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Body of radius

The body (shaft) of the radius is the elongated central portion of the radius bone, extending between the expanded proximal end (head and neck) and the distal end (styloid process and articular surface). It is slightly curved, with its convexity directed laterally, allowing for forearm rotation during pronation and supination. The radius is the lateral bone of the forearm, situated parallel to the ulna, and plays a crucial role in forearm mechanics and wrist articulation.

The radial shaft is triangular in cross-section in its upper and middle parts and becomes more rounded distally. It provides strong attachment points for forearm muscles involved in flexion, extension, pronation, and supination. Its shape and interosseous border are key to the integrity of the interosseous membrane, which transmits forces between the radius and ulna.

Synonyms

  • Shaft of the radius

  • Corpus radii

  • Diaphysis of the radius

Structure and Surfaces

The shaft has three borders and three surfaces:

Borders:

  • Anterior border: Extends from the radial tuberosity to the styloid process; gives attachment to the flexor pollicis longus and pronator quadratus.

  • Posterior border: Less distinct, extending from the dorsal margin of the radial tuberosity downward to the distal dorsal surface.

  • Interosseous border (medial): Sharp ridge giving attachment to the interosseous membrane, connecting it with the ulna.

Surfaces:

  • Anterior surface: Smooth in upper part (attachment of flexor pollicis longus) and concave in lower part for pronator quadratus.

  • Posterior surface: Broad and convex, giving origin to the abductor pollicis longus and extensor pollicis brevis muscles.

  • Lateral surface: Rounded and smooth; insertion site for pronator teres proximally and continuous distally with the radial styloid process.

Relations

  • Medially: Interosseous membrane and ulna

  • Laterally: Supinator muscle proximally and tendons of abductor pollicis longus and extensor pollicis brevis distally

  • Anteriorly: Flexor pollicis longus, pronator quadratus, and radial artery in lower part

  • Posteriorly: Extensor tendons crossing over distal half (especially extensor pollicis longus and extensor carpi radialis longus/brevis)

  • Proximally: Continuous with neck and radial tuberosity

  • Distally: Broadens into distal radius articulating with the scaphoid and lunate bones of the wrist

Ossification

  • Primary center appears near the 8th week of fetal life for the shaft.

  • Secondary centers: one for the head (appears at 5 years, fuses around 17 years) and one for the distal end (appears at 1–2 years, fuses around 20 years).

  • Growth occurs mainly at the distal end, which contributes more to the overall length of the radius.

Function

  • Forearm rotation: Works with the ulna to allow pronation and supination, pivoting around the head and distal radioulnar joint.

  • Load transmission: Transfers weight from the hand and wrist to the forearm and elbow.

  • Muscle attachment: Provides origins and insertions for multiple forearm flexor and extensor muscles.

  • Structural stability: Interosseous border serves as an anchor for the interosseous membrane, maintaining alignment with the ulna.

Clinical Significance

  • Fractures: Commonly occur in the midshaft or distal third due to falls on an outstretched hand (e.g., Galeazzi and Monteggia fractures).

  • Stress fractures: Seen in athletes and gymnasts due to repetitive pronation-supination or axial loading.

  • Deformities: Malunion can impair pronation/supination mechanics and wrist alignment.

  • Osteomyelitis: Infection of the shaft may follow open injuries or surgical fixation.

  • Tumors: Rare, but primary bone lesions or metastases may involve the shaft.

  • Surgical relevance: Site for intramedullary nailing, plating, and bone grafting procedures.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark)

    • Marrow: Bright, reflecting fatty marrow in adults

    • Periosteum and interosseous membrane: Thin low-signal lines along borders

    • Fracture line: Linear low-signal band crossing cortex or marrow

    • Muscle planes: Clear intermediate signal surrounding bone

  • T2-weighted images:

    • Cortex: Dark, well-defined

    • Marrow: Bright, slightly less intense than T1

    • Pathology: Fractures, edema, or inflammation appear as hyperintense areas adjacent to cortex

    • Periosteal reaction: Linear bright signal in subperiosteal region in infection or stress injury

  • STIR:

    • Normal marrow: Intermediate-to-dark signal

    • Abnormal marrow: Bright hyperintense signal representing edema, inflammation, or tumor infiltration

    • Soft-tissue edema: Hyperintense regions adjacent to cortex in trauma or infection

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow: Intermediate-to-dark signal

    • Abnormal: Bright focal or diffuse areas indicating marrow edema or fracture

    • Ideal for detecting subtle cortical disruption, periosteal reaction, or soft-tissue inflammation

  • T1 Fat-Sat Post-Contrast:

    • Normal bone marrow: Homogeneous mild enhancement

    • Pathologic marrow: Heterogeneous enhancement in infection, tumor, or healing fracture

    • Periosteal enhancement: Indicates active inflammation or neovascularity

CT Appearance

Non-Contrast CT:

  • Cortex: High-attenuation dense bone with smooth contours

  • Trabecular pattern: Fine reticulation within medullary canal

  • Interosseous border: Sharp ridge visible medially along shaft

  • Pathology: Excellent for detecting fractures, cortical irregularity, sclerosis, and callus formation

  • Bone alignment: Evaluates rotational deformity and joint congruity in trauma cases

Post-Contrast CT (standard):

  • Enhancing periosteum or marrow: Suggests infection, inflammation, or healing response

  • Soft-tissue detail: Displays associated muscle injury, hematoma, or abscess formation

  • Commonly used to assess healing fractures, infection, or post-surgical complications

MRI images

Body of radius coronal cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI images

Body of radius CT CORONAL IMAGE

MRI images

Body of radius sag cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

CT image

Body of radius CT CORONAL IMAGE