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Score — click each question to reveal
Q1
The scaphoid bone is at risk of avascular necrosis after fracture because its blood supply enters:
A. Proximally, from the radial artery
B. Distally, so the proximal fragment loses its supply
C. From both ends equally
D. Through the periosteum only
✓ Answer: B — Blood supply enters distally
The scaphoid receives its blood supply from branches of the radial artery that enter at its distal pole and waist. A fracture at the waist (most common site) cuts off supply to the proximal fragment → avascular necrosis. The proximal pole is at highest risk. Always X-ray in anatomical snuffbox tenderness; if normal, repeat at 2 weeks or MRI/CT.
⚠ The lunate is the most commonly dislocated carpal bone; the scaphoid is the most commonly fractured. Scaphoid fractures can be missed on initial X-ray — treat as fracture until proven otherwise.
Q2
The anatomical snuffbox is bounded anteriorly (radially) by:
A. Extensor pollicis longus tendon
B. Abductor pollicis longus + extensor pollicis brevis tendons
C. Flexor pollicis longus tendon
D. Extensor carpi radialis longus tendon
✓ Answer: B — APL + EPB (anterior/radial boundary)
The anatomical snuffbox: Anterior (radial) boundary = APL + EPB; Posterior (ulnar) boundary = EPL. Floor = scaphoid + trapezium. Contents: radial artery, cephalic vein (origin), superficial radial nerve. Tenderness here = scaphoid fracture until proven otherwise.
⚠ EPL is the POSTERIOR border — remember it wraps around Lister's tubercle. EPB + APL are the ANTERIOR/RADIAL border (two tendons together).
Q3
A Colles' fracture of the distal radius classically produces:
A. Smith's deformity (garden spade)
B. Volar displacement of the distal fragment
C. Dinner-fork deformity (dorsal displacement and tilt)
D. Radial shortening without angulation
✓ Answer: C — Dinner-fork deformity
Colles' fracture: distal radius fracture (within 2 cm of wrist), fragment displaced and tilted dorsally (posteriorly) → dinner-fork deformity on lateral X-ray. Mechanism: FOOSH (fall on outstretched hand), extension force. Commonest in osteoporotic post-menopausal women.
⚠ Smith's fracture (reverse Colles') = volar displacement → “garden spade” deformity. Mechanism = fall on FLEXED wrist. Barton's = intra-articular shear fracture of distal radius.
Q4
In the Garden classification of intracapsular femoral neck fractures, which grade(s) are considered displaced and require prosthetic replacement?
A. Grade I only
B. Grades I and II
C. All four grades
D. Grade III and IV
✓ Answer: D — Garden III and IV (displaced)
Garden classification: I = incomplete/valgus impacted; II = complete, undisplaced; III = complete, partially displaced; IV = complete, fully displaced. Grades III & IV are displaced → blood supply to femoral head disrupted → high AVN risk → treated with hemi/total arthroplasty in elderly. Young patients: attempt ORIF even in Grade III/IV to preserve native head.
⚠ Grades I/II (undisplaced) = cannulated screws (internal fixation). Grades III/IV in elderly = hemiarthroplasty (unipolar/bipolar) or THA. In young, ORIF attempted regardless of displacement.
Q5
The anterior cruciate ligament (ACL) primarily prevents:
A. Anterior displacement of the tibia on the femur
B. Posterior displacement of the tibia on the femur
C. Valgus stress at the knee
D. Hyperextension of the knee
✓ Answer: A — Anterior tibial displacement
ACL: origin = posterior medial surface of lateral femoral condyle; insertion = anterior intercondylar area of tibia. Function: prevents anterior displacement of tibia on femur. Test: anterior drawer test and Lachman test (more sensitive, knee at 20° flexion). PCL prevents posterior tibial displacement (posterior drawer test).
⚠ Mnemonic: ACL prevents Anterior tibial displacement; PCL prevents Posterior tibial displacement. MCL resists valgus stress; LCL resists varus stress.
Q6
O'Donoghue's “Unhappy Triad” of the knee consists of injury to:
A. ACL + PCL + medial meniscus
B. ACL + MCL + medial meniscus
C. ACL + LCL + lateral meniscus
D. PCL + MCL + lateral meniscus
✓ Answer: B — ACL + MCL + medial meniscus
The “Unhappy Triad” (O'Donoghue): ACL + MCL + medial meniscus. Mechanism: valgus force + external rotation (e.g. football tackle from lateral side). The medial meniscus is firmly attached to the MCL, so MCL injury tears the meniscus with it. Modern evidence shows the lateral meniscus may be more commonly injured with ACL tears, but the classic teaching remains medial.
⚠ Why medial meniscus? It is attached to the deep MCL capsule (coronary ligament), making it tethered and vulnerable. The lateral meniscus is more mobile and less often torn with valgus stress.
Q7
The “screw-home mechanism” of the knee locks it in full extension by:
A. Tightening of the PCL in extension
B. Contraction of the popliteus muscle
C. Lateral rotation of the femur on the fixed tibia as the knee reaches full extension
D. Medial rotation of the tibia under the femur
✓ Answer: C — Lateral femoral rotation (or medial tibial rotation) at full extension
At the end of extension, the lateral femoral condyle runs out of articular surface before the medial condyle → the femur rotates laterally on the fixed tibia (or tibia rotates medially) → cruciate ligaments tighten → joint “locked”. Popliteus unlocks the knee (medially rotates the femur on the fixed tibia) to initiate flexion.
⚠ Popliteus = the “key” that unlocks the knee. It medially rotates the femur (or laterally rotates the tibia) to unlock the screwed-home joint at the start of flexion.
Q8
The most common type of shoulder dislocation is:
A. Posterior (associated with seizures and electrocution)
B. Inferior (luxatio erecta)
C. Superior (associated with rotator cuff tear)
D. Anterior (subcoracoid) — ~95% of cases
✓ Answer: D — Anterior (~95%)
Anterior shoulder dislocation (~95%): head of humerus moves anteriorly, commonly to subcoracoid position. Mechanism: abduction + external rotation + extension. Complications: Bankart lesion (tear of anteroinferior labrum), Hill-Sachs lesion (posterior humeral head compression fracture), axillary nerve injury (loss of regimental badge area sensation), recurrence.
⚠ Posterior dislocation = classically “missed” on AP X-ray (vacant glenoid sign); causes = seizures, electrocution, ECT. Patient holds arm in internal rotation and adduction.
Q9
A fracture at the neck of the fibula is most likely to injure which nerve, causing foot drop?
A. Common peroneal (fibular) nerve
B. Tibial nerve
C. Superficial peroneal (fibular) nerve
D. Deep peroneal nerve only
✓ Answer: A — Common peroneal nerve
The common peroneal (fibular) nerve winds around the neck of the fibula, where it is subcutaneous and tightly applied to bone → vulnerable to direct trauma, tight cast, or knee injury. Injury causes foot drop (inability to dorsiflex = deep peroneal), eversion weakness (superficial peroneal), and loss of sensation on dorsum of foot.
⚠ “Common peroneal at the fibular neck” is one of the classic nerve injury sites. The tibial nerve is protected deep in the popliteal fossa. Foot drop = inability to dorsiflex → high-stepping gait.
Q10
The keystone of the medial longitudinal arch of the foot is the:
A. Navicular bone
B. Talus
C. Calcaneus
D. 1st metatarsal head
✓ Answer: B — Talus
The medial longitudinal arch: calcaneus (posterior) → talus (apex/keystone) → navicular → cuneiforms → 1st–3rd metatarsal heads (anterior). The talus is the keystone — it transmits body weight between the leg and foot. Supported by: plantar calcaneonavicular (spring) ligament, tibialis posterior, flexor hallucis longus, plantar fascia.
⚠ Pes planus (flat foot) = failure of the medial longitudinal arch, most commonly due to tibialis posterior dysfunction (adult acquired flat foot). Navicular is part of the arch but not the keystone.
Q11
Acute compartment syndrome requires emergency fasciotomy when compartment pressure rises above:
A. 10 mmHg
B. 20 mmHg
C. 30 mmHg (or within 30 mmHg of diastolic pressure)
D. 50 mmHg
✓ Answer: C — ≥30 mmHg or ΔP <30 mmHg
Absolute threshold: compartment pressure ≥30 mmHg. Relative threshold: ΔP = diastolic BP − compartment pressure <30 mmHg (the more reliable guide). 5 P's: Pain (out of proportion), Pressure, Paraesthesia, Paralysis, Pallor (Pulselessness is late). Treatment: emergency fasciotomy. Most common site: anterior compartment of leg after tibial fracture.
⚠ Do NOT wait for pulselessness — that is a late sign indicating established ischaemia. Fasciotomy must be done before Volkmann's ischaemic contracture (irreversible fibrosis of forearm muscles) occurs.
Q12
The main blood supply to the femoral head in adults comes from the:
A. Lateral circumflex femoral artery
B. Artery of the ligamentum teres (obturator artery)
C. Superior gluteal artery
D. Medial circumflex femoral artery (retinacular branches)
✓ Answer: D — Medial circumflex femoral artery
In adults, ~80% of femoral head blood supply comes from the medial circumflex femoral artery (branch of profunda femoris), which runs in the retinacular folds of the joint capsule. A displaced intracapsular femoral neck fracture tears these retinacular vessels → AVN. The artery of the ligamentum teres (from obturator) is important in children but negligible in adults.
⚠ Children: the artery of the ligamentum teres contributes significantly (Perthes' disease = idiopathic AVN in children). Adults: MCFA is dominant. Extracapsular fractures (intertrochanteric) = lower AVN risk.
Q13
The carrying angle of the elbow is measured between the long axis of the humerus and the forearm in:
A. Full extension, supination
B. Full flexion, supination
C. Full extension, pronation
D. 90° flexion, neutral
✓ Answer: A — Full extension, supination
The carrying angle is measured with the elbow in full extension and supination: ~5–10° in males, ~10–15° in females (valgus). Increased = cubitus valgus (may cause tardy ulnar nerve palsy); decreased/reversed = cubitus varus (“gunstock deformity”, commonest after paediatric supracondylar fracture).
⚠ Cubitus varus = commonest complication of malunited supracondylar fracture in children (not cubitus valgus). Cubitus valgus → tardy ulnar nerve palsy (delayed, years later).
Q14
The pelvic inlet is wider in the transverse diameter in females because the female pelvis has:
A. A narrower subpubic angle (<90°)
B. A wider subpubic angle (>90°), more circular inlet, and greater ischial spine separation
C. A heart-shaped inlet with a prominent sacral promontory
D. An android-shaped pelvis with convergent side walls
✓ Answer: B — Wider subpubic angle, circular inlet, greater ischial spine separation
Female vs male pelvis: female = subpubic angle >90° (gynecoid); pelvic inlet = round/oval (wider transverse); ischial spines less prominent (wider midpelvis); greater sciatic notch wider (>90°); sacrum shorter, wider, less curved. Male = subpubic angle <90°; inlet heart-shaped; narrow midpelvis.
⚠ Caldwell-Moloy classification: gynecoid (round, F), android (heart-shaped, M), anthropoid (oval AP diameter longest), platypelloid (flat, wide transverse). Gynecoid = best for childbirth.
Q15
The acromioclavicular (AC) joint is primarily stabilised against superior displacement by the:
A. AC ligament alone
B. Coracoacromial ligament
C. Coracoclavicular (CC) ligament (conoid + trapezoid)
D. Deltoid and trapezius muscles
✓ Answer: C — Coracoclavicular ligament
The coracoclavicular ligament (conoid + trapezoid) is the primary stabiliser of the AC joint against vertical (superior) displacement. AC ligament stabilises against horizontal (anteroposterior) displacement. Rockwood Grade I/II: AC ± CC intact; Grade III: both disrupted (clinical controversy: surgical vs conservative); Grades IV–VI: severe, operative.
⚠ Coracoacromial ligament forms the coracoacromial arch and limits superior humeral head migration — it is not an AC joint stabiliser.
Q16
Which carpal bone is most commonly DISLOCATED (rather than fractured)?
A. Scaphoid
B. Trapezium
C. Hamate
D. Lunate
✓ Answer: D — Lunate
The lunate is the most commonly dislocated carpal bone (perilunate → lunate dislocation sequence). It can compress the median nerve in the carpal tunnel → acute carpal tunnel syndrome. On lateral X-ray the lunate tilts anteriorly (“spilled teacup” sign). The scaphoid is the most commonly fractured carpal bone.
⚠ Hook of hamate fracture = cyclist/golfer (direct blow) + ulnar nerve/artery damage. Trapezium fracture = dorsal ridge (rare). Pisiform fracture = direct blow.
Q17
The hip joint is a synovial joint of which type, and its deepest bony landmark palpable from behind is:
A. Ball and socket joint; greater trochanter
B. Condyloid joint; greater trochanter
C. Ball and socket joint; ischial tuberosity
D. Saddle joint; lesser trochanter
✓ Answer: A — Ball and socket; greater trochanter
The hip is a ball and socket (spheroidal) synovial joint: femoral head (ball) in acetabulum (socket). The greater trochanter is the most prominent bony landmark felt laterally. Bryant's triangle and Nélaton's line are used to assess displacement in femoral neck fractures using the greater trochanter as reference.
⚠ The hip has much more bony stability than the shoulder (deep acetabular socket + labrum). The shoulder is shallower → more mobile but less stable. The lesser trochanter is medial/posterior and not easily palpable from the surface.
Q18
A supracondylar fracture of the humerus in a child is most commonly associated with injury to:
A. Radial nerve (wrist drop)
B. Anterior interosseous nerve (branch of median nerve — inability to make “OK” sign)
C. Ulnar nerve
D. Musculocutaneous nerve
✓ Answer: B — Anterior interosseous nerve (median nerve branch)
Supracondylar fracture in children (FOOSH, extension type): the displaced proximal fragment can injure the anterior interosseous nerve (deep branch of median nerve) → inability to flex the distal IP of index finger and IP of thumb → cannot make the “OK” sign; pinch deformity. Also: brachial artery can be injured → Volkmann's ischaemic contracture.
⚠ Radial nerve is at risk in humeral shaft fractures (Holstein-Lewis = spiral fracture at junction of middle/lower thirds). Ulnar nerve at risk in medial epicondyle fractures and cubitus valgus. AIN = purely motor (no sensory loss).
Q19
Normal ankle dorsiflexion is ~20°. This movement occurs primarily at which joint?
A. Subtalar (talocalcaneal) joint
B. Talonavicular joint
C. Talocrural (tibiotalar) joint
D. Calcaneocuboid joint
✓ Answer: C — Talocrural (ankle) joint
The talocrural (ankle) joint: synovial hinge between the distal tibia/fibula mortise and the trochlea of the talus. Movements: dorsiflexion (20°) and plantarflexion (50°). The mortise is most stable in dorsiflexion (trochlea is wider anteriorly → wedged into mortise). Inversion/eversion occur at the subtalar (talocalcaneal) joint.
⚠ Ankle sprains: most common = inversion injury → tears ATFL (anterior talofibular ligament) first, then CFL, then PTFL. Ottawa Ankle Rules: X-ray if bony tenderness at posterior tibia/fibula or inability to bear weight.
Q20
The suprascapular notch is crossed by:
A. Suprascapular nerve above; suprascapular artery below the ligament
B. Both nerve and artery below the ligament
C. Both nerve and artery above the ligament
D. Suprascapular artery above; suprascapular nerve below the transverse scapular ligament
✓ Answer: D — Artery above, nerve below the ligament
The superior transverse scapular ligament converts the suprascapular notch into a foramen. The suprascapular nerve passes through (below) the ligament; the suprascapular artery crosses above it. Mnemonic: “Army under the bridge, Navy over it” (Nerve = Army = under; Artery = above). Entrapment of the nerve → supraspinatus + infraspinatus weakness and wasting.
⚠ This is a classic MCQ trap. Nerve → through the notch (under the ligament). Artery → over the ligament. Apply the “Army under the bridge” mnemonic reliably.
D1Anatomical Snuffbox+
A triangular depression on the lateral (radial) aspect of the wrist, visible when the thumb is extended. Boundaries: anterior (radial) = tendons of APL + EPB; posterior (ulnar) = tendon of EPL; floor = scaphoid + trapezium + radial styloid; roof = superficial radial nerve + cephalic vein. Contents running through it: radial artery (main occupant). Tenderness = scaphoid fracture until proven otherwise.
Gray's Anatomy 4e · Unit 03
D2Carrying Angle of the Elbow+
The valgus angle formed between the long axis of the humerus and the long axis of the forearm when the elbow is in full extension and supination. Normal values: ~5–10° in males, ~10–15° in females. Increased = cubitus valgus (may cause tardy ulnar nerve palsy). Decreased/reversed = cubitus varus (gunstock deformity, commonest complication of malunited supracondylar fracture in children). Due to the oblique orientation of the trochlea and the non-right-angle of the medial/lateral epicondyles.
Gray's Anatomy 4e · Unit 03
D3Unhappy Triad (O'Donoghue's Triad)+
A combination of three simultaneous knee ligament/meniscal injuries: ACL + MCL + medial meniscus. Mechanism: valgus force combined with external rotation of the tibia (e.g. lateral tackle in football). The medial meniscus is co-injured because it is firmly attached to the deep surface of the MCL (coronary ligament). Classic features: immediate haemarthrosis, gross instability, severe pain. Note: current literature suggests the lateral meniscus is more commonly injured with ACL tears, but the classic exam answer remains medial.
Gray's Anatomy 4e · Unit 03
D4Colles' Fracture+
An extra-articular fracture of the distal radius within 2 cm of the wrist, with the distal fragment displaced and angulated dorsally (posteriorly). Produces a dinner-fork deformity on lateral X-ray view. There is also radial displacement, radial tilt, impaction, and often ulnar styloid fracture. Mechanism: FOOSH (fall on outstretched hand) in extension. Commonest in post-menopausal women with osteoporosis. Complications: malunion, EPL rupture (bowstringing), median nerve compression, radiocarpal arthritis.
Gray's Anatomy 4e · Unit 03
D5Anatomical Neck vs Surgical Neck of Humerus+
Anatomical neck: the constriction immediately below the humeral head, marking the attachment of the joint capsule. It lies between the articular surface and the greater/lesser tubercles. Fractures here are rare but cause AVN of the humeral head (capsular vessels disrupted). Surgical neck: the constricted area just below the tubercles (greater and lesser), at the junction of the upper shaft and head. Most commonly fractured humeral site. The axillary nerve and posterior circumflex humeral artery are at risk — damage causes deltoid wasting + loss of sensation over “regimental badge” area.
Gray's Anatomy 4e · Unit 03
D6Garden Classification of Femoral Neck Fractures+
A four-grade classification of intracapsular femoral neck fractures based on displacement: Grade I: incomplete (valgus impacted, trabecular pattern intact); Grade II: complete, undisplaced (abnormal trabeculae alignment but no displacement); Grade III: complete, partial displacement (femoral head rotates); Grade IV: complete, full displacement (femoral head free-floating in acetabulum, trabeculae align due to complete capsular disruption). Grades I/II = undisplaced → ORIF with cannulated screws. Grades III/IV = displaced → hemiarthroplasty (elderly) or ORIF (young). AVN and non-union are the major complications.
Gray's Anatomy 4e · Unit 03
Essay 1
Describe the carpal tunnel: its walls, contents, and the clinical features, investigations, and management of carpal tunnel syndrome.
8 marks
Walls of the carpal tunnel
The carpal tunnel is an osseofibrous canal at the wrist: Floor and sides = the carpal bones (arranged in a concave arch); Roof = flexor retinaculum (transverse carpal ligament), which spans from scaphoid tubercle + trapezium ridge (lateral) to pisiform + hook of hamate (medial).
Contents (9 tendons + 1 nerve)
- 4 FDS tendons (index/middle superficial to ring/little)
- 4 FDP tendons
- 1 FPL tendon (in its own synovial sheath)
- Median nerve (most superficial and lateral → most compressed)
Not in the tunnel: FCR (in its own groove), palmaris longus (superficial to retinaculum), ulnar nerve (in Guyon's canal, medial to tunnel).
Carpal tunnel syndrome (CTS) — features
- Tingling/numbness in median nerve distribution: radial 3½ digits (thumb, index, middle, radial half of ring)
- Nocturnal symptoms (worse at night, relieved by shaking hand — “flick sign”)
- Thenar muscle wasting (LOAF muscles — recurrent branch of median nerve)
- Weak pinch grip
- Causes: idiopathic (most common), pregnancy, hypothyroidism, RA, acromegaly, DM, amyloidosis
Clinical tests
- Tinel's sign: tapping over the carpal tunnel → tingling in median nerve distribution
- Phalen's test: sustained wrist flexion 60 sec → symptoms reproduced (more sensitive)
Investigations & management
- Nerve conduction studies: confirm delayed distal sensory/motor latency
- Conservative: wrist splint (neutral), treat underlying cause
- Surgical: carpal tunnel decompression (division of flexor retinaculum) — definitive if thenar wasting or failed conservative
Marking (8 marks): Walls + flexor retinaculum attachment (1.5) · Contents: correct list of tendons + median nerve (2) · Symptoms and nerve distribution (1.5) · Thenar wasting (1) · Clinical tests named (1) · Management (1)
Essay 2
Describe the shoulder (glenohumeral) joint: type, articular surfaces, capsule and reinforcing structures, movements and muscles, and complications of anterior dislocation.
8 marks
Type & articular surfaces
Ball and socket (spheroidal) synovial joint. Head of humerus (large, spherical) articulates with the shallow glenoid fossa of the scapula, which is deepened by the fibrocartilaginous glenoid labrum.
Capsule and stabilising structures
- Fibrous capsule: attached to glenoid labrum + anatomical neck of humerus; lax inferiorly (allows ROM)
- Glenohumeral ligaments (superior, middle, inferior GHL) — thickenings of capsule
- Transverse humeral ligament: holds biceps long head tendon in bicipital groove
- Rotator cuff: SITS — supraspinatus, infraspinatus, teres minor, subscapularis. Dynamic stabilisers; compress humeral head into glenoid
- Coracoacromial arch: coracoid + coracoacromial lig + acromion; limits superior migration
Movements and primary muscles
- Flexion: anterior deltoid, pectoralis major (clavicular)
- Extension: posterior deltoid, latissimus dorsi
- Abduction: supraspinatus (0–15°) + middle deltoid (15–90°) + scapular rotation (90–180°)
- Medial rotation: subscapularis, pectoralis major, latissimus dorsi
- Lateral rotation: infraspinatus, teres minor
Anterior dislocation complications
- Bankart lesion: avulsion of anteroinferior glenoid labrum → recurrence
- Hill-Sachs lesion: compression fracture of posterolateral humeral head
- Axillary nerve injury: deltoid paralysis + regimental badge area sensory loss
- Recurrence: 90% if <20 years old at first dislocation
Marking (8 marks): Type + articular surfaces + labrum (1.5) · Capsule and GHL (1) · Rotator cuff: all 4 named (1.5) · Movements with muscles (2) · Bankart + Hill-Sachs + axillary nerve (2)
Essay 3
Describe the knee joint: type, articular surfaces, cruciate ligaments (origin, insertion, function), and the role of the menisci. Name the tests for cruciate ligament integrity.
8 marks
Type & articular surfaces
The largest synovial joint in the body. Modified hinge (condylar) joint. Articulations: (1) medial femoral condyle + medial tibial plateau; (2) lateral femoral condyle + lateral tibial plateau; (3) patella + patellar surface of femur (patellofemoral joint).
Cruciate ligaments
- ACL: Origin = posterior medial surface of lateral femoral condyle; Insertion = anterior intercondylar area of tibia. Function: prevents anterior tibial displacement; taut in extension. Tests: Anterior drawer (90° flexion), Lachman test (20° flexion — more sensitive), Pivot-shift test.
- PCL: Origin = anterior medial surface of medial femoral condyle; Insertion = posterior intercondylar area of tibia. Function: prevents posterior tibial displacement (main stabiliser in flexion). Test: Posterior drawer test, posterior sag sign.
Menisci
- Fibrocartilaginous C-shaped discs. Medial = C-shaped, attached to MCL (immobile). Lateral = O-shaped, not attached to LCL (more mobile).
- Functions: deepen tibial surface, improve congruence, transmit 50–70% of knee load, proprioception, lubrication
- Blood supply: peripheral 30% (red zone, heals); inner 70% (white zone, avascular, cannot heal → resection)
- Medial meniscus torn in Unhappy Triad; bucket-handle tear = locked knee
Marking (8 marks): Type + 3 articulations (1.5) · ACL origin/insertion/function/tests (2) · PCL origin/insertion/function/test (2) · Menisci: shape + MCL attachment + functions (2) · Bucket-handle + locked knee (0.5)
Essay 4
Describe the blood supply to the femoral head and the classification of femoral neck fractures. Explain why displaced intracapsular fractures cause avascular necrosis.
6 marks
Blood supply to the femoral head
- Medial circumflex femoral artery (MCFA, from profunda femoris): provides ~80% of femoral head blood supply via retinacular vessels in the hip joint capsule. Most important in adults.
- Lateral circumflex femoral artery (LCFA): minor contribution
- Artery of the ligamentum teres (from obturator artery): significant in children under ~8 years; negligible in adults
Why displaced fractures cause AVN
Intracapsular fractures disrupt the retinacular blood vessels that run in the synovial folds of the capsule from the femoral neck to the head. Displacement tears these vessels → the femoral head loses its only significant blood supply in adults → avascular necrosis over months. Extracapsular fractures (intertrochanteric, subtrochanteric) do not disrupt these vessels → much lower AVN rate.
Garden classification
Grade I: incomplete/impacted valgus; Grade II: complete, undisplaced; Grade III: complete, partial displacement; Grade IV: complete, full displacement. Grades I–II = low AVN risk → fixation. Grades III–IV = high AVN risk → arthroplasty in elderly.
Marking (6 marks): MCFA as dominant vessel (1.5) · Retinacular vessels in capsule (1) · Mechanism of AVN in displaced fractures (1.5) · Garden I–IV described (1.5) · Treatment principle (0.5)
Essay 5
Describe the arches of the foot: name the three arches, identify the keystone of each, name the structures that support them, and describe the clinical consequence of arch failure.
6 marks
Three arches
- Medial longitudinal arch: tallest and most important. Calcaneus → talus (keystone) → navicular → three cuneiforms → 1st–3rd metatarsal heads. Support: plantar calcaneonavicular (spring) ligament (primary passive), tibialis posterior (active), flexor hallucis longus, plantar fascia.
- Lateral longitudinal arch: lower, flatter. Calcaneus → cuboid (keystone) → 4th–5th metatarsal heads. Support: long and short plantar ligaments, peroneus longus.
- Transverse arch: at the level of the metatarsal bases/cuneiforms. Middle cuneiform (keystone). Support: peroneus longus (main), tibialis posterior, deep transverse metatarsal ligament.
Clinical consequences of arch failure
- Pes planus (flat foot): medial longitudinal arch collapses, usually due to tibialis posterior dysfunction (adult acquired flat foot, progressive).
- Plantar fasciitis: overuse + arch strain → pain at calcaneal attachment of plantar fascia, worst with first steps in the morning.
- Pes cavus (high arch): associated with neurological conditions (Charcot-Marie-Tooth, Friedreich's ataxia) → clawing of toes, painful metatarsal heads.
Marking (6 marks): All three arches named (1) · Keystones: talus + cuboid + middle cuneiform (1.5) · Spring ligament + tibialis posterior for medial arch (1) · Peroneus longus for transverse arch (0.5) · Pes planus + tibialis posterior dysfunction (1) · Plantar fasciitis (1)