Block 4 Study Guide (GOAT)

Carpals

Bones of the wrist

1.)Scaphoid

2.) Lunate

3.) Triquetrum

4.) Pisiform

5.) Hamate

6.) Capitate

7.) Trapezoid

8.) Trapezium

Metacarpals

Bones of the hand

1.) Thumb - 1st digit

2.) Index - 2nd digit

3.) Middle - 3rd digit

4.) Ring - 4th digit

5.) Pinky - 5th digit

Phalanges

Bones of the fingers

- Proximal

- Intermediate

- Distal

Surgical neck fracture of humerus

Axillary nerve injury

Middle shaft fracture of humerus

- Radial nerve injury

- Wrist drop

Distal end fracture of humerus

Median nerve injury

Medial epicondyle fracture of humerus

Ulnar nerve injury

Acromioclavicular joint

Formed by the acromion of the scapula and the acromial end of clavicle

Glenohumeral joint

Formed by the head of the humerus and glenoid cavity of scapula

Scapulothoracic joint

Formed by the body of the scapula and 3rd rib of thoracic cage

Sternoclavicular joint

Formed by sternum and sternal end of clavicle

Rotator cuff muscles (4)

Supraspinatus, infraspinatus, teres minor, subscapularis

Supraspinatus

Location: rotator cuff

Function: abducts arm

Innervation: suprascapular nerve

Infraspinatus

Location: rotator cuff

Function: lateral rotation of arm

Innervation: suprascapular nerve

Teres minor

Location: rotator cuff

Function: lateral rotation of arm

Innervation: axillary nerve

Subscapularis

Location: rotator cuff

Function: adduction and medial rotation of arm

Innervation: upper/lower subscapular nerves

Teres major

Location: back

Function: adduction and medial rotation of arm

Innervation: lower subscapular nerve

Latissimus dorsi

Location: back

Function: adduction, internal rotation, and respiration

Innervation: thoracodorsal nerve (C6,C7,C8)

Trapezius

Location: back, neck

Function: scapular movement and stability

Innervation: accessory nerve and cervical plexus

Levator scapulae

Location: back

Function: elevates scapula

Innervation: dorsal scapular nerve

Rhomboid minor/major

Location: back

Function: scapular retraction

Innervation: dorsal scapular nerve

Deltoid

Location: shoulder

Function:

-Middle: abduction of arm

-Anterior: flexion/medial rotation

-Posterior: extension/lateral rotation

Innervation: axillary nerve (C5-C6)

Corachobrachialis

Location: humerus

Function: flexion and internal rotation of arm

Innervation: musculocutaneous nerve

Pectoralis major

Location: thorax

Function: adduction/internal rotation of arm

Innervation: medial/lateral pectoral nerves

Serratus anterior

Location: thorax

Function: scapular retraction and extension of arm

Innervation: long thoracic nerve

Biceps brachii

Location: humerus

Function: elbow flexion

Innervation: musculocutaneous nerve

Brachialis

Location: humerus

Function: elbow flexion

Innervation: musculocutaneous nerve

Triceps brachii

Location: humerus

Function: elbow extension

Innervation: radial nerve

Anconeus

Location: humerus

Function: elbow extension

Innervation: radial nerve

Winged scapula

Damage to long thoracic nerve (such as by radical breast mastectomy/trauma):

- Loss of serratus anterior function

- Arm does not extend past 90º

Damage to dorsal scapular nerve:

- Loss of rhomboid major and minor function

- Arm extends past 90º

Veins used for venipuncture

Median cubital, cephalic, basilic. frequently used due to the cross sectional area and visibility

Where does the brachial plexus originate?

C5-T1

Nerves of the brachial plexus

1.) Musculocutaneous nerve: Roots C5–C7; anterior; flexion at both the shoulder and elbow
2.) Axillary nerve: Roots C5 and C6; anterior; helps with shoulder rotation and enables the arm abduction - Teres minor and Deltoid
3.) Median nerve: Roots C6–T1; anterior; movement in the forearm and parts of the hand (innervates THENAR MUSCLES)
4.) Radial nerve: Roots C5–T1; posterior; movements in the arm, elbow, forearm, and hand. “extensor”
5.) Ulnar nerve: Roots C8–T1; anterior; fine motor control of the fingers (innervates HYPOTHENAR MUSCLES)

• flexor carpi ulnaris and the ulnar part of flexor digitorum profundus are dually innervated by median and ulnar nerve

additional brachial plexus nerves- dorsal scapular, suprascapular, subclavius, lateral pectoral, medial pectoral, upper subscapular (USS), thoracodorsal (TD), lower subscapular (LSS), medial brachial cutaneous (MBC), medial antebrachial cutaneous (MABC), long thoracic

Brachial plexus neuropraxia (stretch)

• When someone turns their head too far, it can squeeze (compress) the nerve roots — this happens more in older people.

• When the shoulder gets pulled down hard, it stretches the nerves — this happens more in teens and young adults.

• These injuries can feel like a sharp burn or zap, which is why they’re called “burners” or “stingers,” depending on what it feels like.

- Root compression by rotation of head (older individuals)

- Root traction by downward pull of limb (younger individuals)

- Characterized by burning/stinging

Brachial plexus rupture

• This is when the nerve gets stretched so much that it partly or fully tears.

• This kind of injury causes weak muscles and pain. How bad it is depends on where and how much the nerve is torn.

• Surgery is often needed to fix it.

• ***Might not get full paralysis ONLY if there are only 1 tear of a spinal nerve : there are different multiple axons branching out ***

- Forceful stretch resulting in partial or complete tear of nerve

- Characterized by muscle weakness/pain

- Requires surgery

Brachial plexus neuroma

• This usually happens when a nerve gets cut during surgery.

• A ball of scar tissue/mass grows on the nerve and makes it hurt. This scar stops the nerve from healing.

• Doctors usually need to do surgery to take out the scar tissue.

Occurs when nerve is cut during surgery

- Scar tissue forms painful knot on nerve

- Surgery required to remove

Brachial plexus avulsion

• This is when a nerve root is completely pulled away from the spinal cord.

• It can happen to babies when they are being born, to athletes (childbirth is the most common), or during a hard hit or accident or rock wall climbers if they fall

• There are two types, depending on which nerves are hurt.

• How it’s treated depends on how bad the injury is.

• 2/1000 childbirths

• 2 types : Upper brachial Plexus (C5-C6) and Lower Brachial Plexus (C8-T1)

- Nerve tissue completely separated from spinal cord

- Common during childbirth, athletes, blunt trauma

Upper brachial plexus avulsion

• This is the most common kind of nerve root injury (avulsion).

• It causes something called Erb-Duchenne paralysis.

Signs (What Happens):

• The shoulder feels numb and can’t move, and you can’t bend your elbow.

• Two shoulder muscles — the deltoid and supraspinatus — don’t work, so you can’t lift your arm to the side.

• The infraspinatus muscle doesn’t work either, so your arm turns inward.

• The biceps and brachialis, which help bend the elbow, are paralyzed, so no elbow bending.

• Because the biceps and supinator don’t work, turning the hand upward (supination) is very weak.

• Two big muscles that help bring the arm toward the body (the pectoralis major and latissimus dorsi) are only a little affected.

• summary : is more common and causes problems like a weak shoulder, arm that turns in, and no elbow bending

- C5-C6

- More common

- Loss of function of entire upper arm

Lower brachial plexus avulsion

• This type of injury is less common.

• It causes something called Klumpke’s paralysis.

Signs (What Happens):

• You lose movement or feeling in your wrist and hand.

• The tiny muscles in the hand don’t work, so fingers can’t move properly.

• The forearm and hand muscles shrink and get weak over time, causing a hand shape called “claw hand.”

• summary : is rarer and mostly affects the hand and wrist, making it hard to move fingers and can cause a “claw hand” shape

• Loss of lumbricals 3 and 4

- C8-T1

- Less common

- Loss of function of forearm and hand

- Claw hand

Axillary region lymph nodes

1.) Pectoral

2.) Lateral

3.) Apical

4.) Central

5.) Posterior

Axillary lymph nodes drainage

Subclavian lymphatic trunk -> lymphatic duct -> venous angle

How much of breast's lymphatics drain to axillary lymph node?

~75%

Axillary lymph nodes importance

-Site of breast cancer metastisis

- Removal of lymph nodes may be necessary

- Mastectomy may be necessary

Colle's fracture

when the end of your radius bone (near your wrist) breaks. This usually happens if you fall on your hand with your arm stretched out — like when you try to catch yourself in a fall.

• The broken piece of bone gets pushed backward, kind of like it’s bending the wrong way.

• Sometimes, the little bump on the ulna (the ulnar styloid) can also get pulled off. That’s called an avulsion.

Doctors often call this a “dinner fork” deformity because the wrist ends up looking bent like a fork.

Summary :

Colles’ fracture is a fracture of the radial styloid process with posterior displacement of the fractured fragment into the shaft of the radius. It typically results from a fall on an outstretched hand with an extended arm. The injury may be accompanied by avulsion of the ulnar styloid process.

- Fracture of radial styloid process

- Posterior displacement into shaft

- Occurs from falling on hand with extended arm

Forearm anterior compartment innervation (Of the brachial plexus)

Median nerve: all muscles except 2

Ulnar nerve: flexor carpi ulnaris and flexor digitorum profundus (INNERVATED BY MEDIAN AND ULNAR)

Forearm posterior compartment innervation

Radial nerve

Blood supply of forearm

Radial and ulnar arteries

Muscles of forearm superficial anterior compartment

Pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ularnis

Muscles of forearm intermediate compartment

Flexor digitorum profundus

Radial nerve injury

1. High Up (Proximal to triceps origin):

• You can’t straighten your elbow.

• Your arm might feel like jelly, no reflex when the doctor taps it.

• Your hand hangs down – like it’s too tired to lift up. This is called "wrist drop."

• You can’t move your thumb well.

• You can’t feel parts of your arm and hand, especially the back side.

2. Middle (In the Groove of the Arm Bone – the Humerus):

• Usually happens when your arm bone breaks.

• You can still move your elbow.

• You still get the wrist drop and numbness on the back of the arm and hand.

3. Lower Down (In the Forearm):

• You might hurt the deep part of the nerve.

• You still get wrist drop.

• Your thumb and finger movements are weak.

• But you can still feel things normally!

Summary :

This injury presents differently depending on the level of injury:

• Proximal to triceps origin: Loss of elbow extension, absent triceps reflex, wrist drop due to paralysis of all extensors and the supinator; thumb is flexed and adducted; sensory loss over the dorsolateral lower brachial area, posterior forearm, dorsum of the hand, and radial side of proximal phalanges.

• At the radial groove (often due to humeral fracture): Triceps typically still functions; wrist drop persists; sensory loss is limited to the dorsolateral forearm and hand.

• In the forearm: Deep radial nerve injury causes wrist drop and impaired thumb/metacarpal extension; sensation remains intact.

Median nerve injury

1. Injury Above the Elbow:

• Many muscles in your forearm and hand stop working.

• You can’t bend your wrist well—only one or two muscles still work.

• Your thumb gets weak and can’t move properly (except for one move—pulling in).

• You can’t bend your index and middle fingers right, so when you try to make a fist, those fingers stay straight. This is called "Hand of Benediction." (Due to paralysis of the 1st and 2nd lumbricals)

• You can’t turn your hand to face palm-down (called pronation).

• You also lose feeling in parts of your hand that the median nerve controls.

2. Injury at the Wrist:

• The small muscles that move your thumb get weak, but one thumb muscle still works (abductor pollicis)

• The thumb area/thenar eminence becomes flat and stiff/atrophies—this is called an "ape hand."

• You also lose some feeling in parts of your hand the median nerve normally helps.

Summary :

This injury above the elbow affects forearm and hand muscles. All wrist flexors are paralyzed except flexor carpi ulnaris and the ulnar half of flexor digitorum profundus. Thumb flexors and abductor are paralyzed (but not adductor, which is innervated by the ulnar nerve). Pronation of the forearm is lost. Flexion at the MCP joints is intact due to functioning interossei (ulnar nerve), but paralysis of the 1st and 2nd lumbricals causes incomplete flexion of the index and middle fingers, producing the "Hand of Benediction". Sensory loss occurs in the median nerve distribution.

This injury at the wrist results in paralysis of the short thumb muscles except adductor pollicis. The thenar eminence atrophies (ape hand), but flexor pollicis longus is still functional. Sensory loss is present over the median nerve area.

Ulnar nerve injury

1. Injury at the Wrist:

• Your fingers get stuck in a claw shape: bent at the tips, but stretched at the base joints. This is called a "Claw Hand."

• You can’t bend your ring and pinky fingers well because one of the deeper finger muscles (flexor digitorum profundus) isn’t working.

• Little finger muscles don’t work at all.

• You can’t spread or pinch your fingers together well, so it’s hard to write or play piano.

• You also lose feeling in the pinky side of your hand.

2. Injury at the Elbow:

• Some bigger muscles stop working, like flexor carpi ulnaris (it helps bend the wrist) and part of flexor digitorum profundus.

• This makes the wrist weaker at moving sideways, and the hand may bend a little outward (away from the body).

Summary :

This injury at the wrist results in claw hand due to paralysis of interossei muscles and medial lumbricals, causing hyperextension at MCP joints and flexion at IP joints. The flexor digitorum profundus tendon is paralyzed, so flexion of the ring and little fingers at the distal phalanges is not possible. Hypothenar muscles (small muscles of the little finger) are paralyzed. Finger abduction and adduction are impaired, affecting fine motor skills like writing and piano playing. Sensory loss occurs over the ulnar nerve area.

Injury at the elbow leads to paralysis of flexor carpi ulnaris and the medial portion of flexor digitorum profundus. Ulnar deviation of the wrist is weakened, causing the hand to be abducted and extended.

Carpel tunnel and carpel tunnel syndrome + parts of it

The clinical significance of this lies in its anatomical structure and its vulnerability to median nerve compression. The carpal bones form two rows that create a concave anterior groove—the carpal groove. This is covered by the flexor retinaculum, a double-layered membrane inserting at the tubercle of the scaphoid, pisiform, tubercle of trapezium, and hook of hamate. Together, these form the carpal tunnel, which transmits the median nerve and flexor muscle tendons.

Carpal Tunnel Syndrome occurs when the median nerve is compressed within this tunnel, often due to conditions like hypothyroidism, rheumatoid arthritis, pregnancy, or amyloidosis, leading to pain, numbness, or weakness in the median nerve distribution of the hand.

Clinical significance of Scaphoid and Lunate injuries

Scaphoid fractures are the most common type of carpal bone fracture, typically occurring at the narrowed waist between its proximal and distal poles.

The lunate is the most frequently dislocated carpal bone, making it a key consideration in wrist trauma assessments.

Anatomical snuffbox

A clinically significant region on the dorsum of the hand. It serves as a landmark through which the radial artery enters, contributing to the formation of the dorsal arterial arch of the hand and serving as the principal artery of the thumb via the deep palmar arch.

Borders:

• Superior: Tendon of extensor pollicis longus

• Inferior: Tendons of extensor pollicis brevis and abductor pollicis longus

Contents:

• Radial artery

• Superficial radial nerve

Pectoralis major

a large superficial chest muscle, originates from the clavicle, sternum, and upper ribs and inserts on the humerus. It functions to adduct, medially rotate, and flex the shoulder joint, and assists in respiration when the shoulder is fixed. It is innervated by both the medial and lateral pectoral nerves (C5–T1).

Pectoralis minor

originates from ribs 3–5 and inserts on the coracoid process of the scapula. It depresses and stabilizes the scapula, rotates the glenoid cavity inferiorly, and assists in respiration. It is innervated primarily by the medial pectoral nerve (C6–T1).