Orthopaedics & MSK — MCQs
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A 49-year-old woman with a history of systemic lupus erythematosus treated with long-term prednisolone presents with insidious onset hip pain over 8 months. The pain is worse with weight-bearing and she has developed a limp. Plain radiographs show a crescent sign in the femoral head with some collapse of the articular surface. Blood tests show normal inflammatory markers. What is the underlying pathological process?
An 81-year-old man with severe aortic stenosis (valve area 0.7 cm², mean gradient 52 mmHg) and NYHA class III heart failure sustains a displaced intracapsular neck of femur fracture. His cardiologist states he is not a candidate for valve replacement due to frailty and comorbidities. The patient was independently mobile pre-injury using a frame. Which surgical option represents the best balance of risk and functional outcome?
A 62-year-old woman presents with a 5-month history of lower back pain radiating down the posterior aspect of her left leg to the heel. The pain is worse with prolonged sitting and improves with standing. She describes numbness over the lateral border of her left foot. On examination, she can walk on her heels but has difficulty walking on her toes on the left side. Ankle reflex is absent on the left. Which nerve root is most likely affected?
A 70-year-old man undergoes total hip replacement for a displaced intracapsular neck of femur fracture. He has a history of recurrent venous thromboembolism and is on long-term warfarin with INR consistently in range (2.0-3.0). What is the most appropriate venous thromboembolism (VTE) prophylaxis regimen post-operatively?
A 51-year-old woman with metastatic breast cancer presents with a 3-week history of thoracic back pain and new onset difficulty walking. On examination, she has a sensory level at T8, grade 3/5 power in both legs, and brisk knee and ankle reflexes. Bladder scan shows 400 mL residual volume post-void. She was due to start radiotherapy next week. What is the most appropriate immediate management?
A 68-year-old woman sustains a basicervical neck of femur fracture. Pre-injury she was independently mobile with a walking stick. She has a history of osteoporosis, chronic kidney disease stage 3b (eGFR 38 mL/min/1.73m²), and well-controlled heart failure. Which surgical management option is most appropriate?
A 43-year-old man with a 6-month history of chronic lower back pain and morning stiffness lasting over 90 minutes presents with new onset right heel pain. He mentions having had three episodes of acute unilateral red eye in the past two years. Examination reveals reduced lumbar spine flexion (Schober's test: 3 cm expansion from 15 cm). Blood tests show CRP 42 mg/L, ESR 38 mm/hr, and he is HLA-B27 positive. What is the most appropriate initial imaging investigation for his back pain?
A 75-year-old man with an intertrochanteric neck of femur fracture undergoes dynamic hip screw fixation. Post-operatively, which measurement on the anteroposterior hip radiograph best predicts the stability of the fixation and risk of cut-out of the lag screw?
A 57-year-old man with prostate cancer presents with a 4-week history of progressive lower back pain, worse at night. He reports new onset difficulty initiating urination and constipation. On examination, he has tenderness over T12-L1, and lower limb neurology reveals hyperreflexia with bilateral upgoing plantars. Perianal sensation is intact. What is the most likely level of pathology?
What is the mechanism by which the medial circumflex femoral artery is most commonly injured during a displaced intracapsular neck of femur fracture?
Orthopaedics & MSK UK Medical PG Practice Questions and MCQs
Question 101: A 49-year-old woman with a history of systemic lupus erythematosus treated with long-term prednisolone presents with insidious onset hip pain over 8 months. The pain is worse with weight-bearing and she has developed a limp. Plain radiographs show a crescent sign in the femoral head with some collapse of the articular surface. Blood tests show normal inflammatory markers. What is the underlying pathological process?
- A. Septic arthritis of the hip joint
- B. Inflammatory arthropathy secondary to lupus
- C. Avascular necrosis of the femoral head (Correct Answer)
- D. Osteoarthritis secondary to joint incongruity
- E. Stress fracture of the femoral neck
Explanation: ***Avascular necrosis of the femoral head*** - The patient's history of **systemic lupus erythematosus (SLE)** and **long-term prednisolone** (corticosteroid use) are major risk factors for **avascular necrosis (AVN)**. - The **insidious onset hip pain** worse with weight-bearing, a limp, and the characteristic **crescent sign** on radiographs (indicating subchondral collapse) with subsequent articular surface collapse, are all highly indicative of AVN. *Septic arthritis of the hip joint* - Typically presents with **acute onset** severe pain, often accompanied by fever and significantly **elevated inflammatory markers**, which are absent in this case. - The chronic, insidious nature of the pain (8 months) and normal inflammatory markers make septic arthritis very unlikely. *Inflammatory arthropathy secondary to lupus* - While SLE can cause arthropathy, it usually presents as a **non-erosive polyarthritis** of smaller joints, not isolated hip pain with **femoral head collapse** and a **crescent sign**. - Lupus-related joint inflammation does not typically cause the specific radiographic features of bone necrosis and structural collapse seen here. *Osteoarthritis secondary to joint incongruity* - **Osteoarthritis** is a common consequence of chronic joint incongruity or damage, including that caused by AVN; however, it is a **secondary process** rather than the primary underlying pathology in this scenario. - The **crescent sign** and specific pattern of articular collapse point to AVN as the initiating event, with osteoarthritis developing later. *Stress fracture of the femoral neck* - A **stress fracture** typically presents as pain in the femoral neck, often with a different radiological appearance, such as a **linear lucency** or sclerosis. - It would not typically cause a **crescent sign** or the widespread collapse of the femoral head articular surface characteristic of avascular necrosis.
Question 102: An 81-year-old man with severe aortic stenosis (valve area 0.7 cm², mean gradient 52 mmHg) and NYHA class III heart failure sustains a displaced intracapsular neck of femur fracture. His cardiologist states he is not a candidate for valve replacement due to frailty and comorbidities. The patient was independently mobile pre-injury using a frame. Which surgical option represents the best balance of risk and functional outcome?
- A. Non-operative management with early mobilization
- B. Cannulated screw fixation under local anaesthesia
- C. Cemented hemiarthroplasty under general anaesthesia
- D. Uncemented hemiarthroplasty under spinal anaesthesia (Correct Answer)
- E. Total hip replacement under regional anaesthesia
Explanation: ***Uncemented hemiarthroplasty under spinal anaesthesia***- This approach avoids **bone cement implantation syndrome (BCIS)**, which can cause sudden reductions in systemic vascular resistance and catastrophic **cardiovascular collapse** in patients with fixed cardiac output from **aortic stenosis**.- **Spinal anaesthesia** is often preferred in high-risk cardiac patients to avoid the haemodynamic fluctuations associated with **general anaesthesia** and positive pressure ventilation.*Non-operative management with early mobilization*- This leads to extremely high **morbidity and mortality** in mobile patients due to complications of immobility like **pressure sores**, **pneumonia**, and **venous thromboembolism**.- It does not address the severe pain of a **displaced fracture**, preventing any meaningful functional mobilization.*Cannulated screw fixation under local anaesthesia*- **Cannulated screws** have a very high failure rate, including **non-union** and **avascular necrosis**, in displaced intracapsular fractures of the elderly.- While less invasive, it provides insufficient stability for **immediate weight-bearing**, which is essential for surviving a hip fracture at age 81.*Cemented hemiarthroplasty under general anaesthesia*- Cementing is typically preferred for better fixation, but the risk of **BCIS** is critically high in a patient with a **valve area of 0.7 cm²** and heart failure.- **General anaesthesia** and cement-induced hypotension can lead to fatal **myocardial ischemia** or arrest in the setting of severe, fixed-obstruction **aortic stenosis**.*Total hip replacement under regional anaesthesia*- **Total hip replacement** is an overly extensive procedure for a patient who was already using a **walking frame** pre-injury and has significant cardiac frailty.- It involves longer **operative time** and higher **blood loss**, which this patient's cardiovascular system cannot tolerate.
Question 103: A 62-year-old woman presents with a 5-month history of lower back pain radiating down the posterior aspect of her left leg to the heel. The pain is worse with prolonged sitting and improves with standing. She describes numbness over the lateral border of her left foot. On examination, she can walk on her heels but has difficulty walking on her toes on the left side. Ankle reflex is absent on the left. Which nerve root is most likely affected?
- A. L3
- B. L4
- C. L5
- D. S1 (Correct Answer)
- E. S2
Explanation: ***S1*** - The patient exhibits classic signs of **S1 radiculopathy**, including weakness in **plantarflexion** (difficulty walking on toes) and an **absent ankle reflex**. - Sensory findings such as numbness on the **lateral border of the foot** and pain radiating to the **heel** correspond specifically to the **S1 dermatome**. *L3* - **L3 nerve root** involvement typically causes pain and numbness in the **anterior thigh** and medial knee area. - It is associated with weakness in **hip flexion** or **knee extension**, rather than the distal foot findings seen here. *L4* - **L4 radiculopathy** presents with a **diminished knee (patellar) reflex** and pain radiating to the **medial malleolus**. - Primary motor weakness involves **foot inversion** and knee extension, but this patient can walk on her heels (dorsiflexion intact). *L5* - **L5 nerve root** compression typically results in weakness of **great toe extension** (extensor hallucis longus) and difficulty with **heel walking**. - It primarily affects sensation on the **dorsal surface** of the foot and does not involve the ankle reflex. *S2* - **S2 radiculopathy** is much less common and typically involves the **posterior thigh** and popliteal fossa rather than the heel. - It is more closely associated with **perineal sensation** and contributes to the **anal wink reflex** rather than the ankle reflex.
Question 104: A 70-year-old man undergoes total hip replacement for a displaced intracapsular neck of femur fracture. He has a history of recurrent venous thromboembolism and is on long-term warfarin with INR consistently in range (2.0-3.0). What is the most appropriate venous thromboembolism (VTE) prophylaxis regimen post-operatively?
- A. Continue warfarin alone with target INR 2.0-3.0 (Correct Answer)
- B. Stop warfarin and commence therapeutic dose low molecular weight heparin (LMWH)
- C. Stop warfarin and commence prophylactic dose LMWH until mobile
- D. Continue warfarin and add prophylactic dose LMWH
- E. Stop warfarin, commence direct oral anticoagulant (DOAC) at prophylactic dose
Explanation: ***Continue warfarin alone with target INR 2.0-3.0*** - For patients already on **long-term therapeutic anticoagulation**, such as warfarin for recurrent VTE, continuing the established regimen post-operatively provides sufficient prophylaxis against new events. - NICE guidelines (NG89) specify that adding pharmacological prophylaxis (like LMWH) to an existing therapeutic dose is unnecessary and significantly increases the **risk of bleeding**. *Stop warfarin and commence therapeutic dose low molecular weight heparin (LMWH)* - While therapeutic LMWH is used for **bridging** perioperatively, it is not the standard long-term prophylaxis for someone already stable and established on warfarin. - Switching unnecessarily to long-term LMWH is more invasive for the patient and does not offer superior protection compared to resume **warfarin therapy**. *Stop warfarin and commence prophylactic dose LMWH until mobile* - Transitioning from therapeutic warfarin to a **prophylactic dose** of LMWH would result in sub-therapeutic anticoagulation levels. - In a patient with a history of **recurrent VTE**, reducing the intensity of anticoagulation increases the risk of a thromboembolic event during the high-risk post-orthopedic period. *Continue warfarin and add prophylactic dose LMWH* - Combining **therapeutic warfarin** (INR 2.0-3.0) with LMWH exceeds the required anticoagulation for VTE prevention. - This combination significantly elevates the risk of **post-operative hematoma** and surgical site bleeding without providing extra clinical benefit. *Stop warfarin, commence direct oral anticoagulant (DOAC) at prophylactic dose* - **DOACs** are effective for VTE prophylaxis, but there is no clinical indication to switch a patient from stable warfarin to a different agent post-surgery. - Prescribing a DOAC at a **prophylactic dose** would provide less protection than the patient’s baseline therapeutic INR, heightening the risk of recurrent clots.
Question 105: A 51-year-old woman with metastatic breast cancer presents with a 3-week history of thoracic back pain and new onset difficulty walking. On examination, she has a sensory level at T8, grade 3/5 power in both legs, and brisk knee and ankle reflexes. Bladder scan shows 400 mL residual volume post-void. She was due to start radiotherapy next week. What is the most appropriate immediate management?
- A. Commence dexamethasone 16 mg daily and arrange radiotherapy within 24 hours
- B. Arrange MRI spine and start dexamethasone after imaging
- C. Contact neurosurgery for urgent decompression and start dexamethasone immediately (Correct Answer)
- D. Start dexamethasone, insert catheter, and arrange routine MRI within 1 week
- E. Arrange emergency CT myelogram and start dexamethasone
Explanation: ***Contact neurosurgery for urgent decompression and start dexamethasone immediately***- The patient exhibits features of **Malignant Spinal Cord Compression (MSCC)**, including thoracic level sensory loss, **motor deficit (3/5 power)**, and urinary retention, which constitutes an **oncological emergency**.- Urgent **surgical decompression** followed by radiotherapy is superior to radiotherapy alone for patients with significant motor deficits, spinal instability, or single-level compression to preserve neurological function.*Commence dexamethasone 16 mg daily and arrange radiotherapy within 24 hours*- While high-dose **dexamethasone** is a standard initial step to reduce vasogenic edema, radiotherapy alone is less effective than surgery for patients already showing **neurological deficits**.- Radiotherapy is generally reserved as primary treatment for highly **radiosensitive tumors** (e.g., lymphomas) or patients who are functionally unfit for surgery.*Arrange MRI spine and start dexamethasone after imaging*- **Dexamethasone** should be administered **immediately** upon clinical suspicion of spinal cord compression to prevent further deterioration, without waiting for imaging results.- Although **MRI whole spine** is the gold standard for diagnosis, the clinical presentation of motor weakness requires parallel surgical consultation rather than serial steps.*Start dexamethasone, insert catheter, and arrange routine MRI within 1 week*- A one-week delay is inappropriate and dangerous; imaging for suspected MSCC must be performed **urgently (within 24 hours)** to avoid irreversible paralysis.- Management of **urinary retention** via catheterization is necessary, but the priority is addressing the **mechanical compression** of the spinal cord.*Arrange emergency CT myelogram and start dexamethasone*- **MRI Whole Spine** is the definitive imaging modality of choice; a **CT myelogram** is only indicated if MRI is contraindicated (e.g., non-compatible pacemakers).- While starting dexamethasone is correct, the management must include a referral for surgical intervention given the **acute neurological decline**.
Question 106: A 68-year-old woman sustains a basicervical neck of femur fracture. Pre-injury she was independently mobile with a walking stick. She has a history of osteoporosis, chronic kidney disease stage 3b (eGFR 38 mL/min/1.73m²), and well-controlled heart failure. Which surgical management option is most appropriate?
- A. Cannulated screw fixation
- B. Dynamic hip screw fixation (Correct Answer)
- C. Uncemented hemiarthroplasty
- D. Cemented total hip replacement
- E. Proximal femoral nail
Explanation: ***Dynamic hip screw fixation*** - **Basicervical neck of femur** fractures occur at the junction of the neck and the trochanter; they are biomechanically equivalent to **extracapsular** fractures and require stable internal fixation. - **Dynamic hip screw (DHS)** is the gold standard for these fractures as it allows controlled collapse and compression across the fracture line while maintaining stability. *Cannulated screw fixation* - These are typically reserved for **undisplaced intracapsular** fractures; they provide insufficient stability for the high-shear forces seen in **basicervical** patterns. - Basicervical fractures have a significantly higher rate of **fixation failure** and non-union when using cannulated screws compared to a DHS. *Uncemented hemiarthroplasty* - Arthroplasty is indicated for **displaced intracapsular** fractures where the blood supply to the femoral head is compromised, which is not the primary concern in **extracapsular/basicervical** fractures. - **Internal fixation** is preferred over joint replacement in this patient to preserve the native bone and avoid the higher surgical trauma of hemiarthroplasty. *Cemented total hip replacement* - While suitable for active patients with displaced intracapsular fractures, it is not the standard of care for **basicervical** fractures where the femoral head blood supply remains intact. - The patient’s **CKD stage 3b** and heart failure increase the risk of **Bone Cement Implantation Syndrome**, making fixation a safer choice than a major cemented arthroplasty. *Proximal femoral nail* - **Intramedullary nails** are generally preferred for unstable, reverse oblique, or high subtrochanteric fractures rather than simple basicervical patterns. - A **DHS** is cheaper and has a lower profile, making it the preferred first-line treatment for stable **extracapsular** patterns over intramedullary nailing.
Question 107: A 43-year-old man with a 6-month history of chronic lower back pain and morning stiffness lasting over 90 minutes presents with new onset right heel pain. He mentions having had three episodes of acute unilateral red eye in the past two years. Examination reveals reduced lumbar spine flexion (Schober's test: 3 cm expansion from 15 cm). Blood tests show CRP 42 mg/L, ESR 38 mm/hr, and he is HLA-B27 positive. What is the most appropriate initial imaging investigation for his back pain?
- A. Plain radiograph of lumbar spine and pelvis
- B. MRI of lumbar spine
- C. CT scan of sacroiliac joints
- D. MRI of sacroiliac joints and spine (Correct Answer)
- E. Bone scintigraphy
Explanation: ***MRI of sacroiliac joints and spine*** - The patient's presentation with chronic inflammatory back pain, morning stiffness >90 minutes, new heel pain (**enthesitis**), recurrent unilateral red eye (**anterior uveitis**), reduced lumbar flexion, elevated inflammatory markers, and **HLA-B27 positivity** are highly suggestive of **axial spondyloarthritis**. - **MRI** is the most sensitive imaging modality for detecting early **sacroiliitis** (bone marrow edema, erosions) and active inflammation in the spine, which is crucial for early diagnosis and appropriate management. *Plain radiograph of lumbar spine and pelvis* - **Plain radiographs** are often normal in the early stages of axial spondyloarthritis and only show changes like **sacroiliitis** or **syndesmophytes** after significant structural damage has occurred, often years into the disease. - Relying solely on X-rays can delay diagnosis and intervention, despite strong clinical suspicion and inflammatory markers. *MRI of lumbar spine* - While an **MRI of the lumbar spine** can show spinal inflammation, it is not the initial imaging of choice because the **sacroiliac joints** are the primary site of involvement and diagnostic hallmark in axial spondyloarthritis. - Missing the sacroiliac joints would fail to fully evaluate the extent of the disease and meet the **ASAS classification criteria** for axial spondyloarthritis. *CT scan of sacroiliac joints* - **CT scans** provide excellent detail of bone structure and are good for identifying **erosions** and **sclerosis** in sacroiliac joints, but they are less sensitive than MRI for detecting early **active inflammation** (bone marrow edema). - Additionally, CT involves **ionizing radiation**, making MRI generally preferred for initial assessment of inflammatory activity. *Bone scintigraphy* - **Bone scintigraphy** can detect areas of increased bone turnover, but it has low **specificity** for diagnosing axial spondyloarthritis, as many conditions can cause increased uptake. - It offers poor anatomical resolution compared to MRI and is rarely used as a primary diagnostic tool for these conditions.
Question 108: A 75-year-old man with an intertrochanteric neck of femur fracture undergoes dynamic hip screw fixation. Post-operatively, which measurement on the anteroposterior hip radiograph best predicts the stability of the fixation and risk of cut-out of the lag screw?
- A. The length of the lag screw penetrating the femoral head
- B. The tip-apex distance (TAD) (Correct Answer)
- C. The angle between the lag screw and the side plate
- D. The number of cortices engaged by the side plate screws
- E. The distance from the lag screw tip to the articular surface
Explanation: ***The tip-apex distance (TAD)*** - **TAD** is the single most important radiographic 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 greater than 25 mm** is significantly associated with mechanical failure and superior-lateral migration of the screw through the femoral head. *The length of the lag screw penetrating the femoral head* - While the screw must be long enough to obtain **adequate purchase** in the subchondral bone, length alone does not account for the **three-dimensional positioning**. - Total length is less predictive of failure than the distance relative to the **center of the femoral head apex**. *The angle between the lag screw and the side plate* - Most dynamic hip screws use a fixed angle (typically **135 or 150 degrees**), which helps restore the femoral neck-shaft angle but does not directly predict **screw cut-out**. - While incorrect angulation can lead to **malalignment**, it is secondary to the precision of the screw tip placement within the head. *The number of cortices engaged by the side plate screws* - Cortical engagement is vital for the **stability of the side plate** to the femoral shaft to prevent plate pull-off. - This measurement does not address the risk of the **lag screw** cutting through the **trabecular bone** of the femoral head. *The distance from the lag screw tip to the articular surface* - Although the screw tip should ideally be within **5-10 mm** of the joint surface, this single-plane measurement is less comprehensive than the **TAD**. - TAD provides a more reliable assessment by combining measurements from both the **anteroposterior and lateral** radiographs.
Question 109: A 57-year-old man with prostate cancer presents with a 4-week history of progressive lower back pain, worse at night. He reports new onset difficulty initiating urination and constipation. On examination, he has tenderness over T12-L1, and lower limb neurology reveals hyperreflexia with bilateral upgoing plantars. Perianal sensation is intact. What is the most likely level of pathology?
- A. Cauda equina compression below L2
- B. Conus medullaris compression at T12-L2 (Correct Answer)
- C. Lumbar nerve root compression at L4-L5
- D. Thoracic spinal cord compression at T10-T11
- E. Sacral nerve compression at S2-S4
Explanation: ***Conus medullaris compression at T12-L2*** - The presence of **hyperreflexia** and **bilateral upgoing plantars** signifies **Upper Motor Neuron (UMN)** involvement, which points to compression of the spinal cord itself. - The **T12-L1 tenderness** along with early **bladder dysfunction** (difficulty initiating urination) and **constipation** are classic symptoms of **Conus Medullaris Syndrome**, as the conus is located between T12 and L2 vertebral levels. *Cauda equina compression below L2* - This condition is characterized by **Lower Motor Neuron (LMN)** signs, including **hyporeflexia** or areflexia, flaccid paralysis, and often **saddle anesthesia** (loss of perianal sensation). - The patient's **hyperreflexia** and **intact perianal sensation** contradict a cauda equina syndrome. *Lumbar nerve root compression at L4-L5* - Compression at this level would primarily cause **radicular pain**, focal weakness, and sensory deficits corresponding to the affected **nerve root**, typically L5. - It would not result in **hyperreflexia**, **upgoing plantars**, or significant early **bladder/bowel dysfunction** like that observed in this patient. *Thoracic spinal cord compression at T10-T11* - While compression in the thoracic spine would produce **UMN signs**, the specific **tenderness at T12-L1** and the pattern of sphincter involvement strongly favor a more caudal spinal cord lesion. - Higher thoracic compression would typically present with a distinct **sensory level** and often more profound motor deficits before significant sphincter symptoms. *Sacral nerve compression at S2-S4* - Isolated sacral nerve compression presents with **LMN signs**, typically causing **flaccid bladder** or bowel dysfunction, and **perianal sensory loss** (saddle anesthesia). - This diagnosis does not account for the **hyperreflexia** and **upgoing plantars**, which indicate **UMN involvement** of the spinal cord.
Question 110: What is the mechanism by which the medial circumflex femoral artery is most commonly injured during a displaced intracapsular neck of femur fracture?
- A. Direct laceration by bone fragments
- B. Thrombosis due to increased intra-articular pressure and capsular tamponade
- C. Spasm secondary to local inflammatory mediators
- D. Compression by haematoma formation
- E. Stretching and tearing due to displacement and rotation (Correct Answer)
Explanation: ***Stretching and tearing due to displacement and rotation*** - In a **displaced intracapsular neck of femur fracture**, the **medial circumflex femoral artery (MCFA)**, particularly its **retinacular branches**, is directly injured by the mechanical forces of fracture displacement and rotation of the femoral head. - This **mechanical disruption**, stretching, and tearing of these critical vessels, which are the primary blood supply to the femoral head, is the leading cause of **avascular necrosis**. *Direct laceration by bone fragments* - While possible, **direct laceration** by sharp bone fragments is less common than the diffuse **stretching and tearing** of the retinacular vessels, which are numerous and delicate. - The primary mechanism of injury involves the disruption of the vessel's integrity as the femoral neck and head fragment move relative to each other, not typically a sharp cut. *Thrombosis due to increased intra-articular pressure and capsular tamponade* - **Increased intra-articular pressure** from **haemarthrosis** and subsequent **capsular tamponade** can compromise microvascular flow and exacerbate ischemia. - However, this is a **secondary effect** that contributes to further ischemia, not the primary mechanism by which the MCFA itself is initially injured during the fracture event. *Spasm secondary to local inflammatory mediators* - **Vascular spasm** can occur in response to trauma and inflammatory mediators, potentially reducing blood flow temporarily. - Nevertheless, spasm is not the primary mechanism causing the **permanent structural damage** to the MCFA and its branches that leads to **avascular necrosis** in these fractures. *Compression by haematoma formation* - A **haematoma** within the joint capsule can indeed compress smaller vessels and contribute to ischemia. - However, the initial and most significant injury to the **medial circumflex femoral artery** in a displaced fracture is typically a direct mechanical **stretching and tearing**, rather than compression from a forming haematoma.
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