CHAPTER 34: Overview of the Lower Limb

BONES OF THE PELVIC REGION AND THIGH

BIG PICTURE

The bones of the skeleton provide a framework that serves as an attachment for soft tissues (e.g., muscles). The bony structure of the gluteal region and thigh, from proximal to distal, consists of the pelvis, femur, patella, tibia, and fibula (Figure 34-1A). Synovial joints and fibrous ligaments serve to connect bones together.

PELVIC AND THIGH BONES

THE PELVIS

The pelvis consists of right and left pelvic bones and has the following properties (Figure 34-1A and B):

• Articulations. The pelvic bones articulate posteriorly with the sacrum via the sacroiliac joints, and anteriorly with each other at the pubic symphysis.

• Constituents. Each pelvic bone consists of three bones: ilium, ischium, and pubis.

• Acetabulum. A large cup-shaped structure at the junction where the ilium, ischium, and pubis fuse. The acetabulum protrudes laterally for articulation with the head of the femur bone.

• Obturator foramen. An opening formed by the ilium, ischium, and pubis.

ILIUM

The ilium is the most superior and the largest bone of the three components of the pelvis.

• Iliac fossa. Attachment site for the iliacus muscle.

• Iliac crest. A prominent, palpable crest between the ASIS and PSIS where numerous body wall and limb muscles attach; possesses a large amount of red bone marrow and thus an ideal harvest site to collect stem cells in bone marrow transplant surgery. Additionally, the iliac crest marks the L4 vertebral level.

• Anterior superior iliac spine (ASIS). Attachment site of the inguinal ligament, sartorius muscle, and tensor fascia latae muscle.

• Anterior inferior iliac spine (AIIS). Attachment site for the rectus femoris muscle.

• Posterior superior iliac spine (PSIS). Attachment site for sacroiliac ligaments and the multifidus muscle; forms the dimples in the skin immediately superior and lateral to the gluteal cleft.

• Posterior inferior iliac spine (PIIS). Attachment site for ligaments.

ISCHIUM

The ischium is the posterior and inferior component of the pelvic bone.

• Ischial tuberosity. A large tuberosity on the posteroinferior aspect of the ischium where the hamstring and adductor magnus muscles and sacrotuberous ligament attach. Covered by the gluteus maximus when standing but uncovers them when sitting; when sitting the weight is placed upon the ischial tuberosities.

• Ischial ramus. Projects anteriorly to join with the inferior ramus of the pubis; serves as attachment site for muscles.

• Ischial spine. A prominent spine that separates the lesser sciatic notch from the greater sciatic notch; serves as a site for muscle attachment and landmark for giving a pudendal nerve block.

PUBIS