Pubis

The pubis, together with the ilium and ischium, make up the innominate bone of the pelvis. These are individual bones in the youth and unite to form one bone in adults, the principal union being in the acetabulum.

The pubis is the ventral part of the innominate bone and forms a median cartilaginous symphysis (pubic symphysis).

Gross anatomy

Osteology

The pubic bone has an anteromedial body, a superior ramus passing upwards to the acetabulum and an inferior ramus bordering the obturator foramen which joins the ischial ramus (conjoined ramus or the ischiopubic ramus).

The body of pubis is flattenedhas an anterior, posterior and symphysial surface.

The superior pubic ramus is triangular in cross-section has an anterior pectineal surface, a dorsosuperior pelvic surface and downsloping obturator surface. The pectineal surface extends from iliopubic or iliopectineal eminence to the pubic tubercle bounded by obturator crest in front and pecten pubis behind. The obturator surface exhibits an obturator groove along which the obturator vessels and nerves pass from pelvis to the thigh. Thepecten pubis is the sharp superior edge of the pectineal surface of the superior ramus of pubis.

The inferior pubic ramus has two surfaces, the antero-external surface facing the thigh and the postero-internal surface facing the perineum.

The pubic tubercle is the crest of bone forming the medial attachment of the inguinal ligament and is crossed by the spermatic cord.

Articulations

The symphysial surface is elongate and oval, united by cartilage to its fellow at the pubic symphysis.

Attachments

Musculotendinous

Muscles that originate from pubis:

• gracilis and adductor brevis at the external surface of the body of pubis and its inferior ramus
• obturator externus at external surface of superior and inferior rami
• obturator internus at pelvic surface of superior and inferior rami
• adductor longus at upper body of pubis just below the pubic crest
• pectineus muscle from the external surface of superior ramus
• sphincter urethrae also takes origin from the conjoint ramus.

Muscles that insert on the pubis:

• rectus abdominis (lateral head) just lateral to pubic crest
• pyramidalis just below the attachment of rectus abdominis
• levator ani (levator prostatae and puborectalis)
• conjoint tendon at the pecten pubis.

Ligamentous

• pubofemoral ligament and obturator membrane at obturator crest
• inguinal ligament (Poupart's ligament) at pubic crest
• ventral pubic ligament at medial aspect of anterior surface of body of pubis
• puboprostatic ligament at the pelvic surface of body of pubis
• lacunar ligament and pectineal ligament at the pecten pubis

Arterial Supply

• Branches of obturator, inferior epigastric, and medial circumflex femoral arteries

Development

Ossification

One ossification centre appears in the body of pubis at the prenatal 8th week, which fuses with the ossifying ischium to become a continuous ramus in the 7th or 8th year of life. The pubic tubercle, crest and symphysial surface may have separate centres.

Related pathology

• osteitis pubis
• pubic diastasis
• open book fracture
• bladder exstrophy