) of the proximal fragment, which measures 4 mm. A previous attempt at fixation with a Herbert screw and non-vascularized bone graft failed. There is no evidence of radiocarpal arthritis. Which of the following is the most appropriate surgical treatment to maximize the chance of union?

Explanation

For scaphoid nonunions with AVN of the proximal pole, especially those that have failed prior surgery and possess a very small proximal fragment, a free vascularized bone graft from the medial femoral condyle (MFC) is the gold standard. The MFC graft provides robust, highly vascularized structural bone and has demonstrated higher union rates in this specific, difficult clinical scenario compared to pedicled distal radius grafts like the 1,2 ICSRA.

Question 2

A 24-year-old motorcyclist sustains a severe closed traction injury to his right brachial plexus. Examination reveals a flail, insensate right upper extremity and a right-sided ptosis and miosis. An MRI of the cervical spine is performed. Which of the following MRI findings is most consistent with the clinical examination and indicates an irreparable lesion at the root level?

Explanation

The patient has a pan-brachial plexus injury with a Horner syndrome (ptosis, miosis, anhidrosis), indicating involvement of the T1 sympathetic fibers. This suggests a pre-ganglionic root avulsion. The hallmark MRI finding of a pre-ganglionic nerve root avulsion is a traumatic pseudomeningocele, which represents a dural tear with cerebrospinal fluid leakage into the extra-spinal soft tissues. Pre-ganglionic lesions are not amenable to direct nerve repair or grafting and require nerve transfers.

Question 3

In a two-stage flexor tendon reconstruction utilizing a silicone tendon implant (Hunter rod) for a chronic Zone 2 flexor digitorum profundus (FDP) laceration, what is the primary biological objective of the first stage of the procedure?

Explanation

The primary purpose of the first stage of a two-stage flexor tendon reconstruction is the placement of a silicone spacer (Hunter rod) to induce the formation of a biological, highly vascularized pseudosheath. This pseudosheath provides a smooth, low-friction gliding surface and a rich vascular supply for the autologous tendon graft that will be inserted during the second stage (typically 3-4 months later).

Question 4

A 50-year-old patient presents with right-sided neck pain radiating down the arm, weakness in elbow extension and wrist flexion, and a diminished triceps reflex. Sensation is decreased over the palmar aspect of the middle finger. MRI demonstrates a paracentral disc herniation at the C6-C7 level. Which spinal nerve root is compressed, and where does it normally exit?

Explanation

The clinical presentation (weak triceps, weak wrist flexion, decreased middle finger sensation, diminished triceps reflex) is classic for a C7 radiculopathy. In the cervical spine, there are 8 cervical nerve roots but only 7 cervical vertebrae. Roots C1-C7 exit above their corresponding numbered pedicles. Therefore, the C7 nerve root exits through the C6-C7 neural foramen, which is located above the C7 pedicle.

Question 5

During autologous nerve grafting for a 4 cm post-traumatic peripheral nerve gap, what is the primary cellular/structural contribution of the interposed donor nerve graft?

Explanation

In an autologous nerve graft, the axons within the donor graft undergo Wallerian degeneration. However, the graft's basal lamina (endoneurial tubes) and viable Schwann cells remain intact. The Schwann cells multiply, clear debris, and form bands of Büngner, which produce neurotrophic factors. This provides both the biological environment and the physical pathways to guide the regenerating axons from the host's proximal stump into the distal stump.

Question 6

An avid cyclist presents with a 3-month history of right hand weakness. Examination reveals marked atrophy of the dorsal interossei and a positive Froment sign. Sensation is completely intact over the volar and dorsal aspects of the small finger and the ulnar half of the ring finger. Hypothenar muscle bulk is normal. Where is the most likely site of ulnar nerve compression?

Explanation

The ulnar nerve bifurcates within Guyon's canal. Zone 1 is proximal to the bifurcation (contains both motor and sensory fibers). Zone 2 contains the deep motor branch only. Zone 3 contains the superficial sensory branch only. Sparing of sensation and hypothenar muscles (which are innervated proximally in the canal or just before the deep branch dives) but severe intrinsic weakness points precisely to a deep motor branch compression in Zone 2, commonly seen in cyclists (handlebar palsy).

Question 7

Which of the following physical examination findings is highly specific for distinguishing true neurogenic thoracic outlet syndrome (TOS) from a severe compressive ulnar neuropathy at the elbow (cubital tunnel syndrome)?

Explanation

True neurogenic thoracic outlet syndrome typically affects the lower trunk of the brachial plexus (C8-T1). Because T1 fibers contribute to the median nerve to innervate the thenar intrinsics, severe lower trunk TOS presents with atrophy of both the hypothenar muscles AND the thenar muscles (specifically the APB), creating the classic 'Gilliatt-Sumner hand'. Cubital tunnel syndrome only affects ulnar-innervated intrinsic muscles, sparing the median-innervated APB.

Question 8

A 35-year-old carpenter sustains a saw injury resulting in a 3.5 cm defect in the proper digital nerve of the index finger in Zone 2. Which of the following reconstructive options represents the gold standard with the most predictable sensory recovery for this specific defect?

Explanation

For digital nerve gaps greater than 2.5 to 3.0 cm, autologous nerve grafting remains the gold standard. While nerve conduits and decellularized allografts are often used for smaller gaps (<1.5 to 2.0 cm) to avoid donor site morbidity, their clinical outcomes drop significantly for defects larger than 3 cm. An autograft (such as the medial antebrachial cutaneous or sural nerve) provides the necessary endoneurial architecture and viable Schwann cells to support regeneration across large gaps.

Question 9

A 42-year-old patient presents with sudden-onset bilateral and symmetric saddle anesthesia, early bowel and bladder incontinence, and impotence. Lower extremity examination reveals hyperreflexia at the knees but absent Achilles reflexes. Motor weakness is mild and symmetric. Where is the most likely neuroanatomic location of the primary lesion?

Explanation

The presentation of sudden-onset, symmetric saddle anesthesia, prominent and early bowel/bladder/sexual dysfunction, and a mixture of Upper Motor Neuron (hyperreflexive knee jerks) and Lower Motor Neuron (absent ankle jerks) signs is characteristic of Conus Medullaris syndrome. In contrast, Cauda Equina syndrome typically presents with asymmetric radicular pain, progressive asymmetric weakness, pure LMN signs (hyporeflexia), and late-onset sphincter dysfunction.

Question 10

In the predictable progression of Scapholunate Advanced Collapse (SLAC) wrist arthritis, which specific radiocarpal or midcarpal articulation is characteristically spared, allowing for surgical salvage via proximal row carpectomy (PRC) in earlier stages?

Explanation

SLAC wrist arthritis follows a very predictable sequence: Stage I involves the radial styloid and distal scaphoid; Stage II involves the entire radioscaphoid articulation; Stage III involves the capitolunate joint. The radiolunate joint is universally spared because the lunate maintains a congruous, spherical articulation with the lunate fossa of the radius, lacking abnormal shear forces. This sparing allows for a proximal row carpectomy (which creates a new articulation between the capitate and the lunate fossa) provided the capitate head is not severely arthritic.

Question 11

When harvesting an autologous corticocancellous bone graft from the anterior iliac crest for the treatment of a structural atrophic nonunion, what is the primary biological property provided by the cancellous portion of the graft?

Explanation

A corticocancellous bone graft provides multiple properties. The cortical portion primarily provides structural mechanical support and acts as an osteoconductive scaffold. The cancellous portion is rich in mesenchymal stem cells, osteoprogenitor cells, and osteoinductive proteins (like BMPs). Therefore, the cancellous bone primarily provides osteogenesis (living cells that form bone) and osteoinduction (factors that induce host cells to form bone).

Question 12

A patient is diagnosed with a peripheral, foveal avulsion of the Triangular Fibrocartilage Complex (TFCC), classified as a Palmer 1B lesion. To restore stability to the distal radioulnar joint (DRUJ), which specific anatomical structures within the TFCC must be anatomically repaired to the fovea?

Explanation

The primary stabilizers of the Distal Radioulnar Joint (DRUJ) are the dorsal and volar radioulnar ligaments. The deep fibers of these ligaments converge and attach to the fovea at the base of the ulnar styloid. An anatomic repair of a Palmer 1B foveal avulsion must reattach these deep fibers to the fovea to appropriately restore DRUJ mechanics and stability.

Question 13

During a right-sided anterior cervical discectomy and fusion (ACDF) at C6-C7, the patient develops a unilateral vocal cord paralysis. The vulnerability of the right recurrent laryngeal nerve during this approach is anatomically explained by its course looping under which of the following structures?

Explanation

The recurrent laryngeal nerves (RLN) have asymmetric courses. The left RLN loops under the aortic arch and ascends predictably in the tracheoesophageal groove, making it relatively safe during left-sided approaches. The right RLN loops under the right subclavian artery and has a much more variable, oblique course as it ascends toward the larynx, increasing its risk of iatrogenic injury during lower right-sided cervical spine approaches.

Question 14

In the classic Oberlin transfer used to restore elbow flexion following an upper trunk (C5-C6) brachial plexus avulsion injury, which specific nerve fascicles are transferred to the motor branch of the biceps?

Explanation

The classic Oberlin transfer is a nerve transfer used for C5-C6 root avulsions to restore elbow flexion. It involves transferring expendable motor fascicles from the intact ulnar nerve (specifically those innervating the flexor carpi ulnaris) directly to the motor branch of the musculocutaneous nerve that innervates the biceps. A double nerve transfer (Somsak) also includes transferring median nerve fascicles (FCR/FDS) to the brachialis branch.

Question 15

The off-label use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in Anterior Cervical Discectomy and Fusion (ACDF) procedures has been strongly associated with which of the following serious postoperative complications?

Explanation

The use of rhBMP-2 (Infuse) in the anterior cervical spine is controversial and officially off-label due to a high risk of profound inflammatory responses. This inflammation causes severe prevertebral soft tissue swelling, which can result in life-threatening airway compromise, severe dysphagia, and the need for prolonged intubation or re-intubation.

Question 16

The tenuous blood supply to the proximal pole of the scaphoid is a primary factor in its high rate of nonunion following fracture. The predominant blood supply to the scaphoid enters at which anatomical location?

Explanation

The primary blood supply to the scaphoid (accounting for 70-80% of its vascularity) enters via the dorsal ridge, which is located on the dorsal aspect of the scaphoid waist. These vessels originate from the dorsal carpal branch of the radial artery and flow in a retrograde direction to supply the proximal pole. Because of this retrograde flow, fractures at the scaphoid waist or proximal pole disrupt the blood supply to the proximal fragment, leading to ischemia and nonunion.

Question 17

A patient presents with hand weakness and numbness in the ring and small fingers. The examiner is trying to differentiate between a C8 radiculopathy and a severe ulnar neuropathy at the elbow. Weakness in which of the following muscles firmly points to a C8 radiculopathy rather than an ulnar neuropathy?

Explanation

Both C8 radiculopathy and ulnar neuropathy can cause weakness in the intrinsic muscles of the hand and sensory changes in the ulnar digits. However, the flexor pollicis longus (FPL) is innervated by the anterior interosseous nerve (a branch of the median nerve), but its nerve fibers originate from the C8 spinal root. Weakness of the FPL (or Extensor Indicis Proprius via the radial nerve, also C8) in the presence of ulnar-sided hand symptoms strongly localizes the lesion to the C8 root rather than the peripheral ulnar nerve.

Question 18

In the Masquelet technique for reconstructing a 3 cm segmental bone defect of a metacarpal, a PMMA cement spacer is temporarily placed. During the second stage (typically 6-8 weeks later), a thick membrane surrounds the spacer. What is the primary biological characteristic of this induced membrane?

Explanation

The induced membrane technique (Masquelet) relies on the foreign body reaction to the PMMA cement spacer. This reaction forms a highly vascularized, pseudosynovial membrane. Biologically, this membrane secretes high levels of crucial growth factors, including Vascular Endothelial Growth Factor (VEGF), Transforming Growth Factor-beta 1 (TGF-β1), and Bone Morphogenetic Protein-2 (BMP-2), which provide a fertile, osteoinductive, and osteogenic environment for the subsequently placed cancellous bone graft.

Question 19

A 55-year-old male presents with severe, burning anterior thigh pain, weakness in right knee extension, and a diminished right patellar reflex. Sensation is decreased over the medial aspect of the lower leg. An MRI of the lumbar spine reveals an extraforaminal (far lateral) disc herniation at the L4-L5 level. Which nerve root is primarily compressed?

Explanation

In the lumbar spine, a classic paracentral disc herniation compresses the descending (traversing) nerve root (e.g., L4-L5 paracentral disc hits the L5 root). However, an extraforaminal or 'far lateral' disc herniation at L4-L5 compresses the exiting nerve root at that level, which is the L4 root. An L4 radiculopathy clinically presents with anterior thigh pain, quadriceps weakness (knee extension), and a diminished patellar reflex.

Question 20

A 60-year-old patient with severe, chronic carpal tunnel syndrome presents with profound atrophy of the thenar eminence and an inability to palmar abduct the thumb, though thumb interphalangeal joint flexion is strong. To restore thumb palmar abduction with a transfer that requires minimal motor re-education, which of the following is the most commonly indicated procedure?

Explanation

The Camitz transfer utilizes the palmaris longus tendon, lengthened with a strip of the palmar aponeurosis, and routes it to the abductor pollicis brevis (APB) insertion. It is highly favored in cases of severe chronic carpal tunnel syndrome because it specifically restores palmar abduction (essential for a wide grasp). Furthermore, because the palmaris longus is a wrist flexor, it acts synergistically with finger flexion, meaning the patient requires almost no postoperative motor re-education to use it effectively.

Question 21

A 55-year-old man presents with chronic wrist pain and stiffness. Radiographs demonstrate advanced joint space narrowing at the radioscaphoid and capitolunate articulations. The radiolunate joint space is completely preserved. He has failed conservative management. Which of the following surgical interventions is most appropriate?

Explanation

The clinical and radiographic presentation describes a Stage III Scapholunate Advanced Collapse (SLAC) wrist, characterized by radioscaphoid and capitolunate arthritis with a preserved radiolunate joint. Proximal row carpectomy is contraindicated because the capitate head is arthritic and would articulate poorly with the lunate fossa. Four-corner fusion (capitate, hamate, lunate, triquetrum) with scaphoid excision effectively treats the arthritic joints while preserving the healthy radiolunate joint, maintaining functional, albeit reduced, wrist motion.

Question 22

When performing an autogenous cable nerve graft to bridge a 4-cm defect in the median nerve, standard surgical technique involves reversing the orientation of the harvested nerve graft. What is the primary biological rationale for this step?

Explanation

Autogenous nerve grafts (such as the sural nerve) have multiple branching points. If the graft is placed in its original prograde orientation, regenerating axons from the proximal stump can track down these branches and escape into the surrounding soft tissue, leading to a loss of axons reaching the distal stump and potential neuroma formation. Reversing the graft ensures that any branches point proximally, preventing axonal escape and funneling all regenerating axons directly toward the distal nerve stump.

Question 23

A 48-year-old woman complains of severe neck pain radiating into her medial right forearm and hand. On physical examination, she demonstrates 3/5 strength in the flexor digitorum profundus of her right ring and small fingers, and 3/5 strength in finger abduction. She has diminished sensation over the ulnar border of her right hand and small finger. Her triceps strength and reflex are intact. Which cervical nerve root is most likely compressed?

Explanation

The patient is presenting with a classic C8 radiculopathy. The C8 nerve root supplies the extrinsic finger flexors (flexor digitorum profundus) and intrinsic hand muscles (interossei, lumbricals), and provides sensation to the ulnar border of the hand and the small finger. A T1 radiculopathy would also affect the intrinsic muscles but presents with sensory changes in the medial forearm rather than the hand, and is much less common. C7 radiculopathy primarily affects the triceps, wrist flexors, and finger extensors, with sensory changes in the middle finger.

Question 24

A 32-year-old snowboarder sustains a high-energy fall onto an outstretched hand and presents with a volar Barton's fracture of the distal radius. The carpus is subluxated volarly along with the marginal fracture fragment. Which of the following ligamentous structures remains attached to the volar marginal fragment and acts as the primary deforming force tethering the carpus to it?

Explanation

A volar Barton's fracture is a shear fracture of the volar margin of the distal radius. The volar radiocarpal ligaments (which include the radioscaphocapitate, long radiolunate, and short radiolunate ligaments) originate on the volar rim of the distal radius. When this rim fractures, these strong stout ligaments remain attached to the fragment, causing the carpus to follow the fragment volarly and proximally due to the pull of the extrinsic flexor tendons.

Question 25

A surgeon is considering the use of a synthetic bone graft substitute to fill a metaphyseal void following elevation of a depressed tibial plateau fracture. Which of the following best describes the properties of calcium phosphate cement compared to calcium sulfate?

Explanation

Calcium phosphate cements have high compressive strength (often exceeding that of cancellous bone) and are resorbed very slowly, sometimes remaining visible on radiographs for years. They set via an isothermal or mildly exothermic reaction (unlike PMMA which is highly exothermic). In contrast, calcium sulfate has lower compressive strength and resorbs very rapidly (typically within 4 to 8 weeks), which can occasionally result in sterile serous drainage. Neither material is osteoinductive or osteogenic; both are strictly osteoconductive.

Question 26

A 28-year-old manual laborer is diagnosed with Stage IIIA Kienbock's disease. Radiographs show lunate sclerosis and fragmentation with lunate collapse, but no fixed scaphoid rotation or carpal collapse. His ulnar variance is minus 3 mm. Which of the following is the most appropriate surgical treatment?

Explanation

In Kienbock's disease (avascular necrosis of the lunate), Stage IIIA indicates lunate collapse but normal carpal alignment (no fixed scaphoid rotation or carpal height loss). In a patient with negative ulnar variance, joint leveling procedures such as a radial shortening osteotomy or ulnar lengthening are the gold standard. These procedures decompress the radiolunate joint, reducing forces across the lunate and frequently resulting in pain relief and prevention of further collapse. Salvage procedures (PRC or limited fusions) are reserved for later stages (IIIB or IV).

Question 27

A 45-year-old man presents with acute onset of low back pain radiating down his right leg following heavy lifting. MRI reveals a large paracentral disc herniation at the L4-L5 level on the right side. Which nerve root is most likely compressed, and what clinical finding is expected?

Explanation

In the lumbar spine, a typical paracentral disc herniation compresses the traversing nerve root, while a far lateral (foraminal/extraforaminal) disc herniation compresses the exiting nerve root. At the L4-L5 level, the exiting root is L4 and the traversing root is L5. Therefore, a paracentral disc herniation at L4-L5 affects the L5 nerve root. L5 radiculopathy is characterized by weakness in the extensor hallucis longus (great toe extension) and altered sensation over the dorsum of the foot, particularly the first dorsal web space.

Question 28

Recombinant human bone morphogenetic proteins (rhBMPs) are utilized in orthopedics to promote bone healing. At the cellular level, through which type of cell surface receptor do BMPs primarily initiate their intracellular signaling cascade?

Explanation

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-beta (TGF-beta) superfamily. They bind to specific type I and type II transmembrane receptors on the surface of mesenchymal stem cells. These receptors possess intrinsic serine/threonine kinase activity. Upon BMP binding, the type II receptor phosphorylates the type I receptor, which subsequently phosphorylates intracellular Smad proteins (Smad 1, 5, and 8), ultimately translocating to the nucleus to regulate transcription of osteogenic genes.

Question 29

A 25-year-old professional golfer complains of painful snapping on the ulnar side of his wrist during the downswing. Examination reveals subluxation of the extensor carpi ulnaris (ECU) tendon over the ulnar styloid during forearm supination, ulnar deviation, and wrist flexion. This pathology is primarily due to a tear or attenuation of which of the following structures?

Explanation

The extensor carpi ulnaris (ECU) tendon is stabilized in the sixth dorsal compartment by a distinct fascial structure known as the ECU subsheath. This subsheath firmly attaches the tendon to the ulnar groove. The extensor retinaculum lies superficial to the ECU subsheath but does not primarily prevent ECU subluxation. A tear of the ECU subsheath allows the tendon to snap out of its groove during forearm supination, wrist flexion, and ulnar deviation.

Question 30

A 60-year-old man undergoes a C4-C6 posterior laminectomy and instrumented fusion for cervical spondylotic myelopathy. On postoperative day 3, he suddenly develops profound unilateral weakness in shoulder abduction and elbow flexion, without a change in his leg strength or bowel/bladder function. What is the most widely accepted pathophysiologic mechanism for this complication?

Explanation

The patient is experiencing a C5 palsy, a well-known complication following cervical decompression surgery (particularly posterior laminectomy/laminoplasty). The C5 nerve root has a short, horizontal course. When the compressive pathology is removed posteriorly, the spinal cord shifts dorsally (posterior drift). This drift can place excessive traction (tethering) on the short C5 nerve root. It frequently presents in a delayed fashion (typically 2-5 days postoperatively) with deltoid and biceps weakness.

Question 31

When utilizing structural cortical allografts for reconstructive procedures, how does the biological incorporation process critically differ from that of cortical autografts?

Explanation

Cortical bone autografts incorporate through a process of creeping substitution (osteoclast-mediated cutting cones followed by osteoblast bone deposition) that gradually replaces the graft. In contrast, structural cortical allografts elicit an immune response and lack live cells, leading to delayed and limited host revascularization. Creeping substitution in massive structural allografts is often incomplete and typically limited to the superficial peripheral margins (outer 2-3 mm) and the junctional interfaces. The bulk of the allograft remains necrotic indefinitely, which predisposes it to late fracture.

Question 32

A 21-year-old man sustains a fracture through the proximal pole of the scaphoid. The vulnerability of this specific fracture to avascular necrosis and nonunion is primarily determined by the unique intraosseous retrograde blood supply of the scaphoid. The major blood supply to the scaphoid enters the bone predominantly at the dorsal ridge and is derived from a branch of which artery?

Explanation

The scaphoid has a tenuous retrograde blood supply. The major blood supply (accounting for 70-80% of the bone, including the entire proximal pole) enters via foramina along the dorsal ridge at the waist of the scaphoid. These vessels are branches of the dorsal carpal branch of the radial artery. Because the intraosseous blood flow is from distal to proximal, fractures at the waist or proximal pole disrupt the blood supply to the proximal fragment, leading to high rates of avascular necrosis and nonunion.

Question 33

A 16-year-old gymnast presents with progressive lower back pain and left leg pain. Imaging demonstrates a Grade II L5-S1 isthmic spondylolisthesis with bilateral pars interarticularis defects. If the patient has isolated left lower extremity radicular symptoms, which nerve root is most likely affected by the primary pathoanatomy of this condition?

Explanation

In isthmic spondylolisthesis at L5-S1, the defect is in the pars interarticularis of L5. The L5 nerve root exits the spinal canal through the L5-S1 neural foramen, passing directly inferior and anterior to the L5 pars. Hypertrophic fibrocartilaginous tissue (the 'Gill nodule') that forms at the site of the pars defect commonly compresses this exiting L5 nerve root in the foramen. This contrasts with degenerative spondylolisthesis (e.g., L4-L5), where central/lateral recess stenosis typically compresses the traversing root (L5).

Question 34

A 22-year-old rugby player presents 3 days after injuring his right ring finger when grabbing an opponent's jersey. He is unable to actively flex the distal interphalangeal (DIP) joint. Physical examination reveals tenderness in the palm, and radiographs are negative for a fracture. Based on the Leddy-Packer classification, what is the pathophysiology and recommended timing for surgical repair?

Explanation

The patient has a "Jersey finger" (flexor digitorum profundus avulsion). A Leddy-Packer Type I injury involves the tendon retracting all the way into the palm. Because it retracts this far, both the long and short vincula are completely torn, severing the tendon's blood supply. To prevent severe tendon necrosis and permanent contracture, Type I injuries must be surgically repaired early, ideally within 7 to 10 days. A Type II retracts to the PIP joint (held by intact long vinculum) and Type III involves a large bony fragment catching at the A4 pulley; both have preserved blood supply and can be repaired slightly later if necessary.

Question 35

When evaluating the regenerative properties of various bone grafting materials, the term 'osteoinduction' refers specifically to which of the following processes?

Explanation

Bone grafting relies on three primary mechanisms. Osteoconduction provides a passive structural scaffold for cell migration and new bone formation. Osteoinduction is the active chemical process by which growth factors (such as Bone Morphogenetic Proteins - BMPs) stimulate host primitive mesenchymal stem cells to recruit, proliferate, and differentiate into mature bone-forming osteoblasts. Osteogenesis refers to the direct provision of live, viable osteoblasts and osteoprogenitor cells transferred within the graft material itself (e.g., fresh autograft).

Question 36

A 35-year-old man sustained a mid-shaft humerus fracture resulting in a high radial nerve palsy that has shown no clinical or electromyographic signs of recovery at 12 months. In a standard set of tendon transfers (such as the Jones transfer) designed to restore hand and wrist function, which donor tendon is classically transferred to restore wrist extension?

Explanation

In a patient with a permanent high radial nerve palsy, tendon transfers are required to restore wrist extension, finger extension, and thumb extension. The classic transfer to restore wrist extension is the transfer of the Pronator Teres (PT) to the Extensor Carpi Radialis Brevis (ECRB). ECRB is chosen over ECRL to avoid radial deviation with extension. Finger extension is typically restored using either the FCU or FCR transferred to the Extensor Digitorum Communis (EDC). Thumb extension is restored by transferring the Palmaris Longus (PL) to the Extensor Pollicis Longus (EPL).

Question 37

A 42-year-old woman with a history of chronic low back pain presents to the emergency department with acute worsening of back pain, bilateral sciatica, and perineal numbness. Which of the following urologic findings is the earliest and most reliable indicator of cauda equina syndrome?

Explanation

Cauda equina syndrome involves compression of the lumbosacral nerve roots below the conus medullaris, affecting the parasympathetic supply to the bladder (S2-S4). This lower motor neuron injury leads to a loss of bladder sensation and a flaccid, areflexic detrusor muscle. The earliest and most reliable urologic sign is urinary retention. As the bladder fills without the ability to voluntarily void, it eventually leads to overflow incontinence. A post-void residual volume typically exceeds 100-200 mL.

Question 38

Cancellous bone autograft is considered the 'gold standard' for filling cavitary bone defects due to its rapid incorporation and optimal biological properties. Compared to cortical autograft, what is the primary histological mechanism that accounts for the faster revascularization and incorporation of cancellous bone graft?

Explanation

Cancellous autografts possess an open, porous trabecular architecture with large marrow spaces. This structure allows for rapid ingrowth of host capillaries (angiogenesis) directly into the graft. Once vascularized, host osteoblasts can immediately begin depositing new woven bone on the surfaces of the dead trabeculae (a process called appositional bone formation). In contrast, dense cortical autograft lacks these large open spaces and requires a much slower process of osteoclastic resorption (cutting cones) to create channels before osteoblasts can deposit new bone, making its incorporation significantly slower.

Question 39

A 65-year-old woman with neglected, severe carpal tunnel syndrome presents with profound thenar atrophy and complete inability to oppose her thumb. The surgeon plans a carpal tunnel release combined with a Bunnell (or Royle-Thompson) opponensplasty. Which of the following describes the most common tendon transfer and pulley utilized in this specific technique to restore true thumb opposition?

Explanation

True thumb opposition requires abduction, flexion, and pronation. To achieve the correct vector of pull (from the thumb metacarpal/proximal phalanx directed toward the pisiform), a pulley is necessary on the ulnar aspect of the wrist. The Bunnell or Royle-Thompson opponensplasty classically utilizes the flexor digitorum superficialis (FDS) of the ring finger. The tendon is passed around the distal flexor carpi ulnaris (FCU) tendon and pisiform (which act as a pulley) to direct the line of pull correctly. The Camitz transfer (PL to APB) provides excellent abduction but lacks the ulnar vector required for true opposition.

Question 40

An 8-month-old infant presents with an unresolved Erb-Duchenne palsy (C5-C6 injury) following a difficult vertex delivery with shoulder dystocia. The affected arm rests in internal rotation and adduction at the shoulder, with the elbow extended and forearm pronated. The internal rotation contracture of the shoulder is primarily driven by the unopposed action of which of the following muscles?

Explanation

In Erb-Duchenne palsy, damage to the C5 and C6 nerve roots causes paralysis of the external rotators (infraspinatus and teres minor) and abductors (supraspinatus and deltoid) of the shoulder, as well as the elbow flexors (biceps, brachialis) and forearm supinators. The unparalyzed internal rotators—most notably the subscapularis and pectoralis major—overpower the weak external rotators, leading to a progressive internal rotation contracture of the shoulder. This positional deformity is classically referred to as the 'waiter's tip' posture.

Question 41

A 26-year-old male presents with a persistent scaphoid nonunion and avascular necrosis of the proximal pole, featuring a humpback deformity and a 6 mm bone defect. Which of the following graft options provides both the structural integrity to correct the deformity and the robust blood supply necessary for this specific scenario?

Explanation

The free vascularized medial femoral condyle (MFC) graft provides necessary structural support to correct large defects (>5 mm) and humpback deformities, along with a robust blood supply essential for healing AVN.

Question 42

To restore elbow flexion in a patient with a traumatic C5-C6 brachial plexus root avulsion, an Oberlin transfer is planned. Which of the following describes the classic donor and recipient nerves in this procedure?

Explanation

The classic Oberlin transfer utilizes a redundant fascicle from the ulnar nerve (usually the FCU motor fascicle) which is transferred directly to the biceps motor branch of the musculocutaneous nerve.

Question 43

During an Adams-Berger anatomic reconstruction of the distal radioulnar joint (DRUJ) for chronic instability, a tendon graft is utilized to recreate the palmar and dorsal radioulnar ligaments. Where are the graft ends passed through the radius?

Explanation

The Adams-Berger procedure reconstructs the radioulnar ligaments using a graft passed through an isometric tunnel in the ulnar fovea and secured through tunnels at the dorsal and volar margins of the sigmoid notch.

Question 44

Following peripheral nerve injury and subsequent grafting, what is the primary role of Schwann cells during the process of Wallerian degeneration?

Explanation

During Wallerian degeneration, Schwann cells proliferate, assist in clearing myelin debris, and form longitudinal columns (Bands of Bungner) that guide regenerating axonal sprouts across the graft.

Question 45

A 45-year-old female presents with acute onset of severe unilateral shoulder pain, which subsides after one week, leaving profound weakness in shoulder abduction and external rotation. MRI of the cervical spine is unremarkable. EMG shows active denervation in the supraspinatus and infraspinatus. What is the most likely diagnosis?

Explanation

Acute, severe neuropathic shoulder pain followed by patchy weakness (often involving the suprascapular or axillary nerves) is the classic presentation of Parsonage-Turner syndrome (idiopathic brachial neuritis).

Question 46

In the standard flexor carpi radialis (FCR) tendon transfer utilized for a high radial nerve palsy, which muscle is typically transferred to the extensor pollicis longus (EPL) to restore thumb extension?

Explanation

In the classic FCR tendon transfer for radial nerve palsy, the pronator teres is transferred to the ECRB, the FCR is transferred to the EDC, and the palmaris longus is transferred to the EPL.

Question 47

Demineralized bone matrix (DBM) is widely used in hand and upper extremity osseous reconstruction. Which of the following best describes the biologic properties of DBM?

Explanation

DBM lacks viable cells, so it is not osteogenic. However, it contains bone morphogenetic proteins (BMPs) providing osteoinductive properties, and its collagenous matrix provides an osteoconductive scaffold.

Question 48

A 42-year-old carpenter presents with cold intolerance and a pulsatile mass in the hypothenar eminence of his dominant hand. Angiography reveals occlusion and aneurysmal dilation of the superficial palmar branch of the ulnar artery. Which bony structure contributes to the pathomechanics of this specific condition?

Explanation

Hypothenar hammer syndrome involves thrombosis or aneurysm of the superficial palmar branch of the ulnar artery as it is repetitively crushed against the hook of the hamate during manual labor.

Question 49

In a patient presenting with a complete flail upper extremity after a motorcycle accident, which of the following electrodiagnostic findings most specifically indicates a pre-ganglionic (avulsion) brachial plexus injury rather than a post-ganglionic lesion?

Explanation

In a pre-ganglionic root avulsion, the dorsal root ganglion remains intact and connected to the peripheral nerve. Therefore, SNAPs remain preserved despite central disconnection and clinical anesthesia.

Question 50

In Scapholunate Advanced Collapse (SLAC) of the wrist, progressive degenerative changes predictably involve specific articular surfaces while sparing others. Which radiocarpal articulation is classically spared from degenerative arthritis in the SLAC wrist?

Explanation

The radiolunate joint is typically spared in SLAC wrists because the lunate's concentric articulation with the spherical lunate fossa of the radius maintains normal congruent mechanics despite surrounding instability.

Question 51

The sural nerve is the most common autograft utilized for bridging peripheral nerve defects. Following harvesting of the sural nerve from the posterior calf, in which specific area will the patient predictably experience a permanent sensory deficit?

Explanation

The sural nerve provides sensory innervation to the lateral aspect of the foot and the distal posterolateral lower leg, making these areas predictably insensate after graft harvest.

Question 52

A patient presents with an inability to form an "OK" sign with their thumb and index finger but maintains normal sensation throughout the hand. Which of the following muscles is typically spared in a complete, isolated anterior interosseous nerve (AIN) palsy?

Explanation

The AIN innervates the FPL, the FDP to the index and middle fingers, and the pronator quadratus. The flexor carpi radialis (FCR) is innervated by the main branch of the median nerve proximal to the AIN origin.

Question 53

A patient with a chronic lower brachial plexus injury (C8-T1) exhibits a severe claw hand deformity. A modified Stiles-Bunnell tendon transfer is planned to restore intrinsic function. Which of the following muscles is utilized as the donor in this procedure?

Explanation

The Stiles-Bunnell procedure utilizes a Flexor Digitorum Superficialis (FDS) tendon split into multiple slips and transferred to the lateral bands to correct clawing in intrinsic-minus hands.

Question 54

In a Bennett fracture-dislocation of the thumb, the metacarpal shaft is displaced by the deforming forces of specific muscles. Which muscle is primarily responsible for the dorsal, proximal, and radial displacement of the first metacarpal shaft?

Explanation

The APL inserts on the base of the first metacarpal and exerts a strong proximal and radial pull on the shaft fragment, resulting in the classic displacement seen in a Bennett fracture.

Question 55

Vascularized nerve grafts (e.g., vascularized ulnar nerve graft) are considered theoretically superior to standard non-vascularized nerve autografts in which of the following specific clinical scenarios?

Explanation

Vascularized nerve grafts maintain their own blood supply and do not rely on creeping angiogenesis from the surrounding bed, making them ideal for large gaps in poorly vascularized, scarred, or irradiated tissues.

Question 56

Biomechanical studies evaluating flexor tendon repairs in Zone 2 demonstrate that the initial tensile strength of the repair before biologic healing occurs is most directly proportional to which of the following factors?

Explanation

The initial tensile strength of a flexor tendon repair is directly proportional to the number of core suture strands crossing the repair site and the thickness (caliber) of the suture material utilized.

Question 57

A 25-year-old male presents with a scaphoid nonunion demonstrating a humpback deformity and avascular necrosis of the proximal pole on MRI. The proximal fragment measures 6 mm. Which of the following is the most appropriate vascularized bone graft to restore scaphoid geometry and maximize the likelihood of union?

Explanation

A free medial femoral condyle vascularized bone graft provides structural corticocancellous bone capable of correcting a humpback deformity while revascularizing the proximal pole. Pedicled distal radius grafts like the 1,2 ICSRA are often too thin to correct significant humpback deformities and have higher failure rates in advanced AVN.

Question 58

A 22-year-old motorcyclist sustains a traumatic brachial plexus injury. Clinical examination shows complete paralysis of the C5 and C6 myotomes. Sensory examination reveals anesthesia in the C5 and C6 dermatomes, yet Sensory Nerve Action Potentials (SNAPs) for the median and radial nerves are preserved. What is the anatomical location of this nerve injury?

Explanation

The presence of preserved SNAPs in an anesthetic dermatome is the hallmark of a preganglionic root avulsion. The dorsal root ganglion remains intact and connected to the peripheral nerve, maintaining the distal axon's viability despite central disconnection.

Question 59

A 45-year-old manual laborer presents with Stage III Scapholunate Advanced Collapse (SLAC). Radiographs reveal advanced arthritis at the radioscaphoid and capitolunate joints, with sparing of the radiolunate joint. What is the most appropriate definitive surgical management?

Explanation

Stage III SLAC wrist involves the capitolunate joint, which makes proximal row carpectomy (PRC) contraindicated because the capitate will articulate directly with the lunate fossa. Scaphoid excision with four-corner fusion relies on the preserved radiolunate joint.

Question 60

During surgical exploration of a complete median nerve transection in the mid-forearm, a nerve defect of 3.5 cm is measured after debridement of non-viable tissue. The injury is 4 weeks old. What is the gold standard reconstruction for this defect?

Explanation

For critical mixed or motor nerve defects greater than 2.5 to 3 cm, autologous nerve grafting (e.g., sural nerve) remains the gold standard. Synthetic conduits and allografts have higher failure rates for defects larger than 3 cm or in major motor/mixed nerves.

Question 61

A 19-year-old rugby player sustains a closed jersey finger injury of the ring finger. Radiographs show no fracture, and the flexor digitorum profundus (FDP) tendon is palpable in the palm. To prevent irreversible contracture and tendon necrosis due to disrupted vincular blood supply, definitive repair should ideally be performed within what timeframe?

Explanation

A Type I FDP avulsion retracts into the palm, rupturing both the short and long vincula and severely compromising the tendon's blood supply. Repair should be performed within 7 to 10 days to prevent tendon necrosis and irreversible contracture.

Question 62

A patient with an isolated, irreparable high radial nerve palsy requires tendon transfers to restore wrist extension, finger extension, and thumb extension. Which of the following is the most standard and reliable donor muscle to restore wrist extension?

Explanation

The pronator teres (PT) is the most reliable and universally used donor muscle for transfer to the extensor carpi radialis brevis (ECRB) to restore wrist extension in radial nerve palsy. It has excellent excursion and synergistic function.

Question 63

A patient is undergoing an Oberlin transfer for a C5-C6 brachial plexus root avulsion to restore elbow flexion. Which specific donor nerve fascicle is most commonly transferred to the motor branch of the biceps?

Explanation

The classic Oberlin transfer utilizes an expendable motor fascicle from the ulnar nerve (typically the one innervating the flexor carpi ulnaris) transferred to the motor branch of the biceps to restore elbow flexion in upper trunk injuries.

Question 64

A 35-year-old patient presents with severe Stage IIIA Kienböck's disease. Radiographs reveal lunate sclerosis and fragmentation but no fixed carpal collapse, accompanied by an ulnar negative variance of 3 mm. Which of the following is the most appropriate joint-leveling procedure?

Explanation

In early advanced Kienböck's disease (Stage IIIA) with ulnar negative variance, a radial shortening osteotomy is the preferred joint-leveling procedure to decompress the lunate and halt disease progression.

Question 65

During exploration of a brachial plexus injury 5 months post-trauma, a neuroma-in-continuity is identified at the upper trunk. Intraoperative nerve stimulation across the neuroma yields a reproducible nerve action potential (NAP). What is the most appropriate next step in management?

Explanation

A positive nerve action potential (NAP) across a neuroma-in-continuity indicates that functionally significant axonal regeneration is occurring. The correct management is careful neurolysis, leaving the nerve intact to allow continued recovery.

Question 66

In arthroscopic repair of a peripheral triangular fibrocartilage complex (TFCC) tear, which of the following neurological structures is at highest risk of injury when establishing the 6U portal?

Explanation

The dorsal sensory branch of the ulnar nerve (DSBUN) courses directly over the ulnar aspect of the wrist. It is highly susceptible to injury during the establishment of the 6U portal or during inside-out TFCC repairs.

Question 67

A patient develops a Scaphoid Nonunion Advanced Collapse (SNAC) wrist following an untreated scaphoid fracture. What is the typical sequential progression of degenerative arthritis in a SNAC wrist?

Explanation

SNAC wrist arthritis reliably progresses in a specific sequence: beginning at the radial styloid-scaphoid articulation (Stage I), advancing to the scaphocapitate joint (Stage II), and finally involving the capitolunate joint (Stage III). The radiolunate joint is typically spared.

Question 68

A 40-year-old male sustains a laceration over the proximal phalanx (Zone II), severing both the FDS and FDP tendons. The surgeon attempts a primary repair but inadvertently sutures the lumbrical muscle too tightly during closure. What clinical phenomenon is the patient most likely to exhibit postoperatively?

Explanation

Suturing the lumbrical too tightly or allowing the FDP to retract proximal to the lumbrical origin creates a 'lumbrical plus' finger. Attempted active flexion of the FDP paradoxically increases tension on the lumbrical, leading to active extension of the PIP and DIP joints.

Question 69

A 28-year-old male sustains a severe traction injury to his right upper extremity. Clinical examination reveals complete flaccidity of the arm, absent sensation, ptosis, miosis, and anhidrosis on the right side of his face. This specific facial triad implies poor prognosis for spontaneous nerve recovery because it indicates injury to which structure?

Explanation

The presence of Horner syndrome (ptosis, miosis, anhidrosis) indicates a preganglionic avulsion of the T1 nerve root. This interrupts the sympathetic chain connection to the stellate ganglion, confirming an irreparable preganglionic lesion.

Question 70

In the context of scapholunate dissociation, a patient is planned for a capsulodesis and ligamentous reconstruction. Which distinct region of the scapholunate interosseous ligament is thickest, strongest, and most critical to reconstruct to restore normal carpal kinematics?

Explanation

The dorsal region of the scapholunate interosseous ligament is the thickest and mechanically most important stabilizer of the scapholunate joint. Reconstruction efforts primarily focus on restoring this dorsal continuity.

Question 71

A 65-year-old woman presents 8 weeks after open reduction and internal fixation of a distal radius fracture with a volar locking plate. She suddenly lost the ability to actively extend her thumb interphalangeal joint. Radiographs show prominent screws penetrating the dorsal cortex. What is the most reliable surgical treatment for this complication?

Explanation

Prominent dorsal screws from volar plating commonly cause attritional rupture of the Extensor Pollicis Longus (EPL) tendon. Primary repair is usually impossible due to retracted, frayed tendon ends; therefore, an EIP to EPL transfer is the gold standard treatment.

Question 72

A surgeon is harvesting an autologous sural nerve graft for a brachial plexus reconstruction. To predictably locate the sural nerve with minimal dissection, the initial incision should be placed precisely in which anatomical location?

Explanation

The sural nerve is most reliably found running immediately posterior to the lateral malleolus in close association with the small saphenous vein. This is the standard distal landmark for its harvest.

Question 73

A 24-year-old male presents with profound median nerve palsy. To restore thumb opposition, a Burkhalter transfer is planned utilizing the Extensor Indicis Proprius (EIP). To optimize the vector for thumb pronation and palmar abduction, the transferred EIP tendon should be routed around which anatomical structure to act as a pulley?

Explanation

In an EIP to APB transfer (Burkhalter), routing the tendon around the ulnar border of the palmar aponeurosis (or sometimes the FCU depending on specific modifications, but classically the ulnar border of the palmar fascia) directs the vector of pull from the pisiform area. This optimally restores true thumb opposition.

Question 74

A patient with a chronic, isolated, traumatic avulsion of the axillary nerve with complete deltoid atrophy is scheduled for a nerve transfer 5 months post-injury. Which of the following is the most highly successful donor nerve for restoring deltoid function in this setting?

Explanation

The Somsak procedure (or its variations) utilizes a motor branch of the radial nerve to the long or medial head of the triceps transferred directly to the anterior division of the axillary nerve. It is highly successful for isolated axillary nerve injuries due to synergistic action and proximity.

Question 75

A 30-year-old carpenter suffers a deep laceration at the level of the proximal interphalangeal (PIP) joint, transecting the central slip of the extensor tendon. If left untreated, the lateral bands will eventually subluxate. In relation to the axis of rotation of the PIP joint, in which direction do the lateral bands migrate to produce the classic resulting deformity?

Explanation

Untreated central slip ruptures lead to a Boutonniere deformity. The lateral bands migrate volar to the axis of rotation of the PIP joint, converting their extensor force into a flexor force at the PIP, while continuing to extend the DIP joint.

Question 76

A 35-year-old male sustains a severe traction injury to his right upper extremity. Clinical examination reveals flaccid paralysis of the entire right arm with anesthesia from the shoulder to the hand. Electromyography (EMG) shows denervation of the cervical paraspinal muscles. Sensory nerve action potentials (SNAPs) are tested for the right upper extremity. Which of the following SNAP findings is most consistent with this patient's injury level and prognosis?

Explanation

Normal SNAPs in an anesthetic limb indicate a preganglionic injury (root avulsion). The sensory dorsal root ganglion remains intact and connected to the peripheral nerve, while the central connection to the spinal cord is severed.

Question 77

In the treatment of severe scaphoid nonunions with avascular necrosis of the proximal pole, a free vascularized bone graft from the medial femoral condyle (MFC) is frequently utilized. Which of the following vessels provides the primary arterial supply to the standard MFC vascularized bone graft?

Explanation

The descending genicular artery, along with its articular and saphenous branches, is the primary vascular supply to the medial femoral condyle corticocancellous bone graft.

Question 78

A 28-year-old carpenter presents with a 5 cm gap in the median nerve at the mid-forearm following a circular saw injury 3 months ago. Which of the following grafting techniques provides the highest likelihood of successful motor and sensory recovery?

Explanation

For critical nerve gaps greater than 3 cm, autograft (such as the reversed sural nerve) remains the gold standard. Conduits and acellular allografts have unacceptably high failure rates in gaps exceeding 3 cm.

Question 79

A 45-year-old manual laborer presents with chronic wrist pain. Radiographs reveal advanced scapholunate advanced collapse (SLAC) with arthritic changes involving the radioscaphoid joint and the proximal capitate. The radiolunate joint is entirely spared. Which of the following surgical interventions is most appropriate?

Explanation

This patient has SLAC Stage III wrist arthritis (capitolunate involvement). Proximal row carpectomy is contraindicated when the capitate head is arthritic; therefore, scaphoid excision with a four-corner fusion is the treatment of choice.

Question 80

A 22-year-old male presents with a complete C5-C6 root avulsion following a motorcycle accident. An Oberlin transfer is planned to restore elbow flexion. Which of the following describes the correct neurological transfer performed in this procedure?

Explanation

The classic Oberlin transfer involves taking an expendable motor fascicle from the ulnar nerve (usually supplying the FCU) and coapting it directly to the biceps motor branch of the musculocutaneous nerve to restore elbow flexion.

Question 81

Six months after a Zone II flexor tendon repair of the middle finger, a patient complains that the affected digit paradoxically extends at the proximal interphalangeal (PIP) joint when attempting to make a tight fist. What is the most likely etiology of this phenomenon?

Explanation

This describes 'lumbrical plus' syndrome, caused by a ruptured or overly long FDP tendon. When the patient attempts to flex, the retracted FDP pulls on the intact lumbrical origin, causing paradoxical PIP extension.

Question 82

A 40-year-old female with long-standing rheumatoid arthritis is suddenly unable to flex the interphalangeal joint of her right thumb. Examination reveals a loss of active thumb IP flexion but an intact tenodesis effect when the wrist is passively extended. What is the most likely cause of this deficit?

Explanation

Loss of active thumb IP flexion with an intact tenodesis effect implies that the FPL tendon is intact, pointing to a neurological cause such as Anterior Interosseous Nerve (AIN) syndrome. A ruptured FPL (Mannerfelt lesion) would have an absent tenodesis effect.

Question 83

A 25-year-old pitcher experiences sudden, severe right shoulder pain, followed two weeks later by profound weakness in external rotation and elevation. EMG demonstrates denervation isolated to the supraspinatus and infraspinatus. There is no history of trauma. What is the most likely diagnosis?

Explanation

Parsonage-Turner syndrome (idiopathic brachial neuritis) typically presents with acute, severe shoulder girdle pain followed by patchy weakness and amyotrophy, most commonly affecting the upper trunk distributions like the suprascapular nerve.

Question 84

During the incorporation of a free vascularized fibular graft used for a 10 cm radial defect, how does the biological healing process distinctly differ from that of a massive non-vascularized cortical bone autograft?

Explanation

Vascularized bone grafts maintain their intrinsic blood supply, avoiding the necrosis and creeping substitution seen in non-vascularized cortical grafts. They heal to the host bone via primary (callus-forming) bone union at the docking sites.

Question 85

A 38-year-old cyclist complains of intrinsic hand weakness and numbness strictly affecting the volar aspect of his small finger and the ulnar half of his ring finger. Sensation on the dorsal ulnar aspect of the hand is completely normal. Where is the most likely site of neural compression?

Explanation

Normal dorsal ulnar sensation localizes the lesion distal to the takeoff of the dorsal ulnar cutaneous nerve (which branches proximal to the wrist). A lesion in Zone 1 of Guyon's canal affects both mixed motor and sensory branches to the volar fingers.

Question 86

A patient presents with a Boutonniere deformity 4 weeks after sustaining a closed crush injury to the PIP joint. Which of the following describes the underlying pathomechanics of this deformity?

Explanation

A Boutonniere deformity results from a disruption of the central slip of the extensor mechanism, allowing the lateral bands to subluxate volarly to the axis of PIP joint rotation, leading to PIP flexion and DIP extension.

Question 87

When performing a nerve repair, the surgeon decides to use a 4-strand core suture technique for a Zone II flexor tendon repair rather than a 2-strand repair. What is the primary biomechanical advantage of the 4-strand repair in this setting?

Explanation

A 4-strand (or greater) core suture significantly increases the tensile strength and gap resistance of a flexor tendon repair, safely permitting early active motion protocols which reduce adhesion formation.

Question 88

A patient with suspected Pronator Syndrome presents with volar forearm pain and paresthesias in the thumb, index, and middle fingers. Which of the following physical examination findings most reliably differentiates Pronator Syndrome from Carpal Tunnel Syndrome?

Explanation

The palmar cutaneous branch of the median nerve provides sensation to the thenar eminence and branches proximal to the carpal tunnel. Sensory loss here occurs in Pronator Syndrome but is spared in Carpal Tunnel Syndrome.

Question 89

A 45-year-old male with Kienbock's disease presents with chronic wrist pain. Imaging reveals lunate sclerosis, fragmentation, and carpal collapse, with a negative ulnar variance of 3 mm. Advanced degenerative changes are noted at the radioscaphoid joint. Which of the following is the most appropriate management?

Explanation

In Kienbock's disease with fixed carpal collapse and secondary arthritic changes (Lichtman Stage IV or advanced IIIB with arthritis), joint leveling procedures (radial shortening) are contraindicated. A salvage procedure like PRC or scaphoid excision/4-corner fusion is required.

Question 90

Wallerian degeneration begins shortly after a peripheral nerve is completely transected. Which of the following cellular events is most responsible for clearing myelin debris during the first two weeks to prepare the distal stump for regenerating axons?

Explanation

During Wallerian degeneration, both blood-borne macrophages and resident Schwann cells undergo phagocytosis to clear myelin and axonal debris distal to the injury, creating a permissive environment for nerve regeneration.

Question 91

A 19-year-old gymnast presents with chronic ulnar-sided wrist pain. MRI demonstrates a central, avascular tear of the triangular fibrocartilage complex (TFCC) with no evidence of distal radioulnar joint (DRUJ) instability. Ulnar variance is neutral. What is the preferred surgical treatment?

Explanation

Central TFCC tears occur in the avascular zone and lack healing potential. In a stable DRUJ with neutral ulnar variance, arthroscopic debridement is the preferred treatment. Peripheral tears are vascularized and amenable to repair.

Question 92

A 50-year-old rheumatoid patient cannot actively extend her small and ring fingers at the metacarpophalangeal (MCP) joints. She can actively maintain extension if the fingers are passively placed in that position. A drop-finger sign is present. What is the most likely diagnosis?

Explanation

The ability to actively maintain extension once passively placed is the hallmark of sagittal band rupture causing volar subluxation of the extensor tendons. In Vaughan-Jackson syndrome (tendon rupture), the patient cannot maintain extension.

Question 93

In brachial plexus reconstruction for a complete C5-C6 root avulsion, transferring the distal spinal accessory nerve to the suprascapular nerve is considered. Which of the following muscles must have confirmed, robust baseline function prior to sacrificing the distal spinal accessory nerve?

Explanation

The spinal accessory nerve innervates the trapezius. Before transferring it, the surgeon must verify that trapezius function is sufficient to prevent debilitating shoulder drop, though usually only the distal portion is transferred to spare upper trapezius fibers.

Question 94

A 32-year-old man presents with a high radial nerve palsy following a humeral shaft fracture. A tendon transfer is planned to restore thumb extension. Which of the following is the most commonly used donor tendon to restore function to the extensor pollicis longus (EPL)?

Explanation

To restore thumb extension in radial nerve palsy, the Palmaris Longus (PL) is most commonly transferred to the EPL. (Note: EIP to EPL is typically used for isolated EPL ruptures, such as post-distal radius fractures, but in high radial nerve palsy, EIP is also paralyzed).

Question 95

Which of the following intrinsic properties of a peripheral nerve graft determines the maximum length it can bridge without succumbing to central ischemic necrosis, barring the use of a vascularized nerve graft?

Explanation

The diameter of a non-vascularized nerve graft dictates its survival. Large diameter nerve grafts (like whole sciatic or median) undergo central ischemic necrosis because revascularization from the recipient bed cannot penetrate the core fast enough.

AAOS & ABOS Upper Extremity MCQs (Set 4): Shoulder, Elbow, Wrist, Hand & Nerve Review | 2025-2026 Boards

Orthopedic Surgery Board Review MCQs: Hand & Wrist, Spinal Nerve & Grafting Part 35

Key Takeaway

Orthopedic Surgery Board Review MCQs: Hand & Wrist, Spinal Nerve & Grafting Part 35

Chapter Index