RADIUS (FOREARM BONE)
ulna and radius (forearm bone) forms the forearm of the body
– Radius or radial bone is a lateral bone of forearm.
– It is homologous to tibia of lower limb.
– It has : Upper end
Superior concave surface of the radial head articulates with capitulum of humerus at elbow joint .
Radius articulates at the radial notch of the ulna.
distal end articulates with the ulna at ulnar notch and with the surface of the scaphoid and lunate carpal bones .
• Side determination
1) Upper end : have a disc shaped head
2) Lower end : it is expanded with a styloid process.
3) At lower end :
– Anterior surface : It is in the form of thick prominent ridge.
– Posterior surface : It presents 4 grooves ( for extensor tendons ).
4) Medial border is the sharpest border.
– There is a radial tuberosity close to neck.
5) Lower end : on posterior surface it presents a tubercle and is called as dorsal tubercle of lister.\
1) The head
– It is Disc shaped
– It is covered with hyaline cartilage.
– Superior concave surface articulates with capitulum of humerus at elbow joint .
2) The neck
– It is enclosed by lower margin of annular ligament.
3) The tuberosity
– It lies just below the neck ( medial part ).
– Posterior part is rough
– Anterior part is smooth.
– It has ,
3 borders – Anterior border
Medial or interosseous border
3 Surfaces – Anterior surface
1) The anterior border :
– Extends from anterior margin of radial tuberosity down close to the styloid process.
– It is oblique ( in upper half of shaft )
Vertical ( in lower half )
– Oblique part is called as anterior oblique line.
2) The posterior border :
– Mirror image of anterior border
– Upper oblique part is called as posterior oblique line.
3) Medial or interosseous border :
– Sharpest border
– Extends from radial tuberosity to posterior margin of ulnar notch .
1) The Anterior surface
– Lies between anterior and medial border
2) The posterior surface
– Lies between posterior and medial border
3) The lateral surface
– Lies between anterior and posterior borders.
• Lower end
– It has 5 surfaces
1) The Anterior surface
2) The Posterior surface
3) The medial surface
4) The lateral surface
5) The Inferior surface
1) The Biceps brachii
– Inserted into posterior part of radial tuberosity.
2) The supinator
– Inserted into the upper part of lateral surface.
3) The Pronator teres
– Inserted into middle of lateral surface.
4) The Brachioradialis
– Inserted into lowest part of lateral surface just above styloid process
5) Flexor digitorum superficialis ( radial head)
– Originates from anterior oblique line and upper part of anterior border.
6) The flexor pollicis longus
– Originates from upper two-thirds of anterior surface
7) Pronator quadratus
– Inserted into anterior surface ( lower part ) and into triangular area on medial side of lower end .
8) The abductor pollicis longus and the extensor pollicis brevis muscles
– Arises from posterior surface.
9) The quadrate ligament
– Attached to medial part of neck
10) The oblique cord
– Attached just below radial tuberosity on medial side.
11) The articular capsule of wrist joint
– Attached to Inferior articular surface ( anterior and posterior margins )
12) The articular disc of inferior radioulnar joint
– Attached to ulnar notch ( lower border )
13) The extensor retinaculum
– Attached to lower part of anterior border.
14) The interosseous membrane
– Attached to interosseous border ( lower 3/4 th ).
15) The first groove :
– Between lowest part of anterior border and styloid process
– abductor pollicis longus and extensor pollicis brevis passes through it .
16) The second groove :
– Between styloid process and dorsal tubercle
– extensor carpi radialis longus and extensor carpi radialis brevis tendons passes through it.
17) The third groove ( medial to dorsal tubercle ):
– It is oblique.
– Gives passage to extensor pollicis longus tendon
18) The fourth groove:
– It gives passage to tendons of extensor digitorum , extensor indicis, posterior interosseous nerve and anterior interosseous artery on medial aspect.
19) The tendon of extensor digiti minimi passes at the junction of lower ends of radius and ulna.
20) The tendon of extensor carpi ulnaris transverses between head and styloid process of ulna.
1) The shaft :
– Ossifies from primary centre .
– Appears during 8 th week of development.
2) The lower end :
– Ossifies from a secondary centre
– Appears during first year
– Fuses at 20 years
– It is growing end of bone
3) The upper end ( head ):
– Ossifies from secondary centre
– Appears during 4 th year
– Fuses at 18 years.
• Clinical anatomy :
1) Colle’s fracture
-Radius (forearm bone) commonly gets fractured about 2 cm above its lower end .
– It causes due to fall on outstretched hand.
– Distal fragment gets displaced upwards and backwards.
– Radial styloid process comes and lie proximal to ulnar styloid process.
– If distal fragment displaces anteriorly , it is called as Smith’s fracture.
2) Pulled elbow
– A sudden jerk on hand of a child may dislodge the head of radius from the grip of the annular ligament .
– This is known as subluxation of head of radius.
– Head can normally felt in a hollow behind the lateral epicondyle of the humerus.
3) SMITH FRACTURE
– Smith fracture is a fracture of distal one – third of radius with palmar displacement.
– Also know as reverse Colle’s fracture.
– It is less common than Colle’s fracture and is easily confused with Colle’s fracture.
– It has a clear fracture dorsally with communition of palmar surface.
– This uncommon fracture is seen in adults and in elderly.
• Mechanism of injury
– Fall on back of dorsum of hand
– Fall on forearm in supination
– Directed blow to flexed hand.
• Clinical features
– Pain , swelling, deformity, and loss of weight function
– Garden spade deformity
– AP view of wrist shows corpus proximal displaced
– There will be anterior displacement of fragment with palmar angulation of distal radius articular surface
– The ulnar styloid process is frequently fractured.
– Closed reduction and immbolization in a long arm cast with forearm in supination and wrist in extension.
– Immbolization for 6 weeks
– For unstable fracture , fixation with percutaneous k- wire or open reduction with plate fixation may be required
– Misinterpretation of radiographs for Colle’s fracture.
-Stiffness of joints
– Subluxation of inferior radioulnar joint
– carpal tunnel syndrome
– Sudeck’s dystrophy
– Rupture of extensor pollicis longus tendon
– median nerve neruropathy
– ulnar nerve neruropathy
– radiocarpal arthrosis
– Compartment syndrome
4) BARTON ‘S FRACTURE
– Barton’s fracture is the intra Articular fracture of lower end of radius.
– Fracture line is oblique , separating large vholar or dorsal fragments.
* Dorsal Barton
– It is dorsal rim fracture of distal radius with dorsal subluxation / dislocation
– It is varient of Colle’s fracture.
– fall with Dorsiflexion and pronation of distal forearm on flexed wrist.
• Clinical features
– Severe pain , swelling, tenderness over wrist
– Restricted wrist movements with painful Dorsiflexion.
– Best seen in lateral view.
– dorsal lip of distal radial articular Surface is displaced proximally and posteriorly.
– Conservative : short arm cast with wrist in neutral position.
– Surgery – Unstable fracture is fixed by percutaneous pins or small screws.
* Volar Barton
– It is a palmar rim fracture of distal radius.
– Palmar tensile stress and dorsal shear stress
– Usually combined with radial styloid fracture.
– Palmar rim of distal radial Articular surface is displaced dorsally.
– Proximal and posterior may be associated with subluxation /dislocation.
– Reduction is simple
– long arm cast is used
– K wire fixation , external fixator is used and buttress plate is used .
– Ellis T shaoed buttress plate is used.