This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 10581
Topic: Infection, Pharmacology & VTE
Which bone is most commonly affected by osteomyelitis in IV drug users?
Correct Answer & Explanation
. Vertebral bodies
Explanation
Intravenous drug users (IVDU) are particularly susceptible to hematogenous osteomyelitis of the vertebral bodies, often caused by Staphylococcus aureus or Pseudomonas aeruginosa. This is due to direct inoculation of bacteria into the bloodstream and subsequent spread to the highly vascular vertebral bodies. While long bones can be affected, the spine is a notably common site in this population.
Question 10582
Topic: Infection, Pharmacology & VTE
What is the primary concern for a patient with an unstable Colles fracture undergoing surgical fixation who is also on anticoagulant therapy (e.g., warfarin)?
Correct Answer & Explanation
. Increased bleeding risk during and after surgery
Explanation
The primary concern for a patient on anticoagulant therapy undergoing surgical fixation for a Colles fracture is an increased bleeding risk during and after surgery. This necessitates careful preoperative management to optimize coagulation status, often involving temporary cessation or bridging therapy, to minimize hematoma formation and blood loss. Anticoagulants do not directly affect fracture reduction or nonunion rates, nor are they a primary risk factor for CRPS or DVT (in fact, they reduce DVT risk).
Question 10583
Topic: 1. General Principles & Basic Science
A patient with a Colles fracture treated conservatively develops significant stiffness and pain in the hand and wrist, with skin trophic changes and hypersensitivity. What is the most appropriate initial management step?
Correct Answer & Explanation
. Referral for physical therapy focusing on pain control and desensitization, and consider pharmacology for CRPS.
Explanation
The symptoms described (stiffness, pain, trophic changes, hypersensitivity) are classic for Complex Regional Pain Syndrome (CRPS) Type I. The most appropriate initial management involves a multidisciplinary approach including early referral for physical and occupational therapy focusing on pain control, desensitization, and gentle active range of motion. Pharmacological management (e.g., NSAIDs, gabapentinoids, bisphosphonates) and sympathetic blocks may also be considered. Further immobilization would worsen CRPS. Surgical exploration is not indicated for CRPS itself.
Question 10584
Topic: Biology, Genetics & Bone Healing
Regarding avascular necrosis (AVN) of the femoral head, which of the following statements is most accurate?
Correct Answer & Explanation
. MRI is the most sensitive imaging modality for early diagnosis.
Explanation
MRI is the most sensitive and specific imaging modality for early diagnosis of AVN, capable of detecting changes before they are visible on plain radiographs. Corticosteroid use is a commonacquiredrisk factor, but the most common cause is often considered idiopathic. The earliest radiographic signs are typically subtle changes in bone density, while the crescent sign (subchondral collapse) represents a later, pre-collapse stage. Core decompression is indicated for Ficat Stage I or II disease (pre-collapse) to halt progression, not Stage IV (end-stage arthritis). Bisphosphonates have shown promise in some studies, but are not universally effective and their role is still evolving.
Question 10585
Topic: Infection, Pharmacology & VTE
Which of the following is the most common cause of osteomyelitis in healthy adults?
Correct Answer & Explanation
. Staphylococcus aureus
Explanation
Staphylococcus aureus is by far the most common causative organism for osteomyelitis in both children and adults, regardless of the route of infection (hematogenous, contiguous, or direct inoculation). Pseudomonas is often seen in puncture wounds or intravenous drug users. Salmonella is associated with sickle cell disease. Mycobacterium tuberculosis causes Pott's disease (spinal tuberculosis) and other chronic forms of osteomyelitis. E. coli can cause osteomyelitis, especially in immunocompromised or elderly patients, but less frequently than S. aureus.
Question 10586
Topic: 1. General Principles & Basic Science
Which of the following is an absolute contraindication to the use of a tourniquet during orthopedic surgery?
Correct Answer & Explanation
. Peripheral vascular disease
Explanation
Severe peripheral vascular disease (PVD) is an absolute contraindication to tourniquet use. Applying a tourniquet in a limb with compromised arterial inflow can lead to further ischemia, tissue necrosis, or even limb loss. While sickle cell trait might increase risk, it's sickle cell disease that is a more significant concern. A history of DVT is a relative contraindication, managed with anticoagulation and prophylactic measures. Severe hypertension and obesity are not absolute contraindications but require careful monitoring and appropriate tourniquet pressure settings.
Question 10587
Topic: Infection, Pharmacology & VTE
Which of the following imaging modalities is considered the most sensitive for detecting early signs of osteomyelitis in the appendicular skeleton?
Correct Answer & Explanation
. MRI with contrast
Explanation
MRI with contrast is the most sensitive and specific imaging modality for detecting early signs of osteomyelitis, particularly marrow edema, inflammation, and abscess formation in the appendicular skeleton. It can detect changes within 3-5 days of infection. Plain radiographs are typically normal in the first 10-14 days. CT is good for cortical bone destruction and sequestrum but less sensitive for early soft tissue and marrow changes. Technetium bone scans are highly sensitive but less specific. Gallium scans are more specific for infection but have lower spatial resolution and are less commonly used as a first-line diagnostic tool than MRI.
Question 10588
Topic: 1. General Principles & Basic Science
Which of the following laboratory findings is most characteristic of gouty arthritis?
Correct Answer & Explanation
. Negatively birefringent urate crystals in synovial fluid.
Explanation
The hallmark diagnostic finding for gouty arthritis is the presence of negatively birefringent, needle-shaped urate crystals in the synovial fluid, identified under polarized light microscopy. Elevated CRP and ESR are general inflammatory markers and are not specific to gout. Leukocytosis in synovial fluid can vary but typically ranges from 10,000-100,000 cells/mm³ in gout, often higher than the 2,000-10,000 range. Calcium pyrophosphate crystals are characteristic of pseudogout (CPPD disease), which are positively birefringent.
Question 10589
Topic: Biology, Genetics & Bone Healing
A 10-year-old boy presents with progressive genu varum. Radiographs show irregular metaphyses, flaring, and cupping of the distal femurs and proximal tibias. His vitamin D levels are normal, and he has a normal calcium-phosphate product. What is the most likely diagnosis?
Correct Answer & Explanation
. Hypophosphatemic rickets
Explanation
The radiographic findings of irregular, flared, and cupped metaphyses are classic signs of rickets. Given the progressive genu varum and normal vitamin D and calcium-phosphate product, hypophosphatemic rickets (e.g., X-linked hypophosphatemia) is the most likely diagnosis. This condition is characterized by renal phosphate wasting despite normal vitamin D levels. Physiologic genu varum usually resolves by age 2. Blount's disease primarily affects the medial proximal tibia. Renal osteodystrophy would have abnormal calcium/phosphate levels. Metaphyseal chondrodysplasia is a broader category, but hypophosphatemic rickets fits the specific laboratory findings.
Question 10590
Topic: Infection, Pharmacology & VTE
A 65-year-old female presents with severe pain, swelling, and redness in her left great toe, acutely worsening over the past 24 hours. She has a history of hypertension and takes a diuretic. Synovial fluid aspiration shows negatively birefringent, needle-shaped crystals. What is the definitive long-term pharmacologic treatment to prevent future attacks?
Correct Answer & Explanation
. Allopurinol
Explanation
The clinical picture and synovial fluid analysis (negatively birefringent, needle-shaped crystals) confirm a diagnosis of gout. While NSAIDs, colchicine, and prednisone are used to treat acute attacks, allopurinol is the definitive long-term pharmacologic treatment forpreventionof future attacks by decreasing uric acid production. Probenecid is also a uricosuric agent but acts differently. Allopurinol is typically initiated once the acute attack has resolved.
Question 10591
Topic: Surgical Anatomy & Approaches
Which surgical approach to the hip carries the highest risk of sciatic nerve injury?
Correct Answer & Explanation
. Posterior (Moore) approach
Explanation
The posterior (Moore) approach to the hip involves dissecting through the short external rotators and often requires retraction of the sciatic nerve, placing it at the highest risk of injury compared to other approaches. The anterior, direct lateral, and anterolateral approaches generally pose a lower risk to the sciatic nerve as they are distant from its course.
Question 10592
Topic: Surgical Anatomy & Approaches
Which nerve is most commonly injured in a displaced midshaft humerus fracture?
Correct Answer & Explanation
. Radial nerve
Explanation
The radial nerve is intimately associated with the midshaft of the humerus as it courses through the spiral groove. Therefore, it is the most commonly injured nerve in midshaft humerus fractures. Injury to the radial nerve typically results in wrist drop and sensory deficits on the dorsum of the hand.
Question 10593
Topic: Infection, Pharmacology & VTE
What is the most common pathogen responsible for septic arthritis in a healthy adult?
Correct Answer & Explanation
. Staphylococcus aureus
Explanation
Staphylococcus aureus is by far the most common pathogen responsible for septic arthritis in healthy adults, as well as in children and those with prosthetic joints. While other bacteria can cause septic arthritis, S. aureus accounts for the majority of cases. Neisseria gonorrhoeae is common in young, sexually active individuals but less overall than S. aureus. S. epidermidis is common in prosthetic joint infections but less so in native joint septic arthritis.
Question 10594
Topic: Biology, Genetics & Bone Healing
What is the primary mechanism of action of bisphosphonates in the treatment of osteoporosis?
Correct Answer & Explanation
. Inhibit osteoclast activity and bone resorption
Explanation
Bisphosphonates are the most commonly prescribed class of drugs for osteoporosis. Their primary mechanism of action is to inhibit osteoclast activity, thereby decreasing bone resorption and slowing down bone loss, which helps to increase bone mineral density over time. They do not directly stimulate osteoblast activity, increase gut calcium absorption, enhance renal calcium reabsorption, or modulate estrogen receptors (that's the role of SERMs).
Question 10595
Topic: Surgical Anatomy & Approaches
A 25-year-old male driver involved in a head-on motor vehicle collision presents with severe hip pain. Radiographs reveal a posterior dislocation of the right hip. Prior to reduction, a detailed neurologic exam notes inability to extend the right great toe and decreased sensation over the dorsal first web space. The hip is successfully reduced via closed means under conscious sedation. Post-reduction, the neurologic deficit remains unchanged. What is the most appropriate management of the neurologic deficit?
Correct Answer & Explanation
. Observation and application of an ankle-foot orthosis (AFO)
Explanation
Sciatic nerve injury (most commonly the peroneal division) occurs in 10-20% of posterior hip dislocations. If the neurologic deficit is present BEFORE reduction and persists post-reduction, the standard of care is observation, as the injury is usually a neuropraxia from the initial stretch, and most patients recover spontaneously. An AFO helps prevent equinus contracture and assists with ambulation. Surgical exploration is indicated only if a new nerve palsy develops AFTER reduction (suggesting iatrogenic entrapment of the nerve or a bone fragment) or if an incarcerated fragment is seen on post-reduction CT.
Question 10596
Topic: Surgical Anatomy & Approaches
A 60-year-old male slips on ice and grabs a railing to break his fall, sustaining a forceful hyperabduction injury to his shoulder. He presents to the ER with his arm locked in 120 degrees of abduction and his elbow flexed, with his hand resting near his head. What is the most commonly associated nerve injury with this specific type of dislocation?
Correct Answer & Explanation
. Axillary nerve
Explanation
The clinical presentation (arm locked in extreme abduction/flexion) is pathognomonic for luxatio erecta (inferior shoulder dislocation). This severe injury has a high rate of associated complications. The axillary nerve is the most commonly injured nerve (up to 60% of cases) due to traction as the humeral head is forced inferiorly into the axilla. There is also a significant risk of axillary artery injury and massive rotator cuff tears.
Question 10597
Topic: 1. General Principles & Basic Science
In multiligamentous knee injuries (knee dislocations), the popliteal artery is at extremely high risk for intimal tear or transection due to its anatomic tethering points. Which of the following correctly identifies the proximal and distal tethering sites of the popliteal artery?
Correct Answer & Explanation
. Adductor hiatus and soleal arch
Explanation
The popliteal artery is highly susceptible to traction injury during knee dislocations because it is firmly fixed anatomically. Proximally, it is tethered as it exits the adductor hiatus (opening in the adductor magnus). Distally, it is tethered as it passes deep to the tendinous arch of the soleus muscle (soleal arch) before bifurcating.
Question 10598
Topic: 1. General Principles & Basic Science
A 35-year-old construction worker is extricated after being trapped beneath concrete rubble for 8 hours. He has bilateral severe crush injuries to the lower extremities. Laboratory tests reveal significant myoglobinuria. Alongside aggressive isotonic intravenous fluid resuscitation, which of the following medications is most appropriate to specifically prevent the precipitation of myoglobin in the renal tubules?
Correct Answer & Explanation
. Intravenous sodium bicarbonate
Explanation
In crush syndrome, massive muscle breakdown leads to rhabdomyolysis and myoglobinuria. Myoglobin is highly nephrotoxic, particularly in acidic environments where it precipitates and causes acute tubular necrosis. Aggressive IV hydration is the primary treatment, but the addition of IV sodium bicarbonate is recommended to alkalinize the urine (target pH > 6.5), which significantly prevents myoglobin precipitation. Calcium, insulin/dextrose, and sodium polystyrene sulfonate are used to treat hyperkalemia, not specifically to protect renal tubules from myoglobin.
Question 10599
Topic: 1. General Principles & Basic Science
A 19-year-old male football player sustains a traumatic posterior sternoclavicular (SC) joint dislocation. He complains of dysphagia, neck pressure, and mild shortness of breath. Closed reduction is planned in the operating room. What is the most critical logistical preparatory step prior to attempting the closed reduction?
Correct Answer & Explanation
. Ensuring a thoracic surgeon is present or immediately available in the OR
Explanation
Posterior sternoclavicular dislocations are orthopedic emergencies due to the proximity of critical mediastinal structures, including the trachea, esophagus, and great vessels (subclavian artery/vein, brachiocephalic vein). Closed reduction carries a risk of catastrophic vascular injury or displacement if a great vessel has been compromised or pseudoaneurysm is present. Therefore, it is absolutely critical to have a thoracic surgeon or vascular surgeon present or immediately available in the operating room before attempting reduction.
Question 10600
Topic: Surgical Anatomy & Approaches
A 42-year-old male presents to the ED with his arm locked in 120 degrees of abduction and his forearm resting on his head following a fall. He reports numbness over the lateral aspect of his shoulder. Radiographs confirm luxatio erecta. Which neurovascular structure is most commonly injured in this type of dislocation?
Correct Answer & Explanation
. Axillary nerve
Explanation
Luxatio erecta is an inferior shoulder dislocation presenting with the arm locked in hyperabduction. The axillary nerve is the most commonly injured neurovascular structure due to the severe inferior displacement of the humeral head.
Test Yourself
Switch to an interactive, timed exam simulation to truly master this topic.