Formed of two bones, the radius lateral ward ; the ulna medial ward. The two bones are joined together between them by a membrane; the inter-osseous membrane.



The radius

Long bone, it is articulated in proximal with the humerus, into distal with the bones of the carpus, in medial with the ulna. It can be divided into different parts : a body, two epiphysis a proximal and distal.

1) The body:

Triangular at the cut, it presents three faces three edges. Ventral curve and medial essential to the movement of pronosupination.

a) Surfaces:

(insertions give to muscles which is distributed to the hand).
Ventral face, Dorsal Face, Side Face.

b) Edges

Ventral edge:
begin with the radial, oblique tuberosity into side and distal.
Medial edge:
(Inter-osseous Edge); marked well, insertion gives to the inter-osseous membrane.
Dorsal edge:

2) Epiphysis


a) - Proximal epiphysis , divided into three parts

  • The radial head
  • The collar
  • Radial tuberosity

The radius head : Cylinder packing ring, entirely covered with cartilage, articular, divided into two parts:

- Cranial Part -> it is articulated with the humerus, it is divided into two parts: The radial articular small cavity (radial cup, fovea), it is articulated with the capitulum and the bevel which is articulated with the furrow capitulo-trochléaire of the humerus in proximal.

- Peripheral Part -> Circumference articular radial, circumferential, completely articular, its height medial is more important than its side height, it is articulated with the ulna in medial.

The collar : under the radial head, cylindrical, narrowed, fastener gives to the capsule. It is directed in médial and distal.

Radial tuberosity : located under the collar, in medial and dorsal of him, insertion gives to the muscle biceps brachial. (tuberosity bicipitale).

b) Distal Epiphyse

bulky, quadrangular (6 FACES)
- Ventral Face:
plane, (insertion to the square muscle pronator gives).
- Dorsal Face:
present the dorsal tuber, (in médial of the tuber furrow of passage of the tendon of the muscle long bungee cord of the inch, into side of the tuber passage of tendons of the bungee cords of the wrist and tendon bungee cord of the inch).
- Side Face:
by the process styloïde radius is prolonged.

- Medial Surface:
(junction of the interosseux edge) articulates itself with the ulna, it has an articular surface: ulnar incisure of the radius.

- Distal Face:
(carpienne), triangular at side top, it is articulated with two bones of the carpus: le scaphoïde en latéral, le lunatum en médial. A facet for each bone separated by a peak foams. Articular surface looks into ventral and distal.

- Proximale Face:
welded with the body of the radius frequently fractured zone. (presence of the cartilage of conjugation in the child)

The ulna

Located in médial of the radius, it is articulated in proximal with the humérus, into distal with the first line of the carpus (indirectly), into side with the radius.
Long Os a body and two épiphyses, a proximale, distal. It is longer than the radius.


Triangular with the cut:
- Ventral Face
- Médiale Face
- Dorsal Face

- Ventral Edge
- Side Edge
- Dorsal Edge

The body swells into distal, it is rectilinear in proximal, it curves into distal. (concavity into side)

a) Faces

- Ventral Face and Médiale:
(insertion of the deep flexor of the fingers).

- Face Dorsale :
present a vertical peak which divides this face into two. (At the level of the slope médial sets the ulnar extensor of the carpus, under the anconné muscle; on the side slope sets four staged muscles of crânial into caudal for the extension of the inch and the index).

b) Edges

The only marked edge is the side edge which looks at the radius, it gives insertion to the inter-osseous membrane: inter-osseous edge. The dorsal edge is palpable under cutaneous (frequent open fracture).


a) Epiphyse Proximale:
it is complex, one can divide it into two parts; circumscribing the socket: incisure trochléaire.
Into dorsal and proximal one finds: The OLECRANE,
Into ventral and distal, one finds: PROCESS CORONOÏDE.

* Olécrâne:
dorsal part of the épiphyse proximale presents several faces (6).
- Dorsal Face:
(insertion gives to the triceps muscle).
- Proximale Face:
(also insertion gives to the triceps muscle), it presents into ventral a top, the nozzle of the olécrâne which abuts against the small cavity olécrânienne of the humérus.
- Ventral Face:
articular face (incomplete incisure trochléaire)
- Two Peripheral Faces:
une médiale et une latérale (qui donnent insertions à la capsule et aux ligaments du coude).

* The Coronoïd Process finishes into ventral and distal the socket (incisure trochléaire), it presents several faces.
- Cranial surface:
prolong the articular surface of the olécrane, it is prolonged by a nozzle (Nozzle coronoïde) -> in inflection the nozzle is placed in the small cavity coronoïdienne of the humérus.
- Ventral Face:
marked by the ulnar tuberosity (insertion gives has a flexor of the elbow, the muscle brachial).
- Médial surface:
tuber coronoïde (on which sets the average ulnar collateral ligament and the capsule)
- Lateral surface:
in proximal, a small articular surface which is articulated with the circumference of the radial head: radial incisure of the ulna (small sigmoid cavity). Into distal pit and peak supinatrice (insertion of the muscle supinator)

* Trochlear incisure :
(large sigmoid cavity) is formed by the olécrane and the coronoïde. It presents a longitudinal peak, two slopes side a médial this last to develop more.

b) Distal Epiphyse: Ulnar head
Very small, fine it is divided into two parts:
articular, a styloïde.
Ulnar articular circumference:
side, round, answers ulnar incisure of the radius.
Ulnar Styloïde process:
located in dorso-médial compared to the ulnar head, of conical form.



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