Trauma, Infection & Shoulder Orthopedic MCQs - Part 59

Question 1

A 68-year-old female with severe rotator cuff tear arthropathy undergoes a reverse total shoulder arthroplasty (RTSA). To minimize the risk of inferior scapular notching postoperatively, how should the glenosphere ideally be positioned during the procedure?

Explanation

Scapular notching is a well-known complication of reverse total shoulder arthroplasty (RTSA) occurring when the humeral component abuts the inferior scapular neck during adduction. Biomechanical and clinical studies have shown that placing the glenosphere with inferior translation (overhanging the inferior glenoid rim by 2-4 mm) and a slight inferior tilt significantly reduces the incidence of impingement and subsequent scapular notching.

Question 2

A 35-year-old male is brought to the trauma bay after a motorcycle collision. He is hemodynamically unstable with a blood pressure of 80/50 mmHg and a heart rate of 130 bpm. A FAST exam is negative. An anteroposterior pelvic radiograph reveals an anteroposterior compression Type III (APC-III) pelvic ring injury, and a pelvic binder is immediately placed. What is the most common anatomic source of major hemorrhage in this specific injury pattern?

Explanation

In pelvic ring injuries, particularly those involving disruption of the posterior elements (like APC-III and vertical shear patterns), the most common source of major hemorrhage is venous bleeding, accounting for up to 80% of cases. The presacral venous plexus and prevesical venous plexus are the primary venous sources. Arterial bleeding (e.g., superior gluteal, internal pudendal) accounts for approximately 10-20% of cases, with the superior gluteal artery being the most commonly injured artery, especially in lateral compression or sheer injuries.

Question 3

You are evaluating a 70-year-old male for a suspected periprosthetic joint infection (PJI) 3 years after a total knee arthroplasty. A synovial fluid sample is sent for alpha-defensin testing. What is the biological origin and function of alpha-defensin in the context of a joint infection?

Explanation

Alpha-defensin is a highly specific antimicrobial peptide naturally released by activated human neutrophils in the presence of pathogens. It integrates into and destroys bacterial cell membranes. Its presence in synovial fluid is a highly accurate biomarker for periprosthetic joint infection, as it distinguishes between aseptic inflammation and true bacterial infection.

Question 4

According to the Hertel radiographic criteria for evaluating proximal humerus fractures, which of the following fracture characteristics is considered the most reliable predictor of subsequent avascular necrosis (AVN) of the humeral head?

Explanation

Hertel et al. described key radiographic predictors for ischemia of the humeral head in proximal humerus fractures. The most significant predictors for AVN are: an attached posteromedial calcar length of less than 8 mm, disruption of the medial hinge greater than 2 mm, and a basicervical fracture pattern. A medial hinge disruption >2 mm disrupts the ascending branches of the anterior humeral circumflex artery and capsular vessels, critically depriving the head of its blood supply.

Question 5

A 25-year-old female sustains a closed Hawkins Type III fracture of the talar neck after a fall from a height. She undergoes prompt open reduction and internal fixation. What is the approximate expected rate of avascular necrosis (AVN) of the talar body for this specific fracture pattern?

Explanation

The Hawkins classification for talar neck fractures is highly prognostic for avascular necrosis (AVN). Type I (undisplaced) has an AVN rate of 0-15%. Type II (subluxation or dislocation of the subtalar joint) has a rate of 20-50%. Type III (dislocation of both subtalar and tibiotalar joints) has an extremely high AVN rate, traditionally reported between 80-100%. Type IV (Type III plus talonavicular subluxation/dislocation) also carries a near 100% risk.

Question 6

A 45-year-old poorly controlled diabetic male presents with a draining sinus over his left anterior tibia. Radiographs demonstrate an infected tibial nonunion with diffuse mechanical instability, though the fibula is intact. According to the Cierny-Mader classification of osteomyelitis, how is this infection staged?

Explanation

The Cierny-Mader classification uses anatomic stage (1: medullary, 2: superficial, 3: localized, 4: diffuse) and host physiologic status (A: normal, B: compromised locally or systemically, C: treatment worse than disease). An infected nonunion or mechanically unstable segment represents a diffuse lesion (Stage 4). Because the patient is a poorly controlled diabetic, he is a systemically compromised host (B-host). Therefore, the correct classification is Stage 4B.

Question 7

In the decision-making process for anterior shoulder instability surgery, glenoid bone loss is a critical factor. At what approximate threshold of anterior glenoid bone loss is an isolated arthroscopic Bankart repair generally considered to have an unacceptably high failure rate, thereby mandating a bony augmentation procedure (e.g., Latarjet)?

Explanation

Traditional biomechanical and clinical studies have established a 'critical' glenoid bone loss threshold of 20% to 25%. Defects larger than this alter the glenohumeral kinematics and contact pressures significantly, resulting in a high failure rate for soft-tissue isolated repairs (Bankart). In these cases, a bony augmentation procedure, such as a Latarjet (coracoid transfer) or iliac crest bone graft, is mandated. (Note: recent literature debates 'subcritical' bone loss around 13.5%, but 20-25% remains the classic absolute indication for bony augmentation).

Question 8

A 28-year-old male polytrauma patient sustains bilateral femoral shaft fractures and severe pulmonary contusions. The surgical team is debating between Early Total Care (ETC) with intramedullary nailing and Damage Control Orthopedics (DCO) with temporary external fixation. According to accepted DCO criteria, which of the following is considered an absolute indication for proceeding with DCO rather than ETC?

Explanation

Pape and Giannoudis established clinical parameters for managing polytrauma. Criteria for an 'unstable' patient mandating Damage Control Orthopedics (DCO) rather than Early Total Care (ETC) include: Arterial pH < 7.24, core temperature < 32°C, base deficit > 6-8 mmol/L, coagulopathy, and transfusion requirements of multiple units of packed RBCs. A pH < 7.24 represents severe acidosis, putting the patient at extreme risk for the 'lethal triad' if a lengthy IM nailing is performed.

Question 9

The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is used to distinguish necrotizing fasciitis from other severe soft tissue infections. Which of the following laboratory parameters awards the highest maximum possible points within the LRINEC scoring system?

Explanation

In the LRINEC score, C-reactive protein (CRP) ≥ 150 mg/L awards the most points (4 points). The other variables award a maximum of 2 points each (WBC > 25 = 2 points; Hemoglobin < 11 = 2 points; Sodium < 135 = 2 points; Creatinine > 1.6 = 2 points). A total score ≥ 6 is suspicious for necrotizing fasciitis.

Question 10

A 42-year-old male presents with sudden onset of severe, unrelenting right shoulder pain lasting for two weeks, which has now begun to resolve. However, he now notices profound weakness in active external rotation and abduction. Examination demonstrates noticeable atrophy of the supraspinatus and infraspinatus. An MRI of the shoulder is negative for a rotator cuff tear. EMG reveals acute denervation potentials in the affected muscles. What is the most likely diagnosis?

Explanation

Parsonage-Turner syndrome (neuralgic amyotrophy) classically presents with an acute onset of severe shoulder girdle pain that lasts for 1 to 3 weeks. As the pain subsides, marked weakness and rapid muscle atrophy (typically involving the suprascapular, long thoracic, or axillary nerves) develop. The exact etiology is unknown but is thought to be an immune-mediated or viral neuritis. MRI rules out mechanical tears, and EMG confirms denervation.

Question 11

A 34-year-old male falls from a roof and sustains an isolated, extra-articular fracture of the scapular body and neck. Operative fixation is being considered. Based on the established indications for operative management of extra-articular scapular neck fractures, which of the following is a recognized indication for open reduction and internal fixation?

Explanation

Operative indications for extra-articular scapular neck fractures are based on severe displacement that severely alters glenohumeral mechanics. Accepted absolute or strong relative indications include: Medial/lateral translation > 20 mm, angular deformity > 45 degrees, and a glenopolar angle (GPA) ≤ 22 degrees. A normal GPA is roughly 30-45 degrees; a decreased angle (<22 degrees) signifies severe rotational malalignment of the glenoid fragment, predisposing to poor functional outcomes.

Question 12

A 4-year-old boy is evaluated in the emergency department for an acute limp and refusal to bear weight on his right leg. His temperature is 38.6°C (101.5°F). Laboratory studies reveal a WBC count of 10,500/mm3 and an ESR of 45 mm/hr. According to the original Kocher criteria for differentiating pediatric septic arthritis of the hip from transient synovitis, what is the approximate probability that this child has septic arthritis?

Explanation

The original Kocher criteria consist of four predictors for septic arthritis: 1) Non-weight-bearing, 2) Temperature > 38.5°C, 3) ESR > 40 mm/hr, and 4) WBC > 12,000/mm3. This patient meets exactly three criteria: Non-weight-bearing, Temperature > 38.5°C, and ESR > 40 mm/hr (his WBC is < 12,000). According to the Kocher study, the predicted probability of septic arthritis is 3% for 1 criterion, 40% for 2 criteria, 93% for 3 criteria, and 99% for 4 criteria.

Question 13

A 65-year-old female has a massive, irreparable posterosuperior rotator cuff tear and poor forward elevation. A latissimus dorsi tendon transfer is proposed. Which of the following physical examination findings is considered a strong contraindication or predictor of poor outcome for an isolated latissimus dorsi transfer?

Explanation

A successful latissimus dorsi tendon transfer for an irreparable posterosuperior rotator cuff tear relies on the presence of an intact subscapularis to maintain the anterior-posterior force couple of the shoulder. A positive lift-off test indicates subscapularis insufficiency, which is a recognized absolute or strong relative contraindication to latissimus dorsi transfer. Doing the transfer in the face of an incompetent subscapularis results in unconstrained superior escape and poor functional outcomes.

Question 14

A 45-year-old male sustains a volar marginal articular fracture of the distal radius (volar Barton's fracture) with volar subluxation of the carpus. During open reduction and internal fixation via an FCR approach, which of the following stout ligamentous structures remains attached to the volar fracture fragment, exerting the primary proximal and volar displacing force on the carpus?

Explanation

In a volar Barton's fracture (volar shear fracture of the distal radius), the strong volar radiocarpal ligaments—specifically the radioscaphocapitate (RSC) and the long/short radiolunate ligaments—remain attached to the avulsed volar bony fragment. Because the carpus is tethered to this fragment via these ligaments, the entire carpus subluxates volarly and proximally along with the fracture fragment.

Question 15

Based on the recommendations of the International Consensus Meeting (ICM) on Musculoskeletal Infection, which of the following is considered an absolute contraindication to a single-stage (one-stage) exchange arthroplasty for a periprosthetic joint infection?

Explanation

A single-stage exchange requires specific conditions for success, primarily the ability to deliver targeted, effective local and systemic antibiotics. An absolute contraindication to single-stage exchange is an unknown infecting organism preoperatively, because the surgeon cannot appropriately mix targeted antibiotics into the bone cement. Other contraindications include systemic sepsis, severe soft tissue compromise, and highly virulent organisms without available oral antibiotic suppression.

Question 16

During a routine diagnostic shoulder arthroscopy, you identify a cord-like middle glenohumeral ligament (MGHL) that inserts directly into the superior labrum at the base of the biceps anchor, and you note an absent anterosuperior labrum from the 1 o'clock to 3 o'clock position. This anatomic variant is known as a Buford complex. What is the most appropriate surgical management for this specific structural finding?

Explanation

The Buford complex is a normal anatomic variant present in about 1.5% to 2% of shoulders. It is characterized by a cord-like MGHL attaching directly to the superior labrum, along with an absent anterosuperior labrum. It is critical to recognize this as a normal variant. Surgical repair (attaching the cord-like MGHL to the anterosuperior glenoid) is contraindicated as it will severely restrict external rotation and cause iatrogenic stiffness. No surgical intervention should be directed at the Buford complex itself.

Question 17

A 30-year-old male develops acute compartment syndrome of the leg following a closed tibial shaft fracture. He undergoes a standard 4-compartment fasciotomy via a two-incision technique. When making the lateral incision to decompress the anterior and lateral compartments, extending the proximal aspect of the incision too close to the fibular head places which of the following structures at greatest risk of iatrogenic injury?

Explanation

The lateral incision in a two-incision leg fasciotomy is used to decompress the anterior and lateral compartments. The incision should stay at least 5 cm distal to the fibular head to avoid iatrogenic injury to the common peroneal nerve, which wraps around the fibular neck before dividing into the deep and superficial peroneal nerves.

Question 18

A 40-year-old male with a 6-cm infected diaphyseal defect of the tibia is treated with debridement, placement of an antibiotic cement spacer, and external fixation (the first stage of the Masquelet technique). According to histologic studies, at what time point does the induced membrane exhibit the peak expression of osteoinductive factors (such as VEGF, TGF-beta1, and BMP-2), making it the optimal biologic window for the second stage (bone grafting)?

Explanation

Histologic and biological studies of the Masquelet induced membrane technique (e.g., Pelissier et al.) demonstrate that the induced membrane is highly vascular and secretes key osteogenic and angiogenic growth factors (VEGF, TGF-β1, BMP-2). The expression of these factors peaks between 2 and 4 weeks after spacer placement, and steadily declines after 6 weeks. Therefore, the optimal biological window for the second stage (cancellous bone grafting) is typically around 4 weeks.

Question 19

A 24-year-old male cyclist falls onto his left shoulder and sustains a closed midshaft clavicle fracture. Which of the following initial radiographic displacement patterns has been shown in large prospective randomized trials to carry the highest risk of nonunion if treated nonoperatively?

Explanation

Prospective trials (such as those by the Canadian Orthopaedic Trauma Society - COTS) have identified predictors of nonunion for midshaft clavicle fractures. The most significant predictors for nonunion in nonoperatively treated clavicle fractures are complete displacement (lack of cortical contact), severe comminution (Z-type), and initial shortening of greater than 1.5 to 2.0 cm. Z-type comminution with > 2 cm shortening carries an exceptionally high nonunion risk if treated conservatively.

Question 20

A 40-year-old male presents with a severe crush injury to the right lower extremity after a high-speed motor vehicle collision. The team calculates a Mangled Extremity Severity Score (MESS) to aid in the decision between limb salvage and primary amputation. Which of the following variables is NOT a component used to calculate the MESS?

Explanation

The Mangled Extremity Severity Score (MESS) is a well-known scoring system designed to help predict the need for amputation. It utilizes four components: 1) Skeletal and soft-tissue injury (1-4 points), 2) Limb ischemia (1-3 points, doubled if >6 hours), 3) Shock (0-2 points), and 4) Patient age (0-2 points). A score ≥ 7 is highly predictive of amputation. Neurologic deficit (e.g., absent plantar sensation) is notably NOT a component of the MESS, though it was controversially used in other older decision-making algorithms.

Question 21

A 22-year-old overhead athlete presents with recurrent anterior shoulder instability. Magnetic resonance arthrography demonstrates that the anterior labroligamentous complex is avulsed from the glenoid rim and displaced medially and inferiorly along the glenoid neck. The anterior scapular periosteum remains intact but is stripped from the bone. Which of the following eponymous lesions is described?

Explanation

The scenario describes an ALPSA (Anterior Labroligamentous Periosteal Sleeve Avulsion) lesion. Unlike a classic Bankart lesion where the periosteum is torn, in an ALPSA lesion the periosteum is intact but stripped, allowing the avulsed labrum to displace medially and inferiorly on the glenoid neck. A Perthes lesion also has an intact periosteum, but the labrum is not medially displaced.

Question 22

A 35-year-old male sustains an anteroposterior compression (APC III) pelvic ring injury in a motorcycle collision. He arrives in hemorrhagic shock. What is the most common anatomical source of massive retroperitoneal hemorrhage in this specific injury pattern?

Explanation

While arterial bleeding (e.g., from the internal pudendal or obturator arteries in APC patterns, or superior gluteal in lateral compression patterns) can be severe and life-threatening, approximately 80-90% of all major pelvic hemorrhage arises from the low-pressure, high-volume presacral venous plexus and exposed cancellous bone surfaces at fracture sites.

Question 23

According to the 2018 International Consensus Meeting (ICM) criteria for Periprosthetic Joint Infection (PJI), which of the following is considered a 'major' criterion that, if present, definitively establishes the diagnosis of PJI?

Explanation

The 2018 ICM criteria establish two 'major' criteria for definitive PJI diagnosis: 1) a sinus tract communicating directly with the joint space/prosthesis, or 2) two positive periprosthetic cultures yielding phenotypically identical organisms. The other listed options are considered 'minor' criteria or biomarkers used in the scoring algorithm.

Question 24

A 68-year-old female presents with severe right shoulder pain, an inability to actively forward elevate her arm past 45 degrees, and a positive hornblower's sign. Radiographs show no significant glenohumeral osteoarthritis but a highly superiorly migrated humeral head. MRI reveals a massive, retracted, and fatty-infiltrated tear of the supraspinatus and infraspinatus. Her deltoid function is completely intact. What is the most appropriate surgical intervention?

Explanation

The patient has a massive, irreparable rotator cuff tear with pseudoparalysis (inability to actively elevate the arm above 90 degrees) but an intact deltoid. Reverse total shoulder arthroplasty (rTSA) is the definitive treatment of choice in this setting, as it alters the biomechanical center of rotation to allow the intact deltoid to effectively elevate the arm. Tendon transfers and superior capsular reconstructions are not reliable in the presence of true pseudoparalysis.

Question 25

A 28-year-old male sustains a high-energy distal femur fracture. CT scanning reveals a coronal plane fracture of the lateral femoral condyle. When using independent lag screw fixation for this specific fragment, which of the following screw orientations is considered the most biomechanically sound?

Explanation

The injury described is a Hoffa fracture (coronal shear fracture of the femoral condyle). Biomechanical studies demonstrate that posterior-to-anterior directed lag screws are significantly stronger than anterior-to-posterior screws. This is because the screw threads engage the thicker, denser cortical bone of the anterior femur, providing better compression and resistance to shear forces.

Question 26

A 6-year-old boy with homozygous sickle cell disease develops acute diaphyseal osteomyelitis. While Staphylococcus aureus remains the most common overall cause of osteomyelitis in this patient population, which of the following organisms is uniquely characteristic and disproportionately prevalent due to the underlying pathophysiology of his disease?

Explanation

Patients with sickle cell disease are uniquely susceptible to Salmonella osteomyelitis due to intermittent bowel ischemia leading to bacteremia, coupled with autosplenectomy impairing the clearance of encapsulated organisms. Though S. aureus is still extremely common, Salmonella is the classic, uniquely associated pathogen in this population.

Question 27

A 32-year-old elite volleyball player presents with insidious onset of vague posterolateral shoulder pain. Physical examination reveals isolated atrophy and weakness of the infraspinatus muscle. Supraspinatus strength and bulk are completely normal. MRI is expected to reveal a paralabral cyst causing nerve compression at which anatomical location?

Explanation

Isolated atrophy and weakness of the infraspinatus indicate compression of the suprascapular nerve distal to the innervation of the supraspinatus. This occurs at the spinoglenoid notch, often due to a paralabral cyst originating from a posterior labral tear. Compression at the suprascapular notch would affect both the supraspinatus and infraspinatus.

Question 28

A 45-year-old man falls from a 12-foot ladder and sustains an isolated extra-articular scapular body and neck fracture. According to established treatment guidelines (e.g., Ada and Miller / OTA), which of the following radiographic parameters is an absolute indication for open reduction and internal fixation?

Explanation

The vast majority of extra-articular scapula fractures are treated non-operatively. Operative indications include: scapular neck angulation >40 degrees, medial/lateral translation >20 mm, and a glenopolar angle <22 degrees (normal is 30-45 degrees). Therefore, a neck fracture with 45 degrees of angulation is an indication for surgery.

Question 29

A 55-year-old diabetic male presents with an erythematous, exquisitely tender, and swollen right lower extremity. In utilizing the LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score to stratify his risk, which of the following laboratory values contributes to a higher score?

Explanation

The LRINEC score incorporates six laboratory parameters: C-reactive protein (CRP), total white blood cell count (points given for >15,000), hemoglobin (points for <13.5), serum sodium (2 points for <135 mmol/L), serum creatinine (points for >1.41 mg/dL), and fasting glucose (points for >180 mg/dL). Lactate, potassium, and procalcitonin are not part of the LRINEC score.

Question 30

During an open reduction and internal fixation of a severe proximal humerus fracture, the surgeon carefully preserves the soft tissue attachments to the tuberosities to maintain perfusion. Recent quantitative anatomical studies have demonstrated that the primary arterial blood supply to the humeral head is provided by which vessel?

Explanation

Historically, the arcuate branch of the anterior humeral circumflex artery was believed to be the primary blood supply to the humeral head. However, modern quantitative studies (e.g., Hettrich et al.) have proven that the posterior humeral circumflex artery actually supplies the vast majority (approximately 64%) of the blood to the humeral head.

Question 31

A 24-year-old male sustains a closed comminuted tibial shaft fracture. Three hours after admission, he complains of excruciating pain that is out of proportion to the injury. Which of the following is recognized as the earliest and most sensitive clinical sign of acute compartment syndrome?

Explanation

Pain out of proportion to the injury and pain elicited by passive stretch of the muscles traversing the affected compartment are the earliest and most sensitive clinical findings in acute compartment syndrome. Loss of pulses, pallor, and paralysis are late signs, often indicating that irreversible ischemic necrosis has already occurred.

Question 32

A 3-year-old girl is evaluated in the emergency department for a limp and refusal to bear weight on her right leg. Her temperature is 38.0°C (100.4°F). Laboratory testing reveals an Erythrocyte Sedimentation Rate (ESR) of 50 mm/hr and a White Blood Cell (WBC) count of 13,000/mm3. According to the Kocher criteria, what is her approximate probability of having septic arthritis of the hip?

Explanation

The Kocher criteria for pediatric septic hip are: non-weight-bearing, temperature >38.5°C, ESR >40 mm/hr, and WBC >12,000/mm3. This patient meets three criteria (non-weight-bearing, ESR >40, WBC >12,000; she fails the temperature criterion at 38.0°C). The probabilities of septic arthritis are approximately 3% for 1 criterion, 40% for 2, 93% for 3, and 99% for 4 criteria.

Question 33

A 25-year-old mountain biker falls directly onto his shoulder point. Radiographs show a significantly displaced distal clavicle. The injury is classified as a Rockwood Type III acromioclavicular (AC) joint dislocation. Which of the following describes the status of the stabilizing soft tissues in this specific injury grade?

Explanation

In a Rockwood Type III injury, both the acromioclavicular (AC) and coracoclavicular (CC) ligaments are completely torn, leading to superior displacement of the clavicle by 25-100% compared to the normal side. The deltotrapezial fascia remains intact. If the deltotrapezial fascia is disrupted, allowing severe subcutaneous displacement, it is classified as a Type V injury.

Question 34

In a patient presenting with a purely ligamentous Lisfranc injury (disruption of the tarsometatarsal joint complex without associated metatarsal base fractures), which of the following is the most appropriate, evidence-based surgical treatment to optimize functional outcomes and minimize the need for hardware removal?

Explanation

Multiple prospective randomized studies (e.g., Ly and Coetzee, 2006) have demonstrated that primary arthrodesis of the medial column (1st, 2nd, and 3rd TMT joints) yields superior functional outcomes, a lower rate of hardware failure, and fewer subsequent surgeries compared to ORIF in purely ligamentous Lisfranc injuries. ORIF remains standard for bony Lisfranc fracture-dislocations.

Question 35

A 45-year-old agricultural worker from the San Joaquin Valley develops chronic osteomyelitis of the lumbar spine following a severe respiratory illness. Histopathologic examination of a vertebral biopsy reveals large, thick-walled spherules containing numerous endospores. What is the most appropriate systemic pharmacological therapy for this bone infection?

Explanation

The clinical history (San Joaquin Valley) and histology ('spherules containing endospores') are pathognomonic for Coccidioidomycosis. Disseminated extrapulmonary disease, such as Coccidioidal osteomyelitis, is classically treated with prolonged antifungal therapy utilizing azoles (Itraconazole or Fluconazole) or, in severe/refractory cases, intravenous Amphotericin B.

Question 36

A 19-year-old rugby player sustains a posteriorly displaced sternoclavicular (SC) joint dislocation. He is hemodynamically stable but complains of dysphagia and voice changes. A closed reduction in the operating room with a cardiothoracic surgeon on standby is attempted but fails. What is the next most appropriate step in management?

Explanation

Posterior SC dislocations that fail closed reduction or cause ongoing compression of mediastinal structures (trachea, esophagus, great vessels) require open reduction. The gold standard for surgical stabilization is reconstruction using a figure-of-eight tendon graft (e.g., semitendinosus or palmaris). Kirschner wires and pins are strictly contraindicated due to the high risk of fatal hardware migration into the heart or great vessels.

Question 37

A 33-year-old male sustains a high-energy injury to his foot and ankle. Radiographs and CT demonstrate a Hawkins Type III talar neck fracture. Based on the vascular anatomy of the talus, what is the approximate published risk of developing avascular necrosis (AVN) of the talar body?

Explanation

A Hawkins Type III fracture is defined as a talar neck fracture with dislocation of both the subtalar and tibiotalar (ankle) joints. This severe injury disrupts all three primary blood supplies to the talar body (artery of the tarsal canal, deltoid branches, and dorsal supply from the anterior tibial artery). The risk of AVN is exceptionally high, classically cited between 70% and 100%.

Question 38

A 30-year-old male presents with a deep, purulent laceration over the third metacarpophalangeal joint after striking another individual in the mouth ('fight bite'). Which fastidious gram-negative rod is characteristically associated with human bite wounds and must be covered by the chosen empiric antibiotic regimen?

Explanation

Eikenella corrodens is a fastidious gram-negative facultative anaerobe that is part of normal human oral flora. It is a classic pathogen in clenched-fist injuries (fight bites) and human bite wounds. Empiric therapy typically involves amoxicillin-clavulanate. Pasteurella and Capnocytophaga are seen in dog/cat bites, Bartonella in cat scratch disease, and M. marinum in aquatic exposures.

Question 39

A 60-year-old man undergoes an anatomic total shoulder arthroplasty via a standard deltopectoral approach. The subscapularis tendon is detached from the lesser tuberosity for exposure and subsequently repaired. At his 3-month postoperative visit, he complains of anterior shoulder pain and weakness. Which physical examination finding would most specifically indicate a structural failure of his subscapularis repair?

Explanation

The subscapularis functions as an internal rotator and a crucial anterior restraint of the glenohumeral joint. If the subscapularis repair fails after total shoulder arthroplasty, the patient will exhibit clinical signs of weakness in internal rotation (e.g., positive lift-off, bear-hug, or belly-press tests) and a distinct increase in passive external rotation due to the loss of the anterior soft tissue tether.

Question 40

A 45-year-old male sustains a highly comminuted, high-energy tibial pilon fracture (OTA/AO 43-C3). The soft tissues are severely swollen with extensive fracture blisters. The surgeon places a spanning external fixator across the ankle joint. According to the standard two-stage treatment protocol (Sirkin and Sanders), when is the optimal time to proceed with definitive open reduction and internal fixation of the tibial plafond?

Explanation

The standard two-stage protocol for severe pilon fractures with compromised soft tissues involves immediate application of a joint-spanning external fixator. Definitive ORIF is delayed until the soft tissues have adequately recovered, which is indicated clinically by the resolution of edema (appearance of the 'wrinkle sign') and epithelialization of fracture blisters. This typically occurs between 10 to 21 days post-injury.

Question 41

A 42-year-old male sustains a closed transverse acetabular fracture with an associated large Morel-Lavallée lesion over the lateral hip. He requires operative fixation via a Kocher-Langenbeck approach. What is the most appropriate management of the soft tissue lesion to minimize infection risk?

Explanation

A Morel-Lavallée lesion is a closed internal degloving injury where subcutaneous tissue is separated from the underlying fascia, filling with blood and necrotic fat. If an operative approach must traverse the lesion, open debridement, excision of the necrotic fat and pseudocapsule, and copious irrigation are required to decrease the very high risk of deep postoperative infection. Aspiration alone is insufficient due to retained necrotic debris.

Question 42

In the management of a staphylococcal periprosthetic joint infection treated with debridement, antibiotics, and implant retention (DAIR), rifampin is often added to the postoperative antibiotic regimen. What is the primary mechanism of action of rifampin that makes it uniquely effective against biofilm-associated staphylococci?

Explanation

Rifampin exerts its bactericidal effect by binding to the beta subunit of DNA-dependent RNA polymerase, thereby inhibiting bacterial RNA synthesis. It is highly lipophilic, penetrates biofilms well, and is active against stationary-phase staphylococci, making it a critical adjunct in DAIR procedures for staphylococcal PJIs. To prevent resistance, it must never be used as monotherapy.

Question 43

A 68-year-old female sustains a proximal humerus fracture. According to classic anatomic studies by Hertel et al., which combination of radiographic findings is the most reliable predictor of humeral head ischemia?

Explanation

Hertel et al. described predictors of humeral head ischemia after proximal humerus fractures. The most reliable predictors of AVN are a lack of metaphyseal head extension (calcar length less than 8 mm), disruption of the medial hinge, and a basicervical (anatomic neck) fracture pattern. When all three are present, the positive predictive value for ischemia is 97%.

Question 44

A 28-year-old male sustains a high-energy dorsiflexion injury to his right foot. Radiographs demonstrate a talar neck fracture with dislocation of both the subtalar and tibiotalar joints, while the talonavicular joint remains intact. What is his Hawkins classification and approximate risk of avascular necrosis (AVN)?

Explanation

A Hawkins III talar neck fracture involves dislocation of the body of the talus from both the subtalar and tibiotalar joints, while the talonavicular joint remains intact. The risk of AVN in Hawkins III fractures is classically reported as high as 80-100% due to disruption of all three major blood supplies (artery of the tarsal canal, artery of the sinus tarsi, and deltoid branches). Hawkins IV includes talonavicular subluxation/dislocation.

Question 45

An obese 55-year-old male with poorly controlled diabetes presents with extreme leg pain, swelling, and erythema. You calculate a Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score. Which of the following laboratory parameters is NOT a component of the LRINEC score?

Explanation

The LRINEC score helps stratify the risk of necrotizing fasciitis. Its components include CRP (≥150 mg/L), WBC count (>15, >25), Hemoglobin (<13.5, <11), Serum sodium (<135 mmol/L), Serum creatinine (>1.41 mg/dL), and Serum glucose (>180 mg/dL). Serum potassium is not a component of the LRINEC score.

Question 46

A 22-year-old male motorcyclist is brought to the trauma bay after a high-speed collision. Chest radiograph shows lateral displacement of the left scapula with an intact clavicle but widely separated acromioclavicular and sternoclavicular joints. What is the most critical immediate step in evaluating this patient?

Explanation

The patient has a scapulothoracic dissociation, characterized by lateral displacement of the scapula and massive soft tissue injury. This represents a closed forequarter amputation. The most critical immediate concern is vascular injury (subclavian or axillary artery), which occurs in up to 80% of cases and can be rapidly fatal. CT angiography is the most critical immediate step.

Question 47

In the development of acute compartment syndrome following a tibial shaft fracture, what is the initial microvascular event that triggers the cascade leading to muscle necrosis?

Explanation

The pathophysiology of acute compartment syndrome begins with an increase in intracompartmental pressure that surpasses local venous pressure. This leads to venous outflow obstruction, which causes a further increase in intracompartmental pressure, eventually collapsing the capillary bed. This eliminates the local tissue perfusion gradient, leading to ischemia. Arterial inflow is maintained until very late in the process.

Question 48

A 45-year-old female presents with a draining sinus tract from her right distal femur, secondary to a fracture treated with ORIF 5 years ago. She has no medical comorbidities but smokes 1 pack of cigarettes a day. According to the Cierny-Mader classification of osteomyelitis, what is her physiological host status?

Explanation

The Cierny-Mader classification categorizes the host physiology into A (normal host), B (compromised host), and C (treatment worse than disease). Smoking is strictly considered a systemic compromising factor (Bs). Local factors (Bl) include poor tissue perfusion, venous stasis, major vessel compromise, or radiation. Therefore, a smoker with no other local factors is a Bs-host (B-host, systemic compromise).

Question 49

In a reverse total shoulder arthroplasty (RTSA), medialization and distalization of the center of rotation achieves which of the following biomechanical advantages?

Explanation

In RTSA, medializing and distalizing the center of rotation lengthens the deltoid, increasing its resting tension and moment arm. This biomechanical shift recruits the anterior and posterior portions of the deltoid to act as forward elevators and abductors, compensating for the absent rotator cuff. Medialization also beneficially decreases the torque/shear forces at the baseplate-glenoid interface.

Question 50

A 25-year-old male sustains a vertically oriented (Pauwels Type III) femoral neck fracture. He undergoes closed reduction and internal fixation with three parallel cancellous screws. Which of the following biomechanical forces is the primary driver of failure (varus collapse and nonunion) in this specific fracture pattern?

Explanation

Pauwels Type III femoral neck fractures are highly vertical (fracture angle >50 degrees from the horizontal). This vertical orientation converts vertical weight-bearing compressive forces into high shear forces across the fracture site. This predisposes the construct to varus collapse, loss of fixation, and nonunion when treated with simple parallel cancellous screws.

Question 51

A 4-year-old boy presents with right hip pain, a limp, and refusal to bear weight. Which inflammatory marker has been shown in subsequent validation studies (e.g., Caird et al.) to be the single best independent predictor of pediatric septic arthritis when combined with the classic Kocher criteria?

Explanation

While the classic Kocher criteria utilized ESR, WBC, inability to bear weight, and fever, subsequent studies (Caird et al.) demonstrated that a CRP > 2.0 mg/dL is an excellent independent predictor. When added as a fifth variable to the original criteria, it significantly increases the diagnostic accuracy for pediatric septic arthritis.

Question 52

A 28-year-old professional volleyball player presents with insidious onset of vague posterior shoulder pain and weakness in external rotation. Examination reveals isolated atrophy of the infraspinatus with normal supraspinatus bulk and strength. Where is the most likely anatomic location of the nerve compression?

Explanation

The suprascapular nerve innervates the supraspinatus and then passes through the spinoglenoid notch to innervate the infraspinatus. Compression at the suprascapular notch affects both muscles. Compression at the spinoglenoid notch (often due to a paralabral cyst associated with a SLAP tear in overhead athletes) causes isolated infraspinatus atrophy and weakness in external rotation.

Question 53

A 35-year-old female presents with a highly comminuted intra-articular distal femur fracture. CT scan reveals a coronal plane shear fracture of the lateral femoral condyle (Hoffa fracture). What is the optimal direction of lag screw placement for isolated fixation of this specific condylar fragment to maximize biomechanical stability?

Explanation

A Hoffa fracture is a coronal shear fracture of the femoral condyle. Biomechanical studies demonstrate that anterior-to-posterior lag screw fixation (often countersunk through the anterior articular cartilage or placed just proximal to the trochlea) provides the most stable construct to resist the posterior shear forces exerted by the gastrocnemius muscles.

Question 54

A 60-year-old diabetic male presents with severe back pain, fever, and progressive lower extremity weakness over 48 hours. MRI reveals a spinal epidural abscess. What is the most common route of bacterial entry and the most common causative organism?

Explanation

The most common route of infection for a spinal epidural abscess is hematogenous dissemination from a distant primary source (such as skin, soft tissue, or the urinary tract). The most commonly isolated organism is Staphylococcus aureus, accounting for over 60% of these infections.

Question 55

A 22-year-old rugby player has recurrent anterior shoulder instability. A 3D CT scan is obtained to calculate the 'glenoid track'. If the patient's Hill-Sachs interval (HSI) is determined to be greater than the calculated glenoid track, what is the most appropriate management alongside an anterior stabilization procedure?

Explanation

According to the glenoid track concept, if the Hill-Sachs interval (width of the defect plus the intact bone bridge to the rotator cuff insertion) is greater than the glenoid track, the lesion is 'off-track' and will engage the anterior glenoid rim during abduction/external rotation. An isolated Bankart repair has an unacceptably high failure rate in off-track lesions; a Remplissage (infraspinatus tenodesis into the defect) or a bone block (Latarjet) is indicated.

Question 56

A 30-year-old male sustains a multi-ligamentous knee injury (KD III) following a tackle. On arrival, his foot is warm and pink, but the dorsalis pedis pulse is weakly palpable compared to the contralateral side. The Ankle-Brachial Index (ABI) is 0.85. What is the next most appropriate step in management?

Explanation

In the setting of a knee dislocation, vascular injury (popliteal artery) is a major concern. An ABI < 0.9 or asymmetric pulses indicate a high suspicion for vascular compromise, requiring a CT angiogram or conventional angiogram. Immediate exploration without imaging is reserved for 'hard signs' of ischemia (e.g., absent pulses, active pulsatile bleeding, expanding hematoma, cold/pale foot).

Question 57

A 40-year-old male agricultural worker from the San Joaquin Valley presents with a chronic draining lesion over his patella. Radiographs show a lytic lesion. Histopathology of a biopsy reveals spherules containing endospores. What is the most appropriate initial pharmacological treatment after surgical debridement?

Explanation

The patient has osseous Coccidioidomycosis ('Valley Fever'), which is endemic to the southwestern US. The hallmark histological finding is spherules containing endospores. Treatment for fungal osteoarticular infections typically involves surgical debridement followed by systemic antifungal therapy, commonly Intravenous Amphotericin B for severe disease, or prolonged oral azole therapy (Itraconazole or Fluconazole).

Question 58

A 65-year-old male has active forward elevation of his right arm to only 45 degrees, though passive elevation is 160 degrees. MRI demonstrates a massive, retracted tear of the supraspinatus and infraspinatus. To determine if a reverse total shoulder arthroplasty (RTSA) is indicated, an injection of local anesthetic into the subacromial space is performed. What is the rationale for this test?

Explanation

The subacromial injection test is used to differentiate pain-mediated weakness (pseudoparesis) from true structural inability to elevate the arm (pseudoparalysis). If pain relief from the injection allows the patient to actively elevate the arm >90 degrees, they have pseudoparesis. If they still cannot elevate the arm despite adequate pain relief, they have true pseudoparalysis, which is an excellent indication for RTSA.

Question 59

A 19-year-old male is tackled and presents with severe right upper chest pain, stridor, and difficulty swallowing. Imaging confirms a posterior sternoclavicular (SC) joint dislocation. Which of the following structures lies immediately posterior to the medial clavicle and is at greatest risk of direct mechanical injury during this displacement?

Explanation

Posterior SC dislocations are medical emergencies due to the proximity of critical mediastinal structures. The most anterior vascular structure lying directly posterior to the SC joint is the brachiocephalic (innominate) vein. While the trachea, esophagus, and subclavian vessels are also at risk, the innominate vein is geographically the closest major structure at risk of laceration or compression.

Question 60

Polymethylmethacrylate (PMMA) bone cement is frequently used to deliver local antibiotics in the treatment of orthopedic infections. Which of the following properties is a critical requirement for an antibiotic to be effectively and safely incorporated into PMMA?

Explanation

To be effectively mixed with PMMA, an antibiotic must possess thermal stability (to withstand the exothermic reaction of cement polymerization which can reach high temperatures) and water solubility (to allow it to elute out of the hydrophobic cement matrix into the surrounding aqueous tissue environment). Aminoglycosides (tobramycin) and glycopeptides (vancomycin) fit these criteria well.

Question 61

During an ilioinguinal approach for the fixation of an anterior column acetabular fracture, a significant bleeding vessel is encountered crossing over the superior pubic ramus at a distance of approximately 5 cm from the pubic symphysis. This vessel, commonly referred to as the corona mortis, represents an anastomosis between which two vascular systems?

Explanation

The corona mortis ('crown of death') is a vascular anastomosis between the obturator vessels (branching from the internal iliac system) and the external iliac or inferior epigastric vessels. It crosses the superior pubic ramus and is highly susceptible to iatrogenic injury during the ilioinguinal approach or the modified Stoppa approach to the acetabulum/pelvis.

Question 62

A 72-year-old male with severe rotator cuff tear arthropathy undergoes a reverse total shoulder arthroplasty (RTSA). The surgeon decides to use a lateralized glenosphere construct. Which of the following is a biomechanical consequence of lateralizing the glenosphere in an RTSA?

Explanation

Lateralizing the glenosphere in RTSA improves deltoid wrapping, increases stability, reduces the risk of scapular notching, and improves external rotation contour compared to a medialized design. However, the medialized center of rotation in a Grammont-style prosthesis was specifically designed to reduce torque on the glenoid component. Therefore, lateralizing the glenosphere increases the moment arm and creates increased shear stress at the baseplate-bone interface, theoretically increasing the risk of baseplate loosening.

Question 63

In the diagnostic workup for periprosthetic joint infection (PJI), the alpha-defensin immunoassay is frequently utilized as a highly specific synovial fluid biomarker. Alpha-defensin is an antimicrobial peptide primarily secreted by which of the following cell types in response to pathogens?

Explanation

Alpha-defensin is an antimicrobial peptide naturally secreted by host neutrophils in response to the presence of bacterial pathogens. It has high sensitivity and specificity for the diagnosis of PJI and is less affected by prior antibiotic administration than standard synovial fluid cultures.

Question 64

A 35-year-old male sustains a posterior wall acetabular fracture with a concomitant posterior hip dislocation. During open reduction and internal fixation, an area of marginal impaction of the articular surface is identified. Which of the following surgical steps regarding this impacted fragment is most critical to prevent rapid onset of post-traumatic arthrosis?

Explanation

Marginal impaction refers to the depression of the osteochondral articular surface into the underlying cancellous bone of the acetabulum. Failure to recognize, elevate, and bone graft this impacted articular segment leads to incongruity of the joint surface, which is the most reliable predictor of poor clinical outcomes and rapid post-traumatic arthrosis following posterior wall acetabular fractures.

Question 65

A 22-year-old contact athlete undergoes a Latarjet procedure for recurrent anterior shoulder instability associated with 25% glenoid bone loss. The 'sling effect' of this procedure, which contributes significantly to stability at end-range abduction and external rotation, is primarily mediated by which of the following structures?

Explanation

The Latarjet procedure provides stability through a 'triple blocking' effect. The most important dynamic stabilizer is the 'sling effect' created by the conjoint tendon (short head of biceps and coracobrachialis) as it passes through the lower third split of the subscapularis muscle. When the arm is in abduction and external rotation, the conjoint tendon acts as a sling across the anterior-inferior capsule to prevent anterior translation of the humeral head.

Question 66

According to the Cierny-Mader classification system for osteomyelitis, a 'localized' (Type III) lesion is best defined by which of the following clinical and radiographic characteristics?

Explanation

The Cierny-Mader classification defines osteomyelitis by anatomy and host status. Type I is medullary, Type II is superficial (periosteal), Type III is localized, and Type IV is diffuse. A Type III (localized) lesion is characterized by a full-thickness cortical sequestration or cavitation that can be surgically excised without compromising the mechanical stability of the bone prior to debridement. Type IV (diffuse) involves circumferential disease that requires segmental resection, leading to mechanical instability.

Question 67

A 55-year-old female undergoes open reduction and internal fixation of a comminuted distal femur fracture (OTA/AO 33-C2) using a lateral locked plate. Which of the following technical errors during fixation most significantly increases the risk of asymmetric callus formation and subsequent nonunion?

Explanation

Bridge plating of comminuted fractures relies on relative stability to promote secondary bone healing via callus formation. Excessive rigidity, commonly caused by using too many locking screws near the fracture site (inadequate working length), prevents the interfragmentary micro-motion necessary for callus formation, particularly on the far cortex. This leads to asymmetric callus and a high risk of nonunion and hardware failure.

Question 68

A 65-year-old female sustains a 3-part proximal humerus fracture involving the surgical neck and the greater tuberosity. The greater tuberosity fragment is characteristically displaced by the primary deforming forces of the attached musculature. In which direction is this fragment typically displaced, and by which muscles?

Explanation

In proximal humerus fractures, the greater tuberosity is the attachment site for the supraspinatus, infraspinatus, and teres minor. When fractured, it is predictably displaced superiorly and posteriorly due to the unopposed pull of the supraspinatus and infraspinatus muscles.

Question 69

A 48-year-old male presents with a rapidly expanding erythematous lesion on his lower leg, severe pain out of proportion to the clinical exam, and hemorrhagic bullae. The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is calculated to distinguish this from severe cellulitis. Which of the following laboratory parameters is a component of the LRINEC score?

Explanation

The LRINEC score uses six routine laboratory parameters to stratify the risk of necrotizing fasciitis: C-reactive protein (CRP), total white blood cell count (WBC), Hemoglobin, Serum sodium (Na < 135 mEq/L scores 2 points), Serum creatinine, and Serum glucose. Serum lactate, though indicative of sepsis/tissue hypoperfusion, is not a variable in the original LRINEC score.

Question 70

A 30-year-old male presents 3 months after a conservatively managed, closed tibial shaft fracture with a progressive claw toe deformity of his lesser toes. He reports no pain but has difficulty fitting into shoes. Clinical examination reveals fixed flexion contractures at the distal interphalangeal joints of the lesser toes. Ischemic contracture of which of the following muscles is the most likely etiology?

Explanation

The patient is exhibiting signs of a missed deep posterior compartment syndrome of the leg. The deep posterior compartment contains the Tibialis posterior, Flexor digitorum longus (FDL), and Flexor hallucis longus (FHL). Ischemic contracture of the FDL leads to clawing of the lesser toes, whereas FHL contracture would lead to clawing of the great toe.

Question 71

An elite baseball pitcher is diagnosed with a Type II Superior Labrum Anterior to Posterior (SLAP) tear. The 'peel-back' mechanism is considered the primary biomechanical etiology for this injury in overhead throwers. In which phase of the throwing motion does this peel-back force peak?

Explanation

The 'peel-back' mechanism occurs during the late cocking phase of throwing. In this phase, the shoulder is in maximum abduction and external rotation, which places maximal torsional stress on the base of the biceps tendon. This force transmits to the superior labrum, causing it to 'peel back' and detach from the glenoid rim.

Question 72

A 34-year-old mechanic presents with an infected puncture wound on his index finger. He exhibits the four cardinal signs of suppurative flexor tenosynovitis (Kanavel's signs). Which of these signs is typically the earliest to manifest and is considered the most sensitive indicator of this condition?

Explanation

Kanavel's four signs of flexor tenosynovitis are: 1) fusiform swelling, 2) flexed resting posture, 3) tenderness along the flexor sheath, and 4) pain with passive extension. Pain with passive extension is typically the earliest and most sensitive sign of suppurative flexor tenosynovitis.

Question 73

A 40-year-old male undergoes open reduction and internal fixation of a displaced intra-articular calcaneus fracture utilizing a standard extensile lateral approach. The viability of the full-thickness, 'no-touch' fasciocutaneous flap created during this approach relies primarily on the vascular supply from which of the following arteries?

Explanation

The extensile lateral approach to the calcaneus involves creating a full-thickness fasciocutaneous flap. The blood supply to this flap is primarily provided by the lateral calcaneal artery, a terminal branch of the peroneal artery. The surgical incision must be planned carefully to protect this angiosome to prevent disastrous wound complications.

Question 74

A 55-year-old manual laborer with an irreparable, massive posterosuperior rotator cuff tear and intact cartilage undergoes a Superior Capsular Reconstruction (SCR) using a thick dermal allograft. The primary biomechanical goal of the dermal allograft in this procedure is to:

Explanation

Superior Capsular Reconstruction (SCR) addresses irreparable supraspinatus/infraspinatus tears. The graft is attached medially to the superior glenoid and laterally to the greater tuberosity. Its primary biomechanical function is to serve as a static restraint, recreating the superior capsule to depress the humeral head and prevent its superior translation during active deltoid elevation.

Question 75

A 4-year-old boy presents with right hip pain and refusal to bear weight. Which of the following combinations of parameters comprises the original Kocher criteria, utilized to differentiate pediatric septic arthritis of the hip from transient synovitis?

Explanation

The original Kocher criteria for differentiating septic arthritis from transient synovitis in children include four parameters: Non-weight-bearing status on the affected side, Erythrocyte sedimentation rate (ESR) > 40 mm/hr, Fever > 38.5 C (101.3 F), and a Serum white blood cell (WBC) count > 12,000 cells/mm3. (Note: CRP > 2.0 mg/dL was later added as a fifth independent predictor in Caird's modification).

Question 76

In the management of a 'floating shoulder' (ipsilateral displaced clavicle and scapular neck fractures), open reduction and internal fixation of the clavicle alone is often sufficient to indirectly reduce the scapular neck. However, operative fixation of the scapula is specifically indicated over clavicle-only fixation if the glenopolar angle (GPA) falls below what threshold?

Explanation

The glenopolar angle (GPA) assesses the rotational displacement of the glenoid in scapular neck fractures. The normal GPA is between 30 and 45 degrees. A severely decreased GPA (typically < 22 degrees) is associated with poor functional outcomes and is a recognized indication for direct operative fixation of the scapula, rather than relying on indirect reduction via clavicular fixation.

Question 77

A 19-year-old male sustains a posterior sternoclavicular dislocation during a rugby match. The orthopedic surgeon plans an open reduction. During preoperative planning, the surgeon recalls that the medial clavicle physis is typically the last primary ossification center to fuse in the human body. This may mean the injury is a physeal fracture rather than a true dislocation. At what age does the medial clavicular physis typically fuse?

Explanation

The medial clavicle physis is the last growth plate in the body to fuse. Ossification begins around age 18, and complete fusion does not occur until 23 to 25 years of age. Therefore, apparent sternoclavicular dislocations in patients under 25 are frequently Salter-Harris physeal fractures.

Question 78

In the surgical management of chronic post-traumatic osteomyelitis, antibiotic-impregnated polymethylmethacrylate (PMMA) beads are placed into the dead space following radical debridement. To maximize the rate and duration of local antibiotic elution from the PMMA spacer, which of the following techniques is most appropriate?

Explanation

Antibiotic elution from PMMA is a surface phenomenon. Maximizing elution requires increasing the surface area and the porosity of the cement. Hand-mixing cement (rather than vacuum mixing) incorporates air, increasing porosity and thus elution. Using beads (high surface-area-to-volume ratio) also increases elution compared to a solid block. Adding liquid antibiotics compromises the cement severely and is not recommended in large volumes.

Question 79

A 24-year-old athlete sustains a hyperplantarflexion injury to his foot and presents with severe midfoot pain and plantar ecchymosis. Weight-bearing radiographs demonstrate a 3 mm diastasis between the base of the first and second metatarsals. The primary ligamentous structure disrupted in this injury (the Lisfranc ligament) anatomically originates from the:

Explanation

The Lisfranc ligament is an interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is critical for the stability of the midfoot arch. There is no direct ligamentous connection between the bases of the first and second metatarsals.

Question 80

A 32-year-old motorcyclist is brought to the trauma bay following a high-speed collision. He presents with a flail, pulseless right upper extremity. An anteroposterior chest radiograph reveals a displaced clavicle fracture and a laterally displaced scapula compared to the contralateral side. Recognizing this pattern as a likely scapulothoracic dissociation, which of the following is the most appropriate next step to diagnose the extent of the most life- and limb-threatening associated injury?

Explanation

Scapulothoracic dissociation is a devastating closed forequarter amputation characterized by lateral displacement of the scapula, clavicle fracture or AC/SC joint disruption, and severe neurovascular injury. Vascular injury (subclavian or axillary artery) occurs in up to 88% of cases and is life-threatening. Therefore, an immediate CT angiogram (or formal angiography) is the most critical next step to evaluate for vascular injury in a pulseless extremity.

Question 81

A 22-year-old rugby player presents with recurrent anterior shoulder instability. CT evaluation reveals 25% anterior glenoid bone loss. Which of the following procedures is most appropriate to restore stability?

Explanation

In cases of anterior shoulder instability with critical glenoid bone loss (>20-25%), a coracoid transfer (Latarjet procedure) is the gold standard. Soft tissue procedures alone, such as an arthroscopic Bankart repair, have unacceptably high failure rates in this setting.

Question 82

A 30-year-old male sustains a high-energy vertically oriented (Pauwels type III) displaced femoral neck fracture. Which of the following fixation constructs provides the most biomechanically stable construct against vertical shear forces?

Explanation

Pauwels III fractures experience high vertical shear forces. A sliding hip screw (fixed-angle construct) combined with an anti-rotation screw provides superior biomechanical stability against shear compared to multiple parallel cannulated screws.

Question 83

When evaluating a patient for a suspected periprosthetic joint infection (PJI), a synovial fluid leukocyte esterase (LE) test is performed. Which of the following is the most common cause of a false-positive LE test in this setting?

Explanation

The leukocyte esterase strip test relies on a colorimetric change to detect the enzyme produced by neutrophils. Significant amounts of red blood cells (bloody aspirate) can obscure the color change or cause a false-positive reading.

Question 84

Which of the following best describes the biomechanical rationale of a reverse total shoulder arthroplasty (RTSA) in the setting of rotator cuff tear arthropathy?

Explanation

RTSA medializes and inferiorly shifts the joint's center of rotation. This increases the deltoid's moment arm and resting tension, allowing it to initiate and maintain forward elevation in the absence of a functional rotator cuff.

Question 85

A 28-year-old male sustains a Hawkins Type III talar neck fracture. Which of the following describes the anatomic displacement and the primary blood supply at greatest risk?

Explanation

A Hawkins Type III fracture involves displacement of the talar neck with subluxation or dislocation of both the subtalar and tibiotalar joints. It severely disrupts the artery of the tarsal canal (branch of the posterior tibial artery), which is the major blood supply to the talar body.

Question 86

A 45-year-old construction worker sustains a Gustilo-Anderson Type IIIB open tibia fracture. According to current evidence, what is the most critical initial factor in preventing a deep infection?

Explanation

The most significant independent factor in reducing infection rates in open fractures is the early administration of systemic antibiotics, ideally within 1 hour of injury. Timing of soft tissue coverage is also important but secondary to immediate antibiotic prophylaxis.

Question 87

During a surgical reconstruction for a chronic Type V acromioclavicular (AC) joint separation, the surgeon aims to reconstruct the coracoclavicular ligaments. What is the approximate anatomic distance from the distal clavicle to the normal insertion of the conoid ligament?

Explanation

The conoid ligament inserts approximately 4.5 cm medial to the distal articular end of the clavicle, while the trapezoid ligament inserts approximately 3.0 cm medial to it. Knowledge of this anatomy is crucial for accurate tunnel placement during reconstruction.

Question 88

A 32-year-old male develops acute compartment syndrome of the leg following a tibial plateau fracture. Which clinical finding specifically isolates involvement of the deep posterior compartment?

Explanation

The deep posterior compartment contains the flexor hallucis longus (FHL), flexor digitorum longus (FDL), and tibialis posterior. Pain with passive extension of the toes (which stretches the FHL and FDL) is a classic sign of deep posterior compartment ischemia.

Question 89

In the pathogenesis of periprosthetic joint infection, biofilm maturation allows bacteria to become highly resistant to host defenses and antimicrobials. Which biological process allows bacteria to coordinate gene expression according to the local density of their population?

Explanation

Quorum sensing is an intercellular communication mechanism that allows bacteria to share information about cell density and adjust gene expression accordingly. This process is critical for biofilm maturation and the development of antibiotic resistance.

Question 90

A 65-year-old female presents with a displaced 4-part proximal humerus fracture. According to the Hertel criteria, which radiographic finding is the most reliable predictor of humeral head ischemia?

Explanation

Hertel et al. identified that a metaphyseal head extension (calcar length) of < 8 mm, disruption of the medial hinge, and an anatomical neck fracture pattern are the most highly predictive factors for humeral head ischemia. A short calcar length indicates loss of critical vascular supply from the anterior humeral circumflex artery.

Question 91

During the ilioinguinal approach for an anterior column acetabular fracture, the surgeon encounters significant bleeding from the "corona mortis". This vascular structure represents an anastomosis between which two vessels?

Explanation

The corona mortis is an anatomic variant representing an anastomosis between the external iliac (or inferior epigastric) system and the obturator system. It is located over the superior pubic ramus and is at high risk during anterior pelvic/acetabular exposures.

Question 92

A 4-year-old boy presents with a limp, right hip pain, and a temperature of 38.8°C. His WBC count is 14,000/mm3, ESR is 50 mm/hr, and CRP is 3.5 mg/dL. He refuses to bear weight. Based on the Kocher and Caird criteria, what is the approximate probability that this child has septic arthritis rather than transient synovitis?

Explanation

This patient has 5 out of 5 criteria (fever > 38.5°C, non-weight bearing, ESR > 40, WBC > 12k, and CRP > 2.0 mg/dL). The presence of 4 or more criteria yields a 93-99% predictive probability for pediatric septic arthritis of the hip.

Orthopedic Surgery Board Review MCQs: Arthroplasty, Trauma & Spine Part 255

Orthopedic Surgery Board Review MCQs: Trauma, Infection & Shoulder | Part 59

Key Takeaway

Orthopedic Surgery Board Review MCQs: Trauma, Infection & Shoulder | Part 59

Chapter Index