Profound Morphometric Analysis of Acetabulum in South Indian Population (Acetabular Dimensions)

Acetabular dimensions plays a challenging role in various arthroplasties and reconstructions. Morphometric study of acetabulum of dry hip bones is a necessity to make proper prosthesis and to ensure good quality of life. Materials & methods

The Acetabulum is known as the vinegar cup.Its deep concavity faces laterally and anteroinferiorly .The cup shape socket forms the hip joint on articulation with the head of a femur which provides stability to the joint .Development of cavity embryologically begins at 4th to 6th week and completion of cavity happens at 8th week of intrauterine life.Triradiate cartilage (immature ischium, ilium and pubis) fuses to form acetabulum.The morphology of acetabulum shows 2 surfaces, a smo oth articulating lunate surface, which has its anterior and posterior end and a rough non articulating part called acetabular fossa covered with a pad of fat. 1,2,3The peripheral moon-shaped articular surface of acetabulum covered by hyaline cartilage and deficient at the inferior margin forms acetabular notch.This gap is bridged by transverse acetabular ligament to form acetabular foramen.Knowledge of morphometry & anatomical framework is necessary to understand the mechanics and enhances the acumen to perform hip arthroplasties. 4,5A joint incongruity may also lead to more dislocation & fractures.So a small change in any parameter of acetabulum leads to anatomical variations.

Aim
The morphometry of acetabular fossa enhances major baseline data for prosthesis construction of acetabulum . 6,7In various hip dysplasia, damage to size and shape of acetabulum parameters are evaluated by applying measurements of acetabular parameters by an orthopedic surgeon.The present study aims to obtain morphometric data of various acetabular parameters which provide data to improve hip arthroplasty.

MATERIALS AND METHODS
A total 71 hip bones of unknown sex were studied from Department of Anatomy of Chettinad Hospital and Research Institute.Out of 71 hip bones, 35 were of right side and 36 were of left side irrespective of age and sex, as these parameters can be included when the bones are derived from a single individual, which gives a precise idea.But, when the collection of bones are from different sources, the authenticity of the determination of sex and age becomes controversial.All the hip bones were fully ossified with intact normal anatomical features.
Specimens with any pathological evidences or damages were not included in the study.Measurements of the parameters were done with the help of digital vernier caliper, twine with measuring scale, plasticine, and urinometer.The parameters taken were vertical diameter, transverse diameter, acetabular notch width, acetabular rim, outer margin, inner margin, depth and capacity.Vertical diameter: Maximum distance measured from the anterior superior iliac spine to prominent point on ischial tuberosity, Transverse diameter: Maximum distance measured on acetabular rim in horizontal axis, Depth: Distance measured from the brim of acetabulum to the deepest point in acetabular fossa with an thin metallic strip of vernier caliper.Acetabular notch: Distance measured from the two end points of lunate with vernier caliper.Acetabular Circumference: Circumference of the acetabular cavity measured over the lip of the acetabulum.Outer rim circumference: Circumference measured around the outer margin of anterior horn of lunate surface to outer margin of posterior horn of lunate surface.Inner rim circumference: Circumference measured around the inner margin of anterior horn of lunate surface to inner margin of posterior horn of lunate surface excluding acetabular notch.Capacity: A solid mass of plasticine was moulded to fill the entire acetabular cup till the circumference of acetabulum including acetabular notch.The excess plasticine after the filling was removed in order to provide proper morphometric evidence of volume of acetabulum.
Then the filled plasticine was taken and submerged in the measuring cylinder which was partially filled with water.So the volume of displaced fluid = volume of immersed object according to Archimedes principle.According to Force of buoyancy submerged volume=volume of object.All these values were analyzed statistically using SPSS software.

RESULTS
The morphometry of acetabulum were measured and tabulated as below with side difference in respective units.

DISCUSSION
Our study would give an elaborate idea of possible parameters in anthropometry of acetabulum of dry hip bone in South Indian population, which provides a strong anatomical knowledge to orthopedic surgeons for enhancing the success rate of hip arthroplasties. 8,9,10,11nthropometry of acetabular fossa is a major baseline data for making hip prosthesis. 12,13ur study accounts for precise morphometric values of the possible parameters measurable in the acetabular cavity.The transverse diameters of acetabulum of right and left side were 49.33 ± 7.36 mm, and 48.57±6.79mmrespectively.The transverse diameter reported by Gursharan, 14 was found to be greater than the same in the present study and quite nearer to value was reported by Archana ,15 47.43±3.43mmand 48.13±3.33mm on right and left sides.The diameter of acetabular cavity on vertical axis was 48.05±4.40mmand 47.66±4.95mmon right and left side respectively.The same diameter as compared with Sridharan, was smaller and statistically significant with p value less than 0.05 on both sides (Table 2). 16n the statistical analysis of the transverse and vertical diameters of acetabulum in our study, there was no significant difference between the parameters of the right and left side.
The depth of acetabulum in present study was 23.28±3.27mmon right side and 22.50 ±3.18mm on left side.Our values were smaller and statistically significant on comparison with the study of Sridharan. 16The comparison of the same with Archana of North Indian population is also statistically significant. 15The cavity depth in the South Indian population ranges from 23mm to 29mm with reference of other similar studies by Gursharan and Yugesh . 14,17The width of acetabular notch of present study was measured as 22.00±3.28mmand 20.56±2.61mm on right and left side.It was found that the findings were again smaller and statistically significant with Sridharan, Archana, and Yugesh as mentioned in [Table 2].
The morphometric knowledge of acetabular rim is very important for labral reconstruction, which is necessary to repair labral tears.In this study the value of acetabular rim measured was 15.26±1.38mmand 14.60±1.35mmon right and left side respectively.Outer rim of acetabulum on right and left side were 11.90±0.99mmand 12.43±0.87mmand the inner rim measured were 7.66±0.84mmand 8.06±0.72mm.This understanding of acetabular rim plays a main role in hip stability, but this parameter was infrequently noted in hip anthropometry studies, that have been done till date.
The volumes of acetabulum in this present study were 27.22±5.43mmand 27.22±5.77mmon right and left side respectively.The study by Gursharan, done by the same method showed a huge difference in volume with a comparatively greater range and significant statistically as well. 14hereby the measured values enhanced by manual method are more accurate than the radiological method as these provide a better understanding for biomedical engineers for modeling the prosthesis as readings are near the real value. 18,19,20,21,22,23

CONCLUSION
This study emphasizes mainly on the detailed knowledge of anatomical parameters of acetabulum which are more important & essential to orthopedic surgeons for various hip surgeries.The depth of acetabular cavity plays an important role in acetabular dysplasia.Acetabular rim parameters were studied in great detail and plays important role in labral reconstructions.The values obtained here are pertaining to a part of South Indian population .These values were very smaller when compared to other races and even other Indian states.
The study has proved the importance of making prosthesis at an individualized level, rather than on a general level.This knowledge of acetabular parameters is essential for anatomist, forensics experts and orthopaedicians to deliver their performances to the maximum in their specialties.

Table 1
show the various results obtained during the study period.The value of acetabulum circumference in this study on right side was 15.26 ± 1.38 cm and left side was 14.60± 1.35 cm.Outer rim circumference

Table 2 .
Comparison table