HIP BONE: osteology, myology, ossification, clinical anatomy.

Bone: hip bone.

Features

• Also called os coxa.
• Large irregular bone with three parts ilium, ishium,pubis.
• These three parts meet at the acetabulum (large deep cavity placed on the lateral aspect of the bone).
• Below and medial to the acetabulum is a large oval or triangular aperture called the obturator foramen.

Side determination.

• Acetabulum faces laterally.
• Ilium directed upward.
• Triangular shaped pubis placed anteriorly.

Osteology

• Consists of three parts ilium,ishium, pubis.

Ilium

• Also called os ilium or flank bone.
• Fan shaped.
• Consists of two borders anterior and posterior, two surfaces medial and lateral and a iliac  crest.

Iliac crest

• Extends from anterior superior iliac spine to posterior superior iliac spine.
• Iliac crest subdivided into ventral segment and the dorsal segment.
• Ventral segment consist of the anterior 2/3rd .
• The whole length of the ventral segment shows a broad intermediate area that is bounded by inner and outer lips.
• The outer lip is most prominent about 5cm behind anterior superior iliac spine,this prominence called tubercle of the iliac crest.
• The inner lip gets obliterated as traced posteriorly.
• The posterior 1/3rd of the iliac crest forms the dorsal segment. It has medial and lateral surface separated by a ridge.

Anterior border

• Extend downwards from the anterior superior iliac spine to the acetabulum.
• Its lowest part present a prominence called the anterior superior iliac spine.

Posterior border

• Extends from posterior superior iliac spine to the back of the acetabulum. Few centimetres below the posterior superior iliac spine the posterior borders presents another prominence called posterior superior iliac spine.
• The lower part of the posterior border curves down to form the boundary of a deep notch called the greater sciatic notch.
• The border joins the posterior border of ischium.

Lateral surface

• Also called gluteal surface.
• The surface contains three ridges called posterior, anterior, inferior gluteal lines.

Posterior gluteal line

• Vertical.
• Extend from the iliac crest above to the posterior inferior iliac spine below.

Anterior gluteal line

• Convex upward and backward.
• Extends from the greater sciatic notch to the iiac crest.

Inferior gluteal line

• Horizontal.
• Extends from anterior superior iliac spine to the posterior end of greater sciatic notch.

• The gluteal surface of the ilium bears a prominent groove just above the acetabulum.
• The lower part of the gluteal surface continues with ilium.

Medial surface

• Has two distinct areas iliac fossa and the sacropelvic surface.
• Iliac fossa : smooth,concave and forms the wall of the greater pelvic surface.
• Iliac fossa occupies anterior part of the medial surface.
• Sacropelvic surface : lies behind the iliac fossa .
• Subdivided into three parts                                                                  # the upper rough part constitute iliac tuberosity.                  # Middle part called auricular surface articulates with the lateral side of sacrum.                                                            #a smooth pelvic part forms the wall of the lesser pelvis.( Preauricular sulcus found in this area).

Medial border if ishium: superior iliac fossa and the sacropelvic surface.

• The border is sharp at the upper part .
• The lower part is rounded and forms the arcuate line.
• At the lower end of the arcuate line, iliopubic eminence can be seen.

Ischium

• L shaped part of the hip bone.
• Evens down from the acetabulum and then passes forward to join the pubis.

Body of the ischium

• The upper part of the body forms the inferior and posterior parts of the acetabulum.
• Ishium also has a projection called ramus surfaces.
• The lower part of the body has three surfaces dorsal,femoral, pelvic.

Dorsal surface

• The lower part of the dorsal surface has a large rough impression called ischial tuberosity.

Ischial tuberosity

• Divided into upper and lower parts by a transverse ridge.
• Each of these divided into medial and lateral parts.
• The upper lateral part gives attachment to semimembranosus muscle and is separated by an oblique line from the upper medial part which gives allachment to the semitendinosus and biceps femoris.
• The lower lateral part gives attachment to the hamstring part of the adductor Magnus.
• The lower medial part is covered by fibrous tissue and usually have an overlying bursa.

Femoral surface

• Directed downwards, foreward and laterally.
• Continuous with the external surface of the ramus of the ischium.

Pelvic surface

• Smooth and forms the wall of the pelvis.
• The ramus of the ischium has two surfaces anterior and posterior.
• The ramus of the ischium joins with the ramus of the pubis to form ischio pubis ramus.

Pubis

• Forms the antroinferior part of the hip bone near the midline.
• Consist of body superior ramus and inferior ramus.

Body of the pubis

• Forms anterior and medial parts.
• It has anterior surface and posterior surface .
• The upper border of the body forms a prominent ridge called pubic crest.

Superior ramus

• Attached to upper and lateral part of the body.
• It's lateral extremity takes part in the formation of pubic part of the acetabulum.
• Triangular in cross section has 3 borders and 3 surfaces.
• Anterior border : also called obturator crest.
• Posterior border: sharp, forms pectineal line.
• Inferior border : sharp ; forms the upper margin of the obturator foramen.
• Pectineal surface: lies between obturator crest and pectineal line.
• Pelvic surface : lies between obturator crest and the inferior border.
• A groove runs foreward and downward across it and is called the obturator groove.

Inferior ramus

• Attached to the lower lateral part of the body of the pubis.
• Inferior ramus of the pubis and the ramus of the ischium together called ishiopubic ramus.
• The inferior ramus of the pubis has an anterior surface and a posterior surface.

Acetabulum

• Deep cup like cavity situated on the lateral aspect of the hip bone.
• It forms the hip joint with the head of the femur.
• Directed laterally, downwards and forwards.

• The floor of the acetabulum is partially articular and partially non articular.
• The articular area for the head of the femur is shaped like a horse shoe and is called lunate surface.
• The inner border of the lunate surface forms the margin of the non articular part of the floor which is called acetabular fossa .

Obturator foramen

• Triangular space surrounded by the bodies and Rami of the pubis and ishium.
• The intact body,the foramen is filled by a fibrous sheet called obturator membrane.

Myology
Muscle attached to iliac crest

• External oblique muscle: inserted into the anterior 2/3rd of the outer lip of the ventral segment of the iliac crest.
• Internal oblique muscle : arises from the intermediate area of the ventral segment of the iliac crest .
• Lattisimus dorsi : originates from the outer lip of the iliac crest just behind its highest point.
• Tensor fascia Lata : originates from the anterior part of the outer lip of the iliac crest.
• Transverse abdominis: arises from the anterior 2/3rd of the inner lip of the ventral segment of the iliac crest.
• Quadrature lumborum: arises from the posterior 1/3rd of the inner lip of the ventral segment of the iliac crest.
• Gluteus maximus: arises from the lateral surface of the dorsal segment of the iliac crest .
• Erector spinae: arises from the medial surface of the dorsal segment of the iliac crest.

Muscle attachment to the external aspect of the hip bone.

• Gluteus maximus :arises from the gluteal surface of the ilium behind the posterior gluteal line.
• Gluteus medius: arises from the posterior surface of the ilium between the anterior and posterior gluteal lines.
• Gluteus minimus: arises from the gluteal surface of the ilium behind the anterior and inferior gluteal line.

• Rectus femoris: arises from anterior inferior iliac spine .
• Piriformis : arises from the upper border of the greater sciatic notch near the posterior inferior iliac spine.
• Rectus abdominis: originates from pubic crest.
• Pyramidalis and adductor Longus : originates from the anterior surface of the body of the pubis.
• Gacilis: originates from the anterior surface of the body and the inferior ramus of the pubis and from the ramus of the ischum.
• Adductor brevis : originates from the anterior surface of the body of the pubis and it's inferior ramus, lateral to the origin of the gracilis.
• Obturator externus: originates from the superior and inferior rami of the pubis and forms the ramus of the ischum.
• Adductor Magnus: originates from the lower part of the ischial tuberosity and from the ramus of the ischum.
• Semitendinosus and biceps femoris : originates from the upper medial part of the ischial tuberosity.
• Semimembranosus : originates from the upper lateral part of the ischial tuberosity.
• Quadratus femoris: originates from the femoral surface of the ischum just lateral to the ischial tuberosity.
• Superior gemellus : arises from the dorsal surface of the ischial spine.
• Inferior gamellus: arises from the ischum just above the ischial tuberosity.

Muscle attached to the internal aspect of the hip bone.

• Psoas minor: inserted into pectineal line.
• Iliacus: arises from the upper 2/3rd of the iliac fossa.
• Obturator internus: arises from the pelvic surface of the superior and inferior rami of the pubis and ramus of the ischum , immediately adjoining the obturator foramen and from the pelvic surface of the ischum and of the ilium.
• Levator ani: arises from the pelvic surface of the ischial spine and its most anterior fibres form  the posterior surface of the body of the pubis.
• Coccygeus: arises from the pelvic surface of the ishial spine.

Greater and lesser sciatic foramen.

The greater sciatic foramen transmitted the following structures.

• Piriformis
• The superior and inferior gluteal nerves and vessels.
• Internal pudendal vessels.
• The pudendal and sciatic nerves.
• Posterior cutaneous nerve of the thigh.
• The nerves to obturator internus and quadratus femoris.

Ossification

• Ossifies before birth from three primary centres each for ilium, ishium and pubis.
• The centres appearing in intrauterine life are as follows :.  *For ilium- above the greater sciatic notch in the 8th week.                                                                                              *For ischum- below the acetabulum in the 4th month.

       *For pubis - In the superior ramus in the 4th or 5th month.

• At birth ilium, ishium and pubis are separated by a Y-shaped cartilage present in the region of the acetabulum.
• The three parts fuse completely only after the age of 18 years.
• The inferior ramus of pubis and the ramus of the ischium are at first fused at the age of 7 years.
• The secondary centres appear at the age of 20-25 years.
• Two of them appear at the iliac crest and two if them at acetabular cartilage and occasional centres in the anterior inferior iliac spine and lower part of the acetabulum, the pubic tubercle and the pubic crest.