Ulna and Radio by A.Griguolo

Generality

Ulna and radio are the two long and even bones of the human body, which form the skeleton of the forearm.

Bordering the humerus, in a proximal position, and with the wrist bones in a distal position, the ulna and radius are anatomically and physiologically important for their contribution to the important elbow and wrist joints.

Like all bones in the human body, ulna and radium can also be broken.

What are Ulna and Radio?

Ulna and radio are the two equal bones of the human body, which make up the skeleton of the forearm . The forearm is that anatomical portion of the upper limb between the upper arm and the hand, below (assuming, of course, that the natural position of the lower limb is along the side and with the hand facing down).

Anatomy

Ulna and radio are two long bones ; as long bones, therefore, they are developed in length and characterized by a narrow central portion, which takes the name of body or diaphysis, and by two voluminous extremities, which possess the name of proximal epiphysis and distal epiphysis .

Ulna and radio run parallel to each other, with the ulna residing in a medial position with respect to the radium (if the hand is facing the palm towards the observer).

Being the bones of the forearm, ulna and radium adjoin the elbow, superiorly, and with the wrist, below.

Brief review of the medial-lateral terms

Recalling that the sagittal plane is the anteroposterior division of the human body from which two equal and symmetrical halves are derived, " medial " means "near" or "closer" to the sagittal plane, while " lateral " means "far" or " farther "from the sagittal plane.

Examples:

The second toe is lateral to the big toe, but is medial to the third toe.
The tibia is medial to the fibula, which is lateral to the tibia.

Ulna

Between ulna and radius, the ulna is the medial bone of the forearm (assuming, of course, that the upper limb is extended along the body and the palm of the hand is facing the observer).

PROXIMAL EPIXIS OF THE ULNA

The proximal epiphysis of the ulna is the extremity of the ulna closest to the humerus, ie the bone of the anatomical region known as the arm.

The proximal epiphysis of the ulna is important, from the anatomical point of view, for its active participation in the elbow joint.

Morphologically the proximal epiphysis of the ulna is characterized by:

The so-called olecranon . Representing the absolute most proximal part of the ulna, it is the hook-shaped bone projection that contributes to the formation of the trochlear recess (which will be discussed later).
The olecranon is also a seat for the initial head of the flexor carpi ulnar muscle and a coupling seat for the terminal heads of the anconeus muscles (a part) and brachial triceps.
The " coronoid process ". Located on the anterior surface of the ulna and projected forward, it is the bony crest that contributes, with the olecranon, to the formation of the aforementioned trochlear recess.
The ulnar collateral ligament and the pronator round muscle originate from the coronoid process.
The so-called trochlear recess (or semi-lunar incisura ). It is the wrench-shaped depression with a smooth surface, used to house the humerus trochlea and generate the elbow joint.
The so-called radial recess . Placed sideways to the trochlear cavity, it is the small depression that serves to house the so-called radium head and to establish a link between the latter and the ulna.
The " tuberosity of the ulna ". Located below the coronoid process, it is the bony prominence that houses the terminal head of the brachial muscle.

Brief review of the proximal-distal terms

" Proximal " means "closer to the center of the body" or "closer to the point of origin"; " distal ", instead, means "farther from the center of the body" or "farther from the point of origin.

Examples:

The femur is proximal to the tibia, which is distal to the femur.
In the femur, the extremity bordering the trunk is the proximal end, while the extremity bordering the knee is the distal end.

BODY OF THE ULNA

The body (or diaphysis) of the ulna is the portion of ulna interposed between the proximal epiphysis and the distal epiphysis.

On the body of the ulna, the following anatomical elements stand out:

The front surface (or fly ) and the back surface (or dorsal ). They are areas of departure and arrival for different muscles of the forearm and of the hand (eg: anconeus, deep flexor of the fingers, supinator, long abductor of the thumb, extensor of the thumb, extensor of the index, etc.).
Furthermore, at the level of the anterior surface, the nutritive hole of the ulna also takes place (it is the channel that allows the entry of the blood vessels deputed to oxygenate and nourish the bone of the ulna).
The interosseous border . It is the portion of ulna destined to hook the so-called radio-ulnar interosseous membrane. The radio-ulnar interosseous membrane is a thin sheet of fibrous tissue which, interposed between ulna and radium, indirectly unites the aforementioned bones.

Did you know that ...

Between ulna and radium, the ulna corresponds to the fibula in the lower limb.

DISTAL EPIPHIST OF THE ULNA

The distal epiphysis of the ulna is the end of the ulna closest to the wrist and furthest from the humerus.

Its anatomical importance depends above all on its indirect contribution to the wrist joint.

To distinguish the morphology of the distal epiphysis of the ulna are in particular:

The " head of the ulna ". Rounded in shape, it is the small protuberance destined to fit into the so-called ulnar hollow of the radio (whose description will take place in the section dedicated to the radio).
The " styloid process ". Located on the inferior margin of the distal epiphysis of the ulna, in a medial position, it is the bone projection on which one of the two ends of the collateral ulnar carpal ligament finds insertion; the ulnar collateral ligament of the carpus is an important ligament of the wrist joint, which basically serves to stabilize the latter.

Radio

Between the ulna and the radius, the radius is the lateral bone of the forearm (always with the assumption that the upper limb is extended along the body and the palm of the hand is facing the observer).

Curiosity

In the sense in which the term "arm" includes the anatomical tract between the shoulder and the wrist (and not, as in reality it would be more correct, the anatomical portion between the shoulder and the elbow), humerus, ulna and radium are defined, as a whole, with the expression " bones of the arm ".

PROXIMAL EPIXIS OF THE RADIO

Similar to a cylinder, the proximal radius epiphysis is the end of the radius closest to the humerus.

As in the case of the proximal epiphysis of the ulna, its anatomical importance is connected to its participation in the elbow joint.

To characterize the morphology of the proximal radium epiphysis are:

The " head ". Representing the upper apex of the radius, it is the portion of bone with a smooth surface, which, through the interaction with the cartilage region of the humerus called capitulum, forms the articulation of the elbow.
In addition to this, it is important to point out that, on the medial border of the radium head, there is the connection area with the radial recess of the ulna (radial recess of the ulna which serves to constrain the latter to the radio in the proximal area ).
The " radial tuberosity ". Facing the ulna, it is a bone process that serves to accommodate the terminal head of the biceps brachial muscle.

Did you know that ...

Between the ulna and the radius, the radius corresponds, along the lower argon, to the tibia .

BODY OF THE RADIO

The body of the radium is the portion of radium located between the proximal epiphysis and the distal epiphysis.

With the tendency to widen in the proximal-distal sense, the body of the radium stands out for the following anatomical elements:

The " fly surface ". It is the area from which the hand muscle known as the long flexor of the thumb originates; the area that houses the terminal head of the pronator squared muscle; which inserts into the radio-carpal ligament fly; finally, the area on which the nutritive hole of the radium takes place (equally at the nutritive hole of the ulna, is the channel that allows the entry of the blood vessels delegated to oxygenate and nourish the bone tissue).
The " dorsal surface ". It is the area from which the thumb muscles called the long abductor of the thumb and the extensor of the thumb originate.
The " side surface ". It is the area on which the muscles of the forearm called supinator and pronator round are inserted.
The " bordino interosseo " (or " interossea crest "). It is equivalent to the interosseous border of the ulna, therefore it serves to hook the other end of the radio-ulnar interosseous membrane, consolidating the ulna-radio relationship.

DISTAL EPIFYTS OF THE RADIO

The distal radius epiphysis is the end of the radius closest to the wrist and furthest from the humerus.

It is anatomically important, because, taking contact with the bones of the carpus (which are nothing more than the bones of the wrist ), it actively participates in the formation of the wrist joint.

To distinguish the morphology of the distal epiphysis of the radius are above all:

The " styloid process ". It is a bone projection located in the lateral position, on which the terminal head of the brachioradial muscle and one of the two ends of the collateral radial ligament of the wrist find insertion.
The so-called ulnar hollow . It is the concavity in which the lateral surface of the ulna's head lodges perfectly. This ulna-radio contact in the distal area is added to the ulna-radio union in the proximal area, which has already been discussed on two occasions, and to the ulna-radio interaction deriving from the radio-ulnar interosseous membrane.
The " lateral articular facet " and the " medial articular facet ". The areas responsible for connecting the radius to the carpal bones are therefore the parts of the wrist.
More specifically, the lateral articular facet is the junction point with the carpal bone called scaphoid, while the medial articular facet is the junction point with the carpal bone called semilunar.

"Carpal bones", "wrist bones", "carpal bones" and "carpus" are synonymous.

Ossification

Several ossification centers contribute to the definitive formation of ulna and radius.

To be precise, the ulna is the result of the activity of 3 ossification centers, one of which resides on the body, one on the proximal epiphysis and one on the distal epiphysis; the radius, on the other hand, is the result of the activity of 4 ossification centers, which take place one on the body, two on the proximal epiphysis and one on the distal epiphysis.

Function

Ulna and radio cover essentially two functions .

A first function of ulna and radius is to form the elbow (through contact with the humerus) and the wrist (through contact with the bones of the carpus).

Elbow and wrist are two joints essential to the execution of numerous movements and gestures of the upper limb, including, for example, the throwing or hilt of objects, writing and lifting weights.

The other function of ulna and radio is to receive the muscles and ligaments of the upper limb necessary for the correct functioning of the joints just mentioned.

Without the muscles and ligaments that originate or end on ulna and radium, the movements of the elbow and wrist would be impossible.

diseases

Like practically all the other bones of the human body, even ulna and radium can be subjected to fracture as a result of relevant trauma.

Generally, ulna and radios fracture independently, in the sense that either the ulna is broken or the radium is broken; however, in rare (and very unfortunate) cases, they can both break .

Ulna fracture: the types

On the ulna, the most frequent fracture site is the body, followed, in order, by the olecranon (proximal end) and the distal end.

Fracture of the Radio: the types

Radium can be the victim of 4 different types of fractures, which are called: Colles fracture, radial head fracture, Smith's fracture and Barton's fracture .

Fractures of Ulna and Radio: the types

The simultaneous rupture of ulna and radius is the result of particular traumas, in which the force of impact is transmitted from bone to bone, through the interosseous membrane.