ABOS Part I Orthopaedic Surgery Review: Humerus Fractures & Hand Infections | Part 22141

Correct Answer: C

The case material explicitly states that for the vast majority of closed, non-comminuted midshaft humerus fractures, functional bracing remains a highly effective initial treatment, with union rates often exceeding 90%. The acceptable alignment criteria for non-operative treatment are less than 20 degrees of anterior angulation, less than 30 degrees of varus angulation, and less than 3 cm of shortening. This patient's fracture falls well within these acceptable parameters (15 degrees varus, 10 degrees anterior, 1 cm shortening). Her low-energy mechanism and lack of neurovascular deficit further support non-operative management.

Option A (Immediate ORIF with LCP via posterior approach) is incorrect. While ORIF is an option for certain indications, it is not the most appropriate initial management for a stable, closed fracture within acceptable alignment parameters, especially given the higher complication rates associated with operative management compared to non-operative care for suitable fractures.

Option B (Urgent intramedullary nailing) is incorrect for similar reasons. While IM nailing is a valid operative technique, it is not indicated as the primary treatment for this stable fracture. Furthermore, IM nailing can be associated with shoulder or elbow pain from entry portals.

Option D (Surgical exploration of the radial nerve) is incorrect. The patient has no neurovascular deficits. The case material clearly states that radial nerve palsy in closed humerus fractures should initially be observed, as spontaneous recovery occurs in 70-90% of cases. Immediate exploration is reserved for specific scenarios like open fractures with nerve deficits or evolving palsy with increasing soft tissue compromise, none of which apply here.

Option E (Admission for skeletal traction) is an outdated and generally not indicated primary treatment for midshaft humerus fractures in the modern era, especially for a stable, closed fracture amenable to functional bracing.

Correct Answer: B

The case material explicitly states: "The most critical neurovascular structure in relation to the midshaft humerus is the radial nerve. It spirals obliquely from posterior to lateral across the midshaft humerus within the spiral (radial) groove, accompanied by the profunda brachii artery. Proximally, it lies between the medial and lateral heads of the triceps." The image provided, showing the posterior aspect of the humerus, visually reinforces this anatomical course, highlighting the nerve's vulnerability in this region and its relationship to the triceps muscle.

Option A (The radial nerve lies anterior to the brachialis muscle, accompanied by the brachial artery) is incorrect. The brachial artery and median nerve are typically found anteriorly, medial to the humerus, while the radial nerve is posterior and lateral in the midshaft. The radial nerve lies deep to the brachialis and brachioradialis in the distal third of the arm, not anterior to the brachialis in the midshaft.

Option C (The radial nerve is found in the deltopectoral interval, superficial to the pectoralis major) is incorrect. The deltopectoral interval is an anterior approach to the proximal humerus, and the radial nerve is not found there. The cephalic vein is typically found in this interval.

Option D (The radial nerve pierces the medial intermuscular septum to lie anterior to the medial epicondyle) is incorrect. The radial nerve pierces the lateral intermuscular septum to lie anterior to the lateral epicondyle. The ulnar nerve is the one that passes posterior to the medial epicondyle.

Option E (The radial nerve is typically located between the biceps brachii and brachialis muscles in the midshaft) is incorrect. The musculocutaneous nerve is found between the biceps and brachialis muscles. The radial nerve is posterior and lateral in the midshaft.

Correct Answer: D

The case material states that for comminuted fractures, "bridging principles to restore length and alignment without direct compression of fragments" are required. It also highlights that "Plate fixation offers superior resistance to bending and torsional forces, especially with longer plates and more screws (increasing working length). The principle of relative stability (bridging plates) is often employed for comminuted fractures." Furthermore, the summary mentions that "For comminuted midshaft fractures, MIPO plating techniques using LCPs are gaining popularity due to their potential to preserve soft tissue and provide stable fixation with relative stability principles." MIPO with an LCP applying relative stability (bridging) is ideal for comminuted fractures as it preserves periosteal blood supply and allows for secondary bone healing.

Option A (Dynamic compression plating (DCP) with interfragmentary lag screws for absolute stability) is incorrect. Absolute stability with lag screws and compression plating is typically used for simple transverse or short oblique fractures to achieve primary bone healing, not for highly comminuted fractures where direct compression would devitalize fragments and a bridging technique is preferred.

Option B (Intramedullary nailing with static locking, as it is a load-sharing device that resists bending and axial loads effectively) is a plausible option, as IM nailing is a load-sharing device promoting secondary healing. However, the question asks for the generally preferred strategy for a highly comminuted fracture, and the case specifically mentions MIPO plating for comminuted fractures. While nailing is effective for bending and axial loads, it is "less effective against rotational forces unless adequately locked proximally and distally." Plate fixation offers superior resistance to bending and torsional forces, making MIPO plating often preferred for highly comminuted patterns where precise alignment and rotational control are critical, especially when considering the potential for shoulder/elbow pain with nailing.

Option C (External fixation) is generally reserved for open fractures with severe soft tissue damage, highly contaminated wounds, or as a temporary measure in polytrauma, not typically as a definitive fixation for a closed comminuted midshaft humerus fracture.

Option E (Tension band wiring) is primarily used for avulsion fractures or fractures around joints (e.g., olecranon, patella) where muscle pull creates a tension force, converting it into compression. It is not suitable for stabilizing a highly comminuted midshaft humerus fracture.

Correct Answer: E

The case material lists several factors that, individually or in combination, serve as strong indications for operative management:

• Failed non-operative treatment: "Persistent unacceptable alignment, nonunion, or patient intolerance of brace." This patient has progressive varus angulation exceeding 35 degrees, which is well beyond the acceptable 30 degrees.
• Segmental fractures: These are listed as a relative indication for operative intervention.
• Morbid obesity or non-compliant patients: "Where functional bracing is challenging." This patient fits both descriptions.

While poorly controlled diabetes (Option D) is a risk factor for nonunion, it is not listed as a direct indication for operative management itself, but rather a comorbidity that influences the decision-making process and prognosis. However, the combination of failed non-operative treatment, a segmental fracture, and patient factors (morbid obesity, non-compliance) makes operative management the most appropriate choice. Therefore, 'All of the above' (considering the individual factors as contributing to the overall decision) is the best answer.

Option A (The presence of a segmental fracture alone) is a relative indication, but not the sole compelling factor here.

Option B (The patient's morbid obesity and non-compliance) are relative indications, making bracing difficult, but not the only reasons for surgery.

Option C (The failure of non-operative treatment) is a strong indication, but combined with the other factors, the decision is even more robust.

Since all listed factors (A, B, C, and the underlying risk from D) contribute significantly to the decision for operative management, 'All of the above' is the most comprehensive and accurate answer.

Correct Answer: A

The case material states: "The prevailing consensus...is that radial nerve palsy in closed humerus fractures should initially be observed. Spontaneous recovery occurs in 70-90% of cases within 3-6 months. Surgical exploration is indicated if there is no clinical or electrophysiological evidence of recovery after 3-6 months..." In this scenario, 3 months have passed with no clinical or electrophysiological recovery, placing the patient at the threshold for considering exploration. Given the lack of any recovery, immediate surgical exploration is the most appropriate next step to assess the nerve's condition (e.g., entrapment, partial laceration) and potentially perform nerve repair or grafting if indicated.

Option B (Continue observation for another 3 months) is incorrect. While recovery can sometimes extend beyond 6 months, the guideline specifically states exploration is indicated if no recovery is seen after 3-6 months. Waiting longer without any signs of recovery would delay potential intervention and worsen outcomes if the nerve is transected or entrapped.

Option C (Initiate tendon transfers) is incorrect as a primary next step. Tendon transfers are typically considered if recovery does not occur after 9-12 months, after nerve exploration and repair attempts have failed or are deemed not feasible.

Option D (Order a high-resolution MRI) is incorrect. While MRI can visualize nerve continuity, it is not the definitive diagnostic or therapeutic step when clinical and electrophysiological studies indicate no recovery. Surgical exploration remains the gold standard for direct assessment and potential repair.

Option E (Prescribe corticosteroids) is incorrect. Corticosteroids are not indicated for radial nerve palsy in this context and would not promote nerve regeneration or recovery from a mechanical injury.

Correct Answer: C

The case material explicitly states under Pre-Operative Planning: "Angiography: Indicated if vascular injury is suspected (e.g., diminished pulses, expanding hematoma)." This patient presents with both diminished radial pulses and an expanding hematoma, which are classic signs of a vascular injury requiring urgent assessment and potential repair. Vascular injury is an absolute indication for operative intervention, and its identification is paramount.

Option A (Standard AP and lateral radiographs) are essential for fracture characterization but will not provide information about the vascular status. While they are always obtained, they are not the most critical immediate study for the suspected vascular injury.

Option B (Computed Tomography (CT) scan) is useful for complex comminuted fractures or articular involvement but is not the primary study for acute vascular injury. A CT angiogram (CTA) could be an alternative to conventional angiography, but the question specifically asks about angiography, which is the gold standard for detailed vascular assessment.

Option D (Electromyography (EMG) and nerve conduction studies (NCS)) are used to assess nerve function and prognosis, typically 6-8 weeks after injury, not for acute assessment of vascular compromise. The radial nerve palsy, while present, is secondary to the immediate life-threatening vascular concern.

Option E (Magnetic Resonance Imaging (MRI) of the brachial plexus) is not indicated in the acute setting for a midshaft humerus fracture with suspected vascular injury. It might be considered for complex brachial plexus injuries, but not as the immediate critical study here.

Correct Answer: B

The case material explicitly states under 'Patient Positioning': "Lateral Decubitus Position: Most commonly used for posterior plating approaches (Henry or triceps splitting). ...Advantages: Excellent access to the entire posterior and posterolateral aspects of the humerus, allowing for easy identification and protection of the radial nerve. Good visualization for direct reduction." This directly matches the description in Option B.

Option A (Supine position with the arm draped over an arm board) is primarily indicated for antegrade intramedullary nailing or anterior plating, not typically for a posterior approach. The advantage listed is for antegrade nailing, not posterior plating.

Option C (Beach chair position) is a variation of the supine position, primarily used for antegrade nailing or shoulder surgery, not for posterior midshaft humerus plating.

Option D (Prone position) can be used for posterior plating but is less common than lateral decubitus due to anesthetic challenges and increased patient risks. While it offers direct posterior access, the claim of 'minimal risk to the brachial plexus' is not a unique advantage over lateral decubitus, and prone positioning has its own set of risks.

Option E (Semi-Fowler position) is similar to the beach chair and is used for shoulder procedures or antegrade nailing, not typically for posterior midshaft humerus plating.

Correct Answer: B

The case material emphasizes: "Radial Nerve Protection: This is the cardinal rule for midshaft humerus fracture surgery. Regardless of the approach, the radial nerve must be identified and protected." Under the 'Posterior Approach Henry Triceps Split' section, it states: "Deep Dissection & Internervous Plane: ...Crucially, identify the radial nerve. It typically lies within the spiral groove, deep to the lateral head of the triceps and medial to the lateral intermuscular septum. Trace the nerve proximally and distally, isolating it with vessel loops. Protect the profunda brachii artery accompanying the nerve. This step is critical and often performed first before further fracture exposure." Therefore, identifying the triceps interval and then the radial nerve is the most critical immediate next step.

Option A (Incise the deep fascia and immediately expose the fracture site) is incorrect because it bypasses the crucial step of radial nerve identification, significantly increasing the risk of iatrogenic injury.

Option C (Reflect the brachialis and biceps brachii muscles medially) describes a step in an anterolateral approach, not a posterior approach.

Option D (Perform a fasciotomy of the forearm) is not indicated unless there is clinical evidence of compartment syndrome, which is not mentioned in the vignette. It is not a routine step in midshaft humerus fracture fixation.

Option E (Apply a distractor to the fracture fragments) is a step in fracture reduction and fixation, which occurs after the nerve has been identified and protected, and the fracture site exposed. It is not the immediate next step after superficial dissection.

Correct Answer: C

The case material defines nonunion as "Failure of radiographic healing by 6-9 months post-fracture, often accompanied by pain or instability." This patient meets the criteria (8 months, pain, motion, no callus). The management section for nonunion states: "For established nonunions, revision surgery often involves combining mechanical stabilization (e.g., exchange nailing, conversion from plate to nail, or vice versa, dual plating) with biological augmentation (autogenous bone grafting). Addressing underlying risk factors (e.g., smoking cessation, nutritional optimization) is also crucial." Therefore, revision surgery with exchange nailing (a form of mechanical enhancement) and autogenous bone grafting (biological enhancement), along with addressing smoking and nutrition, is the most comprehensive and appropriate strategy.

Option A (Continue observation) is incorrect. At 8 months with no signs of healing and persistent pain/motion, it is an established nonunion, and further observation without intervention is unlikely to lead to union, especially with risk factors present.

Option B (Initiate bisphosphonates) is incorrect. Bisphosphonates are used for osteoporosis and to reduce fracture risk, not to stimulate healing of an established nonunion. They can even inhibit bone remodeling in some contexts.

Option D (Removal of the existing plate and application of a larger plate without bone grafting) is partially correct regarding mechanical enhancement but critically misses the biological component. For an established nonunion, especially with risk factors like smoking and poor nutrition, biological augmentation with bone grafting is almost always necessary to stimulate healing.

Option E (Aggressive physical therapy) is incorrect. Aggressive mobilization of an unstable nonunion will not promote healing and may exacerbate pain and instability. Activity should be restricted until definitive treatment for the nonunion is performed.

Correct Answer: C

The case material states under 'Immediate Post-Operative Phase': "Immobilization: Initially, a sling or shoulder immobilizer for comfort and protection, especially for the first 1-2 weeks. For highly stable fixation (e.g., well-locked plate, IM nail with good purchase), early gentle active-assisted and passive ROM can begin within days." It also specifies: "Weight-Bearing: No weight-bearing or lifting with the affected arm." This aligns perfectly with Option C.

Option A (Complete immobilization in a cast for 6 weeks) is incorrect. While immobilization is initially used, prolonged casting is generally avoided after stable operative fixation to prevent joint stiffness, especially in the humerus where early motion is encouraged.

Option B (Initiate immediate full active range of motion) is incorrect. While early motion is encouraged, 'full active ROM' immediately post-op is too aggressive and could jeopardize the healing fracture or fixation. It should be gentle and active-assisted/passive initially.

Option D (Aggressive isometric strengthening exercises) is incorrect. Isometric strengthening is introduced in the 'Early Healing and Strengthening Phase,' not immediately post-op. Aggressive exercises could disrupt the healing process.

Option E (Unrestricted active rotation) is incorrect. While early ROM is encouraged, 'unrestricted active rotation' is too aggressive, especially for the shoulder, and the case specifically advises: "Caution is advised with rotation, especially in early IM nailing where rotational stability may be limited." Even with plate fixation, unrestricted active rotation is not typically allowed immediately.

Correct Answer: B

The case material clearly lists "Open fractures: Require urgent debridement and stabilization to prevent infection" as an absolute indication for operative intervention. This patient has an open midshaft humerus fracture (Gustilo-Anderson Type II), which mandates immediate surgical management.

Option A (The patient's young age) is not an absolute indication for surgery. While it might influence the choice of fixation, it does not mandate surgery in itself.

Option C (The high-energy mechanism) often leads to more severe fractures, but it is not an absolute indication for surgery unless it results in specific complications (e.g., open fracture, vascular injury, severe comminution making non-op impossible).

Option D (The absence of neurovascular deficits) is a positive finding, but it does not, by itself, constitute an indication for surgery. In fact, for closed fractures, the absence of deficits often supports non-operative management.

Option E (The potential for a segmental fracture) is listed as a relative indication for surgery, not an absolute one. The definitive presence of an open fracture is a much stronger and absolute indication.

Correct Answer: C

The patient's presentation (laceration over an MCP joint after striking a mouth, pain with passive flexion, swelling, and tenderness) is highly suspicious for a 'fight bite' with potential septic arthritis of the MCP joint. Even in the absence of a visible foreign body or fracture on X-ray, the mechanism and clinical signs strongly suggest joint capsule penetration and deep infection. Emergent surgical irrigation and debridement with joint exploration is the standard of care for suspected septic arthritis or deep space infection from a human bite. This allows for thorough debridement of devitalized tissue, removal of any missed foreign bodies, and copious irrigation of the joint space. Intravenous broad-spectrum antibiotics should be initiated promptly. Oral antibiotics alone (A) are insufficient for deep infections. Discharging the patient (A, B) without definitive surgical management is dangerous and can lead to rapid joint destruction. While joint aspiration (D) can confirm septic arthritis, it should not delay definitive surgical management once clinically suspected. Primary closure of the wound (E) is contraindicated in contaminated human bite wounds due to the high risk of trapping infection.

Correct Answer: B

The patient's presentation is highly suggestive of septic arthritis of the MCP joint, a severe complication of a fight bite. Empiric intravenous antibiotics are crucial. Amoxicillin-clavulanate (Augmentin) is the first-line empiric antibiotic for human bite infections. It provides excellent broad-spectrum coverage against the characteristic polymicrobial flora of human bites, including common aerobes (Staphylococcus, Streptococcus) and anaerobes (Bacteroides, Fusobacterium, Peptostreptococcus), as well as the fastidious Gram-negative rod Eikenella corrodens. Ciprofloxacin and Rifampin (A) lack adequate anaerobic coverage. Doxycycline and Metronidazole (C) also have gaps in coverage for the typical fight bite pathogens. 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: C

Purulent material tracking along a tendon, especially into the wrist, is a classic sign of tenosynovitis, which is an infection of the tendon sheath. The extensor digitorum communis tendon is involved here. While other pathologies like septic arthritis (B) and osteomyelitis (D) can coexist or develop from tenosynovitis, the direct observation of pus within the tendon sheath extending proximally confirms tenosynovitis. Cellulitis (A) is a superficial soft tissue infection. A localized abscess (E) would be a circumscribed collection of pus, but its extension along a tendon sheath points specifically to tenosynovitis.

Correct Answer: D

For a suspected 'fight bite' over an MCP joint, the finger should be held in full flexion (the clenched fist position) 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 (A) or neutral (B) will obscure the primary injury tract and make it difficult to assess the joint capsule. Hyperextension (C) is anatomically incorrect for this purpose.

Correct Answer: B

The 'intrinsic plus' or 'safe position' splint is generally recommended for hand immobilization following injury or surgery, especially for infections, 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

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 and typically not present with bone changes. 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

Given the patient's history of penicillin allergy (anaphylaxis), beta-lactam antibiotics like Ampicillin-sulbactam (A) and Piperacillin-tazobactam (D) are contraindicated. Cefazolin (B) is a first-generation cephalosporin, which has some cross-reactivity risk with penicillin, and when combined with Metronidazole, lacks full Gram-negative coverage for organisms like Eikenella. Clindamycin provides good coverage against anaerobes and Gram-positives (Staph/Strep). Ciprofloxacin provides good coverage against Gram-negatives, including Eikenella corrodens. This combination (Clindamycin and Ciprofloxacin) is a suitable and commonly used alternative for a penicillin-allergic patient with a severe human bite infection. Vancomycin (E) would cover MRSA and Gram-positives, and Aztreonam covers Gram-negatives including Eikenella, but this combination is often reserved for resistant organisms or specific scenarios. Clindamycin and Ciprofloxacin is a common and effective alternative.

Correct Answer: B

In an acutely infected wound, primary repair of a partially or completely lacerated tendon is generally contraindicated due to the high risk of infection of the repair site, leading to tendon necrosis, rupture, and adhesion formation. The most appropriate management is thorough irrigation and debridement of the tendon ends and surrounding tissue, followed by leaving the tendon unrepaired. Definitive repair, if necessary, should be delayed until the infection is completely resolved and the wound is clean. Excising the tendon (C) would result in significant functional deficit. Covering with a flap (D) is premature and risky in an infected field. Corticosteroids (E) are contraindicated in active infection.

Correct Answer: C

While redness and warmth (A), elevated WBC count (B), and duration of symptoms (E) can be present in both cellulitis and deep infections, significant pain with passive range of motion (PROM) of the affected joint, especially if disproportionate to superficial findings, is the hallmark sign differentiating a deep-seated joint infection (septic arthritis) from isolated cellulitis. Cellulitis primarily involves the superficial soft tissues, while septic arthritis directly affects the joint capsule, making any movement excruciating due to stretching of the inflamed synovium. The size of the laceration (D) is not a reliable differentiator for depth of infection.

Correct Answer: C

A fracture of the fifth metacarpal neck associated with a fight bite means the fracture is an open fracture (communicating with the outside environment through the bite wound). This significantly complicates management. The bite wound requires meticulous debridement and copious irrigation, and the fracture must be treated as an open, contaminated injury. Definitive fracture stabilization (e.g., with internal hardware) is often delayed until the infection is controlled and the wound is clean, or performed with external fixation if immediate stability is required and internal fixation is deemed too risky in the acute infected setting. Primary closure of the bite wound (A) is contraindicated. Immediate definitive internal fixation (B) is dangerous in an infected field due to high risk of hardware infection. A fracture does not negate infection risk (D); in fact, it increases the risk of osteomyelitis. Ignoring the fracture (E) is malpractice.

Closed humeral shaft fractures presenting with a primary radial nerve palsy are managed initially with functional bracing and observation. Spontaneous nerve recovery occurs in the vast majority of cases, and immediate surgical exploration is not indicated.

A secondary radial nerve palsy that develops immediately following closed reduction of a humeral shaft fracture strongly suggests iatrogenic nerve entrapment within the fracture site. This is an absolute indication for immediate surgical exploration and internal fixation.

Acceptable alignment for nonoperative management of humeral shaft fractures includes up to 20 degrees of anterior angulation, 30 degrees of varus angulation, and 3 cm of shortening. The shoulder and elbow joints have a wide range of motion that easily compensates for this degree of malalignment without functional deficits.

The radial nerve pierces the lateral intermuscular septum approximately 10 cm proximal to the lateral epicondyle. At this level, it moves from the posterior compartment into the anterior compartment of the arm.

A secondary radial nerve palsy that develops after a closed reduction attempt of a humeral shaft fracture is an absolute indication for surgical exploration. This presentation is classic for a Holstein-Lewis fracture, where the radial nerve can become tethered or entrapped between the fracture fragments during reduction.

Kanavel's four cardinal signs of pyogenic flexor tenosynovitis include fusiform swelling, a flexed resting posture, tenderness along the tendon sheath, and pain with passive extension. Exquisite pain with passive extension is considered the earliest and most sensitive sign of the condition.

Acceptable alignment parameters for non-operative management of humeral shaft fractures include up to 30 degrees of varus/valgus angulation, 20 degrees of anterior/posterior angulation, and up to 3 cm of shortening. The extensive mobility of the shoulder and elbow joints compensates for these deformities without significant functional loss.

Kanavel's four cardinal signs are fusiform swelling, flexed resting posture, tenderness along the flexor sheath, and severe pain with passive extension. Erythema tracking up the forearm is a sign of lymphangitis, not a specific cardinal sign of flexor tenosynovitis.

In a Holstein-Lewis fracture, the radial nerve is particularly vulnerable to injury as it is tethered tightly while piercing the lateral intermuscular septum to pass from the posterior to the anterior compartment. This occurs approximately 10 cm proximal to the lateral epicondyle.

Human bites, or "fight bites," occurring over the MCP joint carry a high risk of deep space infection and septic arthritis. Eikenella corrodens is a fastidious Gram-negative rod uniquely associated with human oral flora, requiring treatment with amoxicillin-clavulanate or ampicillin-sulbactam.

The standard posterior approach to the humerus utilizes a muscle-splitting technique through the triceps brachii. Because all heads of the triceps are innervated by the radial nerve, there is no true internervous plane in this approach.

The patient has herpetic whitlow, an infection caused by the Herpes Simplex Virus (HSV) common in healthcare workers. Incision and drainage is strictly contraindicated as it can lead to secondary bacterial infection and failure to heal; treatment consists of antivirals, dry dressings, and observation.

Absolute indications for operative fixation of a humeral shaft fracture include an associated vascular injury requiring repair, a "floating elbow" (ipsilateral forearm fractures), bilateral humerus fractures, and compartment syndrome. Primary radial nerve palsy in a closed fracture is generally treated with observation.

Cat bites have a high rate of infection, most commonly caused by Pasteurella multocida. Amoxicillin-clavulanate (Augmentin) is the first-line oral antibiotic of choice as it effectively covers Pasteurella, as well as Staph and Strep species.

A primary radial nerve palsy associated with a closed humeral shaft fracture will spontaneously resolve in over 70% to 90% of cases. The standard of care is expectant management with fracture bracing and observation, delaying EMG testing until 3 to 6 weeks if no clinical recovery is observed.

Mycobacterium marinum is an atypical mycobacterium found in aquatic environments, classically presenting as a "fish tank granuloma" in aquarium workers or fishermen. It requires lower incubation temperatures (30°C) to grow in culture.

The most common and significant complication of antegrade intramedullary nailing of the humerus is shoulder pain and dysfunction, often due to violation of the rotator cuff (supraspinatus tendon) and prominent proximal hardware.

A volar longitudinal incision over the point of maximum fluctuance is currently the preferred approach for a felon, as it provides direct access to the septal compartments without jeopardizing digital nerves or causing tip necrosis. It must not cross the DIP flexion crease to prevent scar contracture.

Transverse fractures, particularly those in the proximal third of the humerus, have the highest risk of nonunion when treated non-operatively. This is due to a smaller cross-sectional area for healing, lack of interdigitation, and distracting forces from the arm's weight.

A collar button abscess is a web space infection that forms a dual compartment "dumbbell" shape. It spreads from the volar subfascial space to the dorsal subcutaneous space via the pathways around the natatory ligaments and superficial transverse metacarpal ligaments.

In cases of long bone fractures with critical vascular compromise, the preferred sequence is rapid restoration of perfusion with a temporary intravascular shunt, followed by stable skeletal fixation, and concluding with definitive vascular repair to prevent disruption of the vascular anastomosis during bone manipulation.

A horseshoe abscess occurs when purulence spreads between the radial bursa (which envelops the flexor pollicis longus of the thumb) and the ulnar bursa (which envelops the flexor tendons of the small finger) via their proximal communication in the space of Parona.

The radial nerve courses posteriorly along the spiral groove and predictably lies approximately 14 cm proximal to the lateral epicondyle and roughly 20 cm distal to the acromion before piercing the lateral intermuscular septum.

While acute paronychia is usually bacterial (S. aureus), chronic paronychia is classically associated with prolonged moisture exposure and fungal infection, most commonly Candida albicans. Treatment involves keeping hands dry, topical antifungals/steroids, or surgical marsupialization if refractory.

Historically, the arcuate branch of the anterior circumflex humeral artery was thought to provide the main blood supply. However, recent quantitative perfusion studies have definitively shown that the posterior circumflex humeral artery provides roughly 64% of the blood supply to the humeral head.

The deep spaces of the hand are separated by facial septa. The midpalmar space is separated from the thenar space radially by the midpalmar (or oblique) septum, which inserts firmly onto the fascia of the third metacarpal.

Acceptable alignment for midshaft humerus fractures treated non-operatively is up to 30 degrees of varus angulation, 20 degrees of anterior angulation, and 3 cm of shortening. The large compensatory range of motion of the shoulder and elbow allows for excellent functional outcomes despite these deformities.

A closed humerus fracture with a primary radial nerve palsy should initially be observed, as the majority of these palsies are neuropraxias that will spontaneously recover. Routine immediate surgical exploration is not indicated unless the fracture requires operative fixation for other reasons.

Acute suppurative flexor tenosynovitis is traditionally managed with antibiotics and closed sheath irrigation. The standard technique utilizes a proximal incision at the A1 pulley and a distal incision at the A5 pulley to flush the flexor sheath with saline.

"Fight bites" over the MCP joint carry a high risk of septic arthritis and are classic for human oral flora, prominently Eikenella corrodens. Amoxicillin-clavulanate provides appropriate broad-spectrum empiric coverage for this organism alongside Staph and Strep.

Pasteurella multocida is the most common pathogen associated with cat and dog bites, classically presenting with an intense, rapid-onset cellulitis often within 12 to 24 hours of the injury. Treatment requires beta-lactamase inhibitors or other broad-spectrum coverage.

Absolute indications for ORIF of a midshaft humerus fracture include open fractures, vascular injury requiring repair, compartment syndrome, floating elbow, and bilateral humerus fractures. Primary radial nerve palsy is considered a relative, not absolute, indication.

A volar longitudinal incision over the site of maximum fluctuance is generally preferred for a felon, as it avoids crossing the flexion creases and minimizes damage to the digital nerves. "Fish-mouth" incisions are historically discouraged due to high risks of painful scarring and neurovascular injury.