A 30-year-old man is evaluated for 6 months of persistent pain in his right buttock and posterior thigh. He is a construction worker and has difficulty lifting heavy objects or climbing stairs. He has no history of back injury and no associated back pain. Past medical history is unremarkable. The patient does not use tobacco and drinks only moderate quantities of alcohol. On examination, the patient develops pain with forced adduction of the flexed thigh and internal rotation of the extended thigh against resistance. Further evaluation reveals possible entrapment of the sciatic nerve in the greater sciatic foramen. Which of the following structures passes through the foramen and occupies most of its volume?

Question

A 30-year-old man is evaluated for 6 months of persistent pain in his right buttock and posterior thigh.  He is a construction worker and has difficulty lifting heavy objects or climbing stairs.  He has no history of back injury and no associated back pain.  Past medical history is unremarkable.  The patient does not use tobacco and drinks only moderate quantities of alcohol.  On examination, the patient develops pain with forced adduction of the flexed thigh and internal rotation of the extended thigh against resistance.  Further evaluation reveals possible entrapment of the sciatic nerve in the greater sciatic foramen.  Which of the following structures passes through the foramen and occupies most of its volume?

Quizplus · Accepted Answer

11ec160b_35f2_5dc2_9249_951e77e03f99_MD0001_00 The sciatic foramen is a pelvic opening serving as the major pathway for pelvic neurovascular structures to the lower limbs. It is divided into greater and lesser sciatic foramina by the sacrospinous ligament (Choice E). The greater sciatic foramen is bordered anterolaterally by the greater sciatic notch of the ilium, inferiorly by the ischial spine and sacrospinous ligament, superiorly by the anterior sacroiliac ligament, and posteromedially by the sacrotuberous ligament (Choice F). The piriformis originates on the anterior aspect of the sacrum and occupies most of the space in the greater sciatic foramen. It inserts on the greater trochanter of the femur and acts to externally rotate the thigh when extended and abduct the thigh when flexed. Structures running above the piriformis include the superior gluteal vessels and superior gluteal nerve. Structures crossing below the piriformis include the inferior gluteal vessels, internal pudendal vessels, and multiple nerves (most notably the sciatic nerve). Muscle injury or hypertrophy can compress the sciatic nerve to cause sciatica-like symptoms (eg, pain, tingling, and numbness in the buttocks and along the nerve distribution) known as piriformis syndrome. The muscle can be tender with deep palpation or on stretching with adduction and internal rotation. (Choice A) The coccygeus muscle is a pelvic floor muscle anterior to the sacrospinous ligament and combines with the levator ani to form the pelvic diaphragm. (Choice B) The gluteus minimus is the smallest of the 3 gluteal muscles and is immediately beneath the gluteus medius. It works with the gluteus medius to stabilize the hip and abduct the thigh when the limb is extended. (Choice C) The obturator internus is a fan-shaped muscle originating from the medial surface of the obturator membrane, ischium, and pubic rim. It exits the pelvis through the lesser sciatic foramen and inserts on the greater trochanter of the femur, where it functions similarly to the piriformis. Educational objective: The piriformis passes through the greater sciatic foramen and is involved with external hip rotation. Muscle injury or hypertrophy can compress the sciatic nerve in the foramen, causing piriformis syndrome. __________ References: Piriformis syndrome: a cause of nondiscogenic sciatica. (http://www.ncbi.nlm.nih.gov/pubmed/25574881)

A 30-Year-Old Man Is Evaluated for 6 Months of Persistent