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Inferior pubic ramus

The inferior pubic ramus is a thin, flat bony projection of the pubis that extends posterolaterally and inferiorly from the body of the pubis. It unites with the ischial ramus to form the ischiopubic ramus, a strong structural bar that contributes to the anterior wall of the pelvis and the boundaries of the obturator foramen.

Embryologically, the pubic and ischial rami develop from separate ossification centers that fuse during adolescence to form the ischiopubic ramus. Clinically, fractures of the inferior pubic ramus are common in pelvic trauma, osteoporosis, and stress injuries, and are often associated with acetabular or sacral injuries.

Attachments

  • Muscular:

    • Adductor longus

    • Adductor brevis

    • Gracilis

  • Ligamentous:

    • Inferior pubic ligament (part of pubic symphysis support)

  • Forms part of the border of the obturator foramen, giving attachment to the obturator membrane.

Relations

  • Forms the superior boundary of the pubic arch

  • Contributes to the anterior wall of the pelvic cavity

  • Lies anterior to the obturator canal through which the obturator nerve and vessels pass

Synonyms

  • Ramus inferior ossis pubis

  • Inferior branch of pubis

Function

  • Provides origin for adductor muscles of the thigh (adductor longus, adductor brevis, gracilis)

  • Contributes to stability of pelvic ring by articulating with ischial ramus

  • Supports load transfer between axial skeleton and lower limbs

  • Serves as a landmark in orthopedic and gynecologic procedures

Nerve Supply (related attachments)

  • Adductor muscles: innervated by obturator nerve (L2–L4)

  • Gracilis: obturator nerve (anterior branch)

Arterial Supply

  • Obturator artery (branch of internal iliac artery)

  • Inferior epigastric artery contributes via pubic branch

Venous Drainage

  • Obturator vein → internal iliac vein

  • Communications with external iliac vein via pubic venous plexus

MRI Appearance

T1-weighted images:

  • Cortex: dark hypointense rim

  • Marrow: intermediate signal

  • Clear outline against surrounding pelvic soft tissues

T2-weighted images:

  • Cortex: hypointense

  • Marrow: intermediate to bright signal depending on fat content

  • Detects stress reactions and marrow changes in fractures

PD Fat-Saturated (Proton Density FS):

  • Cortex: remains hypointense

  • Marrow edema or stress fracture: bright hyperintense

  • Sensitive for subtle fractures and enthesopathies

STIR:

  • Suppresses fat, making bone marrow edema, fractures, or inflammation appear hyperintense

  • Highly sensitive for early stress injuries in athletes or osteoporosis

T1 Post-Gadolinium (fat saturation):

  • Bone cortex: no enhancement

  • Inflammatory, neoplastic, or infectious changes: abnormal enhancement of marrow or surrounding soft tissues

  • Useful in osteomyelitis, tumors, or pelvic soft tissue pathology

3D T2-weighted Imaging:

  • Cortex: dark hypointense outline

  • Provides high-resolution multiplanar reconstructions of pelvic ring and obturator foramen

  • Important for fracture planning and surgical navigation

CT Appearance

Non-contrast CT:

  • Cortex: hyperdense and sharply defined

  • Marrow: relatively hypodense compared to cortex

  • Gold standard for detecting fractures, cortical disruptions, or bony remodeling

CT Post-Contrast:

  • Bone cortex: unchanged, remains hyperdense

  • Soft tissue enhancement: highlights abscesses, tumors, or inflammatory changes around the pubic ramus

  • 3D CT reconstructions used in preoperative pelvic surgery planning

Clinical Significance

  • Fractures: Common in elderly with osteoporosis or high-energy trauma in young adults

  • Stress fractures: Seen in athletes, especially runners

  • Oncology: Site of involvement in primary pelvic tumors or metastases

  • Surgical relevance: Landmark in approaches to acetabulum and pelvic floor surgery

CT VRT 3D image

Inferior pubic ramus 3D CT VRT anatomy image

CT image

Inferior pubic ramus ct axial iamge

MRI image

Inferior pubic ramus MRI axial anatomy image-img-00000-00000