Orthopaedics & MSK — MCQs
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A 36-year-old woman presents with a 12-week history of lower back pain, bilateral buttock pain, and morning stiffness lasting 90 minutes that improves with activity. She has a history of inflammatory bowel disease. Plain radiographs of the pelvis and lumbar spine are normal. What is the most appropriate next step in investigation?
A 71-year-old woman undergoes dynamic hip screw fixation for a stable intertrochanteric neck of femur fracture. What is the optimal position of the lag screw within the femoral head to reduce the risk of fixation failure?
A 49-year-old woman with a 6-month history of chronic lower back pain presents with new onset faecal incontinence and inability to feel when her bladder is full. She reports numbness in the perineal area but denies leg weakness. Lower limb examination shows normal power, normal reflexes, and intact sensation except for saddle anaesthesia. What is the most appropriate immediate management?
Which of the following arteries is most at risk during insertion of cannulated screws for fixation of an intracapsular neck of femur fracture?
A 57-year-old man presents with a 3-month history of progressively worsening lower back pain and bilateral leg weakness. He has a 35 pack-year smoking history. Examination reveals symmetrical lower limb weakness (4/5 power), hyper-reflexia, and extensor plantar responses bilaterally. Perianal sensation is intact. What is the most likely diagnosis?
A 79-year-old man with a displaced intracapsular neck of femur fracture is being considered for surgery. He has severe dementia (AMTS 2/10), is nursing home resident requiring full assistance with all activities of daily living, and was non-ambulatory pre-injury. What is the most appropriate surgical management?
A 42-year-old woman presents with a 4-week history of lower back pain and morning stiffness lasting 2 hours. She reports improvement with exercise. She has a history of psoriasis and recurrent anterior uveitis. Inflammatory markers are elevated: CRP 34 mg/L, ESR 42 mm/hr. What is the most appropriate initial imaging investigation?
Which nerve root is most commonly affected in lumbar disc herniation causing sciatica with loss of ankle reflex?
A 73-year-old woman sustains a reverse oblique intertrochanteric femur fracture following a fall. She is medically optimized and undergoes surgical fixation. Which fixation method is most appropriate for this fracture pattern?
What is the primary mechanism by which weight-bearing status is restricted following internal fixation of an undisplaced intracapsular neck of femur fracture with cannulated screws?
Orthopaedics & MSK UK Medical PG Practice Questions and MCQs
Question 171: A 36-year-old woman presents with a 12-week history of lower back pain, bilateral buttock pain, and morning stiffness lasting 90 minutes that improves with activity. She has a history of inflammatory bowel disease. Plain radiographs of the pelvis and lumbar spine are normal. What is the most appropriate next step in investigation?
- A. HLA-B27 testing
- B. MRI of sacroiliac joints (Correct Answer)
- C. CT of pelvis
- D. Bone density scan (DEXA)
- E. Rheumatoid factor and anti-CCP antibodies
Explanation: ***MRI of sacroiliac joints*** - In patients with symptoms highly suggestive of **inflammatory back pain** and normal plain radiographs, **MRI of the sacroiliac (SI) joints** is the most sensitive test to detect early **sacroiliitis** by showing **bone marrow edema**. - This is the gold standard for diagnosing **non-radiographic axial spondyloarthritis (nr-axSpA)**, especially given the patient's history of **inflammatory bowel disease**, which is strongly associated with spondyloarthritis. *HLA-B27 testing* - While a **positive HLA-B27** allele is associated with spondyloarthropathies, it is not diagnostic on its own as it is also present in a significant portion of the **healthy population**. - A positive result can support the diagnosis but does not provide visual confirmation of **active inflammation** in the joints, which is needed for diagnosis and management. *CT of pelvis* - **CT scanning** provides excellent detail of **structural bone changes** like erosions and sclerosis, but it is less sensitive than MRI for detecting early **active inflammation** or **bone marrow edema**. - It also involves significant **ionizing radiation** exposure, making MRI a preferred and safer choice for evaluating early inflammatory changes. *Bone density scan (DEXA)* - A **DEXA scan** is used to diagnose **osteoporosis** or osteopenia by measuring bone mineral density. - It has no role in the initial diagnostic workup of **inflammatory back pain** or sacroiliitis, though patients with chronic inflammation may develop osteoporosis later. *Rheumatoid factor and anti-CCP antibodies* - These markers are specific for **rheumatoid arthritis (RA)**, which primarily involves **peripheral small joints** in a symmetrical pattern and spares the sacroiliac joints. - Axial involvement is not a feature of typical rheumatoid arthritis (except for the **C1-C2 vertebrae** in advanced disease), making these tests inappropriate for this presentation.
Question 172: A 71-year-old woman undergoes dynamic hip screw fixation for a stable intertrochanteric neck of femur fracture. What is the optimal position of the lag screw within the femoral head to reduce the risk of fixation failure?
- A. Superior and anterior position
- B. Inferior and posterior position
- C. Central-central position with tip-apex distance <25 mm (Correct Answer)
- D. Superior and posterior position
- E. Inferior and anterior position
Explanation: ***Central-central position with tip-apex distance <25 mm***- The **central-central position** on both AP and lateral views ensures the lag screw is anchored in the densest **subchondral bone**, providing the greatest mechanical stability.- Maintaining a **Tip-Apex Distance (TAD)** of less than **25 mm** is the most critical surgical factor for preventing **screw cut-out**, the most common cause of fixation failure.*Superior and anterior position*- Placing the screw in a **superior position** significantly increases the risk of the screw cutting through the **superior cortex** of the femoral head under weight-bearing loads.- An **anterior position** provides thinner bone stock for the screw threads, leading to poor **purchase** and increased mechanical instability.*Inferior and posterior position*- While some surgeons traditionally favored an **inferior position** on the AP view to engage the calcar, a **posterior position** on the lateral view is associated with higher failure rates.- Deviation from the **center-center** axis in both planes increases the resultant forces that drive **fixation failure**.*Superior and posterior position*- This is considered the least desirable position as the **superior-posterior** quadrant has the lowest bone mineral density in the femoral head.- This location greatly increases the **eccentric loading** on the lag screw, predisposing the patient to early **implant cut-out**.*Inferior and anterior position*- An **anterior position** on the lateral radiograph is suboptimal because it fails to align with the **mechanical axis** of the femoral neck.- Even if the screw is **inferior** on the AP view, any eccentricity on the lateral view contributes to a higher **TAD**, surpassing the recommended **25 mm** safety threshold.
Question 173: A 49-year-old woman with a 6-month history of chronic lower back pain presents with new onset faecal incontinence and inability to feel when her bladder is full. She reports numbness in the perineal area but denies leg weakness. Lower limb examination shows normal power, normal reflexes, and intact sensation except for saddle anaesthesia. What is the most appropriate immediate management?
- A. Urgent outpatient MRI within 1 week and neurology referral
- B. Emergency MRI spine and surgical decompression (Correct Answer)
- C. Commence gabapentin and arrange physiotherapy
- D. Admit for catheterization, analgesia, and MRI within 24 hours
- E. Reassure and arrange routine MRI in 4-6 weeks
Explanation: ***Emergency MRI spine and surgical decompression***- This patient presents with hallmark features of **Cauda Equina Syndrome (CES)**, including **saddle anaesthesia**, **faecal incontinence**, and loss of bladder sensation, which is a surgical emergency.- Immediate **MRI** is required to confirm the compression, followed by **urgent surgical decompression** (usually within 24-48 hours) to prevent permanent loss of bowel, bladder, and sexual function.*Urgent outpatient MRI within 1 week and neurology referral*- Any delay in imaging when CES is suspected can lead to **irreversible neurological deficits**; outpatient management is completely inappropriate for this presentation.- The management of CES is typically handled by **neurosurgery** or **orthopaedic spinal surgery**, not neurology, due to the need for mechanical decompression.*Commence gabapentin and arrange physiotherapy*- **Gabapentin** is used for chronic neuropathic pain, but it does nothing to address the **mechanical compression** of nerve roots in CES.- **Physiotherapy** is contraindicated as the primary management for an acute spinal emergency and would delay life-changing surgical intervention.*Admit for catheterization, analgesia, and MRI within 24 hours*- While the patient requires admission and catheterization, an **MRI within 24 hours** may be too slow if the goal is to optimize recovery by decompressing as soon as possible.- In the context of **sphincter disturbance** (faecal incontinence), the timeline should be emergency/immediate rather than a "within 24 hours" target which might allow for unnecessary delays.*Reassure and arrange routine MRI in 4-6 weeks*- Reassurance is dangerous in this clinical scenario as **saddle anaesthesia** and bowel/bladder dysfunction are "red flag" symptoms for spinal cord or nerve root compression.- A **routine MRI timeline** (4-6 weeks) would almost certainly guarantee the patient suffers **permanent paralysis** or permanent double incontinence.
Question 174: Which of the following arteries is most at risk during insertion of cannulated screws for fixation of an intracapsular neck of femur fracture?
- A. Obturator artery
- B. Medial circumflex femoral artery (Correct Answer)
- C. Lateral circumflex femoral artery
- D. Profunda femoris artery
- E. Superior gluteal artery
Explanation: ***Medial circumflex femoral artery*** - The **medial circumflex femoral artery (MCFA)** is the most critical blood supply to the **femoral head**, particularly its posterior superior retinacular branches. Injury to these vessels is the primary cause of **avascular necrosis (AVN)** of the femoral head following intracapsular fractures. - During surgical fixation with cannulated screws, these retinacular branches, which run along the femoral neck within the capsule, are highly susceptible to direct trauma or disruption, further compromising an already precarious blood supply. *Obturator artery* - The **obturator artery** contributes a small amount to the femoral head's blood supply through the artery of the **ligamentum teres**, which is contained within the fovea capitis. - This contribution is generally considered minor and often non-functional or obliterated in adults, making it less significant for overall head viability and less at risk during screw placement in the neck. *Lateral circumflex femoral artery* - The **lateral circumflex femoral artery** primarily supplies the anterior and lateral aspects of the thigh, including the **quadriceps femoris muscles** and the anterior hip joint capsule. - While it contributes to the vascular ring around the femoral neck, its direct retinacular branches supplying the femoral head are far less significant than those of the medial circumflex femoral artery. *Profunda femoris artery* - The **profunda femoris artery**, or deep femoral artery, is a large branch of the femoral artery and gives rise to both the medial and lateral circumflex femoral arteries. - Although it is the main arterial supply to the **deep thigh musculature**, it is anatomically distant from the femoral neck itself and therefore not directly at risk during the insertion of cannulated screws. *Superior gluteal artery* - The **superior gluteal artery** is a branch of the internal iliac artery that exits the pelvis superior to the piriformis muscle, supplying the **gluteus medius**, minimus, and tensor fascia latae muscles. - This artery is located far from the femoral neck and provides no direct blood supply to the femoral head, making it safe from injury during **intracapsular cannulated screw fixation**.
Question 175: A 57-year-old man presents with a 3-month history of progressively worsening lower back pain and bilateral leg weakness. He has a 35 pack-year smoking history. Examination reveals symmetrical lower limb weakness (4/5 power), hyper-reflexia, and extensor plantar responses bilaterally. Perianal sensation is intact. What is the most likely diagnosis?
- A. Cauda equina syndrome
- B. Lumbar spinal stenosis
- C. Thoracic cord compression (Correct Answer)
- D. Peripheral neuropathy
- E. Guillain-Barré syndrome
Explanation: ***Thoracic cord compression***- The presence of **upper motor neuron (UMN) signs**, such as **hyper-reflexia** and **extensor plantar responses** (Babinski sign) in the lower limbs, localizes the lesion above the level of the L1 vertebra, most commonly the thoracic spine.- The patient's 35 pack-year **smoking history** and progressive back pain raise high suspicion for **metastatic malignancy** causing spinal cord compression.*Cauda equina syndrome*- This condition involves compression of nerve roots below the spinal cord terminus, presenting with **lower motor neuron (LMN) signs**, such as **hyporeflexia** and flaccid paralysis.- It is classically associated with **saddle anesthesia** and bladder/bowel dysfunction, whereas this patient has **intact perianal sensation** and UMN signs.*Lumbar spinal stenosis*- Typically presents as **neurogenic claudication**, where leg pain and weakness are triggered by walking and relieved by leaning forward.- Physical examination generally shows **decreased or absent reflexes** (LMN signs) rather than the hyper-reflexia and extensor plantars seen here.*Peripheral neuropathy*- Characterized by a **'glove and stocking'** distribution of sensory loss and distal weakness, which does not match this patient's presentation.- Features **absent or reduced deep tendon reflexes** and is not associated with **pathological plantar responses** or back pain.*Guillain-Barré syndrome*- An acute, **ascending inflammatory polyradiculoneuropathy** that typically follows a gastrointestinal or respiratory infection.- It presents with **areflexia** and symmetric flaccid paralysis, which is inconsistent with the **spasticity and hyper-reflexia** noted in this case.
Question 176: A 79-year-old man with a displaced intracapsular neck of femur fracture is being considered for surgery. He has severe dementia (AMTS 2/10), is nursing home resident requiring full assistance with all activities of daily living, and was non-ambulatory pre-injury. What is the most appropriate surgical management?
- A. Total hip replacement
- B. Cemented hemiarthroplasty
- C. Uncemented hemiarthroplasty
- D. Internal fixation with cannulated screws
- E. Conservative management with analgesia (Correct Answer)
Explanation: ***Conservative management with analgesia***- In a patient who was **non-ambulatory** pre-injury and has **severe dementia**, the surgical risks of anesthesia and post-operative complications typically outweigh the benefits of mobility restoration.- Focus shifts to **palliative care**, optimizing comfort through **pain relief**, pressure sore prevention, and maintaining quality of life rather than functional rehabilitation.*Total hip replacement*- This procedure is indicated for patients who are **active**, fit for surgery, and have no **cognitive impairment**, which is the opposite of this patient's profile.- It carries a higher risk of **dislocation** and surgical complexity that is unjustified in a non-ambulatory resident.*Cemented hemiarthroplasty*- This is the standard of care for most elderly patients with **displaced intracapsular fractures** who were previously mobile.- While it allows early weight-bearing, it is inappropriate for a patient who cannot **mobilize** due to severe pre-existing cognitive and functional deficits.*Uncemented hemiarthroplasty*- Current **NICE guidelines** generally recommend cemented over uncemented implants due to better functional outcomes and lower risk of **periprosthetic fractures**.- It offers no advantage in this specific case where the primary goal is not restoring gait in a non-ambulatory patient.*Internal fixation with cannulated screws*- This technique is generally reserved for **undisplaced fractures** or young patients where preserving the **femoral head** is a priority.- It has a high **failure rate** in displaced fractures in the elderly and would subject this frail patient to an unnecessary surgical intervention.
Question 177: A 42-year-old woman presents with a 4-week history of lower back pain and morning stiffness lasting 2 hours. She reports improvement with exercise. She has a history of psoriasis and recurrent anterior uveitis. Inflammatory markers are elevated: CRP 34 mg/L, ESR 42 mm/hr. What is the most appropriate initial imaging investigation?
- A. Plain radiographs of lumbar spine and sacroiliac joints
- B. MRI of the lumbar spine
- C. MRI of sacroiliac joints (Correct Answer)
- D. CT of the lumbar spine
- E. Bone scan
Explanation: ***MRI of sacroiliac joints*** - Given the patient's **inflammatory back pain** (morning stiffness, improvement with exercise), history of **psoriasis**, and **uveitis**, **axial spondyloarthropathy** is highly suspected. - **MRI of the sacroiliac joints** is the most sensitive imaging modality for detecting **early active sacroiliitis** (bone marrow edema), which is crucial for diagnosis in the initial stages when X-rays may still be normal. *Plain radiographs of lumbar spine and sacroiliac joints* - **Plain radiographs** primarily detect **chronic structural damage** such as erosions, sclerosis, or ankylosis, which may take years to develop and might not be present in early disease. - In the context of **early inflammatory back pain** and suspicion of axial spondyloarthropathy, X-rays have **low sensitivity** for active inflammation and can lead to delayed diagnosis. *MRI of the lumbar spine* - While an **MRI of the lumbar spine** can identify spinal pathology, it may not adequately visualize the **sacroiliac joints**, which are typically the primary site of inflammation in axial spondyloarthropathy. - It focuses more on **vertebral bodies**, **intervertebral discs**, and **spinal cord structures**, which are less likely to show the earliest inflammatory changes specific to this condition. *CT of the lumbar spine* - **CT scans** excel at visualizing **bony architecture** and detecting structural changes like erosions or fusion but are **less sensitive than MRI** for detecting early active inflammation (bone marrow edema). - It also involves significant **ionizing radiation**, making it a less suitable initial diagnostic choice compared to MRI for suspected inflammatory conditions. *Bone scan* - A **bone scan** (scintigraphy) is highly sensitive for detecting increased metabolic activity but has **low specificity**, meaning it cannot differentiate well between inflammatory, degenerative, or traumatic causes of bone uptake. - It is generally **not recommended** as a primary diagnostic tool for early axial spondyloarthropathy due to its lack of detail and inability to precisely localize or characterize the type of inflammation.
Question 178: Which nerve root is most commonly affected in lumbar disc herniation causing sciatica with loss of ankle reflex?
- A. L3
- B. L4
- C. L5
- D. S1 (Correct Answer)
- E. S2
Explanation: ***S1*** - The **ankle reflex** (Achilles tendon reflex) is primarily mediated by the **S1 nerve root**; therefore, its loss is a hallmark of S1 radiculopathy. - S1 nerve root compression, often due to an **L5-S1 disc herniation**, typically results in sensory loss at the **lateral foot** and weakness in **plantar flexion**. *L3* - Injury to the L3 nerve root affects the **patellar (knee) reflex**, not the ankle reflex. - L3 radiculopathy usually presents with pain and sensory loss over the **anterior thigh** and weakness in **hip adduction**. *L4* - The L4 nerve root is the main mediator of the **patellar reflex**, and its compression leads to a diminished knee-jerk response. - It is associated with **weakness in knee extension** (quadriceps) and sensory loss over the **medial malleolus**. *L5* - L5 radiculopathy characteristically causes **weakness in big toe extension** (Extensor Hallucis Longus) and **foot drop** during dorsiflexion. - Crucially, the **ankle reflex remains intact** in L5 lesions because the reflex arc is specifically dependent on the S1 root. *S2* - S2 nerve root involvement is rare in isolated lumbar disc herniations and primarily contributes to **bladder and bowel function** or sensation in the **perineal area**. - While it contributes slightly to the Achilles reflex, its isolation would not be the primary cause of a completely lost ankle reflex, which is distinct from the primary S1 involvement.
Question 179: A 73-year-old woman sustains a reverse oblique intertrochanteric femur fracture following a fall. She is medically optimized and undergoes surgical fixation. Which fixation method is most appropriate for this fracture pattern?
- A. Dynamic hip screw with plate
- B. Cannulated screws
- C. Cephalomedullary nail (Correct Answer)
- D. Total hip replacement
- E. Hemiarthroplasty
Explanation: ***Cephalomedullary nail*** - For **reverse oblique intertrochanteric fractures**, cephalomedullary nails provide superior **biomechanical stability** by acting as a buttress to prevent **medial displacement** of the femoral shaft. - This intramedullary device is less likely to fail under the high mechanical stress associated with this specific **unstable fracture pattern** compared to extramedullary implants. *Dynamic hip screw with plate* - A **DHS** is biomechanically unsuitable here because the fracture line runs from **superomedial to inferolateral**, which allows the femoral shaft to slide medially along the screw. - Use of a side plate in reverse oblique patterns often leads to **fixation failure** and nonunion due to the lack of an intact lateral wall to provide support. *Cannulated screws* - These are primarily indicated for **nondisplaced intracapsular femoral neck fractures**, not extracapsular intertrochanteric fractures. - They lack the necessary **load-bearing strength** to stabilize complex, high-energy, or unstable intertrochanteric fracture lines. *Total hip replacement* - **Total hip arthroplasty** is generally reserved for **intracapsular fractures**, severe hip osteoarthritis, or salvage after failed internal fixation. - It is overly invasive for an isolated intertrochanteric fracture where the **femoral head and acetabulum** are otherwise healthy. *Hemiarthroplasty* - This procedure is typically used for **displaced femoral neck fractures** in elderly patients to allow early mobilization, not as a primary treatment for reverse oblique patterns. - Fixation with a nail is preferred over hemiarthroplasty to **preserve the native joint** and avoid the higher risks of dislocation associated with arthroplasty in extracapsular fractures.
Question 180: What is the primary mechanism by which weight-bearing status is restricted following internal fixation of an undisplaced intracapsular neck of femur fracture with cannulated screws?
- A. To prevent avascular necrosis of the femoral head
- B. To allow bone healing and prevent fracture displacement (Correct Answer)
- C. To reduce the risk of deep vein thrombosis
- D. To minimize pain during the early post-operative period
- E. To prevent failure of the fixation implant
Explanation: ***To allow bone healing and prevent fracture displacement*** - Restricting weight-bearing is crucial to maintain the **anatomical alignment** of an undisplaced fracture while the **primary bone healing** occurs. - Premature excessive loading can lead to **secondary displacement** of the intracapsular fracture, which significantly increases the risk of fixation failure and the need for **arthroplasty**. *To prevent avascular necrosis of the femoral head* - **Avascular necrosis (AVN)** is primarily caused by the initial **vascular insult** to the retinacular vessels during the injury itself. - While weight-bearing is restricted post-surgery, it does not directly prevent the biological process of **ischemic necrosis** resulting from interrupted blood supply. *To reduce the risk of deep vein thrombosis* - Weight-bearing restriction actually **increases** the risk of venous stasis and **deep vein thrombosis (DVT)** rather than reducing it. - DVT prevention is achieved through **pharmacological prophylaxis** and encouraging early **ankle pump exercises** and mobilization within safe limits. *To minimize pain during the early post-operative period* - While limiting movement may indirectly help with comfort, **pain management** is primarily addressed with **analgesics** and regional nerve blocks. - Clinical protocols for weight-bearing are based on **fracture stability** and biomechanics rather than purely on the patient's pain threshold. *To prevent failure of the fixation implant* - Although implant protection is important, **titanium or steel cannulated screws** are designed to withstand significant stress; the weaker link is the **bone-screw interface**. - The primary focus is preventing the **bone fragments** from shifting (displacement) rather than worrying about the structural breakage of the **metal hardware** itself.
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