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Clinical Case 3 - Right Tibia & Fibula Fracture

Scenario: After plaster cast removal for right tibia and fibula fracture, the patient has lost sensation on the dorsum of the foot (including toes) except the lateral side of the little toe. Dorsiflexion and eversion of the foot are also lost.

Q1. Structure Involved

The Common Peroneal Nerve (CPN) - specifically its branch the Superficial Peroneal Nerve is primarily responsible here, but the pattern of combined motor loss (dorsiflexion + eversion) and sensory loss strongly suggests injury to the Common Peroneal Nerve (L4, L5, S1, S2) as a whole, which then affects both its terminal branches:

Deep Peroneal Nerve - dorsiflexion of the foot
Superficial Peroneal Nerve - eversion of the foot + sensation over dorsum of foot

The spared area (lateral side of the little toe) is supplied by the Sural Nerve - which is why sensation there is preserved.

The common peroneal nerve is the lateral division of the sciatic nerve. It winds around the neck of the fibula, making it extremely vulnerable to compression during prolonged casting - this is a well-recognised complication of plaster immobilisation.

Q2. Surface Marking of the Common Peroneal Nerve

The common peroneal nerve can be marked as follows:

It begins at the apex of the popliteal fossa (where it separates from the sciatic nerve)
It runs along the medial border of the biceps femoris tendon, obliquely downward and laterally toward the head of the fibula
It then winds around the neck of the fibula (just below the fibular head), where it is subcutaneous and directly palpable
At the neck of the fibula, it divides into the deep peroneal nerve (anterior compartment) and superficial peroneal nerve (lateral compartment)

The critical surface landmark: a line from the apex of the popliteal fossa to the neck of the fibula, following the posterior border of the fibula head.

Q3. Deformity Due to Injury

Foot Drop (Drop Foot)

When the common peroneal nerve is injured:

Dorsiflexors (tibialis anterior, extensor hallucis longus, extensor digitorum longus) are paralysed - loss of dorsiflexion
Evertors (peroneus longus, peroneus brevis) are paralysed - loss of eversion
Unopposed action of the tibialis posterior (plantar flexion + inversion) leads to:
- The foot hangs in plantar flexion and inversion = "foot drop" with a degree of inversion
- The deformity is sometimes called talipes equinovarus (fixed foot drop)
The patient develops a characteristic high-stepping (steppage) gait to avoid dragging the dropped foot

Clinical Case 4 - Bullet Injury to Right Gluteal Region

Scenario: Bullet injury to right gluteal region. After recovery - characteristic limp during walking, sagging of left hip when stepping on the right foot. Trendelenburg sign positive.

Q1. Nerve Involved

Superior Gluteal Nerve (L4, L5, S1)

The superior gluteal nerve exits the pelvis through the greater sciatic foramen, superior to the piriformis muscle. A bullet wound to the gluteal region can directly injure this nerve. Injury causes weakness of the hip abductor muscles, which leads to the positive Trendelenburg sign and Trendelenburg gait described. - Gray's Anatomy for Students, Imaging Anatomy Vol. 3

Q2. Muscles Supplied by the Superior Gluteal Nerve

The superior gluteal nerve supplies:

Gluteus medius - primary hip abductor; also assists medial rotation
Gluteus minimus - hip abductor and medial rotator
Tensor fasciae latae (TFL) - flexes, abducts and medially rotates the thigh; tenses the iliotibial tract

All three muscles are hip abductors/stabilisers of the pelvis. - Miller's Review of Orthopaedics 9th Edition; Imaging Anatomy Vol. 3

Q3. Trendelenburg Sign

Definition: A test for weakness of the hip abductor muscles (gluteus medius and minimus).

Procedure: Ask the patient to stand on the affected limb (right limb in this case).

Positive sign: When the patient stands on the affected right limb, the pelvis drops/sags on the opposite (left) side - because the weakened right-side abductors cannot hold the pelvis level.

Mechanism:

Normally, when standing on one leg, the abductors of the weight-bearing side contract to keep the pelvis horizontal
When the superior gluteal nerve is damaged, gluteus medius and minimus are paralysed on that side
The pelvis tilts inferiorly toward the swing (non-weight-bearing) side - visible as "sagging of the left hip"

Trendelenburg Gait: The patient compensates by lurching the trunk toward the affected (right) side during the stance phase - this is also called a "gluteus medius lurch" or "abductor lurch." - Gray's Anatomy for Students

Clinical Case 5 - DVT After Hysterectomy

Scenario: 42-year-old woman, post-hysterectomy, presents with swollen, tender, warm left calf - diagnosed as Deep Vein Thrombosis (DVT).

Q1. Deep Veins of the Lower Limb

Listed from distal to proximal (Bailey & Love's Surgery 28th Edition; Harrison's 22nd Edition):

In the foot/leg:

Anterior tibial veins (paired venae comitantes of the anterior tibial artery)
Posterior tibial veins (paired venae comitantes of the posterior tibial artery)
Peroneal (fibular) veins (paired venae comitantes of the peroneal artery)
Soleal veins (drain into posterior tibial or peroneal veins)
Gastrocnemius veins (medial and lateral, drain into popliteal vein)
Sural veins

In the popliteal fossa:

Popliteal vein (formed by union of anterior + posterior tibial veins, plus fibular veins)

In the thigh:

Femoral vein (continuation of popliteal vein above adductor hiatus)
Deep femoral vein (profunda femoris vein, joins femoral vein in the femoral triangle)

In the pelvis:

External iliac vein (continuation of femoral vein above inguinal ligament)
Internal iliac vein
Common iliac vein

Q2. Peripheral Heart

The "peripheral heart" refers to the calf muscle pump (the soleus and gastrocnemius muscles acting together).

During walking and muscle contraction, the calf muscles compress the deep veins of the leg, propelling blood proximally against gravity. The venous valves prevent backflow. This mechanism is so effective at pushing blood from the lower limb back toward the heart that the calf muscle complex is colloquially called the "peripheral heart."

Clinical relevance here: Post-operative immobility after hysterectomy means the calf muscle pump is not functioning - venous stasis results, which is one component of Virchow's Triad contributing to DVT formation.

Q3. Veins Connecting Superficial and Deep Veins of the Leg

These are the Perforating (Fascial Perforator) Veins, also called communicating veins:

They penetrate the deep fascia of the leg to connect the superficial venous system (great saphenous vein, small saphenous vein) to the deep venous system
They contain valves that normally direct blood flow from superficial to deep (i.e., inward)
The most clinically important are the medial calf perforators (Cockett's perforators / Paratibial perforators), located along the medial aspect of the leg

Named groups include:

Cockett's perforators (posterior tibial perforators) - 3 main ones at the lower medial leg
Boyd's perforator - around the knee
Dodd's perforator - in the lower thigh
Hunter's perforator - in the middle thigh

When deep vein valves are destroyed post-DVT, these perforators may become incompetent, leading to ambulatory venous hypertension and venous ulcers. - Bailey and Love's Surgery 28th Edition; Mulholland and Greenfield's Surgery 7th Edition

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Clinical Case 1 - Right Clavicle Fracture (RTA)

Scenario: 27-year-old male, RTA, severe pain over right collar bone. Prominence/ecchymosis over right midclavicular region, diffuse swelling over right clavicle/shoulder/arm, depression of right shoulder joint, mild numbness over right upper limb, right radial pulse weaker than left.

Q1. Most Likely Injury

Fracture of the right clavicle - specifically a midshaft (middle third) fracture, which is the most common type (accounts for ~80% of all clavicle fractures).

Classic clinical signs present here:

Prominence and ecchymosis at the midclavicular point
Patient holding the arm adducted across the body (to relieve pain and weight of the limb)
Depression of shoulder (loss of the clavicle's strut function - it normally holds the shoulder up and out)
Weaker radial pulse = possible subclavian artery compression/injury by bone fragments
Numbness = brachial plexus involvement

Q2. Structures Most Commonly Affected Following Clavicle Fracture

The clavicle lies directly above critical neurovascular structures. Commonly affected structures include:

Brachial plexus - lies posterior and inferior to the clavicle; stretch or compression by displaced fragments causes numbness/paraesthesia over the upper limb
Subclavian artery and vein - lie immediately beneath the clavicle; injury can cause diminished radial pulse, thrombosis, or pseudoaneurysm
Axillary artery - can be involved with severely displaced fractures
Lung apex / Pleura - pneumothorax or haemothorax with severely comminuted fractures (though less common)
Thoracic duct (on the left side)

The brachial plexus and subclavian vessels explain ALL the neurovascular signs in this patient - numbness (plexus) and weak radial pulse (artery). - Rockwood & Green's Fractures in Adults 10th Ed; Textbook of Family Medicine 9e

Q3. Joints Formed by the Clavicle

The clavicle forms two joints:

Sternoclavicular (SC) joint - medially, between the sternal end of the clavicle and the manubrium sterni (+ 1st costal cartilage). It is the only bony articulation between the upper limb and the axial skeleton. It is a synovial saddle (sellar) joint with an articular disc.
Acromioclavicular (AC) joint - laterally, between the acromial end of the clavicle and the acromion of the scapula. It is a synovial plane joint. Stabilised by the coracoclavicular ligaments (conoid + trapezoid).

Rosen's Emergency Medicine; Imaging Anatomy Vol. 3

Clinical Case 2 - Breast Lump with Peau d'Orange

Scenario: 47-year-old female, hard painless lump in upper outer quadrant of right breast. Peau d'orange skin appearance, loss of mobility of breast and nipple retraction, enlarged axillary lymph nodes.

Q1. Most Likely Observation / Diagnosis

Carcinoma of the Breast (Breast Cancer)

The combination of:

Hard painless lump in the upper outer quadrant (most common site - 50% of tumours arise here)
Peau d'orange
Nipple retraction
Loss of mobility (fixation to deep structures)
Enlarged axillary lymph nodes

...is the classic presentation of invasive breast carcinoma. - Bailey and Love's Surgery 28th Ed; Robbins Pathology

Q2. Common Site of Breast Cancer

The upper outer quadrant (superolateral quadrant) of the breast is the most common site (~50% of all breast cancers arise here). This is because it contains the greatest volume of breast tissue (the axillary tail of Spence extends into this region, and most terminal duct lobular units - TDLUs - lie here).

Q3. Muscles Lying Deep to the Breast

The breast sits on two muscles:

Pectoralis major - covers the medial 2/3 of the deep surface of the breast
Serratus anterior - covers the lateral 1/3
(A small portion may overlie the external oblique inferolaterally)

Loss of mobility of the breast in this patient indicates that the tumour has invaded through the retromammary space and fixed itself to the pectoralis fascia or pectoralis major muscle - a sign of locally advanced disease.

Q4. Lymphatic Drainage of Breast / Anatomical Basis of Peau d'Orange

Lymphatic drainage of the breast:

~75% drains to axillary lymph nodes, divided into levels:
- Level I (anterior/pectoral group, lateral thoracic nodes) - below and lateral to pectoralis minor
- Level II (central group, interpectoral/Rotter's nodes) - behind pectoralis minor
- Level III (apical/subclavian nodes) - above and medial to pectoralis minor, at apex of axilla
~25% drains to internal mammary (parasternal) nodes - along internal mammary vessels, deep to the parietal pleura
Small amounts drain to: supraclavicular nodes, contralateral breast, abdominal nodes

Anatomical basis of Peau d'Orange:

The skin of the breast contains a rich network of cutaneous lymphatics. These cutaneous lymphatics communicate with deeper channels through the breast parenchyma. When axillary lymph nodes are blocked by metastatic tumour cells, lymphatic obstruction causes:

Lymphoedema of the skin and subcutaneous tissues
The skin becomes thickened and oedematous
Hair follicles and sweat gland openings are tethered to the deeper dermis by Cooper's ligaments (which cannot expand), while the surrounding skin swells
This creates the classic "orange peel" appearance - pitting around the fixed follicle openings
Bailey and Love's Surgery 28th Ed; Schwartz's Principles of Surgery 11th Ed

Clinical Case 3 - Brachial Plexus Injury (Motorcyclist RTA)

Scenario: Motorcyclist, right brachial plexus injury. Weakness of right shoulder abduction and forearm flexion. Weakness of lateral aspect of upper arm. Biceps and brachioradialis reflexes absent. Some sensory loss over lateral aspect of upper arm.

Q1. Most Likely Injury

Erb-Duchenne Palsy - injury to the Upper Trunk of the Brachial Plexus (C5 and C6 roots)

In motorcycle accidents, the typical mechanism is forced separation of the head/neck from the shoulder (e.g., when thrown off the bike), which violently stretches the C5-C6 roots/upper trunk. This is the classic adult Erb's palsy mechanism. - Neuroanatomy through Clinical Cases 3rd Ed; Bradley and Daroff's Neurology

Q2. Muscles Affected Following Upper Trunk (C5-C6) Injury

The muscles affected are those supplied by C5 and C6:

Muscle	Action Lost
Deltoid (axillary n., C5)	Shoulder abduction
Supraspinatus (suprascapular n., C5)	Initiates shoulder abduction
Infraspinatus (suprascapular n., C5-C6)	Lateral rotation of shoulder
Teres minor (axillary n., C5)	Lateral rotation
Biceps brachii (musculocutaneous n., C5-C6)	Forearm flexion + supination
Brachialis (musculocutaneous n., C5-C6)	Forearm flexion
Brachioradialis (radial n., C5-C6)	Forearm flexion in mid-prone position

The classic posture is the "waiter's tip" position: arm adducted and medially rotated, elbow extended, forearm pronated - because the opposing movements (abduction, lateral rotation, elbow flexion, supination) are all lost.

Q3. Root Value of the Injury

The roots involved are C5 and C6 (upper trunk of the brachial plexus).

Clues in the clinical presentation:

Biceps reflex absent → C5, C6
Brachioradialis reflex absent → C5, C6
Sensory loss over the lateral arm → territory of the upper lateral cutaneous nerve of arm (from axillary nerve, C5) and lateral cutaneous nerve of forearm (from musculocutaneous nerve, C5-C6)

Clinical Case 4 - Radial Nerve Injury / Wrist Drop

Scenario: 25-year-old male, trauma, unable to extend the wrist. Digits flexed at proximal phalanges. Supination affected. Extension of elbow and extension of middle/terminal phalanges spared. Sensory loss from lower lateral arm and posterior forearm. No sensory loss from posterior arm. X-ray - fracture diagnosed.

Q1. Anatomical Structure Involved and Site of Lesion

Structure: Radial nerve

Site of lesion: In the spiral groove (radial groove) of the humerus - i.e., at the mid-shaft level of the humerus. This is a fracture of the shaft of the humerus.

Key reasoning:

Wrist drop (lost wrist extension) + lost finger extension at MCP joints = posterior interosseous nerve (deep branch of radial) territory - lost
Supination weakened (brachioradialis affected, but elbow extension spared = triceps intact)
Elbow extension IS spared - this rules out a high axillary or posterior cord lesion (triceps is supplied by radial nerve branches given off in the axilla, above the spiral groove)
Terminal phalanges extension IS spared - intrinsic muscles extending IPs are supplied by ulnar and median nerves
Sensory loss from lower lateral arm (lower lateral cutaneous nerve of arm, from radial nerve at spiral groove level) and posterior forearm (posterior cutaneous nerve of forearm, also from radial nerve in spiral groove)
No loss from posterior arm - posterior cutaneous nerve of arm is given off above the spiral groove, so its preservation confirms the lesion is at or below the spiral groove

Q2. Course and Branches of the Radial Nerve

Course:

Arises from the posterior cord of the brachial plexus (C5-C8, T1)
Passes through the triangular interval (between long head of triceps, humerus, teres major) to enter the posterior compartment of arm
Winds around the spiral groove (radial groove) of the humerus with the profunda brachii artery, between medial and lateral heads of triceps
Pierces the lateral intermuscular septum to enter the anterior compartment of arm
Lies between brachialis and brachioradialis in the lateral cubital fossa
Divides into two terminal branches at the level of the lateral epicondyle:
- Superficial branch (purely sensory) - runs under brachioradialis, emerges posteriorly at the wrist, supplies dorsum of hand (lateral 3.5 fingers)
- Deep branch (posterior interosseous nerve) - winds around the neck of the radius through the supinator muscle (arcade of Frohse), enters posterior compartment, supplies all extensors of wrist, fingers, and thumb

Branches:

Nerve to long head of triceps (in axilla)
Nerve to medial head of triceps + lower lateral cutaneous nerve of arm
Posterior cutaneous nerve of arm (in axilla)
Nerve to lateral and medial heads of triceps (in spiral groove)
Posterior cutaneous nerve of forearm (in spiral groove)
Lower lateral cutaneous nerve of arm
Nerve to brachioradialis, ECRL, ECRB, and anconeus (in anterior arm/lateral cubital fossa)
Superficial radial nerve (sensory terminal branch)
Posterior interosseous nerve (deep/motor terminal branch)

Q3. Anatomical Basis for Signs and Symptoms

Sign/Symptom	Anatomical Basis
Wrist drop	Loss of wrist extensors (ECRL, ECRB, ECU) supplied by the radial nerve / posterior interosseous nerve
Finger drop (flexion at MCP joints)	Loss of extensor digitorum communis (posterior interosseous nerve) - cannot extend fingers at MCPs
Middle and terminal phalangeal extension SPARED	Extension at IPJs is performed by lumbricals and interossei (ulnar + median nerves) via the extensor hood - unaffected
Supination affected	Supinator muscle supplied by posterior interosseous nerve; brachioradialis (a weak supinator from mid-prone position) also loses radial nerve supply at spiral groove
Elbow extension SPARED	Triceps is supplied by radial nerve branches given off above the spiral groove (in the axilla) - so these are preserved
Sensory loss lower lateral arm + posterior forearm	Lower lateral cutaneous nerve of arm and posterior cutaneous nerve of forearm both arise at the spiral groove level and are affected
No sensory loss from posterior arm	Posterior cutaneous nerve of arm arises in the axilla (above the groove) and is preserved, confirming the exact level of injury

Clinical Case 5 - Carpal Tunnel Syndrome

Scenario: 33-year-old female, severe pain in right wrist and hand, weak right hand. Numbness, paraesthesia, and pain along the lateral palm and lateral 3.5 fingers. Mild thenar muscle atrophy. Weak grip.

Q1. Most Likely Injury

Carpal Tunnel Syndrome (CTS)

The classic presentation: pain/numbness/paraesthesia in the distribution of the median nerve (lateral 3.5 fingers and lateral palm), thenar wasting, and weak grip. It is the most common entrapment neuropathy. - Gray's Anatomy for Students

Q2. Structure Involved

Median Nerve, compressed within the Carpal Tunnel (beneath the flexor retinaculum at the wrist).

The median nerve supplies:

Sensation to the lateral 3.5 fingers (thumb, index, middle, and lateral half of ring finger) and lateral palm via the palmar cutaneous branch (which exits proximal to the flexor retinaculum - this is why the proximal palm sensation may be preserved in CTS)
Motor supply to the LOAF muscles: Lumbricals (1st and 2nd), Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis - thenar atrophy results from denervation of opponens pollicis and abductor pollicis brevis

Q3. Structures Passing Above and Below the Flexor Retinaculum

Superficial to the flexor retinaculum (pass ABOVE it):

Palmaris longus tendon (runs in the midline, just superficial)
Palmar cutaneous branch of the median nerve (exits the median nerve ~5 cm proximal to the retinaculum and crosses superficially - this is why CTS does NOT affect palm sensation, only digits)
Palmar cutaneous branch of the ulnar nerve
Ulnar nerve and ulnar artery (pass through Guyon's canal, which is medial to the flexor retinaculum, not through it - technically they pass superficial/adjacent to its medial border)

Deep to the flexor retinaculum (pass BELOW/THROUGH it = contents of carpal tunnel):

Median nerve (compressed here in CTS)
Flexor pollicis longus tendon (1 tendon, in its own synovial sheath)
Flexor digitorum superficialis tendons (4 tendons, in a common synovial sheath)
Flexor digitorum profundus tendons (4 tendons, sharing the synovial sheath with FDS)

Total: 1 nerve + 9 tendons pass through the carpal tunnel beneath the flexor retinaculum.

Note: The flexor carpi radialis tendon passes through a separate compartment within the substance of the flexor retinaculum (not the main tunnel).

Gray's Anatomy for Students; Imaging Anatomy Vol. 3; Tintinalli's Emergency Medicine

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