Gluteal Region and Ischiorectal Fossa - Study Guide

Bony landmarks

• asis
• aiis
• iliac crest
• posterior superior/inferior iliac spine
• parts of the ilium (hip bone, innominate bone)
• sacrum and coccyx
• ischial spine and notch

Ligaments

• sacrotuberous ligament
• sacrospinous ligament

Muscles

• gluteus maximus - sacrum, ilium,
  • iliotibial tract
  • femoral tuberosity
  • inferior gluteal nerve
• gluteus medius - anterior/posterior gluteal lines
  • greater trochanter
• superior gemellus - ischial spine
  • intertrochanteric crest by way of obturator internus tendon
• inferior gemellus - ischial tuberosity
• gluteus minimus - anterior and inferior gluteal lines
  • greater trochanter
  • superior gluteal nerve
• obturator internus
  • lateral rotator
• quadratus femoris
  • lateral rotator
  • ischial tuberosity
  • intertrochanteric crest
• tensor fascia lata
  • origin?
  • superior gluteal nerve
  • iliotibial tract
• piriformis muscle
  • greater sciatic foramen
  • superior aspect of intertrochanteric crest of greater trochanter
  • lateral rotator

Relationships of the piriformis muscle to structures passing through the greater sciatic foramen

• superior
  • superior gluteal a. n. v.
• inferior
  • inferior gluteal n. a. v.
  • sciatic nerve
  • posterior femoral cutaneous n.
  • n. to quadratus femoris
  • internal pudendal a. v.
  • pudendal n.
  • nerve to obturatus internus

Lumbar plexus

• a collection of nerve fibers derived from spinal nerves T12-L4
• elaborates peripheral nerves

Sacral plexus

• L4-S4
• lumbosacral trunk connects lumbar plexus to the sacral plexus to, thus, form the lumbosacral plexus.

Peripheral nerve distributions versus dermatomal distributions

• Spinal nerve distribution versus dermatomal distribution

Quadrants of the gluteal region and gluteal injection

• upper lateral quadrant is safest for injection

Gluteal Region and the Ischio Rectal Fossa - Study Guide

True/False Questions

1. The spinal cord ends at the vertebral level of L2(3) whereas the spinal canal continues to the level of S2.
2. The sacrospinous ligament contributes the superior border of the of the lesser sciatic foramen.
3. The sacrotuberous ligament contributes the superior border of the lesser sciatic foramen.
4. The gluteus maximus muscle takes insertion, in part, from the sacrotuberous ligament.
5. In addition to the iliotibial tract, the gluteus maximus muscle inserts onto the linea aspera.
6. The gluteus maximus muscle receives the inferior gluteal artery but not the inferior gluteal nerve.
7. The gluteus maximus muscle receives the superior gluteal artery but not the superior gluteal nerve.
8. When standing with just one lower extremity planted (on one foot), the gluteus medius is an adductor of the free (un-planted) lower extremity.
9. The quadratus femoris muscle, by virtue of inserting onto the intertrochanteric line, is a medial rotator of the hip joint.
10. The superior and inferior gemelli insert onto the trochanteric fossa by way of the obturator externus tendon.
11. The superior gluteal nerve, but not the superior gluteal artery, enter the gluteus maximus muscle.
12. The pudendal nerve, as it crosses the posterior surface of the ischial spine, is accompanied by the the external pudendal artery.
13. The posterior cutaneous nerve of the thigh, within the gluteal region is located immediately medial to the peroneal portion of the sciatic nerve.
14. The lumbar plexus, by way of the lumbosacral trunk, communicates (connects) with the sacral plexus.
15. The ventral ramus of the L5 spinal nerve does not contribute to the lumbar plexus.
16. The ventral ramus of the L4 spinal nerve contributes both to the lumbar plexus and to the sacral plexus.
17. The sciatic nerve consists of a peroneal portion that innervates original dorsal musculature and a tibial portion that innervates original ventral musculature.
18. The lateral femoral cutaneous nerve contributes to the L2, L3, and L4 dermatome.
19. The lateral femoral cutaneous nerve, by way of the lumbar plexus, receives contributions from the ventral rami of spinal nerves L1, L2, L3.

1. The greater and lesser trochanters are related on the anterior femur by the introchanteric crest.
2. The two innominate bones are joined at their anterior extents by the sacroiliac joints.
3. Intermediate between the greater and lesser sciatic notches is the ilial spine.
4. The greater sciatic foramen, an osseofibrous foramen, has the sacrospinous ligament contributing to its superior boundary.
5. The lesser sciatic foramen provides a communication between the gluteal region and the ischiorectal fossa.
6. The spinal cord ends at the level of L2 but the spinal canal extends to sacral level 2.

1. The gluteus maximus is vacularized by both the superior and inferior gluteal arteries but its motor innervation is by the inferior gluteal nerve only and not the superior gluteal nerve.
2. The gluteus medius lies deep to the the gluteus maximus and superficial to the gluteus minimus.
3. The gluteus medius lies anterior to the gluteus maximus and posterior to the gluteus minimus.
4. The inferior gemellus originates from the ischial spine and inserts onto the tendon of the obturator externus and then the fovea of the femur.
5. The superior gemellus arises from the ischial spine and inserts on the the tendon of the obturator internus and then the fovea of the femur.
6. The superior gluteal nerve travels transversely deep to the gluteus medius and superficial to gluteus minimus toward the tenser fascia lata.
7. The piriformis, superior gemellus, obturator internus, inferior gemullus, and quadratus femoris make up 5 short lateral rotators of the hip.
8. The origins of the superior and inferior gemeli are interrupted by the greater sciatic notch.
9. Both the superior gluteal nerve and the sciatic nerve enter the gluteal region by passing superior to the piriformis.
10. The lumbar plexus receives ventral rami, but not dorsal rami, from spinal nerves.

1. The lumbar plexus, a somatic plexus, elaborates the femoral and obturator nerves (non-exhaustive).
2. The sacral plexus, a somatic plexus, elaborates the sciatic nerve, superior gluteal nerve, and inferior gluteal nerve (non-exhaustive)..

1. A peripheral nerve derived from a plexus typically contributes to more than one dermatome.
2. A spinal nerve contributes to one dermatome only.
3. A dermatomal region of anesthesia indicates spinal nerve damage (eg. herniated disc).
4. A cross-dermatomal region of anesthesia indicates damage to a peripheral nerve derived from a plexus (eg. nerve entrapment).

Definition and Short Answer

1. What is a key difference between the distribution of the superior gluteal artery and the superior gluteal nerve?
2. How does nerve to obturator externus enter the gluteal region?
3. Somatic nerve plexus. What is the difference between a dermatome and a peripheral nerve distribution?
4. The tibial and common peroneal parts of the sciatic nerve reflect what about development of the lower extremity?
5. What is a key difference, other than distribution, between the superior and inferior clunial nerves?
6. What dermatomal levels equate to peripheral nerve distributions? What key anatomical structures are not found at these levels?
7. The greater sciatic foramen provides an osseofibrous communication between the (blank) cavity and the (blank) region. The lesser sciatic foramen provides an osseofibrous communication between the (blank) region and the (blank) fossa.
8. The superior gluteal nerve leaves the (blank) cavity passing throught the (blank) foramen opposed to the superior surface of the (blank) muscle. Within the (blank) region, the superior gluteal nerve courses laterally on the anterior surface of the (blank) muscle and on the posterior surface of the (blank) muscle. Extending further laterally, the superior gluteal nerve provides its most distal innervation to the (blank) muscle. Discuss a key anatomical difference between the distribution of the superior gluteal nerve and the distribution of the superior gluteal artery.
9. The pudendal nerve leaves the (blank) cavity passing through the (blank) foramen inferior to the (blank) muscle. In the gluteal region the pudendal nerve courses inferior along the posterior surfaces of the (blank) muscle, (blank) ligament, and (blank) spine. The pudendal nerve leaves the (blank) region passing through the (blank) foramen to the (blank) fossa. Within the (blank) fossa, the pudendal nerve courses along the (blank) edge on the medial wall of the (blank) tuberosity in an osseofibrous passageway known as the (blank) canal.
10. The greater sciatic foramen shares its inferior boundary with the superior boundary of the lesser sciatic foramen by way of the (blank) ligament.
11. The embryological determination of origin and insertion relies on proximal/distal anatomy. What is the embryological origin of the gluteus medius? What is the functional origin of the gluteus medius when the opposite lower limb is not planted during standing or walking?
12. The obturator internus has an origin within the (blank) cavity and a tendinous projection that enters the (blank) region passing through the (blank) foramen inferior to the (blank) muscle. Together, these three muscles insert on the (blank) crest and act to (blank) rotate the (blank) joint.
13. There are five short lateral rotators in the gluteal region. In order, from superior to inferior, these are the (blank), (blank), (blank), (blank), and (blank) muscles.
14. Three nerves enter the gluteal region crossing the anterior/inferior surface of the (blank) muscle and the posterior/superior surface of the (blank) muscle and/or the (blank) ligament and/or the (blank) spine. From medial to lateral these nerves are the (blank), (blank), and (blank) nerves. The two most medial of these nerves leave the gluteal region by way of the (blank) foramen to enter the (blank) fossa whereas the most lateral of these three nerves courses inferiorly to enter the posterior (blank) as the nerve crosses anterior to the (blank) fold.
15. A probe passed from the superficial gluteal region to a deeper location about 1/4" anterior to the interval between the inferior gemellus and the quadratus femoris. The tip of the probe is in contact with the (blank) muscle and branches of the (blank) artery.
16. What is the difference between a dermatome and a peripheral nerve distribution. You will understand this difference when you know why a sensory deficit that maps a dermatome indicates a nerve lesion proximal to a nerve plexus whereas a sensory deficit that maps a peripheral nerve distribution indicates a lesion distal to a nerve plexus. In the former case the lesion might be caused by a herniated disk compressing a spinal nerve whereas in the latter case the lesion might be caused by entrapment compressing a peripheral nerve (e.g., lateral femoral nerve entrapment at the inguinal ligament).
17. Arterial supply to the superior aspect of the sciatic nerve is provided by the (blank) artery, a branch of the (blank) artery. Be prepared to know the arterial supply to the middle and inferior portions of the sciatic nerve. See Grant's Atlas.
18. Compare the distribution of the superior gluteal artery to the distribution of the superior gluteal nerve.

Essay

1. Reversal of origin and insertion? Discuss the anatomy and function of gluteus medius and minimus.
2. Insertion by way of an intervening tendon from another muscle?
3. Innervation by one nerve (inferior gluteal nerve) but supplied by two arteries (superior and inferior gluteal arteries)?
4. Five short lateral rotators?
5. Discuss why the superior lateral gluteal quadrant is preferable for an injection site relative to each of the remaining 3 quadrants.
6. What structures traverse the lessor sciatic foramen? What are the regions that communicate by way of the lessor sciatic foramen?
7. An injection into the upper medial quadrant of the gluteal region could cause both pelvic sag and foot drop. Explain.

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