Orthopedic MCQs: Shoulder, Trauma, Infection - Part 69

Question 1

A 72-year-old female undergoes a reverse total shoulder arthroplasty (rTSA). To minimize the risk of inferior scapular notching, how should the glenosphere baseplate be optimally positioned?

Explanation

Scapular notching is a common complication of rTSA, particularly with Grammont-style implants, where the humeral component abuts the inferior scapular neck. To minimize this, biomechanical and clinical studies recommend placing the baseplate (glenosphere) with inferior translation (overhanging the inferior glenoid rim by 2-4mm) and inferior tilt (approximately 10-15 degrees). This allows the humeral cup to clear the inferior scapular neck during adduction.

Question 2

A 35-year-old male is brought to the trauma bay after a high-speed motorcycle collision. He has a mechanically unstable anterior-posterior compression (APC) type III pelvic ring injury and remains hemodynamically unstable despite initial fluid resuscitation. What is the most common anatomical source of his massive pelvic hemorrhage?

Explanation

While arterial bleeding (e.g., from the internal pudendal, obturator, or superior gluteal arteries) can occur and be life-threatening, the vast majority (up to 80-90%) of pelvic hemorrhage in high-energy ring disruptions arises from the disrupted presacral venous plexus and bleeding from fractured cancellous bone surfaces.

Question 3

A 68-year-old male presents with a painful total knee arthroplasty. Synovial fluid analysis is sent for alpha-defensin testing. What best describes the origin and nature of alpha-defensin in the setting of periprosthetic joint infection?

Explanation

Alpha-defensin is a naturally occurring antimicrobial peptide released by human neutrophils in response to the presence of pathogens. It has demonstrated very high sensitivity and specificity for diagnosing periprosthetic joint infections (PJI) and has the added benefit of maintaining accuracy even if the patient has been subjected to prior antibiotic administration.

Question 4

A 22-year-old collegiate rugby player presents with recurrent anterior shoulder instability. A CT scan with 3D reconstruction demonstrates 22% anterior glenoid bone loss and an engaging Hill-Sachs lesion. Which of the following is the most appropriate definitive surgical management?

Explanation

Engaging Hill-Sachs lesions in the presence of >20% anterior glenoid bone loss represent 'off-track' lesions with severe bone deficiency. Soft tissue stabilization (Bankart repair), even with remplissage, is associated with unacceptably high failure rates in this setting. The Latarjet procedure (coracoid transfer) restores the bony arc of the glenoid and provides a dynamic soft-tissue sling effect via the conjoint tendon, making it the standard of care.

Question 5

A 45-year-old male sustains a Schatzker IV tibial plateau fracture. The surgeon elects to use a posteromedial surgical approach. Which of the following represents the correct intermuscular interval for this approach?

Explanation

The posteromedial approach to the proximal tibia is frequently used to buttress medial plateau fractures (Schatzker IV). The standard superficial internervous/intermuscular interval is between the pes anserinus tendons (anteriorly) and the medial head of the gastrocnemius (posteriorly). The gastrocnemius is retracted posteriorly and laterally to protect the popliteal neurovascular bundle.

Question 6

The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is used to help distinguish necrotizing fasciitis from severe cellulitis. Which of the following laboratory values is a specific component that adds points to the LRINEC score?

Explanation

The LRINEC score incorporates six laboratory parameters: CRP (>150 mg/L), WBC count (elevated, with higher points for >25), Hemoglobin (decreased, <13.5 or <11), Serum Sodium (<135 mmol/L adds 2 points), Serum Creatinine (>1.41 mg/dL), and Glucose (>180 mg/dL). Platelets, calcium, potassium, and BUN are not components of the LRINEC score.

Question 7

A 55-year-old manual laborer has a massive, irreparable posterosuperior rotator cuff tear. The surgeon is considering a latissimus dorsi tendon transfer. Which of the following is considered an absolute contraindication to this procedure?

Explanation

Latissimus dorsi tendon transfer is indicated for massive, irreparable posterosuperior rotator cuff tears (supraspinatus/infraspinatus) in younger patients without significant glenohumeral arthritis. An intact and functioning subscapularis is an absolute prerequisite; it is required to provide an anterior force couple. If the subscapularis is incompetent, the humeral head will subluxate anterosuperiorly, leading to clinical failure of the transfer.

Question 8

A 28-year-old female sustains a Pauwels type III (vertical) femoral neck fracture. Which of the following internal fixation constructs provides the greatest biomechanical stability against vertical shear forces?

Explanation

Vertical femoral neck fractures (Pauwels III, angle >50 degrees) experience very high shear forces, leading to high rates of varus collapse and nonunion when treated with standard parallel cancellous screws. Biomechanical studies have consistently demonstrated that a fixed-angle construct, specifically a sliding hip screw supplemented with a derotation screw, provides significantly superior resistance to vertical shear forces.

Question 9

A 60-year-old male with a 30-year history of chronic tibial osteomyelitis presents with a rapidly growing, fungating, and malodorous mass arising from his chronic sinus tract. Biopsy is most likely to reveal which of the following pathologies?

Explanation

Marjolin's ulcer refers to malignant transformation that occurs within chronic wounds, burn scars, or chronic osteomyelitis sinus tracts. The most common histologic type by far is squamous cell carcinoma, which tends to be highly aggressive and has a high rate of metastasis in this setting.

Question 10

A 19-year-old male undergoes open reduction and internal fixation of a displaced midshaft clavicle fracture using a superiorly applied pre-contoured plate. Postoperatively, he complains of a numb patch of skin over his anterior chest wall. Which nerve was most likely injured during the surgical approach?

Explanation

The supraclavicular nerves (C3-C4 roots from the superficial cervical plexus) branch outward over the clavicle to provide sensation to the anterior chest wall. They are frequently encountered and are at high risk of iatrogenic injury or entrapment during superior plating of midshaft clavicle fractures, resulting in a predictable area of anterior chest numbness.

Question 11

A 30-year-old male sustains a Hawkins Type III talar neck fracture (fracture with subtalar and tibiotalar dislocation). Which of the following vessels provides the primary blood supply to the talar body and is almost universally disrupted in this injury pattern?

Explanation

The talus has a tenuous, retrograde blood supply. The artery of the tarsal canal (a branch of the posterior tibial artery) supplies the majority of the talar body. In a Hawkins III fracture, the anastomotic vessels in the tarsal canal, sinus tarsi, and superior neck are disrupted, leading to a near 100% rate of avascular necrosis of the talar body.

Question 12

A 70-year-old female with a chronic staphylococcal periprosthetic joint infection of the hip is treated with a two-stage exchange arthroplasty. Her systemic antibiotic regimen includes rifampin due to its excellent biofilm penetration. What is the molecular mechanism of action of rifampin?

Explanation

Rifampin is highly active against Staphylococcal biofilms because it penetrates the biofilm matrix well and acts by binding to and inhibiting bacterial DNA-dependent RNA polymerase, thereby preventing RNA transcription. It must always be used in combination with other agents to prevent the rapid emergence of resistance.

Question 13

Recent quantitative anatomical studies have redefined the primary arterial supply to the proximal humeral head, altering historical teaching. Based on current evidence, which of the following vessels provides the majority of the extraosseous blood supply to the humeral head?

Explanation

Historically, the anterior circumflex humeral artery (via its anterolateral arcuate branch) was taught to be the primary blood supply to the humeral head. However, landmark modern quantitative studies (e.g., Hettrich et al.) demonstrated that the posterior circumflex humeral artery actually provides the majority (approximately 64%) of the extraosseous blood supply to the humeral head.

Question 14

A 25-year-old male sustains a closed comminuted tibial shaft fracture. The orthopedic surgeon is evaluating the patient for acute compartment syndrome using continuous intra-compartmental pressure monitoring. Which of the following correctly defines the 'delta P' threshold commonly used to indicate the absolute need for a fasciotomy?

Explanation

Acute compartment syndrome is defined by inadequate tissue perfusion due to elevated intracompartmental pressure. The 'delta P' is calculated as the diastolic blood pressure minus the compartment pressure. A delta P of less than 30 mmHg is considered the critical threshold for tissue ischemia and is an absolute indication for emergency fasciotomy.

Question 15

A 2-year-old girl is diagnosed with septic arthritis of the knee. Synovial fluid PCR identifies Kingella kingae. Which of the following best describes the bacteriology of this organism?

Explanation

Kingella kingae is a Gram-negative coccobacillus that is increasingly recognized as a leading cause of pediatric septic arthritis and osteomyelitis in children aged 6 months to 4 years. It is a fastidious organism that is often missed on standard solid agar cultures; thus, inoculation into BACTEC liquid blood culture vials or detection via PCR is required for reliable identification.

Question 16

A 40-year-old female presents with shoulder pain, inability to actively abduct the arm beyond 90 degrees, and lateral scapular winging following a posterior triangle cervical lymph node biopsy. Which of the following tendon transfers (Eden-Lange procedure) is classically indicated for her condition?

Explanation

Injury to the spinal accessory nerve during posterior triangle neck surgery results in trapezius palsy, characterized clinically by lateral scapular winging and loss of active abduction. The Eden-Lange procedure is the classic tendon transfer used to treat this condition; it involves transferring the levator scapulae to the acromion, and the rhomboids major and minor to the infraspinatus fossa to replicate the absent force vectors of the trapezius.

Question 17

During open reduction and internal fixation of a posterior wall acetabular fracture via a Kocher-Langenbeck approach, the surgeon places the patient's operative leg in a specific position to minimize tension on the sciatic nerve. Which position is most appropriate, and which division of the nerve is at highest risk of iatrogenic injury?

Explanation

During the Kocher-Langenbeck approach, the sciatic nerve is at high risk of iatrogenic stretch injury from retractors. Extending the hip and flexing the knee maximally relaxes the sciatic nerve. The peroneal division is located more laterally, possesses less supportive perineural connective tissue, and is mechanically tethered distally at the fibular head, making it significantly more susceptible to stretch injuries than the tibial division.

Question 18

A 35-year-old carpenter presents with a swollen, painful index finger 3 days after a puncture wound. The physician suspects acute pyogenic flexor tenosynovitis. According to Kanavel's cardinal signs, which of the following is typically the earliest and most sensitive clinical finding?

Explanation

Kanavel's four classic signs of acute pyogenic flexor tenosynovitis are: 1) flexed resting posture of the digit, 2) fusiform (sausage-like) swelling, 3) exquisite tenderness along the course of the flexor tendon sheath, and 4) severe pain elicited by passive extension. Pain with passive extension is typically the earliest, most reliable, and most sensitive clinical sign of infection within the tendon sheath.

Question 19

A 45-year-old female sustains a high-energy distal femur fracture following a motor vehicle accident. The CT scan reveals a 'Hoffa' fragment. Which of the following best describes this specific fracture pattern?

Explanation

A Hoffa fracture (AO/OTA 33-B3) is defined as an intra-articular coronal plane fracture of the distal femoral condyle. It most commonly involves the lateral condyle. Because it lies in the coronal plane, it is often radiographically occult on standard AP radiographs and is best visualized on a true lateral radiograph or CT scan. It requires AP or PA interfragmentary screw fixation for stable reconstruction.

Question 20

A 50-year-old male sustains a severe pilon fracture. The preoperative CT scan demonstrates a large, displaced anterolateral distal tibial articular fragment (the Tillaux-Chaput fragment). Which of the following ligaments remains attached to this fragment and often dictates its displacement?

Explanation

The Tillaux-Chaput fragment is the anterolateral articular fragment of the distal tibia seen in pilon or transitional ankle fractures. It serves as the primary tibial attachment site for the Anterior Inferior Tibiofibular Ligament (AITFL). Its corresponding fibular avulsion counterpart is the Wagstaffe-Le Fort fragment.

Question 21

A 22-year-old male presents with recurrent anterior shoulder instability. CT shows a Hill-Sachs lesion engaging the anterior glenoid and 25% anterior glenoid bone loss. What is the most appropriate surgical intervention?

Explanation

The Latarjet procedure is indicated for patients with recurrent anterior shoulder instability and significant glenoid bone loss (typically >20-25%). Arthroscopic Bankart repair alone in this setting has an unacceptably high failure rate.

Question 22

A 28-year-old male sustains a high-energy Pauwels type III vertical femoral neck fracture. Which of the following fixation constructs provides the greatest biomechanical stability for this fracture pattern?

Explanation

Pauwels type III fractures are highly unstable due to significant vertical shear forces. A sliding hip screw with a derotational cancellous screw provides superior biomechanical stability against vertical shear compared to three parallel screws.

Question 23

A 65-year-old male presents with acute purulent drainage 2 weeks after a primary total hip arthroplasty. Which of the following factors makes him the most appropriate candidate for debridement, antibiotics, and implant retention (DAIR)?

Explanation

DAIR is most successful when performed for acute postoperative infections (within 4 weeks of index surgery) or acute hematogenous infections with symptom duration less than 3 weeks. A sinus tract or loose components are absolute contraindications to DAIR.

Question 24

A 55-year-old male manual laborer presents with a massive, irreparable posterosuperior rotator cuff tear. He has an intact subscapularis, no glenohumeral arthritis, and lacks forward elevation. Which of the following is the most appropriate surgical treatment?

Explanation

A latissimus dorsi tendon transfer is indicated for young, active patients with massive, irreparable posterosuperior cuff tears, intact subscapularis, and no arthritis. It helps restore active external rotation and forward elevation.

Question 25

A 40-year-old male sustains a posterior wall acetabular fracture with a posterior hip dislocation. Post-reduction, he exhibits a foot drop and inability to actively extend his great toe. Which specific neural structure is most likely injured?

Explanation

The sciatic nerve is at high risk during posterior hip dislocations and posterior wall acetabular fractures. The peroneal division is more lateral, tightly tethered, and has larger fascicles, making it significantly more susceptible to injury than the tibial division.

Question 26

A 45-year-old male presents with a massive, irreparable posterosuperior rotator cuff tear. His subscapularis remains intact, and he has no glenohumeral arthritis. A lower trapezius tendon transfer is planned. To optimize its line of pull, what clinical motion is this transfer primarily designed to restore?

Explanation

Lower trapezius transfer is indicated for younger patients with irreparable posterosuperior rotator cuff tears. It effectively simulates the line of pull of the infraspinatus, primarily restoring external rotation in abduction and improving overhead function.

Question 27

A 28-year-old male sustains a vertically oriented (Pauwels III) femoral neck fracture. What is the primary biomechanical advantage of utilizing a sliding hip screw with an anti-rotation screw compared to three parallel cannulated screws for this specific fracture pattern?

Explanation

Pauwels III fractures have a high vertical shear angle that predisposes the fracture to varus collapse. A fixed-angle length-stable device, such as a sliding hip screw, resists these massive shear forces significantly better than parallel cannulated screws.

Question 28

A 65-year-old female presents 14 days after a primary total knee arthroplasty with acute purulent drainage, fever, and severe knee pain. Which of the following factors represents an absolute contraindication for a Debridement, Antibiotics, and Implant Retention (DAIR) procedure?

Explanation

Implant loosening is an absolute contraindication for a DAIR procedure. When a prosthesis is loose, the biofilm cannot be adequately eradicated, and the implants must be explanted via a one- or two-stage revision arthroplasty.

Question 29

A 70-year-old male is 3 weeks post-anatomic total shoulder arthroplasty. He reports a sudden pop and increased pain after reaching backward for a door. Examination reveals increased passive external rotation compared to the contralateral side and profound weakness in internal rotation. What is the most likely diagnosis?

Explanation

Subscapularis failure after anatomic TSA presents with anterior shoulder pain, weak internal rotation, and increased passive external rotation. It typically occurs early postoperatively due to excessive external rotation or forceful extension before the tendon has healed.

Question 30

A 70-year-old male presents 3 months after an anatomic total shoulder arthroplasty with an acute loss of active internal rotation and anterior instability. Imaging confirms a complete, retracted subscapularis failure. What is the most reliable definitive surgical treatment?

Explanation

Complete subscapularis failure after anatomic TSA leads to anterior instability and significant dysfunction. Revision to a reverse total shoulder arthroplasty (rTSA) provides the most reliable outcome, as direct repairs or tendon transfers in this setting have unacceptably high failure rates.

Question 31

A 28-year-old male sustains a vertically oriented, Pauwels type III femoral neck fracture. When treating this injury with an inverted triangle configuration of cancellous screws, what biomechanical disadvantage makes this fixation prone to failure?

Explanation

Pauwels type III fractures are highly vertical and experience significant shear forces rather than compressive forces. Standard cancellous screws offer poor resistance to these vertical shear forces, often necessitating fixed-angle devices like a sliding hip screw or cephalomedullary nail.

Question 32

A 60-year-old female is diagnosed with an acute hematogenous periprosthetic joint infection (PJI) of her total hip arthroplasty 3 weeks after an uncomplicated urinary tract infection. Her implant is 5 years old. Which factor is an absolute contraindication to Debridement, Antibiotics, and Implant Retention (DAIR)?

Explanation

DAIR is only appropriate for well-fixed implants with stable, healthy soft tissue coverage in acute or acute-hematogenous settings. A loose component requires implant removal and a one- or two-stage exchange arthroplasty.

Question 33

A 22-year-old rugby player has recurrent anterior shoulder instability. MRI arthrogram shows a Hill-Sachs lesion and an anterior glenoid bone loss of 25%. According to the 'glenoid track' concept, how is the track calculated to determine if the Hill-Sachs lesion is engaging?

Explanation

The glenoid track is calculated as 83% of the intact anterior-posterior glenoid width minus the measured anterior glenoid bone loss. If the Hill-Sachs lesion width extends medially beyond this track, it is considered 'off-track' and highly likely to engage.

Question 34

A 35-year-old male sustains a closed comminuted tibial shaft fracture. Two hours post-injury, he develops severe leg pain out of proportion. Which pressure threshold calculation is widely accepted as the most accurate indication for emergent four-compartment fasciotomy, especially in a hypotensive patient?

Explanation

While an absolute intra-compartmental pressure of 30 mm Hg or greater is commonly used, calculating the Delta P (diastolic blood pressure minus compartment pressure) of less than 30 mm Hg is the most accurate indicator for fasciotomy, minimizing unnecessary surgery in normotensive patients.

Question 35

A 45-year-old diabetic male with Charcot neuroarthropathy presents with a chronic foot ulcer and suspected osteomyelitis of the calcaneus. X-rays are inconclusive due to preexisting bony destruction. What is the most accurate nuclear imaging modality for confirming chronic osteomyelitis in this setting?

Explanation

In cases of distorted bony anatomy like Charcot arthropathy, a combined leukocyte (WBC) and marrow scan is the most specific nuclear imaging modality. It differentiates true infection (discordant increased WBC uptake) from reactive marrow changes (concordant uptake).

Question 36

In a 68-year-old female with a 4-part proximal humerus fracture, which of the following radiographic findings (Hertel's criteria) is the most reliable predictor of subsequent humeral head ischemia?

Explanation

Hertel identified that a posteromedial metaphyseal head extension (calcar length) of less than 8 mm and disruption of the medial hinge (>2 mm) are strong positive predictors of humeral head ischemia and subsequent AVN.

Question 37

A 40-year-old construction worker sustains a displaced intra-articular calcaneus fracture (Sanders Type III). Which of the following is the most significant intraoperative factor determining the long-term clinical outcome after open reduction and internal fixation?

Explanation

The anatomical reduction of the posterior facet articular surface is the most critical prognostic factor for functional outcomes. Failure to reduce the facet accurately significantly increases the risk of post-traumatic subtalar arthritis.

Question 38

A 28-year-old carpenter presents with a swollen, painful index finger 3 days after a splinter injury. On examination, the finger is held in slight flexion. Which of Kanavel's four cardinal signs is considered the earliest and most sensitive indicator of pyogenic flexor tenosynovitis?

Explanation

Pain out of proportion with passive extension is classically described as the earliest and most sensitive of Kanavel's four signs for pyogenic flexor tenosynovitis.

Question 39

A 45-year-old heavy laborer presents with a massive, retracted, and irreducible posterosuperior rotator cuff tear. His subscapularis and teres minor are completely intact. Which tendon transfer is historically indicated to restore external rotation and elevation in this specific scenario?

Explanation

Latissimus dorsi tendon transfer is indicated for younger, active patients with massive, irreparable posterosuperior rotator cuff tears (supraspinatus/infraspinatus) who have an intact subscapularis. Lower trapezius transfer is a modern alternative, but latissimus dorsi is the classic historical standard.

Question 40

A 25-year-old male sustains a severe inversion injury resulting in a Hawkins Type III talar neck fracture. What does this classification imply regarding the fracture displacement and the blood supply to the talar body?

Explanation

A Hawkins Type III fracture involves a talar neck fracture with dislocation of both the subtalar and tibiotalar joints. It carries a very high risk of avascular necrosis (frequently >80%) due to massive disruption of the talar body blood supply.

Question 41

A 24-year-old professional rugby player undergoes an open Latarjet procedure for recurrent anterior shoulder instability. Postoperatively, he presents with weakness in elbow flexion and forearm supination, as well as altered sensation over the lateral aspect of the forearm. Which nerve is most likely injured?

Explanation

The musculocutaneous nerve courses near the conjoined tendon and is at high risk during the coracoid transfer in a Latarjet procedure. Injury results in biceps and brachialis weakness (elbow flexion/supination) and sensory loss in the lateral antebrachial cutaneous nerve distribution.

Question 42

A 35-year-old male is brought to the trauma bay following a high-speed motor vehicle collision. He has a mechanically unstable anterior-posterior compression (APC) type II pelvic ring injury. A pelvic binder is to be applied to temporarily stabilize the pelvis. To be most effective, where should the binder be centered?

Explanation

A pelvic binder or sheet must be centered over the greater trochanters to effectively reduce pelvic volume and stabilize the pelvic ring. Placement over the iliac crests is incorrect and can paradoxically worsen pelvic opening or fail to control hemorrhage.

Question 43

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following is considered a major definitive criterion for the diagnosis of a periprosthetic joint infection (PJI)?

Explanation

The 2018 ICM criteria define a major criterion for PJI as either a sinus tract communicating with the prosthesis or two positive periprosthetic cultures with phenotypically identical organisms. The other options are minor criteria or clinical signs that contribute to a scoring system but are not independently diagnostic.

Question 44

Recent quantitative vascular studies assessing the blood supply to the proximal humerus have challenged historical anatomical teachings. Which artery is now recognized as providing the predominant blood supply (up to 64%) to the humeral head?

Explanation

Historically, the anterior circumflex humeral artery was thought to be the main vascular supply to the humeral head. However, recent studies demonstrate that the posterior circumflex humeral artery provides the majority of the blood supply to the proximal humerus.

Question 45

A 28-year-old male sustains a vertically oriented (Pauwels Type III) femoral neck fracture. Which of the following fixation constructs offers the greatest biomechanical stability against the high shear forces present in this fracture pattern?

Explanation

Pauwels Type III fractures are highly unstable due to significant vertical shear forces. Biomechanical studies indicate that a fixed-angle device, such as a sliding hip screw combined with an anti-rotation screw, provides superior stability compared to parallel cannulated screws in young patients.

AAOS & ABOS Upper Extremity MCQs (Set 4): Shoulder, Elbow, Wrist, Hand & Nerve Review | 2025-2026 Boards

Orthopedic Surgery Board Review MCQs: Shoulder, Trauma, & Infection - AAOS Master Bank Part 69

Key Takeaway

Orthopedic Surgery Board Review MCQs: Shoulder, Trauma, & Infection - AAOS Master Bank Part 69

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