Lecture 9: The Forearm flexor compartment and Wrist

Question 1

What is the ‘head’ of the bone and at what end is the head of the radius and ulna

Answer 1

The head is the smaller end of the bone. The head of the radius is at the proximal end of the forearm (sup R/U joint) whereas the head of the ulna is at the distal end of the forearm (inf R/U joint)

Question 2

How does the position of the flex/pro comp of the forearm and ext/ sup comp change from the superior to inferior Radio-ulnar joint

Answer 2

There are 4 segments at the sup joint, with a line from post to ant going through the Radius and ulna forming a boundary, with the two middle squares containing the flex and ext compartment of the arm.

The outer semicircles contain forearm compartments, with the Medial semicircle = the flex/pro comp of forearm and Lateral semicircle= ext sup comp.
Eventually the forearm at the distal R/U joint has only a horizontal line with Anterior compartment : Flex and pro and Posterior compartment : Extend and Sup compartment

Question 3

Describe the articulation at the distal radio-ulnar joint

Answer 3

The head of the ulna articulates with the tail of the radius by fitting into the ulnar notch. In between them is the sacciform recess which extends a little higher and underneath the ulnar but in the layer above the fibrous articular disc (excludes ulnar from proper wrist joint).

Question 4

What is the lateral pointy part of the bone sticking out from the radius or the ulnar

Answer 4

Styloid process

Question 5

What is the interosseous membrane and its function

Answer 5

Interosseous membrane is investing fascia that joins the medial border of the radius to the lateral border of the ulna. Its function is to act as a hinge for radial rotation, a place for muscle attachement and a medium for transmission of force from radius to ulnar to prevent excessive force on the head of the radius

Question 6

What bones articulate at the wrist joint proper?

Answer 6

The radius with the the fibrous articular disc proximally and then the scaphoid, lunate and triquetrum distally.

Question 7

What are the other 2 joints in the wrist (apart from wrist joint proper) and what bones articulate there

Answer 7

The mid carpal/ transverse intercarpal joint which is a n shape between the two rows of 4 carpal bones. AND
The carpo-metacarpal joint: between the distal row of carpal bones and the medial 4 digits (metacarpal bones)

Question 8

Compare the range of movement available in the 3 joints of the wrist (from distal to proximal)

Answer 8

At Carpal- metacarpal joint there is very little movement
At midcarpal joint there is some flexion/ extenion
At Wrist joint proper there is flexion/ extension + abduction/adduction + a little rotation.

Question 9

What are the 8 carpal bones of the wrist: proximal then distal row, from lateral to medial both rows

Answer 9

Scaphoid, Lunate, Triquetrum, Pisiform
Trapezium, Trapezoid, Capitate, Hamate

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Question 10

What is the carpal tunnel made out of and what does it do

Answer 10

It is the space enclosed by the carpal bones and covered by the flexor retinaculum which is a thickening of the fascia which holds the flexor tendons of the elbow and stops them from bow stringing. It attaches to the pisiform and hamate bones medially and the scaphoid and trapezium laterally.

Question 11

What are the 3 types of bones that make up the hand (from proximal to distal )

Answer 11

The carpals which make up the wrist. The metacarpals which make up the palm and the phalanges that make up the digits/ fingers.
The phalanges have a proximal, middle and distal for the 4 fingers and no middle for the thumb.

Question 12

What are the 4 superficial forearm muscles, 1 intermediate forearm muscle and 3 deep forearm muscles

Answer 12

Superficial: Pronator Teres, Flexor carpi radialis, Palmaris longus, Flexor carpi ulnaris
Intermediate: Flexor digitorum superficialis
Deep: Flexor pollicis longus, Flexor digitorum profundus and Pronator quadratus

Question 13

What is the origin and insertion of the superficial forearm muscles

Answer 13

Origin: at the common flexor tendon except for pronator teres on the supracondylar ridge
Insertion;
Pronator Teres - middle lateral surface of the radius
Flexor carpi radialis - the base of 2nd metacarpal
Palmaris longus - palmar aponeurosis
Flexor carpi ulnaris- pisiform carpal bone

Question 14

What is the action of the 4 superficial forearm muscles

Answer 14

PT: pronates the forearm

FCR and FCU ( and PL) flexes the forearm

Question 15

What is the origin and insertion and movement of the intermediate forearm muscle-

Answer 15

Flexor digitorum superficialis O; radial and humero ulnar heads,
Insertion: 4 tendons that insert on the base of the middle phalanx of the 4 digits. Insertion is slit in two

Question 16

What is the action of the intermediate forearm muscle

Answer 16

It flexes the fingers, giving more control on individual flexion

Question 17

What is the origin and insertion and movement of the deep forearm muscles

Answer 17

O: interosseous membrane: FDP+ PQ is ulnar, FPL is radius
Insertion;
FPL: base of the distal phalanx of the thumb
FDP: splits into 4 tendons to base of distal phalanx of digits
PQ: last inner part of the radius.

Question 18

What is the action of the deep forearm muscles

Answer 18

FPL and FDP : flex and PQ pronates

Question 19

What tendons of forearm muscles pass under flexor retinaculum and through the common synovial sheath of the palm

Answer 19

Long tendons of Flexor digitorum superficialis, Flexor digitorum profundus and Flexor pollicis longus (which may have its own sheath

Question 20

What tendons of forearm muscles pass on top of the flexor retinaculum

Answer 20

Palmaris Longus and Flexor carpi ulnaris

Question 21

How does the median nerve travel down the forearm and what muscles does it innervate along the way (including branches) for motor and cutaneous

Answer 21

Motor:

• Main branch : PT, FCRadialis, PalmL, FDSup,
• Anterior interosseous (smaller deeper branch) : PQ, FpollicisL, Lateral half of FDprofundus,
• Recurrent branch after retinaculum which does Thenar, 1st and 3rd lumbricals

Cutaneous: 3.5 digits including thumb

• Palmar cutaneous branch for skin on the palm
• Proper palmar digital nerve

Question 22

How does the ulnar nerve travel down the forearm and what muscles does it innervate along the way (including branches) for motor and cutaneous

Answer 22

Cutaneous: medial 1.5 digits

• palmar cutaneous branch
• proper palmar digital nerves

Motor:

• FCUlnaris and Medial half of FDProfundus
• Deep branch of ulnar nerve does most intrinsic muscles of the hand

Question 23

Describe the arterial supply to the forearm from the cubital fossa

Answer 23

At the cubital fossa the brachial artery splits into Radial and Ulnar arteries which go down the side of their bones. There is a branch of the ulnar artery which is the common interosseous branch towards the midline of the arm which splits into the anterior and posterior interosseous artery.

There are recurrents for radial and interosseous , two for ulnar.

The superficial and deep branches of the ulnar and radial arteries form arches.