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Radius (bone)
Radius (bone)
Radius (bone)
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Radius
The radius (shown in red) is a bone in the forearm.
Details
Identifiers
Latinradius
MeSHD011884
TA98A02.4.05.001
TA21210
FMA23463
Anatomical terms of bone

The radius or radial bone (pl.: radii or radiuses) is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is longer than the radius, but the radius is thicker. The radius is a long bone, prism-shaped and slightly curved longitudinally.

The radius is part of three joints: the elbow and the wrist, both of which are synovial joints; and the radioulnar joint, which is a syndesmosis. At the elbow, it joins with the capitulum of the humerus, and in a separate region, with the ulna at the radial notch. At the wrist, the radius forms a joint with the ulna bone. The radioulnar joint allows for supination and pronation of the forearm.

The corresponding bone in the leg is the tibia.[citation needed]

Structure

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3D model.
Full anterior view of right radius
Full posterior view of right radius
Full medial view of right radius
Full lateral view of right radius

The long narrow medullary cavity is enclosed in a strong wall of compact bone. It is thickest along the interosseous border and thinnest at the extremities, same over the cup-shaped articular surface (fovea) of the head.

The trabeculae of the spongy tissue are somewhat arched at the upper end and pass upward from the compact layer of the shaft to the fovea capituli (the humerus's cup-shaped articulatory notch); they are crossed by others parallel to the surface of the fovea. The arrangement at the lower end is somewhat similar. It is missing in radial aplasia.

The radius has a body and two extremities. The upper extremity of the radius consists of a somewhat cylindrical head articulating with the ulna and the humerus, a neck, and a radial tuberosity.[1] The body of the radius is self-explanatory, and the lower extremity of the radius is roughly quadrilateral in shape, with articular surfaces for the ulna, scaphoid and lunate bones. The distal end of the radius forms two palpable points, radially the styloid process and Lister's tubercle on the ulnar side. Along with the proximal and distal radioulnar articulations, an interosseous membrane originates medially along the length of the body of the radius to attach the radius to the ulna.[2]

Anterior and posterior view of radius bone - labelled.

Near the wrist

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The distal end of the radius is large and of quadrilateral form.

Joint surfaces

It is provided with two articular surfaces – one below, for the carpus, and another at the medial side, for the ulna.

  • The carpal articular surface is triangular, concave, smooth, and divided by a slight antero-posterior ridge into two parts. Of these, the lateral, triangular, articulates with the scaphoid bone; the medial, quadrilateral, with the lunate bone.
  • The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is narrow, concave, smooth, and articulates with the head of the ulna.

These two articular surfaces are separated by a prominent ridge, to which the base of the triangular articular disk is attached; this disk separates the wrist-joint from the distal radioulnar articulation.

Other surfaces

This end of the bone has three non-articular surfaces – volar, dorsal, and lateral.

Body

[edit]

The body of the radius (or shaft of radius) is prismoid in form, narrower above than below, and slightly curved, so as to be convex lateralward. It presents three borders and three surfaces.

Borders

The volar border (margo volaris; anterior border; palmar;) extends from the lower part of the tuberosity above to the anterior part of the base of the styloid process below, and separates the volar from the lateral surface. Its upper third is prominent, and from its oblique direction has received the name of the oblique line of the radius; it gives origin to the flexor digitorum superficialis muscle (also flexor digitorum sublimis) and flexor pollicis longus muscle; the surface above the line gives insertion to part of the supinator muscle. The middle third of the volar border is indistinct and rounded. The lower fourth is prominent, and gives insertion to the pronator quadratus muscle, and attachment to the dorsal carpal ligament; it ends in a small tubercle, into which the tendon of the brachioradialis muscle is inserted.

The dorsal border (margo dorsalis; posterior border) begins above at the back of the neck, and ends below at the posterior part of the base of the styloid process; it separates the posterior from the lateral surface. is indistinct above and below, but well-marked in the middle third of the bone.

The interosseous border (internal border; crista interossea; interosseous crest;) begins above, at the back part of the tuberosity, and its upper part is rounded and indistinct; it becomes sharp and prominent as it descends, and at its lower part divides into two ridges which are continued to the anterior and posterior margins of the ulnar notch. To the posterior of the two ridges the lower part of the interosseous membrane is attached, while the triangular surface between the ridges gives insertion to part of the pronator quadratus muscle. This crest separates the volar from the dorsal surface, and gives attachment to the interosseous membrane. The connection between the two bones is actually a joint referred to as a syndesmosis joint.

Surfaces

The volar surface (facies volaris; anterior surface) is concave in its upper three-fourths, and gives origin to the flexor pollicis longus muscle; it is broad and flat in its lower fourth, and affords insertion to the Pronator quadratus. A prominent ridge limits the insertion of the Pronator quadratus below, and between this and the inferior border is a triangular rough surface for the attachment of the volar radiocarpal ligament. At the junction of the upper and middle thirds of the volar surface is the nutrient foramen, which is directed obliquely upward.

The dorsal surface (facies dorsalis; posterior surface) is convex, and smooth in the upper third of its extent, and covered by the Supinator. Its middle third is broad, slightly concave, and gives origin to the Abductor pollicis longus above, and the extensor pollicis brevis muscle below. Its lower third is broad, convex, and covered by the tendons of the muscles which subsequently run in the grooves on the lower end of the bone.

The lateral surface (facies lateralis; external surface) is convex throughout its entire extent and is known as the convexity of the radius, curving outwards to be convex at the side. Its upper third gives insertion to the supinator muscle. About its center is a rough ridge, for the insertion of the pronator teres muscle.[3] Its lower part is narrow, and covered by the tendons of the abductor pollicis longus muscle and extensor pollicis brevis muscle.

Near the elbow

[edit]

The upper extremity of the radius (or proximal extremity) presents a head, neck, and tuberosity.

  • The radial head has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum (or capitellum) of the humerus. The circumference of the head is smooth; it is broad medially where it articulates with the radial notch of the ulna, narrow in the rest of its extent, which is embraced by the annular ligament. The deepest point in the fovea is not axi-symmetric with the long axis of the radius, creating a cam effect during pronation and supination.
  • The head is supported on a round, smooth, and constricted portion called the neck, on the back of which is a slight ridge for the insertion of part of the supinator muscle.
  • Beneath the neck, on the medial side, is an eminence, the radial tuberosity; its surface is divided into a posterior, rough portion, for the insertion of the tendon of the biceps brachii muscle, and an anterior, smooth portion, on which a bursa is interposed between the tendon and the bone.

Development

[edit]

The radius is ossified from three centers: one for the body, and one for each extremity. That for the body makes its appearance near the center of the bone, during the eighth week of fetal life.

Ossification commences in the lower end between 9 and 26 months of age.[citation needed] The ossification center for the upper end appears by the fifth year.

The upper epiphysis fuses with the body at the age of seventeen or eighteen years, the lower about the age of twenty.

An additional center sometimes found in the radial tuberosity, appears about the fourteenth or fifteenth year.

Function

[edit]

Muscle attachments

[edit]

The biceps muscle inserts on the radial tuberosity of the upper extremity of the bone. The upper third of the body of the bone attaches to the supinator, the flexor digitorum superficialis, and the flexor pollicis longus muscles. The middle third of the body attaches to the extensor ossis metacarpi pollicis, extensor primi internodii pollicis, and the pronator teres muscles. The lower quarter of the body attaches to the pronator quadratus muscle and the tendon of the brachioradialis.

Clinical significance

[edit]

Radial aplasia refers to the congenital absence or shortness of the radius.

Fracture

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A subtle radial head fracture with associated positive sail sign

Specific fracture types of the radius include:

  • Proximal radius fracture. A fracture within the capsule of the elbow joint results in the fat pad sign or "sail sign" which is a displacement of the fat pad at the elbow.
Illustration showing radius shaft fracture

History

[edit]

The word radius is Latin for "ray". In the context of the radius bone, a ray can be thought of rotating around an axis line extending diagonally[clarification needed] from center of capitulum to the center of distal ulna. While the ulna is the major contributor to the elbow joint, the radius primarily contributes to the wrist joint.[5]

The radius is named so because the radius (bone) acts like the radius (of a circle). It rotates around the ulna and the far end (where it joins to the bones of the hand), known as the styloid process of the radius, is[clarification needed] the distance from the ulna (center of the circle) to the edge of the radius (the circle). The ulna acts as the center point to the circle because when the arm is rotated the ulna does not move.

Other animals

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In four-legged animals, the radius is the main load-bearing bone of the lower forelimb. Its structure is similar in most terrestrial tetrapods, but it may be fused with the ulna in some mammals (such as horses) and reduced or modified in animals with flippers or vestigial forelimbs.[6]

[edit]
  • Radius bone and radius of a circle comparison.
    Radius bone and radius of a circle comparison.
  • Position of radius (shown in red).
    Position of radius (shown in red).
  • Radius, styloid process - anterior view
    Radius, styloid process - anterior view
  • Radius, ulnar notch - posterior view
    Radius, ulnar notch - posterior view
  • Radius, radial head – posterior view
    Radius, radial head – posterior view
  • Radius, radial head – anterior view
    Radius, radial head – anterior view
  • Radius l. dx. – ant. view
    Radius l. dx. – ant. view
  • Radius l. dx. – post. view
    Radius l. dx. – post. view
  • Anterior surface of radius (at right)
    Anterior surface of radius (at right)
  • Posterior surface of radius (at left)
    Posterior surface of radius (at left)
  • Posterior view of right proximal radius
    Posterior view of right proximal radius
  • Posterior view of right distal radius
    Posterior view of right distal radius
  • Medial view of right proximal radius
    Medial view of right proximal radius
  • Medial view of right distal radius
    Medial view of right distal radius
  • Lateral view of right distal radius
    Lateral view of right distal radius
  • Anterior view of right distal radius
    Anterior view of right distal radius
  • Anterior view of right proximal radius
    Anterior view of right proximal radius
  • Radius bone anatomy

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Radius (bone)

View on Grokipedia
from Grokipedia
The radius is one of the two long bones of the human forearm, positioned laterally (on the side) and parallel to the , forming the structural framework of the antebrachium. It is a prismoid-shaped characterized by three borders (anterior, posterior, and interosseous), three surfaces (anterior, posterior, and lateral), a proximal end featuring the fovea and radial tuberosity, a triangular shaft, and a distal end with the styloid process and articular facets for the . The radius develops from the through . Functionally, the radius enables essential movements of the upper limb, including pronation and supination of the forearm (allowing up to 180 degrees of rotation via its articulations with the ulna), flexion and extension at the elbow joint with the humerus, and a range of motions at the wrist such as flexion, extension, abduction, adduction, and circumduction through the radiocarpal joint. It articulates proximally with the capitulum of the humerus and the radial notch of the ulna to form the humeroradial and proximal radioulnar joints, respectively, and distally with the ulnar head, carpal bones (scaphoid, lunate, and triquetrum), and via a triangular fibrocartilage complex that stabilizes the joint. Blood supply to the radius is primarily from the anterior and posterior interosseous arteries branching from the common interosseous artery, with nutrient arteries entering the bone at mid-shaft, supporting its role in load-bearing and mobility. Notable aspects of the radius include physiologic variants, such as variations in the radial tuberosity, which can influence surgical interventions for fractures—a common injury due to its exposed position and role in falls. The bone's lateral convexity and connection with the create a syndesmotic stability that distributes forces across the , making it vital for hand dexterity and overall function.

Gross anatomy

Proximal end

The proximal end of the consists of the radial head, , and tuberosity, which facilitate articulations at the and proximal radioulnar . The radial head is a disc-shaped or cylindrical structure covered in , with an average diameter of 20-25 mm in adults. Its superior aspect features a concave articular fovea that articulates with the to form part of the . The peripheral provides a convex articular surface that fits into the radial notch of the , forming the proximal radioulnar ; this is encircled and stabilized by the annular ligament. Distal to the head lies the radial neck, a narrow constriction that connects the head to the shaft and serves as an attachment site for ligaments stabilizing the . Due to its slender morphology, the radial neck is particularly prone to fractures, often resulting from falls on an outstretched hand. The radial tuberosity is an oval, roughened eminence located on the anteromedial aspect just distal to the , providing the primary insertion site for the biceps brachii . This tuberosity's position enhances the mechanical advantage of the in supination and elbow flexion.

Shaft

The shaft of the radius constitutes the elongated midportion of the bone, presenting a prismoid configuration with a triangular cross-section that broadens progressively toward the distal end. This structure features three principal borders: an anterior (volar) border, a posterior (dorsal) border, and an interosseous border along the medial aspect. The interosseous border forms a sharp ridge that serves as the primary attachment site for the , linking the radius to the adjacent for structural stability in the . The radius shaft possesses three corresponding surfaces: anterior, posterior, and lateral. The anterior surface, situated between the anterior and interosseous borders, is predominantly smooth, facilitating the passage of flexor tendons from the musculature. The posterior surface, bounded by the posterior and interosseous borders, includes a prominent oblique ridge or line in its middle third, providing attachment points for origins of extensor muscles. The lateral surface, convex and relatively narrow, lies between the anterior and posterior borders and accommodates origins for muscles such as the abductor pollicis longus in its distal portion. Additionally, the shaft exhibits a gentle lateral convexity along its length, enhancing its supportive geometry. A key feature on the anterior surface is the nutrient foramen, typically located at the junction of the upper and middle thirds, which permits entry of the into the . The average length of the adult , encompassing the shaft as its primary component, measures 22-25 cm, varying slightly by sex and population. Blood supply to the shaft derives mainly from the , a branch of the anterior interosseous , which penetrates the cortex via the nutrient foramen near the mid-shaft level to nourish the diaphyseal bone tissue. This vascular entry supports the overall integrity of the mid-forearm structure. The shaft transitions smoothly from the proximal radial tuberosity and flares in width toward the distal region.

Distal end

The distal end of the radius is markedly expanded compared to the shaft, forming a widened, rectangular structure that supports the and measures approximately twice the width of the proximal end. This expansion includes a biconcave articular surface with a normal volar tilt of 10-15 degrees relative to the long axis of the bone, facilitating proper load distribution across the carpus, and a radial inclination of 20-25 degrees, which aligns the for thumb-side stability. The medial aspect of the distal radius features the ulnar notch, also known as the sigmoid notch, a smooth, crescent-shaped concave facet that articulates with the head of the to form the distal radioulnar , allowing pronation and supination of the forearm. Laterally and distally, the carpal articular surface is divided into two distinct fossae: the scaphoid fossa, which is concave and narrower, articulating with the , and the lunate fossa, which is concave and broader, articulating with the lunate bone to compose the radiocarpal . The dorsal and palmar rims bordering these fossae serve as key attachment sites for the triangular fibrocartilage complex (TFCC), a ligamentous structure that enhances stability and transmits ulnar-sided forces. Projecting laterally from the distal radius is the styloid process, a conical bony prominence approximately 10-12 mm in length that extends beyond the articular surface and provides insertion for the of the muscle as well as attachments for the extensor carpi radialis longus and brevis tendons and the radial collateral ligament of the . On the dorsal surface, roughly 1 cm proximal to the articular margin, lies , a low, rounded ridge that forms a shallow groove directing the of the extensor pollicis longus, thereby organizing the extensor compartment of the and preventing during movement.

Microscopic anatomy and development

Histology

The histology of the radius bone reveals a microscopic dominated by cortical and cancellous tissues, along with surrounding membranes that support structural integrity and cellular activity. Cortical bone forms the dense outer layer, particularly prominent in the shaft, where it consists of organized or . Each features a central surrounded by concentric lamellae of mineralized matrix, providing high mechanical strength through its compact arrangement. interconnect these , facilitating the passage of blood vessels and nerves from the to nourish the tissue. This cortical structure exhibits greater density in the shaft compared to the proximal and distal ends, reflecting adaptations to torsional loads in the , with an average porosity of 5-10% in adults. In contrast, the epiphyses contain cancellous bone, characterized by a porous trabecular network of interconnected rods and plates that enhance compressive resistance. These trabeculae are anisotropically oriented along principal stress trajectories, optimizing load distribution within the spongy interior. The surrounding , a thin membrane enveloping the except at articular surfaces, comprises an outer fibrous layer rich in and an inner cambial layer with osteogenic cells capable of new bone formation. Sharpey's fibers from the fibrous layer penetrate the cortical bone, firmly anchoring the periosteum to the underlying matrix. Lining the medullary cavity and trabecular spaces is the endosteum, a delicate layer containing osteoblasts for bone deposition, osteoclasts for resorption, and quiescent osteocytes embedded in lacunae. These cells, along with osteoprogenitor populations, drive continuous remodeling to maintain calcium homeostasis and repair microdamage. In the radius, this remodeling is influenced by its role in forearm rotation, though the core histological elements align with those of other long bones.

Ossification

The ossification of the radius bone follows the typical endochondral pattern for long bones, beginning with the formation of a primary in the during embryonic development. This center emerges from mesenchymal tissue around the 8th intrauterine week, where a model is gradually replaced by bone through the process of chondrification followed by and vascular invasion. Secondary ossification centers develop later at the epiphyses, contributing to the longitudinal growth of the bone. The distal epiphyseal center appears between 1 and 2 years of age, while the proximal epiphyseal center forms at 5 to 6 years. In total, three ossification centers are involved in radial development: the diaphyseal primary center and the proximal and distal epiphyseal secondary centers. These timelines occur earlier in females compared to males, reflecting general in skeletal maturation. Fusion of these centers completes the skeletal maturity of the radius. The proximal epiphysis fuses with the shaft between 16 and 18 years, and the distal epiphysis fuses between 17 and 19 years, with females typically achieving fusion earlier than males. Longitudinal growth occurs at the physeal growth plates between the epiphyses and diaphysis, characterized by zones of cellular activity. The hypertrophic zone features enlarged chondrocytes that secrete matrix components, followed by a calcification zone where the cartilage matrix mineralizes, providing a scaffold for metaphyseal bone formation. These growth plates are particularly vulnerable to injury due to their relatively weak structure in the hypertrophic and calcified regions. Disruptions in this process can lead to developmental anomalies. For instance, Madelung deformity arises from partial growth arrest at the distal radial , often due to abnormal of the ulnar volar aspect, resulting in volar and ulnar tilting of the distal . On average, the distal growth plate contributes approximately 75% to the adult length of the , while the proximal plate accounts for about 25%, underscoring the greater impact of distal physeal disturbances.

Biomechanics and function

Joint articulations and movements

The proximal radioulnar joint is a pivot synovial joint formed by the articulation of the circumferential radial head with the radial notch of the , enabling forearm rotation through pronation and supination. Pronation allows approximately 80 degrees of motion, turning the palm posteriorly, while supination permits about 90 degrees, positioning the palm anteriorly. The annular encircles the radial head, maintaining its stability within the ulnar notch during these rotational movements and preventing . The distal radioulnar joint similarly functions as a pivot, where the ulnar head articulates with the ulnar notch of the distal radius, contributing to the same pronation-supination arc as the proximal joint for coordinated . Stability here is primarily provided by the complex (TFCC), which anchors the ulnar head to the radius and sigmoid notch, absorbing compressive forces and limiting excessive translation. The TFCC's dorsal and palmar radioulnar ligaments further constrain axial migration during . At the wrist, the radiocarpal is a synovial condyloid articulation between the distal radius and the proximal row of (scaphoid, lunate, and triquetrum), permitting hinge-like flexion and extension alongside abduction (radial deviation) and adduction (ulnar deviation). Flexion ranges from 70 to 80 degrees, extension about 70 degrees, radial deviation 20 degrees, and ulnar deviation 30 degrees, facilitating hand positioning for and manipulation. Radial and ulnar collateral ligaments reinforce this against varus and valgus stresses, while the between the radius and ulna distributes axial loads proximally from the . Biomechanically, the radius rotates around the fixed ulnar axis during pronation and supination, with the two bones maintaining longitudinal alignment via the , which transfers up to 50% of compressive forces from the radius to the under axial loading. In the , load distribution typically directs approximately 80% through the radius and 20% via the ulnar-sided TFCC, varying with position and ulnar variance to optimize stability and minimize stress concentrations.

Muscle attachments

The proximal end of the radius features the radial tuberosity, a key site for muscle insertion that facilitates supination and flexion. The brachii inserts directly onto the smooth anterior aspect of the radial tuberosity, generating a force vector that produces approximately 4 times greater supination when the is pronated compared to neutral positions, contributing to overall supination strength up to around 16 Nm during maximal effort. Along the shaft of the radius, several muscles attach to enable rotational and stabilizing movements of the forearm. The supinator muscle originates from the lateral epicondyle of the humerus and the supinator crest of the ulna, inserting onto the lateral, posterior, and anterior surfaces of the proximal third of the radius; this attachment allows the muscle to wrap around the radial head, producing supination torque that peaks at about 16.2 Nm when the forearm is in a moderately pronated position (75% prone). The pronator teres inserts on the lateral mid-shaft of the radius after originating from the medial epicondyle of the humerus and coronoid process of the ulna, exerting a pronatory force that is most efficient near the neutral forearm position. More distally on the shaft, the brachioradialis inserts at the styloid process of the radius, proximal to the wrist, aiding in elbow flexion across various forearm orientations while transmitting force to stabilize the distal radius. At the distal end of the radius, attachments support thumb movements and fine forearm rotation. The flexor pollicis longus originates from the anterior surface of the radius, spanning from below the radial tuberosity to the , enabling flexion of the thumb's interphalangeal joint through a tendon that passes through the . On the posterior aspect, the extensor pollicis brevis originates from the distal third of the radius's posterior surface and , extending the of the thumb. The extensor pollicis longus tendon, though originating primarily from the ulna, courses along the dorsal ridge of the distal radius, while the abductor pollicis longus originates from the posterior surfaces of the radius, ulna, and in the mid-forearm, abducting and extending the thumb at the . The pronator quadratus, originating from the distal anterior ulna, inserts across the distal anterior radius, providing fine pronation control and stability during subtle rotational adjustments of the . Tendon sheaths and grooves on the radius guide extensor tendons to optimize biomechanical efficiency. Notably, , a dorsal bony prominence on the distal radius, serves as a for the extensor pollicis in the third extensor compartment, directing it ulnar to the tubercle to facilitate smooth extension and prevent subluxation during motion.

Clinical aspects

Fractures and injuries

Distal radius fractures are among the most common upper extremity injuries, often occurring due to falls on an outstretched hand (FOOSH) leading to dorsal angulation of the distal fragment, as seen in Colles' fractures. Smith's fractures, conversely, involve volar angulation of the distal fragment and typically result from falls on a flexed hand or direct trauma to the dorsal . These fractures are classified using the AO system, which categorizes them into type A (extra-articular), type B (partial articular), and type C (complete articular) based on the involvement of the joint surface and . Proximal radius fractures, particularly of the radial head, frequently arise from axial loading or valgus stress to the , such as during a fall with the arm outstretched. The Mason classification is widely used for these injuries: type I involves undisplaced or minimally displaced fractures without mechanical block; type II features partial articular displacement greater than 2 mm; and type III consists of comminuted fractures involving the entire articular surface. Radius shaft fractures typically result from direct trauma, such as blows to the , or from repetitive stress in athletes, leading to transverse or oblique breaks in the . A specific variant is the , which combines a distal-third radius shaft fracture with or of the distal radioulnar joint (DRUJ), often caused by FOOSH with forearm pronation or direct impact. Complications of radius fractures include , which can develop from swelling and increased pressure in the compartments, potentially leading to neurovascular compromise if not addressed promptly, and , where the fracture fails to heal due to poor blood supply, infection, or excessive motion at the site. plays a critical role in and management; plain X-rays are the initial modality to assess alignment, displacement, and joint involvement, while computed tomography (CT) is recommended for evaluating intra-articular extension or complex . Acute management varies by fracture stability and location. Stable fractures, such as undisplaced Mason type I radial head fractures, are often treated with closed reduction and immobilization in a or splint to restore alignment without . Unstable or displaced fractures, including AO type C distal radius or Galeazzi variants, typically require open reduction and internal fixation (ORIF) using volar or dorsal plates to achieve anatomic reduction and stable fixation. External fixation is employed for highly comminuted or open fractures, providing provisional stabilization while allowing management. Functional outcomes are commonly assessed using the Disabilities of the Arm, Shoulder, and Hand () score, which evaluates upper extremity impairment, with studies showing improved scores in ORIF compared to external fixation for certain unstable distal fractures.

Pathologies and disorders

The radius is susceptible to various acquired pathologies and disorders, including inflammatory, degenerative, and vascular conditions that can impair its structure and function. These are explored in the following subsections.

Congenital Conditions

Radial club hand, also known as radial longitudinal deficiency, is a congenital malformation characterized by or absence of the radius bone, leading to radial deviation of the hand and shortening of the . This condition arises from failure of formation along the radial axis during embryonic development, often resulting in a clubbed appearance of the hand with limited radial motion. The incidence is 1 in 50,000 to 1 in 100,000 live births, with bilateral involvement in about 50% of cases. Madelung deformity is another congenital disorder involving abnormal growth arrest of the palmar-ulnar aspect of the distal radial , causing volar and ulnar tilting of the distal radius with dorsal prominence of the . This leads to a characteristic dorsal ulnar tilt, increased interosseous space, and progressive deformity, typically manifesting in late childhood or . The condition is more common in females and may be associated with genetic syndromes such as Leri-Weill dyschondrosteosis.

Degenerative Conditions

Kienböck's disease involves of the lunate bone, which secondarily affects the radius by disrupting the radiocarpal joint alignment and leading to carpal collapse. The lunate's necrosis causes fragmentation and sclerosis, resulting in abnormal load distribution across the distal radius and progressive pain with limited wrist extension. This condition predominantly affects young adults, particularly manual laborers, and can lead to secondary involving the radius if untreated. Osteoarthritis of the radiocarpal commonly involves the distal radius, characterized by degeneration, subchondral sclerosis, and formation at the articulation between the radius and proximal carpal row. This degenerative process often follows intra-articular distal radius or chronic , leading to , , and reduced . The condition progresses in stages, with advanced cases showing joint space narrowing and cystic changes in the radial articular surface.

Inflammatory Conditions

Rheumatoid arthritis frequently causes erosions at the distal radioulnar joint (DRUJ), where synovial inflammation leads to on the ulnar aspect of the distal radius and sigmoid notch. These marginal erosions, often visible on radiographs as "scalloping," result in joint instability, , and , affecting up to 75% of patients with longstanding disease. Gouty tophi, deposits of monosodium urate crystals, can form in the soft tissues and periarticular regions around the , particularly at the , leading to erosive with overhanging bone margins. In chronic cases, these tophi invade the distal radial , causing punched-out lytic lesions and destruction, exacerbated by recurrent .

Vascular Conditions

Avascular necrosis of the radial head often occurs post-trauma, such as after radial head fractures, due to disrupted blood supply from the anterior and posterior radial recurrent arteries. This leads to ischemia, collapse, and fragmentation, presenting with and limited supination, particularly in children where the condition is rare but can result from high-energy injuries. in the represents a vascular where increased intracompartmental compromises to the radial-sided muscles and neurovascular structures, potentially leading to radial involvement through secondary ischemia. Common after both-bone forearm fractures, it manifests with severe on passive stretch, paresthesia in the distribution, and requires urgent to prevent irreversible muscle and contractures affecting radial alignment.

Diagnosis and Treatment

(MRI) is essential for evaluating pathologies around the radius, such as ligamentous injuries, , or early avascular changes, providing superior contrast resolution compared to plain radiographs. It detects edema, defects, and tophaceous deposits with high sensitivity, aiding in the differentiation of inflammatory from degenerative processes. For severe involving the DRUJ, the Darrach procedure entails subperiosteal resection of the distal proximal to the sigmoid notch of the , relieving pain by eliminating the arthritic articulation while preserving radial stability. This salvage operation is indicated in low-demand patients with refractory symptoms, yielding good pain relief in over 80% of cases, though it risks proximal migration of the ulnar stump.

Comparative and historical aspects

In other animals

In quadrupedal mammals such as , the is elongated and often fused distally with the , forming a robust structure that supports during locomotion while limiting rotation to enhance stability. This fusion contrasts with more mobile configurations in other taxa, prioritizing load distribution over flexibility in cursorial species. Primates exhibit mobile proximal and distal radioulnar joints, enabling pronation and supination critical for grasping branches and manipulating objects during arboreal activities. In arboreal like , the often features an elongated styloid process that stabilizes the , facilitating suspensory postures and precise hand movements. In birds, the radius forms part of the elongated adapted for flight, remaining separate from the and articulating distally with the carpometacarpus, a fused structure of carpal and , which provides rigidity and reduces weight. Certain avian species possess a pneumatic invaded by , further lightening the while maintaining structural integrity for aerodynamic efficiency. Evolutionarily, the separation of the and in therapsids, early ancestors, allowed for independent via pronator muscles and ligaments, marking a key for enhanced versatility beyond the fused states in earlier synapsids. In bipedal taxa like certain theropod dinosaurs, altering to support upright posture and balancing evolutionary pressures for efficient limb proportions. Veterinarily, mid-shaft fractures of the radius are prevalent in dogs due to high-energy trauma, commonly managed through surgical plating such as minimally invasive plate osteosynthesis (MIPO), which preserves vascularity and promotes rapid union with fewer complications than traditional open reduction.

History and nomenclature

The term "radius" for the forearm bone originates from the Latin word radius, meaning "ray," "rod," or "spoke," reflecting its slender, rod-like shape and resemblance to the spoke of a wheel. This nomenclature also draws from ancient Greek associations with wheel spokes or rods, emphasizing the bone's linear form in the forearm. In antiquity, the radius was first systematically described by the Greek physician in the 2nd century AD as one of the two primary bones of the , analogous to a spoke supporting the arm's structure, based on his dissections of animal and human cadavers. Galen's accounts, preserved in works like On the Usefulness of the Parts of the Body, detailed its articulations with the and highlighted its role in movement, influencing anatomical thought for over a . During the , advanced the understanding of the radius through detailed illustrations in his seminal 1543 text De Humani Corporis Fabrica, which depicted the bone's full morphology, including its head, shaft, and styloid process, via precise woodcuts derived from human dissections. This work corrected earlier inaccuracies from and established the radius as a distinct, pivotal element in skeletal . In the 18th century, French surgeon Henri-Louis Duhamel du Monceau conducted pioneering experiments on bone ossification around 1739, using madder root staining in animals to demonstrate the periosteum's role in growth, including in long bones like the radius, laying foundational insights into its developmental biology. By the early 19th century, Irish surgeon Abraham Colles provided a landmark clinical description in 1814 of the distal radius fracture now bearing his eponym, characterizing its dorsal angulation and displacement in his paper "On the Fracture of the Carpal Extremity of the Radius." The late 19th century marked a transformative era with Wilhelm Röntgen's 1895 discovery of X-rays, which enabled non-invasive visualization of the radius and revolutionized the of fractures, such as those at the distal end, by revealing internal bone alignment without surgery. In the 1980s, the advent of computed tomography (CT) and early techniques further enhanced study of the radius's articulations, allowing precise mapping of its proximal and distal joints for surgical planning. Standardized nomenclature for the radius evolved significantly with the publication of in 1998 by the Federative Committee on Anatomical Terminology, which formalized terms such as caput radii for the head and styloides processus radii for the styloid process, promoting global consistency in anatomical description. This was further updated in the second edition (TA2) published in 2019 by the Federative International Programme on Anatomical Terminologies (FIPAT), which refined terms and ensured precise referencing in medical and educational contexts. This replaced earlier variations, ensuring precise referencing in medical and educational contexts.

References

  1. https://www.ncbi.nlm.nih.gov/books/NBK544512/
  2. https://www.ncbi.nlm.nih.gov/books/NBK557681/
  3. https://teachmeanatomy.info/upper-limb/bones/radius/
  4. https://www.kenhub.com/en/library/anatomy/the-radius-and-the-ulna
  5. https://www.physio-pedia.com/Radius
  6. https://pubmed.ncbi.nlm.nih.gov/11733125/
  7. https://www.orthobullets.com/trauma/1019/radial-head-fractures
  8. https://my.clevelandclinic.org/health/body/24528-radius
  9. https://pressbooks-dev.oer.hawaii.edu/anatomyandphysiology/chapter/bones-of-the-upper-limb/
  10. https://www.cbspd.com/assets/documents/WGkDdtxVDq3njREA8Hs91732859361.pdf
  11. https://www.kenhub.com/en/library/anatomy/anterior-interosseous-artery
  12. https://www.orthobullets.com/trauma/1027/distal-radius-fractures
  13. https://www.jbjs.org/reader.php?rsuite_id=2d3498ea-289d-463c-8c02-3f04e0c71c2f
  14. https://pmc.ncbi.nlm.nih.gov/articles/PMC4849245/
  15. https://www.sicot-j.org/articles/sicotj/full_html/2015/01/sicotj150009/sicotj150009.html
  16. https://radiopaedia.org/articles/listers-tubercle?lang=us
  17. https://emedicine.medscape.com/article/1254517-overview
  18. https://teachmeanatomy.info/the-basics/ultrastructure/bone/
  19. https://pmc.ncbi.nlm.nih.gov/articles/PMC6053074/
  20. https://pmc.ncbi.nlm.nih.gov/articles/PMC5101038/
  21. https://pmc.ncbi.nlm.nih.gov/articles/PMC11786143/
  22. https://www.ncbi.nlm.nih.gov/books/NBK557584/
  23. https://pmc.ncbi.nlm.nih.gov/articles/PMC3152283/
  24. https://www.ncbi.nlm.nih.gov/books/NBK539718/
  25. https://radiopaedia.org/articles/ossification-centres-of-the-wrist?lang=us
  26. https://pmc.ncbi.nlm.nih.gov/articles/PMC5782864/
  27. https://embryology.med.unsw.edu.au/embryology/index.php?title=Template:Upper_limb_ossification_table
  28. https://pressbooks.gvsu.edu/introhumanosteology/chapter/epiphyseal-union/
  29. https://pmc.ncbi.nlm.nih.gov/articles/PMC7484711/
  30. https://www.orthobullets.com/hand/6070/madelungs-deformity
  31. https://www.wheelessonline.com/bones/methods-to-estimate-growth-potenital/
  32. https://www.ncbi.nlm.nih.gov/books/NBK538494/
  33. https://www.physio-pedia.com/Goniometry:_Forearm_Supination
  34. https://www.ncbi.nlm.nih.gov/books/NBK547720/
  35. https://pmc.ncbi.nlm.nih.gov/articles/PMC5397311/
  36. https://www.ncbi.nlm.nih.gov/books/NBK537055/
  37. https://www.ncbi.nlm.nih.gov/books/NBK539744/
  38. https://mobile.fpnotebook.com/Ortho/Exam/WrstExm.htm
  39. https://www.ncbi.nlm.nih.gov/books/NBK560907/
  40. https://pubmed.ncbi.nlm.nih.gov/9471063/
  41. https://pubmed.ncbi.nlm.nih.gov/25795995/
  42. https://pubmed.ncbi.nlm.nih.gov/11817880/
  43. https://teachmeanatomy.info/encyclopaedia/s/supinator/
  44. https://pubmed.ncbi.nlm.nih.gov/12121684/
  45. https://teachmeanatomy.info/upper-limb/muscles/anterior-forearm/
  46. https://www.kenhub.com/en/library/anatomy/brachioradialis-muscle
  47. https://www.kenhub.com/en/library/anatomy/flexor-pollicis-longus-muscle
  48. https://www.kenhub.com/en/library/anatomy/extensor-pollicis-brevis-muscle
  49. https://teachmeanatomy.info/upper-limb/areas/extensor-tendon-compartments-wrist/
  50. https://www.kenhub.com/en/library/anatomy/abductor-pollicis-longus-muscle
  51. https://www.kenhub.com/en/library/anatomy/pronator-quadratus-muscle
  52. https://pubmed.ncbi.nlm.nih.gov/19833450/
  53. https://pmc.ncbi.nlm.nih.gov/articles/PMC11775041/
  54. https://www.ncbi.nlm.nih.gov/books/NBK536916/
  55. https://pmc.ncbi.nlm.nih.gov/articles/PMC4311337/
  56. https://www.ncbi.nlm.nih.gov/books/NBK448140/
  57. https://www.ncbi.nlm.nih.gov/books/NBK470188/
  58. https://pmc.ncbi.nlm.nih.gov/articles/PMC2823185/
  59. https://pmc.ncbi.nlm.nih.gov/articles/PMC5447903/
  60. https://www.orthobullets.com/hand/6067/radial-clubhand-radial-deficiency
  61. https://www.orthobullets.com/hand/6050/kienbocks-disease
  62. https://orthoinfo.aaos.org/en/diseases--conditions/arthritis-of-the-wrist/
  63. https://pubmed.ncbi.nlm.nih.gov/8583065/
  64. https://pubmed.ncbi.nlm.nih.gov/17009815/
  65. https://pmc.ncbi.nlm.nih.gov/articles/PMC3621383/
  66. https://pubmed.ncbi.nlm.nih.gov/10641681/
  67. https://www.orthobullets.com/trauma/1064/hand-and-forearm-compartment-syndrome
  68. https://pmc.ncbi.nlm.nih.gov/articles/PMC3928382/
  69. https://pmc.ncbi.nlm.nih.gov/articles/PMC10786111/
  70. https://www.science.smith.edu/departments/biology/VHAYSSEN/msi/pdf/i0076-3519-628-01-0001.pdf
  71. https://statemuseum.arizona.edu/sites/default/files/Distinguishing%2520Human%2520From%2520Animal%2520Bone%2520%2528Watson%2520and%2520McClelland%25202018%2529.pdf
  72. https://dash.harvard.edu/bitstreams/ece7418f-bbd5-4430-bee9-8b46f94230f2/download
  73. https://pmc.ncbi.nlm.nih.gov/articles/PMC12269350/
  74. https://pmc.ncbi.nlm.nih.gov/articles/PMC2750765/
  75. https://pmc.ncbi.nlm.nih.gov/articles/PMC10401756/
  76. https://people.ohio.edu/witmerl/Downloads/1993_Baumel_&_Witmer_NAA-2_Osteologia.pdf
  77. https://meyersgroup.ucsd.edu/papers/journals/Meyers%2520423.pdf
  78. https://pmc.ncbi.nlm.nih.gov/articles/PMC5807948/
  79. https://repositories.lib.utexas.edu/bitstreams/cfba50ba-9d97-49d6-bb00-ac3c3124ab19/download
  80. https://pmc.ncbi.nlm.nih.gov/articles/PMC5762864/
  81. https://pmc.ncbi.nlm.nih.gov/articles/PMC9292778/
  82. https://onlinelibrary.wiley.com/doi/10.1111/vsu.14232
  83. https://www.etymonline.com/word/radius
  84. https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC1987542&blobtype=pdf
  85. https://dokumen.pub/galen-on-the-usefulness-of-the-parts-of-the-body-de-usu-partium.html
  86. https://www.sciencemuseum.org.uk/sites/default/files/2023-11/The-Fabric-of-the-Human-Body-by-Andreas-Vesalius-.pdf
  87. https://pmc.ncbi.nlm.nih.gov/articles/PMC11176209/
  88. https://www.nejm.org/doi/full/10.1056/nejm181410010030410
  89. https://pmc.ncbi.nlm.nih.gov/articles/PMC3345122/
  90. https://pmc.ncbi.nlm.nih.gov/articles/PMC9777835/
  91. https://fipat.library.dal.ca/TA2
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