A 35-year-old man presents to the Emergency Department with sudden onset severe lower back pain that began 4 hours ago while lifting a heavy box at work. The pain radiates down the posterior aspect of his left leg to the lateral border of his foot. He has difficulty walking on his toes on the left side. On examination, there is reduced sensation over the lateral border and dorsum of the left foot, and weakness of plantarflexion on the left. Straight leg raise is positive at 30 degrees on the left. Which nerve root is most likely to be affected?
Q122
A 58-year-old woman with known metastatic breast cancer presents with a 5-week history of progressively worsening lower back pain. The pain is constant, unrelieved by rest, and wakes her from sleep. She has noticed some weakness in her legs over the past week, particularly when climbing stairs. On examination, there is tenderness over L3 vertebra, reduced power (4/5) in both lower limbs, brisk knee reflexes bilaterally, and upgoing plantars. Anal tone is normal. What is the most appropriate immediate management?
Q123
What is the approximate incidence of deep vein thrombosis in patients with neck of femur fractures who do not receive thromboprophylaxis?
Q124
A 70-year-old man sustains an undisplaced Garden I intracapsular neck of femur fracture following a fall. He is an active man who plays golf regularly and lives independently. He has no significant past medical history. The orthopaedic team decides to proceed with internal fixation using cannulated screws. In which configuration should the cannulated screws ideally be inserted to provide optimal biomechanical stability?
Q125
A 47-year-old woman presents with a 12-week history of lower back pain and stiffness. She describes the pain as worst first thing in the morning, with stiffness lasting approximately 90 minutes that improves with exercise. She also reports pain in both heels when she first stands. On examination, there is reduced lumbar spine flexion with a Schober's test measurement of 3 cm (normal >5 cm). Which of the following investigation findings would be most specific for confirming the suspected underlying diagnosis?
Q126
An 81-year-old woman sustains a displaced intracapsular neck of femur fracture. She has severe dementia with an Abbreviated Mental Test Score of 2/10 and was living in a nursing home with full care prior to admission. She has multiple comorbidities including chronic kidney disease stage 4, congestive heart failure, and previous stroke with residual right-sided weakness. The orthogeriatric team is considering whether surgery is appropriate. Which of the following factors is the strongest relative indication for non-operative management in this patient?
Q127
A 52-year-old man with a history of intravenous drug use presents to the Emergency Department with a 10-day history of severe lower back pain, fever, and night sweats. He has been unable to work for the past week due to the pain. Temperature is 38.7°C. On examination, there is marked tenderness over the lumbar spine. Blood tests show WBC 14.2 × 10⁹/L, CRP 156 mg/L, and ESR 78 mm/hr. What is the most appropriate next step in the management of this patient?
Q128
A 76-year-old man sustains a Garden III intracapsular neck of femur fracture following a fall. He has a past medical history of atrial fibrillation, hypertension, and type 2 diabetes mellitus. His pre-injury mobility was independent with a walking stick outdoors. The orthopaedic team decides to proceed with a cemented hemiarthroplasty. What is the primary reason for using bone cement in this patient's procedure?
Q129
A 40-year-old woman presents to her GP with an 8-week history of lower back pain. She works as a cleaner and describes the pain as dull and aching, worse at the end of her working day. She has noticed some early morning stiffness lasting about 10 minutes. She denies any leg pain, bladder or bowel symptoms. On examination, lumbar spine movements are mildly restricted but neurological examination is normal. Which of the following features would be considered a red flag requiring urgent investigation?
Q130
A 74-year-old woman presents to the Emergency Department following a fall from standing height. She complains of right hip pain and inability to weight-bear. On examination, the right lower limb is shortened, abducted and externally rotated. Radiographs confirm a displaced intracapsular neck of femur fracture. Which of the following best describes the mechanism by which avascular necrosis occurs following this injury?
Orthopaedics & MSK UK Medical PG Practice Questions and MCQs
Question 121: A 35-year-old man presents to the Emergency Department with sudden onset severe lower back pain that began 4 hours ago while lifting a heavy box at work. The pain radiates down the posterior aspect of his left leg to the lateral border of his foot. He has difficulty walking on his toes on the left side. On examination, there is reduced sensation over the lateral border and dorsum of the left foot, and weakness of plantarflexion on the left. Straight leg raise is positive at 30 degrees on the left. Which nerve root is most likely to be affected?
A. L3
B. L4
C. L5
D. S1 (Correct Answer)
E. S2
Explanation: ***S1***
- Compression of the **S1 nerve root** typically occurs at the **L5-S1 disc** level and leads to weakness in **plantarflexion**, making it difficult for patients to **walk on their toes**.
- Sensory loss occurs along the **lateral border of the foot** and posterior leg, often accompanied by a diminished or absent **Achilles tendon reflex**.
*L3*
- **L3 nerve root** compression typically presents with weakness in **hip flexion** and **knee extension** (quadriceps).
- Sensory deficit is usually localized to the **anterior thigh**, and the **patellar reflex** may be diminished.
*L4*
- The **L4 nerve root** provides motor innervation for **knee extension** and sensation to the **medial shin** and medial malleolus.
- A classic clinical finding for L4 pathology is a diminished **patellar reflex** (knee-jerk).
*L5*
- **L5 nerve root** compression results in weakness of **big toe extension** (extensor hallucis longus) and **foot dorsiflexion**, causing difficulty **walking on heels**.
- Sensory loss is typically found on the **dorsum of the foot**, particularly in the **first web space** between the first and second toes.
*S2*
- Compression of the **S2 nerve root** is relatively rare and usually presents with sensory changes along the **posterior thigh** and calf.
- It is more commonly associated with complex syndromes like **cauda equina syndrome** if bladder or bowel dysfunction is present.
Question 122: A 58-year-old woman with known metastatic breast cancer presents with a 5-week history of progressively worsening lower back pain. The pain is constant, unrelieved by rest, and wakes her from sleep. She has noticed some weakness in her legs over the past week, particularly when climbing stairs. On examination, there is tenderness over L3 vertebra, reduced power (4/5) in both lower limbs, brisk knee reflexes bilaterally, and upgoing plantars. Anal tone is normal. What is the most appropriate immediate management?
A. Admit for urgent MRI whole spine and commence high-dose dexamethasone (Correct Answer)
B. Arrange urgent outpatient MRI lumbar spine within 48 hours and follow-up in clinic
C. Commence oral analgesia and arrange routine oncology follow-up within 2 weeks
D. Request plain radiographs of lumbar spine to assess for pathological fracture
E. Arrange urgent CT lumbar spine to identify the site of spinal metastasis
Explanation: ***Admit for urgent MRI whole spine and commence high-dose dexamethasone*** - This patient presents with clear signs of **Metastatic Spinal Cord Compression (MSCC)**, an oncological emergency characterized by **progressive back pain**, **motor weakness**, and **upper motor neuron signs** (brisk reflexes, upgoing plantars). - Immediate management requires **high-dose dexamethasone** to reduce peritumoural edema and an **urgent MRI of the whole spine** (within 24 hours), as skip lesions can occur in up to 20% of cases. *Arrange urgent outpatient MRI lumbar spine within 48 hours and follow-up in clinic* - Outpatient management is inappropriate for suspected **MSCC**, as it is an emergency that can lead to irreversible paralysis if not treated promptly. - Imaging only the **lumbar spine** is insufficient; a **whole spine MRI** is crucial to identify all sites of compression, including potential skip lesions. *Commence oral analgesia and arrange routine oncology follow-up within 2 weeks* - Delaying definitive management for two weeks in a patient with **progressive neurological deficits** and alarming pain features risks permanent loss of motor function and bowel/bladder control. - While **analgesia** is important for comfort, it does not address the underlying **spinal cord compression** which requires immediate investigation and treatment. *Request plain radiographs of lumbar spine to assess for pathological fracture* - **Plain radiographs** have very low sensitivity for detecting spinal cord compression and cannot visualize the spinal cord or degree of **thecal sac compromise**. - A normal X-ray does not rule out **MSCC** and should never delay the definitive gold-standard investigation, which is an **MRI**. *Arrange urgent CT lumbar spine to identify the site of spinal metastasis* - **CT scans** are excellent for evaluating bony pathology but are significantly less sensitive than **MRI** for visualizing **soft tissue masses** and the spinal cord itself. - Relying on a **CT lumbar spine** may miss the actual level of compression or additional sites of disease, especially since upper motor neuron signs often indicate a lesion above the lumbar spine.
Question 123: What is the approximate incidence of deep vein thrombosis in patients with neck of femur fractures who do not receive thromboprophylaxis?
A. 5-10%
B. 15-20%
C. 30-40%
D. 50-60% (Correct Answer)
E. 70-80%
Explanation: ***50-60%***- In the absence of **thromboprophylaxis**, the incidence of **Deep Vein Thrombosis (DVT)** in patients with **neck of femur fractures** is extremely high, ranging between 50-60%.- This elevated risk is driven by **Virchow's Triad**, specifically **venous stasis** from immobility and the **hypercoagulable state** triggered by trauma and major orthopedic surgery.*5-10%*- This range significantly underestimates the risk in high-risk orthopedic surgeries and is more characteristic of low-risk minor procedures.- At this low level, the clinical urgency for mandatory **pharmacological prophylaxis** (like LMWH) would not be as critical as it is for hip fractures.*15-20%*- While this reflects a higher risk than general surgery, it still falls short of the true incidence seen in untreated **proximal femur fractures**.- This percentage is closer to the risk observed in some medical patients with **congestive heart failure** or severe respiratory disease, rather than major orthopedic trauma.*30-40%*- This range is more typical for patients undergoing **total knee replacement** or elective hip arthroplasty without prophylaxis, rather than fracture patients.- **Neck of femur fracture** patients often have higher risks due to the immediate **endothelial injury** from the trauma itself and delayed time to surgery.*70-80%*- Although the risk is very high, an incidence of 70-80% is generally considered an overestimation for **venographic DVT** in standard clinical studies of hip fractures.- Most clinical literature and guidelines, such as **NICE**, benchmark the untreated risk at approximately 50-60% for DVT and 2-5% for **fatal pulmonary embolism**.
Question 124: A 70-year-old man sustains an undisplaced Garden I intracapsular neck of femur fracture following a fall. He is an active man who plays golf regularly and lives independently. He has no significant past medical history. The orthopaedic team decides to proceed with internal fixation using cannulated screws. In which configuration should the cannulated screws ideally be inserted to provide optimal biomechanical stability?
A. Three screws in a triangular configuration with the apex positioned inferiorly (Correct Answer)
B. Two screws positioned parallel to each other in the sagittal plane
C. Three screws in a triangular configuration with the apex positioned posteriorly
D. Four screws in a square configuration to maximize bone purchase
E. Three screws in a vertical linear arrangement along the femoral neck axis
Explanation: ***Three screws in a triangular configuration with the apex positioned inferiorly***- For **Garden I fractures**, three parallel screws in an **inverted triangle** pattern provide optimal biomechanical stability by maximizing the **moment arm** and resistance to shear forces.- Placing the **apex screw inferiorly** (resting on the calcar) and the other two superiorly ensures superior **rotational stability** and compression across the fracture site.*Two screws positioned parallel to each other in the sagittal plane*- Using only two screws provides significantly less **rotational control** and is biomechanically inferior for resisting **varus forces** compared to three screws.- Clinical guidelines generally recommend a minimum of three screws for stable internal fixation of **intracapsular femoral neck** fractures.*Three screws in a triangular configuration with the apex positioned posteriorly*- This configuration does not provide the same level of **coronal plane stability** as the inverted triangle with the apex inferiorly.- The apex screw must be positioned against the **inferior cortex (calcar)** to provide the strongest support against weight-bearing stresses.*Four screws in a square configuration to maximize bone purchase*- While a fourth screw may be used in **basicervical fractures**, it is not standard for subcapital fractures as it increases the risk of **femoral head devascularization**.- Adding a fourth screw overcrowding the femoral head can lead to iatrogenic damage without providing a significant increase in **mechanical strength**.*Three screws in a vertical linear arrangement along the femoral neck axis*- A linear arrangement offers very poor resistance to **rotational torque**, which is crucial for preventing fracture displacement during movement.- The lack of **divergence/triangulation** in the screw placement limits the ability to counteract multi-planar forces acting on the hip joint.
Question 125: A 47-year-old woman presents with a 12-week history of lower back pain and stiffness. She describes the pain as worst first thing in the morning, with stiffness lasting approximately 90 minutes that improves with exercise. She also reports pain in both heels when she first stands. On examination, there is reduced lumbar spine flexion with a Schober's test measurement of 3 cm (normal >5 cm). Which of the following investigation findings would be most specific for confirming the suspected underlying diagnosis?
A. Raised serum C-reactive protein and erythrocyte sedimentation rate
B. Sacroiliitis demonstrated on plain radiographs of the pelvis (Correct Answer)
C. Positive HLA-B27 antigen on genetic testing
D. Reduced lumbar spine bone mineral density on DEXA scanning
E. Bamboo spine appearance on lateral lumbar spine radiograph
Explanation: ***Sacroiliitis demonstrated on plain radiographs of the pelvis***
- This is the **hallmark radiological finding** in ankylosing spondylitis and is a key diagnostic criterion in the **Modified New York Criteria** for definite AS.
- Early changes include **erosions**, **sclerosis**, and eventually **fusion** of the sacroiliac joints, confirming axial involvement.
*Raised serum C-reactive protein and erythrocyte sedimentation rate*
- While **inflammatory markers** (CRP, ESR) are often elevated in active ankylosing spondylitis, they are **nonspecific** and can be raised in many other inflammatory or infectious conditions.
- A significant proportion (up to 50%) of patients with active AS may have **normal inflammatory markers**, making them unsuitable as a specific diagnostic test.
*Positive HLA-B27 antigen on genetic testing*
- **HLA-B27** is strongly associated with ankylosing spondylitis, being present in about 90% of patients, but its **specificity is low** as it is also found in 5-10% of the general population without AS.
- Therefore, a positive result supports the diagnosis in the right clinical context but is **not diagnostic on its own** and not as specific as radiographic sacroiliitis.
*Reduced lumbar spine bone mineral density on DEXA scanning*
- **Osteoporosis** and osteopenia are common complications in ankylosing spondylitis, often due to chronic inflammation, reduced mobility, and sometimes corticosteroid use.
- However, reduced **bone mineral density** is a secondary finding and not a specific diagnostic feature for the initial confirmation of ankylosing spondylitis itself.
*Bamboo spine appearance on lateral lumbar spine radiograph*
- The "bamboo spine" appearance is a characteristic feature of **advanced ankylosing spondylitis**, resulting from extensive **syndesmophyte formation** and fusion of vertebral bodies.
- While highly specific, this finding typically occurs in **late-stage disease** and is unlikely to be present in a patient with a 12-week history, making it less relevant for initial confirmation.
Question 126: An 81-year-old woman sustains a displaced intracapsular neck of femur fracture. She has severe dementia with an Abbreviated Mental Test Score of 2/10 and was living in a nursing home with full care prior to admission. She has multiple comorbidities including chronic kidney disease stage 4, congestive heart failure, and previous stroke with residual right-sided weakness. The orthogeriatric team is considering whether surgery is appropriate. Which of the following factors is the strongest relative indication for non-operative management in this patient?
A. The presence of severe cognitive impairment with AMTS of 2/10
B. Complete loss of independent mobility prior to the fracture (Correct Answer)
C. Chronic kidney disease stage 4 with estimated GFR of 22 ml/min
D. Advanced age of 81 years at time of fracture
E. Previous stroke with residual hemiparesis
Explanation: ***Complete loss of independent mobility prior to the fracture***
- The primary goal of hip fracture surgery is to restore **functional mobility**; if a patient was already bed-bound or chair-bound, the functional benefit of surgery is virtually non-existent.
- **NICE guidelines** suggest that non-operative management is mostly reserved for those who are medically unfit for any anesthesia or those whose pre-injury **non-ambulatory status** makes surgical risks outweigh clinical benefits.
*The presence of severe cognitive impairment with AMTS of 2/10*
- **Dementia** is not a contraindication to surgery; in fact, surgery often facilitates better pain management and nursing care in this population to prevent **delirium**.
- Studies indicate that patients with cognitive impairment still benefit from **early mobilization** and stabilization of the fracture to reduce the risk of pressure sores.
*Chronic kidney disease stage 4 with estimated GFR of 22 ml/min*
- While **CKD stage 4** increases the risk of perioperative complications like electrolyte imbalances, it is a manageable **comorbidity** rather than a reason to omit surgery.
- Multidisciplinary care involving an **orthogeriatrician** and renal specialist can optimize the patient for a safe surgical outcome.
*Advanced age of 81 years at time of fracture*
- **Chronological age** is not a relative indication for non-operative management; physiological status and **frailty** are more pertinent factors.
- Many patients in their 80s and 90s undergo successful **hemiarthroplasty** or internal fixation, maintaining their pre-morbid quality of life.
*Previous stroke with residual hemiparesis*
- **Residual weakness** from a stroke does not preclude surgery unless it resulted in a total loss of mobility prior to the fall.
- Effective surgery identifies the best method to stabilize the hip to allow whatever **functional movement** the patient had remaining to be preserved.
Question 127: A 52-year-old man with a history of intravenous drug use presents to the Emergency Department with a 10-day history of severe lower back pain, fever, and night sweats. He has been unable to work for the past week due to the pain. Temperature is 38.7°C. On examination, there is marked tenderness over the lumbar spine. Blood tests show WBC 14.2 × 10⁹/L, CRP 156 mg/L, and ESR 78 mm/hr. What is the most appropriate next step in the management of this patient?
A. Start empirical broad-spectrum intravenous antibiotics and arrange urgent MRI spine (Correct Answer)
B. Arrange an urgent CT-guided biopsy of the lumbar spine before starting antibiotics
C. Discharge with oral antibiotics and arrange outpatient MRI within 2 weeks
D. Arrange plain radiographs of the lumbar spine to guide further management
E. Perform a lumbar puncture to exclude meningitis before further investigation
Explanation: ***Start empirical broad-spectrum intravenous antibiotics and arrange urgent MRI spine***
- The patient exhibits classic signs of **pyogenic vertebral osteomyelitis/discitis**, including **fever**, **spinal tenderness**, and **intravenous drug use** history, requiring immediate hospitalization and imaging.
- **MRI spine** is the gold-standard investigation for diagnosis due to its high sensitivity for detecting **bone marrow edema** and potential **spinal epidural abscesses**.
*Arrange an urgent CT-guided biopsy of the lumbar spine before starting antibiotics*
- While a **biopsy** is crucial for definitive organism identification, it should not delay initiating **empirical broad-spectrum antibiotics** in a **systemically unwell** patient with high inflammatory markers.
- **Blood cultures** should be obtained immediately to attempt pathogen identification, but **empirical antibiotics** take priority when **sepsis** or **neurological compromise** is a risk.
*Discharge with oral antibiotics and arrange outpatient MRI within 2 weeks*
- Discharge is inappropriate given the **red flag symptoms** of a potential spinal infection and the high risk of permanent **neurological damage** or **sepsis**.
- **Oral antibiotics** provide insufficient penetration and coverage compared to **intravenous therapy** required for deep-seated bone infections.
*Arrange plain radiographs of the lumbar spine to guide further management*
- **Plain radiographs** have very low sensitivity in the early stages of osteomyelitis, as bony changes like **disc space narrowing** may not appear for 2-4 weeks.
- A normal X-ray cannot rule out **spinal infection**, making it a poor choice for guiding acute management in a symptomatic patient.
*Perform a lumbar puncture to exclude meningitis before further investigation*
- The primary clinical finding is **localized spinal tenderness** and back pain, which points toward a **vertebral infection** rather than primary meningitis.
- **Lumbar puncture** is not indicated here and could potentially be dangerous if a **spinal epidural abscess** is present at the needle entry site.
Question 128: A 76-year-old man sustains a Garden III intracapsular neck of femur fracture following a fall. He has a past medical history of atrial fibrillation, hypertension, and type 2 diabetes mellitus. His pre-injury mobility was independent with a walking stick outdoors. The orthopaedic team decides to proceed with a cemented hemiarthroplasty. What is the primary reason for using bone cement in this patient's procedure?
A. To reduce the risk of periprosthetic infection by providing antibiotic delivery
B. To improve immediate mechanical stability and allow earlier mobilisation (Correct Answer)
C. To reduce the operative time compared to uncemented fixation techniques
D. To decrease the risk of intraoperative femoral shaft fracture during implantation
E. To provide better long-term osseointegration of the prosthesis
Explanation: ***To improve immediate mechanical stability and allow earlier mobilisation***- **Cemented hemiarthroplasty** provides immediate, rigid fixation, which is crucial for allowing elderly patients with comorbidities to achieve **early weight-bearing** and mobility post-surgery.- Early **mobilisation** is paramount in older hip fracture patients to prevent life-threatening complications such as **pneumonia**, **venous thromboembolism (VTE)**, and pressure sores.*To reduce the risk of periprosthetic infection by providing antibiotic delivery*- While **antibiotic-loaded cement** can offer local antimicrobial protection, this is a secondary benefit rather than the primary mechanical reason for its use.- Intravenous **prophylactic antibiotics** remain the standard primary prevention strategy for surgical site infections, irrespective of cement use.*To reduce the operative time compared to uncemented fixation techniques*- Cementing actually tends to **increase operative time** because the surgeon must wait for the bone cement to cure (harden) before proceeding.- **Uncemented** implants might be faster to insert but carry higher risks of postoperative thigh pain and periprosthetic fractures, especially in osteoporotic bone.*To decrease the risk of intraoperative femoral shaft fracture during implantation*- The use of cement does not necessarily decrease the risk; in fact, the **pressurization of cement** and insertion of the stem can potentially **increase the risk of fracture** in fragile, osteoporotic bone.- Conversely, **uncemented** stems also pose a risk of femoral shaft fracture during the **press-fit** insertion process.*To provide better long-term osseointegration of the prosthesis*- **Osseointegration** is a biological process where bone grows into a porous coating, which is characteristic of **uncemented** implants over several weeks.- **Cemented** implants rely on a **mechanical interlock** between the cement and the cancellous bone for fixation, rather than biological bone ingrowth.
Question 129: A 40-year-old woman presents to her GP with an 8-week history of lower back pain. She works as a cleaner and describes the pain as dull and aching, worse at the end of her working day. She has noticed some early morning stiffness lasting about 10 minutes. She denies any leg pain, bladder or bowel symptoms. On examination, lumbar spine movements are mildly restricted but neurological examination is normal. Which of the following features would be considered a red flag requiring urgent investigation?
A. Age less than 55 years at presentation
B. Morning stiffness lasting less than 30 minutes
C. Pain worse with activity and better with rest
D. Progressive thoracic kyphosis with restriction of chest expansion (Correct Answer)
E. Symptoms duration of 8 weeks
Explanation: ***Progressive thoracic kyphosis with restriction of chest expansion***- A structural deformity or significant loss of spinal mobility suggests serious underlying pathology such as **ankylosing spondylitis** or a **vertebral fracture**, which are red flags.- **Chest expansion restricted** to less than 2.5 cm is a specific clinical sign used to screen for chronic inflammatory spondyloarthropathies.*Age less than 55 years at presentation*- Presentation between the ages of **20 and 55 years** is typically associated with mechanical back pain rather than systemic or neoplastic causes.- A first-time presentation of back pain is only considered a **red flag** if the patient is **younger than 20** or **older than 55** years.*Morning stiffness lasting less than 30 minutes*- Brief morning stiffness is a classic feature of **mechanical back pain** or osteoarthritis rather than inflammatory conditions.- Inflammatory back pain (a red flag category) is characterized by **morning stiffness** lasting **longer than 30-60 minutes** that improves with activity.*Pain worse with activity and better with rest*- This pattern is typical of **mechanical back pain**, which is common in manual workers like cleaners and does not usually require urgent investigation.- Back pain that is **unrelieved by rest**, worse at night, or improves significantly with exercise may indicate **malignancy** or **inflammatory arthritis**.*Symptoms duration of 8 weeks*- A duration of 8 weeks classifies the pain as **subacute**; while persistent, it is not a red flag in the absence of weight loss, night pain, or neurological deficits.- **Chronic duration** without progressive worsening or other "B" symptoms usually points toward benign musculoskeletal etiologies rather than urgent surgical or medical emergencies.
Question 130: A 74-year-old woman presents to the Emergency Department following a fall from standing height. She complains of right hip pain and inability to weight-bear. On examination, the right lower limb is shortened, abducted and externally rotated. Radiographs confirm a displaced intracapsular neck of femur fracture. Which of the following best describes the mechanism by which avascular necrosis occurs following this injury?
A. Damage to the deep circumflex iliac artery leading to ischaemia of the femoral head
B. Disruption of the retinacular vessels which are the primary blood supply to the femoral head (Correct Answer)
C. Compression of the obturator artery within the ligamentum teres causing reduced perfusion
D. Thrombosis of the profunda femoris artery secondary to the trauma
E. Venous congestion causing back-pressure and reduced arterial inflow to the femoral head
Explanation: ***Disruption of the retinacular vessels which are the primary blood supply to the femoral head***
- In **displaced intracapsular neck of femur fractures**, the delicate **retinacular vessels**, which are branches of the medial and lateral circumflex femoral arteries, are often torn or severely compressed.
- These vessels are the **primary blood supply** to the **femoral head** in adults, and their disruption directly leads to **avascular necrosis (AVN)**.
*Damage to the deep circumflex iliac artery leading to ischaemia of the femoral head*
- The **deep circumflex iliac artery** primarily supplies the **iliac crest** and muscles of the abdominal wall, not the femoral head.
- Its damage would not directly cause **ischaemia** of the femoral head following an intracapsular hip fracture.
*Compression of the obturator artery within the ligamentum teres causing reduced perfusion*
- The **artery of the ligamentum teres**, a branch of the **obturator artery**, provides only a **minor and often negligible** blood supply to the femoral head in adults.
- It is usually **insufficient** to prevent **avascular necrosis** when the main retinacular supply is compromised.
*Thrombosis of the profunda femoris artery secondary to the trauma*
- The **profunda femoris artery** (deep femoral artery) is a major artery supplying the **thigh muscles** and gives rise to the circumflex femoral arteries.
- A **thrombosis** of the main profunda femoris artery would lead to widespread **lower limb ischaemia**, rather than isolated **femoral head AVN**.
*Venous congestion causing back-pressure and reduced arterial inflow to the femoral head*
- While increased **intracapsular pressure** can contribute to impaired perfusion, the primary mechanism for **AVN** in **displaced intracapsular fractures** is the direct **mechanical disruption and tearing** of the arterial supply.
- **Venous congestion** is not the leading cause for the high incidence of **avascular necrosis** in these types of severe fractures.
