Pelvic Girdle and Femur Anatomy

Surface Anatomy of the Pelvic Girdle and Femur

• Bony landmarks aid in physical exams and surgery.
• They help evaluate development, detect fractures/dislocations, and locate structures like nerves and blood vessels.

Pelvic Girdle

• The pelvic girdle is a ring-like bony structure in the lower trunk which connects axial skeleton to the lower limbs.
• Components are 2 hip bones, sacrum, and coccyx.
• Articulations include 2 sacroiliac joints, sacrococcygeal symphysis, and pubic symphysis.
• Ligaments stabilize by attaching the sacrum's lateral border to bony pelvis landmarks.

Functions of the Pelvis

• Supports weight transfer from the upper axial skeleton.
• Provides attachment for muscles/ligaments for locomotion.
• It contains and protects abdominopelvic and pelvic viscera.

Greater and Lesser Pelvis

• The pelvic region divides into greater (false) and lesser (true) pelvises.
• The greater pelvis is located superiorly and supports abdominal viscera with little obstetric relevance.
• The lesser pelvis is located inferiorly and houses the pelvic cavity and viscera.
• The pelvic inlet marks the junction between greater and lesser and its outer edges make up the pelvic brim.

Pelvic Inlet

• The pelvic inlet's size is defined by the pelvic brim.
• The borders of the pelvic inlet are the sacral promontory, sacral wings, arcuate line, pectineal line, and pubic symphysis.
• The pelvic inlet determines the birth canal's size and shape, serving as a key attachment site.
• The Linea terminalis is the combined pectineal line, arcuate line, and sacral promontory.
• The Iliopectineal line is the combined arcuate and pectineal lines, representing the lateral border of the pelvic inlet.

Pelvic Outlet

• The pelvic outlet is located at the end of the lesser pelvis and the beginning of the pelvic wall.
• Its borders consists of: tip of coccyx (posterior), ischial tuberosities, sacrotuberous ligament (lateral), and pubic arch including ischiopubic rami (anterior).
• The angle beneath the pubic arch is the sub-pubic angle, greater women.

Gynaecoid vs Android Pelvis

• Most women have a gynaecoid pelvis, unlike the male android pelvis.
• The gynaecoid pelvis creates a greater pelvic outlet aiding childbirth
• Gynaecoid pelvic characteristics: Wider, broader, lighter / Oval-shaped inlet / Less prominent ischial spines / Greater sub-pubic arch angle (80-90 degrees) / Shorter, more curved sacrum / Less pronounced sacral promontory
• Progesterone allows sacrotuberous and sacrospinous ligaments to stretch to increase outlet size.

Female Bony Pelvis Assessment

• The lesser pelvis is the bony canal through which the fetus passes during childbirth.
• The diameter is determined by pelvic examination or radiographically, assessing the birth canal.

Obstetric Conjugate

• Minimum anteroposterior diameter of the pelvic inlet is measured to determine the narrowest fixed distance.
• This distance goes from sacral promontory to the midpoint of pubic symphysis, or obstetric conjugate.
• This cannot be clinically assessed due to the bladder's presence.

Diagonal Conjugate

• An alternative is the diagonal conjugate which is the distance from the inferior border of the pubic symphysis to the sacral promontory and it can be measured manually via the vagina.
• Use the middle finger to measure from sacral promontory.
• Mark the level of inferior margin of the pubic symphysis, then find the distance with index finger to the pubic symphysis to measure the diagonal conjugate, (ideally 11cm or greater)
• Clinicians check and measure the bispinous diameter via a mid-pelvis to test for straight side walls which is the narrowest part of the pelvic canal.
• The subpubic angle width in the pelvic outlet is determined by the distance between ischial tuberosities.

Iliac Crests

• When hands are on hips, they rest on iliac crests.
• The anterior third is easily palpated due to being subcutaneous.
• The posterior two thirds are hard to palpate because they are covered with fat.

Iliac Tubercle

• Marks the widest point of the iliac crest, 5-6 cm posterior to the ASIS.
• Palpate by placing the thumb on ASIS and fingers along external lip.
• The iliac tubercle lies at the L5 vertebra's spinous process.

Anterior Superior Iliac Spine

• The iliac crest ends anteriorly at the rounded ASIS, which is easily palpated by tracing the iliac crest antero-inferiorly.
• The ASIS is often visible in thin individuals.
• However, they are easier to palpate when the person is sitting if covered with fat

Pubic Bones/Symphysis

• Located with approximately a hand's width inferior to the umbilicus.
• The pubic tubercle can be palpated 2 cm from the pubic symphysis at the anterior pubic crest extremity.

Posterior Superior Iliac Spine

• The iliac crest terminates posteriorly at the PSIS which is hard to palpate
• The PSIS is found easily because it's at the bottom of a skin dimple, approximately 4 cm lateral to the midline.

PSIS Dimple

• The dimples are present because the skin and underlying fascia are attached to the PSIS.
• Skin dimples serve as landmarks for palpating the sacroiliac joints to check for edema.
• They indicate the iliac crests' termination, bone marrow, and bone grafts obtained can repair a fractured tibia.

Ischial Tuberosity

• The ischial tuberosity is easily palpated when thigh flexed and is covered with buttocks.
• The buttocks cover and obscure the tuberosity when the thigh is extended.
• The gluteal fold coincides with the fat pad associated with the inferior border of the gluteus maximus, indicating separation of the buttocks from the thigh.

Femoral Head

• Palpate the femoral head at a point approximately a thumb's breadth inferior to the midpoint of the inguinal ligament between the ASIS and pubic tubercle.
• Only the superior and inferior ends of the femur are palpable because the shaft of the femur which is usually covered with muscles.

Greater Trochanter

• Located laterally, projecting superior to the junction of the shaft with the femoral neck.
• The prominence is anterior and the hollow is on the lateral side of the buttocks which forms the wider part of the adult pelvis
• The posterior edge of the greater trochanter is easily palpated when the limb is not weight bearing.

Parts of the Trochanter

• The anterior/lateral trochanter parts are hard to palpate due to fascia and muscle cover.
• It causes discomfort on hard surfaces because of its proximity to the skin
• Anatomically, a line joining the greater trochanter tips normally passes through the pubic tubercles and center of femoral heads.
• The lesser trochanter is indistinctly palpable superior to the lateral end of the gluteal fold.

Femoral Hernia

• A hernia is an organ bulge through a structure or muscle that usually contains it.
• The femoral hernia originates in the femoral ring
• The femoral hernia appears as a lump or mass in the femoral triangle just inferior to the inguinal ligament and lateral to adductor longus. A loop of the small intestine protrudes through the femoral ring enters into the femoral canal.