Pelvis

Question 1

Contents of the greater sciatic foramen

Answer 1

• piriformis muscle
• Suprapiriform foramen:
  
  • Superior gluteal artery and vein
  • Superior gluteal nerve
• Infrapiriform foramen:
  
  • Sciatic nerve
  • Pudendal nerve
  • Inferior gluteal artery and vein
  • Inferior gluteal nerve
  • Posterior femoral cutaneous nerve
  • Nerve to obturator internus
  • Nerve to quadratus femoris

Question 2

What structures pass near the sacrospinous ligament?

Answer 2

Sacrospinous ligament – a thin triangular ligament from the ischial spine to the outer edge of the coccyx and sacrum. The pudendal vessels and nerve pass immediately inferomedial to the ischial spine. Sutures placed through the SSL at least 2.5cm from the ischial spine on the superior border without transgressing the entire thickness are in an area generally free of arterial vessels

Question 3

Origin and insertion of obturator internus?

How to test for pain?

Answer 3

originates on the medial surface of the obturator membrane, exits the pelvis through the lesser sciatic foramen and inserts onto the greater trochanter of the femur.

To check for obturator internus tenderness get the patient to externally rotate and abduct their hip against resistance, this can replicate pelvic pain in patients with pelvic floor muscle pain

Question 4

What attaches to the ischial spine?

Answer 4

Ischial spine – part of the posterior border of the body of the ischium

provides attachment for:

• the levator ani muscles,
• pelvic fascia,
• coccygeus muscle
• sacrospinous ligament

Question 5

What is the tendinous arch/white line?

Answer 5

1. Tendonous arch (white line) of pelvic fascia (levator ani muscle) – runs from the lower part of the pubic symphysis to the ischial spine and is the line of attachment for the pelvic fascia and the levator ani muscles

Question 6

Obturator nerve

Answer 6

– forms from nerve roots L2-4,

descends through the fibres of psoas major and emerges from its medial border.

It then travels posteriorly to the common iliac vessels along the pelvic sidewall to exit the pelvis through the obturator canal in the obturator foramen to provide motor input to the medial aspect of the thigh (adduction) and sensory to the same area

Question 7

Femoral nerve

Answer 7

– L2-4, again travels through the psoas major muscle but emerges laterally and leaves the pelvis under the inguinal ligament. It provides motor input to the anterior thigh muscles for hip flexion and knee extension, and sensory input to the anteromedial thigh, lower leg and foot.

Question 8

Genitofemoral nerve

Answer 8

L1-2, travels through psoas major and emerges on its anterior surface where it then divides into:

Genital branch – passes through the deep inguinal ring into the inguinal canal accompanying the round ligament and innervating the mons pubis and labia majora

Femoral branch – passes under the inguinal ligament laterally and innervates the skin of the upper anterior and medial thigh

Question 9

Contents of Alcock’s canal

Answer 9

the pudendal nerve, artery and vein.

Question 10

Pudendal nerve

Answer 10

1. The nerve forms from the sacral plexus (S2-4), leaves the pelvis through the greater sciatic foramen behind the sacrospinous ligament close to the ischial spine and re-enters the pelvis through the lesser sciatic foramen. It then accompanies the pudendal vessels in Alcock’s canal formed by fascia from the obturator internus muscle. It supplies sensation to the external genitalia and the perianal and perineal skin, and motor input to the levator ani muscles, external urethral/anal sphincters (provides voluntary control of faecal and urinary continence – S2, 3, 4 keeps the poo off the floor) and ischiocavernosus/bulbospongiosus.

Question 11

What is the significance of the sacral promontory?

Answer 11

• ‘summit’ of the pelvis
• common iliac vessels bifurcate into external and internal iliacs at this level
• The ureter crosses over from the lateral to the medial side at this level over the bifurcation of the iliac vessels.
• The superior hypogastric nerve plexus, as a parasympathetic nerve plexus, unites to form the left and right hypogastric nerves at this level. At this level the nerve fibers of the plexus are seen and, when traced inferiorly, form the hypogastric nerves.
• The sacral promontory forms the initiation point for transperitoneal para‐aortic lymph node dissection.

Question 12

What are the retroperitoneal spaces of the pelvis?

Answer 12

1. Bilateral:
   - Pararectal space
   - Paravesical space
2. Unilateral/midline:
   - Prevesical space
   - Rectovaginal space
   - Retrorectal or presacral space
   - Retropubic

Question 13

Pararectal space

• Borders?

Answer 13

• Anteriorly: Cardinal ligament,
• Medially: Rectal pillars, uterosacral ligament, ureter,
• Laterally: Internal iliac artery,
• Posteriorly: Sacrum,
• Caudally: Puborectalis muscle/levator ani
• Roof: posterior leaf broad ligament

Ureter divides it into medial and lateral pararectal spaces

Question 14

Contents of the medial pararectal space

Answer 14

Dissected to identify uterine artery

Contains the hypogastric nerve- important space for nerve sparing radical hysterectomy

Ureter divides medial and lateral spaces

Question 15

Surgeries using the pararectal space

Answer 15

• Radical hysterectomy
• Pelvic lymphadenectomy
• Excision of endometriosis
• Ureteric reimplantation/psoas hitch

Question 16

Symptoms of nerve injury to hypogastric plexus

Answer 16

• Risk with radical hysterectomy
• Located in pararectal space
• Parasympathetic innervation S2-S4
• Injury to the hypogastric plexus results in increased bladder tone, impaired ejaculation in men, and dyspareunia

Question 17

Borders of the paravesical space

Answer 17

Superior to pararectal space

Lateral to bladder

Borders:

Medially- bladder

Laterally- PSW

Inferiorly - uterine artery

Divided medially and laterally by obliterated hypogastric artery

Contents of lateral paravesical space: obturator nerve and pelvic lymph nodes

Question 18

Prevesical space

Answer 18

• Lies between bladder and anterior abdominal wall
• Enclosed laterally by lateral umbilical ligament

Question 19

Rectovaginal space

Answer 19

Borders:

• Anteriorly the uterus and the posterior vaginal wall,
• Posteriorly by the rectum
• Laterally by the uterosacral and the Mackenrodt ligament
• Roof comprises the peritoneal reflections of the pouch of Douglas
• Floor is formed by the levator ani muscle.

The Denonvilliers fascia is a two‐layered fascia present retroperitoneally yet between the rectum and the vagina: one layer covers the rectum and the second layer covers the vagina. The vaginal veins are present underneath the Denonvilliers fascia, covering the vagina. Hence, the avascular plane is created exactly between the two layers of Denonvilliers fascia to dissect the rectovaginal space.

Question 20

Symptoms of femoral nerve injury

Answer 20

• Nerve roots L2-L4
• Passes infero-laterally through the psoas muscle and emerges from its lateral border. It exits the pelvis beneath the inguinal ligament, lateral to the femoral vessels to enter the thigh.
• Most commonly occurs at time of hysterectomy when lateral retractors are used/self retaining
• Can also happen with poor pt positioning- if hyperflexion/abduction/ext rotation of the hip occurs.

Sx: weakness of hip flexion and adduction and knee extension. Loss of the knee jerk reflex and paraesthesia over the anterior and medial thigh, as well as the medial aspect of the calf.

Question 21

Symptoms of ilioinguinal and iliohypogastric nerve injury

Answer 21

• T12-L1
• Both nerves pass laterally through the head of the psoas muscle before running diagonally along quadratus lumborum
• Injury typically due to nerve entrapment at lateral borders following pfannanstiel

Triad of symptoms:

1. sharp burning pain radiating from the incision site to the mons pubis, labia and thigh,
2. paraesthesia over the nerve distribution areas,
3. pain relief following administration of local anaesthetic

Question 22

Injury to genitofemoral nerve

Answer 22

L1-L2

Transverses the anterior surface of psoas, and lies immediately lateral to the external iliac vessels. It divides into a genital branch, which enters the deep inguinal ring, and a femoral branch, which passes deep to the inguinal ligament within the femoral sheath.

This nerve is susceptible to injury during pelvic sidewall surgery and during removal of the external iliac nodes.

Injury: paraesthesia over the mons pubis, labia majorum and femoral triangle

Question 23

Injury to lateral cutaneous nerve of the thigh

Answer 23

L2-L3

emerges from the lateral border of psoas

Mechanism of injury: similar to femoral

Symptoms: paraesthesia and pain in the anterior and posterio-lateral thigh

Question 24

Sx of injury to obturator nerve

Answer 24

L2-L4

The anterior branches of L2–L4 give rise to the obturator nerve and converge behind the psoas muscle. The obturator nerve then passes over the pelvic brim in front of the sacroiliac joint and behind the common iliac vessels to enter the thigh via the obturator foramen

Cause of injury: retroperitoneal surgery, excision of endometriosis, the passage of a trocar through the obturator foramen, insertion of transobturator tapes and during paravaginal defect repairs.

Symptoms: sensory loss in the upper medial thigh and motor weakness in the hip adductors

Question 25

Injury to Sciatic and common peroneal nerve

Answer 25

L4–S3 nerve roots

Emerges from the pelvis below the piriformis muscle, curving laterally and downward through the gluteal region. Initially it lies midway between the posterior superior iliac spine and ischial tuberosity. Lower down in the thigh it courses midway between the ischial tuberosity and greater trochanter.

The common peroneal nerve and tibial nerve are its two derivatives at the mid-thigh. The common peroneal nerve importantly winds forward around the neck of the fibula.

Common cause of injury: The sciatic and peroneal nerves are commonly injured at the sciatic notch and the lateral aspect of the fibular neck respectively. Both nerves are susceptible to stretch injuries from hyperflexion of the thighs in improper lithotomy positions. The common peroneal nerve may be compressed at the fibular neck in lithotomy.

Sciatic nerve injury presents as sensory impairment below the knee and weakness of hip extension and knee flexion. Foot drop is reported when the common peroneal nerve is injured, along with paraesthesia over the calf and dorsum of the foot

Question 26

Injury to pudendal nerve

Answer 26

S2–S4

Exits the pelvis initially through the greater sciatic foramen below the piriformis. Runs behind the lateral third of the sacrospinous ligament and ischial spine alongside the internal pudendal artery and immediately re-enters the pelvis through the lesser sciatic foramen to the pudendal canal (Alcock’s canal).

Common cause of injury: entrapment injuries during sacrospinous ligament fixation as it runs behind the lateral aspect of the sacrospinous ligament.

Symptoms: postoperative gluteal, perineal and vulval pain, which worsens in the seated position if the nerve is damaged.