Anatomy of the Acetabulum

Dr Zahid AskarMBBS, FCPS(Ortho),FRCS(Tr & Ortho)

Prof. of OrthopaedicsKhyber Medical College

Peshawer

• Acetabulum (Gr: ὀξίς, ὀξύβαφον, ὀξυβάφιον) was a vinegar-cup, used by Greeks and Romans placed on the dining-table .

• The acetabulum is the point where the three components of the pelvis (ilium, ischium, and pubis) meet.

The articular Lunate Surface/DOME

The nonarticular AcetabularFossa

The inferior AcetabularNotch.

Anatomical restoration of the dome with concentric reduction of the femoral head beneath this dome is the goal of both operative and nonoperative treatment.

Embryology

• At 4 to 6 gestational weeks, the hip joint develops from the cartilaginous analogue -

• By 7 weeks a cleft appears

• By 11 weeks, hip joint formation is mostly complete

• At late gestation, femoral head grows more rapidly

• At birth the femoral head is < 50% covered

• Acetabulum continues to grow till 7 years with maximum growth is in the first 4 years.

ASIS

AIIS

Ischial Tuberosity

PubisIschial Spine

tendon of obturator internus m.

internal pudendal a.

internal pudendal v.

pudendal n.

nerve to obturator internus

- 7 nerves:- Sciatic Nerve- Superior Gluteal Nerve- Inferior Gluteal Nerve- Internal Pudendal Nerve:- Posterior Femoral Cutaneous Nerve- Nerve to Quadratus Femoris- Nerve to Obturator Externus

- 3 Vessel Sets:- Superior Gluteal Artery & Vein- Inferior Gluteal Artery & vein- Internal Pudendal Artery & vein

- 1 Muscle:- Piriformis

Forces Across The Hip Joint

• Walking upto 4 times BW

• Running upto 7 times BW

• Supported gait (w/ a walker or a cane) 2-3 BW

Wednesday, December 17, 2014

8

Supine straight leg raising 2 times BW.Getting on & off bed pan 4 times BWJogging and very fast walking both raised the forces to about 5.5 BW.Stumbling on one occasion caused magnitudes of 7.20 BW

1. promontory of sacrum2. ala of sacrum3. arcuate line of ilium4. pecten pubis (pectineal line)5. pubic crest6. pubic symphysis

Iliopectineal lineThe iliopectineal line is the border of the iliopubic eminence. It can be defined as a compound structure of the arcuate line and pectineal line. With the sacral promontory, it makes up the linea terminalis

Iliopubiceminence (or iliopectinealeminence), which marks the point of union of theilium and pubis

Ant. Column

The two Columns

Post. ColumnAcetabulum

These two columns serve as struts, mechanically representing the coalescence of bony trabeculae along lines of stress

Anterior Column (white)

Consists of

• Anterior half of the Iliac crest,

• The Iliac spines,

• Anterior half of the acetabulum, and the pubis. ;

Posterior Column(red)

• Consists of:

• Ischium,

• the ischial spine,

• the posterior half of the acetabulum,

• the dense bone forming the sciatic notch.

• The posterior column ends at its intersection with the anterior column at the top of the sciatic notch

Post

Post

3D Anatomy of the Innominate Bone

Anterior

AcetabulumMean lateral inclination of 40 to 48 degrees

Anteversion of 18 to 21 degrees

G. Maximus

G. Medius

G. Minimus

Quadratus

• Sciatic Nerve

• Superior/Inf Gluteal N.V Bundle

• Corona mortis

Sciatic Nerve

• The largest and longest nerve in the body

• Arises from the lumber and sacral plexus

• Comes out of the pelvis through the Sciatic Notch

• Runs anterior (deep) to Piriformis and lies posterior (superficial) to the short external rotators

Leaves pelvis through the greater sciatic notch along-with superior gluteal artery and veinIt runs over the piriformisbetween the gluteus mediusand minimus supplying these muscles

Superior Gluteal Nerve

Do not split gluteus mediusmore than 5-7 cm proximal to greater trochanter due to risk of denervating the muscle at risk during the lateral (Hardinge) approach to the hip

Leaves the pelvis through the greater sciatic foramenRuns underneath the piriformisDivides into muscular branches to supply the Gluteus Maximus

Inferior Gluteal Nerve

From the front

Vessels near the Acetabulum

Schematic showing the excessively long screws on the quadrilateral intrapelvic surface relative to the iliac arterial system.

corona mortis

"corona mortis" or crown of death Chances of significant hemorrhage

An anastomosis between the obturator and the external iliac or inferior epigastric arteries or veins.

Located behind the superior pubic ramus at a variable distance from the symphysis pubis (range 40-96 mm). 60% had a large diameter (>3 mm)

“We carried out forty cadaver dissections (80 hemi-pelvises) through the ilioinguinal approach. A vascular anastomosis was found in 83% of specimens. Of these, 60% had a large diameter (>3 mm) channel along the posterior aspect of the superior pubic ramus”

“In clinical practice, however, 492 anterior approaches (to the best of our knowledge the largest series described) have been carried out over the last 15 years by the senior author (MB) and only five of these problematic vessels were discovered, and in only two cases was there troublesome bleeding. “

Darmanis S, Lewis A, Mansoor A, Bircher MCorona mortis: an anatomical study with clinical implications in approaches to the pelvis and acetabulum.Clin Anat. 2007 May;20(4):433-9.

Where to put the screws???

•Thank You !!!