Orthopaedics & MSK — MCQs
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A 56-year-old woman presents with a 4-month history of lower back pain and progressive bilateral leg weakness. She reports difficulty walking upstairs and recent episodes of urinary hesitancy. Neurological examination reveals bilateral lower limb weakness (power 4/5 in hip flexion and knee extension bilaterally), diminished ankle reflexes, and a post-void residual bladder volume of 250ml. What is the most appropriate immediate management?
A 74-year-old woman undergoes surgical fixation for a Garden II intracapsular neck of femur fracture with three cannulated screws inserted in an inverted triangle configuration. Post-operatively, she is noted to have a shortened leg length compared to the contralateral side despite satisfactory screw positioning on radiographs. What is the most likely mechanism responsible for this complication?
A 69-year-old man presents to the Emergency Department with a 72-hour history of progressively worsening lower back pain. He describes the pain as severe and unrelenting, not relieved by rest or analgesia. He has a past medical history of chronic obstructive pulmonary disease for which he takes oral prednisolone 10mg daily. On examination, he is pyrexial at 38.2°C and has marked tenderness over the L3-L4 vertebrae. What is the most appropriate initial investigation to exclude the most likely diagnosis?
A 71-year-old woman sustains a neck of femur fracture following a fall. On examination, the affected leg is shortened and externally rotated. Radiographs confirm an extracapsular fracture. Which anatomical landmark best distinguishes intracapsular from extracapsular neck of femur fractures?
A 58-year-old man with metastatic prostate cancer presents with a 4-week history of progressive lower back pain and new onset bilateral lower limb weakness. MRI shows a pathological fracture of L2 vertebra with retropulsion of bone fragments causing significant spinal canal compromise and spinal cord compression. He has motor power 3/5 in both legs. What is the most appropriate initial management?
A 67-year-old woman underwent total hip replacement for a displaced intracapsular neck of femur fracture 18 hours ago. She suddenly becomes confused and agitated, with worsening hypoxia (oxygen saturation 85% on 4L oxygen). Arterial blood gas shows: pH 7.32, PaO2 7.8 kPa, PaCO2 4.2 kPa, lactate 2.8 mmol/L. Chest radiograph shows bilateral diffuse infiltrates. What is the most likely diagnosis?
A 42-year-old office worker presents with a 10-week history of lower back pain radiating down the posterior aspect of his right leg to the lateral aspect of his foot. He has reduced sensation over the lateral aspect of his foot and weakness of plantarflexion. Straight leg raise is positive at 40 degrees on the right. Which nerve root is most likely affected?
A 77-year-old woman is being consented for cemented hemiarthroplasty for a displaced intracapsular neck of femur fracture. She asks about the risks of the procedure. According to the National Hip Fracture Database and published literature, what is the approximate 30-day mortality rate following surgical treatment of hip fracture in the UK?
A 54-year-old man with a 20-year history of ankylosing spondylitis presents to the Emergency Department after a minor fall. He reports severe neck pain and is protecting his cervical spine. He has no neurological deficit. What is the most appropriate initial imaging investigation?
A 68-year-old man underwent dynamic hip screw fixation for a stable two-part intertrochanteric fracture 4 months ago. He now presents with persistent groin pain on weight-bearing and difficulty mobilizing. Radiographs show the lag screw has migrated laterally through the femoral head with loss of fixation. What is the most likely mechanism responsible for this complication?
Orthopaedics & MSK UK Medical PG Practice Questions and MCQs
Question 31: A 56-year-old woman presents with a 4-month history of lower back pain and progressive bilateral leg weakness. She reports difficulty walking upstairs and recent episodes of urinary hesitancy. Neurological examination reveals bilateral lower limb weakness (power 4/5 in hip flexion and knee extension bilaterally), diminished ankle reflexes, and a post-void residual bladder volume of 250ml. What is the most appropriate immediate management?
- A. Urgent MRI lumbar spine and referral to spinal surgery (Correct Answer)
- B. Commence pregabalin and arrange outpatient physiotherapy
- C. Prescribe high-dose non-steroidal anti-inflammatory drugs and review in 2 weeks
- D. Arrange routine MRI lumbar spine within 6 weeks
- E. Refer to urology for management of urinary retention
Explanation: ***Urgent MRI lumbar spine and referral to spinal surgery***- The patient presents with **red flag symptoms** for **Cauda Equina Syndrome (CES)**, including progressive bilateral leg weakness, diminished ankle reflexes, and bladder dysfunction (urinary hesitancy and high **post-void residual** volume). - **Immediate MRI** is essential to confirm the diagnosis and locate the compression, followed by urgent **surgical decompression** to prevent permanent neurological deficits. *Commence pregabalin and arrange outpatient physiotherapy* - These interventions are appropriate for managing chronic neuropathic pain or musculoskeletal issues, but not for an acute **neurological emergency** like suspected CES. - Delaying definitive diagnosis and treatment with conservative measures risks irreversible **spinal cord damage** and **bladder/bowel dysfunction**. *Prescribe high-dose non-steroidal anti-inflammatory drugs and review in 2 weeks* - **NSAIDs** are indicated for inflammatory or mechanical back pain, but they do not address the **nerve root compression** causing the neurological deficits. - A **2-week review** period is unacceptable given the rapid progression and potential for permanent harm in CES, which demands immediate action. *Arrange routine MRI lumbar spine within 6 weeks* - A **routine MRI** timeframe is for patients with stable symptoms or those being investigated for chronic conditions without acute neurological deterioration. - Suspected CES necessitates an **emergency MRI** (ideally within hours) to assess for spinal compression, as rapid intervention is critical for prognosis. *Refer to urology for management of urinary retention* - The **urinary retention** is a symptom of **neurogenic bladder dysfunction** due to **cauda equina compression**, not a primary urological problem. - Focusing solely on urological management without addressing the underlying spinal pathology would delay crucial intervention and lead to ongoing and potentially permanent neurological damage.
Question 32: A 74-year-old woman undergoes surgical fixation for a Garden II intracapsular neck of femur fracture with three cannulated screws inserted in an inverted triangle configuration. Post-operatively, she is noted to have a shortened leg length compared to the contralateral side despite satisfactory screw positioning on radiographs. What is the most likely mechanism responsible for this complication?
- A. Inadequate screw length resulting in incomplete fracture reduction
- B. Collapse at the fracture site due to loss of reduction during healing (Correct Answer)
- C. Avascular necrosis of the femoral head causing segmental collapse
- D. Posterior dislocation of the hip during positioning on the fracture table
- E. Sciatic nerve palsy causing apparent leg shortening due to flexion deformity
Explanation: ***Collapse at the fracture site due to loss of reduction during healing*** - Intracapsular neck of femur fractures fixed with **cannulated screws** are designed to allow **controlled collapse** or impaction at the fracture site, which promotes healing by compression. - In elderly patients with **osteoporotic bone**, this biological and mechanical collapse can be more pronounced, leading to **secondary shortening** despite initially satisfactory reduction and screw placement. *Inadequate screw length resulting in incomplete fracture reduction* - The question states that **screw positioning** was satisfactory on radiographs, implying correct screw length and adequate initial reduction. - **Incomplete reduction** would be an intraoperative issue, typically detected immediately, not a post-operative complication developing later with otherwise good fixation. *Avascular necrosis of the femoral head causing segmental collapse* - **Avascular necrosis (AVN)** is a known long-term complication of femoral neck fractures, but its characteristic **segmental collapse** leading to shortening usually occurs **months to years** post-surgery, not in the immediate post-operative phase. - Early post-operative shortening, especially with good initial fixation, is more indicative of mechanical failure or impaction at the fracture site rather than the progression of AVN. *Posterior dislocation of the hip during positioning on the fracture table* - A **posterior hip dislocation** is an acute event, presenting with a distinct clinical picture of a shortened, **internally rotated**, and **adducted** limb, and would be immediately evident on post-operative imaging. - This mechanism is inconsistent with a situation where screw positioning is satisfactory and shortening is noted post-operatively as a complication of the fracture healing process. *Sciatic nerve palsy causing apparent leg shortening due to flexion deformity* - **Sciatic nerve palsy** causes neurological deficits like **foot drop** and sensory loss, and does not directly cause anatomical bone shortening at the fracture site. - While a severe **flexion deformity** can cause apparent shortening, it is a functional issue and not the primary mechanism for true anatomical leg length discrepancy after a well-fixed femoral neck fracture.
Question 33: A 69-year-old man presents to the Emergency Department with a 72-hour history of progressively worsening lower back pain. He describes the pain as severe and unrelenting, not relieved by rest or analgesia. He has a past medical history of chronic obstructive pulmonary disease for which he takes oral prednisolone 10mg daily. On examination, he is pyrexial at 38.2°C and has marked tenderness over the L3-L4 vertebrae. What is the most appropriate initial investigation to exclude the most likely diagnosis?
- A. Plain radiographs of the lumbar spine
- B. CT scan of the lumbar spine
- C. MRI scan of the lumbar spine (Correct Answer)
- D. Blood cultures and inflammatory markers
- E. Bone scan with technetium-99m
Explanation: ***MRI scan of the lumbar spine*** - The patient's presentation with **progressively worsening, unrelenting lower back pain**, **pyrexia**, **localized tenderness**, and a history of **chronic oral prednisolone use (immunosuppression)** is highly suggestive of **spinal infection** (e.g., discitis or vertebral osteomyelitis). - **MRI with gadolinium contrast** is the **gold standard** investigation for diagnosing spinal infections, offering superior visualization of **vertebral marrow edema**, **disc space involvement**, and **epidural abscess formation**. *Plain radiographs of the lumbar spine* - Plain radiographs have **low sensitivity** for detecting early spinal infections, with changes typically appearing **2-4 weeks after symptom onset**. - They cannot adequately visualize **soft tissue involvement** or early inflammatory changes in the vertebral marrow, which are critical for diagnosis. *CT scan of the lumbar spine* - While a CT scan is excellent for demonstrating **cortical bone destruction**, it is **less sensitive than MRI** for detecting early inflammatory changes in the bone marrow and soft tissues, such as discitis or epidural collections. - It is often considered when MRI is contraindicated or for surgical planning after an MRI diagnosis. *Blood cultures and inflammatory markers* - **Blood cultures** and **inflammatory markers (ESR, CRP)** are crucial for identifying the causative organism and assessing disease activity, but they are **laboratory tests**, not imaging modalities. - They are **adjunctive investigations** that support the diagnosis of infection but cannot provide the necessary anatomical localization or confirm the extent of spinal involvement. *Bone scan with technetium-99m* - A **technetium-99m bone scan** has **high sensitivity** but **poor specificity** for spinal infection, as it can be positive in various conditions like degenerative disease, trauma, or tumors. - It also offers **inferior anatomical resolution** compared to MRI, making it difficult to precisely localize the infection or differentiate it from other pathologies.
Question 34: A 71-year-old woman sustains a neck of femur fracture following a fall. On examination, the affected leg is shortened and externally rotated. Radiographs confirm an extracapsular fracture. Which anatomical landmark best distinguishes intracapsular from extracapsular neck of femur fractures?
- A. The greater trochanter
- B. The intertrochanteric line anteriorly and intertrochanteric crest posteriorly (Correct Answer)
- C. The lesser trochanter
- D. The linea aspera
- E. The subtrochanteric region
Explanation: ***The intertrochanteric line anteriorly and intertrochanteric crest posteriorly*** - The **hip joint capsule** attaches anteriorly to the **intertrochanteric line** and posteriorly to the **intertrochanteric crest**, which defines the boundary of the joint space. - Fractures occurring proximal to these landmarks are **intracapsular**, while those distal are **extracapsular**, with significant implications for **blood supply** to the femoral head. *The greater trochanter* - This is a prominent bony landmark and a site for **muscle attachments**, such as the gluteal muscles, but it does not define the capsular attachment. - Fractures involving the greater trochanter are by definition **extracapsular** but are not the primary landmark for distinguishing between neck fracture types. *The lesser trochanter* - The **lesser trochanter** is located on the posteromedial aspect of the proximal femur, serving as the insertion point for the **iliopsoas muscle**. - It is situated distal to the main capsular attachment and is more indicative of the subtrochanteric region rather than the precise intracapsular/extracapsular dividing line. *The linea aspera* - This is a rough longitudinal ridge located on the **posterior aspect of the femoral shaft**, providing attachment for various thigh muscles. - It is far too distal to the neck of the femur to be relevant in distinguishing between **intracapsular** and **extracapsular** neck fractures. *The subtrochanteric region* - This region refers to the area of the femur distal to the lesser trochanter, describing a specific type of **extracapsular fracture**. - While it is a fracture classification, it is not the anatomical landmark that delineates the boundary of the hip joint capsule itself.
Question 35: A 58-year-old man with metastatic prostate cancer presents with a 4-week history of progressive lower back pain and new onset bilateral lower limb weakness. MRI shows a pathological fracture of L2 vertebra with retropulsion of bone fragments causing significant spinal canal compromise and spinal cord compression. He has motor power 3/5 in both legs. What is the most appropriate initial management?
- A. Urgent radiotherapy within 24 hours
- B. High-dose dexamethasone and urgent radiotherapy
- C. Immediate surgical decompression and stabilization (Correct Answer)
- D. Percutaneous vertebroplasty
- E. Conservative management with analgesia and mobilization
Explanation: ***Immediate surgical decompression and stabilization*** - **Surgical decompression** is the treatment of choice in cases of **metastatic spinal cord compression (MSCC)** where there is **spinal instability** or **mechanical compression** by bone fragments (retropulsion). - It is indicated for patients with a **prognosis >3 months** and functional deficits, as it provides immediate stabilization and better functional outcomes compared to radiotherapy alone in the setting of structural collapse. *Urgent radiotherapy within 24 hours* - **Radiotherapy** is primarily used for **radio-sensitive tumors** (e.g., lymphoma, myeloma) or cases where there is no mechanical instability/bone retropulsion. - While important, it cannot address the **mechanical instability** caused by a pathological fracture or provide the immediate structural support required in this patient. *High-dose dexamethasone and urgent radiotherapy* - **Dexamethasone** should be administered immediately to reduce **vasogenic edema**; however, it is an adjunctive therapy and not the definitive management for bone fragments. - Combining this with radiotherapy is insufficient for **unstable fractures**, as it fails to rectify the **spinal canal compromise** caused by the retropulsed bone. *Percutaneous vertebroplasty* - **Vertebroplasty** is used for pain relief in stable osteoporotic or malignant vertebral fractures without neurological compromise. - It is **contraindicated** in the presence of **spinal cord compression** or bone fragments in the spinal canal, as the cement could further compromise the cord. *Conservative management with analgesia and mobilization* - **Conservative management** is inappropriate for a patient with **progressive neurological deficits** (3/5 power) and mechanical cord compression. - **Spinal cord compression** is a medical emergency that requires active intervention to prevent permanent **paraplegia** and loss of autonomic function.
Question 36: A 67-year-old woman underwent total hip replacement for a displaced intracapsular neck of femur fracture 18 hours ago. She suddenly becomes confused and agitated, with worsening hypoxia (oxygen saturation 85% on 4L oxygen). Arterial blood gas shows: pH 7.32, PaO2 7.8 kPa, PaCO2 4.2 kPa, lactate 2.8 mmol/L. Chest radiograph shows bilateral diffuse infiltrates. What is the most likely diagnosis?
- A. Aspiration pneumonia
- B. Cardiogenic pulmonary oedema
- C. Acute respiratory distress syndrome (ARDS) (Correct Answer)
- D. Pulmonary embolism with infarction
- E. Transfusion-related acute lung injury (TRALI)
Explanation: ***Acute respiratory distress syndrome (ARDS)*** - The patient's **acute severe hypoxemia**, **bilateral diffuse infiltrates** on chest X-ray, and confusion, occurring within 18 hours of **major orthopaedic surgery** for a hip fracture, are classic features of ARDS. - Severe trauma and orthopaedic surgery are significant risk factors, initiating a systemic inflammatory response that damages the **alveolar-capillary membrane**, leading to non-cardiogenic pulmonary oedema. *Aspiration pneumonia* - Typically presents with **localized infiltrates**, often in dependent lung segments like the **right lower lobe**, not the diffuse bilateral pattern seen here. - While post-operative patients are at risk, there is no mention of a witnessed aspiration event or specific risk factors like vomiting or impaired consciousness leading to aspiration. *Cardiogenic pulmonary oedema* - Although it causes **bilateral infiltrates** and hypoxemia, it usually presents with clinical signs of **fluid overload** or heart failure, such as **elevated JVP** or S3 gallop, which are absent in this case. - The context of major surgery and trauma points towards a **non-cardiogenic** cause of pulmonary oedema, unlike primary cardiac failure. *Pulmonary embolism with infarction* - A **pulmonary embolism** often presents with acute dyspnea and hypoxemia, but the chest X-ray is typically **normal** or shows focal changes like a Westermark sign or Hampton hump, not diffuse bilateral infiltrates. - While a possibility post-surgery, the widespread radiological changes are more indicative of a global lung injury like ARDS, which can be triggered by events such as **fat embolism syndrome**. *Transfusion-related acute lung injury (TRALI)* - TRALI is characterized by **acute hypoxemia** and **bilateral pulmonary infiltrates** that occur within 6 hours of a **blood product transfusion**. - The question does not specify a recent **blood transfusion**, and the 18-hour post-operative timeframe makes TRALI less likely unless the transfusion occurred much earlier with delayed onset of symptoms.
Question 37: A 42-year-old office worker presents with a 10-week history of lower back pain radiating down the posterior aspect of his right leg to the lateral aspect of his foot. He has reduced sensation over the lateral aspect of his foot and weakness of plantarflexion. Straight leg raise is positive at 40 degrees on the right. Which nerve root is most likely affected?
- A. L3 nerve root
- B. L4 nerve root
- C. L5 nerve root
- D. S1 nerve root (Correct Answer)
- E. S2 nerve root
Explanation: ***S1 nerve root*** - S1 radiculopathy is characterized by **weakness in plantarflexion** (gastrocnemius/soleus) and loss of sensation over the **lateral aspect of the foot** and small toe. - It frequently results from an **L5/S1 disc herniation** and is associated with a **diminished ankle reflex**. *L3 nerve root* - Compression here typically results in sensory loss over the **anterior thigh** and weakness in **hip flexion** or knee extension. - It would not cause symptoms radiating to the lateral foot or affects on **plantarflexion**. *L4 nerve root* - L4 involvement presents with weakness in **knee extension** and a diminished **knee-jerk (patellar) reflex**. - Sensory loss is usually located on the **medial aspect of the leg** and foot, rather than the lateral side. *L5 nerve root* - L5 radiculopathy causes weakness in **big toe extension** (extensor hallucis longus) and **foot dorsiflexion**, leading to foot drop. - Sensory deficit is primarily found on the **dorsum of the foot** and the first web space between the first and second toes. *S2 nerve root* - Isolated S2 compression is rare and typically presents with sensory loss over the **posterior thigh** and popliteal fossa. - It is more commonly associated with **cauda equina syndrome**, involving bladder or bowel dysfunction rather than isolated plantarflexion weakness.
Question 38: A 77-year-old woman is being consented for cemented hemiarthroplasty for a displaced intracapsular neck of femur fracture. She asks about the risks of the procedure. According to the National Hip Fracture Database and published literature, what is the approximate 30-day mortality rate following surgical treatment of hip fracture in the UK?
- A. 1-2%
- B. 5-8% (Correct Answer)
- C. 10-12%
- D. 15-18%
- E. 20-25%
Explanation: ***5-8%*** - According to data from the **National Hip Fracture Database (NHFD)**, the **30-day mortality** rate for hip fractures in the UK has settled within this range over recent years due to improved **orthogeriatric care**. - This statistic is essential for **informed consent** as it reflects the systemic frailty and perioperative risks associated with the elderly population. *1-2%* - This range is too low and is more representative of mortality for **elective** primary hip replacements in healthier cohorts. - **Hip fracture** patients are typically older with multiple **comorbidities**, resulting in significantly higher acute mortality. *10-12%* - Although historical rates were higher, modern **multidisciplinary management** has successfully reduced the average 30-day mortality below this level. - This percentage might be seen in specific **high-risk subgroups**, such as those with severe **cardiac failure** or high ASA grades, but not the national average. *15-18%* - Mortality this high is generally not observed within the first **30 days** post-surgery in contemporary UK practice. - These figures may align more with mortality rates at the **3-to-6-month** mark following a hip fracture. *20-25%* - This range is closer to the **one-year mortality** rate, which remains high at approximately **30%** for this patient demographic. - It overstates the immediate **perioperative risk** encountered within the first month of surgical intervention.
Question 39: A 54-year-old man with a 20-year history of ankylosing spondylitis presents to the Emergency Department after a minor fall. He reports severe neck pain and is protecting his cervical spine. He has no neurological deficit. What is the most appropriate initial imaging investigation?
- A. MRI of the cervical spine
- B. Plain radiographs of the cervical spine (3 views)
- C. CT scan of the entire spine (Correct Answer)
- D. Flexion-extension views of the cervical spine
- E. Plain radiographs of the cervical spine followed by MRI if normal
Explanation: ***CT scan of the entire spine*** - In patients with **ankylosing spondylitis**, the fused and brittle **"bamboo spine"** is highly susceptible to **unstable fractures** even after minor trauma, requiring high-sensitivity imaging. - **CT scanning of the entire spine** is the preferred initial investigation because it can detect subtle fractures that may be **multiple or non-contiguous** across different spinal levels, which is crucial in AS. *Plain radiographs of the cervical spine (3 views)* - **Plain radiographs** have very low sensitivity in ankylosing spondylitis due to **overlapping ossified ligaments** and architectural distortion. - A "normal" radiograph cannot safely exclude a fracture in this patient population, often leading to **delayed diagnosis** and neurological catastrophe. *MRI of the cervical spine* - While **MRI** is superior for evaluating **spinal cord injury**, hematoma, or ligamentous tears, it is not the first-line modality for identifying acute bone cortex breaks. - MRI is typically reserved as a **secondary investigation** if the CT is negative but clinical suspicion or neurological deficits persist. *Flexion-extension views of the cervical spine* - These views are **strictly contraindicated** in the acute setting of suspected spinal fracture or instability. - Attempting forced motion in a brittle, potentially fractured spine can cause **displacement** and permanent **neurological damage**. *Plain radiographs of the cervical spine followed by MRI if normal* - Starting with radiographs is inappropriate as they are clinically unreliable for excluding fractures in a **rigid, osteoporotic spine**. - Relying on this sequence unnecessarily **delays definitive diagnosis** and may miss fractures at non-cervical levels that CT would have caught.
Question 40: A 68-year-old man underwent dynamic hip screw fixation for a stable two-part intertrochanteric fracture 4 months ago. He now presents with persistent groin pain on weight-bearing and difficulty mobilizing. Radiographs show the lag screw has migrated laterally through the femoral head with loss of fixation. What is the most likely mechanism responsible for this complication?
- A. Infection leading to loosening of the implant
- B. Excessive weight-bearing during the early post-operative period
- C. Inadequate reduction with varus malposition at the fracture site (Correct Answer)
- D. Osteoporosis causing continued collapse around the screw
- E. Screw placed in the inferior portion of the femoral head
Explanation: ***Inadequate reduction with varus malposition at the fracture site***- **Varus malposition** places the lag screw in a more superior position relative to the femoral head, increasing the shear forces and the risk of **mechanical cut-out**.- Stable reduction is critical for the success of a **Dynamic Hip Screw (DHS)**, as it ensures that weight-bearing forces are transmitted through the bone rather than just the implant.*Infection leading to loosening of the implant*- **Implant loosening** due to infection usually presents with systemic symptoms, localized swelling, or **lucent lines** around the hardware on radiographs.- While infection causes bone resorption, it does not typically manifest as a specific lateral migration of the **lag screw** through the cortex without other signs of sepsis.*Excessive weight-bearing during the early post-operative period*- The **Dynamic Hip Screw (DHS)** is specifically designed to allow for **controlled compression** and collapse at the fracture site during weight-bearing.- While non-compliance can stress any hardware, it is rarely the primary cause of cut-out if the **Tip-Apex Distance (TAD)** and reduction are anatomically correct.*Osteoporosis causing continued collapse around the screw*- **Poor bone quality** (osteoporosis) certainly provides less resistance to screw migration, but it is considered a secondary risk factor compared to **surgical technique**.- Most fixation failures in osteoporotic bone are ultimately attributed to suboptimal hardware placement or poor **fracture reduction** rather than the bone quality alone.*Screw placed in the inferior portion of the femoral head*- Placement of the lag screw in the **inferior or central** portion of the femoral head is actually the recommended technique to minimize cut-out risk.- Contrastingly, **superior-posterior** placement is a known technical error that significantly increases the likelihood of the screw migrating through the femoral head.
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