Lower limb anatomy (pelvis) + intro to spine

Question 1

The pelvis

Answer 1

The pelvic girdle is made up of two hip/innominate bones / hemipelvis

Separated posteriorly by sacrum and anteriorly at symphysis pubis

Bony ring, strongly held by extensive ligamentous complex

Each comprised of three parts:
Ilium (iliac bone)
Ischium
Pubis

In regional / soft tissue anatomy is split into two parts:
False/greater pelvis; superior and part of abdomen
True/lesser pelvis; inferior and has an inlet and outlet

Oblique line from symphysis pubis to sacral promontory (l5s1)

For msk purposes this is less significant

Question 2

Pelvic inlet/outlet

Answer 2

Ring-shaped structures within true pelvis

Inlet:
superior
Circular/heart-shaped bony ring
Junction between abdomen/pelvis
Angled 50-60 degrees to coronal plane

Outlet:
Inferior
Diamond-shaped bony/ligamentous
Junction between pelvis and perineum (pelvic floor)
Anterior formed by inferior pubic rami, posterior by ligaments
Horizontal plane

Question 3

What are the functions of the pelvis?

Answer 3

bearing the weight of individuals superior to the pelvis, stabilizing them, and allowing them to sit and stand as the legs located inferiorly move.

Question 4

The hip bones / hemipelvis

Answer 4

Also called innominate bones

Paired bones (useful in image interpretation)

Comprised of 3 primary ossification centres (parts):
Ilium (not ileum)
Ischium
Pubis

Formed separately but fuse in adolescence (15-25)

Question 5

Ossification centres

Answer 5

Primary:
Ilium (8th week in utero)
Ischium (4 months)
Pubic (4-5months)

Secondary (common sites for avulsion) fracture):
Ilium: iliac crests and aiis (puberty)
Ischial tuberosity (PubERTY)
Symphysis pubis (puberty)

Fusion between ~15-25 years

Question 6

Iliac bone / ilium

Answer 6

Medial aspect adjoins abdomen, lateral is lower limb (relates to origin of structures)

Fan-shaped

Key features/soft tissue attachments:
Iliac crest/tubercle
Iliac fossa (internal)
Gluteal surface (external)
Anterior superior iliac spine (ASIS)
Posterior Superior ILIAC spine (PSIS)
Anterior inferiors iliac spine (AIIS)
Superior rim of acetabulum

Question 7

Ilium attachments

Answer 7

Iliac crest – quadratus lumborum/transversus abdominus
Iliac fossa – iliacus
Gluteal surface – gluteus medius/minimus
ASIS – Sartorius
AIIS – rectus femoris

Question 8

ischium

Answer 8

Postero-inferior part of the pelvic bone

Forms large part of obturator foramen and acetabulum

Ischial tuberosity origin for hamstring muscles

Ischial spine – attachment site

Question 9

Pubic bone

Answer 9

infero-anterior part of the pelvic bone

C-shaped, body and superior and inferior pubic rami

body flattened medially to form symphysis pubis

Pubic tubercle insertion for inguinal ligament

Forms obturator foramen with inferior ischium

Primary attachment for adductor muscle group

Question 10

SYMPHYSIS PUBIS

Answer 10

Cartilaginous joint between left and right pubic bones – function??

Articular surfaces covered by hyaline (articular) cartilage

Joined by fibrocartilage

More movement in women than men, changes related to pregnancy/post-partum

Question 11

The hip joint

Answer 11

Synovial joint

Ball-and-socket between femoral head and acetabulum

Designed to be strong and stable (in comparison to other joints)
Relatively limited movement (when compared to shoulder)

Movements:
Flexion/extension
Abduction/adduction
Internal-external rotation
circumduction

Question 12

acetabulum

Answer 12

Formed by combination of ilium, ischium, and pubic bones

Large-deep cup surrounds femoral head

Deepened by rim of fibrocartilage called labrum

Peripheral articular surface covered by hyaline cartilage; thickest superiorly – why?

Central acetabular fossa is roughened attachment point

Inferior notch allows passage of neurovascular structures

Question 13

Proximal femur

Answer 13

Characterised by four structures (OSSIFICATION CENTRES):
Femoral head (articular surface)
FEMoRAL NECK (metaphysis)
Greater and lesser trochanters

Prone to clinically significant fractures with high levels of morbidity/mortality

Question 14

OSSIFICATION CENTRES

Answer 14

Primary:
Diaphysis/shaft (8th week in utero)

Secondary:
Epiphysis /femoral head (6 months)
Greater trochanter (4 years)
Lesser trochanter (13 yearS)

Fusion between ~16-18 years

Question 15

Femoral head

Answer 15

Femoral head round and smooth, covered with articular cartilage

Central depression called fovea capitis; attachment for ligamentum teres

variable minimal blood supply to femoral head through this fovea; important in fractures

Question 16

Femoral neck

Answer 16

Approximately 125 degree angle with diaphysis

Slight anterior angulation

Intra-capsular

Tensile/compressive trabecular pattern

Important to diagnose fractures here

Question 17

Trochanteric region

Answer 17

Great trochanter laterally:
extends anteriorly and posteriorly
Several ridges and depressions for attachments
Gluteus medius/minimus, obturator and gemelli muscles

Lesser trochanter postero-medially:
Tendon of psoas and iliacus muscles

Inter-trochanteric line (anteriorly) and crest (posteriorly)

Question 18

The hip joint

Answer 18

Surrounded by synovial membrane

Capsule Extends distally to base of neck of femur (intra-capsular)

Covered by strong fibrous joint capsule

Reinforced by 3 sets of ligaments from 3 parts of pelvic bone

Question 19

Blood supply

Answer 19

complex blood supply

Majority comes from branches from the femoral artery

Inserts at base of neck and extends proximally into head

Key principle behind hip fracture management; risk of avascular necrosis

Question 20

the femur

Answer 20

Long bone:
Epiphysis (x2)
Metaphysis (x2)
Diaphysis

Other Bony features proximally (hip) and distally (knee)

Strongest/longest in the skeleton

Diaphysis very strong; relatively rarely fractured without significant trauma/pathology

Question 21

FEMORAL DIAPHYSIS

Answer 21

Main feature is the linea aspera (rough line) posteriorly

Ridge along posterior diaphysis

Major site of muscle attachment; adductors

Question 22

musculatur

Answer 22

compartments plus accessory muscles

Anterior (quadriceps femoris):
Vastus medialis, intermedius, lateralis
Rectus femoris

Medial (adductors):
Adductor magnus, longus,brevis
pectineus
Gracilis

Posterior (hamstrings):
Biceps femoris (Long/short head)
Semimembranosus
semitendinosus

Question 23

Neurovascular structures

Answer 23

Large vascular and nervous structures

Femoral artery, vein, and nerve

Sciatic nerve runs between hamstrings

Significant role in high velocity injuries