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Introduction
Operations on the proximal femur are
one of the commonest in orthopaedic surgical
practice. The aim of these operations is to
remove pathology and restore anatomy to the
normal, as far as possible. The implants for
fixation of proximal femur fractures and joint
replacements have been designed taking into
consideration of the anthropometry of the
western population which vary from other ethnic
groups (1, 2). The standard commercially
available marketed prostheses sometimes may
not be the best fit to all subjects because of the
large anatomic variation among different
populations (2). The osteological parameters of
the proximal femur are very important for the
design of suitably sized prostheses of total hip
replacement (THR), especially for cementless
implantation (3). Orthopaedic surgeons always
stress the need for a proper implant-patient
match in hip joint replacements to avoid post-
operative complication of mismatch which may
affect the outcome of the operation (2).
Whereas what is normal has been
standardized for Caucasians and Chinese (4-6),
data for Indians are lacking. Since build,
physique, habits and genetic make up vary
markedly in different ethnic groups, it is possible
Ann Natl Acad Med Sci (India), 54(4): 203-215, 2018
Correspondence: Dr. Ramchander Siwach, Senior Professor and Head, Department of Orthopaedics,
Pt. B.D. Sharma PGIMS, Rohtak, Haryana, India. Email : rcsiwach.bps@gmail.com.
COL. SANGHAM LAL MEMORIAL ORATION delivered during the NAMSCON 2018 held at the
Mahatma Gandhi Medical College & Research Institute, Puducherry.
Anthropometric Study of Proximal Femur Geometry
and Its Clinical Application
Ramchander Siwach
Department of Orthopaedics,
Pt. B.D. Sharma PGIMS,
Rohtak, Haryana, India.
ABSTRACT
The implants for fixation of proximal femur fractures and joint replacements have been designed taking
into consideration of the anthropometry of the western population which vary from other ethnic
groups. The present study aimed to study the morphology of the upper end of femur in relation to its
various diameters and angles and compare the external and internal geometry of proximal femur as
obtained from radiographs, with actual measurements on cadaveric specimens in Indian population.
Seventy five pairs (150 bones) of cadaveric femora were studied morphologically and radiologically
using standardized techniques to obtain various anthropometrics measurements. These values were
compared with those reported in the literature for Hong Kong Chinese, Caucasian, Chinese and
Western populations. Data were found to be quite different from them. It is proposed that implants
designed for Western populations should be used judiciously and future implants be designed to match
the morphology of the Indian bones.
Keywords: Anthropometry, proximal femur, cadaveric, Indian population.
Published online: 2020-05-09
that anthropometric dimensions described as
normal for proximal end femur for Westerners
might be quite different from those encountered
amongst Indians. The present study was
conducted with aim to remove the lacuna of
information about proximal femoral geometry in
Indian people and evaluate its impact on implant
design. The present study aimed to investigate
the morphology of the upper end of femur in
relation to its various diameters and angles and
compare the external and internal geometry of
proximal femur as obtained from radiographs,
with actual measurements o n cadav e r i c
specimens. The clinical application of the
various geometric data, with the implants
available, for osteosynthesis of the upper end of
the femur and hip arthroplasty was also studied.
Materials and Methods
The study was conducted on 150 adult
cadaveric femora (Fig. 1). Specimens that
showed osseous pathology or previous fractures
were excluded from the study. With the help of
forensic expert these 150 adult cadaveric femora
were differentiated into male and female femora,
and their approximate age was determined. We
did study on femora of adult group (age
ap pro xim ate ly be twe en 20 -80 ye ar s) .
Roentgenograms of 75 pairs of near identical
specimen were taken in antero-posterior and
lateral views using a precise standardized
technique.
The specimens were placed directly over
the cassette so the magnification would be
insignificant. The distance between the X-ray
source and the film was 1.2 m and the beam was
centered on the lesser trochanter with the femur
lying in neutral rotation. For lateral view without
moving the femur, the X-ray source was rotated
through 90° in the vertical plane, the distance
between the source and the film remaining the
same. Then the femur was kept on a sponge of
the 2 feet length, 10" breadth and 8" height; the
X-ray cassette was kept touching the femur, with
one technician holding the cassette after wearing
a lead apron. But on these lateral views the whole
neck profile was not clear due to superimposition
of greater trochanter. So to avoid this problem
we kept the femur directly on the cassette in frog
leg view position holding the condyles of the
femur. In this view the neck profile of femur was
clear.
Morphological Study
The standard extracortical and endosteal
dim e ns i on s were de t er m in e d by dir e ct
measurement of cadaveric specimens. These
measurements were done with the help of
vernier caliper and goniometer (Fig. 2). With the
help of vernier caliper we measured femoral
head diameter, femoral head length, effective
neck length, femoral neck diameter and canal
width 20 mm above lesser trochanter, at level of
lesser trochanter and 20 mm below lesser
trochanter. With the help of goniometer neck
shaft angle and angle of anteversion were
measured.
a) Femoral head diameter: The distance
between the two extreme points of head was
measured.
b) Femoral head length: Radius of femoral
head is not equal superiorly and inferiorly
due to its placement (Fig. 3):
(i) Maximum femoral head length - From the
center of the femoral head to the periphery of
femoral head along the articular cartilage
border where it is maximum (superior);
(ii) Minimum femoral head length - From
the center of femoral head to the periphery of
204 Ramchander Siwach
Fig. 1: Cadaveric femora of 150 adults.
Fig. 2: Showing various extra cortical
dimensions in cadaveric femur and instruments
used for various measurements.
Fig. 3: Showing femoral head length in superior
and inferior quadrant in cadaveric femur.
Fig. 4: Showing variations in angles of
anteversion in cadaveric femur.
Fig. 5: Anatomical representation and
radiographic measurement on femoral
radiographs.
femoral head along the articular cartilage
border where it is minimum (inferior).
c) E f fectiv e neck length: (i) M a x imum
effective neck length - The length of neck
where it is maximum was measured along
the calcar (inferior); (ii) Minimum effective
neck length - The length of neck where it is
minimum was measured (superior).
d) Neck diameter: (i) Anteroposterior neck
diameter - The distance between the two
extreme points in middle of neck from the
center point of intertrochanteric line to base
of head in anteroposterior plane was
meas u re d ; ( ii) Sup e ri o inf e rio r neck
diameter - The distance between the two
extreme poi nts in middle of ne ck in
supe r i oin f eri o r p l ane was meas u red
(saggital plane).
205
Anthropometric Study of Proximal Femur Geometry
Anatomical characteristics in millimeters measured on the anteropos terior
radiograph
Reference axis system
O: Center of the lesser trochanter (origin of the axis system)
X: Horizontal axis through O on anteroposterior view
Y: Horizontal axis through O on lateral view
Z: Vertical axis through O on the anteroposterior and lateral Views.
A: Femoral head offset
B: Femoral head diameter
C: Femoral head position
D: Canal width, 20 mm above the
lesser trochanter
E: Canal width, at the level of the
lesser trochanter
F: Canal width, 20 mm below
the lesser trochanter
G: Endosteal width, at the
isthmus
H: Extracortical width, at the
isthmus
I: Isthmus position
J: Neck-shaft angle (degrees).
of femur 3 cm above isthmus and third point was
marked at the center of femur 3 cm below
isthmus, a line connecting these 3 points was
drawn and extended upwards and downwards.
With the help of scale we measured
femoral head offset, femoral head diameter,
femoral head position, neck diameter, canal
width 20 mm above lesser trochanter, canal
width at level of lesser trochanter, canal width
20 mm below lesser trochanter, endosteal width
at the isthmus and extracortical width at the
isthmus and isthmus position.
a) Femoral head offset: The distance between
the center of head of femur and vertical axis
drawn on femur.
b) Femoral head diameter: Two points were
marked at the maximum distance on the head
and the distance between the two was
measured.
c) Femoral head position: It is the distance
between the center of head and the horizontal
line drawn throu g h c e nter of l esse r
trochanter.
d) Neck diameter: The width of the narrowest
portion of the neck was measured.
e) Canal width, 20 mm above lesser trochanter:
Two points were marked 20 mm above the
lesser trochanter at maximum intracortical
area and the distance between them was
measured.
f) Canal width at level of lesser trochanter:
Two points were marked at the level of lesser
trochanter at maximum intracortical area
and t he d ista n c e b e twee n them was
measured.
g) Canal width 20 mm below lesser trochanter:
Two points were marked 20 mm below the
lesser trochanter at maximum intracortical
area and the distance between them was
measured.
h) En d o steal w idth a t th e ist h m us: The
narrowest portion of the medullary canal is
e) C an al wi dth , 2 0 m m a b ov e l e ss e r
trochanter: It was marked with a sketch pen
20 mm above and parallel to the horizontal
axis passing through the center of lesser
trochanter.
f) Canal width at level of lesser trochanter: A
horizontal line was drawn through the center
of lesser trochanter on anterior side.
g) Extracortical width 20 mm below lesser
trochanter: It was marked with a sketch pen
20 mm below and parallel to the horizontal
axis passing through the center of lesser
trochanter.
h) Neck shaft angle: Center of head of femur
was marked. Then mid point of the neck was
marked by measuring the width of the
narrowest portion of the neck and dividing
by two. The line from center of the head of
femur through the center of the neck was
drawn. A line through the centre of the
diaphysis of the femur was drawn. These
two lines intersected each other. The angle
between the two was measured.
i) Angle of anteversion: The center of the neck
between its anterior and posterior surfaces
was determined at two different points on the
neck, as viewed from above. A line was
drawn connecting these two points (Fig. 4).
The femur was placed on a smooth level,
horizontal surface so that it rested on three
points, namely, the posterior aspect of the
two femoral condyles and the posterior
aspect of the greater trochanter. The
goniometer was placed on the block of wood
on which femur was rested. One arm of
goniometer was opened and rotated till it
was corresponding to the line connecting 2
center points marked on the neck of femur.
The angle thus formed was read directly
from goniometer, the eye kept on a level with
the axis of the neck.
Radiological Study
A center point was marked at the level of
isthmus. Second point was marked at the center
206 Ramchander Siwach
called isthmus. Two points were marked at
this level at maximum intracortical area and
the distance between them was measured.
i) Extracortical width at the isthmus: Two
points were marked at the above level at the
maximum extracortical area and the distance
between them was measured.
j) Isthmus position: The distance between the
isthmus and the center of lesser trochanter
was measured.
k) Neck shaft angle: Center of head was
marked. The mid point of the neck was
located by measuring the width of the
narrowest portion of the neck and dividing
by two. The line connecting the center of
head of femur through the center of the neck
was drawn and extended to meet the vertical
axis marked on femur. The angle formed
between these two lines was measured by
goniometer.
l) Canal flare index (CFI): It is defined as the
ratio of the intracortical width of the femur at
a point 20 mm proximal to the lesser
trochanter to that at the medullary isthmus,
allowing us to classify the femur into three
general shapes: Normal, Stove pipe and
Champagne flute.
Various anatomical representation and
radiological measurement parameters are well
depicted in Fig. 5.
Clinical Correlation
The implants used for osteosynthesis and
arthroplasty were inserted in these bones, as
described in their respective operative steps. The
operations performed were dynamic hip screw,
dynamic condylar screw, cancellous screws, and
b la d e p l at e b ot h 95 ° a n d 1 3 0° , f or
osteosynthesis, and femoral endoprosthesis for
arthroplasty. In the cases of femoral arthroplasty
the clina clay was used as cement to assess the
cement mantle. After performing operations
these bones were examined morphologically as
well as radiologically as described above.
The comparison was done of both
radiological and morphological measurements
of le ngths, diamet ers and angles. T hese
parameters were correlated with the lengths,
diameter and angles of standard implants
available in the market for fixation of fracture
trochanter, fracture neck femur and arthroplasty
of hip. The standardization of the implants have
been done taking into account that the present
parameters of implants are acceptable in western
bone mass, the percentage of volume occupied
by these i m p lants in western b o n e was
co mpared, by the percen tage of v olume
occupied by these implants in our femoral bone.
And taking these as standard, modifications in
implants size will be suggested in accordance to
the anthropometric study of our race femora.
Results
Table 1 shows the average values of the
mor p h o l o g ical pa r a m e t e rs stud i e d , their
standard deviation, minimum and maximum
values and Table 2 shows the radiological aspect
of all the morphological measurements. Table 3
shows comparison with Western and Asian
(Chinese and Caucasians in Hong Kong). The
volume of implants in the femoral head was
2
calculated using d /4 x l where d is diameter of
femoral head and l is length of implant [l =2/3 d-
10 mm (subchondral bone left)]. Table 4 depicts
the percentage of femoral head volume occupied
by various implants in different populations.
Cr o s s -sectional area of fe m oral n e c k is
2
calculated by Formula p d /4 (d = diameter).
Table 5 represents the percentage of cross-
2
sectional area of neck p d /4 occupied by various
implants in different populations.
Discussion
There are considerable variations in the
fe m oral g e ometry of p o p ulations across
different geographical locations and ethnic
groups (3). Implants for fixation of proximal
femur fractures have been designed taking into
consideration of the anthropometry of the
western population which varies from those of
other ethnic groups (1). Similarly the standard
207
Anthropometric Study of Proximal Femur Geometry
Table 2: Radiological measurements
Dimensions
No.
Average Minimum
(mm) Maximum
(mm) Standard
deviation
(mm)
Femoral head offset
75
38 29 47 5.52
Femoral head diameter
75
43.53 38 49 3.40
Femoral head position
75
50.15 41 62 4.80
Neck diameter
75
29.5 24 35 3.19
Canal width, 20
mm above lesser
trochanter
75
43.5 33 53 4.37
Canal width at level of lesser
trochanter
75
23.8 18 30 3.20
Canal width 20
mm below lesser
trochanter 75
16.57 12 21 1.99
Endosteal width at the isthmus 75 10.11 6 15 1.90
Extracortical width at the
isthmus 75
24.42 20 30 2.54
Isthmus position 75 112.92 87 128 10.58
Neck shaft angle (°) 75 123° 118° 140° 4.29
208 Ramchander Siwach
Dimensions
No.
Average
Minimum
(mm)
Maximum
(mm)
Standard deviation
(mm)
Femoral head diameter 150 43.95 35.4 50.0 3.06
Femoral head length
Maximum (superiorly)
150
36.9
24.4 49.2 4.11
Minimum (inferiorly)
25.5
16.0 36.5 4.26
Effective neck length
Maximum (superiorly)
150 37.23
26.5 50.5 4.65
Minimum (inferiorly)
22.69
16.3 39.2 3.65
Neck diameter
Anteroposterior
150
24.90
18.7 34.4 2.94
Superoinferior
31.87
23.3 40.9 2.91
Extracortical width, 20mm
above lesser trochanter
150
50.24
39.7 63 4.81
Extracortical width at
level of lesser trochanter
150
40.44
29.8 52.6 4.67
Extracortical width 20mm
below lesser trochanter
150 30.70 22.1 36.6 3.13
Neck shaft angle (°) 150 123.5° 114° 136° 4.34
Angle of anteversion (°)
150
13.68°
0° 36° 7.92
Table 1: Morphological measurements
Table 4: Percentage of femoral head volume occupied by various implants in different races
Different studies
3 Cancellous
screws
3 Acinis
screws 2 Garden
screws DHS
Blade
plates
Western
6.03
6.99 6.88 7.44 4.39
Caucasian
6.37
7.38 7.26 7.85 4.64
Asian (Hongkong
Chinese)
6.81
7.89 7.76 8.39 4.96
Indian
6.24
7.24 7.11 7.69 4.55
Our study
6.48
7.52 7.39 7.99 4.72
Table 5: Percentage of cross sectional area of neck occupied by various implants
12.77 14.81 14.56 15.75 9.31
15.07 17.48 17.18 18.58 10.98
15.72 18.23 17.92 19.38 11.45
Different studies
3 Cancellous
screws
3 Acinis
screws 2 Garden
screws DHS
Blade
plates
Caucasian
Asian (Hongkong
Chinese)
Our study
Average Dimensions
Present
study
(Indian) Western
(6,7)
Caucasian
(5)
Hongkong
(Chinese) (5)
Femoral head offset
38 43
Femoral head diameter
43.53 46.1 46 45
3
Femoral head volume (mm )
29618.55 34181.41 30744.48 26782.67
Length of implant in femoral head (mm)
19.3 20.73 19.67 18.33
Femoral head position
50.15 51.6
Neck diameter
29.5 33 31
Canal width, 20mm above lesser trochanter
43.5 45.4
Canal width at level of lesser trochanter
23.8 29.4
Canal width 20mm below lesser trochanter
16.57 20.9
Endosteal width at the isthmus
10.11
12.3
Extracortical width at the isthmus
24.42
Isthmus position
112.92
113.4
Neck shaft angle (°)
123°
124.7° 136°
135°
Angle of anteversion (°)
13.68°
7°
14°
2
Cross-sectional area of femoral neck (mm ) 633 778.92 660.12
- -
- -
- -
- -
- -
- -
--
--
-
-
-
-
Table 3: Comparison of measurements with other groups
209
Anthropometric Study of Proximal Femur Geometry
commercially available marketed prostheses
sometimes may not be the best fit to Indian
patients because of the large anatomic variation
(7). So the present study aimed to report
proximal femoral geometry in Indian population
and evaluate its impact on implant design.
In our ethnic race on radiological
measurement average femoral head offset was
38 mm as compared to 43 mm in western
literature. Similarly femoral head diameter in
present study was 43.53 mm as compared to 46.1
mm in western literature. This shows that our
skeleton is smaller than the western one. So in
consideration of clinical importance of this
parameter we shall have to think of smaller
implants for osteosynthesis and may be a smaller
size of endoprosthesis in few of our bones,
especially in females. This dimension is also of
clinical significance in acetabular cup size and
t h e n u m b er o f s cr ew s t o b e u se d i n
osteosynthesis of fracture neck of femur. In our
set up smaller acetabular cup and lesser number
of screws and smaller implants as DHS, DCS
and blade plates need to be designed. As there is
difference between the size and shape of the
proximal femur of our race and western race
with respect to canal width at different levels,
hence the implants made according to western
race do not fit accurately in our bones. There has
to be a close match between the dimensions of
the femur and the implant prosthesis. Similarly
on radiological measurement the average
intramedullary width of isthmus in our race was
10 .11 mm (ma ximum being 15 mm and
minimum being 6 mm) as compared to12.3 mm
in western literature (maximum being 18.5 and
minimum being 8 mm). There is marked
difference between the two races in this
parameter. This parameter is of immense
importance in choosing the right size of the stem
of e nd o pr o st h es i s and the di am e te r of
intramedullary nails because this parameter is
much less in our race as compared to western
race. On radiological measurement in our race
average neck shaft angle was 123° (maximum
being 140° and minimum being 118°). In
western literature average neck shaft angle was
124.7°, maximum being 154.5° and minimum
being 105.7°. In Caucasian male average is 136°
with maximum being 161° and minimum 120°.
In Caucasian female average is 133° with
maximum being 145° and minimum 115°. This
dimension is of significance in angled implants
such DCS, DHS, blade plate. This angle being
lesser in our race, we should prefer implants of
lesser angle to avoid their superior cut through in
the femoral head and neck. On radiological
measurement femoral head position average was
50.15 mm in the present study as compared to
51.6 mm in western population. There is no
significant difference between the two, probably
because there is not much difference between
neck shaft angle of our and western race.
The percentage of cross-sectional area of
neck occupied by three cancellous screws of 6.5
mm in the neck is 12.77% in Caucasian as
compared to 15.72% in our study. Therefore, the
volume of bone mass replaced by metal is more
in our patients as compared to counterpart in
west. The percentage of femoral head volume
occupied by three cancellous screws is 6.48% in
our study as compared to 6.37% and 6.03%, in
Caucasian and western, respectively. So, the
chances of union reduce when 3 lag screws of
6.5 mm diameter each are inserted in the already
compromised head and neck of the femur,
especially in females. Therefore, it is advisable
to put only two screws in place of three. In case
we need to put 3 cancellous screws, one should
be put as a cantilever along the superior border of
the neck, which will hold only in the trochanter
and the head. If we reduce the thread diameter of
cancellou s screws to 6.0 mm t h e n , th e
percentage of femoral head volume occupied by
three cancellous screws in our race becomes
5.52% which is nearly ideal for our race. The
main hold of the screw threads is in the head of
the femur. The head length is more in the
superior part, the average is 36.9 mm as
compared to the inferior part where the average
is 25.5 mm. The cancellous screws are available
in 16 mm and 32 mm thread length. Considering
these parameters the screw thread, especially the
32 mm thread length, will not cross the fractured
210 Ramchander Siwach
site in subcapital and transcervical fracture neck
of the femur which is the prime requisite for
union. Regarding the 16 mm thread length, it
will cross the fracture site in subcapital and
transcervical fracture neck femur in normal head
which has reasonably adequate head length
superiorly. In the central and superior area there
is otherwise ample space available for a good
hold. Therefore, in adults, subcapital and
transcervical fractures, the 32 mm thread length,
6.5 mm or 7 mm cancellous screws should
preferably not be used. The 16 mm thread length
hold is good if they are passed through the center
of the neck or in the superior quadrant. In the
inferior area the head length is small and if the 5-
10 mm subchondral area is left, as recommended
the chances of the threaded portion crossing the
fracture site is minimal even with 16 mm
threaded screws. Therefore, accuracy is of prime
importance regarding the length of the screws as
the margin of error is less.
The percentage of femoral head volume
occupied by DHS is 7.99%, 7.69%, 8.39%,
7.85% and 7.44% in present study, Indian
counterpart, Asian, Caucasian and western
studies, respectively. Similarly percentage of
cross-sectional area of neck occupied by DHS in
our study is 19.38%, Asians 18.58% and
Caucasian 15.75%. The compression of bone in
the head and replacement of bone mass by metal
produces a tamponade effect in head which has a
large bearing on nonunion and avascular
necrosis; which are the key complications of
fracture neck of femur. Secondly, there are two
kinds of barrels in DHS, long and short ones with
length of 38 mm and 25 mm respectively, with
the outer diameter of 12.6 mm each. So while
using this kind of barrel, one has to be
considerate in accordance with the fracture line,
otherwise the barrel will be longer. This will
further occupy more space upto the longer
portion along with the neck length and will not
allow the controlled collapse. In our study the
average neck length is 32 mm and only the short
barrel should be used, because in using a long
barrel there is always a danger of barrel crossing
t h e f ra ct u re si te , t h er eb y p r ev en t in g
compression at the fracture site and controlled
collapse thereafter. Thirdly the thread length of
the DHS screw is 22 mm, with the outer diameter
of 12.5 mm, and shaft diameter of 8 mm. To put
the 12.5 mm screw we have to tap for 12.5 mm
which takes out a lot of bone mass both from the
neck and the head. The head length in our series
varies from 25.5 mm to 36.9 mm and for proper
purchase of DHS screw 5-10 mm subchondral
bone is to be left, resulting thereby that screw
thread which is 22 mm in DHS will not cross the
fracture site in subcapital fractures. Lastly in our
study, the neck shaft angle was found to be 123°
(average radiologically), though ranging from
118° to 140°. DHS is available in angles starting
from 135° to 150° at the difference of 5°. From
the above information it appears that the 135°
angle is more and hence chances of the superior
cut through of the implant are more. Otherwise
one has to make the entry point at such a level on
the lateral side of trochanteric area so that the tip
of screw lies in the center or posteroinferior
quadrant of the head. To achieve this valgus
osteotomy will be needed simultaneously for a
better approximation of femoral shaft with the
plate, and thereby achieving an undesirable
overall coxa valga in comparison to contralateral
hip which may result in limb length discrepancy
and avascular necrosis of head of femur. We
conclude that for the Indian patients, the implant
size should be reduced to 11.5 mm in place of
12.5 mm, then the cross-sectional area occupied
in the neck will be 16.40% and the percentage of
femoral head volume occupied will reduce to
6.76%, which are within the desirable limits.
This should be done even with compromising
the strength of the implant, to have better
biology, which is the key factor for union and
vascularity. The threaded portion should also be
reduced from 22 mm to 15 mm, and the implant
should also be available in 120°, 125° and 130°
in accordance with our patients requirement.
Also we should always procure the X-rays of
both the hips to achieve same neck shaft angle
peroperatively as it varies from person to person.
Regarding the diameter and thread length
parameters, same is true with DCS screw but its
angle is acceptable.
211
Anthropometric Study of Proximal Femur Geometry
In the present study, the CFI varies
from 2.75 to 8.5. Depending on the CFI, the
shape of the medullary canal, the normal canal
type is 50%, champagne-fluted canal type in
38.46% and stovepipe canal type in 7.69%, and
in a few cases do not fit in any of the types
described above. The implants available are in
variable lengths, ranging from 126 mm to 174
mm, with distal width ranging from 7 mm to 11
mm and anteroposterior thickness ranging from
6 mm to 8.5 mm. Our isthmus position ranges
from 87 mm to 128 mm (average 112.92 mm)
and the endosteal diameter at the level of isthmus
varies from 6 mm to 15 mm (average 10.11 mm).
Therefore, in the Indian patients only smaller
prostheses are used, and in case of thin and lean
patients (especially of younger age group) even
CDH implants are good enough. At a distance of
20 mm above the l esser t r ochanter, th e
anteroposterior canal width was found to differ
by 45.4%, when compared with a French
population which can affect the mechanical
stability of femoral stem (8). We recommend
endoprosthesis having length ranging from 100
mm to 150 mm, distal width from 6 mm to 11mm
and anteroposterior thickness from 5.5 mm to 8
mm . T he i n ci de nc e o f i n tr aop er at iv e
complications like splintering and fractures
ranges from 4% to 21% (9-11). These are due to
over-sized implants available that have been
ma nu fa ct ur e d b as ic al ly w i th we ste rn
parameters. Most femoral stems are designed to
extend to the isthmus of medullary canal, so that
the component is stable and there is a 2 mm
cement mantle around it. Therefore, only smaller
sized implant, both in length as well as in
thickness, with straight and polished stem, are
preferred. To achieve these conditions the
manufacturers should reduce the geometric
measurements of endoprosthesis but at the same
time should not compromise on strength of
implant. Another important point in total hip
arthroplasty is restoration of original position of
the center of head along with the limb length
equality and the restoration of the original
balance of abductors (6). For this purpose
femoral components are available in a long
range of neck lengths for each separate stem size.
To have a good muscle balance and limb length,
the head offset is an essential component. There
are various implants available with variable
offsets ranging from 32.8 mm to 50 mm. In our
study the head offset ranges from 29 mm to 47
mm (average 38 mm), hence in our patients 37.5
mm to 44 mm head offsets are suitable. So the
clinical result of the above observations made in
relation to the medullary canal geometry is, that
the implant needs to be designed on the basis of
anthropometric data available, along with other
factors like age, sex and the environment, etc.
This will minimise the preoperative and
postoperative complications involved in total
hip arthroplasty, although for a perfect match
each implant needs to be customised.
Some other authors have also reported
the assessment of geometry of proximal femur in
In d ia n p op ul at io n a nd hav e sug g es te d
modifications in implants. Pathrot et al (1)
advocated certain modifications in the presently
available short cephalomedullary nail designs
for them to better fit the anatomy of our subset of
population: (a) two nails of 125° and 135°; (b)
the medio-lateral angle at the level of 65 mm
from the tip of the nail; (c) two femoral neck
screw placements (35 and 45 mm from the tip of
the nail); and (d) five different sizes of distal
width for better fit in canal (9-13 mm). Maji et al
also found variations in the morphology of the
proximal femur between the Indian population
and that of other countries, and advocated the
need for standardizing THR implant sizes for the
Indian population, especially for cementless
implantation (3). Rawal et al observed a
difference of 16.8% in the femoral head offset
between Indian and Swiss populations, which
can affect soft tissue tension and range of motion
(7). Maheshwari et al also reported that when
compared with the Western data, the femoral
neck anteversion values were 3-12 degrees
lower and the combined anteversion values were
3-5 degrees lower in Indian adults (11). The
a c e t ab ul um a n t e v e rs io n v a l u e s w e r e
comparable, but were skewed towards the higher
side (11). But Saikia et al observed that the neck
shaft angle and the femoral neck anteversion in
212 Ramchander Siwach
213
Anthropometric Study of Proximal Femur Geometry
Implants
Presently available
dimensions
Our recommendations
Cancellous screw
Thread diameter 6.5
mm
Thread diameter 6
mm
Thread length 16
mm, 32
mm
Thread length 16
mm
Acinis screw
(cannulated)
Thread diameter 7
mm
Thread diameter 6.5
mm
Thread length 16
mm, 32
mm
Thread length 16
mm
Garden screw
Thread diameter 8.5
mm
Thread diameter 8
mm
DHS screw
Thread diameter 12.5 mm
Thread diameter 11.5 mm
Thread length 22
mm
Thread length 15
mm
Barrel short and long
Barrel short
Angles 135° to 150°
(at difference of 5°)
Angles 120° to 150°
(at difference of 5°)
Blade plate
‘U’ profile 6.5x16 mm
‘U’ profile 6.5x12.5
mm
Angles 95° and 130°
Angles 95°, 120°, 125° and 130°
Gamma nail
Standard Gamma nail
Modified by Leung et al1
Mediolateral angle-10°
Mediolateral angle 4°
Length 200
mm
Length 180
mm
Diameter of distal shaft
12
mm, 14
mm and 16
mm
Diameter of distal shaft 11
mm and
12
mm
and 12
mm
This modified nail is also suitable to
our race femora
Endoprosthesis
Length 126
mm to 174
mm Length 100 mm to 150 mm
Distal width 7
mm to 11
mm Distal width 6
mm to 11 mm
Anteroposterior thickness 6 mm to
8.5 mm Anteroposterior thickness 5.5 mm
to 8
mm
Modularity up to 10
mm Modularity up to 15
mm
Head offset 32.8 mm to 50
mm Head offset 37.5 mm to 44 mm
Stem type –
-Banana shape
-Straight
-Rough and grooved
-Flat back
-Rounded
-Rectangular
cross section
-Trapezoidal and diamond shaped
Stem type –
Polished, straight and trappered
collarless stem is preferred.
Table 6: Our recommendations for implant dimensions
individuals of North eastern region of India was
5-6 degrees more than the western literature
(12).
Anthropometric studies for proximal
femur in ethnic groups other than western
population have reported significant differences.
Pi et al reported that Chinese proximal femoral
parameters are significantly different from
Westerners (13). Compared with Westeners, the
offset was smaller, while the neck shaft angle
was significantly larger in Chinese population
(13). Most parameters of the proximal femoral
medullary cavity diameter were significantly
smaller in Chinese population than those in
Westerners (13). Atilla et al reported osteometry
of the femora in Turkish individuals (14). They
observed diverse features of femoral geometry
in Turkish individuals compared to Western
populations and advocated that these differences
should be taken into account in the design and
development of hip prostheses (14).
The observations in the present study
have profound implications. Not only are
western implants large in size, their angles, and
orientations and thread length also mismatch
Indian femora. Implants designed for western
skeletons occupy much more space in the Indian
femoral head and neck. A certain subset of Indian
femora does not have any implant available to
them as they are too small. Furthermore, a
shorter neck length implies that the threads of
cancellous or Garden screws used to fix neck
fractures may not cross the fracture site thereby
failing to provide compression and thus
defeating the whole purpose of the surgery. If
too much bone is replaced by metal a tamponade
effect can ensue that may cause avascularity of
fe m o ral he a d, co n sequently resulting in
nonunion of neck fractures and/or AVN. Since
our heads are smaller, the threads of screws often
fail to cross the fracture of neck of femur
especially if the fracture is sub capital and the
screw placement in the inferior quadrant of head.
This means we must have screws with shorter
thread lengths. In thin built and short individuals
the neck may not have space enough to occupy
the three 6.5 mm screws recommended for
fixation of neck fractures. A smaller neck shaft
angle implies that a DHS inserted through the
classical entry portal using angled guide will
either go into the superior quadrant or pull the
fracture in valgus both of which are undesirable.
We probably require DHS with smaller angles.
Our recommendations for different implants are
shown in Table 6.
The implication s of the s t u dy on
a r t hr o p l a s t y o p e r a ti o n s c a n n o t b e
overemphasized as these are designed to
reproduce the normal anatomy as far as possible.
Orthopaedic surgeons always stress the need for
a proper implant-patient match in hip joint
replacements, in particular, for a cementless
fem o r a l st e m (7) . T h e co m p l ications of
mismatch are aseptic loosening, improper load
distribution, and discomfort (7). The clinical
symptoms are due to the bone implant mismatch,
which result in micromotion. There are studies,
which highlight that these micromotions should
be reduced to 14 micra or less, to prevent
osteolysis and aseptic loosening (5). We agree
with Roy et al that improved knowledge of the
morphology of the proximal femora will assist
the surgeon in restoring the geometry of the
proximal femur during total hip arthroplasty and
the data could be used as a guideline to design a
more suitable implant for Eastern Indian
population (2).
References
1. Pathrot D, Ul Haq R, Aggarwal AN, Nagar
M, Bhatt S (2016). Assessment of the
geometry of proximal femur for short
cephallomedullary nail placement : an
observational study in dry femora and
living subjects. Indian J Orthop 50(3): 269-
276.
2. Roy S, Kundu R, Medda S, Gupta A,
Nanrah BK (2014). Evaluation of proximal
fe m oral geometry in plain anterior-
posterior radiograph in Eastern-Indian
population. J Clin Diagn Res 8(9): AC01-
AC03.
3. Maji PK, Roychowdhury A, Datta D
214 Ramchander Siwach
(2012). Investigating the morphology of
th e pr o xim al fem ur of th e In d ian
population towards d e s i gning m o r e
suitable THR implants. J Long Term Eff
Med Implants 22(1): 49-64.
4. Hoaglund FT, Low WD (1980). Anatomy
of the femor al neck and head, with
comparative data from Caucasians and
HongKong. Chinese Clin Orthop 152: 10-
16.
5. Reddy VS, Moorthy GVS, Reddy SG
(1999). Do we need a special design of
femoral component of total hip prosthesis
in our patients? Indian J Orthop 33(4): 282-
284.
6. Noble C, Jerry W, Alexander BS, et al
(1988). The anatomical basis of femoral
component design. Clin Orthop Rel Res
235: 148-164.
7. Rawal B, Ribeiro R, Malhotra R, Bhatnagar
N (2012). Anthropometric measurements
to design best-fit femoral stem for the
Indian population. Indian J Orthop 46(1):
46-53.
8. B o mb el li R , S an to re R F ( 19 84 ).
Cementless isoelastic total hip prosthesis:
prelimin a r y r e p o rt o n th e first 215
consecutive cases. In: The Cementless
Fixation of Hip Endoprosthesis. Morscher
E, ed. New York: Springer-Verlag, 243.
9. Engelhardt A (1984). Casual histogenesis
and biomechanical discoveries as a basis
f o r c e m e n t l e s s fi x a t i o n o f h i p
endoprosthesis. In: The Cementless
Fixation of Hip Endoprosthesis. Morscher
E, ed. New York: Springer-Verlag.
10. Zweymuller K (1986). A cementless
titanium hip endoprosthesis system based
on press-fit fixation: basic research and
clinical results. Instr Course Lect 35: 203-
225.
11. Maheshwari AV, Zlowodzki MP, Siram G,
Jain AK (2010). Femoral neck anteversion,
acetabular anteversion and combined
anteversion in the normal Indian adult
population: a computed tomographic study.
Indian J Orthop 44(3): 277-282.
12. Saikia KC, Bhuyan SK, Rongphar R
(2008). Anthropometric study of the hip
joint in northeastern region population with
computed tomography scan. Indian J
Orthop 42(3): 260-266.
13. Pi Y, Zhao Y, Wang W, He Z, Mao X (2013).
Mea su re m en t of pro xi ma l fem o ra l
morphology and analysis of 500 cases in
Hunan Province. Zhong Nan Da Xue Xue
Bao Yi Xue Ban 38(9): 925-930.
14. Atilla B, Oznur A, Cağlar O, Tokgözoğlu
M, Alpaslan M (2007). Osteometry of the
f e mo ra in Tu rk is h in di vi du al s : a
morphometric study in 114 cadaveric
femora as an anatomic basis of femoral
component design. Acta Orthop Traumatol
Turc 41(1): 64-68.
215
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