What percentage of the blood supply to the femoral head is provided by the medial femoral circumflex artery in adults?
Q82
A 73-year-old man undergoes a cemented hemiarthroplasty for a displaced intracapsular neck of femur fracture. During cement insertion, he suddenly becomes hypotensive (BP 75/40 mmHg) and desaturates (SpO2 82%). His heart rate increases to 120 bpm. What is the most likely diagnosis?
Q83
An 86-year-old woman sustains a Garden II intracapsular neck of femur fracture following a fall. She has severe dementia (AMTS 2/10), is normally bed-bound, and lives in a nursing home with full care. She has multiple comorbidities including severe COPD and ischaemic heart disease. What is the most appropriate initial management?
Q84
A 42-year-old man presents to his GP with a 6-week history of lower back pain. The pain is worse in the morning and improves with exercise. He also reports bilateral heel pain. On examination, there is reduced lumbar spine flexion with a Schober test measurement of 3 cm. What is the most appropriate initial investigation?
Q85
A 70-year-old woman presents to the Emergency Department following a fall. She has a shortened and externally rotated left leg. Radiographs confirm a displaced subcapital neck of femur fracture. She has an eGFR of 35 mL/min/1.73m². What surgical intervention is most appropriate for this patient?
Q86
A 47-year-old woman presents with a 4-month history of lower back pain and progressive bilateral leg weakness. She has a history of breast cancer treated 18 months ago with mastectomy and adjuvant chemotherapy. MRI demonstrates a soft tissue mass causing spinal canal compromise at T12. Neurological examination reveals grade 4/5 power in both legs, intact sensation, and preserved sphincter function. After commencing dexamethasone, a multidisciplinary team meeting discusses management options. Which factor would most strongly favour surgical decompression over radiotherapy alone as the initial definitive treatment?
Q87
A 67-year-old man undergoes a dynamic hip screw fixation for a stable intertrochanteric femur fracture. The operation is technically successful with good reduction and appropriate implant positioning on intraoperative fluoroscopy. Six months later, he presents with increasing hip pain and difficulty walking. Radiographs show the lag screw has cut out superiorly through the femoral head. Which intraoperative measurement error most likely contributed to this complication?
Q88
A 38-year-old woman presents with a 6-week history of lower back pain and stiffness. She also reports a 2-week history of painful red eyes and worsening vision. She has a past medical history of psoriasis. Blood tests show: CRP 54 mg/L, ESR 42 mm/hr. Which extra-articular manifestation is she currently experiencing?
Q89
A 65-year-old man sustains a subcapital neck of femur fracture with posterior comminution after a fall. He is an active independent individual who plays golf twice weekly. He has well-controlled type 2 diabetes and hypertension. Preoperatively, his surgeon discusses the risk of avascular necrosis of the femoral head if internal fixation is performed. In the context of this specific fracture pattern, which feature contributes most significantly to the elevated risk of avascular necrosis?
Q90
A 72-year-old man presents with a 3-month history of lower back pain that has recently started radiating down his right leg to his foot. He describes weakness when trying to push down on the accelerator while driving. On examination, he has weakness of right ankle plantarflexion (4/5 power), reduced sensation over the right lateral foot and sole, and an absent right ankle reflex. Straight leg raise is positive at 40 degrees on the right. Which nerve root is most likely compressed?
Orthopaedics & MSK UK Medical PG Practice Questions and MCQs
Question 81: What percentage of the blood supply to the femoral head is provided by the medial femoral circumflex artery in adults?
A. 20-30%
B. 40-50%
C. 60-70%
D. 80-90% (Correct Answer)
E. 95-100%
Explanation: ***80-90%***
- The **medial femoral circumflex artery (MFCA)** is the dominant blood supply to the adult femoral head, contributing approximately **80-90%** of its circulation.
- It gives rise to the **superior and inferior retinacular arteries**, which are frequently disrupted in **intracapsular femoral neck fractures**, leading to **avascular necrosis**.
*20-30%*
- This range significantly underestimates the arterial dominance of the MFCA; a contribution this low would describe the **lateral femoral circumflex artery** or minor collateral flow.
- Clinical risk of **osteonecrosis** after fracture is high precisely because the MFCA provides far more than 30% of the total supply.
*40-50%*
- While nearly half, this value does not reflect the **anatomical reality** where the MFCA serves as the primary and near-exclusive source for the femoral head epiphysis.
- This percentage would suggest a more balanced supply with the **obturator artery**, which is not the case in the adult skeleton.
*60-70%*
- Although the MFCA is the main source, its actual contribution is more substantial than two-thirds, reaching the **80-90%** threshold in most individuals.
- This value fails to highlight the extreme vulnerability of the femoral head to **ischemia** when the circumflex vessels are compromised.
*95-100%*
- While the MFCA is the primary vessel, this range excludes the consistent, albeit minor, contributions from the **artery of the ligamentum teres** (obturator artery) and the **lateral circumflex artery**.
- The **artery of ligamentum teres** typically provides about **5-10%** of the supply in adults, preventing the MFCA from accounting for the entire 100%.
Question 82: A 73-year-old man undergoes a cemented hemiarthroplasty for a displaced intracapsular neck of femur fracture. During cement insertion, he suddenly becomes hypotensive (BP 75/40 mmHg) and desaturates (SpO2 82%). His heart rate increases to 120 bpm. What is the most likely diagnosis?
A. Pulmonary embolism from deep vein thrombosis
B. Anaphylactic reaction to antibiotic prophylaxis
C. Fat embolism syndrome
D. Bone cement implantation syndrome (Correct Answer)
E. Myocardial infarction
Explanation: ***Bone cement implantation syndrome***
- This clinical picture is pathognomonic due to the timing of **sudden hypotension** and **hypoxia** occurring specifically during the **cementation phase** of hip surgery.
- It is caused by the embolization of **bone marrow**, fat, and air into the pulmonary circulation, leading to a sudden increase in **pulmonary vascular resistance**.
*Pulmonary embolism from deep vein thrombosis*
- While a major cause of post-operative distress, it typically presents later in the **recovery period** rather than intraoperatively at the moment of cementing.
- The immediate temporal relationship with **cement insertion** makes a primary DVT-related embolus less likely than BCIS.
*Anaphylactic reaction to antibiotic prophylaxis*
- Anaphylaxis usually presents shortly after **drug administration** and is often accompanied by **bronchospasm**, wheezing, or cutaneous signs like **urticaria**.
- In this case, the hemodynamic collapse is directly synchronized with the surgical step of **bone cement** application.
*Fat embolism syndrome*
- Characterized by a classic triad of **hypoxemia**, **neurological abnormalities**, and a **petechial rash**, which aren't fully described here.
- It typically follows a **latent period** of 24–72 hours after the initial trauma or surgery, unlike the acute intraoperative presentation of BCIS.
*Myocardial infarction*
- While an intraoperative **MI** can cause sudden hypotension and tachycardia, it lacks the specific association with the **reaming or cementing** process.
- BCIS is a more common cause of acute **right-sided heart strain** and collapse during this specific part of a hemiarthroplasty.
Question 83: An 86-year-old woman sustains a Garden II intracapsular neck of femur fracture following a fall. She has severe dementia (AMTS 2/10), is normally bed-bound, and lives in a nursing home with full care. She has multiple comorbidities including severe COPD and ischaemic heart disease. What is the most appropriate initial management?
A. Cannulated screw fixation
B. Cemented hemiarthroplasty
C. Total hip replacement
D. Conservative management with analgesia and early mobilisation (Correct Answer)
E. Uncemented hemiarthroplasty
Explanation: ***Conservative management with analgesia and early mobilisation***
- This patient is **86 years old**, **bed-bound** with **severe dementia (AMTS 2/10)**, and has significant **comorbidities** (severe COPD, ischaemic heart disease).
- For such a frail patient with very limited pre-injury mobility and severe cognitive impairment, the risks of surgery often outweigh any potential functional benefit, making **palliation** and comfort care paramount.
*Cannulated screw fixation*
- **Cannulated screw fixation** is typically used for stable, **undisplaced or minimally displaced intracapsular fractures** in younger, more active patients to preserve the femoral head.
- In an 86-year-old bed-bound patient with severe comorbidities, the risks of fixation failure, avascular necrosis, and the need for revision surgery are high, and it would not significantly improve her baseline functional status.
*Cemented hemiarthroplasty*
- **Cemented hemiarthroplasty** is the preferred surgical option for **displaced intracapsular neck of femur fractures** in **elderly, independently mobile** patients or those who ambulate with aids.
- Given her **severe dementia** and **bed-bound status**, this procedure would not restore her mobility, and she would still be at significant risk of complications (e.g., **bone cement implantation syndrome**) from a major surgery.
*Total hip replacement*
- **Total hip replacement (THR)** is generally reserved for **fit, active, and cognitively intact** elderly patients with displaced intracapsular fractures, or those with pre-existing hip pathology like arthritis.
- This patient's **severe dementia**, non-ambulatory status, and multiple comorbidities make her unsuitable for a complex and extensive procedure like THR, which requires significant postoperative rehabilitation.
*Uncemented hemiarthroplasty*
- **Uncemented hemiarthroplasty** is generally avoided in the elderly population due to higher rates of **periprosthetic fracture** and less reliable fixation in osteoporotic bone compared to cemented options.
- It offers no functional advantage for a bed-bound patient with severe comorbidities and cognitive impairment while carrying significant surgical risks.
Question 84: A 42-year-old man presents to his GP with a 6-week history of lower back pain. The pain is worse in the morning and improves with exercise. He also reports bilateral heel pain. On examination, there is reduced lumbar spine flexion with a Schober test measurement of 3 cm. What is the most appropriate initial investigation?
A. MRI lumbar spine
B. HLA-B27 genetic testing
C. Plain radiographs of the sacroiliac joints
D. Inflammatory markers (ESR and CRP) (Correct Answer)
E. Bone scan
Explanation: ***Inflammatory markers (ESR and CRP)***- In a patient presenting with suspected **ankylosing spondylitis** (AS) due to inflammatory back pain and heel pain, the initial step in primary care is to measure **ESR and CRP** to confirm the presence of **systemic inflammation**.- Elevated **CRP/ESR** levels support the clinical diagnosis of **inflammatory back pain** and help differentiate it from mechanical causes before progressing to more advanced imaging.
*MRI lumbar spine*- While **MRI** is the most sensitive imaging modality for detecting early **sacroiliitis** (bone marrow edema), it is typically a second-line investigation if initial clinical and biochemical tests are inconclusive.- It is not the most appropriate immediate first step in the GP setting when **inflammatory bloods** have not yet been performed to establish the inflammatory nature of the pain.
*HLA-B27 genetic testing*- **HLA-B27** is present in about 90% of patients with AS, but it is also found in a significant proportion of the **general population** who do not have the disease.- It is not used as a primary screening tool or **initial investigation** because a positive result does not confirm the diagnosis in isolation, and a negative result does not rule out spondyloarthritis.
*Plain radiographs of the sacroiliac joints*- **X-rays** of the sacroiliac joints can show chronic changes such as **erosions, sclerosis**, or **fusion**, but these changes often take years to develop and may be absent in early disease.- Therefore, plain radiographs have low sensitivity for **early diagnosis** and are less useful than inflammatory markers in the initial workup for suspected inflammatory back pain.
*Bone scan*- A **bone scan** is not routinely used for the diagnosis of **ankylosing spondylitis** as it lacks the specificity required to distinguish AS from other inflammatory processes.- Its primary role is in looking for **metastatic disease**, occult fractures, or other focal bone lesions, not the primary evaluation of **axial spondyloarthritis**.
Question 85: A 70-year-old woman presents to the Emergency Department following a fall. She has a shortened and externally rotated left leg. Radiographs confirm a displaced subcapital neck of femur fracture. She has an eGFR of 35 mL/min/1.73m². What surgical intervention is most appropriate for this patient?
A. Uncemented hemiarthroplasty (Correct Answer)
B. Cemented hemiarthroplasty
C. Cemented total hip replacement
D. Cannulated screw fixation
E. Dynamic hip screw fixation
Explanation: ***Uncemented hemiarthroplasty***
- For a **displaced subcapital neck of femur fracture** in an elderly patient, **arthroplasty** is preferred due to the high risk of **avascular necrosis** and non-union with internal fixation.
- An **uncemented** approach is indicated to avoid **Bone Cement Implantation Syndrome (BCIS)**, as patients with **renal impairment (eGFR 35)** are at increased risk of cardiovascular instability from cement exposure.
*Cemented hemiarthroplasty*
- While often a standard choice for elderly hip fractures, the use of cement poses a significant risk of **Bone Cement Implantation Syndrome (BCIS)**.
- This risk is heightened in patients with significant comorbidities like **renal impairment**, which can lead to life-threatening cardiovascular compromise.
*Cemented total hip replacement*
- **Total hip replacement (THR)** is generally reserved for more active elderly patients or those with **pre-existing osteoarthritis** of the hip.
- The use of cement in THR also carries the risk of **BCIS**, which is particularly concerning for this patient with **renal impairment**, making it a less safe option.
*Cannulated screw fixation*
- **Cannulated screws** are typically reserved for **undisplaced** or minimally displaced **intracapsular fractures** where the femoral head blood supply is likely preserved.
- For a **displaced subcapital fracture** in an elderly patient, fixation has a high rate of **non-union** and subsequent **avascular necrosis**, leading to poor functional outcomes.
*Dynamic hip screw fixation*
- A **dynamic hip screw (DHS)** is the treatment of choice for **extracapsular (intertrochanteric)** fractures, not intracapsular neck of femur fractures.
- It is mechanically unsuitable for a **subcapital fracture** and would not provide stable fixation, potentially leading to failure and further complications.
Question 86: A 47-year-old woman presents with a 4-month history of lower back pain and progressive bilateral leg weakness. She has a history of breast cancer treated 18 months ago with mastectomy and adjuvant chemotherapy. MRI demonstrates a soft tissue mass causing spinal canal compromise at T12. Neurological examination reveals grade 4/5 power in both legs, intact sensation, and preserved sphincter function. After commencing dexamethasone, a multidisciplinary team meeting discusses management options. Which factor would most strongly favour surgical decompression over radiotherapy alone as the initial definitive treatment?
A. Single level of spinal involvement
B. Mechanical spinal instability on MRI (Correct Answer)
C. Previous radiotherapy to the thoracic spine
D. Slowly progressive neurological deficit over months
E. Patient is ambulatory at presentation
Explanation: ***Mechanical spinal instability on MRI***- **Mechanical spinal instability** detected on MRI is a primary indication for surgical decompression and stabilization, as **radiotherapy** alone cannot restore structural integrity or prevent further collapse of a compromised vertebral column.- The presence of instability often necessitates surgery to prevent **catastrophic neurological deterioration** and to provide immediate spinal **stabilization**, thereby improving pain and functional outcomes. *Single level of spinal involvement*- While a **single-level lesion** simplifies surgical planning, it does not inherently prioritize surgery over **radiotherapy** if the spine is stable and the tumor is considered radiosensitive.- Many cases of single-level **Metastatic Spinal Cord Compression (MSCC)** can be effectively managed with **radiotherapy** alone, especially when the spinal integrity is preserved. *Previous radiotherapy to the thoracic spine*- Previous **radiotherapy** to the *same* segment (T12) would strongly favor surgery due to the limited **spinal cord tolerance** for re-irradiation, but the question does not specify the exact location of prior radiation.- If the previous radiation was to a *different* level, it would not necessarily preclude **radiotherapy** (e.g., conventional or stereotactic radiosurgery) to the T12 lesion as an initial treatment option. *Slowly progressive neurological deficit over months*- A **slowly progressive neurological deficit** often allows sufficient time for **radiotherapy** to take effect, especially for tumors (like breast cancer) that are typically radiosensitive.- **Acute or rapidly progressive neurological deficits** are stronger indicators for urgent surgical decompression to prevent irreversible neurological damage. *Patient is ambulatory at presentation*- Being **ambulatory** is a strong positive prognostic factor, associated with better functional outcomes regardless of whether surgery or radiotherapy is chosen.- While it signifies preserved neurological function, it is not a specific criterion that mandates surgery over radiotherapy unless accompanied by **spinal instability** or a highly radioresistant tumor.
Question 87: A 67-year-old man undergoes a dynamic hip screw fixation for a stable intertrochanteric femur fracture. The operation is technically successful with good reduction and appropriate implant positioning on intraoperative fluoroscopy. Six months later, he presents with increasing hip pain and difficulty walking. Radiographs show the lag screw has cut out superiorly through the femoral head. Which intraoperative measurement error most likely contributed to this complication?
A. Tip-apex distance greater than 25 mm (Correct Answer)
B. Lag screw positioned in the superior quadrant of the femoral head on AP view
C. Insufficient lag screw length with tip 5 mm from subchondral bone
D. Barrel plate angle of 135 degrees used instead of 150 degrees
E. Lag screw placed anterior to the central axis on lateral view
Explanation: ***Tip-apex distance greater than 25 mm***- The **tip-apex distance (TAD)** is the most critical intraoperative predictor of **lag screw cut-out**; it is the sum of the distances from the screw tip to the femoral head apex on both AP and lateral views.- A **TAD >25 mm** is strongly associated with mechanical failure and superior migration of the screw through the femoral head, as seen in this patient.*Lag screw positioned in the superior quadrant of the femoral head on AP view*- While **superior positioning** is generally avoided, the **TAD** is a more specific and statistically validated measurement for predicting fixation failure.- Correct surgical technique aims for a **center-center** or **inferior-center** position to maximize purchase in the dense trabecular bone.*Insufficient lag screw length with tip 5 mm from subchondral bone*- A tip distance of **5 mm from the subchondral bone** is actually considered an appropriate and safe position to ensure adequate purchase without joint penetration.- Insufficient length usually refers to a distance much greater than 10-15mm, which would limit the **stability** of the construct and increase TAD.*Barrel plate angle of 135 degrees used instead of 150 degrees*- The choice of **plate angle** (typically 135°) is based on the patient's native **neck-shaft angle** and does not directly cause screw cut-out.- A **135-degree plate** is standard for most stable intertrochanteric fractures and provides appropriate dynamic compression.*Lag screw placed anterior to the central axis on lateral view*- **Anterior placement** on the lateral view is suboptimal but is less significantly associated with late cut-out compared to an overall high **TAD**.- Central placement on the **lateral radiograph** is the goal to ensure the screw remains within the thickest part of the femoral neck.
Question 88: A 38-year-old woman presents with a 6-week history of lower back pain and stiffness. She also reports a 2-week history of painful red eyes and worsening vision. She has a past medical history of psoriasis. Blood tests show: CRP 54 mg/L, ESR 42 mm/hr. Which extra-articular manifestation is she currently experiencing?
A. Scleritis
B. Anterior uveitis (Correct Answer)
C. Keratitis
D. Episcleritis
E. Posterior uveitis
Explanation: ***Anterior uveitis***- This patient likely has **psoriatic arthritis** with axial involvement, a type of **spondyloarthropathy** commonly associated with inflammatory eye conditions given her history of psoriasis and inflammatory back pain.- **Anterior uveitis** presents with a **painful red eye**, photophobia, and blurred vision, making it the most frequent extra-articular manifestation in these patients. *Scleritis*- Characterized by severe, **boring pain** that often radiates to the forehead and is more commonly associated with **rheumatoid arthritis** or systemic vasculitis.- It involves deeper layers of the eye than uveitis and typically does not present as a primary feature of axial spondyloarthropathies. *Keratitis*- Refers to **corneal inflammation**, which usually presents with a **foreign body sensation** and discharge rather than primarily inflammatory back pain markers.- It is not typically classified as a systemic extra-articular manifestation of **seronegative spondyloarthropathies** and is often infectious or related to dry eye. *Episcleritis*- Presents as a localized or diffuse **painless red eye** and rarely causes significant changes in vision or high levels of pain.- While it can occur in autoimmune diseases, it is generally **self-limiting** and less severe than the uveitis seen in this clinical scenario. *Posterior uveitis*- Primarily involves the **choroid and retina**, presenting with floaters or vision loss but usually **without the acute pain** and redness seen in anterior involvement.- It is less common in the context of HLA-B27 associated conditions compared to **acute anterior uveitis** and would not typically cause a painful red eye.
Question 89: A 65-year-old man sustains a subcapital neck of femur fracture with posterior comminution after a fall. He is an active independent individual who plays golf twice weekly. He has well-controlled type 2 diabetes and hypertension. Preoperatively, his surgeon discusses the risk of avascular necrosis of the femoral head if internal fixation is performed. In the context of this specific fracture pattern, which feature contributes most significantly to the elevated risk of avascular necrosis?
A. Patient's age over 60 years
B. Presence of posterior comminution (Correct Answer)
C. Time delay between injury and surgery
D. Subcapital location of the fracture
E. Patient's diabetic status
Explanation: ***Presence of posterior comminution*** - **Posterior comminution** indicates a severe mechanical disruption of the **posterior cortex**, which is the primary site through which the **retinacular vessels** (from the **medial circumflex femoral artery**) reach the femoral head. - This specific fracture characteristic is associated with a significantly higher risk of **avascular necrosis (AVN)** because it suggests the majority of the **60-80% blood supply** to the femoral head has been destroyed. *Patient's age over 60 years* - While **age** influences the choice between fixation and arthroplasty, it is a demographic factor rather than a **fracture pattern** characteristic that determines vascular compromise. - Older age is associated with **osteopenia**, which may lead to fixation failure, but it does not inherently cause AVN. *Time delay between injury and surgery* - Although a longer **time to reduction** can exacerbate ischemic damage, it is a perioperative management factor, not a feature of the "**specific fracture pattern**." - Modern evidence suggests that while urgent reduction is preferred, the **initial displacement** and comminution are more predictive of AVN outcome than time. *Subcapital location of the fracture* - All **subcapital fractures** are **intracapsular** and carry a baseline risk of vascular injury because they occur proximal to the vessel insertion. - However, the subcapital location itself is less predictive of poor outcome than the presence of **displacement** or **comminution** within that location. *Patient's diabetic status* - **Diabetes mellitus** increases the risk of **surgical site infection** and poor bone healing (non-union), but it is not the primary mechanism for **post-traumatic AVN**. - It is an important **comorbidity** for overall surgical risk but does not define the mechanical or vascular severity of the femoral neck fracture.
Question 90: A 72-year-old man presents with a 3-month history of lower back pain that has recently started radiating down his right leg to his foot. He describes weakness when trying to push down on the accelerator while driving. On examination, he has weakness of right ankle plantarflexion (4/5 power), reduced sensation over the right lateral foot and sole, and an absent right ankle reflex. Straight leg raise is positive at 40 degrees on the right. Which nerve root is most likely compressed?
A. L3
B. L4
C. L5
D. S1 (Correct Answer)
E. S2
Explanation: ***S1*** - Compression of the **S1 nerve root** is characterized by weakness in **ankle plantarflexion** (gastrocnemius and soleus muscles), which directly explains the difficulty with pushing an accelerator pedal. - Sensory loss for an **S1 lesion** is classically found over the **lateral foot and sole**, and it is associated with a diminished or absent **Achilles (ankle) reflex**. *L3* - **L3 nerve root** compression primarily affects **knee extension** via the quadriceps and causes sensory loss over the **anterior/medial thigh**. - It is associated with a diminished **patellar reflex** (L3-L4), not the absent ankle reflex seen in this patient. *L4* - An **L4 radiculopathy** typically leads to weakness in **ankle dorsiflexion** and **knee extension**, with sensory changes over the **medial calf** and ankle. - This level is also assessed via the **patellar reflex**, which is inconsistent with the absent Achilles reflex in this case. *L5* - **L5 nerve root** compression often results in weakness of **big toe extension** (extensor hallucis longus) and foot **eversion**, leading to a foot drop. - Sensory loss occurs over the **dorsum of the foot** and the **first web space**, and there is no distinct reflex commonly tested for L5 alone. *S2* - **S2 compression** is less common and primarily presents with sensory loss over the **posterior thigh** and popliteal fossa. - While it contributes to plantarflexion, isolated **S2 lesions** would not typically present with the specific lateral foot sensory loss and absent ankle reflex that are hallmark signs of S1 involvement.
