Question 1

A new laboratory test trialled in 10 000 people showed a positive result in 11 people. Of the 10 000, 11 people have cystic fibrosis and ten of the 11 had a positive test result. What is the sensitivity of the test for cystic fibrosis?

Explanation

Correct Answer: D-0.9 Explanation 0.9 This is a ‘know it or you don’t’ question. It is useful to know how both sensitivity and specificity are calculated. Sensitivity refers to the proportion of people with disease that have a positive test result. Specificity refers to the proportion of people without disease that have a negative

test result. SnNout is a mnemonic applied to the finding that when a sign, test or symptom has a high Sensitivity, a Negative result rules out the diagnosis. SpPin is a mnemonic applied to the finding that when a sign, test or symptom has a high Specificity, a Positive result rules in the diagnosis. How to calculate the sensitivity and specificity:

Target disorder Present Absent Diagnostic test reult +ve a b a + b -ve c d c + d a + c b + d a + b + c + d From this table, the sensitivity and specificity can be determined as follows:

• Sensitivity = a/(a + c) • Specificity = d/(b + d) 0.01 0.01 is incorrect. When correctly calculated the sensitivity here is 0.9. 0.09 0.09 is incorrect. When correctly calculated the sensitivity here is 0.9. 0.1 0.1 is incorrect. When correctly calculated the sensitivity here is 0.9. 1 1 is incorrect. When correctly calculated the sensitivity here is 0.9.

Question 2

A 40-year-old man complains of increasing shortness of breath and his chest X-ray shows an elevated hemidiaphragm on the left side; no other abnormalities are seen. What is the most likely investigation to elucidate the mechanical reason for his shortness of breath?

Explanation

Correct Answer: D- Fluoroscopy Explanation Fluoroscopy The diagnosis of unilateral paralysis, suggested by asymmetric elevation of the affected hemidiaphragm on X-ray, can be confirmed by fluoroscopy. During a forced inspiratory manoeuvre (the ‘sniff’ test), the unaffected hemidiaphragm descends forcefully, increasing intra- abdominal pressure and pushing the paralysed hemidiaphragm cephalad (paradoxical motion). Fluoroscopy is inaccurate for the diagnosis of bilateral paralysis. Computed tomography (CT) thorax scan Computed tomography (CT) thorax scan is incorrect. CT scan will demonstrate an elevated hemidiaphragm, but dynamic imaging is required to show diaphgragmatic paralysis which is the diagnosis here. Echocardiography Echocardiography is incorrect. The breathlessness here is not cardiac in origin, it is due to diaphragmatic paralysis, therefore cardiac investigations would not be helpful in making a diagnosis here. Electrocardiogram (ECG) Electrocardiogram (ECG) is incorrect. The breathlessness here is not cardiac in origin, it is due to diaphragmatic paralysis, therefore cardiac investigations would not be helpful in making a diagnosis here. Magnetic resonance imaging (MRI) scan Magnetic resonance imaging (MRI) scan is incorrect.

Although MRI may demonstrate a structural defect, it is not a dynamic investigation and would not be the most helpful here.

Question 3

A 20-year-old woman complains of a sudden onset of dyspnoea associated with pleuritic chest pain. She takes the oral contraceptive pill, and has a BMI of 31. Her O2 saturation is 92% on air. Chest X- ray is reported as normal, pregnancy test is negative. Which of the following methods of assessment is the most appropriate to confirm your diagnosis of pulmonary embolism?

Explanation

Correct Answer: A- CTPA Explanation CTPA CT pulmonary angiogram (CTPA), widely available in most Emergency units, is now seen as the diagnostic test of choice for for pulmonary embolus. d-Dimer d- Dimer is incorrect. A negative d-dimer test is useful for excluding pulmonary embolism (PE) in patients who are clinically thought to be at low risk, but a ‘positive’ result does not establish the diagnosis. We do not have full clinical information here to calculate this lady’s Well’s score, but it is likely she would be classed as high risk and therefore d-dimer testing would be inappropriate. Echocardiography Echocardiography is incorrect. Echocardiography might show right ventricular dilatation and evidence of pulmonary hypertension, which, in the proper clinical setting, might strengthen the clinical impression that a PE has occurred; however, a CTPA is the most likely test to give a definitive diagnosis here. Right heart catheterisation Right heart catheterisation is incorrect. Right heart catheterisation is not available in all hospitals and is an invasive investigation that should not be used to diagnose PE. If PE is present, this test will show elevated right heart pressures and pulmonary hypertension. In a small number of patients with massive PE, right heart catheterisation may be used to perform percutaneous thrombectomy to administer local thrombolysis to the site of the PE if there are contraindications to systemic thrombolysis. Ventilation perfusion scan Ventilation perfusion scan is incorrect. Ventilation/perfusion scans have been superceded by CTPA in the diagnostic work up of PE. Their use should now be restricted to individuals with contrast allergy or where the risk from radiation from CTPA is high.

Question 4

A 63-year-old woman who is a lifelong smoker is found to have non-small-cell lung cancer. Which of the symptoms below is most likely to be her presenting symptom?

Explanation

Correct Answer: C- Cough Explanation Cough Non-small-cell lung cancer can present in a number of different ways. The most common presentation is cough (45%) followed by breathlessness (37%). Chest pain and haemoptysis occur in about a third of patients; anorexia and weight loss affect about a fifth; and 3% experience dysphagia. About 15% of patients are asymptomatic, their lung cancer being detected on a routine chest X-ray being performed for another reason. Breathlessness Breathlessness is incorrect. Cough is the most common presentation affecting 45% of patients compared to 37% of patients for breathlessness. Chest wall pain Chest wall pain is incorrect. Cough is the most common presentation affecting 45% of patients compared to 33% of patients for chest pain. Haemoptysis Haemoptysis is incorrect. Cough is the most common presentation affecting 45% of patients compared to 33% of patients for haemoptysis. Weight loss Weight loss is incorrect. Cough is the most common presentation affecting 45% of patients compared to around 20% of patients for anorexia and weight loss.

Question 5

A 32-year-old woman is admitted to the Emergency Department with a severe cough and shortness of breath. She has been unwell for a few days with a cough and sore throat and now says she is coughing purulent sputum which is rust-coloured and blood-stained. She has a history of asthma which is usually managed with a Seretide® inhaler. On examination, she is pyrexial (38.2 °C) and has a blood pressure of 110/82 mmHg. Her pulse is 95 bpm and regular. She has a respiratory rate of 30/min and coarse inspiratory crackles to the mid- zone on the right- hand side. There are marked cold sores affecting her upper lip.

Investigation:

Hb 12.1 g/dl

WCC 14.3 x 109/l

PLT 202 x 109/l

Sodium 139 mmol/l

Potassium 4.5 mmol/l

Creatinine 179 µmol/l CRP 170 mg/l

Po2 9.1 kPa

Pco2 4.3 kPa Which of the following is the most likely cause of her underlying pneumonia?

Explanation

Correct Answer: E- Streptococcus pneumoniae Explanation Streptococcus pneumoniae The history is very typical of community-acquired pneumonia, the commonest cause of which is Streptococcus pneumoniae, and the clinical findings and investigations are also consistent with this. Herpes labialis is usually associated with Streptococcus pneumoniae infection. Management involves the combination of a penicillin such as amoxicillin with a macrolide such as clarithromycin. Chlamydia pneumoniae Chlamydia pneumoniae is incorrect. Chlamydia pneumoniae usually causes a mild pneumonia and many patients are asymptomatic. Klebsiella pneumoniae Klebsiella pneumoniae is incorrect. Klebsiella pneumoniae classically causes a cavitating pneumonia affecting the upper lobe(s). Mycoplasma pneumoniae Mycoplasma pneumoniae is incorrect. Mycoplasma pneumoniae causes an atypical pneumonia, classically with headaches, myalgia and a dry cough. It has an insidious onset, often over weeks. Staphylococcus aureus Staphylococcus aureus is incorrect. Staphylococcus aureus is not a common cause of community- acquired pneumonia unless an individual has immunosuppression. It may also occur after influenza infection. Pneumonia is classically cavitating.

Question 6

A 26-year-old woman with previously well-controlled asthma on low-dose Seretide comes to the clinic for review. She has recently discontinued her inhaler and sticks only to PRN salbutamol as she is 4 months pregnant. On examination her BP is 100/60 mmHg, pulse is 79/min and regular. She has bilateral fine wheeze, and a peak flow of 350 l/min (510 predicted). Which of the following is the correct management for her?

Explanation

Correct Answer: D- Restart previous dose of Seretide Explanation Restart previous dose of Seretide Several physiological changes occur in pregnancy, which are recognised to either improve or worsen the control of asthma, and it is well recognised that worsening or improvement of symptoms during the course of a pregnancy is difficult to predict. What is known, however, is that if asthma is well controlled during the pregnancy then there is little or no increased risk of maternal or fetal complications. With respect to use of long-acting β-agonists (LABA) and inhaled steroids, BTS/SIGN guidelines recommend continuing the normal dose as there is no evidence of increased risk to the mother or fetus from taking these medications. Fluticasone only Fluticasone only is incorrect. Although fluticasone can be taken in pregnancy if indicated, the most appropriate thing to do here is to restart the treatment which is known to provide effective control of this lady’s asthma. Give monteleukast Give monteleukast is incorrect. Although monteleukast can be taken in pregnancy if indicated, the most appropriate thing to do here is to restart the treatment which is known to provide effective control of this lady’s asthma. Monteleukast should not be started in an asthmatic prior to inhaled steroids. Oral prednisolone Oral prednisolone is incorrect. Oral prednisolone can be used in pregnancy but should be reserved for treating exacerbations or where patients have failed to gain control on inhaled medications. Salmeterol only Salmeterol only is incorrect. Although salmeterol can be taken in pregnancy if indicated, the most appropriate thing to do here is to restart the treatment which is known to provide effective control of this lady’s asthma. Salmeterol should not be started in an asthmatic prior to inhaled steroids.

Question 7

A 17-year-old woman presents with a dry cough and pyrexia, some 3 weeks after induction therapy for acute lymphoblastic leukaemia. She has been treated with a macrolide and co-amoxiclav by her GP but there has been no response. On examination she is pyrexial 38.2 °C and short of breath at rest. There are scattered crackles throughout both lung fields on auscultation.

Investigations:

Hb 12.3 g/dl

WCC 9.1 × 109/l

PLT 155 × 109/l

Na+ 138 mmol/l

K+ 4.2 mmol/l

Creatinine 102 μmol/l LDH 420 U/l

CXR Diffuse bilateral infiltrates extending from the perihilar region pH 7.36

pO2 9.8 kPa

pCO2 4.7 kPa Which of the following is the most likely diagnosis?

Explanation

Correct Answer: E- Pneumocystis jirovecii Explanation Pneumocystis jirovecii The pattern of diffuse pulmonary infiltrates coupled with mild hypoxia fits best with Pneumocystis jirovecii. Saturation falls rapidly on minimal exercise, and ambulatory oximetry is a useful further investigation. Co-trimoxazole is the effective antibiotic in treating the acute infection. CMV pneumonitis CMV pneumonitis is incorrect. Cytomegalovirus (CMV) is a reasonable differential diagnosis here but the chest radiograph appearances described are absolutely classical for Pneumocystis jirovecii pneumonia. Fungal pneumonitis Fungal pneumonitis is incorrect. Fungal pneumonitis is a reasonable differential diagnosis here but the chest radiograph appearances described are absolutely classical for Pneumocystis jirovecii pneumonia. Klebsiella pneumoniae Klebsiella pneumoniae is incorrect. Klebsiella pneumonia typically affects the upper lobes and is cavitating. Leukaemic infiltration Leukaemic infiltration is incorrect. Although raised LDH levels are seen in haematological malignancy, they would be expected to fall after induction chemotherapy, so the raised LDH seen here fits with Pneumocystis jirovecii infection.

Question 8

You are asked to see a 57-year-old smoker, who complains of shortness of breath some 7 days after a total hip replacement. On examination, he is obese and has a swollen left leg. He is also visibly short of breath. There appears to be increased prominence of vascular markings at the right hilum on the chest X-ray. His calculated alveolar–arterial (a–a) gradient is 34 mmHg (10-24 normal range). Which of the following fits best with his diagnosis?

Explanation

Correct Answer: E- Pulmonary embolus Explanation Pulmonary embolus The alveolar–arterial (A–a) gradient is affected primarily by ventilation/perfusion (V/Q) mismatch and shunting. This means that changes in alveolar–arterial gradient occur with ventilatory disorders, such as pneumonia, and disorders of the vasculature, such as a pulmonary embolus. Pulmonary embolus is the most likely diagnosis here. The alveolar–arterial (A–a) gradient is calculated using the following equation (where PAo2 is the alveolar oxygen, and Pao2 and Paco2 are the arterial O2 and CO2 levels, respectively):

PAo2 – (Pao2 + Paco2/0.8) The alveolar oxygen level in kPa is calculated by: (100 - 7)/100 × % inspired O2 eg for 21% O2, the PAo2 would be 20 mmHg. The gradient is then calculated by taking the arterial partial pressure of oxygen from the alveolar one. Because inspired oxygen can alter the ‘normal’ alveolar– arterial (A–a) gradient also varies according to level of inspired oxygen; if you are using a chart you must make sure that you are using the correct line on the chart corresponding to the correct inspired oxygen concentration. Atelectasis Atelectasis is incorrect. Atelectasis can certainly occur post-operatively. However, it is not noted on the chest radiograph and the presence of a unilaterally swollen leg is suggestive of venous thromboembolism. Hyperventilation syndrome Hyperventilation syndrome is incorrect. Hyperventilation is associated with a normal A–a gradient and in a 57- year-old patient this should typically be between 10 and 24 mmHg. This man has a reduced A–a gradient and a high clinical proabability of pulmonary embolus. Pneumothorax Pneumothorax is incorrect. The chest radiograph does not show a pneumothorax and this man has signs and symptoms more compatible with pulmonary embolism. Post-operative pneumonia Post-operative pneumonia is incorrect. The lack of consolidation on chest radiograph or infective symptoms, such as fever or productive cough, makes respiratory infection an unlikely diagnosis here.

Question 9

A 26-year-old male smoker presents to the Emergency Department with sudden onset of left-sided pleuritic chest pain and breathlessness. He takes no regular medication and has not received a diagnosis of significant chest disease. A chest X-ray confirms the clinical suspicion of a left sided pneumothorax with a 2.5cm rim of air. What should the initial management of his pneumothorax be?

Explanation

Correct Answer: B- Aspiration Explanation Aspiration The immediate management of a spontaneous primary pneumothorax >2cm is air aspiration. 100% inspired oxygen 100% inspired oxygen is incorrect. High-flow oxygen is helpful regardless of a patient’s oxygen saturations in pneumothorax as it aids resolution of the pneumothorax; however, 100% oxygen is not required. The correct initial management is aspiration. Conservative treatment Conservative treatment is incorrect. In a young, stable patient conservative management can be considered if the pneumothorax is small (rim of air is < 2 cm at level of hilum). Intercostal tube drainage Intercostal tube drainage is incorrect. Intercostal tube drainage should be reserved for patients who fail to respond to aspiration or who have a tension pneumothorax. Surgical referral for pleurodesis Surgical referral for pleurodesis is incorrect. Surgical referral is considered in patients who develop complications of their pneumothorax (ie bronchopleural fistula) or who have had more than one pneumothorax.

Question 10

A 75-year-old woman visits your chronic obstructive pulmonary disease (COPD) clinic for review. Her blood gases were checked at her last visit 2 months ago when she was relatively well, and you check them again today. Her PaO2 on air on both occasions was 6.8 kPa. There is no CO2 retention on 28% O2. To her credit, she did succeed in stopping smoking 6 months ago. She is maintained on combination inhaled steroid and long- acting ß2-agonist therapy. What is the next management step most likely to improve her prognosis?

Explanation

Correct Answer: E- Suggest she uses an oxygen concentrator for at least 15 hours a day Explanation Suggest she uses an oxygen concentrator for at least 15 hours a day Studies have shown that at least 15 hours of oxygen therapy per day is required to reduce the pulmonary hypertension associated with COPD, to treat the underlying pathology of incipient right heart failure and to improve survival. This cannot be realistically achieved using cylinders, and patients should be given a concentrator and a venturi mask to deliver the oxygen at an FiO2 that corrects the hypoxaemia without inducing hypercapnoea. Add in an anticholinergic to her therapy Add in an anticholinergic to her therapy is incorrect. This would be an appropriate adjunctive therapy to her current regimen, but would not improve her prognosis. Only smoking cessation and long-term oxygen therapy (in patients who meet prescription criteria) improve survival in COPD. Continue her current treatment and review in 4 months’ time Continue her current treatment and review in 4 months’ time is incorrect. Continuing her current therapy will not

alter her prognosis. Give her rotational antibiotics to prevent an exacerbation Give her rotational antibiotics to prevent an exacerbation is incorrect. There is no evidence for routine prophylactic rotational antibiotics in COPD. Offer her oxygen cylinders for use as required Offer her oxygen cylinders for use as required is incorrect. This lady’s gases indicate that long-term oxygen therapy will confer a survival benefit. Short-burst oxygen therapy may provide symptom relief but will not improve her survival.

Question 11

A 58-year-old smoker with chronic bronchitis was treated with antibiotics for a right upper-lobe bronchopneumonia by his GP. After 6 weeks he was readmitted to hospital. The chest X-ray shows signs of a pneumonia in the same place. What is the most likely reason?

Explanation

Correct Answer: A- Bronchial carcinoma with post- stenotic pneumonia Explanation Bronchial carcinoma with post-stenotic pneumonia Non-resolving pneumonia is an indication of bronchogenic carcinoma. An ill-defined homogeneous or patchy consolidation in a segmental or non-segmental distribution might be an indication of bronchogenic carcinoma. Patients with these findings are often initially treated for pneumonia; the lack of response to antibiotic therapy suggests the diagnosis of a malignancy. Radiological signs:

• An endobronchial lesion commonly leads to partial or complete atelectasis and this is the most common sign of bronchogenic carcinoma • Bronchial stenosis and post-stenotic changes are commonly seen because most non-small- cell carcinomas demonstrate intraluminal growth. Narrowing of the main bronchi or a complete cut-off can be identified on chest X-rays • Complete endobronchial obstruction can sometimes produce distal mucoid impaction, which can be visible on plain chest X-rays as a tubular or branching opacity • The opacity can contain air bronchograms and air alveolograms. This presentation is often seen with adenocarcinoma and bronchoalveolar carcinoma Candida pneumonia Candida pneumonia is incorrect. Candida pneumonia would be very unusual in a patient who is not immunosuppressed. Given there is nothing in the history to suggest immunosuppression, this diagnosis is unlikely. Immunodeficiency Immunodeficiency is incorrect. Given this gentleman’s age, one would expect more history of recurrent infections +/- bronchiectasis if primary immunodeficiency was the correct diagnosis. There is no history given to suggest a secondary immunodeficiency such as HIV, immunosuppressive medications or haematological malignancy. Sarcoidosis Sarcoidosis is incorrect. Sarcoidosis does not present as pneumonia clinically or on a chest radiograph. It is likely the chest radiograph would show bilateral hilar lymphadenopathy +/- interstitial infiltrates, but not focal consolidation. Tuberculosis Tuberculosis is incorrect. In a non-resolving right upper lobe pneumonia, tuberculosis is a reasonable differential diagnosis, but given the lack of history suggesting this patient is at risk of tuberculosis (eg ethnicity, known contact with TB, alcoholism, malnutrition, immunosuppression) and the fact that this patient is a smoker, the most likely underlying diagnosis is bronchial carcinoma.

Question 12

A 67-year-old man consults his doctor complaining of a painful mouth and increasing difficulty eating. He has a past history of smoking and has chronic obstructive pulmonary disease (COPD). His medication history includes use of a fluticasone/salmeterol combination inhaler and omeprazole for indigestion. On examination he has a body mass index (BMI) of 29 kg/m2 and looks well. There is extensive stomatitis and

pharyngitis on examination of the oropharynx, with white plaques on examination of the tongue. Full blood count, U&Es, liver function tests (LFTs) and viscosity are all normal. Which of the following would be the most appropriate management in this case?

Explanation

Correct Answer: A- Advise him to rinse his mouth each time he uses his inhaler and use a spacer device and review him in a month Explanation Advise him to rinse his mouth each time he uses his inhaler and use a spacer device and review him in a month This man almost certainly has oropharyngeal and oesophageal candidiasis from inadequate hygiene after using his inhaler. He should be taught adequate inhaler technique and urged to rinse his mouth after each use. Resistant symptoms can be managed with oral nystatin or a course of fluconazole. Arrange urgent barium swallow Arrange urgent barium swallow is incorrect. The lack of weight loss and the normal investigation results makes underlying malignancy unlikely, although a symptom check in 1 month is still advisable. If symptoms had not resolved or had worsened then further investigation with a barium study may be warranted. Arrange an urgent upper gastrointestinal endoscopy Arrange an urgent upper gastrointestinal endoscopy is incorrect. The lack of weight loss and the normal

investigation results makes underlying malignancy unlikely, although a symptom check in 1 month is still advisable. If symptoms had not resolved or had worsened then further investigation with an endoscopy may be warranted. Increase his dose of omeprazole Increase his dose of omeprazole is incorrect. The history is not suggestive of poorly controlled reflux. Stop his inhaled steroids Stop his inhaled steroids is incorrect. It would be more appropriate to try mouth rinsing post dose and the use of a spacer first, and if this does not lead to resolution of his symptoms then consider stopping his current inhaled steroid.

Question 13

A 58-year-old man is referred by his GP with probable obstructive sleep apnoea (OSA). Which of the following features is most strongly associated with OSA?

Explanation

Correct Answer: B- Daytime somnolence Explanation Daytime somnolence Daytime somnolence is the predominant symptom of OSA. Body mass index of 26 kg/m2 Body mass index of 26 kg/m2 is incorrect. Obstructive sleep apnoea is associated with obesity (of which hypothyroidism is a cause) and sedatives such as alcohol. Epworth sleepiness score of 6 Epworth sleepiness score of 6 is incorrect. The Epworth sleepiness score can be between 0 and 24 (the higher the score, the more sleepy the patient is) and 6/24 is low. A score of 11 or more is suggestive of OSA. Normal blood pressure Normal blood pressure is incorrect. OSA is associated with hypertension. Normal oxygen saturations at night Normal oxygen saturations at night is incorrect. OSA results in repeated oxygen desaturations overnight. The disorder is most marked during rapid eye movement (REM) sleep.

Question 14

A 55-year-old man presents with increasing shortness of breath. He has been working in the sand- blasting industry and exposed to quartz particles. What is the most likely diagnosis?

Explanation

Correct Answer: E- Silicosis Explanation Silicosis Silicosis is a fibrotic disease of the lungs caused by inhalation of crystalline silicon dioxide, usually in the form of quartz. Silicosis can affect anyone involved in quarrying, carving, mining, tunnelling, grinding or sand- blasting, if the dust generated contains quartz. Between 50 and 60 cases are diagnosed in the UK each year, generally in people involved in the production of slate or granite, among miners cutting through rock and in fettlers in foundries. Crystalline silica is present in the earth’s crust usually as quartz, although other forms such as crystobalite and tridymite occur occasionally. They are all extremely toxic to macrophages. Quartz seems to be most toxic when freshly fractured, suggesting that its surface properties are important in toxicity. Silicosis presents a spectrum of clinical appearances, depending on the circumstances in which it is contracted. The most severe form is acute silicosis, which can be acquired after very heavy exposure over just a few months, such as during a sand-blasting job without respiratory protection. These patients become intensely breathless and die within months. The X-ray shows appearances resembling pulmonary oedema. Less heavy exposure causes progressively less dramatic symptoms, ranging from a progressive upper lobe fibrosis with slowly increasing exertional dyspnoea over several years (accelerated silicosis) to a condition with radiographic nodular changes similar to coal-worker’s pneumoconiosis (simple nodular silicosis) that is unassociated with any symptoms or physical signs. This last type of silicosis is the most common, and is usually associated with exposure to dust containing 10–30% silica over a prolonged period. Simple nodular silicosis differs from coal-worker’s pneumoconiosis in that the lesions tend to be larger (3–5 mm) and in that it is progressive even after dust exposure ceases. Lesions increase in size and become more profuse. Moreover, extensive simple silicosis can be associated with some restriction of lung volumes. Accelerated silicosis and progressive massive fibrosis cause lung restriction and lead to cor pulmonale and cardiorespiratory failure. Asbestosis Asbestosis is incorrect. Asbestosis can develop following exposure to asbestos fibres. Typical occupations associated with possible exposure include plumbers, electricians, engineers and ship dockyard workers. Asthma Asthma is incorrect. The short history given alludes to an occupation-related cause of breathlessness. The specific mentioning of quartz particles suggests a diagnosis of silicosis. Asthma is not an occupation-related lung disease. Eosinophilic pneumonitis Eosinophilic pneumonitis is incorrect. The short history given alludes to an occupation-related cause of breathlessness. The specific mentioning of quartz particles suggests a diagnosis of silicosis. Eosinophilic pneumonitis is not an occupation-related lung disease. Sarcoidosis Sarcoidosis is incorrect. The short history given alludes to an occupation-related cause of breathlessness. The specific mentioning of quartz particles suggests a diagnosis of silicosis. Sarcoidosis is not an occupation- related lung disease.

Question 15

A 33-year-old woman with cystic fibrosis dies while awaiting a lung transplant. She undergoes a post-mortem examination including a biopsy of the respiratory epithelium. Which of the following cells is likely to be found on the surface of the respiratory epithelium?

Explanation

Correct Answer: E- Neutrophils Explanation Neutrophil infiltration is well recognised as a determinant of progression in cystic fibrosis. Infiltration occurs early in the course of the disease, and neutrophil derived factors such as elastase lead to accelerated damage to the respiratory epithelium. Basophils Basophils (Option A) is incorrect. Basophilic infiltration is associated with fatal asthma. Eosinophils Eosinophils (Option B) is incorrect. Eosinophils are associated with allergic lung diseases. Lymphocytes Lymphocytes (Option C) is incorrect. Lymphocytic infiltration is associated with lymphocytic interstitial pneumonia. Monocytes Monocytes (Option D) is incorrect. Monocyte infiltration may be involved in the development of idiopathic pulmonary fibrosis.

Question 16

A 50-year-old smoker was diagnosed with a non-small- cell carcinoma. Investigations revealed a 4 cm × 3 cm × 2 cm tumour in the lower lobe of his left lung that has invaded the visceral pleura. The ipsilateral hilar lymph node is also involved, but there is no metastatic involvement of any distal organ. What is the stage of disease in this patient?

Explanation

Correct Answer: B- T2 N1 M0 Explanation T2 N1 M0 This is a 'know it or you don't' answer. It is important to remember the criteria for staging carcinoma of the lung. As the tumour is more than 3 cm in its greatest dimension and has only invaded the visceral pleura, it is designated T2. Metastasis to the ipsilateral peribronchial and/or ipsilateral hilar lymph nodes makes the nodal stage N1. Absence of distal metastasis is called M0. TNM staging takes into account:

• The size and position of the tumour (T) • Whether the cancer cells have spread into the lymph nodes (N) • Whether the tumour has spread anywhere else in the body - secondary cancer or metastases (M) It would be useful to go through the staging in detail for other possible combinations. See external link for full TNM staging criteria:

T2 N0 M0 T2 N0 M0 is incorrect. The correct disease staging for this patient is T2 N1 M0. T3 N1 M0 T3 N1 M0 is incorrect. The correct disease staging for this patient is T2 N1 M0. T4 N0 M0 T4 N0 M0 is incorrect. The correct disease staging for this patient is T2 N1 M0. T4 N1 M0 T4 N1 M0 is incorrect. The correct disease staging for this patient is T2 N1 M0.

Question 17

A 48-year-old woman presents with a pleural effusion. You perform a diagnostic pleural aspiration. Which of the following is true regarding the results that you might receive from the laboratory?

Explanation

Correct Answer: A- An eosinophilia makes malignancy less likely Explanation An eosinophilia makes malignancy less likely Pleural fluid eosinophilia (> 10%) makes malignancy and tuberculosis (TB) less likely, and suggests air in the pleural cavity. Heavy bloodstaining effectively excludes pulmonary embolic disease Heavy bloodstaining effectively excludes pulmonary embolic disease is incorrect. Heavily bloodstained fluid in the absence of trauma suggests pulmonary infarction or malignancy. High glucose levels occur in rheumatoid arthritis High glucose levels occur in rheumatoid arthritis is incorrect. Low glucose levels occur in rheumatoid arthritis, TB, empyema and malignancy. Low levels of salivary amylase suggest oesophageal rupture Low levels of salivary amylase suggest oesophageal rupture is incorrect. High levels of salivary amylase suggest oesophageal rupture. The presence of antinuclear factor is virtually diagnostic of scleroderma The presence of antinuclear factor is virtually diagnostic of scleroderma is incorrect. The presence of antinuclear factor is virtually diagnostic of systemic lupus erythematosus (SLE), not scleroderma.

Question 18

A 50-year-old patient presents with blood eosinophilia in association with a radiographic pulmonary infiltrate. A bronchoscopy shows an excess of eosinophils in bronchoalveolar lavage fluid in the absence of pathogenic micro-organisms. The diagnosis of eosinophilic pneumonia is made. What is the best treatment apart from removing the causal factors?

Explanation

Correct Answer: E- Systemic steroids Explanation Systemic steroids Eosinophilic pneumonia often responds well to corticosteroid medication, although treatment might need to be prolonged (6 months or more) in patients with the chronic forms of the disorder. The importance of identifying whether it is associated with the causal factors listed below lies in the need to manage these. Otherwise, eosinophilic pneumonia may not respond adequately to steroid therapy; the associated diseases can also produce other manifestations. Ask yourself whether there are any causal factors:

• Is there parasitic infestation? • Have any drugs been administered? • Is there asthma? • Is there evidence of allergy to parasites or drugs? • Is there evidence of allergic bronchopulmonary mycosis (particularly aspergillosis)? • Is there evidence of vasculitis? • Is there evidence of the hypereosinophilic syndrome? • Is there evidence of other disorders known to be associated with eosinophilic pneumonia? Clarithromycin Clarithromycin is incorrect. Eosinophilic pneumonia is not an infective pneumonia and antibiotics will not improve it. Inhaled ß2-agonists Inhaled ß2-agonists is incorrect. This is a treatment used in asthma. They have no role in the treatment of pure eosinophilic pneumonia, although ß2-agonists may be trialled if there is associated bronchospasm. Leukotriene-receptor antagonists Leukotriene-receptor antagonists is incorrect. This is a treatment used in asthma. They have no role in the treatment of pure eosinophilic pneumonia. Nebulised ß2-agonists Nebulised ß2-agonists is incorrect. This is a treatment used in asthma. They have no role in the treatment of pure eosinophilic pneumonia, although ß2-agonists may be trialled if there is associated bronchospasm.

Question 19

What would the optimal management be for a 70-year- old man with moderate chronic obstructive pulmonary disease (COPD) who has attended the Emergency Department with increasing dyspnoea and who has been found to have a 3 cm pneumothorax?

Explanation

Correct Answer: B- Chest drain insertion initially Explanation Chest drain insertion initially This is a man with a pneumothorax secondary to his COPD. He is symptomatic and the British Thoracic Society (BTS) Guidelines suggest he should not undergo needle aspiration but proceed to chest drain insertion initially, given the rim of the pneumothorax is > 2 cm and he is breathless. Chest drain insertion if needle aspiration fails Chest drain insertion if needle aspiration fails is incorrect. This is appropriate management of a primary pneumothorax > 2 cm. Conservative management, with observation and repeat chest X-ray after 4 hours Conservative management, with observation and repeat chest X-ray after 4 hours is incorrect. Pneumothoraces with a > 2 cm rim should be actively treated with either aspiration (in primary pneumothoraces) or chest drain insertion (secondary pneumothoraces). Conservative management, with observation and repeat chest X-ray after 12 hours Conservative management, with observation and repeat chest X-ray after 12 hours is incorrect. Conservative management is appropriate for primary pneumothoraces if the rim is < 2 cm and the patient is not breathless. For secondary pneumothoraces, conservative management with admission for high-flow oxygen and observation for 24 hours is appropriate if the rim is < 1 cm and the patient is not breathless. Needle aspiration Needle aspiration is incorrect. Needle aspiration is considered as first-line management in secondary pneumothoraces of 1–2 cm in a patient who is not breathless. In primary pneumothoraces, needle aspiration is appropriate first-line management if the patient is breathless or the rim is > 2 cm.

Question 20

In which of the following emergency medical presentations is non-invasive ventilation an established first choice therapy in the presence of respiratory acidosis?

Explanation

Correct Answer: B- Acute exacerbation of chronic obstructive pulmonary disease with respiratory acidosis Explanation Acute exacerbation of chronic obstructive pulmonary disease with respiratory acidosis Non-invasive ventilation (NIV) is currently being evaluated in a number of emergency situations. The best evidence relates to exacerbations of chronic obstructive pulmonary disease. In particular, this type of therapy is effective in patients with decompensated type II respiratory failure. Physiological responses (heart rate, respiratory rate and arterial blood gases) improve more quickly with NIV in these patients compared with standard treatment. Intubation is also less frequently required. Acute asthma Acute asthma is incorrect. The correct management for acute asthma with respiratory acidosis is oxygen, steroids, nebulised bronchodilators, intravenous magnesium alongside urgent critical care/anaesthetic for consideration of intubation and invasive ventilation. Adult respiratory distress syndrome (ARDS) Adult respiratory distress syndrome (ARDS) is incorrect. ARDS with respiratory acidosis is best managed with invasive ventilation using low tidal volumes (6 mL/kg based upon ideal body weight). Pulmonary oedema with hypertension Pulmonary oedema with hypertension is incorrect. NIV is part of a range of therapies for pulmonary oedema, but more usually where pulmonary oedema co-exists with hypertension, diuretics and measures to control blood pressure are normally attempted first. Tension pneumothorax Tension pneumothorax is incorrect. The correct first choice treatment for tension pneumothorax is immediate needle decompression followed by intercostal drain insertion.

Question 21

A diagnostic test has a fixed sensitivity and specificity. If the prevalence of the target disease in the tested population decreases, what is the effect on the predictive values of the test?

Explanation

As disease prevalence decreases, the absolute number of true positives decreases while false positives increase, thus decreasing the positive predictive value (PPV). Conversely, true negatives increase, which increases the negative predictive value (NPV).

Question 22

A 24-year-old male sustains a closed femoral shaft fracture. Forty-eight hours later, he develops confusion, petechiae over the axilla, and a PaO2 of 55 mmHg. What is the primary pathophysiological mechanism responsible for his hypoxemia?

Explanation

The hypoxemia in fat embolism syndrome is primarily due to a secondary inflammatory cascade causing endothelial damage, acute respiratory distress syndrome (ARDS), and resulting V/Q mismatch with right-to-left shunting. It is not merely a mechanical occlusion by fat globules.

Question 23

Failure of a modular total hip arthroplasty at the head-neck junction often involves crevice corrosion. Which of the following initiates this specific type of corrosion in orthopedic implants?

Explanation

Crevice corrosion is initiated by the localized depletion of oxygen within the fluid restricted inside the crevice. This creates an anodic, acidic environment compared to the oxygen-rich surface outside, driving metal dissolution.

Question 24

Which of the following correctly pairs the receptor and its specific cellular location during the physiological process of osteoclast activation?

Explanation

Receptor Activator of Nuclear factor Kappa-B (RANK) is located on the surface of osteoclasts and their precursors. Its ligand, RANKL, is expressed on the surface of osteoblasts and stromal cells.

Question 25

In a clinical trial evaluating a novel fracture fixation device, investigators conclude there is no difference in union rates compared to standard plating (p = 0.15). However, a true difference exists in the population, representing a Type II error. Which parameter is mathematically defined as 1 minus the probability of a Type II error?

Explanation

Statistical power is defined as the probability of correctly rejecting the null hypothesis when it is false. It is mathematically calculated as 1 minus Beta (the probability of committing a Type II error).

Question 26

On a standard stress-strain curve representing the mechanical behavior of cortical bone, what does the slope of the linear elastic region represent?

Explanation

The slope of the linear elastic region on a stress-strain curve represents Young's modulus of elasticity. This value denotes the intrinsic stiffness of the material.

Question 27

A 68-year-old man requires an elective total hip arthroplasty and is taking warfarin for a mechanical heart valve. He is bridged with therapeutic low-molecular-weight heparin (LMWH). To minimize the risk of epidural hematoma, when is the most appropriate time to administer the last dose of therapeutic LMWH prior to neuraxial anesthesia?

Explanation

Guidelines strongly recommend withholding therapeutic doses of LMWH for at least 24 hours prior to the placement of a neuraxial block to mitigate the risk of a spinal or epidural hematoma.

Question 28

Primary bone healing (osteonal reconstruction) is desired in the rigid fixation of articular fractures. Which biomechanical environment is absolutely required for primary bone healing to occur?

Explanation

Primary bone healing occurs via cutting cones and requires absolute stability with an interfragmentary strain of less than 2%. Higher strains lead to secondary bone healing with callus formation or nonunion.

Question 29

A 28-year-old athlete sustains a traction injury to the brachial plexus. Examination reveals profound weakness in shoulder abduction and external rotation, but normal internal rotation and adduction. Sensation is diminished over the lateral deltoid. Which neural structure is most likely injured?

Explanation

The clinical picture describes Erb's palsy, caused by an injury to the upper trunk of the brachial plexus (C5-C6). This affects the suprascapular, axillary, and musculocutaneous nerves, leading to loss of abduction and external rotation.

Question 30

An orthopaedic surgeon identifies 100 patients who developed a deep surgical site infection following spine surgery and compares them to 300 similar patients who did not develop an infection. The surgeon retrospectively reviews their charts to determine the frequency of poorly controlled diabetes in each group. What type of study design is this?

Explanation

This is a case-control study. The investigator groups patients based on the outcome (infection vs. no infection) first, and then looks backward to assess for prior exposure (diabetes).

Question 31

A 70-year-old female is recovering from a total knee arthroplasty. On post-operative day 5, she develops a confirmed deep vein thrombosis and her platelet count drops from 250,000 to 90,000. She is currently on subcutaneous unfractionated heparin. What is the most appropriate immediate pharmacological management?

Explanation

The patient has developed heparin-induced thrombocytopenia (HIT). All heparin products (including LMWH) must be stopped immediately, and anticoagulation should be continued with a non-heparin agent such as a direct thrombin inhibitor (e.g., argatroban) or fondaparinux.

Question 32

A surgeon utilizes a processed freeze-dried cortical allograft strut for structural support in a revision hip arthroplasty. Which of the following biological properties does this graft inherently possess?

Explanation

Freeze-dried cortical allografts provide a structural scaffold for host cells to populate, meaning they are osteoconductive. The processing kills viable cells (loss of osteogenesis) and denatures most proteins like BMPs (severe loss of osteoinduction).

Question 33

A 55-year-old woman with a history of celiac disease presents with diffuse bone pain. Radiographs demonstrate bilateral symmetrical pseudofractures (Looser zones) in the femoral neck. Laboratory tests reveal hypocalcemia, hypophosphatemia, and elevated alkaline phosphatase. What is the most likely diagnosis?

Explanation

The presence of Looser zones (pseudofractures) combined with hypocalcemia, hypophosphatemia, and elevated alkaline phosphatase is the classic biochemical and radiographic profile of osteomalacia, often driven by severe Vitamin D deficiency.

Question 34

A 42-year-old man presents with a right-sided L5 radiculopathy due to a herniated nucleus pulposus. Which physical examination finding is most specific for an isolated L5 nerve root compression?

Explanation

The L5 nerve root primarily innervates the extensor hallucis longus, leading to weakness in great toe extension when compressed. The Achilles reflex and lateral foot sensation are S1, while the patellar reflex is primarily L4.

Question 35

A 29-year-old male with sickle cell disease presents with acute osteomyelitis of the humeral diaphysis. While Staphylococcus aureus is the most common organism overall, which of the following organisms is disproportionately responsible for osteomyelitis in this specific patient population?

Explanation

Patients with sickle cell disease have a uniquely high risk for Salmonella osteomyelitis due to autosplenectomy, microinfarcts in the bowel leading to bacteremia, and expansion of the medullary space.

Question 36

In skeletal muscle physiology, the initiation of contraction occurs when intracellular calcium levels rise. To which specific molecular structure does calcium directly bind to facilitate the cross-bridge cycle?

Explanation

Calcium released from the sarcoplasmic reticulum binds directly to Troponin C. This binding causes a conformational change that moves tropomyosin away from the myosin-binding sites on the actin filament, allowing contraction to occur.

Question 37

A randomized trial investigates a new drug to prevent deep vein thrombosis (DVT) after pelvic trauma. The incidence of DVT in the control group is 15%, while the incidence in the treatment group is 5%. What is the number needed to treat (NNT) to prevent one DVT?

Explanation

The absolute risk reduction (ARR) is 15% - 5% = 10% (or 0.10). The number needed to treat (NNT) is the inverse of the ARR (1 / 0.10), which equals 10.

Question 38

A new diagnostic joint aspirate test for periprosthetic joint infection is implemented in a region where the prevalence of the disease recently doubled. Assuming the intrinsic sensitivity and specificity of the test remain unchanged, which of the following statistical parameters will increase?

Explanation

Positive Predictive Value is highly dependent on disease prevalence. As the prevalence of a disease increases in a population, the PPV increases and the Negative Predictive Value (NPV) decreases, while sensitivity and specificity remain constant.

Question 39

A 68-year-old man undergoes a total knee arthroplasty. To minimize intraoperative and postoperative blood loss, intravenous tranexamic acid (TXA) is administered. What is the precise mechanism of action of this pharmacological agent?

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It reversibly binds to the lysine receptor sites on plasminogen, thereby preventing plasmin from binding to and degrading fibrin.

Question 40

A patient experiences a profound motor deficit in the extremity without significant sensory loss after the use of a pneumatic tourniquet for 140 minutes during upper limb reconstructive surgery. What is the primary pathophysiological mechanism responsible for this nerve injury?

Explanation

Tourniquet-induced nerve palsy is primarily caused by direct mechanical compression and deformation of the nerve beneath the cuff, with the highest shear forces occurring at the proximal and distal edges.

Question 41

A 35-year-old male sustains a multifragmentary diaphyseal femur fracture. The surgeon opts for a bridge plating technique to provide relative stability. According to Perren's strain theory, what range of gap strain is optimal for promoting secondary bone healing (callus formation)?

Explanation

According to Perren's strain theory, gap strain between 2% and 10% stimulates the formation of granulation tissue and cartilage, leading to secondary bone healing via endochondral ossification.

Question 42

During a biomechanical testing study, a solid cylindrical titanium rod with a radius of 2 cm is compared to another solid titanium rod with a radius of 4 cm. Assuming identical length and loading conditions, how much stiffer in bending is the larger rod compared to the smaller one?

Explanation

The area moment of inertia for a solid cylinder, which dictates bending stiffness, is proportional to the radius to the fourth power (r^4). Doubling the radius (from 2 cm to 4 cm) increases the bending stiffness by a factor of 16.

Question 43

A randomized controlled trial evaluating a new nonsteroidal anti-inflammatory drug for knee osteoarthritis reports a p-value of 0.03, leading researchers to conclude it is superior to placebo. If the drug is actually no more effective than placebo in reality, what type of statistical error has occurred?

Explanation

A Type I error (alpha error) occurs when the null hypothesis is incorrectly rejected, meaning a difference is declared when none truly exists (a false positive).

Question 44

During anterior cruciate ligament reconstruction, the graft is tensioned and secured. Over time, the surgeon notes that the tension required to hold the graft at a constant length decreases. Which viscoelastic property does this phenomenon represent?

Explanation

Stress relaxation is a viscoelastic property where a material held at a constant length or strain experiences a gradual decrease in internal stress (and thus tension) over time.

Question 45

A 22-year-old athlete undergoes skeletal muscle biopsy for a metabolic study. In the process of normal skeletal muscle contraction, intracellular calcium release triggers cross-bridge cycling by directly binding to which of the following molecules?

Explanation

During muscle contraction, calcium ions released from the sarcoplasmic reticulum bind to Troponin C. This causes a conformational change that moves tropomyosin away from the myosin-binding sites on the actin filament.

Question 46

A 45-year-old man requires an urgent open reduction and internal fixation for a closed tibia plateau fracture. He has a documented history of severe anaphylaxis to penicillin. Which of the following is the most appropriate perioperative prophylactic antibiotic regimen?

Explanation

In patients with a severe (IgE-mediated) allergy to penicillin, cephalosporins should be avoided due to the risk of cross-reactivity. Clindamycin or Vancomycin are the standard recommended alternatives for orthopedic surgical prophylaxis.

Question 47

A therapeutic orthopedic study is designed as a high-quality prospective cohort study comparing clinical outcomes of operative versus nonoperative treatment for Achilles tendon ruptures without randomizing the patients. Based on the hierarchy of evidence-based medicine, what level of evidence does this study provide?

Explanation

A high-quality prospective cohort study (where patients are tracked forward in time but not randomized) provides Level II evidence for therapeutic questions.

Question 48

A 28-year-old male sustains a massive segmental bone defect of the radius and receives a structural cortical allograft. During the physiological process of creeping substitution, what is the initial cellular phase that the cortical graft undergoes?

Explanation

Unlike cancellous bone grafts which heal initially by osteoblastic apposition, cortical bone grafts undergo osteoclastic resorption first, creating cutting cones before new bone is laid down, temporarily making the graft weaker.

Question 49

A 19-year-old male undergoing general anesthesia for an open femur fracture suddenly exhibits unexplained tachycardia, generalized muscle rigidity, and a rapidly rising end-tidal CO2. If malignant hyperthermia is suspected, what is the primary pathophysiologic defect?

Explanation

Malignant hyperthermia is a pharmacogenetic disorder typically caused by a mutation in the ryanodine receptor (RYR1) on the sarcoplasmic reticulum, leading to uncontrolled, massive calcium release into the myoplasm.

Question 50

A meta-analysis investigates the association between smoking and tibial nonunion. The pooled Relative Risk (RR) is reported as 2.8, with a 95% Confidence Interval (CI) of [0.9, 4.7]. What is the correct interpretation of these statistical findings?

Explanation

For ratio measures such as Relative Risk or Odds Ratio, a 95% confidence interval that includes 1.0 indicates that there is no statistically significant difference between the groups at the 0.05 alpha level.

Question 51

A 30-year-old woman presents with persistent radial-sided wrist pain two weeks after a FOOSH injury. Initial and repeat radiographs are entirely normal. Which magnetic resonance imaging (MRI) sequence is most sensitive for detecting early, radiographically occult bone marrow edema indicative of a scaphoid fracture?

Explanation

STIR and T2 fat-suppressed MRI sequences suppress the high signal from normal marrow fat, making the bright signal of interstitial water (bone marrow edema) highly conspicuous and sensitive for occult fractures.

Question 52

An infection control committee reviews a new silver-impregnated surgical dressing designed to prevent deep surgical site infections. A robust trial shows the absolute risk reduction (ARR) of infection using this dressing is 4% (0.04). What is the Number Needed to Treat (NNT) to prevent one additional infection?

Explanation

The Number Needed to Treat (NNT) is calculated as 1 divided by the Absolute Risk Reduction (ARR). Therefore, 1 / 0.04 equals 25.

Question 53

During a complex revision total hip arthroplasty, a surgeon utilizes a 316L stainless steel screw to secure a titanium alloy acetabular component. Which of the following complications is most likely to occur at the interface of these two metals?

Explanation

Galvanic corrosion occurs when two macroscopic metals with different electrochemical potentials (e.g., stainless steel and titanium) are placed in direct contact within an electrolytic medium (body fluids), causing the less noble metal to corrode.

Question 54

A 70-year-old patient is prescribed Rivaroxaban for deep vein thrombosis prophylaxis following a total knee arthroplasty. What is the precise molecular target of this medication?

Explanation

Rivaroxaban and apixaban are oral anticoagulants that exert their effect by directly and reversibly inhibiting Factor Xa, preventing the conversion of prothrombin to thrombin.

Question 55

A 55-year-old woman is being evaluated for metabolic bone disease. Her laboratory workup includes normal serum calcium, normal phosphorus, and normal parathyroid hormone levels, but an elevated bone-specific alkaline phosphatase. What does this specific marker primarily indicate?

Explanation

Bone-specific alkaline phosphatase and osteocalcin are biochemical markers of bone formation, reflecting active osteoblastic activity. Markers like N-telopeptide (NTx) and C-telopeptide (CTx) reflect osteoclastic bone resorption.

Question 56

A researcher is studying the mechanical properties of cortical bone. On a standard stress-strain curve representing the tensile testing of a bone specimen, what term defines the exact point where the material transitions from elastic deformation to permanent plastic deformation?

Explanation

The yield point marks the end of elastic (reversible) deformation and the beginning of plastic (irreversible) deformation on a stress-strain curve. Loading beyond this point results in permanent structural changes.

Question 57

A 40-year-old patient is evaluated for an unhealed tibial shaft fracture 8 months after cast immobilization. The surgeon plans an operation. To ensure primary (osteonal) bone healing without callus formation, what biomechanical environment must the surgical construct provide?

Explanation

Primary (osteonal) bone healing occurs without callus formation and requires absolute stability (gap strain <2%) and intimate contact, typically achieved through lag screw fixation and compression plating.

Question 58

A 25-year-old man with bilateral femur fractures develops sudden confusion, severe hypoxia, and a non-blanching rash on his chest 36 hours post-injury. According to Gurd's diagnostic criteria, which of the following is considered a major criterion for this condition?

Explanation

Gurd's major criteria for fat embolism syndrome include petechial rash, respiratory insufficiency, and cerebral involvement (confusion/coma). Tachycardia, fever, and thrombocytopenia are considered minor criteria.

Question 59

A 65-year-old woman is prescribed rivaroxaban for deep vein thrombosis prophylaxis following an elective total knee arthroplasty. What is the specific mechanism of action of this pharmacological agent?

Explanation

Rivaroxaban and apixaban are oral direct Factor Xa inhibitors used for VTE prophylaxis. Dabigatran is a direct thrombin inhibitor, while warfarin acts as a Vitamin K antagonist.

Question 60

A new diagnostic immunoassay for periprosthetic joint infection is evaluated. If the prevalence of periprosthetic joint infection in the tested hospital population significantly increases over time, how are the positive predictive value (PPV) and negative predictive value (NPV) affected?

Explanation

Predictive values are highly dependent on disease prevalence. As prevalence increases, a positive result is more likely to be a true positive (increased PPV), while a negative result is less likely to be a true negative (decreased NPV).

Question 61

A 72-year-old man on chronic warfarin therapy for atrial fibrillation presents with a closed, displaced femoral neck fracture. His admission INR is 3.8. He requires urgent surgical fixation within 24 to 48 hours. What is the most effective and rapid pharmacological method to reverse his coagulopathy?

Explanation

Prothrombin complex concentrate (PCC) provides immediate reversal of warfarin-induced coagulopathy by replacing factors II, VII, IX, and X. Vitamin K is co-administered to sustain the reversal as the PCC half-life is relatively short.

Question 62

A 55-year-old man with poorly controlled type 2 diabetes is scheduled for an elective lumbar spinal fusion. He is counseled extensively on the risk of surgical site infection (SSI). What is the generally accepted preoperative HbA1c threshold above which most elective orthopedic surgeries should be delayed?

Explanation

Current orthopedic guidelines recommend delaying elective joint and spine surgeries if the patient's HbA1c is 8.0% or higher. Values above this threshold are independently associated with a significantly increased risk of surgical site infections and poor wound healing.

Question 63

A 45-year-old woman presents with sudden onset pleuritic chest pain and dyspnea 2 weeks after an ORIF of a tibial plateau fracture. Her ECG shows an S1Q3T3 pattern. What is the next best step for definitive confirmation of her suspected diagnosis?

Explanation

The clinical presentation and classic ECG findings suggest a pulmonary embolism. CT pulmonary angiography (CTPA) is the gold standard imaging modality for definitive diagnosis in a hemodynamically stable patient.

Question 64

A 30-year-old man undergoes shoulder arthroscopy under general anesthesia. Thirty minutes into the case, he develops masseter spasm, unexplained tachycardia, and a sharply rising end-tidal CO2. What is the underlying pathophysiology of this life-threatening condition?

Explanation

The patient is experiencing malignant hyperthermia, triggered by volatile anesthetics or succinylcholine. It is caused by a mutation in the ryanodine receptor (RYR1), leading to massive uncontrolled calcium release from the sarcoplasmic reticulum.

Question 65

A 60-year-old woman sustains a distal radius fracture treated with closed reduction and casting. Which of the following daily oral supplements has the highest level of evidence for reducing her risk of developing Complex Regional Pain Syndrome (CRPS)?

Explanation

Vitamin C (typically 500 mg daily for 50 days) has been shown in randomized trials to reduce the incidence of CRPS following distal radius fractures. It acts as an antioxidant mitigating the excessive inflammatory response.

Question 66

A 28-year-old man is post-operative day 1 following intramedullary nailing of a closed tibia fracture. His temperature is 38.2°C. His lungs are clear, the wound is clean, and there is no excessive calf swelling. What is the most likely cause of his fever?

Explanation

Low-grade fever within the first 24-48 hours after major orthopedic trauma or surgery is extremely common and usually represents a normal cytokine-mediated inflammatory response to tissue injury. Early post-operative fever is rarely due to surgical site infection.

Question 67

To appropriately minimize the risk of surgical site infection in a primary total hip arthroplasty, standard prophylactic intravenous antibiotics (e.g., Cefazolin) should ideally be completely infused within what timeframe?

Explanation

Clinical guidelines dictate that prophylactic antibiotics must be fully administered within 60 minutes prior to the surgical incision to ensure optimal tissue concentration at the time of initial exposure. Vancomycin or fluoroquinolones may require a 120-minute window due to longer infusion times.

Question 68

During bone graft incorporation, creeping substitution describes the process by which a graft is resorbed and replaced by host bone. Which of the following graft types relies entirely on creeping substitution and osteoconduction, completely lacking live osteogenic cells?

Explanation

Cortical allografts lack live cells and incorporate purely via osteoconduction and creeping substitution, which can be a prolonged process taking months to years. Autografts retain living osteocytes and osteoblasts, conferring osteogenic properties.

Question 69

An orthopedic researcher wants to investigate the association between a rare primary bone malignancy (e.g., osteosarcoma) and a specific prior environmental exposure. Which epidemiological study design is the most appropriate and efficient for this scenario?

Explanation

A case-control study is the most efficient design for evaluating rare diseases. It retrospectively compares previous exposures between a group with the disease (cases) and a group without the disease (controls).

Question 70

A 68-year-old man is scheduled for an elective total knee arthroplasty. He has a history of an uncomplicated myocardial infarction exactly 3 weeks ago and is currently asymptomatic. What is the best preoperative recommendation regarding his surgery timing?

Explanation

According to ACC/AHA guidelines, elective non-cardiac surgery should be delayed for at least 60 days following a myocardial infarction in the absence of coronary intervention. Operating within this window dramatically increases perioperative mortality.

Question 71

A 35-year-old man sustains an unstable pelvic ring fracture in a high-speed motor vehicle collision. On arrival, his BP is 85/50 mmHg, HR is 135 bpm, and his urine output is negligible. Into which class of hemorrhagic shock does this patient fall, and what is his estimated blood volume loss?

Explanation

The patient is in Class III hemorrhagic shock, characterized by a drop in measurable blood pressure, tachycardia (120-140 bpm), and decreased urine output. This correlates with a 30-40% loss of blood volume, or roughly 1500-2000 mL in an average adult.

Question 72

A 22-year-old man with an acute, closed tibia fracture develops disproportionate leg pain, swelling, and paresthesia. Intracompartmental pressure is measured. Which of the following values definitively confirms an acute compartment syndrome necessitating emergency fasciotomy?

Explanation

Acute compartment syndrome is definitively diagnosed when the delta pressure (diastolic blood pressure minus intracompartmental pressure) falls below 30 mmHg. Relying on absolute pressure alone can lead to overtreatment or missed diagnosis depending on the patient's systemic blood pressure.

Question 73

A 40-year-old woman undergoes prolonged pelvic surgery in the lithotomy position. Post-operatively, she complains of numbness over the anterolateral aspect of her leg and the dorsum of her foot, accompanied by a foot drop. Which nerve was most likely injured due to poor positioning?

Explanation

The common peroneal nerve is highly vulnerable to compression against the fibular head when the patient is in the lithotomy position. Injury results in foot drop (loss of dorsiflexion) and sensory loss over the anterolateral leg and dorsum of the foot.

Question 74

A new clinical test for detecting meniscal tears is evaluated in a population of 1000 patients. MRI confirms that 100 patients truly have a meniscal tear. The new test is positive in 90 of the patients with a tear, and positive in 90 of the patients without a tear. What is the Positive Predictive Value (PPV) of this new test?

Explanation

PPV is the proportion of true positives among all positive results [TP / (TP + FP)]. Here, TP = 90 and FP = 90, making the calculation 90 / 180 = 50%.

Question 75

A randomized controlled trial comparing two total knee arthroplasty designs concludes there is no significant difference in 10-year survivorship (p = 0.15). However, independent registry data later definitively proves a significant difference truly exists in the population. What statistical error occurred in the trial?

Explanation

A Type II (beta) error occurs when a study fails to reject a false null hypothesis (i.e., failing to detect a difference that truly exists). It is usually caused by an inadequate sample size and lack of statistical power.

Question 76

A 24-year-old man sustains a closed femoral shaft fracture. 48 hours later, he develops acute confusion, tachypnea, and a petechial rash over his anterior chest and axillae. Which of the following is the most definitive primary preventative strategy for this patient's condition?

Explanation

The patient has clinical signs of Fat Embolism Syndrome (FES). Early operative stabilization (within 24 hours) of long bone fractures is the most effective proven method for reducing the incidence and severity of FES.

Question 77

An 80-year-old woman undergoes urgent hemiarthroplasty for a displaced femoral neck fracture. Her past medical history is significant for end-stage renal disease (eGFR 12 mL/min). Which of the following deep vein thrombosis (DVT) prophylaxis regimens is most appropriate?

Explanation

Unfractionated heparin is not renally cleared and is considered safe in patients with severe renal impairment (eGFR < 15 mL/min). Low-molecular-weight heparins (like enoxaparin) and most NOACs require strict renal dose adjustment or are entirely contraindicated.

Question 78

A researcher is evaluating an orthopedic implant made of a titanium alloy. During mechanical testing, the material is loaded into its elastic range and held at a constant strain. Over time, the internal force within the material progressively decreases. What biomechanical phenomenon does this describe?

Explanation

Stress relaxation is a viscoelastic property where the stress (internal force) decreases over time when a material is held at a constant strain (deformation). Creep, conversely, is an increase in strain under constant stress.

Question 79

During a revision hip arthroplasty, the surgeon notes severe osteolysis around a well-fixed cementless acetabular component with significant polyethylene wear. Which of the following cell types is the primary direct effector of the bone resorption in this process?

Explanation

While macrophages phagocytose particulate debris and release pro-inflammatory cytokines (like TNF-alpha and IL-1), the osteoclast is the final common pathway and the primary cell responsible for directly resorbing the bone.

Question 80

A 35-year-old woman develops acute shortness of breath and hypotension 3 days after internal fixation of a pelvic ring injury. A massive pulmonary embolism is suspected. Which of the following electrocardiogram (ECG) findings, though not the most common, is classically associated with right ventricular strain in this condition?

Explanation

The S1Q3T3 pattern (prominent S wave in lead I, Q wave and inverted T wave in lead III) is a classic sign of acute right ventricular strain or cor pulmonale due to a pulmonary embolism, although sinus tachycardia is the most common overall ECG finding.

Question 81

Normal articular cartilage is divided into distinct structural zones. Which zone contains the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibers oriented perpendicular to the joint surface?

Explanation

The deep (radial) zone has the highest proteoglycan content, the lowest water content, and thick collagen fibrils arranged perpendicular to the articular surface to resist compressive loads.

Question 82

Denosumab is a monoclonal antibody utilized in the treatment of osteoporosis and giant cell tumor of bone. It exerts its clinical effect by binding directly to which of the following molecular targets?

Explanation

Denosumab binds directly to RANKL, preventing it from interacting with RANK on the surface of osteoclasts and their precursors. This mechanism effectively mimics the natural inhibitory action of Osteoprotegerin (OPG).

Question 83

A prospective cohort study is designed to evaluate the risk of postoperative surgical site infection following spinal fusion in diabetic versus non-diabetic patients. Which of the following statistical measures is most appropriate to report the strength of association in this specific study design?

Explanation

Relative risk (RR) is the appropriate measure of association for cohort studies, comparing the incidence of disease in exposed versus unexposed groups. Odds ratios are typically used in case-control studies.

Question 84

During primary bone healing following rigid plate fixation (absolute stability), healing occurs primarily without cartilaginous callus formation via Haversian remodeling. Which of the following best describes the cellular arrangement of the 'cutting cone' mechanism?

Explanation

In the cutting cone of primary cortical bone healing, osteoclasts are situated at the front (leading edge) to resorb dead bone, followed closely by osteoblasts at the rear (trailing edge) which lay down new osteoid to form Haversian systems.

Question 85

A 65-year-old man requires an emergency open reduction and internal fixation for a highly displaced, open tibia fracture with vascular compromise. He chronically takes warfarin for atrial fibrillation and his current INR is 4.5. Which of the following provides the most rapid and effective reversal of his anticoagulation?

Explanation

Prothrombin complex concentrate (PCC) provides the most rapid, low-volume reversal of Vitamin K antagonists (warfarin) by supplying concentrated factors II, VII, IX, and X. IV Vitamin K is given concurrently to sustain the reversal once the PCC half-life wanes.

Question 86

Tranexamic acid (TXA) is commonly utilized to reduce perioperative blood loss in major orthopedic procedures. What is its primary mechanism of action?

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It reversibly binds to plasminogen, competitively inhibiting its activation into plasmin, thereby preventing the degradation of fibrin clots (antifibrinolytic effect).

Question 87

A biomechanical evaluation of a new synthetic ligament reveals that the material becomes stiffer as the rate of applied tension increases. This time- and rate-dependent material behavior is best described as:

Explanation

Viscoelastic materials exhibit time- and rate-dependent behavior, meaning their mechanical response (like stiffness) changes depending on how fast the load is applied. Normal ligaments and tendons are naturally viscoelastic.

Question 88

During the normal human gait cycle, which muscle or muscle group undergoes an essential eccentric contraction during the initial contact (heel strike) to loading response phase to prevent a 'foot slap' mechanism?

Explanation

The tibialis anterior contracts eccentrically (lengthens under tension) immediately following heel strike to decelerate plantarflexion and gently lower the forefoot to the ground, preventing 'foot slap'.

Question 89

Galvanic corrosion is an electrochemical process that occurs when two dissimilar metals are placed in physical contact within a conductive fluid environment. Which of the following metal combinations is highly susceptible to this specific type of corrosion and generally avoided in orthopedics?

Explanation

Mixing titanium alloys with stainless steel implants (e.g., a stainless steel screw in a titanium plate) in a physiological environment creates a strong electrochemical gradient, leading to rapid galvanic corrosion and potential hardware failure.

Question 90

A 22-year-old male with a severe traumatic brain injury (TBI) and a closed midshaft femur fracture undergoes intramedullary nailing. Which of the following statements is true regarding fracture healing in patients with concomitant severe TBI?

Explanation

Patients with severe traumatic brain injuries exhibit an accelerated osteogenic response, resulting in a significantly increased volume of fracture callus, faster union times, and a high risk of heterotopic ossification due to circulating humoral osteogenic factors.

Question 91

The organic extracellular matrix of normal hyaline articular cartilage is specifically designed to resist both tensile and compressive loads. Which type of collagen constitutes the vast majority (90-95%) of this collagenous matrix?

Explanation

Type II collagen makes up 90-95% of the collagen in hyaline articular cartilage. Type I collagen is primarily found in bone, tendon, meniscus, and the annulus fibrosus. Type X is associated with the calcified cartilage zone and hypertrophic chondrocytes.

Question 92

A randomized controlled trial is proposed to compare sling immobilization versus operative fixation for displaced midshaft clavicle fractures. The researchers want a 90% probability of detecting a clinically significant difference if one truly exists, with the alpha level set at 0.05. The 90% parameter refers to the study's:

Explanation

Statistical power (1 - beta) is the probability that a study will correctly reject a false null hypothesis, effectively meaning the study's ability to detect a true difference if one exists. A power of 80% to 90% is typically desired.

Orthopedic Prometric MCQs - Chapter 4 Part 1

Orthopedic Prometric MCQs - Chapter 4 Part 1

Detailed Chapters & Topics

Orthopedic Prometric MCQs - Chapter 4 Part 2

Orthopedic Prometric MCQs - Chapter 4 Part 3

Orthopedic Prometric MCQs - Chapter 4 Part 4

Orthopedic Prometric MCQs - Chapter 4 Part 5

Orthopedic Prometric MCQs - Chapter 4 Part 6

Orthopedic Prometric MCQs - Chapter 4 Part 7

Orthopedic Prometric MCQs - Chapter 4 Part 8

Orthopedic Prometric MCQs - Chapter 4 Part 9

Orthopedic Prometric MCQs - Chapter 4 Part 10

Orthopedic Prometric MCQs - Chapter 4 Part 11

Guide Overview