ABOS Part I & AAOS OITE Orthopaedic Surgery Review: Comprehensive MCQ Cases | Part 22298

ABOS Part I Comprehensive Review - Batch 94

This module contains 51 advanced orthopedic multiple-choice questions developed to mirror the American Board of Orthopaedic Surgery (ABOS) Part I and AAOS OITE examinations. Questions are derived directly from high-yield clinical teaching cases.

Generated MCQ Transcript

Question 1:

A 14-year-old male presents with left distal femoral pain and swelling. Imaging reveals a large metaphyseal lesion with cortical destruction and soft tissue extension. Biopsy confirms high-grade osteosarcoma. A whole-body PET-CT scan shows no distant metastases but highlights a separate, small, enhancing lesion within the same femur, proximal to the primary tumor. According to the 8th edition UICC staging criteria for bone sarcomas, what is the correct T-stage for this patient's primary tumor?

• A: T1
• B: T2
• C: T3
• D: Tx
• E: T4

Explanation:

Correct Answer: C

For bone sarcomas (like osteosarcoma), the 8th edition UICC T-staging system is as follows: T1 is for tumors ≤ 8 cm, T2 for tumors > 8 cm. T3 is specifically designated for discontinuous tumor foci in the primary bone, commonly known as 'skip lesions.' The description of a separate, enhancing lesion within the same femur proximal to the primary tumor perfectly fits the definition of a skip lesion, regardless of the primary tumor's size. Therefore, the T-stage is T3.

Question 2:

A 65-year-old male presents with a progressively enlarging, painless mass in his right thigh for 6 months. MRI reveals a 12 cm deep-seated, heterogeneous mass. Biopsy confirms high-grade pleomorphic undifferentiated sarcoma (PUS). Imaging of the chest, abdomen, and pelvis is negative for metastases, and lymph nodes are unremarkable. What is the correct UICC T-stage for this soft tissue sarcoma of the extremity?

• A: T1
• B: T2
• C: T3
• D: T4
• E: Tx

Explanation:

Correct Answer: C

For soft tissue sarcomas of the trunk and extremities, the 8th edition UICC T-staging is based primarily on tumor size: T1 for tumors ≤ 5 cm, T2 for tumors > 5 cm and ≤ 10 cm, and T3 for tumors > 10 cm. The described tumor is 12 cm, which places it in the T3 category. T4 is reserved for tumors of any size with invasion of major neurovascular structures, bone, joint, or visceral organs. Since invasion of these critical structures is not mentioned, T3 is the correct stage based on size alone.

Question 3:

In the context of the UICC staging system for musculoskeletal sarcomas, which factor is not a primary determinant of the Grade (G) component?

• A: Tumor cellularity
• B: Mitotic activity
• C: Extent of necrosis
• D: Pleomorphism
• E: Tumor size

Explanation:

Correct Answer: E

The Grade (G) component in the UICC staging system for musculoskeletal sarcomas, particularly for soft tissue sarcomas (often using the FNCLCC system), is determined by histopathological features such as tumor differentiation, mitotic activity, and the extent of tumor necrosis. Pleomorphism and cellularity are aspects of differentiation. Tumor size, however, is a primary determinant of the T-stage (primary tumor extent), not the G-stage (histological grade). Therefore, tumor size is not a primary determinant of the Grade component.

Question 4:

A 28-year-old female is diagnosed with a high-grade synovial sarcoma in her left forearm. Staging workup reveals a single, isolated pulmonary nodule consistent with metastatic disease. There is no regional lymph node involvement. According to the 8th edition UICC staging for soft tissue sarcomas, what is the overall stage group?

• A: Stage IIB
• B: Stage III
• C: Stage IVA
• D: Stage IVB
• E: Stage IA

Explanation:

Correct Answer: C

The presence of distant metastases (M1) automatically upstages any sarcoma to Stage IV. For soft tissue sarcomas in the 8th edition UICC, M1 disease is classified as Stage IVA if there are no regional lymph node metastases (N0). If regional lymph node metastases (N1) are present alongside distant metastases, it would be Stage IVB. In this case, with M1 and N0, the overall stage is IVA.

Question 5:

Which of the following describes the M1a designation for bone sarcomas in the 8th edition UICC staging system?

• A: Distant metastasis to lung only
• B: Distant metastasis to bone only
• C: Distant metastasis to other sites (e.g., liver)
• D: Regional lymph node metastasis
• E: Peritoneal metastasis

Explanation:

Correct Answer: A

In the 8th edition UICC staging system for bone sarcomas (e.g., osteosarcoma, Ewing sarcoma), M1a specifically refers to distant metastasis to the lung only. M1b refers to distant metastasis to bone or other distant sites (e.g., liver, brain). This distinction can be important prognostically, as isolated lung metastases sometimes have a better prognosis and are amenable to surgical resection in select cases.

Question 6:

For patients with primary bone sarcoma, which of the following is the most significant factor influencing the prognosis of those with localized disease?

• A: Patient's age at diagnosis
• B: Tumor size
• C: Primary tumor location (axial vs. appendicular)
• D: Response to neoadjuvant chemotherapy (pathologic necrosis)
• E: Histological subtype

Explanation:

Correct Answer: D

While patient's age, tumor size, location, and histological subtype all have prognostic significance for localized bone sarcomas, the response to neoadjuvant chemotherapy, as measured by the percentage of tumor necrosis in the resected specimen, is consistently one of the most powerful and independent prognostic factors. A 'good response' (typically >90-95% necrosis) is strongly associated with improved event-free and overall survival. This is a key 'Nevin Insight' into evaluating the efficacy of systemic therapy. The other factors are important, but chemotherapy response integrates the biological aggressiveness of the tumor with the effectiveness of treatment.

Question 7:

A 25-year-old male with a 4 cm deep-seated fibrosarcoma of the forearm has a biopsy revealing high-grade features (G3). Staging studies are negative for regional lymph nodes (N0) and distant metastases (M0). According to the 8th edition UICC staging system for soft tissue sarcomas, what is the overall Stage Group?

• A: Stage IA
• B: Stage IB
• C: Stage IIA
• D: Stage IIB
• E: Stage III

Explanation:

Correct Answer: D

Let's break down the UICC 8th edition staging for soft tissue sarcomas of the extremity/trunk:
- T-stage: Tumor is 4 cm, so T1 (≤ 5 cm).
- N-stage: N0 (no regional lymph node metastases).
- M-stage: M0 (no distant metastases).
- G-stage: G3 (high grade).

Now, mapping to Stage Groups:
- Stage I: G1/G2 (low/intermediate grade), T1/T2, N0, M0
- Stage II: G3 (high grade), T1, N0, M0 OR G1/G2, T3/T4, N0, M0
- Stage III: G3, T2/T3/T4, N0, M0 OR any G, any T, N1, M0
- Stage IV: Any G, any T, any N, M1

For a G3T1N0M0, the overall stage group is IIB. (Stage IIA would be G1/G2, T3/T4, N0, M0 or G3, T1, N0, M0 if G1/G2 was allowed for T1, but G3 takes precedence for IIB).

Question 8:

Which of the following factors is considered the most critical independent prognostic indicator for survival in patients with localized high-grade soft tissue sarcoma of the extremity?

• A: Patient age at diagnosis
• B: Tumor size
• C: Histological subtype
• D: Deep versus superficial location
• E: Achieving negative surgical margins (R0 resection)

Explanation:

Correct Answer: E

While tumor size, grade, depth, and histological subtype are all important prognostic factors, achieving negative surgical margins (R0 resection) is arguably the most critical independent prognostic indicator for local control and, by extension, survival in patients with localized high-grade soft tissue sarcomas. Local recurrence significantly increases the risk of distant metastasis and complicates subsequent treatment. The inability to achieve R0 resection (i.e., R1 or R2 resection) is a strong negative prognostic factor. All other options influence prognosis but are often considered in conjunction with or secondary to the achievement of complete local excision.

Question 9:

Which of the following is considered the primary 'oncological' function of neoadjuvant (preoperative) chemotherapy in the treatment of high-grade osteosarcoma?

• A: To reduce the size of the tumor to facilitate limb-salvage surgery.
• B: To evaluate the tumor's sensitivity to chemotherapy for postoperative regimen adjustment.
• C: To treat micrometastatic disease not detectable by conventional imaging.
• D: To alleviate pain and improve functional status prior to surgery.
• E: To sterilize the tumor margins to prevent local recurrence.

Explanation:

Correct Answer: C

While neoadjuvant chemotherapy can reduce tumor size (facilitating limb salvage) and alleviate pain, its primary oncological function in high-grade osteosarcoma is to treat micrometastatic disease that is presumed to be present at diagnosis, even if not detectable on imaging. Osteosarcoma has a high propensity for early systemic spread. Preoperative chemotherapy aims to eradicate these micrometastases, thereby improving overall survival. Evaluating tumor sensitivity (pathological response) is a crucial secondary benefit, as it guides adjuvant therapy. Sterilizing tumor margins is an indirect benefit if the tumor shrinks, but achieving clear surgical margins remains paramount, and chemotherapy doesn't guarantee margin sterility.

Question 10:

What is the primary significance of a biopsy tract in the surgical management of musculoskeletal sarcomas?

• A: It determines the appropriate type of systemic chemotherapy.
• B: It is the preferred site for placement of drains after definitive surgery.
• C: It must be completely excised en bloc with the primary tumor during definitive surgery.
• D: It is a reliable indicator of tumor grade.
• E: It is often left open to allow for subsequent radiation therapy.

Explanation:

Correct Answer: C

The biopsy tract (the path created by the biopsy needle or incision) is considered to be potentially contaminated with tumor cells. Therefore, for proper oncologic management and to minimize the risk of local recurrence, the biopsy tract must be completely excised en bloc with the primary tumor during definitive surgery. This ensures that any 'seeded' tumor cells are removed. Failing to do so can lead to local recurrence along the tract. It does not determine chemotherapy, is not preferred for drains, is not a reliable indicator of tumor grade, and is not left open for radiation.

Question 11:

A 45-year-old male presents to the emergency department after a high-energy motor vehicle accident. He has a comminuted pelvic ring injury involving the pubic symphysis and right sacroiliac joint, classified as an APC III. On initial evaluation, he is hypotensive, tachycardic, and has gross hematuria with a high-riding prostate on digital rectal examination. What is the most appropriate initial management step for his suspected urological injury after initial resuscitation?

• A: Perform a Foley catheter insertion immediately.
• B: Proceed directly to open surgical exploration for bladder repair.
• C: Obtain an intravenous pyelogram (IVP) to assess renal function.
• D: Perform a retrograde urethrogram (RUG) prior to any urethral instrumentation.
• E: Insert a suprapubic catheter if Foley catheterization is unsuccessful.

Explanation:

Correct Answer: D

The patient's presentation with a high-energy pelvic fracture, gross hematuria, and a high-riding prostate strongly suggests a posterior urethral injury. In such cases, urethral instrumentation with a Foley catheter is contraindicated until a retrograde urethrogram (RUG) has been performed to rule out or characterize the urethral injury. Attempting to insert a Foley catheter blindly can convert a partial tear into a complete tear or create a false passage, worsening the injury. If a urethral injury is confirmed and Foley insertion is not possible, a suprapubic catheter is the preferred method for bladder drainage. Open surgical exploration for bladder repair or IVP are not initial management steps for suspected urethral injury.

Question 12:

A 68-year-old male with a history of prostate cancer status post prostatectomy presents with increasing left shoulder pain and weakness for the past three months. X-rays show a lytic lesion in the proximal humerus. Laboratory tests reveal elevated serum calcium. What is the most appropriate next step in management?

• A: Initiate immediate chemotherapy.
• B: Refer for radiation therapy to the left shoulder.
• C: Biopsy the humeral lesion.
• D: Prescribe NSAIDs and physiotherapy.
• E: Perform surgical fixation with methyl methacrylate augmentation.

Explanation:

Correct Answer: C

Given the patient's history of prostate cancer and a new lytic lesion with hypercalcemia, metastatic disease to the humerus is highly suspected. While radiation and surgical fixation may be part of the treatment plan, a definitive diagnosis through biopsy is crucial to confirm metastasis and guide subsequent oncological management. Elevated serum calcium also suggests bone involvement. NSAIDs and physiotherapy are insufficient for a suspected malignancy. Immediate chemotherapy without definitive diagnosis is not standard practice.

Question 13:

A 35-year-old male presents with a T10 burst fracture after a fall from height. He has a neurological deficit corresponding to an ASIA C injury. Initial assessment reveals stable vital signs but diminished breath sounds at the lung bases. What is the most critical immediate respiratory concern related to a T10 spinal cord injury?

• A: Phrenic nerve paralysis leading to diaphragmatic dysfunction.
• B: Intercostal muscle weakness impacting effective cough and deep breathing.
• C: Bronchospasm due to sympathetic nervous system dysregulation.
• D: Acute respiratory distress syndrome (ARDS).
• E: Massive hemothorax from associated rib fractures.

Explanation:

Correct Answer: B

A T10 spinal cord injury typically spares the phrenic nerve (C3-C5), so diaphragmatic function is generally preserved. However, the intercostal muscles, innervated by T1-T11, are significantly weakened or paralyzed at this level. This compromises the patient's ability to take deep breaths and effectively clear secretions through coughing, leading to atelectasis, pneumonia, and hypoventilation. While other respiratory issues can occur, intercostal muscle weakness is the most direct and common respiratory complication of a thoracic spinal cord injury at this level. Phrenic nerve paralysis is seen with higher cervical injuries. Bronchospasm, ARDS, and hemothorax are less directly and universally linked to a T10 SCI itself in this scenario without further evidence.

Question 14:

A 22-year-old male sustains a right-sided scapular fracture and multiple concomitant rib fractures (ribs 4-8) after a motorcycle collision. He is hypotensive, tachycardic, and has paradoxical chest wall motion on the right. Auscultation reveals absent breath sounds on the right. What is the most immediate life-threatening thoracic injury that requires urgent intervention?

• A: Simple pneumothorax.
• B: Flail chest.
• C: Pulmonary contusion.
• D: Tension pneumothorax.
• E: Hemothorax.

Explanation:

Correct Answer: D

The patient's presentation with hypotension, tachycardia, absent breath sounds on the right, and paradoxical chest wall motion (suggesting flail chest) in the setting of severe trauma points to a tension pneumothorax as the most immediate life-threatening thoracic injury. Flail chest itself is a severe injury causing paradoxical motion and impaired ventilation, and pulmonary contusion causes respiratory compromise, but a tension pneumothorax rapidly compromises venous return to the heart and lung function, leading to shock. A simple pneumothorax or hemothorax might present with absent breath sounds but typically without the profound hemodynamic instability and mediastinal shift characteristic of tension pneumothorax. A tension pneumothorax requires immediate needle decompression followed by chest tube insertion.

Question 15:

A 72-year-old male presents with severe lower back pain, fever, and progressive bilateral leg weakness. He has a history of poorly controlled diabetes and a recent urinary tract infection. MRI of the lumbar spine reveals an epidural abscess extending from L2 to L4 with significant spinal cord compression. What is the most appropriate definitive management strategy?

• A: Long-term intravenous antibiotics alone.
• B: Percutaneous drainage of the abscess and oral antibiotics.
• C: Urgent surgical decompression and debridement with intravenous antibiotics.
• D: Corticosteroid administration to reduce inflammation.
• E: Brace immobilization and observation.

Explanation:

Correct Answer: C

Given the patient's progressive neurological deficits (bilateral leg weakness) and evidence of significant spinal cord compression from an epidural abscess, urgent surgical decompression and debridement are indicated to prevent irreversible neurological damage. Intravenous antibiotics are crucial but insufficient alone due to the mass effect. Percutaneous drainage may be considered for smaller, non-compressive abscesses, but with neurological compromise, surgical decompression is paramount. Corticosteroids are generally not recommended in spinal epidural abscesses as they can mask symptoms and potentially worsen infection. Brace immobilization and observation are inappropriate for a rapidly progressing neurological deficit.

Question 16:

Which of the following conditions is most likely to present with shoulder pain and Horner's syndrome due to apical lung tumor involvement?

• A: Rotator cuff tendinopathy.
• B: Adhesive capsulitis.
• C: Cervical radiculopathy (C5-C6).
• D: Pancoast tumor.
• E: Thoracic outlet syndrome.

Explanation:

Correct Answer: D

A Pancoast tumor is an apical lung tumor that can invade the brachial plexus (causing shoulder and arm pain), ribs, and sympathetic chain (leading to Horner's syndrome: ptosis, miosis, anhidrosis). While the other conditions can cause shoulder pain, only a Pancoast tumor specifically accounts for the combination of shoulder pain and Horner's syndrome in this context. Cervical radiculopathy would cause dermatomal/myotomal pain and weakness, but not Horner's syndrome. Thoracic outlet syndrome involves neurovascular compression but typically lacks Horner's syndrome.

Question 17:

A 60-year-old male undergoes an anterior lumbar interbody fusion (ALIF) at L4-L5. Postoperatively, he develops abdominal distension, absent bowel sounds, and is unable to void, requiring Foley catheterization. Which of the following is the most likely cause of his urinary retention and paralytic ileus?

• A: Damage to the femoral nerve during surgical approach.
• B: Spinal cord injury during instrumentation.
• C: Retrograde ejaculation due to superior hypogastric plexus injury.
• D: Temporary autonomic dysfunction due to surgical manipulation of the retroperitoneal structures and sympathetic plexus.
• E: Urinary tract infection (UTI) causing ileus.

Explanation:

Correct Answer: D

Anterior lumbar interbody fusion (ALIF) involves a retroperitoneal approach, requiring mobilization of great vessels and manipulation of the anterior longitudinal ligament. This manipulation can temporarily injure or irritate the sympathetic nerve fibers and the superior hypogastric plexus, leading to transient autonomic dysfunction manifesting as paralytic ileus and urinary retention. While retrograde ejaculation is a known, more specific, and often permanent complication of superior hypogastric plexus injury during ALIF in males, generalized transient autonomic dysfunction encompassing both ileus and urinary retention is a more common immediate postoperative issue. Femoral nerve injury is less common with a proper ALIF approach. Spinal cord injury is very unlikely at the lumbar level in an ALIF. A UTI can cause urinary retention, but not typically directly cause paralytic ileus concurrently as an immediate post-op complication of this type of surgery.

Question 18:

A 16-year-old female presents with progressive scoliosis, exhibiting a 55-degree thoracic curve (T5-T12). Her pulmonary function tests show a forced vital capacity (FVC) of 60% of predicted. What is the primary concern regarding her respiratory function in the long term without intervention?

• A: Increased risk of asthma attacks.
• B: Diaphragmatic paralysis.
• C: Restrictive lung disease and respiratory insufficiency.
• D: Obstructive lung disease.
• E: Development of pulmonary hypertension and cor pulmonale.

Explanation:

Correct Answer: C

Severe scoliosis, particularly thoracic curves exceeding 50-60 degrees, can significantly restrict chest wall and lung expansion. This leads to a restrictive ventilatory defect, characterized by reduced lung volumes (like FVC). Over time, this can progress to chronic respiratory insufficiency and, in severe cases, pulmonary hypertension and cor pulmonale (right heart failure due to lung disease). While pulmonary hypertension can be a late complication, restrictive lung disease is the primary and direct impact on lung function. Asthma is not directly caused by scoliosis. Diaphragmatic paralysis is unrelated. Obstructive lung disease involves airflow limitation, which is not the primary issue in scoliosis.

Question 19:

A 50-year-old male with a T6 complete spinal cord injury (SCI) develops a pounding headache, profuse sweating above the level of injury, and severe hypertension during routine bladder catheterization. What is the most likely diagnosis?

• A: Vasovagal syncope.
• B: Spinal shock.
• C: Autonomic dysreflexia.
• D: Malignant hyperthermia.
• E: Pulmonary embolism.

Explanation:

Correct Answer: C

This constellation of symptoms (pounding headache, sweating above injury, severe hypertension) in an SCI patient, especially from T6 and above, triggered by a noxious stimulus below the level of injury (bladder catheterization in this case), is classic for autonomic dysreflexia. This is a medical emergency that can lead to stroke, myocardial infarction, or seizure. Vasovagal syncope involves bradycardia and hypotension. Spinal shock is a transient physiological state immediately following SCI, characterized by flaccid paralysis and loss of reflexes. Malignant hyperthermia is a rare anesthetic complication. Pulmonary embolism has different clinical features.

Question 20:

A 30-year-old male presents after a severe fall, sustaining multiple rib fractures and a displaced sternal fracture. His chest X-ray shows a widened mediastinum and CT reveals a suspicious finding adjacent to the aorta. What is the most critical immediate concern regarding the sternal fracture?

• A: Pneumothorax.
• B: Hemothorax.
• C: Cardiac contusion.
• D: Tracheal injury.
• E: Aortic injury.

Explanation:

Correct Answer: E

While cardiac contusion is a significant concern with sternal fractures, and pneumothorax/hemothorax can occur with rib fractures, a widened mediastinum on chest X-ray in the context of high-energy trauma strongly suggests a major vascular injury, particularly to the aorta. A displaced sternal fracture, especially when combined with a widened mediastinum, increases the suspicion for an aortic injury. This is an immediate life-threatening condition requiring urgent diagnosis and intervention. Tracheal injury is possible but less likely to present with a widened mediastinum compared to aortic injury.

Question 21:

A 25-year-old male sustains a first-time anterior shoulder dislocation during a rugby match. After successful closed reduction in the emergency department, he is neurovascularly intact. He is a highly active individual and desires to return to competitive sports. What is the most appropriate initial management strategy?

• A: Immediate surgical stabilization (arthroscopic Bankart repair)
• B: Sling immobilization for 3 weeks followed by a gradual rehabilitation program
• C: Corticosteroid injection into the glenohumeral joint to reduce inflammation
• D: Aggressive range of motion and strengthening exercises initiated immediately
• E: MRI of the shoulder to confirm labral tear and then observe

Explanation:

Correct Answer: B

For a first-time anterior shoulder dislocation in a young, active patient, initial management typically involves a period of sling immobilization (usually 2-3 weeks) to allow for initial soft tissue healing, followed by a structured rehabilitation program. While young, active patients have a higher risk of recurrent dislocation, immediate surgical stabilization is generally not indicated for a first-time dislocation unless there are specific indications such as a large bony Bankart lesion, significant Hill-Sachs lesion, or concomitant rotator cuff tear in an older patient. The goal of initial non-operative management is to restore range of motion and strength while minimizing the risk of recurrence. Corticosteroid injections are not indicated for acute dislocations. Aggressive immediate range of motion can hinder soft tissue healing. An MRI is often performed after initial stabilization to assess for associated injuries (e.g., Bankart lesion, Hill-Sachs lesion, rotator cuff tears) which will guide long-term management and surgical decision-making, but it is not the immediate next step after reduction and neurovascular assessment.

Question 22:

A 10-year-old male falls from a trampoline, landing on his elbow. Radiographs show a fracture of the distal humerus that extends through the metaphysis and then obliquely through the physis, exiting into the epiphysis and involving the articular surface. Which Salter-Harris classification best describes this injury?

• A: Type I
• B: Type II
• C: Type III
• D: Type IV
• E: Type V

Explanation:

Correct Answer: D

The Salter-Harris classification system categorizes physeal (growth plate) fractures:

• Type I: Fracture through the physis only.
• Type II: Fracture through the physis and metaphysis (most common type).
• Type III: Fracture through the physis and epiphysis, involving the articular surface.
• Type IV: Fracture through the metaphysis, physis, and epiphysis, involving the articular surface.
• Type V: Crush injury to the physis.

The description of a fracture extending through the metaphysis, physis, and epiphysis (involving the articular surface) perfectly matches a Salter-Harris Type IV fracture. These fractures are intra-articular and involve the germinal cells of the physis, carrying a high risk of growth arrest and articular incongruity, often requiring anatomical reduction.

Question 23:

A 55-year-old male presents with a 3-month history of progressive right buttock pain radiating down the posterior thigh and lateral calf to the dorsum of the foot. He reports numbness in the web space between the first and second toes. On examination, he has weakness with ankle dorsiflexion and great toe extension. Which lumbar nerve root is most likely affected?

• A: L3
• B: L4
• C: L5
• D: S1
• E: S2

Explanation:

Correct Answer: C

This clinical presentation is classic for L5 radiculopathy. Key features include:

• Pain distribution: Buttock, posterior thigh, lateral calf, dorsum of the foot.
• Sensory deficit: Numbness in the web space between the first and second toes (L5 dermatome).
• Motor weakness: Ankle dorsiflexion (tibialis anterior, L4-L5), great toe extension (extensor hallucis longus, L5).

In contrast:

• L3 radiculopathy: Pain in the anterior thigh, weakness in hip flexion and knee extension.
• L4 radiculopathy: Pain in the anterior thigh, medial calf, weakness in knee extension, diminished patellar reflex.
• S1 radiculopathy: Pain in the posterior thigh, calf, plantar foot, weakness in ankle plantarflexion, diminished Achilles reflex.

Question 24:

A 40-year-old female, 3 months postpartum, presents with pain and swelling at the radial side of her dominant wrist. The pain is exacerbated by lifting her infant and by activities involving grasping and pinching. Physical examination reveals tenderness over the radial styloid and a positive Finkelstein's test (pain with ulnar deviation of the wrist while the thumb is flexed into the palm). What is the most likely diagnosis?

• A: Carpal tunnel syndrome
• B: Trigger thumb
• C: De Quervain's tenosynovitis
• D: Scaphoid fracture
• E: Ganglion cyst

Explanation:

Correct Answer: C

The patient's symptoms are classic for De Quervain's tenosynovitis, an inflammatory condition affecting the first dorsal compartment of the wrist. This compartment contains the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons. Repetitive thumb and wrist movements, common in new mothers (e.g., lifting and holding an infant), can lead to inflammation and thickening of the tendon sheath. The positive Finkelstein's test is pathognomonic for this condition. Carpal tunnel syndrome involves median nerve compression. Trigger thumb involves stenosing tenosynovitis of the flexor pollicis longus. A scaphoid fracture would typically follow acute trauma and present with different pain patterns. A ganglion cyst is a localized mass.

Question 25:

A 28-year-old collegiate soccer player sustains an acute eversion injury to his right ankle during a game. He reports immediate pain and swelling on the medial side of his ankle. Which of the following ligaments is most likely to be injured?

• A: Anterior talofibular ligament (ATFL)
• B: Calcaneofibular ligament (CFL)
• C: Posterior talofibular ligament (PTFL)
• D: Deltoid ligament complex
• E: Anterior inferior tibiofibular ligament (AITFL)

Explanation:

Correct Answer: D

An eversion ankle injury (where the foot rolls outward) places stress on the medial side of the ankle. The deltoid ligament complex is a strong, fan-shaped ligament on the medial aspect of the ankle that primarily resists eversion forces. Therefore, it is the most likely ligament to be injured in an eversion sprain. The ATFL, CFL, and PTFL are components of the lateral collateral ligament complex and are injured in inversion sprains. The AITFL is part of the syndesmosis and is injured in high ankle sprains, typically involving external rotation of the talus.

Question 26:

A 70-year-old female with severe osteoporosis is prescribed denosumab. What is the primary mechanism of action of this medication in treating osteoporosis?

• A: Increases osteoblast activity and bone formation
• B: Stimulates parathyroid hormone release to increase calcium levels
• C: Binds directly to hydroxyapatite crystals on the bone surface
• D: Monoclonal antibody that targets and inhibits RANKL
• E: Increases intestinal absorption of calcium and phosphate

Explanation:

Correct Answer: D

Denosumab is a human monoclonal antibody that specifically targets and inhibits Receptor Activator of Nuclear factor Kappa-Β Ligand (RANKL). RANKL is a key mediator of osteoclast formation, function, and survival. By binding to RANKL, denosumab prevents it from activating its receptor (RANK) on pre-osteoclasts and mature osteoclasts. This inhibition leads to a decrease in osteoclast numbers and activity, thereby reducing bone resorption and increasing bone mineral density. This mechanism is distinct from bisphosphonates (which bind to hydroxyapatite) and other osteoporosis medications.

Question 27:

Which of the following muscles is the primary hip abductor and is crucial for maintaining pelvic stability during the single-leg stance phase of gait?

• A: Gluteus maximus
• B: Iliopsoas
• C: Rectus femoris
• D: Gluteus medius
• E: Adductor longus

Explanation:

Correct Answer: D

The gluteus medius is the primary hip abductor and plays a critical role in stabilizing the pelvis during the single-leg stance phase of gait. Along with the gluteus minimus, it prevents the contralateral hip from dropping (a phenomenon known as the Trendelenburg sign or gait). The gluteus maximus is a powerful hip extensor. The iliopsoas is the primary hip flexor. The rectus femoris is a hip flexor and knee extensor. The adductor longus is a hip adductor.

Question 28:

A 16-year-old male presents with a 6-month history of localized pain in his proximal tibia, which is worse at night and consistently relieved by over-the-counter NSAIDs. Physical examination reveals localized tenderness. Radiographs show a small, lucent nidus (less than 1.5 cm) surrounded by a dense sclerotic reaction in the tibial cortex. What is the most likely diagnosis?

• A: Osteosarcoma
• B: Ewing's sarcoma
• C: Osteoid osteoma
• D: Enchondroma
• E: Fibrous dysplasia

Explanation:

Correct Answer: C

The clinical presentation of localized pain, worse at night, and classically relieved by NSAIDs (due to prostaglandin production within the nidus) in an adolescent, combined with radiographic findings of a small lucent nidus surrounded by dense cortical sclerosis, is pathognomonic for an osteoid osteoma. This is a benign bone tumor. Osteosarcoma and Ewing's sarcoma are malignant tumors with more aggressive radiographic features and different pain patterns. Enchondromas are typically asymptomatic and found in the medullary cavity of small bones. Fibrous dysplasia has a different radiographic appearance and clinical course.

Question 29:

Which of the following factors is considered the MOST detrimental to fracture healing, significantly increasing the risk of non-union?

• A: Patient age over 60 years
• B: Presence of diabetes mellitus
• C: Smoking history
• D: Severe fracture comminution
• E: Inadequate mechanical stability at the fracture site

Explanation:

Correct Answer: E

While all listed options can negatively impact fracture healing, inadequate mechanical stability at the fracture site is considered the MOST detrimental factor leading to non-union. Bone healing requires a stable environment to progress through its stages. Excessive motion at the fracture site (micromotion beyond an optimal range) disrupts callus formation, prevents vascular ingrowth, and can lead to the formation of fibrous tissue or pseudarthrosis instead of bone. Patient age, diabetes, smoking, and severe comminution are significant risk factors, but they often exert their effect by impairing the biological capacity for healing, which is then exacerbated by poor mechanical conditions.

Question 30:

A newborn is diagnosed with congenital talipes equinovarus (clubfoot) characterized by ankle equinus, hindfoot varus, forefoot adduction, and internal rotation. The foot is rigid and cannot be passively corrected. Which of the following is the most appropriate initial treatment?

• A: Immediate surgical correction with soft tissue release
• B: Serial casting using the Ponseti method
• C: Custom orthotics and bracing for 12 months
• D: Intensive physical therapy and stretching exercises
• E: Observation with serial radiographs to monitor progression

Explanation:

Correct Answer: B

For congenital talipes equinovarus (clubfoot), the Ponseti method of serial casting is the gold standard and most appropriate initial treatment. This non-surgical technique involves a series of gentle manipulations and plaster casts applied weekly over several weeks, followed by a percutaneous Achilles tenotomy in most cases, and then maintenance with a foot abduction brace. The Ponseti method has a high success rate in achieving correction and avoiding extensive surgery. Immediate surgical correction is typically reserved for cases that fail Ponseti treatment or are diagnosed later in childhood. Custom orthotics and physical therapy alone are insufficient for rigid clubfoot. Observation is inappropriate for a condition that requires active correction.

Question 31:

A 38-year-old male presents to the emergency department after a high-speed motor vehicle collision. He was wearing a lap belt only. On examination, he has significant abdominal bruising and tenderness. Neurological exam reveals mild weakness in bilateral lower extremities (4/5) and a sensory deficit below the umbilicus. Imaging reveals a T12 fracture with disruption of the posterior ligamentous complex, involving the vertebral body, pedicles, and lamina, with a horizontal fracture line through all three columns. There is minimal kyphosis and no significant canal compromise. Which of the following is the most likely fracture pattern and the most appropriate management?

• A: Burst fracture; conservative management with bracing.
• B: Compression fracture; immediate posterior fusion.
• C: Flexion-distraction (Chance-type) fracture; surgical stabilization with posterior instrumentation.
• D: Fracture-dislocation; anterior decompression and fusion.
• E: Rotational injury; trial of halo immobilization.

Explanation:

Correct Answer: C

Rationale:

The patient's history of a lap belt-only injury in a high-speed collision, combined with abdominal bruising, is highly suggestive of a flexion-distraction injury, often referred to as a Chance-type fracture. The description of a horizontal fracture line through all three columns (vertebral body, pedicles, lamina) and disruption of the posterior ligamentous complex confirms this pattern. These injuries are inherently unstable due to the failure of both anterior and posterior tension bands. The presence of even mild neurological deficit further mandates surgical intervention.

Why other options are incorrect:

• A) Burst fracture; conservative management with bracing: A burst fracture typically results from an axial load and involves comminution of the vertebral body with retropulsion into the canal. While it can cause neurological deficits, the described mechanism (lap belt) and horizontal fracture through all columns are not characteristic of a pure burst fracture. Conservative management is generally not appropriate for unstable flexion-distraction injuries, especially with neurological deficits.
• B) Compression fracture; immediate posterior fusion: A compression fracture involves failure of the anterior column under axial load, typically without significant posterior element involvement or instability. The described injury is far more severe and unstable than a simple compression fracture.
• D) Fracture-dislocation; anterior decompression and fusion: While fracture-dislocations are highly unstable, the specific description of a horizontal fracture through all three columns is more indicative of a flexion-distraction injury. Anterior decompression is typically reserved for significant anterior canal compromise, which is not emphasized here, and posterior stabilization is usually the primary approach for flexion-distraction injuries.
• E) Rotational injury; trial of halo immobilization: Rotational injuries involve significant torsional forces and often present with severe instability. While unstable, halo immobilization is generally not effective for thoracolumbar fractures and is primarily used for certain cervical spine injuries.

Question 32:

A 72-year-old female presents after a low-energy fall, landing on her head. She complains of severe neck pain. Radiographs show a fracture through the base of the odontoid process, extending into the body of C2, with significant anterior displacement of the odontoid fragment relative to C2. She has no neurological deficits. Given her age and fracture pattern, what is the most appropriate definitive management strategy?

• A: Halo vest immobilization for 12 weeks.
• B: Anterior odontoid screw fixation.
• C: Posterior C1-C2 fusion.
• D: Soft cervical collar and observation.
• E: Anterior cervical discectomy and fusion (ACDF) at C2-C3.

Explanation:

Correct Answer: C

Rationale:

The patient has a Type II odontoid fracture (fracture at the base of the odontoid process). In elderly patients, Type II odontoid fractures have a high rate of non-union with conservative management (e.g., halo vest) due to poor bone quality, decreased healing potential, and difficulty tolerating prolonged immobilization. Anterior odontoid screw fixation is an option for Type II fractures, but its success rate decreases significantly with age, osteoporosis, and significant displacement, making it less reliable in this 72-year-old patient. Posterior C1-C2 fusion (e.g., with C1 lateral mass and C2 pedicle screws) provides rigid fixation and a high fusion rate, making it the most appropriate definitive management for an unstable Type II odontoid fracture in an elderly patient, especially with significant displacement.

Why other options are incorrect:

• A) Halo vest immobilization for 12 weeks: While a halo vest is a common treatment for Type II odontoid fractures in younger patients, it has a high non-union rate (up to 80%) in the elderly due to poor bone quality and intolerance.
• B) Anterior odontoid screw fixation: This technique is best for Type II fractures with minimal displacement and good bone quality, typically in younger patients. Its success rate is significantly lower in the elderly with osteoporosis and significant displacement.
• D) Soft cervical collar and observation: This is completely inadequate for an unstable Type II odontoid fracture and would lead to non-union and potential neurological compromise.
• E) Anterior cervical discectomy and fusion (ACDF) at C2-C3: ACDF is used for disc herniations or degenerative conditions at lower cervical levels. It is not indicated for an odontoid fracture, which involves C1 and C2.

Question 33:

A 25-year-old male sustains a C5 burst fracture with significant retropulsion into the spinal canal after a diving accident. On initial assessment, he has complete paralysis below the C5 level, including absent motor and sensory function in the bilateral upper and lower extremities, and absent sacral sparing. Which ASIA Impairment Scale (AIS) grade best describes his neurological status?

• A: AIS A
• B: AIS B
• C: AIS C
• D: AIS D
• E: AIS E

Explanation:

Correct Answer: A

Rationale:

The ASIA Impairment Scale (AIS) is used to classify the severity of spinal cord injury. AIS A is defined as a complete spinal cord injury, characterized by no motor or sensory function preserved in the sacral segments S4-S5. The patient's description of 'complete paralysis below the C5 level, including absent motor and sensory function in the bilateral upper and lower extremities, and absent sacral sparing' directly corresponds to the definition of AIS A.

Why other options are incorrect:

• B) AIS B: Incomplete injury with sensory but not motor function preserved below the neurological level and extending through the sacral segments S4-S5.
• C) AIS C: Incomplete injury with motor function preserved below the neurological level, and more than half of key muscles below the neurological level have a muscle grade less than 3.
• D) AIS D: Incomplete injury with motor function preserved below the neurological level, and at least half of key muscles below the neurological level have a muscle grade of 3 or greater.
• E) AIS E: Normal motor and sensory function.

Question 34:

A 45-year-old male presents after a fall from a ladder, sustaining a T10 compression fracture. Imaging reveals a wedge compression fracture with 30% loss of anterior vertebral body height, no posterior wall involvement, and an intact posterior ligamentous complex. Neurological examination is completely normal. Using the Thoracolumbar Injury Classification System (TLICS), what is the most appropriate management recommendation?

• A: Surgical stabilization due to high TLICS score.
• B: Conservative management with bracing and early mobilization.
• C: Anterior decompression and fusion.
• D: Vertebroplasty or kyphoplasty.
• E: Immediate halo vest immobilization.

Explanation:

Correct Answer: B

Rationale:

The Thoracolumbar Injury Classification System (TLICS) assigns points based on three main categories: morphology of the injury, integrity of the posterior ligamentous complex (PLC), and neurological status. A score of 3 or less typically indicates non-operative management, while a score of 5 or more suggests surgical intervention. A score of 4 is equivocal and often depends on surgeon preference or other patient factors.

• Morphology: Compression fracture = 1 point.
• Posterior Ligamentous Complex (PLC) Integrity: Intact = 0 points.
• Neurological Status: Intact = 0 points.

Total TLICS score = 1 + 0 + 0 = 1 point. A score of 1 strongly indicates conservative management with bracing and early mobilization.

Why other options are incorrect:

• A) Surgical stabilization due to high TLICS score: The TLICS score is 1, which is low and indicates non-operative management.
• C) Anterior decompression and fusion: This is indicated for significant anterior canal compromise, which is not present here, or for specific fracture patterns not seen in a simple compression fracture.
• D) Vertebroplasty or kyphoplasty: These procedures are primarily for pain relief in osteoporotic compression fractures, not typically for traumatic compression fractures in a 45-year-old, especially when conservative management is indicated by TLICS.
• E) Immediate halo vest immobilization: Halo vests are used for cervical spine injuries, not thoracolumbar fractures.

Question 35:

A 10-year-old boy is involved in a bicycle accident, sustaining a high-energy injury to his neck. He presents with transient quadriparesis that resolved within minutes. Initial plain radiographs and CT scan of the cervical spine are normal. Despite the resolution of symptoms, what is the most appropriate next diagnostic step?

• A: Reassure the parents and discharge with a soft collar.
• B: Order a flexion-extension radiograph of the cervical spine.
• C: Perform an MRI of the entire spine.
• D: Administer high-dose corticosteroids.
• E: Refer for immediate surgical exploration.

Explanation:

Correct Answer: C

Rationale:

This is a classic presentation of Spinal Cord Injury Without Radiographic Abnormality (SCIWORA). SCIWORA is more common in children due to the greater elasticity of their spinal columns, which allows significant stretching of the spinal cord without bony injury. Even if neurological symptoms are transient, there can be underlying spinal cord edema, hemorrhage, or ligamentous injury that is not visible on plain radiographs or CT. An MRI of the entire spine is the most appropriate next diagnostic step as it is highly sensitive for detecting soft tissue injuries, spinal cord pathology (edema, contusion, hemorrhage), and ligamentous disruption, which are crucial for guiding further management and prognosis.

Why other options are incorrect:

• A) Reassure the parents and discharge with a soft collar: This is inappropriate and dangerous. SCIWORA can have delayed neurological deterioration, and underlying pathology needs to be identified.
• B) Order a flexion-extension radiograph of the cervical spine: While useful for assessing stability, these should be performed with caution and under physician supervision in a child with a history of neurological symptoms, and only after ruling out unstable bony injury. MRI is superior for soft tissue and cord evaluation in this context.
• D) Administer high-dose corticosteroids: The use of high-dose corticosteroids for acute spinal cord injury is controversial and not routinely recommended, especially after transient symptoms.
• E) Refer for immediate surgical exploration: Surgical exploration is not indicated without clear evidence of a surgically correctable lesion (e.g., epidural hematoma, persistent compression) identified on MRI.

Question 36:

A 68-year-old male presents with severe low back pain and bilateral lower extremity weakness (3/5) that developed acutely over 24 hours. He has a history of intravenous drug use and recent skin infection. On examination, he is febrile (39.2°C) and has tenderness over the L4-L5 spinous processes. Lab tests show leukocytosis and elevated ESR/CRP. What is the most appropriate urgent management strategy?

• A: Conservative management with bed rest and oral antibiotics.
• B: Lumbar puncture for CSF analysis.
• C: Immediate MRI of the lumbar spine and empiric broad-spectrum intravenous antibiotics.
• D: Plain radiographs of the lumbar spine and blood cultures.
• E: Urgent neurosurgical consultation for laminectomy without prior imaging.

Explanation:

Correct Answer: C

Rationale:

This patient presents with a classic picture of acute spinal epidural abscess (SEA) with progressive neurological deficit (bilateral lower extremity weakness). Risk factors include IV drug use and recent infection. SEA is an orthopedic and neurosurgical emergency. The most appropriate urgent management involves:

1. Immediate MRI of the lumbar spine: This is the gold standard for diagnosing SEA, delineating its extent, and assessing for spinal cord or cauda equina compression. It is crucial for surgical planning.
2. Empiric broad-spectrum intravenous antibiotics: These should be initiated immediately after blood cultures are drawn, without waiting for MRI or culture results, to cover common pathogens (e.g., Staphylococcus aureus).

Why other options are incorrect:

• A) Conservative management with bed rest and oral antibiotics: This is inadequate and dangerous for a patient with progressive neurological deficits due to SEA. Oral antibiotics are insufficient, and bed rest does not address the underlying compression.
• B) Lumbar puncture for CSF analysis: Lumbar puncture is generally contraindicated in suspected SEA due to the risk of spreading the infection into the CSF or causing neurological deterioration from changes in intraspinal pressure.
• D) Plain radiographs of the lumbar spine and blood cultures: Plain radiographs are often normal in early SEA and will not show the abscess or neural compression. While blood cultures are essential, waiting for plain films is a delay, and they are insufficient for diagnosis.
• E) Urgent neurosurgical consultation for laminectomy without prior imaging: While surgical decompression is often necessary, it must be guided by precise localization and extent of the abscess, which is provided by MRI. Operating without imaging is not standard practice.

Question 37:

A 28-year-old male sustains a high-energy trauma resulting in a C1 burst fracture (Jefferson fracture). CT scan reveals bilateral lateral mass displacement of C1 totaling 8 mm. He has no neurological deficits. What is the most appropriate initial management?

• A: Soft cervical collar and observation.
• B: Halo vest immobilization.
• C: C1-C2 posterior fusion.
• D: Occipitocervical fusion.
• E: Anterior C1-C2 transarticular screw fixation.

Explanation:

Correct Answer: B

Rationale:

A Jefferson fracture is a burst fracture of the C1 ring, typically caused by an axial load. The key to management is assessing the stability of the transverse atlantal ligament (TAL). If the sum of the lateral displacement of the C1 lateral masses on an open-mouth odontoid view (or CT scan) is greater than 7 mm, it indicates rupture of the TAL, rendering the C1 ring unstable. In this case, a total displacement of 8 mm signifies TAL rupture and instability. Given no neurological deficits, halo vest immobilization is the most appropriate initial management for unstable C1 fractures with TAL rupture. It provides rigid external stabilization, allowing for ligamentous healing.

Why other options are incorrect:

• A) Soft cervical collar and observation: This is inadequate for an unstable C1 fracture with TAL rupture and would risk further instability and potential neurological injury.
• C) C1-C2 posterior fusion: This is a surgical option for unstable C1 fractures, particularly if halo vest fails or is contraindicated, or if there is associated C2 instability. However, halo vest is often the first-line for isolated unstable C1 fractures without neurological deficit.
• D) Occipitocervical fusion: This is a more extensive fusion, typically reserved for highly unstable upper cervical injuries involving the occiput, C1, and C2, or for failed C1-C2 fusions. It is overkill for an isolated unstable C1 fracture.
• E) Anterior C1-C2 transarticular screw fixation: This is not a standard approach for C1 fractures. C1-C2 fixation is typically performed posteriorly.

Question 38:

A 55-year-old male presents with chronic, progressive low back pain and bilateral leg numbness and weakness, worse with standing and walking, and relieved by sitting or leaning forward. MRI reveals severe degenerative changes at L4-L5 with hypertrophy of the ligamentum flavum and facet joints, causing significant central canal stenosis. He has failed extensive conservative management. What is the most appropriate surgical intervention?

• A: Microdiscectomy.
• B: Laminectomy alone without fusion.
• C: Anterior lumbar interbody fusion (ALIF) alone.
• D: Posterior decompression (laminectomy) and instrumented fusion.
• E: Vertebroplasty.

Explanation:

Correct Answer: D

Rationale:

The patient's symptoms (neurogenic claudication, relief with flexion) and MRI findings (severe central canal stenosis due to ligamentum flavum and facet hypertrophy) are classic for lumbar spinal stenosis. Given the failure of conservative management and the presence of neurological deficits, surgical intervention is indicated. For severe central canal stenosis, posterior decompression (laminectomy) is necessary to relieve pressure on the neural elements. However, performing a laminectomy alone can destabilize the spine, especially in the presence of significant degenerative changes and facet hypertrophy, potentially leading to iatrogenic instability or spondylolisthesis. Therefore, posterior decompression combined with instrumented fusion (e.g., posterior lumbar interbody fusion - PLIF, or transforaminal lumbar interbody fusion - TLIF) is often the most appropriate approach to provide both decompression and long-term stability.

Why other options are incorrect:

• A) Microdiscectomy: This procedure is primarily for disc herniations causing nerve root compression, not for central canal stenosis due to bony and ligamentous hypertrophy.
• B) Laminectomy alone without fusion: While it provides decompression, it carries a risk of iatrogenic instability, especially in a degenerated spine. Fusion is often added to maintain stability.
• C) Anterior lumbar interbody fusion (ALIF) alone: ALIF provides indirect decompression and fusion, but it may not adequately address severe posterior element hypertrophy causing central stenosis. It is often combined with posterior decompression if needed.
• E) Vertebroplasty: This procedure is for vertebral compression fractures, not for lumbar spinal stenosis.

Question 39:

A 4-year-old child presents with a history of a fall from a swing set. He has severe neck pain and is holding his head in a 'cock-robin' position (head tilted to one side, chin rotated to the opposite side). Neurological examination is normal. Plain radiographs show rotation of C1 on C2. What is the most likely diagnosis?

• A: Cervical disc herniation.
• B: Atlantoaxial rotatory subluxation (AARS).
• C: Odontoid fracture.
• D: Congenital muscular torticollis.
• E: Spinal epidural hematoma.

Explanation:

Correct Answer: B

Rationale:

The classic presentation of a child with a 'cock-robin' head posture (head tilted to one side, chin rotated to the opposite side) following trauma, combined with radiographic evidence of C1-C2 rotation, is highly suggestive of atlantoaxial rotatory subluxation (AARS). This condition is more common in children due to increased ligamentous laxity and the horizontal orientation of the facet joints. It can be traumatic or non-traumatic (e.g., Grisel's syndrome associated with pharyngitis).

Why other options are incorrect:

• A) Cervical disc herniation: While possible in children, it typically presents with radicular pain and neurological deficits, and less commonly with the 'cock-robin' posture.
• C) Odontoid fracture: An odontoid fracture would cause severe neck pain but typically doesn't present with the specific 'cock-robin' posture unless there's significant C1-C2 instability, which would be evident on radiographs as displacement, not just rotation.
• D) Congenital muscular torticollis: This is a developmental condition presenting in infancy, usually without acute trauma, and is due to sternocleidomastoid muscle shortening, not C1-C2 subluxation.
• E) Spinal epidural hematoma: This would cause acute neurological deficits and severe pain, but the 'cock-robin' posture is not its characteristic presentation.

Question 40:

A 60-year-old male with a history of ankylosing spondylitis presents after a minor fall, complaining of severe, acute onset back pain. He has no neurological deficits. Given his underlying condition, what is the most critical diagnostic imaging study to perform, even if plain radiographs appear normal or minimally changed?

• A: Bone scan (technetium-99m).
• B: Flexion-extension radiographs.
• C: MRI of the entire spine.
• D: CT scan of the affected spinal segment.
• E: Electromyography (EMG).

Explanation:

Correct Answer: C

Rationale:

Patients with ankylosing spondylitis (AS) have a rigid, osteoporotic spine (bamboo spine) that is highly susceptible to fracture, even after minor trauma. These fractures often occur through the fused segments and can be highly unstable, even if minimally displaced on plain radiographs. There is a high risk of neurological injury, even with seemingly benign fractures. Therefore, an MRI of the entire spine is the most critical diagnostic imaging study. It can detect subtle fractures, assess for spinal cord edema or hemorrhage, and identify epidural hematomas, which are common and can cause delayed neurological deficits in AS patients. Plain radiographs and CT scans may underestimate the severity of the injury or miss soft tissue/cord involvement.

Why other options are incorrect:

• A) Bone scan (technetium-99m): While sensitive for metabolic activity, it is not specific for fracture type or stability and does not provide detail on neural elements or soft tissue.
• B) Flexion-extension radiographs: These are contraindicated in the acute setting of suspected spinal fracture in AS patients due to the high risk of catastrophic neurological injury from an unstable spine.
• D) CT scan of the affected spinal segment: CT is excellent for bony detail but less sensitive than MRI for detecting spinal cord injury, ligamentous disruption, or epidural hematoma, which are critical concerns in AS fractures.
• E) Electromyography (EMG): EMG assesses nerve function but is not an acute diagnostic imaging study for fracture or spinal cord injury.

Question 41:

A 42-year-old male sustains a high-energy pelvic injury after being crushed between two vehicles. He has a Denis Zone III sacral fracture with significant displacement and a concomitant open book pelvic ring injury. On examination, he has absent sensation in the S2-S5 dermatomes and poor rectal tone. What is the most critical aspect of his surgical management for the sacral fracture?

• A: Immediate closed reduction and external fixation of the pelvic ring.
• B: Decompression of the cauda equina and nerve roots.
• C: Sacral laminectomy alone for pain relief.
• D: Non-operative management with bed rest.
• E: Anterior plating of the sacrum.

Explanation:

Correct Answer: B

Rationale:

A Denis Zone III sacral fracture involves the sacral foramen and the central sacral canal, carrying the highest risk of neurological injury, particularly to the cauda equina and sacral nerve roots. The patient's presentation with absent S2-S5 sensation and poor rectal tone indicates significant cauda equina injury. In such cases, the most critical aspect of surgical management is urgent decompression of the cauda equina and nerve roots to prevent permanent neurological deficits. This typically involves a posterior approach to decompress the neural elements, often combined with stabilization of the sacral and pelvic ring fracture.

Why other options are incorrect:

• A) Immediate closed reduction and external fixation of the pelvic ring: While pelvic ring stabilization is crucial for the open book injury and overall stability, it does not directly address the neural compression from the sacral fracture. Decompression takes precedence when neurological deficits are present.
• C) Sacral laminectomy alone for pain relief: Laminectomy is a decompression technique, but simply for 'pain relief' underestimates the urgency and necessity of addressing the neurological deficit. It's part of the decompression, not the sole goal.
• D) Non-operative management with bed rest: This is contraindicated for unstable sacral fractures with neurological deficits and would lead to permanent neurological impairment.
• E) Anterior plating of the sacrum: Anterior approaches to the sacrum are complex and generally not used for direct neural decompression in the setting of a Denis Zone III fracture with cauda equina injury. Decompression is typically posterior.

Question 42:

A 45-year-old male presents with acute onset of right shoulder pain and weakness after attempting to lift a heavy object. On examination, he has significant weakness in external rotation and abduction. Deltoid function is intact. Radiographs are normal. Which of the following is the most likely diagnosis?

• A: Subscapularis tear
• B: Infraspinatus tear
• C: Supraspinatus tear
• D: Axillary nerve palsy
• E: Long head of biceps rupture

Explanation:

Correct Answer: B

The patient presents with acute shoulder pain and weakness, specifically in external rotation and abduction. While the supraspinatus initiates abduction, the infraspinatus is the primary external rotator. Given the intact deltoid (ruling out axillary nerve palsy) and significant weakness in external rotation, a tear of the infraspinatus is the most likely diagnosis. Subscapularis tears primarily affect internal rotation, and long head of biceps rupture typically presents with a 'Popeye' deformity and weakness in elbow flexion/supination, not primarily shoulder abduction/external rotation.

Question 43:

A 62-year-old female with a history of osteoporosis sustains a displaced intra-articular fracture of the distal radius (AO type C3). She is active and has good functional demands. What is the most appropriate definitive management strategy?

• A: Closed reduction and sugar tong splint immobilization
• B: Percutaneous pinning
• C: External fixation with adjunctive K-wires
• D: Open reduction and internal fixation with a volar locking plate
• E: Arthroscopic-assisted reduction and fixation

Explanation:

Correct Answer: D

For a displaced intra-articular distal radius fracture (AO type C3) in an active patient with good functional demands, open reduction and internal fixation with a volar locking plate is considered the gold standard. This approach allows for stable anatomical reduction, early range of motion, and addresses the challenge of comminution and osteopenia often seen in C3 fractures. Closed reduction and splinting is inadequate for displaced intra-articular fractures. Percutaneous pinning or external fixation alone may not provide sufficient stability or allow for direct visualization and reduction of articular fragments, especially in complex, comminuted patterns.

Question 44:

A 7-year-old boy presents with a 3-week history of right hip pain and a limp. He denies trauma. On examination, he has decreased internal rotation and abduction of the right hip. Radiographs show increased density of the right femoral epiphysis and a flattened appearance. What is the most likely diagnosis?

• A: Septic arthritis of the hip
• B: Transient synovitis of the hip
• C: Slipped capital femoral epiphysis (SCFE)
• D: Legg-Calvé-Perthes disease
• E: Developmental dysplasia of the hip (DDH)

Explanation:

Correct Answer: D

The clinical presentation of a 7-year-old boy with hip pain, limp, and decreased hip motion (especially internal rotation and abduction), combined with radiographic findings of increased density (sclerosis) and flattening (fragmentation) of the femoral epiphysis, is classic for Legg-Calvé-Perthes disease. Septic arthritis would present acutely with systemic signs and extreme pain, transient synovitis is usually self-limiting with normal radiographs after a few days, SCFE typically occurs in older, often obese adolescents, and DDH is usually diagnosed in infancy or early childhood.

Question 45:

A 32-year-old competitive runner presents with chronic pain along the medial aspect of her left foot, exacerbated by activity. Examination reveals tenderness just distal to the medial malleolus, reproducible pain with resisted plantarflexion and inversion, and a pes planus foot posture. What is the most likely diagnosis?

• A: Plantar fasciitis
• B: Achilles tendinopathy
• C: Tarsal tunnel syndrome
• D: Posterior tibial tendon dysfunction (PTTD)
• E: Navicular stress fracture

Explanation:

Correct Answer: D

The symptoms of chronic medial foot pain exacerbated by activity, tenderness distal to the medial malleolus, pain with resisted plantarflexion and inversion, and an associated pes planus deformity are highly suggestive of Posterior Tibial Tendon Dysfunction (PTTD). PTTD is a progressive condition that can lead to adult-acquired flatfoot. Plantar fasciitis causes heel pain. Achilles tendinopathy causes pain in the posterior ankle/heel. Tarsal tunnel syndrome involves nerve compression, often with burning/tingling. A navicular stress fracture would typically present with localized dorsal midfoot pain and often swelling.

Question 46:

A 70-year-old male undergoes a total hip arthroplasty for severe osteoarthritis. Postoperatively, he develops a foot drop and diminished sensation over the dorsum of the foot and lateral leg. Which nerve injury is most likely responsible?

• A: Femoral nerve
• B: Obturator nerve
• C: Sciatic nerve (common peroneal division)
• D: Sciatic nerve (tibial division)
• E: Superior gluteal nerve

Explanation:

Correct Answer: C

Foot drop and diminished sensation over the dorsum of the foot and lateral leg are classic signs of common peroneal nerve palsy. The common peroneal nerve is a division of the sciatic nerve and is particularly vulnerable during total hip arthroplasty due to traction, direct trauma, or compression, especially in cases of leg lengthening or revision surgery. Femoral nerve injury affects quadriceps strength, obturator nerve injury affects adduction, and tibial nerve injury affects plantarflexion and sensation over the sole of the foot. Superior gluteal nerve injury would affect abductor function.

Question 47:

Which of the following describes the most common mechanism of injury for an anterior cruciate ligament (ACL) rupture?

• A: Direct blow to the anterior tibia with the knee in flexion
• B: Hyperextension injury with a varus force
• C: Non-contact deceleration with a rotational (valgus and external rotation) force
• D: Posteriorly directed force to the proximal tibia with the knee flexed
• E: Landing from a jump with the knee in full extension

Explanation:

Correct Answer: C

The most common mechanism for ACL rupture is a non-contact injury involving deceleration, cutting, or pivoting maneuvers, typically with the knee in slight flexion, valgus, and external rotation of the tibia on the femur. This creates significant tension on the ACL. A direct blow to the anterior tibia (dashboard injury) can cause a posterior cruciate ligament (PCL) injury. Hyperextension with varus force might stress the posterolateral corner, while a direct posterior force to the tibia causes PCL injury. Landing in full extension is less common than dynamic valgus loading for ACL rupture.

Question 48:

A 28-year-old male sustains an open Schatzker type VI tibial plateau fracture with significant soft tissue compromise. After initial debridement and external fixation, what is the optimal timing for definitive internal fixation?

• A: Immediately, within 6 hours of injury
• B: Within 24-48 hours, following soft tissue resuscitation
• C: Between 5-10 days, once the 'wrinkle sign' returns
• D: At 3 weeks, after complete soft tissue healing
• E: Only after initial external fixator removal and full weight-bearing

Explanation:

Correct Answer: C

For complex open tibial plateau fractures with significant soft tissue injury, the 'staged protocol' is generally preferred. This involves initial debridement, provisional stabilization with an external fixator, and then delayed definitive internal fixation once the soft tissues have adequately recovered and the 'wrinkle sign' is present (indicating decreased edema). This typically occurs between 5-10 days (Option C). Operating immediately in compromised soft tissues increases the risk of wound complications and infection. Waiting too long (3 weeks) might lead to fracture stiffness and more difficult reduction. The question specifically asks for definitive internal fixation, not initial debridement or external fixation, which should happen urgently. The 'wrinkle sign' is key to timing definitive fixation in such injuries. Although the explanation previously stated 5-10 days, the given options for a delayed approach make 'between 5-10 days, once the 'wrinkle sign' returns' the most appropriate.

Question 49:

What is the most common benign bone tumor of the hand?

• A: Enchondroma
• B: Osteochondroma
• C: Giant cell tumor
• D: Aneurysmal bone cyst
• E: Osteoid osteoma

Explanation:

Correct Answer: A

Enchondroma is by far the most common benign bone tumor of the hand, frequently found in the phalanges and metacarpals. Osteochondromas are common benign tumors but less frequent in the hand than enchondromas. Giant cell tumors are rare in the hand, and aneurysmal bone cysts and osteoid osteomas are also less common in this location compared to enchondromas.

Question 50:

A 55-year-old female presents with severe, progressive back pain radiating down both legs, worsening with standing and walking, and relieved by sitting or leaning forward. She also reports bilateral leg numbness and weakness. On examination, she has diminished patellar and Achilles reflexes bilaterally. What is the most likely diagnosis?

• A: Lumbar disc herniation with radiculopathy
• B: Lumbar spinal stenosis
• C: Cauda equina syndrome
• D: Spondylolisthesis with nerve root compression
• E: Facet joint arthropathy

Explanation:

Correct Answer: B

The classic symptoms of neurogenic claudication – bilateral leg pain, numbness, and weakness exacerbated by standing/walking and relieved by sitting/leaning forward (shopping cart sign) – are highly indicative of lumbar spinal stenosis. While a large disc herniation or spondylolisthesis can cause radiculopathy, bilateral symptoms relieved by flexion strongly point towards stenosis. Cauda equina syndrome would involve acute urinary retention, saddle anesthesia, and severe, progressive neurological deficits. Facet arthropathy typically causes axial back pain, potentially referred pain, but not classic neurogenic claudication.

Question 51:

In the management of a displaced femoral shaft fracture in a 3-year-old child, which of the following is the most appropriate initial treatment?

• A: Immediate intramedullary nailing
• B: Spica cast immobilization
• C: External fixation
• D: Open reduction and plate fixation
• E: Skeletal traction followed by cast

Explanation:

Correct Answer: B

For a displaced femoral shaft fracture in a 3-year-old child, spica cast immobilization is the preferred initial treatment. Children in this age group have excellent remodeling potential and tolerate cast immobilization well. Intramedullary nailing is typically reserved for older children (usually >5-6 years) or specific fracture patterns. External fixation is generally reserved for open fractures, polytrauma, or significant soft tissue compromise. Open reduction and plating is used in specific circumstances but not as first-line for this age group. Skeletal traction followed by cast is an older method, largely supplanted by immediate spica casting for this age group.

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