L3: The Forearm and Wrist

Question 1

List the major bony landmarks of the radius.

Answer 1

• The radial tuberosity - attachment for the biceps brachii tendon
• Shaft
• Radial styloid - a small projection on the end on the radius

Question 2

List the major bony landmarks of the ulna.

Answer 2

• Ulnar tuberosity - attachment site for brachial tendon
• Shaft
• Ulna styloid
• Coronoid process
• Trochlea notch
• Olecranon process

Question 3

What are the possible movements at the wrist joint?

Answer 3

Flexion - move hand forwards

Extension - straighten hand

Adduction - move wrist medially

Abduction - move wrist laterally

Question 4

What are the possible movements at the digits?

Answer 4

Flexion - bend digits forward. This can occur at the PIP, MCP, ICP and DCP
Extension - straighten digits
Abduction - spread out digits
Adduction - bring digits back together

Question 5

What are the possible movements at the thumb?

Answer 5

In addition to those at the digits:

• Flexion - move finger across the palm
• Extension - moves thumb away from the palm in the same plane of the hand
• Abduction - takes the thumb out away from the palm in 90 degrees
• Adduction - brings the thumb towards the side of the palm
• Opposition - this brings the thumb across the palm to pinch the palm of the thumb and little finger together.

Question 6

What is the extensor expansion? What is it’s important?

Answer 6

Found on the dorsal of the digits - it is the special connective attachments by which the extensor tendons insert into the phalanges. On the extensor surface of the thumb, there is no extensor expansion proper: the tendons of the extensor pollicis brevis and longus are inserted separately in the proximal and distal phalanx respectively.

Question 7

Where can we assume all the anterior forearm muscles originate from?

Answer 7

The medial epicondyle - “the common flexor origin”

Question 8

Where can we assume all the posterior forearm muscles originate from?

Answer 8

The lateral epicondyle - “the common extensor origin”

Question 9

How many layers of anterior and posterior forearm muscles are there?

Answer 9

3 in the anterior and 2 in the posterior

Question 10

List the superficial anterior forearm muscles, their distal attachments and function.

Answer 10

(4)

Pronator teres - Acts to pronate the proximal radialunar joint. It inserts on the shaft of the radius. It does not act on the wrist.

Flexor caprii radialis - Flexor of the wrist on the radial side. Inserts on the 2nd metacarpal.

Palmaris longus - Distal half the flexor reticulum and palmar aponeuroses. Does not insert distally on the bones. 20% of people do not have this muscle. Contract helps wrist flexion.

Flexor caprii ulnaris - Flexor of the wrist on the radial side. Inserts on the 5th metacarpal.

Question 11

List the middle anterior forearm muscles, their distal attachments and function.

Answer 11

(1)

The flexor digitorum superficialis - its tendons split into 4 and insert onto the digits. inserts on the proximal digit, before it arrives the tendon splits into 2 and wraps around the digit. Contraction off this muscle flexes the digits. Since its spans the writs it also helps in flexion of the wrist.

Question 12

List the deep anterior forearm muscles, their distal attachments and function.

Answer 12

(3)

Flexor digitorum profundas - has 4 tendons = inserts on the distal phalanx. Deep muscle to the flexor digitorium superficalis. It still flexes the digits. This time the tendon goes all the way to the distal phalanx. It gets here by travelling in between the partition of the flexor digititorum superficialis.

Surrounding the long flexor tendon is a fibrous and synovial sheath. These protect the tendons and anchor them. They allow the tendons to move without friction when the muscles contract.

Flexor pollicis longus - inserts on the distal phalanx of the thumb. Flexes the IPJ. Since it crosses the wrist, it can flex the wrist.

Pronator quadratus - attachment to the distal quarter of the radius and ulna. It contributes to pronation of the forearm. Pronates the forearm

Question 13

List the superficial posterior forearm muscles, their distal attachments and function.

Answer 13

(6) - (3) wrist extensors and (2) digit extensors

Extensor carpii longus - From the lateral epicondyle onto the second metacarpal. Acts to extend the wrist joint.

Extensor carpii brevis - this is the companion muscle of that above but inserts on the 3rd metacarpal. It also acts to extend the wrist joint.

Extensor carpii radialis - inserts on the 5th metacarpal. It acts to extend the wrist.

Extensor digitorum = 4 tendons - each to the 4 fingers

Extensor digiti minimi = 1 tendon to little finger

The extensor digitorum tendons leads to an extensor expansion that overlies the extension of the digits. It is a roughly triangular region. It is a thin fibrous structure that is securely attached to the bone. The tendon of ED blend onto the extensor expansion. Through this attachment the ED can cause extension of the joints. The extensor digiti mini does the same.

Brachioradialis - Lies on the lateral most aspect of the posterior compartment. Brachioradialis forms a buldge on the lateral most affect on the posterior compartment. It does not extend the writs or the digits. Its insertion is on the radius.

Question 14

List the deep anterior forearm muscles, their distal attachments and function.

Answer 14

(5)

Supinator - Deep muscle of the posterior forearm. It has origin from the humerus and part of the ulna and inserts on the radius. It helps us to supinate the proximal radial-ulna joint.

Extensor indicis has one tendon that inserts in the index finger. Gives us control and is important in extension of the index finger. Important in non-verbal communication (pointing). Inserts on the extensor expansion on the dorsum of the finger.

(2) Thumb extensors

Extensor pollicis longus - extensors of the thumb that insert on the distal phalanx. It is able to extend the interphalangeal joint.

Extensor pollicis brevis - extensors of the thumb that insert on the proximal phalanx. It can extend the metacarpophalangeal joint.

(1) thumb abductor

Abductor pollicis longus - inserts on the first metacarpal. Abductor of the thumb as there is another abductor on the thumb that is a small short muscle. When it contracts, it pulls the thumb out.

(Anconeus - a small muscle situated on the posterior aspect of the elbow.)

Question 15

What vessels and nerves supply the anterior forearm muscles?

Answer 15

Vessels: Anterior interosseous branch of the ulnar artery, and the radial artery. Drained by the cephalic and basilica vein.

Nerves:
- Median nerve - almost all. some are supplied by the anterior interosseous branch (the medial side of the

• The ulnar nerve however supplies the lateral side of the flexor digitorum profundas and the flexor carpii ulnaris.

Question 16

What vessels and nerves supply the posterior forearm muscles?

Answer 16

Vessels: Posterior interosseous artery from ulnar artery which travels through the holes in the interosseous membrane. Drained by the cephalic and basilica vein.

Nerves:
- The radial nerve

Question 17

What forms the boundaries and contents of the anatomical snuff box?

Answer 17

The extensor pollicis longus and extensor pollicis brevis (both medial)and abductor pollicis longus (lateral).

In this we can palpate the radial artery. you can also access the cephalic vein here.

The scaphoid bone lies on the floor of the ASB.

Question 18

What forms the boundaries and contents of the cubital fossa?

Answer 18

The superior boundary is formed by a line drawn between the epicondyles. The lateral boundary by the brachioradialis and the medial border by pronator teres.

inside we find the median cubital vein - a communicating vein between the basilica and cephalic vein. Deep to this you can find the median nerve and brachial artery if you peel back the superficial aspect. Deep to this, if you move the brachioradialis out of the way, you can see the radial nerve.

Question 19

What is the anatomy of the carpal tunnel?

Answer 19

The carpal bones form the boundaries of the carpel tunnel. The roof of the carpal tunnel the flexor reticulum. Inside is the median nerve and tendons of forearm muscles.

Question 20

What is carpal tunnel syndrome?

Answer 20

Median nerve entrapment. The skin and muscles that are innervated by median n. branches distal to the CT are affected. It leads to tingling and pain in the part innervated by the median nerve: in the palmar side the digits lateral digits (thumb, index, middle and half of number 4), on the dorsal it is the time of these digits.

Question 21

Briefly describe the bones of the hand.

Answer 21

There are 8 carpal bones arranged in two layers. Layer 1: scaphoid, lunate, triquetrum, Pisiform (from ulna to radius).

Layer 2: Trapezium, Trapeziod, Capitate and Hamate (from ulnar to radial side).

Distal to this is 5 metacarpal bones. Distal to this is the 5 proximal phalanges. Distal to this is the intermediate phalanges and finally the distal phalanges (expect in the thumb where there is only proximal and distal phalanges).

There are joints between these.

Question 22

How do we assess a patient with soft tissue and tendon injury?

Answer 22

Test movements at the joints to test motor function. Also test sensory function by testing the region supplied by the nerve.

Question 23

What are the pulse points on forearm?

Answer 23

Can palpate the radial artery on the side of the thumb. The ulna artery cannot be palpated easily as it is quite hidden.

Brachial - On the inner aspect of the elbow - The brachial pulse can be located by feeling the bicep tendon in the area of the antecubital fossa.