Indian Journal of Clinical Anatomy and Physiology


Morphometry of proximal end of femur in population of Telangana state and its clinical application


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Author Details: K Sreenivasa Reddy*,P David Anand Kumar

Volume : 6

Issue : 1

Online ISSN : 2394-2126

Print ISSN : 2394-2118

Article First Page : 57

Article End Page : 60


Abstract

Introduction: Fracture proximal end of femur is frequent in our busy life using more vehicles and resulting in more accidents and also because of increased geriatric population where the fracture occurs due to osteoporosis.

Aim: to standardize various parameters of femur.

Materials and Methods: The length of the femur was measured using a wooden board fixed with a tape and a mobile wooden piece. The angle between the axis of neck and the axis of shaft of femur was determined based on procedure given by Singh and Bhasin.[1] The axis of neck was determined by colored thread used to divide the anterior surface of neck into two equal halves. The width and length of neck of femur are measured using digital vernier calipers.

Results: The length of femur was 43.55cms (SD=2.283), neck shaft angle was 125.35° (SD= 7.883°), length of neck anteriorly 26.51mm (SD=3.369), length of the neck posteriorly 30.846 mm (SD=3.9mm), width of the neck 30.68mm anteroposteriorly (SD=4.359mm), and 29.94 super inferiorly (SD=3.599).

Conclusion: Femoral measurements in this study show that there is a significant difference between our population and other populations studied; there is a need to explore options for customizing implants according to anthropometric measurement corresponding to local population.

Keywords: Femur, Fracture, Dimensions, Implants, Morphometry.

Introduction

Fracture of proximal end of femur involving neck and trochanter are quite common. Internal Fixation with implants is a must for speedy recovery of patients. These implants are designed and produced according to wester n measurements. Most of our Indian orthopedic surgeons are of opinion that these implants are of large sized for our population and should be modified to suit our population.

The usage of those oversized implants affects the wound healing and end result of the surgery. So we studied the femur, its length, neck-shaft angle, length of the neck anteriorly and posteriorly, and width of neck anteroposteriorly and superio inferiorly in order to standardize the measurements of femur.

Materials and Methods

A total of 366 femora were collected from varius colleges of telengana area as follows. 90 femurs from MIMS Ghanpur, 80 femur from Siddipeta, 80 Femure from RIMS Adilabad, and 116 femur from Gandhi medical college and the measurements are taken as follows. The length of the femur was measured using a wooden board fixed with a tape and a mobile wooden piece (Fig. 1). The angle between the axis of neck and the axis of shaft of femur was determined based on procedure given by Singh and Bhasin.[2]

The axis of neck was determined by colored thread used to divide the anterior surface of neck into two equal halves. The axis of the femur is marked along a thread suspended from the upper end of greater-trochanter to the lateral condyle of the femur. The angle between axis of neck and axis of femur was measured using a goniometer (Fig. 2).

The length of the neck is measured anteriorly between the base of the head and midpoint of intertrochanteric line (Fig. 4). Posteriorly the length is measured between the base of head and midpoint of intertrochanteric crest (Fig. 5). The width of neck is measured supero inferiorly (Fig. 6) and anteroposteriorly. The results are represented in table 2, and these measurements are compared with dimensions of the presently available implants in table 3.

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Fig. 1: Measuring length of femur

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Fig. 2: Measuring neck-shaft angle of femur

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Fig. 3: DHS implant size

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Fig. 4: Length of neck anteriorly

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Fig. 5: Length of neck posteriorly

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Fig. 6: Width of neck supero inferiorly

Results

The statistical analysis was done using SPSS 15.0. The descriptive statistics (frequency, range, mean and standard error) for the variables are presented in Table 2.

Table 1: Dimensions of orthopedic implants commonly used for treatment of proximal fractures of femur

Implant: DHS/DCS

Dimensions

Thread diameter

12.5mm

Thread length

22mm

Shaft diameter

08mm

Barrel angle

125 -130°

Barrel diameter

12.6mm

Barrel thickness

15.8mm

Barrel width

19mm

AO SCREWS

 

Thread diameter

6.5mm

Shaft diameter

4.5mm

BLADE PLATE

 

Blade length

35mm

Blade thickness

02mm

Table 2: Descriptive statistics

Variable

Number of femurs

Mean ± SD

Length of femur (cms)

366

43.55 ± 2.283

Neck-shaft angle (degrees)

366

125.35 ± 7.883

Length of neck (mm)

Anteriorly

366

26.51 ± 3.369

Posteriorly

366

30.846 ± 3.900

Width of neck (mm) Anteroposteriorly

Supero inferiorly

366

366

30.68 ± 4.359

29.94 ± 3.599

Table 3: Comparison between dimensions of Indian femurs and foreign implants

Variable

Present Study

Dimension of Implant (11)

Neck-shaft angle

125.35°

125° - 155°

Neck length

Anteriorly

26.5mms

22mms

Posteriorly

30.8mms

22mms

 

 

Present Study

Width of compact bone (18)

Dimensions of Implant

Cancellous bone

Neck width antero-posteriorly

30.68 mm

4mm

19 mm barrel diameter

7.68 mm/2=3.84

Neck width supero-inferiorly

29.94 mm

4.5mm

15.8 mm barrel thickness

9.64mm/2=4.82

Discussion

The femur’s neck is a very important structure for erect position of human body. According to large number of Anatomists the average neck-shaft angle in human beings is 125° (range 110° to 144°) and in fetuses is 140°. The angle between the axis of the neck and axis of the shaft of femur was studied by many workers previously namely Parson P.G (1914)[2] Hashimato M (1938),[3] Humphry WH (1958),[4] Kate BR (1967),[5] Singh P (1968).[1]

The average angle in the present study (n= 366) is found to be 125.35° (range 105°-142°), standard error being 7.88°. Very few Indian studies are available with respect to the dimensions of the proximal femur. Kate measured neck shaft angle of 1000 femora and found the average as 128.4° degrees in the year 1968.[5] Siwachmeasured neck shaft angle in 75 pairs of femora and found average to be 123.5°.[6]

In 2008 Saikia KC worked on the North Eastern population and found the average next shaft angle to be 139.5°.[7] In 1993 Isaac B found that the average neck shaft angle was 127.5° (8). Toogood et al, in the year 2009 studied the proximal femoral anatomy and concluded the average neck shaft angle as129.23°.[8]

Minakshi et al[9] in their study of morphometry of proximal femur in Indian population (the bones collected in north India got femur length as 42.82± 2.87 cm, neck length as 44.75 mm ± 8.097, width of neck as 24.01 ± 3.05 mm and neck shaft angle as 128.9 ±5.52°, when compared to our study the length of femur is very near to our values, the neck shaft angle is a little higher and the length and width of neck of femur are very high compared to our study. This signifies that the values are differing for people of various ethinic groups.

Aparnagullapalli[10] et al in their study of femoral neck shaft angle followed Billing[11] and Norman[12] method to measure the neck shaft angle in which the axis of the neck is represented by a line drawn from the centre of the femoral head to the center of the femoral neck at the narrowest part of the neck and a line drawn from the middle of the femoral condyles to the middle of the greater trochanter is taken as axis of shaft of femur. But in Bhasim et al[1] method which we followed the axis of neck was determined by colored thread used to divide the anterior surface of neck into two equal halves. The axis of the femur is marked along a thread suspended from the upper end of greater-trochanter to the lateral condyle of the femur. They observed the neck shaft angle as 121°, this may be because of the procedure used to determine the neck shaft angle by them.

Our results are almost similar to that of Siwach and Isaac but differes a little with the studies of Toogood et al, and largely from that of Saikiaet al.

The mean length of neck in the present study is 26.5 mm anteriorly and 30.8 mm posteriorly, average 28.7mm and the standard error is 0.0133. According toSiwach (2003) maximum and minimum effective neck length are 37.2 mms and 22.6 mms and mean is 29.9 mms. In our study the average neck width is 30.31 mms (SE 0.073). So we get the higher value than Siwach who got it as 24.9 mm (width).

Dr. Ravichandran[13] and others in their study at VMKV medical college Salem collected about 560 unpaired femora from varios colleges of Madras state and studied various dimentions their results are as follows average neck shaft angle is 126.55°, neck length as 31.18 mm, width 30.99 mm. These results are almost consistent with our results. Ravichandran et al in their study proved that the implants available at present are not suitable for our Indian Patients as they are prepared according to the sizes of western population.

Ravi G.O[14] et al in their study on south Indian femora got the average length of femor as 44.71, length of neck of femur as 36.3 mm, and neck shaft angle as 136.8° and these measurements are consistent with our results..

Amith R, Beena N⊃1;° and others in their study of south Indian femora by computer assisted image analysis method got the neck shaft angle as 121.2°. This is far less than most of the studies conducted on south Indian bones.

A comparision between the dimensions found in our study and dimensions of the available orthopaedic implants shows that these implats are oversized for Indian skeleton and sufficient bone stock is not available for effective fixation. Use of such implants not only effect the functional end result but also negates the very purpose of internal fixation and early rehabilitation. The D H S dynamic hip screw is the implant of choice for stable trochantric fracture and dynamic condyle screw is for unstable trochantric fracture.

High angle implants (as DHS barrel angle 135°) causes malunion in valgus and that with lower angle (as DHS barrel angle 95°) causes malunion in varus thus altering biomechanics at both hip and knee joints leading greater risk of secondary arthritis to the patient.

Insertion of the screws with large thread diametre needs removal of cancellous bone leading to loss of cancellous bone needed for repair of fracture,

As an example DHS/DCS has a thread diameter of 12.5 mm and barrel diameter of 12.6 mm, insertion of this screws needs reaming upto 11.5mm and tapping upto 13.5 mm, thus removing large cancellous bone from the neck of femur. There by delaying the healing process. It is clear that the proximal femoral geometry varies among different ethnic groups. Therefore usage of implants designed exclusively for Western bones will not be suitable for other ethnic groups.

The dimensions found in our study are lesser than the measurements of the orthopedic implants. These implants are bigger in size for the Indian femora and therefore bone stock is not available for an effective fixation. These bigger implants result in failure of the surgery. The Dynamic Hip Screw (DHS) is used for stable trochanteric fractures & Dynamic Condylar Screw (DCS) / Condylar Blade is usedfor unstable trochanteric fractures (14, 15) higher angle implants (eg. DHS barrel angle: 135°) causes malunion in valgus & that with lower angle (DCS & Condylar Blade plate 95°degrees) causes malunion in varus. The thread diameter of the DHS / DCS is 12.5 mm and barrel diameter is 12.6 mm (Table 1).

In 2003 Siwach has measured the neck width as 2.49 cm and neck length as 3.18cm. The width of the neck in our study is only3.097 cm. Therefore these implants (Fig. 3) are bigger in size and cause arrest of circulation resulting in non- union and avascular necrosis.

In 2009 Mishra AK et al[15] in his study concluded that these western implants are bigger and not suitable for Indians. He found a need to design these implants suitable for Indian bones stresses that the fracture implant designs should be specific for Indians.

Conclusion

The present study shows the neck shaft angle and the length and width of the neck of the femur in our people is far less than the Western people. So the implants prepared according to western people dimensions are far bigger than our femora. So there is a need to prepare implants according to our study to be useful for our people.

Sources of Funding: Nil.

Conflicts of Interest: None.

References

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