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Ischiopubic ramus

The ischiopubic ramus is the thin bony plate formed by the union of the inferior pubic ramus and the ramus of the ischium. Together, they form part of the anteroinferior boundary of the obturator foramen and contribute to the framework of the anterior pelvis. It is an important site for muscular attachment, transmission of body weight in sitting, and serves as a radiologic landmark in pelvic trauma, infection, and oncology.

Synonyms

  • Pubic-ischial ramus

  • Inferior pubic ramus + ischial ramus

  • Ischiopubic junction

Structure and Relations

  • Composition: Union of the inferior pubic ramus (anteriorly) with the ischial ramus (posteriorly)

  • Shape: Thin, flattened, and slightly curved bone, forming a bridge in the lower pelvis

  • Surfaces:

    • Outer surface: Faces laterally, gives origin to adductor muscles

    • Inner surface: Faces medially, related to pelvic cavity and covered by obturator internus muscle

  • Borders:

    • Superior border: Contributes to obturator foramen

    • Inferior border: Attachment for perineal and urogenital diaphragm muscles

  • Relations:

    • Anteriorly: Adductor longus and brevis muscles

    • Posteriorly: Obturator externus and adductor magnus

    • Inferiorly: Perineal membrane, bulbospongiosus, ischiocavernosus muscles

    • Superiorly: Obturator canal and obturator vessels/nerve

Nerve Supply

  • No direct innervation; periosteum innervated by branches of obturator and pudendal nerves (pain sensitive)

Arterial Supply

  • Obturator artery branches

  • Inferior pubic branches of internal pudendal artery

  • Periosteal vessels from surrounding pelvic circulation

Venous Drainage

  • Drains into obturator vein and internal pudendal vein, then into internal iliac venous system

Function

  • Structural component of anterior pelvic ring, providing support and stability

  • Forms boundary of obturator foramen, passage for neurovascular structures

  • Provides attachment for adductors and perineal muscles

  • Distributes weight during sitting and locomotion

Clinical Significance

  • Fractures: Common in pelvic ring injuries; may disrupt pelvic stability

  • Stress fractures: Seen in athletes and military recruits

  • Tumors: May be affected by metastasis, sarcoma, or chondrosarcoma

  • Infection: Osteomyelitis or extension of pelvic abscess may involve it

  • Surgical relevance: Landmark in pelvic reconstructive and orthopedic surgeries

MRI Appearance

T1-weighted images:

  • Cortex: very dark (signal void)

  • Marrow: bright to intermediate signal depending on fatty content

  • Fractures: dark linear band interrupting marrow signal

T2-weighted images:

  • Cortex: dark

  • Marrow: bright to intermediate signal depending on fatty content

  • Pathology (edema, infection, tumor): hyperintense regions replacing normal marrow

STIR (Short Tau Inversion Recovery):

  • Cortex: dark

  • Normal marrow: relatively low signal

  • Edema, infection, or tumor: bright hyperintensity within marrow

T1 Fat-Sat Post-Contrast:

  • Cortex: no enhancement

  • Normal marrow: mild homogeneous enhancement

  • Tumor, infection, fracture healing: heterogeneous or focal enhancement

  • Abscess: rim enhancement with central non-enhancing cavity

CT Appearance

Non-Contrast CT:

  • Cortex: dense bright white

  • Marrow: lower density relative to cortex

  • Fractures: seen as cortical breaks or lucent lines

  • Lytic lesions: focal hypodense areas

  • Sclerotic lesions: areas of increased density

Post-Contrast CT:

  • Cortex: does not enhance

  • Marrow: mild uniform enhancement

  • Pathology (infection, tumor, metastasis): heterogeneous enhancement

  • Abscess/necrosis: rim enhancement with central hypodensity

CT VRT 3D image

Ischiopubic ramus 3d ct image

CT image

Ischiopubic ramus ct axial

CT image

Ischiopubic ramus ct coronal

MRI image

Ischiopubic ramus MRI axial anatomy image-img-00000-00000