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Anatomical neck of humerus

The anatomical neck of the humerus is a narrow, obliquely oriented groove encircling the humeral head, marking the junction between the articular surface of the head and the tuberosities (greater and lesser tubercles). It represents the former epiphyseal line and serves as the capsular attachment site for the shoulder (glenohumeral) joint.

It is distinct from the surgical neck, which lies distal to the tubercles and is a common fracture site. The anatomical neck is an important structural landmark for joint capsule attachment, vascular supply to the humeral head, and defining articular boundaries of the glenohumeral joint.

Synonyms

  • Articular neck of humerus

  • Capsular groove of humerus

  • Humeral head junction

Location and Structure

  • Position: Lies at the oblique border between the head of the humerus and the greater and lesser tubercles.

  • Shape: Slightly constricted and irregular, forming a narrow groove surrounding the articular surface.

  • Orientation: Oblique — more pronounced posteriorly and inferiorly than anteriorly.

  • Articular relationship: Demarcates the articular head (covered by hyaline cartilage) from the non-articular bone of the tubercles.

  • Epiphyseal nature: Represents the site of fusion between the humeral head epiphysis and the metaphysis.

Relations

  • Superiorly: Humeral head (articular cartilage).

  • Inferiorly: Surgical neck and proximal humeral shaft.

  • Anteriorly: Lesser tubercle and insertion of the subscapularis tendon.

  • Posteriorly: Greater tubercle with attachments of supraspinatus, infraspinatus, and teres minor.

  • Medially: Capsule of the glenohumeral joint attaches circumferentially to the anatomical neck margin.

Attachments

  • Joint capsule: The fibrous capsule of the glenohumeral joint attaches to the anatomical neck except superiorly, where it extends onto the humeral head.

  • Glenohumeral ligaments: Blend with the capsule anteriorly near the neck region.

  • Articular cartilage: Covers the head up to the anatomical neck margin.

  • Synovial membrane: Lines the internal aspect of the capsule around the neck.

Nerve Supply

  • Periosteal innervation by branches of the axillary nerve and suprascapular nerve.

  • Joint capsule sensory innervation through axillary, suprascapular, and lateral pectoral nerves.

Function

  • Structural demarcation: Defines the boundary between articular and non-articular surfaces of the proximal humerus.

  • Capsular anchorage: Provides attachment for the glenohumeral joint capsule, maintaining joint integrity.

  • Vascular conduit: Serves as the site where ascending branches of the anterior and posterior circumflex humeral arteries enter the humeral head.

  • Mechanical role: Distributes stress between the humeral head and tubercles during shoulder movement.

Clinical Significance

  • Fractures: Rarely isolated; may occur with head-splitting fractures or in association with dislocation.

  • Vascular compromise: Fractures near the anatomical neck can disrupt epiphyseal blood supply, predisposing to avascular necrosis of the humeral head.

  • Degeneration and osteophytes: Common in osteoarthritis of the glenohumeral joint.

  • Arthroscopy landmark: Used to identify capsule reflection and intra-articular boundaries.

  • Imaging importance: Crucial for assessing fracture extension, cartilage integrity, and avascular necrosis.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark).

    • Marrow: Bright due to fatty content in adults.

    • Articular cartilage: Smooth, thin, intermediate-to-low signal surrounding humeral head.

    • Joint capsule: Low signal encircling the neck.

    • Fractures: Linear low-signal lines; marrow edema appears intermediate-to-bright.

  • T2-weighted images:

    • Cortex: Low signal.

    • Marrow: Bright, though slightly less than on T1.

    • Cartilage: Intermediate-to-bright, easily outlining the articular surface.

    • Joint fluid: Hyperintense, highlighting glenohumeral recesses.

    • Pathology: Marrow edema, cartilage loss, or joint effusion appear as bright hyperintensities.

  • STIR:

    • Normal marrow: Intermediate-to-dark signal.

    • Pathologic marrow (edema, fracture, necrosis): Bright hyperintense areas with blurred trabecular margins.

    • Useful for early detection of osteonecrosis or occult fractures.

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow: Intermediate-to-dark signal with smooth cortical contour.

    • Abnormal: Focal bright hyperintensity indicates marrow edema or reactive change.

    • Ideal for subtle fractures, contusions, or early AVN (avascular necrosis) detection.

  • T1 Fat-Sat Post-Contrast:

    • Normal marrow: Homogeneous mild enhancement.

    • Inflammation or tumor: Irregular, patchy enhancement.

    • Avascular necrosis: Peripheral “double line” enhancement pattern with central non-enhancing necrotic core.

    • Postoperative or traumatic change: Peripheral enhancement around hematoma or scar tissue.

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation, sharply defined groove separating articular head and tubercles.

  • Marrow: Low-to-moderate density.

  • Articular surface: Smooth, curved; cartilage appears as low-density line.

  • Pathology:

    • Excellent for evaluating fracture lines, osteophytes, erosions, or sclerosis.

    • Avascular necrosis: May show subchondral lucency and collapse of articular surface.

    • Post-traumatic deformity: Well visualized in multiplanar reformats.

Post-Contrast CT (standard):

  • Bone: Minimal direct enhancement.

  • Soft tissue and periosteum: Enhance in inflammatory or post-surgical changes.

  • Usefulness:

    • Assessing healing, vascular lesions, or infection.

    • Differentiating subchondral cysts, osteolysis, and neoplastic involvement.

CT VRT 3D image

Anatomical neck of humerus ct vrt image

MRI image

Anatomical neck of humerus sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Anatomical neck of humerus ct coronal image