ABOS Part I & OITE Orthopaedic Review: HPII, Hand & Pediatric Fractures | Part 22216

Correct Answer: C

Explanation:

The case explicitly states, 'The severity of injury is directly related to the type of injectate, the volume injected, the pressure, the anatomical location, and, critically, the time elapsed between injury and surgical intervention.' It further emphasizes that 'Delayed presentation, often due to the initial innocuous appearance of the injury, is common and significantly correlates with poorer outcomes, including higher rates of infection, necrosis, amputation, and long-term joint stiffness and contracture.' Additionally, 'paint and paint thinner mixtures being among the most destructive due to their inflammatory and necrotic properties.' Therefore, the combination of a highly toxic injectate (paint thinner) and a significant delay to presentation (9 hours, exceeding the critical 6-hour window for optimal outcomes) is the most critical factor influencing the severity and risk of complications in this scenario.

• A. The patient's age and gender: While the case mentions the typical patient is a male industrial worker aged 30-50 years, this is an epidemiological observation, not a direct determinant of injury severity or outcome.
• B. The small initial appearance of the puncture wound: The case highlights that HPIIs 'often presenting with a deceptively small puncture wound,' which leads to delayed presentation. While deceptive, it's the delay it causes, not the wound size itself, that directly correlates with severity.
• D. The anatomical location (non-dominant index finger): The case notes the non-dominant index finger is the most frequently affected digit, making it a common site, but not the primary determinant of severity compared to injectate type and delay.
• E. The pressure at the nozzle (typically 2,000 to 10,000 psi): High pressure is a prerequisite for the injury mechanism, enabling deep penetration. However, the type of substance injected and the time it remains in the tissue are more critical for the severity of the subsequent chemical and inflammatory damage.

Correct Answer: D

Explanation:

The case explicitly states under 'Biomechanics of Contracture Development' that 'The most common DIP joint contracture after HPII is flexion contracture, largely due to FDP tethering and volar plate/collateral ligament scarring.' It further details that 'Injected material can track along the tendon sheath, causing chemical tenosynovitis, adhesions, and eventually FDP tendon tethering and severe flexion contracture.' The FDP tendon is the primary flexor of the DIP joint, and its adherence within the fibrous flexor sheath (specifically the A5 pulley at the DIP joint level) is a direct cause of limited extension and fixed flexion.

• A. The oblique retinacular ligament (ORL): The ORL couples DIP and PIP motion. While its scarring can affect DIP motion, it's not described as the primary cause of severe flexion contracture in the same way FDP tethering is.
• B. The terminal extensor tendon: Damage or scarring to the terminal extensor tendon would primarily result in an extension lag or, if severely scarred dorsally, potentially an extension contracture, not a flexion contracture.
• C. The true collateral ligaments of the DIP joint: While collateral ligaments can become infiltrated, scarred, and shortened, contributing to restricted motion, the case specifically highlights FDP tethering as the primary driver for flexion contracture. Collateral ligament shortening primarily restricts the full arc of motion, making it difficult to achieve both full flexion and extension.
• E. The dorsal joint capsule: Scarring or thickening of the dorsal joint capsule would primarily lead to an extension contracture, not a flexion contracture.

Correct Answer: B

Explanation:

The case unequivocally states under 'Indications for Surgical Intervention' that 'All suspected or confirmed high-pressure injection injuries' are a 'universal indication' for 'Primary Surgical Debridement (Urgent/Emergent).' It further emphasizes, 'Even in asymptomatic cases with a clear history of HPII, surgical exploration is indicated due to the deceptive nature of the injury and the high risk of delayed necrosis.' The time elapsed (4 hours) is well within the critical window for urgent intervention (ideally within 6 hours).

• A. Initiate broad-spectrum oral antibiotics and observe for 24 hours, given the mild symptoms: This is incorrect. The case stresses that HPIIs are deceptive and require immediate surgical intervention, not observation, even with mild symptoms. IV antibiotics are indicated, but not as a substitute for surgery.
• C. Obtain an MRI to delineate the extent of soft tissue involvement before deciding on surgery: While MRI can be helpful, the case states it 'should not delay urgent surgery.' The decision for surgery is based on the diagnosis of HPII, not on the extent shown by MRI.
• D. Apply a static splint in a position of safety and refer for outpatient hand therapy: This is incorrect. HPIIs are surgical emergencies. Non-operative management is not indicated for the acute phase.
• E. Administer corticosteroids to reduce inflammation and prevent fibrosis: The case notes that the use of corticosteroids is 'controversial' and 'Current guidelines generally do not recommend routine prophylactic corticosteroids.' They are not the primary or immediate management step.

Correct Answer: C

Explanation:

The case explicitly states under 'Incisions for Initial Debridement': 'Mid-axial Incisions: The preferred incision for digital HPII. These incisions are made along the non-weight-bearing surfaces of the digits... Advantages: Provide excellent exposure of the neurovascular bundles, flexor tendon sheath, extensor mechanism, and joint capsules. They minimize damage to the volar skin and preserve dorsal lymphatic drainage.'

• A. A dorsal longitudinal incision along the midline of the digit: This would not provide adequate exposure to the volar structures (flexor sheath, neurovascular bundles) which are most commonly involved in HPII.
• B. A fish-mouth (racquet) incision extending from the fingertip to the palm: The case states, 'Fish-mouth (racquet) or Zigzag (Brunner) Incisions: While useful for wide exposure in certain hand injuries, they are generally avoided in acute HPII unless extensive skin necrosis dictates their use, due to the increased risk of skin edge necrosis, scarring, and secondary contractures.'
• D. A zigzag (Brunner) incision across the volar aspect of the digit: Similar to the fish-mouth incision, Brunner incisions are generally avoided in acute HPII due to the risk of skin edge necrosis and secondary contractures, unless extensive skin necrosis is already present.
• E. A transverse incision at the level of the DIP joint: A transverse incision would provide very limited exposure and would not allow for adequate debridement of the entire flexor sheath or tracking of injectate proximally or distally.

Correct Answer: D

Explanation:

The 'Complications & Management' table in the case lists 'DIP Joint Contracture' with an incidence of 'Very high, 50-90% for significant injuries.' This is the highest incidence among the options provided for a specific DIP joint-related complication.

• A. Osteomyelitis: Incidence is listed as '<5-10%'.
• B. Complex Regional Pain Syndrome (CRPS): Incidence is listed as '5-20%'.
• C. Tendon rupture: While tendon adhesion is high, rupture is listed as 'less common, but severe.'
• E. Neuropathy / Sensory Loss: Incidence is listed as 'Up to 30%'.

Therefore, DIP joint contracture is the most common specific complication listed for significant HPIIs.

Correct Answer: C

Explanation:

Under 'Immediate Post-Operative Phase (Days 0-2 weeks)' and 'Initial Mobilization,' the case states: 'Affected DIP Joint: If wounds permit and there is no active infection or unstable fixation, very gentle, protected active DIP joint flexion and extension may be initiated within the first few days. This is crucial for preventing tendon adhesions and maintaining joint lubrication. The key is active, not passive, to promote tendon gliding.'

• A. Aggressive passive range of motion (PROM) exercises to stretch contracted tissues: The case advises 'Gentle, pain-free PROM may be introduced cautiously' in the intermediate phase, and warns 'Avoid forceful manipulation which can cause re-injury or trigger CRPS.' Aggressive PROM is contraindicated in the immediate phase.
• B. Prolonged static splinting of the DIP joint in full extension to prevent flexion: The case states, 'prolonged immobilization must be avoided.' While static splinting in a position of safety may be used for night wear, it is not the primary method for preventing contracture; early motion is.
• D. Immediate initiation of progressive resistive exercises for strengthening: Strengthening exercises are introduced in the 'Advanced Phase (Weeks 6-beyond),' not immediately post-op.
• E. Serial casting of the digit to achieve maximal correction of any developing contracture: Serial casting is a technique for 'significant, refractory contractures' in the 'Intermediate Phase,' not an immediate post-operative intervention for prevention.

Correct Answer: C

Explanation:

The case, under 'Secondary Surgical Management (for Established Contracture)' and 'Flexion Contracture,' states: 'If the FDP tendon is adherent, an extensive tenolysis is performed... If the volar plate and joint capsule are scarred and shortened, a volar plate release (often requiring resection of a portion) and anterior capsulotomy are performed to restore extension.' This patient has a significant, refractory flexion contracture (45 degrees) after extensive conservative management, with no joint destruction, making soft tissue release the indicated procedure.

• A. Continue with another 3 months of intensive hand therapy and splinting: The case indicates that surgical intervention for established contracture is considered after 'Failure of intensive non-operative therapy (typically >3-6 months).' This patient has already completed 6 months of intensive therapy, suggesting further conservative management is unlikely to be effective.
• B. Consider DIP joint arthrodesis in a functional position: Arthrodesis is described as a salvage procedure for 'severe, intractable contractures with significant joint destruction or pain.' The patient's radiographs show no significant joint destruction, making soft tissue release a more appropriate initial surgical option to preserve motion.
• D. Initiate a course of oral corticosteroids to reduce residual inflammation: The use of corticosteroids is controversial and generally not recommended for established contractures, especially after the acute inflammatory phase has subsided.
• E. Recommend hyperbaric oxygen therapy to improve tissue remodeling: HBO is considered an adjunct therapy, primarily for acute tissue salvage, and its role in established contracture remodeling is not a primary recommendation.

Correct Answer: D

Explanation:

Under 'Pre-Operative Planning & Patient Positioning' and 'Imaging,' the case states: 'X-rays: Essential to identify injected material (e.g., paint, grease often appear radiopaque), bony involvement (fractures, osteomyelitis), and the presence of gas. Baseline X-rays are crucial for future comparisons.'

• A. Magnetic Resonance Imaging (MRI): While MRI 'Can delineate soft tissue involvement, tendon sheath tracking, and extent of chemical synovitis or necrosis,' the case notes it 'May be considered if diagnosis is uncertain or to guide extent of debridement in complex cases, but should not delay urgent surgery.' It is not listed as 'essential' for initial evaluation in the same way X-rays are.
• B. Computed Tomography (CT) scan: CT is not specifically mentioned as an essential initial imaging modality in the case for HPII.
• C. Ultrasound: Ultrasound is not mentioned in the case for diagnostic workup of HPII.
• E. Arteriogram: An arteriogram is an invasive procedure used to visualize blood vessels and is not part of the routine initial diagnostic workup for HPII unless specific vascular compromise requiring revascularization is suspected, which is rare in the acute phase.

Correct Answer: E

Explanation:

The case explicitly states in the 'Introduction & Epidemiology' section: 'Non-toxic substances generally cause less severe reactions than toxic ones, with paint and paint thinner mixtures being among the most destructive due to their inflammatory and necrotic properties.' This is reinforced in the 'Summary of Key Literature / Guidelines' section: 'Literature consistently demonstrates that paint and paint thinner mixtures are the most damaging, leading to the highest rates of amputation and contracture.'

• A. Water: The case notes 'Water, air, and some solvents cause less severe reactions but still require prompt intervention.'
• B. Air: Similar to water, air causes less severe reactions.
• C. Hydraulic fluid: While hydraulic fluid is a common injectate and causes significant injury, the case specifically highlights paint and paint thinner as the most destructive.
• D. Diesel fuel: Diesel fuel is also a toxic injectate, but the case consistently identifies paint and paint thinner as having the highest destructive potential.

Correct Answer: C

Explanation:

The case explicitly states under 'Contraindications' for 'Primary HPII Debridement': 'No absolute contraindications. Relative contraindications relate to patient stability.' It further clarifies: 'Patient instability: Severe systemic medical comorbidities precluding anesthesia may necessitate temporizing measures until stabilization, though this is rare given the limb-threatening nature of HPII.' While the patient has comorbidities and signs of infection, he is described as 'hemodynamically stable,' meaning he can tolerate surgery. The limb-threatening nature of HPII mandates immediate intervention.

• A. Surgical debridement should be delayed until his fever and elevated WBC count are normalized with antibiotics: This is incorrect. Delaying debridement for HPII significantly worsens outcomes. While antibiotics should be started immediately, they are an adjunct to, not a replacement for, urgent surgery.
• B. His uncontrolled diabetes is an absolute contraindication to immediate surgical debridement: This is incorrect. The case states there are 'No absolute contraindications' for primary HPII debridement. Diabetes is a comorbidity that increases risk but does not preclude urgent, limb-saving surgery.
• D. An MRI should be performed first to rule out osteomyelitis before proceeding with surgery: This is incorrect. MRI should not delay urgent surgery. While osteomyelitis is a potential complication, the immediate priority is debridement of the injected material and necrotic tissue.
• E. Only local wound care and broad-spectrum antibiotics are necessary, given his systemic instability: This is incorrect. The patient is described as hemodynamically stable, and HPII is a surgical emergency requiring debridement, not just conservative management.

Correct Answer: C

Explanation:

Under 'Intermediate Phase (Weeks 2-6)' and 'Progressive Splinting,' the case states: 'Dynamic Splinting: Continue dynamic extension splinting for flexion contractures, with adjustable outriggers to apply gentle, constant stretch.' It also mentions 'Static Progressive Splinting: Utilize splints that allow for gradual, incremental adjustments to increase the stretch on the contracted structures.' These methods apply 'Sustained Low-Load Stretch,' which is a key principle for contracture prevention and management.

• A. Initiate forceful passive manipulation of the DIP joint to break adhesions: The case explicitly warns against this: 'Avoid forceful manipulation which can cause re-injury or trigger CRPS.'
• B. Discontinue all splinting to encourage natural movement: This is incorrect. Splinting, particularly dynamic or static progressive splinting, is crucial in the intermediate phase to address developing contractures.
• D. Refer for immediate surgical tenolysis and capsulotomy: Surgical intervention for established contracture is typically considered after 'Failure of intensive non-operative therapy (typically >3-6 months).' At Week 4, non-operative measures like splinting are the primary approach.
• E. Prescribe a period of complete immobilization to allow tissues to heal fully: The case emphasizes 'Early Mobilization' as the 'single most important factor' and states that 'Prolonged immobilization is cited as a major contributor to stiffness and contracture development.'

Correct Answer: Flexible intramedullary nails

The patient is a 7-year-old girl weighing 35 kg with a diaphyseal femur fracture. According to current pediatric orthopedic guidelines, flexible intramedullary nails (FINs) are the optimal choice for femur fractures in children aged 6-8 years, and also for children 8 years to adolescent who are under 50 kg, especially for length-stable fractures. FINs offer the advantages of early mobilization and improved patient and family convenience compared to spica casting.

• Reduction and immediate spica cast: While spica casting is an option for this age group, flexible nailing is generally preferred due to better patient and family outcomes, allowing for earlier weight-bearing and easier care.
• Lateral trochanteric intramedullary nail fixation: This method is typically reserved for older children (at least 9 years of age or older) who weigh over 49 kg, or those with length-unstable fractures. The patient's age and weight do not meet these criteria, and there are risks of greater trochanteric apophyseal arrest and osteonecrosis of the femoral head with this approach.
• Traction followed by delayed spica casting: Traction is often used as a temporary measure or for very young children, but for a 7-year-old, definitive fixation with flexible nails is generally preferred over prolonged traction and casting.
• External fixation: External fixation is a viable option for pediatric femur fractures but is usually reserved for specific situations such as severely comminuted or open fractures, or in the context of damage control orthopaedics, none of which are indicated in this case.

Correct Answer: Two 3-mm nails, 80% canal fill

The goal for flexible intramedullary nail fixation of a pediatric femur fracture is to achieve approximately 80% canal fill at the narrowest point (isthmus) to provide adequate stability without overstuffing the canal. The patient's isthmus measures 7.5 mm.

• Two 2.5-mm nails: The combined diameter would be 5.0 mm. (5.0 / 7.5) * 100% = 66.7% canal fill. This is less than the ideal 80% and could lead to inadequate fixation and risk of failure.
• Two 3-mm nails: The combined diameter would be 6.0 mm. (6.0 / 7.5) * 100% = 80% canal fill. This perfectly meets the target canal fill and provides optimal stability.
• One 3.0-mm nail and one 3.5-mm nail: The combined diameter would be 6.5 mm. (6.5 / 7.5) * 100% = 86.7% canal fill. While close to 80%, using two nails of different sizes can contribute to loss of reduction and malalignment. Additionally, exceeding 80% fill can increase the risk of complications.
• Two 3.5-mm nails: The combined diameter would be 7.0 mm. (7.0 / 7.5) * 100% = 93.3% canal fill. This significantly exceeds the 80% target, increasing the risk of iatrogenic fracture, malalignment, and other complications due to overstuffing the canal.
• One 2.5-mm nail and one 3.0-mm nail: The combined diameter would be 5.5 mm. (5.5 / 7.5) * 100% = 73.3% canal fill. This is below the ideal 80% and also involves nails of different sizes, which is generally less desirable.

Correct Answer: Pain at the knee (insertion sites)

Flexible intramedullary nailing is a generally safe and effective procedure for pediatric femur fractures. While all surgical procedures carry risks, studies have shown relatively low rates of serious complications such as infection, significant bleeding, and loss of reduction (especially with length-stable fractures). The most common complication associated with flexible intramedullary nails is irritation of the soft tissues at the nail insertion sites, typically around the knee. This irritation can cause pain and discomfort, often necessitating hardware removal once the fracture has healed. To mitigate this, it is suggested that the nail ends be left no more than 25 mm out of the bone.

• Infection: While a risk with any surgery, infection rates for flexible nailing are low.
• Bleeding: Significant bleeding requiring transfusion is uncommon with this procedure.
• Loss of reduction: With proper nail sizing and technique for length-stable fractures, loss of reduction is infrequent.
• Nonunion: Nonunion is a rare complication in pediatric femur fractures, especially with appropriate fixation.

Correct Answer: Ipsilateral overgrowth does occur, usually around 9 mm in 2 to 10-year-olds.

Femur fractures in children, particularly in the 2 to 10-year age range, are known to stimulate growth, leading to ipsilateral limb overgrowth. This phenomenon is thought to be related to hyperemia following the injury. While the range of overgrowth can vary (approximately 4 to 25 mm), the average amount of overgrowth observed in this age group is around 9 mm.

• There is no risk of overgrowth at this age; overgrowth only happens in children under 2: This is incorrect. Children under 2 years and those over 10 years are less likely to experience significant overgrowth compared to the 2-10 year age group.
• Ipsilateral overgrowth does occur, with an average of less than 5 mm: This underestimates the typical average overgrowth in this age group.
• Ipsilateral overgrowth does occur, usually between 15 and 20 mm in 2 to 10-year-olds: This overestimates the typical average overgrowth, although overgrowth within this range can occur in some cases.
• Overgrowth is a risk in children over 10, not in those younger than 10: This is incorrect. Children over 10 are less prone to significant overgrowth, while the 2-10 year age group is most susceptible.

Correct Answer: Osgood–Schlatter disease

Tibial tubercle fractures, as depicted in the image, occur more commonly in adolescents who have a history of Osgood–Schlatter disease. Osgood–Schlatter disease is an overuse injury characterized by repetitive strain across the tibial tubercle apophysis, leading to inflammation and microtrauma. While a direct causal relationship is not always demonstrated, the weakened apophysis in Osgood–Schlatter patients makes them more susceptible to avulsion fractures of the tibial tubercle.

• Patellofemoral syndrome: This condition involves anterior knee pain associated with overuse but is not specifically linked to an increased risk of tibial tubercle fractures.
• Sinding-Larsen–Johansson syndrome: Similar to Osgood–Schlatter, this is an overuse injury, but it affects the inferior pole of the patella, not the tibial tubercle, and therefore is not associated with tibial tubercle fractures.
• Patellar tendonitis: This is inflammation of the patellar tendon, which can cause pain but is not a known risk factor for avulsion fractures of the tibial tubercle itself.
• Chondromalacia patellae: This refers to softening and breakdown of the cartilage on the underside of the patella and is not a risk factor for tibial tubercle fractures.

Correct Answer: Anterior compartment—recurrent anterior tibial artery

Tibial tubercle fractures, particularly displaced ones, carry a significant risk of developing compartment syndrome. Anatomical studies and clinical experience have shown that the anterior compartment is most commonly affected. The recurrent anterior tibial artery, which courses near the tibial tubercle, is particularly vulnerable to injury or compression in the setting of this fracture, contributing to the risk of anterior compartment syndrome. Therefore, close monitoring of the neurovascular status of the anterior compartment is crucial in the perioperative period, and many surgeons will perform a prophylactic anterior compartment fasciotomy during surgery.

• Anterior compartment—medial inferior geniculate artery: The medial inferior geniculate artery supplies the knee joint and surrounding structures but is not the primary vessel at risk for compartment syndrome in the anterior compartment with this specific fracture.
• Anterior compartment—anterior tibial artery: While the anterior tibial artery is the main artery of the anterior compartment, the recurrent anterior tibial artery is more directly implicated in the immediate vicinity of the tibial tubercle fracture.
• Lateral compartment—recurrent anterior tibial artery: The recurrent anterior tibial artery is associated with the anterior compartment, not the lateral compartment.
• Lateral compartment—fibular artery: The fibular artery (also known as the peroneal artery) supplies the lateral and posterior compartments but is not typically at risk with an isolated tibial tubercle fracture.

Correct Answer: Tillaux fracture; AITFL (anterior inferior tibiofibular ligament)

The radiograph displays a Tillaux fracture, which is a specific type of transitional ankle fracture seen in adolescents. It involves an avulsion fracture of the anterolateral distal tibial epiphysis. The anterior inferior tibiofibular ligament (AITFL), a key syndesmotic ligament, inserts onto this fragment. The injury typically occurs due to external rotation forces on the foot, causing the AITFL to avulse a piece of the epiphysis.

• Tillaux fracture; ATFL (anterior talofibular ligament): The ATFL is the most commonly injured ligament in lateral ankle sprains but is not directly involved in a Tillaux fracture.
• Chopart fracture; ATFL (anterior talofibular ligament): Chopart injuries involve the midtarsal joint (talonavicular and calcaneocuboid joints) and are distinct from distal tibial physeal fractures.
• Chopart fracture; AITFL (anterior inferior tibiofibular ligament): This option incorrectly combines the Chopart injury with the AITFL.
• Chaput fracture; ATFL (anterior talofibular ligament): A Chaput fracture is another eponym for an avulsion fracture of the anterior inferior tibial tubercle, which is essentially the same anatomical injury as a Tillaux fracture but is more commonly used in adult ankle fracture classifications. However, it is associated with the AITFL, not the ATFL.

Correct Answer: Triplane fracture; Salter–Harris II on sagittal view; Salter–Harris III on anteroposterior (AP) view

The images depict a triplane fracture of the distal tibia, a complex transitional ankle fracture occurring during physeal closure. The characteristic radiographic appearance of a triplane fracture is a Salter–Harris II fracture pattern on the lateral view (sagittal plane) and a Salter–Harris III fracture pattern on the anteroposterior (AP) or coronal view. This is because the fracture involves the epiphysis, physis, and metaphysis in multiple planes.

• Salter–Harris III on sagittal view; Salter–Harris II on anteroposterior (AP) view: This reverses the classic appearance.
• Salter–Harris III on sagittal view; Salter–Harris III on anteroposterior (AP) view: This would imply a Salter-Harris III in both planes, which is not the classic description of a triplane fracture.
• Tillaux fracture: A Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis only, without a metaphyseal component, and is typically seen as a Salter-Harris III on AP/coronal views. It does not have the Salter-Harris II component on the lateral view.

Correct Answer: Traction, internal rotation of the foot, and dorsiflexion of the ankle

The classic reduction maneuver for triplane ankle fractures involves sustained axial traction to disimpact the fragments, followed by maximal internal rotation and supination of the foot, combined with dorsiflexion of the ankle. This maneuver aims to reverse the typical external rotation and pronation mechanism of injury and to achieve anatomical reduction of the articular surface.

• Traction, internal rotation of the foot, and plantarflexion of the ankle: Plantarflexion would not help reduce the fracture and may even exacerbate displacement.
• Traction, external rotation of the foot, and dorsiflexion of the ankle: External rotation is typically the mechanism of injury, so applying external rotation would worsen the displacement.
• Traction, external rotation of the foot, and plantarflexion of the ankle: Both external rotation and plantarflexion are incorrect for reduction.
• Traction, abduction of the foot, and plantarflexion of the ankle: Abduction and plantarflexion are not the correct components of the reduction maneuver for this fracture.

Correct Answer: Computed tomography scan (CT) without contrast of the left ankle

The primary goal after reducing a triplane ankle fracture is to assess the anatomical alignment of the articular surface and the physeal gap. While MRI is excellent for soft tissue evaluation (ligaments, tendons, cartilage), CT scanning is considered the gold standard for evaluating bony injury, fracture alignment, and articular congruity, especially in complex fractures like triplane fractures where displacement can be subtle on plain radiographs. A non-contrast CT scan provides sufficient detail for this purpose, and contrast enhancement would not add significant useful information for assessing bony alignment.

• Magnetic resonance imaging (MRI) without contrast: While it can show bony detail, CT is superior for precise assessment of fracture fragments and articular step-off. MRI is more for soft tissue.
• Magnetic resonance imaging (MRI) with contrast: Contrast is typically used for evaluating vascularity, tumors, or infection, not primarily for post-reduction bony alignment.
• Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC): This specialized MRI technique is used to evaluate articular cartilage health and injury, but it is not the immediate post-reduction imaging of choice for assessing fracture alignment.
• Computed tomography scan (CT) with contrast: Contrast is not necessary for evaluating bony alignment and articular congruity in this setting.

Correct Answer: Posttraumatic physeal closure of the distal tibia that does not require additional treatment

Transitional ankle fractures, such as Tillaux and triplane fractures, occur during the period of physiological physeal closure. By the time these injuries occur, a significant portion of the growth plate has already fused. Therefore, while some degree of posttraumatic physeal closure may occur, it is typically not clinically significant and does not lead to substantial limb length discrepancy or angular deformity requiring corrective osteotomy. The remaining growth potential is usually minimal.

• Posttraumatic physeal closure of the distal tibia that requires corrective valgus/varus/extension osteotomy: These are unlikely because significant growth arrest leading to angular deformity or limb length discrepancy is rare with transitional fractures due to the timing of the injury during natural physeal closure.
• Nonunion of the Thurston–Holland fragment: The Thurston–Holland fragment is associated with Salter-Harris II fractures (a component of triplane fractures). While nonunion is a theoretical complication of any fracture, it is exceedingly rare in pediatric physeal fractures, especially with appropriate treatment, and has not been reported as a common sequela for triplane fractures.

Paint thinners and solvents cause severe inflammatory responses and extensive tissue necrosis, carrying amputation rates up to 80%. Grease and water typically result in lower amputation rates and less aggressive systemic inflammatory responses.

Fluid injected into the thumb flexor sheath tracks proximally into the radial bursa. It can subsequently communicate with the ulnar bursa via a horseshoe connection in a large percentage of individuals.

This presentation describes a Seymour fracture, which is an open Salter-Harris fracture of the distal phalanx. It requires meticulous irrigation and debridement, reduction of the fracture, and repair of the nail bed to prevent osteomyelitis and growth arrest.

Nonunion of a lateral condyle fracture typically leads to a progressive cubitus valgus deformity. Over time, this valgus angulation chronically stretches the ulnar nerve, resulting in tardy ulnar nerve palsy.

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. It presents clinically as an inability to make the "OK" sign due to weakness of the FPL and the FDP to the index finger.

High-pressure injection injuries require immediate, extensive open debridement using wide mid-axial or Brunner (zigzag) incisions. Limited or percutaneous techniques fail to adequately clear the necrotizing material and do not relieve compartment pressure.

In a Bennett fracture, the volar oblique ligament retains the small volar-ulnar fragment in its anatomic position. The abductor pollicis longus (APL) acts as the primary deforming force, pulling the main metacarpal shaft proximally, dorsally, and radially.

In children under 9 years old, complete bayonet apposition is acceptable if angulation is less than 15 degrees and malrotation is less than 45 degrees. This is due to the significant remodeling potential of the pediatric forearm, particularly near the distal physis.

Femur fractures in non-ambulatory infants are highly suspicious for non-accidental trauma (child abuse). A full skeletal survey and consultation with child protective services are mandatory prior to finalizing definitive orthopedic management.

Proximal phalanx fractures typically deform with apex volar angulation. The intrinsic (interosseous) muscles pull the proximal fragment into flexion, while the central slip extends the distal fragment.

Certain injected solvents, such as turpentine or hydrocarbons, can be absorbed systemically and cause profound toxicity. This can lead to severe rhabdomyolysis and subsequent acute renal failure if not promptly debrided.

Absolute indications for operative fixation of a medial epicondyle fracture include an open fracture or incarceration of the fragment within the joint, which blocks reduction and motion. Millimetric displacement criteria (e.g., >5mm) remain controversial and are considered relative indications.

A "pink, pulseless" hand after anatomic reduction and pinning of a supracondylar humerus fracture generally indicates adequate collateral perfusion. The standard of care is close observation and admission for serial clinical checks rather than immediate vascular exploration.

In pediatric phalangeal neck fractures with severe dorsal angulation, the proximal phalanx head can buttonhole through palmar structures. The volar plate or collateral ligaments typically interpose and block reduction, necessitating open reduction.

Clinical studies show that a delay in wide surgical debridement of more than 10 hours from the time of a high-pressure injection injury significantly increases the risk of digital amputation. Early decompression and debridement are critical regardless of the injected substance.

The type of material injected is the most significant prognostic factor in HPII. Oil-based paint solvents and thinners cause a severe, immediate inflammatory response and tissue necrosis, leading to amputation rates as high as 60-80%.

The flexor tendon sheath of the index finger typically communicates with the thenar space. In contrast, the sheaths of the middle and ring fingers communicate with the midpalmar space.

With posteromedial displacement of the distal fragment, the proximal fragment displaces anterolaterally, putting the radial nerve at greatest risk. Posterolateral displacement places the anterior interosseous nerve (AIN) at risk.

A nonunion of a pediatric lateral condyle fracture typically results in progressive cubitus valgus. Over time, this valgus deformity stretches the ulnar nerve, leading to tardy ulnar nerve palsy.

In a proximal phalanx shaft fracture, the intrinsic muscles (interossei) flex the proximal fragment via their insertion on the base, while the central slip of the extensor mechanism extends the distal fragment, creating an apex-volar deformity.

The anterior oblique ligament (volar oblique ligament) anchors the small anteromedial fragment of a Bennett fracture to the trapezium. The metacarpal shaft is subluxated proximally and dorsally by the abductor pollicis longus.

The Tillaux fracture is an avulsion of the anterolateral distal tibial epiphysis caused by tension from the anterior inferior tibiofibular ligament (AITFL). This occurs in adolescents because the medial portion of the distal tibial physis closes before the lateral portion.

High-pressure injection injuries are surgical emergencies regardless of benign initial appearance. Immediate, wide open surgical debridement is required to remove the foreign material, decompress the compartments, and minimize the risk of amputation.

Incarceration of the medial epicondyle fragment within the ulnohumeral joint after closed reduction of an elbow dislocation is an absolute indication for open reduction and internal fixation.

Up to 40-50 degrees of volar angulation is typically acceptable in a 5th metacarpal neck fracture due to the high compensatory mobility of the 5th carpometacarpal joint. Angulation exceeding this requires reduction to prevent pseudoclawing.

In children under 9 years of age with a midshaft both-bone forearm fracture, up to 15-20 degrees of angulation and 45 degrees of malrotation are generally acceptable due to their substantial remodeling potential.

A 'pink, pulseless' hand following stable reduction and pinning of a pediatric supracondylar humerus fracture indicates adequate collateral perfusion. The standard of care is close observation rather than immediate vascular exploration.

In both SLAC and SNAC wrists, the radiolunate joint is characteristically spared from early osteoarthritis due to its concentric, congruent anatomy. This sparing is the mechanical basis for salvage procedures like four-corner fusion.

Injection pressures exceeding 7,000 psi are universally associated with a 100% amputation rate due to massive mechanical tissue destruction and widespread dissemination of the injected material.

Organic solvents like paint thinner cause severe, immediate liquefactive tissue necrosis and have the highest amputation rate among injected materials (often >60%). Grease and hydraulic fluid cause a profound inflammatory response and oleogranulomas but generally have lower amputation rates than paint solvents.

A Seymour fracture is an open Salter-Harris I or II fracture of the distal phalanx with an associated nail bed laceration and proximal nail plate avulsion. Appropriate management includes nail plate removal, thorough irrigation, nail bed repair, reduction of the fracture, and K-wire stabilization if unstable, along with antibiotics.

Proximal phalanx fractures typically deform with an apex volar (dorsal angulation) configuration. This is driven by the interossei flexing the proximal fragment and the central slip extending the distal fragment.

Digital blocks are contraindicated in high-pressure injection injuries because the injected volume and ensuing edema already severely compromise digital perfusion. Adding more fluid into the confined space heavily exacerbates the risk of compartment syndrome and irreversible ischemia.

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. AIN palsy presents with the inability to flex the IP joint of the thumb (flexor pollicis longus) and the distal IP joint of the index finger (flexor digitorum profundus), preventing the "A-OK" sign.

The 2nd and 3rd carpometacarpal joints are rigidly fixed, tolerating minimal angulation before causing a prominent head in the palm and pseudoclawing. For the 2nd metacarpal neck, maximum acceptable angulation is 10-15 degrees, compared to up to 40-70 degrees in the highly mobile 5th metacarpal.

While time to surgery (>10 hours) and high pressure (>7,000 PSI) are critical, the type of material injected (e.g., organic solvents/paint thinner vs. water) is the most significant prognostic factor for eventual amputation due to direct, irreversible cytotoxicity.

A Milch Type II lateral condyle fracture extends through the apophysis and exits into the joint through the trochlear groove, creating potential radioulnar instability as it violates the lateral wall of the trochlea. Milch Type I exits lateral to the trochlear groove through the capitulotrochlear groove.

In a Bennett fracture, the volar ulnar beak fragment remains anatomically held to the trapezium by the anterior oblique ligament. The entire metacarpal shaft is pulled proximally, dorsally, and radially by the uninhibited pull of the abductor pollicis longus (APL).

In the setting of a pink, pulseless hand after successful anatomic reduction and pinning of a supracondylar fracture, observation is indicated if tissue perfusion is excellent. The collateral circulation is sufficient, and the radial pulse often returns within a few days as vasospasm resolves.

The specific material injected is the single most important prognostic factor. Oil-based paints and solvents incite a massive necrotizing inflammatory response, resulting in amputation rates of up to 60-80%.

An extensile mid-lateral incision (or Brunner zigzag) is recommended to allow thorough decompression and debridement. A straight volar longitudinal incision should be avoided because it often leads to a severe flexion contracture.

This is a classic Seymour fracture, an open Salter-Harris I or II fracture of the distal phalanx. It requires nail plate removal, extensive irrigation, anatomic reduction, and repair of the nail bed to prevent osteomyelitis and premature physeal closure.

Displaced phalangeal neck fractures feature a dorsally extended distal condylar fragment. Failure to reduce this obliterates the subcondylar fossa, creating a mechanical block that severely limits PIP joint flexion.

Rotational deformities are poorly tolerated in metacarpal fractures. Any degree of finger scissoring (overlap) during active composite flexion indicates significant malrotation and requires operative reduction and fixation.

The chemical nature of the injected substance is the most critical prognostic factor for amputation. Organic solvents and paints carry a significantly worse prognosis than grease or water.

Dorsal fracture-dislocations of the PIP joint with greater than 40-50% articular involvement are inherently unstable. Volar plate arthroplasty or an osteochondral graft (like a hemi-hamate autograft) is required to restore joint stability and congruity.

The Anterior Interosseous Nerve (AIN) is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures. Injury presents with the inability to flex the IP joint of the thumb and DIP joint of the index finger, resulting in a loss of the 'OK' sign.

Pediatric lateral condyle fractures displaced more than 2 mm generally require open reduction and internal fixation (ORIF). Closed reduction is often inadequate due to soft tissue interposition and rotation, carrying a high risk of nonunion.