Joints of the pelvis

Question 1

Sacro-iliac joint

Answer 1

• Os coxae attached to axial skeleton
• Joint surfaces are the facies auricularis ossis coxae and the facies auricularis ossis sacri
• Uneven surface - amphiartrosis, immobile joint
• Joint capsule attached to margins of joint surface
• Secured by a row of very strong ligaments

Question 2

Ligamenta sacroiliaca ventralia

Answer 2

• Reinforce joint capsule on the frontal side
• Connect the anterior surface of the lateral part of the sacrum to the margin of the auricular surface of the ilium and to the preauricular sulcus

Question 3

Ligamenta sacroiliaca interossea

Answer 3

• Very strong
• Between tuberositas sacralis and tuberositas iliaca

Question 4

Dorsal (posterior) sacroiliac ligaments

Answer 4

• Between the posterior iliac apine and tuberosities on the dorsal side of the sacral bone

Question 5

Iliolumbar ligament

Answer 5

• Between the dorsal part of the iliac crest and processus costarii of L4 and L5

Question 6

Sacrospinal ligament

Answer 6

• From the ischiadic spine to the lateral margins of the sacral bone and coccyx

Question 7

Sacrotuberal ligament

Answer 7

• Links the ischial tuberosity with the lateral margins of the sacrum and coccyx
• From the ischial tuberosity the processus falciformis runs frontally and it attaches to the lower margin of the os coxae

Question 8

Sacrospinal ligament

Answer 8

• Closes incisura ischiadica major and changes it into the foramen ischiadicum majus
• The foramen is split by the m. piriformis into two foramen suprapiriforme through which the superior gluteal vessels and nerve pass and foramen infrapiriforme through which the inferior gluteal vessels and nerve, ischiadic nerve, posterior cutaneous femoral nerve, internal pudendal vessels and pudendal nerve pass

Question 9

Foramen ischiadicum minus

Answer 9

• Formed by the closure of the incisura ischiadica minor by the sacrotuberous ligament which runs between the sacrum and the ischial tuberosity and the sacrospinous ligament which runs between the sacrum and the ischial spine
• Tendon of m. obturator internus passes through it to the fossa ischiorectalis
• The pudendal nerve and internal pudendal vessels also pass through here

Question 10

Pubis symphysis

Answer 10

• Unpaired synchondrosis - practically immobile
• Joins frontal margins of both pelvic bones
• Discus interpubicus is inserted between facies symphysis of both pubic bones, this is a layer of fibrous cartilage, 45mm long in women and 50mm long in men
• Reinforced by two strong ligaments: lig. pubicus superius found on the cranial side of the symphysis and a stronger lig. arcuatum pubis which fills the angle between the lower margins of the symphysis
• Towards end of pregnancy can soften due to influence of hormones in order to enable a slight enlargement of the birth canal during labour

Question 11

Obturator membrane

Answer 11

• Strong fibrous membrane
• Incompletely closes the obturator foramen
• Transforms the obturator sulcus into the obturator canal through which the obturator vessels and nerve pass
• Both faces of the obturator membrane are sites of origin of mm. obturatorii