📚 Question Bank

Pectoralis minor has no action at the shoulder joint.

Its origin is from 3,4,5 ribs near the costochondral junction and inserts at the medial border and the upper surface of the coracoid process. The pectoralis minor is an accessory muscle of inspiration, which stabilizes the scapula by pulling it anteriorly and inferiorly.

Movements at the shoulder joint:

Movement Flexion Extension

Abduction Adduction

Medial rotatio n

Lateral rotatio n

Prime Movers Pectoralis majorDeltoid Deltoid (Spinal part)

Deltoid

Pectoralis majorLatissmus do rsi

Subscapularis Infraspinatus

Synergists Coracobracialis

Teres majorLatissmus dorsiT riceps brachii (Long head)

Supraspinatus

Teres majorTriceps brachii (L ong head)

Pectoralis majorDeltoidLatiss mus dorsiTeres major

Teres minorDeltoid

Lateral rotation of the humerus increases the range of abduction.

When the arm is abducted without rotation, the greater tubercle comes in contact with the coracoacromial arch, preventing further abduction.

If the arm is then laterally rotated 180°, the tubercles are rotated posteriorly and the more articular surface becomes available to continue elevation. Hence, the range of abduction is increased.

A normal scapulohumeral rhythm is in the ratio of 2:1.

Scapulohumeral rhythm is the ratio of the glenohumeral movement to the scapulothoracic movement during arm elevation.

For instance, if the arm is abducted to a 90° angle, the glenohumeral elevation is 60° and the scapulothoracic rotation is 30°. Thus, the humerus and scapula move in a 2:1 ratio.

The long head of biceps is intracapsular.

The fibrous capsule which envelopes the shoulder joint is attached medially to the glenoid neck at a variable distance from the glenoid labrum. The capsule includes the supraglenoid tubercle, to which the long head of the biceps attaches, and which is therefore intracapsular.

Rotator interval is an area between the supraspinatus and subscapularis.

The rotator interval is a medially-based, triangular area that is not covered by the capsule.

It is present between the superior edge of the subscapularis and the anterior edge of

the supraspinatus with the coracoid as the medial boundary of the interval. It is reinforced by the coracohumeral ligament, the superior glenohumeral ligament, and fibers from the supraspinatus tendon laterally.

Prono-supination movements do not happen at the radiocarpal (wrist) joint. Supination and pronation mainly occur at 3 joints:

• Humeroradial
• Superior radioulnar joints
• Inferior radioulnar joints

The middle radioulnar joint is a syndesmosis (fibrous) joint that mainly helps bind the radius and ulna together. It also helps in weight transmission from radius towards ulna.

During the intracapsular arthroscopy, the lateral epicondyle is not seen since it is extracapsular.

The capsular ligament of the elbow joint is attached anteriorly just above the coronoid and radial fossa and posteriorly above the olecranon fossa.

Note: Medial epicondyle is also extracapsular.

The average carrying angle is approximately 17°.

The carrying angle is the angle defined by the border of the fully supinated forearm and the long axis of the humerus when the elbow is fully extended.

It is usually 10°-15° in males and more than 15° in females. The absolute angle varies from individual to individual and also increases as age increases.

In clinics, it's necessary to see the carrying angle of the contralateral side instead of just on a single side. But anything between 5 to 15 degrees is considered normal. The carrying angle is used to identify varus or valgus in the elbow joint. It decreases in cubitus varus and increases in cubitus valgus.

In the above scenario, the area of tenderness and the pain in the ring and little finger are suggestive of the hook of hamate fracture. The pain in the ring and little finger is related to the close proximity of the ulnar nerve which could get affected due to a fracture of hook of hamate.

The hamate is cuneiform and bears an unciform hamulus (hook) that projects from the distal part of its rough palmar surface.

Mnemonic for Carpal Bones -

She(S) - Scaphoid Looks(L) - Lunate

The epiphysis of the first metacarpal is present at the base. All the other metacarpals have epiphysis at the head.

Features of the first metacarpal:

• Epiphysis at the head is an aberrant epiphysis
• It is the shortest and stoutest of all metacarpals
• The palmar (medial) surface is longitudinally concave and divided by a ridge into a larger
• lateral

(anterior) and smaller medial (posterior) part

• The base has a convexo-concave articular surface to make a saddle synovial joint with trapezium The first metacarpal fracture at the base of the thumb is called Bennett's fracture. It is

an intraarticular fracture that separates the palmar ulnar aspect of the base of the first metacarpal from the rest of the first metacarpal.

The image below shows a radiograph of a hand at 2.5 years (dorsopalmar projection). Note the early stages of ossification in the epiphyses at the proximal ends (base) of the phalanges and first metacarpal; the distal ends of the remaining metacarpals and radius.

The fascia around the axillary vessels and brachial plexus is called the axillary sheath. It is derived from the prevertebral fascia.

Clinical correlation:

• In a brachial plexus nerve block, the axillary sheath localizes the anesthetic solution to the
• nerve plexus.
• Chronic retropharyngeal abscess in TB may spread to the axilla or to the superior mediastinum.
• But it never spreads to the posterior mediastinum because prevertebral fascia fuses to restrict the spread.

Structure labelled in the picture is artery piercing the clavipectoral fascia called thoracoacromial artery.

Clavipectoral fascia envelops the subclavius and pectoralis minor. Medially it forms

the costocoracoid ligament. Laterally it is connected to the axillary fascia by suspensory ligament of axilla (Gerdy's ligament). The structures piercing clavipectoral fascia are:

• 1 vein: Cephalic vein
• 1 artery: Thoracoacromial artery (associated veins and lymphatics)
• 1 nerve: Lateral pectoral nerve.

The space around the shoulder joint where the radial nerve may be compressed is the triangular interval. It contains the profunda brachii vessels.

The axillary nerve is likely to be affected as it is one of the contents of the quadrangular space.

Quadrangular space syndrome is a condition is caused by hypertrophy or fibrosis of the quadrangular space muscles which impinge on the axillary nerve. Patients present with weakness of the shoulder movements.

Bicipital aponeurosis is not a content, it forms the roof of cubital fossa. Biceps tendon is a content of cubital fossa.

Note - The Radial nerve is given as content of the cubital fossa in some books, in others, it's excluded as a content of cubital fossa due to its extreme lateral position.

The marked region is the anatomical snuffbox. The superficial branch of radial nerve forms the roof of the anatomical snuffbox. Tenderness in this region is suggestive of a scaphoid fracture, a common injury after a fall on an outstretched hand.

Anatomical snuffbox boundaries:

Lateral wall:

• Abductor pollicis longus (APL),
• Extensor pollicis brevis (EPB)

Medial wall:

• Extensor pollicis longus (EPL).

Roof:

• Cephalic vein
• Superficial branch of radial nerve
• Floor:
• Radial styloid, Scaphoid, Trapezium, and 1st Metacarpal.
• Only content: Radial artery

The given clinical scenario is suggestive of carpal tunnel syndrome. The carpal tunnel does not contain flexor carpi ulnaris tendon (FCU).

Carpal tunnel contents (1– structures): Also can be taken as 4 structures only if FDP and FDS are counted as 2 structures.

• Flexor digitorum profundus (FDP-4 tendons).
• Flexor digitorum superficialis (FDS-4 tendons).
• Flexor pollicis longus (FPL-1 tendon).
• Median nerve between tendons of FDP and FDS.

Superficial to the carpal tunnel and the flexor retinaculum, the ulnar artery and ulnar nerve pass through the ulnar tunnel or Guyon's canal.

Flexor carpi radialis is the only content in the lateral slip, not medial slip.

Flexor retinaculum (carpal tunnel): 1– structures in total.

• 4 tendons of flexor digitorum superficialis (FDS), 4 tendons of flexor digitorum profundus

(FDP), both in a common synovial sheath (in ulnar bursa).

• 1 Median nerve
• 1 Flexor pollicis longus (FPL) with its synovial sheath (in radial bursa).
• Medial superficial slip of flexor retinaculum (called volar carpal ligament):
• Volar carpal ligament forms the "Guyon's canal"
• Guyon's canal contains ulnar nerve and vessels.
• Lateral deep slip of flexor retinaculum:
• Flexor carpi radialis (FCR) tendon is the only content.
• Flexor retinaculum has 4 attachments:
• Medially:
• Pisiform
• ˜ook of the hamate
• Laterally:
• Tubercles of scaphoid
• Trapezium

Extensor pollicis longus is not present in the fourth compartment of the extensor retinaculum. Posterior interosseous nerve and anterior interosseous artery are present in the fourth compartment.

Extensor retinaculum attachments:

• Medially - Pisiform and triquetral.
• Laterally - Anterior border of the radius.

Wing tendons refer to the insertion of lumbricals and interossei to the corners of the dorsal digital expansion or simply extensor expansion.

Dorsal digital expansion/ Extensor expansion:

• Formation: By extensor tendons expanding "extensor expansion"
• Location: Back of digits "dorsal digital expansion"
• Extensors making the expansion: ED, EPL (extensor digitorum and extensor pollicis longus)
• Muscles joining the expansion: EDM, EI, EPB (extensor digiti minimi, extensor indicis, and extensor pollicis brevis)

Extensor expansion triangular hood attachments: (The shape of expansion)

• Apex: Distal phalanx
• Central region: Middle phalanx (in the thumb, attached to proximal phalanx)
• Corner of the base: Sides of MCP joint (in the thumb, attached to muscles)
• Extensor hood: Lumbrical, interossei, and extensor digitorum muscles (in the thumb, the adductor pollicis and abductor pollicis brevis muscles)

The given clinical scenario along with the image showing infantile spasms is suggestive of Aicardi syndrome, an X-linked dominant disorder associated with agenesis of the corpus callosum. The fibres of the tapetum originate from both the body and splenium of the corpus callosum.

The given clinical scenario of split-brain syndrome is a type of disconnection syndrome following corpus callosotomy. Commissural fibres constitute the surgically resected structure i.e. the corpus callosum.

Corpus callosotomy is a procedure where the corpus callosum is resected as a last resort to manage intractable epileptic seizures. The resultant predicament is that the patient would behave in some ways as if it were two separate minds.

The given scenario of ipsilateral paralysis, hypertonia, hyperreflexia and ankle clonus (image) is suggestive of a corticospinal tract lesion. The anterior limb of the internal capsule does not contain corticospinal fibres. It passes through the posterior limb of internal capsule.

Corticospinal fibres have the following course as shown in the image below:

The given clinical scenario is suggestive of Sydenham's chorea, a complication of rheumatic fever. The choreic movements are caused by the destruction of D2 neurons of the striatum. The neostriatum consists of the caudate nucleus and putamen.

The image given below shows Sydenham's chorea in a patient.

Nomenclature of basal ganglia:

• Corpus striatum: Caudate nucleus + putamen+ globus pallidus
• Lentiform nucleus: Putamen + globus pallidus
• Neostriatum: Caudate nucleus + putamen

Wilson's pencils are thin myelinated or unmyelinated axons, which are afferents and efferents passing through the striatum.

The image given below shows micrograph of the putamen (top-right) and external globus pallidus

(bottom-left), showing Wilson's pencils (blue, diagonal, linear structures).