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Jai Ganesh

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Ulna (Bone)

Ulna (Bone)

Gist

The ulna is the longer, larger medial bone of the forearm, running parallel to the radius from the elbow to the wrist. It acts as a stable hinge for the elbow via the olecranon process and facilitates forearm rotation. It is essential for elbow stability, forearm rotation (pronation/supination), and serves as a major site for muscle attachment.

What is the ulna? The ulna is the longer of the two bones in your forearm. It helps you move your arm, wrist and hand. Your ulna also supports lots of important muscles, tendons, ligaments and blood vessels.

Summary

The ulna or ulnar bone (pl.: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the radius, the forearm's other long bone. Longer and thinner than the radius, the ulna is considered to be the smaller long bone of the lower arm. The corresponding bone in the lower leg is the fibula.

Structure

The ulna is a long bone found in the forearm that stretches from the elbow to the wrist, and when in standard anatomical position, is found on the medial side of the forearm. It is broader close to the elbow, and narrows as it approaches the wrist.

Close to the elbow, the ulna has a bony process, the olecranon process, a hook-like structure that fits into the olecranon fossa of the humerus. This prevents hyperextension and forms a hinge joint with the trochlea of the humerus. There is also a radial notch for the head of the radius, and the ulnar tuberosity to which muscles attach.

Close to the wrist, the ulna has a styloid process.

Details:

Description

The ulna is one of two bones that make up the forearm, the other being the radius. It forms the elbow joint with the humerus and also articulates with the radius both proximally and distally. It is located in the medial forearm when the arm is in the anatomical position. It is the larger of the two forearm bones. Ulna assists in pronation and supination of the forearm and hand.

Structure

The ulna is a long bone larger proximally than distally.

Proximal ulna

The proximal ulna is hook-like in form which articulates with the trochlea of the humerus to create the hinge joint of the Elbow.

The articulation is formed of the olecranon and the coronoid process.

Olecranon

This is a large, curved bony prominence which is accepted into the olecranon fossa, located on the humerus, during elbow extension.

The olecranon forms the upper part of the semi-lunar notch which is a smooth, large depression and articulates with the humeral trochlea during elbow flexion and extension.

Coronoid process

The coronoid process is a horizontal, bony projection which attaches directly onto the ulnar shaft. It is received into the coronoid fossa of the humerus in elbow flexion. The coronoid process also forms the lower part of the semi-lunar notch.

On the lateral side of the coronoid process is the radial notch where the head of the radius sits.

Head of the ulna

The lateral, distal end of the ulna is the head of the ulna. It articulates with the ulnar notch on the radius and with the triangular articular disc in the Wrist Joint.

Shaft of the Ulna

The shaft of ulna is triangular in shape and it consists of three borders and three surfaces. It's width is decreased as it moves towards distal end.

The three surfaces are:

* Anterior surface
* Posterior Surface
* Medial Surface

The three borders are:

* Interosseous Border
* Anterior Border
* Posterior Border

Distal End

The head of Ulna has convex articular surface on its lateral side in order to articulate with ulnar notch of radius. It forms the distal radio-ulnar joint.

The styloid process has attachment of ulnar collateral ligament.

Articulations:

Elbow

The ulna articulates with the humerus at its most proximal point forming the elbow in a hinge joint. It is the trochlea of the humerus which sits in the semi-lunar notch of the ulna to form this joint.

Radio-ulnar joints

The ulna articulates with the radius proximally and distally to produce pronation (from the proximal joint) and supination (from the distal joint) of the forearm.

The ulna also articulates with the radius in a syndesmosis joint via its interosseous membrane. Which runs the length of the shaft of the ulna from the radial notch proximally to the head of the ulna. This also acts to compartmentalise dorsal and volar sides of the forearm.

Muscle attachments:

Olecranon process

Triceps - inserts onto the posterior of the olecranon process.

Anconeus - inserts onto lateral aspect

Flexor Carpi Ulnaris - origin:posterior, also shares an origin from humeral medial epicondyle

Coronoid process

Brachialis - inserts to anterior, inferior coronoid process

Pronator teres - originates medial surface, also from humeral medial epicondyle

Flexor Digitorum Superficialis - originates medial surface, also from humeral medial epicondyle

Shaft of ulna

All of the following arise from the shaft of the ulna:

Flexor Digitorum Profundus

Pronator quadratus

Extensor carpi ulnaris - also shared with lateral epicondyle of humerus

Abductor pollicis longus - also originates from interosseous membrane

Extensor Pollicis Longus - also originates from interosseous membrane

Extensor indicis - also originates from interosseous membrane

Clinical relevance

Like any other joint in the body the ulna can be affected by osteoarthritis in the elbow joint.

Ulnar fractures

Typically occur as a result of fragility and normally following a fall such as a fall on an outstretched hand (FOOSH)

Monteggia fracture - fracture of the proximal 1/3 of the ulnar shaft accompanied by the dislocation of the radial head.
Hume fracture - fracture of the olecranon accompanied by anterior dislocation of the radial head.
Galezzi's fracture - fracture to the distal radius accompanied by ulnar head dislocation at distal radio-ulna joint.

Additional Information

The ulna is one of the bones in your forearm. It helps you move your arm, wrist and hand. If osteoporosis weakens your bones, you have an increased risk for fractures you might not even know about. Talk to a healthcare provider about a bone density test.

Overview:

The ulna is the longer of the two bones in your forearm.

What is the ulna?

The ulna is the longer of the two bones in your forearm. It helps you move your arm, wrist and hand. Your ulna also supports lots of important muscles, tendons, ligaments and blood vessels.

If you experience a fractured (broken) ulna, you might need surgery to repair your bone and physical therapy to help you regain your strength and ability to move.

Your ulna — like all bones — can be affected by osteoporosis.

Because your ulna is connected to so many muscles and nerves, injuries to one can often affect the others.

Function:

What does the ulna do?

Your ulna has several important jobs, including:

* Helping your forearm and wrist move, flex and rotate.
* Holding more than a dozen muscles in place.
* Stabilizing the rest of your arm, wrist and hand.
* Helping your elbow and wrist move.

Anatomy:

Where is the ulna located?

The ulna is one of two bones in your forearm. The other is your radius. The ulna is on the medial (pinkie) side of your forearm.

What does the ulna look like?

The ulna has a notched end where it meets your humerus (upper arm bone), a long shaft in the middle that’s slightly curved and a narrow end that meets your wrist. It’s slightly longer than the radius.

Even though it’s one long bone, your ulna is made up of several parts. These include:

Ulna proximal aspect

The upper (proximal) end of your ulna connects to your humerus. It forms the bony point of your elbow. The ulna’s proximal end (aspect) contains the:

* Olecranon.
* Trochlear notch.
* Coronoid process.
* Radial notch.
* Ulnar tuberosity.

Ulna shaft

The shaft is the long middle portion of the ulna that supports the weight of your forearm and gives it its shape.

Ulna distal aspect

The lower (distal) end of your ulna forms part of your wrist joint. It ends in a rounded bump called the styloid process — the bump above your wrist on your pinkie side. The distal end is sometimes referred to as the head of your ulna.

Your healthcare provider may use all these parts and labels as they describe where you’re having pain or issues. If you ever break your ulna (an ulnar fracture), your provider might use some of these terms to describe where your bone was damaged.

How big is the ulna?

The ulna is the second longest bone in your arm. It’s one of the longest bones in your body. Most adults’ ulna bones are around 11 inches (in.) long.

Conditions and Disorders:

What are the common conditions and disorders that affect the ulna?

The most common issues that affect the ulna are fractures, osteoporosis and damage to the ulnar nerve. Common conditions include:

* Osteoarthritis.
* Ulnar wrist pain.
* Ulnar nerve entrapment.

Ulna fractures

A bone fracture is the medical term for a broken bone. The most common causes of ulna fractures include:

* Sports injuries.
* Fall.
* Car accidents.

Symptoms of a fracture include:

* Pain.
* Swelling.
* Tenderness.
* Inability to move your arm like you usually can.
* Bruising or discoloration.
* A deformity or bump that’s not usually on your body.

Go to the emergency room right away if you’ve experienced trauma or think you have a fracture.

Osteoporosis

Osteoporosis weakens bones, making them more susceptible to sudden and unexpected fractures. It usually doesn’t cause any symptoms you can notice, so many people don’t know they have osteoporosis until after it causes them to break a bone.

Females and adults older than 65 have an increased risk for developing osteoporosis. Talk to your provider about a bone density test that can catch osteoporosis before it causes a fracture.

What tests are done on the ulna?

The most common test done to check the health of your ulna is a bone density test. It’s sometimes called a DEXA or DXA scan. A bone density test uses low levels of X-rays to measure how strong your bones are. It’s a way for your provider to track bone loss as you age.

If you’ve experienced a humeral fracture, your provider or surgeon might need imaging tests, including:

* X-rays.
* Magnetic Resonance Imaging (MRI).
* CT scan.

What are common treatments for the ulna?

Usually, your ulna won’t need treatment unless you’ve experienced a fracture or other injury to your arm. You might need treatment if you’ve been diagnosed with osteoporosis.

Ulna fracture treatment

How your fracture is treated depends on which type it is and what caused it. You’ll need some form of immobilization like a splint or cast. You might need surgery to realign (set) your bone to its correct position so it can heal.

Osteoporosis treatment

Treatments for osteoporosis can include exercise, vitamin and mineral supplements and medications.

Your provider will help you develop a treatment plan that’s customized for you and your bone health.

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