Differences in the parameters of bone and anatomical variations of the hip joint do exist among different races. The development of computed tomography has helped in further detailed anatomic study of the hip Joint. Tomographic study of pediatric hip has been reported mainly for detection of dislocation/subluxation or when measurement of femoral torsion and acetabular anteversion are needed12
. We used CT scan to make a quantitative analysis of all the parameters of adult hip joint in our study. Our method is a collection of various parameters and their methods of measurement described by several authors.2,3,8–11,13–17
The CE angle was first described by Wiberg (1939)6
and subsequently by many authors.6,10,11
Values of >25° are considered normal whereas values < 20° are considered dysplastic. The CE angle of Wiberg studied in an adult Indian population by Mandal et al
found that in 83% the CE angle was between 28° and 42°. None of the hips had a CE angle of less than 20°, a similar pattern was seen when compared with Africans and Caucasians. Osteoarthritis is rare in Africans and Indians and fairly common in Caucasians. The finding of similar acetabular measurements in adult hips in these three races suggests that acetabular dysplasia may not have a significant role in the development of osteoarthritis.18
In our series the mean CE angle is 32.7° (range = 20°-60°; SD 8.9°). The CE angle was significantly higher (P
= 0.002) in Caucasoids than the mongoloids, however, we are unable to correlate whether this higher value of CE angle in Caucasoid has an influence in the predisposition to osteoarthritis, as no study on the prevalence of osteoarthritis among the ethnic groups of NE region is currently available.
The acetabular angle was first described by Sharp.9
Acetabular angle is frequently used to determine the presence of dysplasia, values of >43° are considered dysplastic. Stuberg and Harris reported a mean acetabular angle of 32.2° in white males and 32.1° in white females respectively.19
Nakamura et al
. reported a mean of 38° and a standard deviation of 3.6° in the Japanese population.20
In the present series we have found a mean acetabular angle of 39.2° (range = 30°-50°; SD 4.9°).
The femoral neck shaft angle has been examined by several authors and most authors agree that there is considerable individual variation and wide standard deviation in this angle. Hoaglund and Low stated that the average neck shaft angle in adults is 135°.21
Lequesne et al
. found a standard deviation of 4.37°, the mean value was 132.8° in their study.2
In our series the mean was 139.5° (range = 118°-150°; SD 7.5°) and was several degrees more than the others. The neck shaft angle showed the highest variation when compared with the western literature and also between the Mongoloids and Caucasoids. Statistically significant variation was observed between the left and right side only (P
The acetabular version was measured by Reikeras et al
., they compared the measurements among normal and in osteoarthritic hip. The normal mean and standard deviation were 17°and 6°, respectively. They found no difference in mean of the acetabular angle in normal and osteoarthritic individuals.22
In the present study we have found an average of 18.2° (range = 8°-40°; SD 5.6°).
The femoral neck anteversion has been measured by various authors using plain radiograph/CT scan, clinically, as well as on dry specimens.14,22,23
The literature has suggested that the measurement on CT scan is more accurate than on X-rays.14,23
Hoaglund and Low21
in 1980 did a cadaveric study in Caucasians and Hong Kong Chinese, the results obtained were as follows. In Caucasians: Male 14° (4°-36°), Female 16° (7°-28°). In Hong Kong Chinese: males 14° (4°-36°) and 16° in females (7°-28°). Reikeras et al
. measured the femoral neck anteversion (FNA) in normal and in osteoarthritic hip with CT scan and found it to be 13° with a standard deviation of 7° in the normal. In osteoarthritic hip they found an average of 6° more than the normal average.22
Jain et al
. calculated femoral anteversion in dry specimens, as well as living persons using clinical, CT and biplane radiograph. They found CT to be accurate on living subjects, the mean FNA with the CT method was 7.4° (SD 4.6°).23
They also made a comparison between preoperative, clinical and biplane X-ray methods and found that the angle of anteversion of the neck of femur in humans exhibits a wide range (−25° to +50°) with the mean angle varying from 8° to 25°. They concluded that the hip joints of the Indian population would be evolutionally different from their Western counterparts, since our population is more apt to floor level activities with increased external rotation of the hip.24
Nagar et al
. concluded from their study on adult Indian dry femora and normal subjects that average anteversion in male bones is greater and right-left variations exist, being greater on the right side.25
On clinical assessment they found a similar pattern. In our series the mean femoral neck anteversion was found to be 20.4° (range = 8°-45°; SD 8.6°). The mean in our series was more than most of the other series that we compared. Moderately decreased femoral neck anteversion (10°-14°) was observed in two hips.
The acetabular depth has been regarded by many authors as an important measurement to define acetabular dysplasia.5,17
An acetabular depth of less than 0.9 cm is considered dysplastic. We found a mean acetabular depth of 2.5 cm (range = 1.4-5.6 cm; SD 0.8 cm). Significant variation in the acetabular depth was observed among the Caucasoids and Mongoloids (P
= 0.001); however, the mean values of acetabular depth was identical when comparison was made between right side: 2.5 cm (1.4-5.6 cm) and left side: 2.5 cm (1.4-5.6 cm), identical values were also observed between males: 2.5 cm (1.6-5.6 cm) and females: 2.5 cm (1.4-5.2 cm).
The joint space width measurement has been conducted by several authors to determine the normal mean and range. Most studies reveal a normal mean of about 4 mm.10
Joint space width is an important determinant of osteoarthritic changes. Many authors have concluded that joint space narrowing should not be expected in an elderly or obese person unless arthritic changes develop.2,16
The average joint space in our study was 4.5 mm (range = 2-12 mm; SD 2 mm). We observed no significant change among the different age groups.
Parameters measured by various authors concluded that the value was higher on the left side than on the right side.26,27
We have also found a higher value on the left side in most of the parameters but it was statistically significant in the neck shaft angle (120°-150°) only (P
Several authors have suggested that the vertical diameter of the femoral head is larger in taller individuals.17,28
A study conducted on the femora of Nigerians revealed a mean diameter of 54.23 in males and 54.08 in females.28
Chauhan et al
. reported a mean vertical diameter of femoral head in males and females to be 45.44 mm and 43.87 mm, respectively on the right side and 45.84 mm and 44.67 mm, respectively on the left side.17
We also agree with the reported conclusions, since the mean vertical diameter of the femoral head in our individual is less that of the Nigerians and the North Indians as the average height of the people of the northeast are shorter, this was also obvious when we compared the mean vertical diameter between the Caucasians and the Mongoloids of our own subjects, Caucasians are taller than Mongoloids and are expected to have larger diameter of femoral head.
All the parameters were found to be in the higher range in the Caucasoids than the Mongoloids, but statistically significant variation was found in the acetabular depth, (P = 0.001) and CE angle of Wiberg (P = 0.002) apart from the vertical diameter of the femoral head (P = 0.01). The increased acetabular depth and CE angle of Wiberg in the Caucasians is due to a larger head diameter.
There was variation in the parameters among the age groups that we measured, but no regular pattern of increase or decrease in relation to the age group was observed. The age group of 61-70 years showed the highest value in the acetabular angle, neck shaft angle and femoral neck anteversion, the same age group showed the lowest value in CE angle, acetabular depth and joint space width. The authors could not find any valid explanation for the variations in the age groups, measurement was more towards the extremes.
The Indian subcontinent comprises a vast collection with different morphological, genetic, cultural and linguistic characteristics, while much of this variability is indigenous, a considerable fraction of it has been introduced through large-scale immigration into India in historical times.
The northeastern part of India is inhabited by numerous endogenous tribes and castes that have their own distinct social, linguistic and biological identity. It has been hypothesized that a plethora of migration, particularly through the northeast Indian corridor has contributed to the present day population of northeastern India. Ethnically speaking, most of the tribal groups are Mongoloids; whereas caste groups are either Caucasoids or show a mosaic of features of both the ethnic groups. These factors are responsible for wide variations of different parameters in the individuals of the NE region.
Both the Mongoloids and Caucasoids show a certain degree of differentiation within themselves in work culture, habits and biological traits such as anthropometry, genetic markers and dermatoglyphics.29
Knowledge of the anatomical parameters of the bony components of the hip joint is very essential, as it will help better understanding of the etiopathogenesis of diseases like primary osteoarthritis of the hip joint. Awareness of the average dimensions of the acetabulum and femoral head will assist prosthetists in designing a suitable prosthesis according to the need of a particular individual.17,23
The parameter and its values in our series shows differences when compared to the other western literature. The limitation of this study has been a small sample size hence a study with a larger sample size is warranted.