ABOS Part I & AAOS OITE Review: Hand & Wrist Trauma, Fight Bites, Scaphoid Fractures | Part 22205

Correct Answer: C

The correct answer is C because the most critical immediate step for a suspected 'fight bite' over an MCP joint is aggressive surgical management. This involves copious irrigation, thorough debridement of devitalized tissue, and surgical exploration to assess for joint capsule violation, tendon injury, or retained foreign bodies (e.g., tooth fragments). Delaying aggressive management significantly increases the risk of severe complications like septic arthritis, osteomyelitis, and tenosynovitis. Oral antibiotics alone (A) are insufficient for deep infections. Radiographs (B) are important but should not delay definitive surgical intervention if indicated. Topical antibiotics (D) are ineffective for deep-seated infections. Awaiting culture results (E) is impractical and dangerous, as empiric antibiotics must be initiated promptly.

Correct Answer: C

The correct answer is C because human bite infections, including 'fight bites,' are characteristically polymicrobial, involving a complex mixture of aerobic and anaerobic bacteria from the oral flora. Common aerobes include Staphylococcus aureus (which can be MRSA), Streptococcus species, and Corynebacterium. Key anaerobes include Bacteroides, Fusobacterium, and Peptostreptococcus. Eikenella corrodens, a fastidious Gram-negative rod, is a hallmark pathogen of human bite wounds and is found in over 25% of infections, even in immunocompetent individuals. Monomicrobial S. aureus (A) is inaccurate. Eikenella is not rare (B). Fungal (D) and viral (E) infections are uncommon in the acute setting of a fight bite.

Correct Answer: B

The correct answer is B because the patient's presentation, including a punctate wound over an MCP joint and signs of significant inflammation with exquisite pain on movement, is highly suggestive of septic arthritis of the MCP joint, a serious complication of fight bites. Given the delayed presentation and severe symptoms, emergent surgical irrigation and debridement of the joint, combined with intravenous broad-spectrum antibiotics, is the standard of care. Oral antibiotics (A) are insufficient. While joint aspiration (C) can confirm the diagnosis, it should not delay definitive surgical management once septic arthritis is clinically suspected. An MRI (D) may provide further detail but is not necessary before proceeding with emergent surgical exploration for a clear clinical picture of septic arthritis. Delaying definitive treatment (E) can lead to rapid joint destruction.

Correct Answer: B

The correct answer is B because Amoxicillin-clavulanate (Augmentin) is widely considered the first-line empiric antibiotic for human bite infections. It provides excellent coverage against common oral flora, including Staphylococcus (non-MRSA), Streptococcus species, anaerobes, and notably, Eikenella corrodens. Ciprofloxacin and Rifampin (A) lack adequate anaerobic coverage. Doxycycline (C) has activity against some oral flora, but Metronidazole alone does not cover aerobic organisms like Staphylococci/Streptococci. Cephalexin (D) has good Gram-positive coverage but lacks activity against anaerobes and Eikenella. Vancomycin and Gentamicin (E) are typically reserved for more severe, resistant, or nosocomial infections, with Vancomycin targeting MRSA and Gentamicin providing Gram-negative coverage, but this combination is not optimal for initial empiric human bite coverage.

Correct Answer: B

The correct answer is B because the primary reasons for obtaining plain radiographs in a suspected fight bite injury are to identify associated fractures (most commonly a 'boxer's fracture' of the metacarpal neck or head) and to detect retained foreign bodies, particularly tooth fragments, which can be radiopaque. Tooth fragments can act as a nidus for ongoing infection. While X-rays can show gross soft tissue swelling, they do not directly visualize the joint capsule (E) or assess for intrinsic muscle atrophy (A) or carpal tunnel syndrome (C). Assessing soft tissue edema (D) is a secondary finding, not the primary indication.

Correct Answer: C

The correct answer is C because any human bite wound that is suspected or confirmed to penetrate the joint capsule, a tendon sheath, or directly involve bone is an absolute indication for emergent surgical exploration and debridement. These injuries carry a high risk of developing severe infections like septic arthritis, tenosynovitis, or osteomyelitis. Superficial lacerations (A) or early presentations without deep involvement (B) might sometimes be managed non-operatively, but caution is paramount. Diabetes (D) increases risk but doesn't, by itself, mandate surgery without deep involvement. Response to oral antibiotics (E) suggests a less severe infection, but deep involvement would still warrant surgical management.

Correct Answer: A

The correct answer is A because for a suspected 'fight bite' over an MCP joint, the finger should be held in full flexion during initial assessment and irrigation. The injury typically occurs with the hand clenched in a fist, which causes the skin and extensor tendon to shift proximally relative to the MCP joint capsule. When the hand is then extended, the damaged joint capsule and any penetrating wound tract move distally and are no longer aligned with the initial skin laceration, effectively sealing off the wound and potentially trapping bacteria within the joint. Flexing the finger realigns the entry portal, allowing for thorough irrigation and exploration of the joint capsule. Full extension (B) or neutral (C) will obscure the primary injury tract.

Correct Answer: B

The correct answer is B because the 'intrinsic plus' or 'safe position' splint is generally recommended for hand immobilization following injury or surgery to prevent joint contractures. This position involves placing the wrist in 20-30 degrees of extension, the MCP joints in approximately 70-90 degrees of flexion, and the IP joints in full extension. This position maintains the collateral ligaments of the MCP joints in their elongated state, preventing shortening contractures, and avoids shortening of the IP collateral ligaments. Full extension of MCPs (A, C) can lead to MCP collateral ligament shortening. Full flexion of IP joints (A, D) can lead to IP collateral ligament shortening. Active range of motion (E) is generally not indicated initially for a severe infection requiring immobilization.

Correct Answer: C

The correct answer is C because a persistent discharging sinus tract, especially following a human bite with radiographic evidence of cortical irregularity and lucency of the bone, is highly suggestive of chronic osteomyelitis. The fight bite can directly inoculate bacteria into the bone or lead to septic arthritis which then spreads to the bone. Chronic tenosynovitis (A) would primarily involve the tendon sheath. Septic non-union (B) would be if there was a fracture that failed to heal and became infected, but the question describes bone changes not specifically related to a fracture non-union. Reactive arthritis (D) is a sterile inflammatory arthritis following infection elsewhere. Chronic cellulitis (E) is a soft tissue infection that typically would not present with bone changes or a persistent sinus tract for this duration.

Correct Answer: C

The correct answer is C because the joint capsule of the metacarpophalangeal (MCP) joint is the most commonly violated specific anatomical structure in a 'fight bite' injury. The injury typically occurs with the hand clenched in a fist, where the MCP joint is exposed. The opponent's tooth directly impacts and often lacerates the skin and the underlying joint capsule, inoculating bacteria directly into the joint space. Flexor tendon sheaths (A) are on the palmar side. Digital nerves (B) and dorsal veins (E) can be injured, but the joint capsule is the most characteristic and critical violation. The palmar aponeurosis (D) is on the palmar aspect of the hand.

Correct Answer: C

The case describes a non-displaced fracture in the most common anatomical location. According to the provided text, waist fractures are the most common, accounting for approximately 70-80% of all scaphoid fractures. Distal pole fractures are 5-10%, proximal pole fractures are 15-20%, and tubercle fractures are rare. Vertical oblique fractures are a pattern of waist fracture, but not a distinct anatomical location with a separate incidence percentage in the provided text.

Incorrect Options:

• A) Distal pole fracture; 5-10%: While a possible location, it is not the most common.
• B) Tubercle fracture; <5%: These are rare and generally stable, but not the most common type.
• D) Proximal pole fracture; 15-20%: These are less common than waist fractures and carry the highest risk of AVN, but are not the most frequently encountered.
• E) Vertical oblique fracture; Not specified, but rare: This describes a fracture pattern, often mechanically unstable, but not the most common anatomical location in terms of overall incidence.

Correct Answer: C

The text explicitly states that the scaphoid's blood supply is highly vulnerable. The dorsal carpal artery branch (from the radial artery) supplies the majority (70-80%) of the scaphoid via intraosseous branches entering the dorsal ridge. Crucially, these vessels provide a retrograde blood supply to the proximal pole. Fractures through the scaphoid waist or proximal pole often compromise this retrograde flow, especially if displaced, which explains the heightened susceptibility of the proximal pole to avascular necrosis (AVN).

Incorrect Options:

• A) Primarily supplied by the palmar superficial branch of the radial artery, leading to a low risk of AVN: The palmar superficial branch supplies only the distal tubercle and a small portion of the distal pole (20-30%), not the majority of the scaphoid or the proximal pole.
• B) Primarily supplied by the dorsal carpal artery branch of the radial artery, providing an antegrade flow to the proximal pole: While the dorsal carpal artery branch is the primary supply, the flow to the proximal pole is retrograde, not antegrade.
• D) Primarily supplied by direct branches from the ulnar artery, ensuring robust vascularity: The primary blood supply to the scaphoid is from the radial artery, not the ulnar artery.
• E) Receives dual blood supply from both dorsal and palmar branches, making AVN rare: While there are dorsal and palmar contributions, the proximal pole's reliance on retrograde flow makes it highly susceptible to AVN, not rare.

Correct Answer: C

The text clearly describes the progression of SNAC wrist: "It typically begins at the radial styloid-scaphoid articulation, progresses to the capitolunate joint, and spares the radiolunate joint until late stages." This specific pattern of degenerative arthritis is a hallmark of SNAC wrist, resulting from altered carpal mechanics due to chronic scaphoid nonunion.

Incorrect Options:

• A) Begins at the radiolunate joint, then progresses to the capitolunate joint, and finally the radioscaphoid articulation: This is incorrect as the radiolunate joint is typically spared until late stages, and the initial involvement is at the radioscaphoid articulation.
• B) Begins at the capitolunate joint, then progresses to the radioscaphoid articulation, and finally the radiolunate joint: This sequence is incorrect. The radioscaphoid articulation (specifically radial styloid-scaphoid) is the initial site of degeneration.
• D) Begins simultaneously at all carpal articulations due to global carpal collapse: SNAC wrist follows a predictable, sequential pattern of degeneration, not simultaneous involvement of all joints.
• E) Primarily affects the scaphotrapeziotrapezoid (STT) joint, with later involvement of the proximal carpal row: While the STT joint can be affected in other carpal pathologies, the primary progression of SNAC wrist is as described in option C.

Correct Answer: C

The text lists specific indications for operative management. A scaphoid sagittal angle > 60 degrees (indicating humpback deformity) and displacement > 1 mm are both explicit criteria for surgical intervention, as they signify an unstable fracture pattern with a high risk of malunion and altered carpal kinematics. The patient's CT scan confirms both of these critical findings.

Incorrect Options:

• A) Patient's profession as a high-demand athlete: While a valid consideration for operative management (high-demand patients desiring early return to activity), it is a patient factor, not a direct fracture characteristic indicating instability or displacement. The fracture characteristics in option C are more compelling indications for surgery in this specific case.
• B) Non-displaced waist fracture: The initial radiographs showed a non-displaced fracture, but the CT scan revealed displacement and angulation, making this option incorrect based on the full clinical picture. Non-displaced waist fractures can often be treated non-operatively.
• D) Risk of prolonged immobilization with non-operative treatment: This is a general advantage of surgical fixation (allowing earlier mobilization), but it is not the primary or most compelling indication for surgery based on the specific fracture characteristics of displacement and angulation.
• E) The fracture being a waist fracture: Waist fractures are the most common type, and while many are treated operatively, the location alone is not a definitive indication for surgery without other factors like displacement, angulation, or instability.

Correct Answer: C

The text states that distal tubercle fractures are generally stable and heal reliably with short-term immobilization, making them an indication for non-operative management. Furthermore, the patient has significant medical comorbidities (uncontrolled diabetes, severe cardiac disease) which are listed as contraindications for operative management due to increased surgical risk. Therefore, conservative management with immobilization is the most appropriate initial strategy.

Incorrect Options:

• A) Open reduction and internal fixation with a headless compression screw: This is an operative intervention. Given the stable nature of a tubercle fracture and the patient's severe comorbidities, surgery is contraindicated.
• B) Percutaneous screw fixation: This is also an operative intervention, and while minimally invasive, it still carries surgical risks that are heightened by the patient's comorbidities. It is not indicated for a stable tubercle fracture.
• D) Vascularized bone grafting due to age-related vascular compromise: Vascularized bone grafting is a complex procedure reserved for nonunions with AVN or challenging cases, not for an acute, non-displaced tubercle fracture. Age alone does not necessitate this.
• E) Proximal row carpectomy to prevent future arthritis: Proximal row carpectomy is a salvage procedure for advanced arthritis (e.g., SNAC wrist) and is not indicated for an acute, non-displaced fracture.

Correct Answer: C

The text explicitly states: "Computed Tomography (CT) Scan: The gold standard for assessing fracture displacement, comminution, and fragment orientation, especially in waist and proximal pole fractures. Axial, coronal, and sagittal reconstructions are critical for 3D understanding. It aids in surgical approach selection and screw trajectory planning." This makes CT the ideal choice for detailed fracture assessment and surgical planning.

Incorrect Options:

• A) Magnetic Resonance Imaging (MRI): MRI is highly useful for diagnosing occult scaphoid fractures not visible on radiographs or CT, and for detecting bone contusion or ligamentous injuries. However, for detailed assessment of fracture geometry, displacement, and comminution for surgical planning, CT is superior.
• B) Bone Scan: Rarely used for acute fractures, it can confirm occult fractures by showing increased uptake but provides limited anatomical detail for surgical planning.
• D) Ultrasound: While useful for soft tissue assessment, ultrasound has limited utility for diagnosing scaphoid fractures and assessing their detailed characteristics.
• E) Repeat plain radiographs in 10 days: This is a common initial strategy for occult fractures, but it is not an advanced imaging modality and does not provide the detailed 3D information needed for surgical planning, especially if displacement or comminution is suspected.

Correct Answer: C

The text describes the deep dissection for the Volar (Henry) Approach: "Deep to the FCR, the radial artery is identified. It runs between the FCR and the flexor pollicis longus (FPL). The radial artery is carefully retracted radially, often with the FPL." Protection of the radial artery is critical to prevent vascular compromise.

Incorrect Options:

• A) Ulnar artery: The ulnar artery is located on the ulnar side of the wrist and is not typically encountered or at risk during a volar radial approach to the scaphoid.
• B) Median nerve: The median nerve is located more centrally in the carpal tunnel and is not the primary neurovascular structure retracted radially in this approach. The palmar cutaneous branch of the median nerve should be protected, but the main trunk is not typically retracted radially.
• D) Dorsal cutaneous branch of the ulnar nerve: This nerve is on the dorsal aspect of the wrist and is not relevant to a volar approach.
• E) Posterior interosseous nerve: This nerve is a branch of the radial nerve, located dorsally in the forearm, and is not at risk during a volar approach to the scaphoid.

Correct Answer: D

The text outlines the management of nonunion and AVN: "For cases with established AVN of the proximal pole or recalcitrant nonunions, vascularized bone grafts (e.g., 2,3-ICSRA pedicled graft, free medial femoral condyle flap) have shown superior union rates by providing a direct blood supply." The presence of AVN in the proximal pole makes a vascularized graft the preferred option to enhance revascularization and promote healing, especially with early carpal collapse, indicating a need to restore scaphoid integrity.

Incorrect Options:

• A) Non-vascularized bone grafting with revision internal fixation: This is typically used for stable nonunions without significant AVN or bone loss. Given the established AVN of the proximal pole, a non-vascularized graft would be less effective in promoting revascularization.
• B) Scaphoidectomy and four-corner arthrodesis (4CA): This is a salvage procedure for advanced stages of post-traumatic arthritis (SNAC wrist). While there is early carpal collapse, it's not described as advanced arthritis, and the primary goal should still be to achieve union and preserve the scaphoid if possible.
• C) Proximal row carpectomy (PRC): Similar to 4CA, PRC is a salvage procedure for established arthritis. It involves removing the entire proximal carpal row and is considered when the articular surfaces are significantly damaged.
• E) Total wrist arthrodesis: This is an end-stage salvage procedure for severe, pan-carpal arthritis or failed previous surgeries, resulting in complete loss of wrist motion. It is too aggressive for a case with early carpal collapse where scaphoid reconstruction is still feasible.

Correct Answer: C

The text describes Phase 2 of rehabilitation (Controlled Active Range of Motion) as typically beginning at "Weeks 6/8-12." It explicitly states: "Repeat radiographs (and potentially CT scan) at 6-8 weeks to confirm signs of fracture healing. If healing is sufficient, progress to active ROM." This indicates that the transition from full-time immobilization to active ROM is contingent on radiographic evidence of initial healing, usually around 6-8 weeks for stable fixation.

Incorrect Options:

• A) Immediately post-operatively: While some surgeons may allow immediate gentle ROM with exceptionally rigid fixation and high patient compliance, the typical protocol for stable fixation still involves an initial period of immobilization (4-6 weeks) to protect healing.
• B) At 2-3 weeks, after initial wound healing: This is generally too early for active wrist ROM, as significant bone healing has not yet occurred, and the fracture site remains vulnerable.
• D) At 12 weeks, regardless of radiographic healing: While 12 weeks is within the broader range for rehabilitation progression, the text emphasizes that progression is based on "initial radiographic signs of healing," which typically occur earlier than 12 weeks for stable fixation. Waiting until 12 weeks regardless of healing might delay rehabilitation unnecessarily.
• E) At 4-6 months, after complete radiographic union: This timeframe is typically for return to full activity or contact sports, not for initiating controlled active wrist ROM. Complete union often takes longer, but active ROM starts earlier.

Correct Answer: B

The text states under "Diagnostic Algorithms": "MRI is highly sensitive for occult fractures and bone contusions... Meta-analyses have demonstrated the superior diagnostic accuracy of MRI over plain radiographs and bone scans for occult scaphoid fractures." This directly supports MRI as the superior modality for detecting occult fractures when initial radiographs are negative.

Incorrect Options:

• A) Computed Tomography (CT) Scan: While CT is the gold standard for assessing fracture displacement, comminution, and fragment orientation for surgical planning, MRI is generally considered more sensitive for detecting occult fractures (bone edema/contusion) not visible on initial radiographs or even early CT.
• C) Diagnostic Ultrasound: Ultrasound has limited diagnostic accuracy for scaphoid fractures, especially occult ones, compared to MRI or CT.
• D) Arthrography: Arthrography is primarily used to assess ligamentous injuries and cartilage integrity, not for diagnosing occult bone fractures.
• E) Fluoroscopy with stress views: Fluoroscopy is used intraoperatively for guiding fixation or dynamically assessing carpal instability, but it is not an advanced imaging modality for detecting occult fractures.

For proximal pole scaphoid fractures, a dorsal approach is preferred as it avoids dividing the critical volar radioscaphocapitate ligament and allows for direct, central-central screw placement which biomechanically provides the greatest load to failure.

Fight bites occur with a clenched fist. Examining the hand in full flexion replicates the injury position, revealing capsular and extensor tendon lacerations that glide proximally when the hand is extended.

In both SLAC and SNAC wrists, the radiolunate joint is characteristically spared from arthritic changes. This preservation is the physiological basis for performing a proximal row carpectomy or scaphoid excision with 4-corner fusion.

Eikenella corrodens is a Gram-negative rod highly resistant to clindamycin, first-generation cephalosporins, and macrolides. In penicillin-allergic patients, a fluoroquinolone (like ciprofloxacin) combined with clindamycin or metronidazole provides optimal coverage.

The medial femoral condyle (MFC) free vascularized bone graft is reliably based on the articular branch of the descending genicular artery. It provides structurally robust, vascularized bone for challenging scaphoid nonunions.

The Watson scaphoid shift test evaluates the integrity of the scapholunate ligament. A palpable 'clunk' and pain as the scaphoid subluxates dorsally over the radial rim indicates SL ligament incompetence.

A dorsal longitudinal approach allows extension of the traumatic wound. Splitting the sagittal band laterally allows access to the MCP joint without disrupting the central extensor slip, facilitating thorough debridement.

The deep motor branch of the ulnar nerve curves directly around the distal aspect of the hook of the hamate. It is highly susceptible to injury during excision of the hamate hook.

A humpback deformity occurs when the distal scaphoid pole flexes. Without the normal stabilizing link of an intact scaphoid, the lunate extends with the triquetrum, resulting in a Dorsal Intercalated Segment Instability (DISI) posture.

Approximately 70-80% of the scaphoid's blood supply comes from the dorsal carpal branch of the radial artery, which enters the dorsal ridge distally and flows in a retrograde fashion to the proximal pole.

In Mayfield's progressive stages of perilunate instability, Stage IV is characterized by the complete volar dislocation of the lunate into the carpal tunnel, often causing acute median neuropathy.

MRI is the gold standard for diagnosing occult scaphoid fractures acutely, possessing a sensitivity and specificity approaching 100%. It enables immediate diagnosis and avoids unnecessary prolonged casting.

The anterior oblique ligament (AOL) securely holds the small volar ulnar fragment to the trapezium, while the abductor pollicis longus (APL) pulls the metacarpal shaft proximally and radially.

Proximal row carpectomy relies on the articulation between the capitate head and the lunate fossa of the radius. If the capitate head is arthritic (common in advanced SNAC III), PRC is contraindicated, and 4-corner fusion is preferred.

Multiple studies have shown that there is no statistically significant difference in union rates or functional outcomes when treating non-displaced scaphoid waist fractures with a short arm cast versus a thumb spica cast.

Joint penetration and extensor tendon involvement are definitive indications for surgical debridement and washout in fight bites due to the extremely high risk of deep space infection and septic arthritis.

The volar approach is ideal for humpback waist nonunions because it avoids the critical dorsal blood supply. It also easily accommodates a volar wedge graft to restore scaphoid length and correct the DISI deformity.

Pain with passive extension is one of Kanavel's four cardinal signs of pyogenic flexor tenosynovitis. The others are fusiform swelling, flexed resting posture, and tenderness along the flexor tendon sheath.

The 1,2 ICSRA lies on the surface of the extensor retinaculum between the first dorsal compartment (APL, EPB) and the second dorsal compartment (ECRL, ECRB).

Failure to anatomically reduce a trans-scaphoid perilunate dislocation inevitably leads to scaphoid nonunion. This disrupts the carpal column biomechanics, progressing rapidly to Scaphoid Nonunion Advanced Collapse (SNAC).

Amoxicillin-clavulanate provides excellent coverage for Eikenella corrodens, Staphylococcus, and Streptococcus species typical of human bites. Eikenella is classically resistant to first-generation cephalosporins and clindamycin.

Fight bites occur with the MCP joint in flexion. If examined only in extension, the proximal retraction of the extensor tendon and capsule may conceal the arthrotomy, leading to missed septic arthritis.

The major blood supply to the scaphoid is from the dorsal carpal branch of the radial artery, which enters the dorsal ridge distally and provides retrograde flow. This makes proximal pole fractures highly susceptible to delayed union or avascular necrosis.

MRI is the gold standard for diagnosing occult scaphoid fractures due to its near 100% sensitivity and specificity. Early MRI prevents unnecessary prolonged casting in athletes with mere sprains and ensures timely treatment for true fractures.

In both SNAC and SLAC wrist arthritis, the radiolunate joint is characteristically spared. This preservation allows for carpal salvage procedures like a proximal row carpectomy or four-corner fusion.

The dorsal approach is preferred for proximal pole scaphoid fractures. It allows direct visualization of the proximal pole, ensures central screw placement, and avoids disrupting the vital volar radiocarpal ligaments.

In a Bennett fracture, the abductor pollicis longus (APL) pulls the metacarpal shaft proximally and dorsally. The volar ulnar base fragment remains anatomically located, held by the strong anterior oblique ligament.

The dorsal portion of the scapholunate interosseous ligament is the thickest and strongest component. It serves as the primary stabilizer of the scapholunate articulation, and its isolated disruption leads to significant instability.

Acute median nerve neuropathy (carpal tunnel syndrome) is the most common neurologic complication associated with lunate and perilunate dislocations. Symptoms include numbness, tingling, or pain in the volar radial three-and-a-half digits.

Proximal row carpectomy (PRC) relies on a preserved, cartilage-covered proximal capitate to articulate with the lunate fossa of the radius. In Stage III SLAC wrist, capitolunate arthritis is present, making PRC contraindicated.

The carpometacarpal joint of the small finger has significant compensatory mobility in the sagittal plane. Therefore, volar angulation of up to 40 to 50 degrees is generally well tolerated in 5th metacarpal neck fractures without causing symptomatic pseudo-clawing.

The volar percutaneous or mini-open approach utilizes the STT joint to access the distal pole. To place the screw in the central axis of the scaphoid, the starting point must be through the edge of the trapezium or the STT joint articular surface.

Eikenella corrodens is a fastidious, facultatively anaerobic gram-negative rod that is capnophilic (requires a CO2-enriched environment for optimal growth). It is classically associated with human bite wounds and is resistant to clindamycin and first-generation cephalosporins.

Mayfield Stage IV represents a complete volar lunate dislocation into the carpal tunnel. The sequence is: I (scapholunate dissociation), II (perilunate dislocation with capitate dorsal), III (lunotriquetral disruption), and IV (volar lunate dislocation).

Pain with passive extension of the digit is generally considered the earliest and most sensitive sign of infectious pyogenic flexor tenosynovitis. It effectively stretches the inflamed tendon sheath, eliciting immediate, disproportionate pain.

Proximal pole scaphoid fractures have a high rate of avascular necrosis and nonunion due to retrograde blood supply. Surgical fixation is generally recommended even for non-displaced proximal pole fractures to optimize union rates.

The dorsal approach (often utilizing the interval between the 3rd and 4th compartments) is preferred for proximal pole scaphoid fractures. It allows central screw placement directly down the longitudinal axis of the scaphoid without damaging the articular surface.

Eikenella corrodens is a common pathogen in human 'fight bite' injuries. It is classically susceptible to penicillin and amoxicillin but notoriously resistant to clindamycin and first-generation cephalosporins.

SNAC Stage II involves arthritis of the radioscaphoid and scaphocapitate joints. Appropriate salvage options include scaphoid excision with four-corner fusion or a proximal row carpectomy (if the capitate head is preserved).

The scaphoid receives 70-80% of its blood supply from the dorsal carpal branch of the radial artery, which enters at the dorsal ridge and supplies the proximal pole in a retrograde fashion.

In a Bennett fracture, the volar ulnar beak fragment is held by the anterior oblique ligament. The main metacarpal shaft is displaced dorsally, proximally, and radially by the pull of the abductor pollicis longus (APL).

Fight bites occur with a clenched fist. When the hand is subsequently extended for examination, the lacerated extensor tendon and dorsal capsule glide proximally, hiding the entry path into the joint.

MRI is the most sensitive and specific modality for diagnosing occult scaphoid fractures in the acute setting (<24-48 hours) as it easily detects the associated bone marrow edema. CT is highly specific but less sensitive acutely.

A scaphoid waist nonunion with volar collapse causes a humpback deformity. Without the stabilizing link of the distal scaphoid, the lunate extends along with the intact triquetrum, resulting in a DISI deformity.

Perilunate injuries are classified into lesser arc (purely ligamentous) and greater arc (involving fractures of the surrounding carpal bones). A trans-scaphoid perilunate dislocation is a classic greater arc injury.

Human bite wounds have a very high risk of aggressive polymicrobial infection. The standard of care mandates formal surgical debridement while leaving the wound open to heal by secondary intention or delayed closure.

The scaphoid is perfused primarily by the dorsal carpal branch of the radial artery, which enters distally and flows retrogradely toward the proximal pole. This tenuous retrograde blood supply leaves the proximal pole highly susceptible to ischemia and avascular necrosis following a fracture.

Eikenella corrodens is a fastidious Gram-negative bacillus frequently isolated from clenched-fist 'fight bite' injuries. It is classically resistant to first-generation cephalosporins and clindamycin, but demonstrates excellent susceptibility to amoxicillin-clavulanate and penicillin.

Clenched-fist injuries occur with the MCP joints in marked flexion, driving the tooth through the skin, extensor tendon, and joint capsule. When the fingers are subsequently extended, the lacerated extensor tendon and capsular defect retract proximally, sealing the bacterial inoculum deep within the joint.

Displaced proximal pole scaphoid fractures have a high rate of nonunion and avascular necrosis. Open reduction and internal fixation via a dorsal approach is preferred, as it provides direct access to the proximal fragment and allows for biomechanically advantageous central screw placement.

Hook of hamate fractures frequently occur from repetitive impact in racquet sports or golf. If left untreated, chronic friction against the irregular, nonunited fracture site can lead to tenosynovitis and subsequent attritional rupture of the adjacent FDP tendons, most commonly affecting the small finger.

Fractures of the fifth metacarpal neck can tolerate significant volar angulation due to the high compensatory mobility of the fourth and fifth carpometacarpal joints. Volar angulation up to 40 to 50 degrees is generally well tolerated and can be treated non-operatively.

Scaphoid Nonunion Advanced Collapse (SNAC) progresses through predictable stages based on abnormal carpal kinematics. Stage I involves the radial styloid, Stage II progresses to the scaphocapitate joint, and Stage III involves the periscaphoid articulation, while characteristically sparing the radiolunate joint.

In a Bennett fracture, the small volar ulnar beak fragment is retained anatomically by the anterior oblique ligament. The larger metacarpal shaft is displaced proximally, dorsally, and radially primarily by the strong pull of the abductor pollicis longus (APL) tendon.

Pediatric scaphoid fractures most commonly involve the distal pole and generally have an excellent prognosis due to a robust blood supply in this region. Nonoperative management with a short arm cast is highly successful, even with mild displacement, and remains the standard of care.

Operative exploration of a clenched-fist bite wound requires extending the laceration to fully visualize the joint capsule and retracted extensor tendon. This is typically done using transverse extensions or a modified Bruner incision to avoid longitudinal scars that cross the joint crease and cause severe flexion contractures.