Acetabulum anatomy

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Anatomy of the AcetabulumDr Zahid AskarMBBS, FCPS(Ortho),FRCS(Tr & Ortho)Prof. of OrthopaedicsKhyber Medical CollegePeshawer

1Acetabulum(Gr:,,) was avinegar-cup, used by GreeksandRomans placed on the dining-table .

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

The articularLunate Surface/DOMEThe nonarticular Acetabular FossaThe inferior Acetabular Notch. Anatomical restoration of the dome with concentric reduction of the femoral head beneath this dome is the goal of both operative and nonoperative treatment.

EmbryologyAt 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 rapidlyAt birth the femoral head is < 50% coveredAcetabulum continues to grow till 7 years with maximum growth is in the first 4 years.

ASISAIISIschial TuberosityPubisIschial 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 toQuadratus Femoris - Nerve to Obturator Externus- 3 Vessel Sets: -Superior Gluteal Artery & Vein -Inferior Gluteal Artery& vein - Internal Pudendal Artery & vein- 1 Muscle: -PiriformisForces Across The Hip JointWalking upto 4 times BW Running upto 7 times BW Supported gait (w/ a walker or a cane) 2-3 BWTuesday, December 16, 20148Supine 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 terminalisIliopubic eminence(oriliopectineal eminence), which marks the point of union of theiliumandpubis

Ant. ColumnThe two Columns

Post. ColumnAcetabulum

These two columns serve as struts, mechanically representing the coalescence of bony trabeculae along lines of stressAnterior Column (white)Consists ofAnterior 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



3D Anatomy of the Innominate Bone

AnteriorAcetabulumMean lateral inclination of 40 to 48 degrees

Anteversion of 18 to 21 degrees

G. MaximusG. Medius

G. MinimuspiriformisQuadratusSciatic NerveSuperior/Inf Gluteal N.V BundleCorona mortis

Sciatic NerveThe largest and longest nerve in the bodyArises from the lumber and sacral plexusComes out of the pelvis through the Sciatic NotchRuns anterior (deep) toPiriformis 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 piriformis between the gluteus medius and minimus supplying these muscles

Superior Gluteal Nerve

Do not split gluteus medius more than 5-7 cm proximal to greater trochanter due to risk of denervating the muscle at risk during the lateral (Hardinge) approach to the hipLeaves the pelvis through the greater sciatic foramenRuns underneath the piriformisDivides into muscular branches to supply the Gluteus MaximusInferior 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 ramusIn 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 MCoronamortis: 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 !!!