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Hand And Wrist: And Emq Questio Review | Dr Hutaif Hand -...

Advanced Hand & Wrist Orthopedic MCQs: Scaphoid Nonunion & Carpal Collapse

26 Apr 2026 35 min read 129 Views
Illustration of explanation this patient - Dr. Mohammed Hutaif

Key Takeaway

This interactive board review contains 100 randomly selected orthopedic surgery questions with clinical images, immediate feedback, and detailed references.

Advanced Hand & Wrist Orthopedic MCQs: Scaphoid Nonunion & Carpal Collapse

Comprehensive 100-Question Exam


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Question 1

A 42-year-old construction worker with a 5-year history of a scaphoid waist nonunion presents with severe wrist pain. Radiographs demonstrate joint space narrowing at the radioscaphoid articulation, as well as degenerative changes at the capitolunate joint. The radiolunate joint is preserved. Which of the following is the most appropriate surgical treatment?





Explanation

The patient has Stage III SNAC (Scaphoid Nonunion Advanced Collapse), characterized by the addition of capitolunate arthritis to radioscaphoid arthritis. Proximal row carpectomy (PRC) relies on a preserved capitate head to articulate with the lunate fossa of the radius; therefore, capitolunate arthritis is a strict contraindication to PRC. Scaphoid excision and four-corner fusion is the treatment of choice for Stage III SNAC.

Question 2

A surgeon plans to perform a 1,2 intercompartmental supraretinacular artery (1,2 ICSRA) vascularized bone graft for a scaphoid proximal pole nonunion. The pedicle for this graft is derived from which of the following source vessels?





Explanation

The 1,2 ICSRA is a consistently present branch of the radial artery. It courses distally on the dorsal aspect of the distal radius between the first and second extensor compartments and is utilized for pedicled vascularized bone grafts to the scaphoid (Zaidemberg's graft).

Question 3

In the natural history of an untreated scaphoid waist fracture, the carpus typically collapses into a Dorsal Intercalated Segment Instability (DISI) pattern. What biomechanical consequence directly drives this specific deformity?





Explanation

In a scaphoid waist nonunion, the distal pole tends to flex (volar rotation) due to the pull of the STT joint capsule and FCR, creating a 'humpback' deformity. Because the proximal scaphoid pole remains attached to the lunate via the intact scapholunate interosseous ligament, the uncoupled lunate extends under the normal physiologic influence of the triquetrum, leading to a DISI deformity.

Question 4

Which of the following best describes the dominant arterial supply to the proximal pole of the scaphoid?





Explanation

The primary blood supply to the scaphoid is retrograde. The dorsal carpal branch of the radial artery provides 70-80% of the blood supply, entering through the dorsal ridge and supplying the proximal pole and waist in a retrograde fashion. This poor vascularity puts the proximal pole at high risk for avascular necrosis following fracture.

Question 5

A 28-year-old male presents with a chronic proximal pole scaphoid nonunion and avascular necrosis (AVN). A free vascularized medial femoral condyle (MFC) bone graft is planned. Which vascular pedicle is primarily harvested to supply this graft?





Explanation

The free medial femoral condyle (MFC) vascularized bone graft is primarily supplied by the descending genicular artery (DGA), or alternatively the superomedial genicular artery if the DGA is insufficient. It provides excellent structural support and robust vascularity for challenging scaphoid nonunions complicated by AVN.

Question 6

When distinguishing between Scapholunate Advanced Collapse (SLAC) and Scaphoid Nonunion Advanced Collapse (SNAC), which of the following radiographic findings is uniquely characteristic of SNAC?





Explanation

Both SLAC and SNAC predictably spare the radiolunate joint (until end-stage pancarpal arthritis) and both feature progressive radioscaphoid and midcarpal arthritis. However, in SNAC, the scapholunate ligament remains intact, tethering the proximal scaphoid fragment to the lunate; thus, the scapholunate interval remains normal. In SLAC, this ligament is torn, causing a widened SL interval (Terry Thomas sign).

Question 7

A patient with a chronic scaphoid waist nonunion develops a significant humpback deformity but has no radiographic evidence of wrist osteoarthritis or proximal pole AVN. The surgeon plans to correct the deformity. Which approach and grafting technique is most appropriate to restore carpal kinematics?





Explanation

A humpback deformity in a scaphoid nonunion requires restoration of the volar scaphoid length to correct the intrascaphoid angle and secondary DISI deformity. A volar approach with a structural opening wedge bone graft (often harvested from the iliac crest) placed volarly corrects the deformity and restores normal carpal alignment.

Question 8

To accurately assess a scaphoid fracture for union or the degree of humpback deformity, computed tomography (CT) scans should be reformatted. What is the optimal plane of reconstruction to evaluate the true longitudinal axis of the scaphoid?





Explanation

The scaphoid lies at an oblique angle (approximately 45 degrees volar to the coronal plane and 45 degrees radial to the sagittal plane). To accurately evaluate the scaphoid morphology and trabecular bridging, CT imaging must be reformatted along its true longitudinal axis, which corresponds to a parasagittal plane approximately 45 degrees to the standard sagittal plane of the wrist.

Question 9

During a proximal row carpectomy (PRC) for Stage II SNAC wrist, the surgeon must be careful to preserve which of the following ligaments to prevent ulnar translation of the remaining carpus?





Explanation

During a PRC, the proximal carpal row (scaphoid, lunate, triquetrum) is excised, and the capitate articulates with the lunate fossa. The radioscaphocapitate (RSC) ligament acts as a primary volar sling and stabilizer; its preservation is critical to prevent ulnar translation of the carpus off the distal radius.

Question 10

Following scaphoid excision and four-corner arthrodesis for advanced SNAC wrist, the patient complains of persistent pain 9 months postoperatively. Radiographs indicate a pseudarthrosis. Which of the following articulations is the most common site for nonunion in a four-corner fusion?





Explanation

Nonunion is a well-recognized complication of four-corner arthrodesis (fusion of the lunate, capitate, hamate, and triquetrum). The capitolunate joint is the most common site of pseudarthrosis, likely due to its central location, high relative motion prior to fusion, and the significant shear forces transmitted across it during wrist loading.

Question 11

A 25-year-old male sustains a proximal pole scaphoid fracture. After 6 months of conservative management, he has an established nonunion. MRI with gadolinium demonstrates no enhancement of the proximal pole fragment. What is the most appropriate surgical intervention to optimize the chance of union?





Explanation

Lack of gadolinium enhancement on MRI indicates avascular necrosis (AVN) of the proximal pole. In a young patient without advanced arthrosis (SNAC), attempting joint preservation is paramount. A vascularized bone graft (pedicled from the radius or a free medial femoral condyle graft) provides the highest union rates for scaphoid nonunions complicated by severe ischemia or AVN.

Question 12

A 65-year-old low-demand patient with Stage III SNAC wrist presents with significant pain but wishes to avoid procedures that alter carpal mechanics or require prolonged immobilization. A total wrist denervation is planned. Which two nerves provide the most significant sensory contribution to the wrist joint and are primary targets for this procedure?





Explanation

Total or partial wrist denervation is a palliative procedure for chronic wrist pain. The anterior interosseous nerve (AIN) and the posterior interosseous nerve (PIN) carry the primary nociceptive sensory fibers from the deep wrist joint capsule. Resecting these terminal branches significantly reduces pain while preserving motor function and wrist motion.

Question 13

A 50-year-old heavy manual laborer with Stage IV SNAC wrist (pancarpal arthritis) opts for total wrist arthrodesis to maximize grip strength and eliminate pain. To optimize postoperative hand function, what is the ideal position for total wrist arthrodesis?





Explanation

Total wrist arthrodesis provides a stable, painless wrist for heavy laborers. The optimal position for functional grip strength and activities of daily living is 10 to 15 degrees of extension and 5 to 10 degrees of ulnar deviation. This positioning optimally tensions the finger flexors, maximizing mechanical advantage for grip.

Question 14

Scaphoid fractures in children are rare but can occasionally result in nonunion. Compared to adults, which anatomic location of the scaphoid is most frequently fractured and at highest risk for nonunion in the pediatric population?





Explanation

In the pediatric population, the ossification center of the scaphoid develops distally to proximally. Consequently, pediatric scaphoid fractures most commonly involve the distal pole, in contrast to adults where waist fractures heavily predominate. Nonunions, though rare, tend to occur at the distal pole in children.

Question 15

When evaluating a scaphoid nonunion with magnetic resonance imaging (MRI), which sequence and specific finding most reliably indicates the presence of avascular necrosis (AVN) in the proximal pole?





Explanation

While a low signal on T1 is a sign of ischemia or edema, it is not highly specific for true AVN, as bone marrow edema from the nonunion can produce similar findings. The most reliable MRI indicator of avascular necrosis is the lack of enhancement of the proximal pole on T1-weighted fat-suppressed images following the administration of intravenous gadolinium contrast.

Question 16

A 33-year-old athlete with a scaphoid waist nonunion demonstrates early degenerative changes strictly isolated to the articulation between the scaphoid and the radial styloid. There is no midcarpal arthritis. What is the most appropriate surgical management?





Explanation

The patient has Stage I SNAC, defined by arthritis isolated to the radioscaphoid joint (specifically the radial styloid). The standard of care for Stage I SNAC in an active patient is to attempt salvage of the scaphoid via nonunion takedown, bone grafting, and rigid fixation, coupled with a radial styloidectomy to excise the focal area of arthrosis and relieve impingement/pain.

Question 17

A 40-year-old female with no history of trauma presents with progressive radial-sided wrist pain. Imaging reveals sclerosis and fragmentation of the entire scaphoid with a normal scapholunate interval and no fracture line. This condition represents idiopathic avascular necrosis of the scaphoid. What is the eponym for this disease?





Explanation

Preiser's disease is the eponym for idiopathic avascular necrosis of the scaphoid. It occurs without a preceding fracture, differentiating it from traumatic scaphoid AVN. Kienböck's affects the lunate, Freiberg's affects the metatarsal head, Panner's affects the capitellum, and Köhler's affects the navicular bone in the foot.

Question 18

In the setting of an unstable scaphoid waist nonunion with secondary carpal collapse, lateral radiographs of the wrist are obtained. Which of the following angular measurements definitively confirms the presence of a Dorsal Intercalated Segment Instability (DISI) deformity?





Explanation

In a normal wrist, the scapholunate angle on a lateral radiograph is between 30 and 60 degrees. In a DISI deformity (which occurs in scaphoid nonunion due to uncoupling of the scaphoid and lunate), the lunate extends (dorsal tilt) while the distal scaphoid flexes. This divergence results in an abnormally increased scapholunate angle, typically greater than 60 degrees.

Question 19

When internally fixing a proximal pole scaphoid fracture or nonunion with a headless compression screw, what is the primary biomechanical advantage of utilizing a dorsal percutaneous or mini-open approach rather than a volar approach?





Explanation

The scaphoid is curved volarly. A volar approach often forces the screw to enter eccentrically (volarly and distally) to avoid the trapezium, leading to suboptimal peripheral placement. A dorsal approach allows the guidewire and screw to be placed directly down the longest mechanical, central axis of the scaphoid, providing superior biomechanical fixation, which is crucial for small proximal pole fragments.

Question 20

A surgeon performs a vascularized bone graft using a pedicle derived from the volar carpal artery to treat a scaphoid waist nonunion. Where is the osteocutaneous or bone flap typically harvested from when utilizing this specific vascular pedicle?





Explanation

The volar carpal artery vascularized bone graft (often referred to as the Kuhlmann graft) is harvested from the volar aspect of the distal radius. It is particularly useful for scaphoid waist nonunions requiring volar placement of the graft, such as when correcting a humpback deformity from a volar approach, providing both structural support and active blood supply.

Question 21

A 35-year-old male presents with wrist pain 8 years after a scaphoid fracture. Radiographs show radioscaphoid and capitolunate arthritis, but the radiolunate and lunotriquetral joints are spared. The diagnosis is SNAC Stage III. What is the most appropriate motion-preserving procedure?





Explanation

SNAC III involves radioscaphoid and capitolunate arthritis. Proximal row carpectomy is contraindicated due to capitolunate degeneration; therefore, scaphoid excision and four-corner fusion is the preferred motion-preserving treatment.

Question 22

A 24-year-old male has a proximal pole scaphoid nonunion with avascular necrosis and a collapsed humpback deformity. Previous 1,2 ICSRA bone grafting failed. What is the most appropriate surgical intervention to achieve union and restore scaphoid morphology?





Explanation

Free vascularized bone grafts, such as the medial femoral condyle (MFC) flap, are indicated for proximal pole nonunions with AVN and structural collapse, especially after failed pedicled grafting. The MFC provides robust structural support and reliable blood supply.

Question 23

In the progression of Scaphoid Nonunion Advanced Collapse (SNAC), which of the following joints is typically the last to be involved or remains definitively spared compared to SLAC arthritis?





Explanation

In both SLAC and SNAC wrists, the radiolunate joint is characteristically spared due to the congruent spherical articulation and absence of abnormal shear forces. Arthritis progresses through the radioscaphoid and midcarpal joints before ever affecting the radiolunate joint in end-stage disease.

Question 24

The major blood supply to the proximal pole of the scaphoid enters the bone at which anatomical location, making proximal pole fractures particularly susceptible to avascular necrosis?





Explanation

The scaphoid receives 70-80% of its vascularity from the dorsal carpal branch of the radial artery, which enters at the dorsal ridge and supplies the proximal pole in a retrograde fashion. This retrograde flow makes proximal fractures highly prone to ischemia.

Question 25

A 29-year-old athlete with a scaphoid waist nonunion has localized arthritis restricted to the radial styloid and the distal scaphoid. There is no humpback deformity. What is the most appropriate surgical management?





Explanation

This represents a SNAC Stage I wrist. The optimal treatment is a radial styloidectomy to address the localized arthritis combined with scaphoid ORIF and bone grafting to heal the nonunion.

Question 26

An untreated scaphoid waist fracture often leads to a humpback deformity. Which of the following best describes the resulting carpal malalignment?





Explanation

In a scaphoid waist nonunion, the distal scaphoid fragment tends to flex volarly along with the distal carpal row. The proximal fragment extends with the lunate, leading to a dorsal intercalated segment instability (DISI) pattern.

Question 27

Proximal row carpectomy (PRC) is being considered for a 45-year-old laborer with a collapsed carpus. Evaluation of which of the following articulations is most critical to determine if PRC is an appropriate option?





Explanation

During a PRC, the capitate articulates directly with the lunate fossa of the radius. Therefore, preservation of the capitolunate joint (specifically the proximal capitate articular surface) is critical for a successful outcome.

Question 28

When evaluating a scaphoid proximal pole nonunion, which imaging modality and specific finding is the most sensitive and specific for diagnosing avascular necrosis (AVN) prior to selecting a bone graft type?





Explanation

Gadolinium-enhanced MRI is the gold standard for assessing scaphoid vascularity. Absent or significantly decreased enhancement of the proximal pole indicates avascular necrosis, which typically necessitates a vascularized bone graft.

Question 29

The 1,2 intercompartmental supraretinacular artery (1,2 ICSRA) vascularized bone graft is commonly used for scaphoid nonunions. This artery courses between which two extensor compartments?





Explanation

The 1,2 ICSRA runs longitudinally along the distal radius between the first extensor compartment (APL, EPB) and the second extensor compartment (ECRL, ECRB). It is used as a pedicle for distal radius bone grafts to the scaphoid.

Question 30

A patient undergoes a scaphoid excision and four-corner fusion for SNAC Stage III. Which four carpal bones are fused in this procedure?





Explanation

A four-corner fusion involves the arthrodesis of the lunate, triquetrum, capitate, and hamate. The scaphoid is excised to eliminate the arthritic radioscaphoid articulation and correct the carpal mechanics.

Question 31

A volar approach is chosen for open reduction and internal fixation of a scaphoid waist fracture with a humpback deformity. Which interval is utilized to access the scaphoid?





Explanation

The standard volar (Russe) approach to the scaphoid utilizes the interval between the flexor carpi radialis (FCR) tendon and the radial artery. This approach is ideal for placing volar wedge grafts to correct humpback deformities.

Question 32

While both SLAC and SNAC wrists result in predictable patterns of carpal arthritis, what key pathophysiologic difference initiates the degenerative cascade in a SNAC wrist?





Explanation

SNAC arthritis is initiated by the abnormal mechanics of a scaphoid nonunion, causing the distal fragment to rotate and impinge on the radial styloid. In contrast, SLAC arthritis is initiated by an incompetent scapholunate ligament.

Question 33

When comparing proximal row carpectomy (PRC) to scaphoid excision and four-corner fusion (4CF) for the treatment of advanced carpal collapse, which of the following represents a known advantage of PRC?





Explanation

Because PRC does not involve an arthrodesis, it avoids the complication of nonunion, allows for earlier postoperative mobilization, and is technically simpler compared to a four-corner fusion.

Question 34

During a radial styloidectomy for SNAC Stage I arthritis, the surgeon must be careful not to excise more than 3 to 4 mm of the radial styloid. Excessive resection risks destabilizing the carpus by detaching which of the following ligaments?





Explanation

The radioscaphocapitate (RSC) ligament originates from the radial styloid. Excision of more than 3 to 4 mm of the styloid can compromise the origin of this critical volar stabilizing ligament, leading to ulnar translation of the carpus.

Question 35

A patient presents with a long-standing scaphoid nonunion. CT demonstrates advanced cystic changes and joint space loss at the capitolunate joint, but the radioscaphoid joint is relatively well preserved. What is the most appropriate management principle for this atypical pattern?





Explanation

Although SNAC progression typically affects the radioscaphoid joint before the capitolunate joint, isolated capitolunate arthritis with a scaphoid nonunion dictates the same salvage treatment principles as SNAC III. Four-corner fusion is typically required.

Question 36

To correct a severe humpback deformity in a scaphoid waist nonunion through a volar approach, what specific shape of bone graft is most frequently required to restore normal carpal kinematics?





Explanation

A wedge-shaped corticocancellous graft (typically from the iliac crest) is placed volarly to pry open the collapsed scaphoid. This corrects the flexion deformity of the distal pole and restores scaphoid length.

Question 37

The primary vascular supply to the proximal pole of the scaphoid is derived from which of the following vessels?





Explanation

The scaphoid receives 70 to 80 percent of its blood supply from the dorsal carpal branch of the radial artery, which enters at the dorsal ridge and flows retrograde to supply the proximal pole.

Question 38

A patient with a scaphoid waist nonunion develops a progressive humpback deformity. Which of the following radiographic angles best quantifies this specific deformity on a standard lateral radiograph?





Explanation

The intrascaphoid angle is measured on a lateral radiograph between lines drawn perpendicular to the proximal and distal articular surfaces. An angle greater than 45 degrees defines a humpback deformity, indicating volar collapse.

Question 39

A 28-year-old male requires surgical correction of a chronic scaphoid waist nonunion with a prominent humpback deformity and no MRI evidence of avascular necrosis. Which of the following surgical approaches and grafting techniques is most appropriate?





Explanation

A volar approach allows direct access to open the volar fracture site and correct the flexion deformity by inserting a structural corticocancellous wedge graft, restoring native scaphoid length.

Question 40

During osteosynthesis of a scaphoid waist nonunion, what is the biomechanically optimal position for the placement of a headless compression screw?





Explanation

Central placement of a headless compression screw down the longitudinal axis of the scaphoid provides the greatest biomechanical stability, maximizing stiffness and time to failure under bending loads.

Question 41

A patient with a long-standing scaphoid nonunion presents with chronic wrist pain. Radiographs demonstrate arthritis between the radial styloid and the distal scaphoid, as well as joint space narrowing at the scaphocapitate articulation. The capitolunate joint is preserved. This represents which stage of Scaphoid Nonunion Advanced Collapse (SNAC)?





Explanation

SNAC Stage II involves degenerative changes at the scaphocapitate joint in addition to the radioscaphoid joint. Stage III involves the capitolunate joint, and Stage I is isolated strictly to the radial styloid.

Question 42

A 50-year-old patient with Stage II SNAC wrist is being evaluated for a proximal row carpectomy (PRC). Which of the following intraoperative findings would be an absolute contraindication to completing the PRC?





Explanation

Proximal row carpectomy relies on a pristine articulation between the proximal capitate and the lunate fossa of the radius. Advanced capitate head arthritis is an absolute contraindication to this salvage procedure.

Question 43

A 34-year-old male with a scaphoid proximal pole nonunion has MRI findings of avascular necrosis and a significant structural cavitary defect. Which of the following vascularized bone grafts is best suited to provide both structural support and robust osteogenic potential?





Explanation

The free medial femoral condyle (MFC) flap is ideal for AVN with a structural defect because it provides robust blood supply and strong structural bone, unlike pedicled radius grafts which lack sufficient structural integrity.

Question 44

A surgeon is performing a 4-corner arthrodesis for a Stage III SNAC wrist. Prior to definitive fixation, what critical correction must be made to the remaining carpus to optimize postoperative wrist kinematics?





Explanation

In a SNAC wrist, the lunate falls into a dorsiflexed (DISI) posture. Reducing the lunate out of extension into a neutral, collinear position before fixation is critical to maximize post-operative wrist motion and grip strength.

Question 45

Which of the following MRI sequences and findings is the most reliable preoperative indicator of avascular necrosis (AVN) in a scaphoid proximal pole nonunion?





Explanation

Low signal intensity on T1-weighted imaging combined with a lack of perfusion (no enhancement) following gadolinium contrast administration is the most specific and reliable MRI indicator of proximal pole avascular necrosis.

Question 46

What is the preferred surgical approach for open reduction and internal fixation of an isolated scaphoid proximal pole nonunion without humpback deformity?





Explanation

A dorsal approach (typically between the 3rd and 4th compartments) is preferred for proximal pole pathology. It allows direct visualization of the dorsally located proximal pole and facilitates perpendicular, antegrade screw placement.

Question 47

In both SLAC and SNAC patterns of carpal collapse, the radiolunate joint is characteristically spared from early degenerative changes. Which of the following biomechanical principles best explains this phenomenon?





Explanation

The radiolunate joint has a highly spherical and congruent morphology. This geometry allows concentric rotation and prevents the abnormal asymmetric shear stresses that cause rapid degeneration in the radioscaphoid joint.

Question 48

A 24-year-old elite athlete presents with a symptomatic scaphoid waist nonunion. Radiographs reveal early osteophyte formation strictly isolated to the radial styloid, with no humpback deformity. Which surgical intervention is most appropriate to maximize function?





Explanation

For early Stage I SNAC in a young, high-demand patient, radial styloidectomy combined with scaphoid nonunion takedown, grafting, and rigid internal fixation can salvage the scaphoid and halt further carpal collapse.

Question 49

A 45-year-old manual laborer with Stage IV SNAC wrist undergoes a total wrist arthrodesis. To optimize functional grip strength, what is the ideal position for fusion of the radiocarpal joint?





Explanation

Total wrist arthrodesis is optimally positioned in 10 to 15 degrees of extension and 10 degrees of ulnar deviation. This mimics the functional resting position of the wrist and maximizes the mechanical advantage of the extrinsic finger flexors.

Question 50

A 45-year-old man with Scaphoid Nonunion Advanced Collapse (SNAC) Stage II undergoes evaluation for a salvage procedure. He strongly prefers a proximal row carpectomy (PRC) over a four-corner arthrodesis. Which of the following intraoperative findings represents an absolute contraindication to proceeding with a PRC?





Explanation

Proximal row carpectomy relies on a congruent and healthy articulation between the capitate head and the lunate fossa of the radius. Eburnation or severe arthritis of the proximal capitate is an absolute contraindication to PRC, necessitating a four-corner fusion or total wrist arthrodesis instead.

Question 51

A free medial femoral condyle (MFC) vascularized bone graft is planned for a recalcitrant scaphoid proximal pole nonunion with confirmed avascular necrosis. The surgeon must dissect which of the following source vessels to serve as the vascular pedicle for this specific graft?





Explanation

The free medial femoral condyle (MFC) vascularized bone graft is supplied by the articular branch of the descending genicular artery, with the superomedial genicular artery serving as a secondary or variant supply. This provides robust antegrade flow ideal for treating avascular nonunions.

Question 52

A 28-year-old man presents with a 2-year-old scaphoid waist nonunion. CT imaging demonstrates a 'humpback' deformity with a lateral intrascaphoid angle of 65 degrees. Which of the following is the most appropriate surgical strategy to restore carpal kinematics?





Explanation

A humpback deformity (lateral intrascaphoid angle > 45 degrees) represents fixed flexion of the distal pole. It is best corrected via a volar approach utilizing a structural opening wedge graft (Fisk-Fernandez technique) to restore scaphoid length and alignment.

Question 53

To accurately assess the true deformity, trabecular bridging, and healing of a scaphoid nonunion, computed tomography (CT) imaging should ideally be reconstructed in which of the following planes?





Explanation

The complex oblique orientation of the scaphoid within the carpus requires CT reformats along its true longitudinal axis (parasagittal and paracoronal to the scaphoid itself). Standard wrist planes often miss subtle nonunions or misrepresent the severity of a humpback deformity.

Question 54

In the natural history and progression of Scaphoid Nonunion Advanced Collapse (SNAC), which specific articular surface is classically preserved until the final stage (Stage IV) of pancarpal arthritis?





Explanation

The radiolunate joint is characteristically spared in both SLAC and SNAC wrists due to the concentric, spherical nature of the lunate fossa, which prevents abnormal translation and shear. It only becomes involved in end-stage (Stage IV) pancarpal arthritis.

Question 55

The primary blood supply to the proximal pole of the scaphoid enters through the dorsal ridge and supplies the bone in a retrograde fashion. From which parent vessel does this predominant blood supply originate?





Explanation

The dorsal carpal branch of the radial artery enters the scaphoid at the dorsal ridge, supplying the proximal 70-80% of the bone via retrograde flow. This retrograde supply is the primary reason proximal pole fractures have a high rate of nonunion and avascular necrosis.

Question 56

A 22-year-old athlete sustains an isolated proximal pole scaphoid fracture that progresses to a nonunion. There is no carpal collapse and no humpback deformity. Which surgical approach provides the best biomechanical and anatomic access for fixation?





Explanation

A dorsal approach is strongly preferred for proximal pole nonunions because it provides direct access to the proximal pole without dividing the critical volar radiocarpal ligaments. It also allows for mechanically advantageous central screw placement down the long axis of the scaphoid.

Question 57

During surgical treatment of a scaphoid waist nonunion, a tourniquet is used for initial dissection. After debridement of the nonunion site, what is the most reliable intraoperative macroscopic indicator of proximal pole viability?





Explanation

The most definitive intraoperative sign of bone viability is the presence of punctate bleeding from the cancellous bone bed after tourniquet deflation. Lack of bleeding (punctate ischemia) suggests avascular necrosis, which alters the reconstructive strategy toward vascularized grafting.

Question 58

Which of the following radiographic features reliably differentiates a Stage II SNAC wrist from a Stage II SLAC wrist?





Explanation

In a SNAC wrist, the proximal scaphoid pole remains attached to the lunate via the intact scapholunate ligament, preserving the congruent proximal radioscaphoid joint. In a SLAC wrist, the entire scaphoid subluxates, leading to arthritis involving the entire radioscaphoid fossa by Stage II.

Question 59

When comparing proximal row carpectomy (PRC) to scaphoid excision and four-corner arthrodesis (FCA) for the salvage of a SNAC wrist, long-term outcome studies generally demonstrate that PRC offers which of the following advantages?





Explanation

PRC is technically simpler, avoids hardware complications, requires less immobilization, and has a lower nonunion rate compared to FCA. Both procedures provide comparable pain relief, grip strength, and range of motion, though FCA has traditionally been favored for younger laborers due to theoretical durability.

Question 60

A patient undergoes a four-corner arthrodesis for SNAC Stage III. Which kinematic function of the wrist will be most significantly altered or abolished compared to a native wrist?





Explanation

Dart thrower's motion (oblique movement from radial extension to ulnar flexion) occurs primarily at the midcarpal joint. A four-corner arthrodesis fuses the midcarpal joint, significantly limiting this highly functional oblique motion.

Question 61

A surgeon elects to use a pedicled vascularized bone graft from the volar distal radius to treat a scaphoid nonunion with a volar deformity. This specific graft (often called the Kaji graft) is typically supplied by which of the following arteries?





Explanation

The volar pedicled bone graft from the distal radius (Kaji graft) is vascularized by the volar carpal artery, a branch of the radial artery. It is particularly useful for volar approaches when correcting a humpback deformity simultaneously.

Question 62

A 45-year-old mechanic presents with chronic wrist pain. Radiographs reveal a scaphoid nonunion with radioscaphoid and capitolunate joint space narrowing. The radiolunate joint is well-preserved, but the capitate head demonstrates severe subchondral sclerosis and cyst formation. Which of the following is the most appropriate surgical intervention?





Explanation

This patient has SNAC Stage III wrist arthropathy. Because the capitate head is arthritic, a proximal row carpectomy is contraindicated; however, an intact radiolunate joint makes scaphoid excision and four-corner fusion the ideal salvage procedure.

None

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