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Bilateral asymmetry in bone measurements of the hand and lateral hand dominance.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 52:27- 31 (1980)
Bilateral Asymmetry in Bone Measurements of the Hand
and Lateral Hand Dominance
C.C. PLATO, J.L. WOOD, AND A.H. NORRIS
National Institute on Aging, Gerontology Research Center, Baltimore City
Hospitals, Baltimore, Maryland 21224
K E Y WORDS Hand, Bone measurements, Bone
loss, Bilateral Asymmetry, Lateral dominance
ABSTRACT
Two hundred thirty-five (235) normal male participants of the
Baltimore Longitudinal Study were classified as right handed, left handed, and
ambidextrous on the basis of their grip-strength performance. Their left and right
hands were also radiographed and the measurements of the second metacarpal
bones were evaluated on the basis of hand dominance. The results indicated that, as
a rule, the right hand measurements are higher than those of the left hand,
regardless of hand dominance. The bilateral differences in total width, length, total
area and cortical area are significant among the right hand dominant and nonsignificant among the left hand dominant. Regardless of hand dominance the bilateral
differences in medullary width are nonsignificant. These results suggest an inherent tendency of the right second metacarpal to have more bone than the left
regardless of hand dominance. Differential stress due to hand dominance will
increase the bilateral difference in the right handed and reduce it in the left
handed.
In a previous study (Platoet al., '78) we found
that the right second metacarpal bones of normal male participants of the Baltimore Longitudinal Study (BLS) of the Gerontology Research Center (GRC), were on the average
longer, wider and have larger bone mass than
the respective second metacarpal of the left
hand. Since most participants were right
handed, it became of interest to evaluate the
possible association of lateral dominance with
bone size and mass. Studies by Buskirk et al.
('56) and Watson ('73) indicated that participation in sports, which primarily involve the use
of one hand, may result in bilateral asymmetry
in growth pattern of certain bones.
Buskirk and his associates ('56) found a significant increase in the length of ulna and
radius in the dominant hand of a group of tennis players, while in non-tennis players only
the length of the ulna showed significant bilateral differences. There were no differences, in
either group, in thickness of bone cortex,
medullary diameter or diameters of the distal
or proximal heads of either the ulna or radius.
More recently, Watson ('731, using photon absorptiometry, studied bone mineral content in
the humerus, ulna and radius of a group of
0002-9483/80/5201-0027
$01.40 0 1980 ALAN R. LISS, INC.
young baseball players. He found significantly
higher mineral content in the humerus of the
dominant hand; however, there was no consistent trend for lateral dominance in mineral
content in either the ulna or the radius.
Garn and his associates ('76) studied, by
handedness, the bilateral differences in total
area, cortical area and percent cortical area of
the second metacarpal in a sample of male and
female patients with chronic renal disease.
Their results showed that both the right and
left handed patients have, on the average,
larger total and cortical areas in the right
hands than the left. Only among the right
handed, however, were the bilateral differences
significant.
The objective of the present study is to evaluate the bilateral differences in bone measurements and their possible association with
lateral hand dominance in a sample of males
representing a wide range of ages.
MATERIAL AND METHOD
Two hundred thirty-five (235) male participants of the Baltimore Longitudinal Study,
who had bilateral hand x-rays and had been
evaluated for grip-strength at two or more vis-
27
28
C.C.PLATO, J.L. WOOD,AND A.H.NORRIS
its were selected for this study. All participants
were Caucasian volunteers between the ages of
25 and 95, and of above-average education and
socioeconomic status. The Longitudinal Study
sample which, until January 1978, consisted of
only male volunteers, is described in detail
elsewhere (Stone and Norris, ’66).The subjects
of the present study differed from those of Garn
et a1 (’76)in that, with one possible exception,
they did not suffer of chronic renal disease, as
judged from physical examination and supported by creatinine clearance studies. Of the
235 participants, only five had creatinine
clearance values below 80. Of these, three were
in the range of 70-79, one had 61 and one, an
active 90-year-old participant had a creatinine
clearance value of 43. Left and right hand
measurements were made “blindly,” by the
same individual, on the I1 metacarpal bone as
described by Garn (’70,and personal communication, 1974) for total width (TW), medullary
width (MW)and length (LEN) as shown in Figure 1A and 1B. Repeat measurements on 25
randomly selected participants showed a nonsignificant intraobserver variation. From these
three basic measurements we derived the combined cortical thickness (CCT), which is the
difference between the total and medullary
widths, the total area (TA), the cortical area
(CAI and the percent cortical area (PCA) (Fig.
C). The latter is the ratio of CAPTA x 100. The
three area variables were chosen for further
discussion in order to make our results comparable with those of Garn et al. (’76).The gripstrength value was derived by averaging the
higher two grip scores (in kilograms) of each
participant using a Stoelting hand dynamometer. The participants were separated into three
laterality groups determined by subtracting
the left from the right (R - L) grip-score values.
A participant was classified as right hand dominant if R -L 2 1.0 kg, and as left hand dominant if R - L s - 1.0 kg. Participants with
differences between - 0.999 and 0.999 kilograms were considered as having no bilateral
dominance, ie, ambidextrous.
The bilateral differences were tested for significance by Student’s t-test for paired comparisons.
RESULTS AND DISCUSSION
One hundred eighty participants were classified as right hand dominant. Their average
age was 59.0 years. Thirty-six were classified
as left hand dominant and nineteen as ambidextrous with mean ages of 59.4 and 53.5
years, respectively. Grip-strength was selected
as the determinant of hand dominance because
of the availability of the data. Recently, we
have also been testing the same individuals for
“handedness” through a series of activities indicating hand, foot and eye preference. However, at this time we do not have sufficient
“handedness” data to be included in this discussion.
The means and standard errors of the various
bone measurements for the left and right hands
of the three laterality groups are given in Table
1. This table also presents the mean paired
bilateral differences (R - L), their respective
standard errors and the t values resulting from
each comparison. Positive differences indicate
higher values in the right hands and negative
higher values in the left.
The results of Table 1, first show that, with
the exception of the percent cortical area of the
left hand dominant and the length of the ambidextrous, all values of the right hand measurements are higher than those of the left. Second, there are no significant bilateral differences in medullary width and percent cortical
area in any of the three groups. Third, there are
no significant bilateral differences in any of the
bone measurements in the left hand dominant
group. Fourth, there are highly significant ( P <
0.001) bilateral differences in total width,
length, total area, and cortical area in the right
hand dominant group. Fifth, the ambidextrous
show significant differences, though not as
pronounced as those of the right hand dominant
group, in total width, total area, and cortical
area.
The bilateral differences in total area and
cortical area, of the left and right hand dominant, seen in Table 1, are similar to those reported by Garn and his associates (’76).In both
studies the right hand dominant displayed significantly larger bone area and mass in the
right hand, while the bilateral differences of
the left hand dominant are not significant.
The average bone measurements reported
herewith are higher than those found by Garn,
et al. (’76). This is not unexpected however,
since in the latter study, measurements of the
male and female were pooled, and the sample
consisted of patients with chronic renal disease.
These sampling differences as well as the difference in determining lateral dominance
(handedness vs grip-strength) may also be responsible for the significant bilateral differences they found in the percent cortical area.
Table 2 presents qualitative bilateral comparisons for the three basic bone measurements, total width, medullary width, and
A
B
-
1
=
TOTAL WIDTH
MEDULLARY WIDTH
=
4
M W = DISTANCE 2 T 0 3
CCT=lW-MW
MA =MEDULLARYAREA
CA = CORTICAL AREA
TA =MA+CA
lW = DISTANCE 1 TO 4
TOTAL WIDTH - MED. WIDTH = CCT
DARK AREA
ARROW, TO ARROW2
Fig. 1. Measurements of the I1 Metacarpal Bone.
a . Determination of bone midshaft.
b. Derivation ofthe three basic measurements, Total Width, Medullary Width and Length
c. Graphic cross-section of bone showing the various bone measurements.
(Modified after Garn 1’74).)
C
1
BONE
LENGTH
SECOND METACARPAL
m
rl
E
U
%U
3:
3
m
%tl
5
M
z
5*
2
!8
I?
30
C.C. PLATO, J.L. WOOD, AND A.H. NORRIS
T A B L E 1. Means and standard errors o f I1 metacarpal measurements of 235 normal males
I1 Metacarpal bone
Left hands
Right hands
Right-left paired
differences
measurements
Mean
Mean
SE
Mean
SE
t'
0.06
0.07
0.28
0.88
0.68
0.53
9.65
4.03
70.58
73.60
60.10
82.11
0.06
0.07
0.28
0.90
0.70
0.52
0.28
0.06
0.39
4.19
3.79
0.59
0.04
0.05
0.10
0.57
0.54
0.38
7.21**
1.27
4.04""
7.32**
7.05**
1.57
Left hand dominance, N = 36, mean age = 59.4
Total width (mmj
9.41
Medullary width (mm)
4.05
Length (mm)
70.87
Total area (mm2)
69.86
Cortical area imm')
56.23
Percent cortical area (%I
80.80
0.11
0.16
0.68
1.67
1.40
1.25
9.49
4.14
71.27
71.21
56.75
80.19
0.12
0.19
0.65
1.82
1.44
1.43
0.09
0.09
0.40
1.34
0.52
-0.60
0.10
0.11
0.21
1.45
1.20
0.91
0.90
0.80
1.89
0.93
0.43
0.66
N o bilateral dominance, N
Total width (mm)
Medullary width (mm)
Length (mm)
Total area ( m m 9
Cortical area (mm?
Percent cortical area (5%)
0.15
0.22
0.94
2.17
1.94
1.74
9.43
3.58
68.46
70.00
59.27
84.91
0.12
0.21
0.95
1.76
1.60
1.50
0.34
0.11
-0.40
4.88
4.34
24
0.11
0.16
0.30
1.69
1.40
1.19
3.00**
0 69
1.36
2 88'*
3.0P
0 20
Right hand dominance, N
Total width imm)
Medullary width (mmj
Length (mi
Total area (mm'j
Cortical area (mm')
Percent cortical area (%)
=
180, m a n age
SE
=
59.0
9.37
3.97
70.19
69.41
56.32
81.52
=
19, mean age
=
9.08
3.47
68.86
65.13
54.93
84.67
53.5
I t = test values were calculated hefore rounding off
= P
0.01.
Results are presented by hand, paired bilateral difference, and by lateral dominance as determned by gripstrength scores.
*m
1
TABLE 2. Number of indiuiduals showing bilateral asymmetry for the three basic bone
measurements and combined cortical thickness ICCTI. (separated by hand dominance)
Number of
observations'
Hand
dominance
Bone
measurement
R>L
L>R
Chisquare'
Right
Total width
Medullary width
CCT
Length
122
90
117
110
45
74
56
64
35 544
16
21 5"*
12 T *
Left
Total width
Medullary width
CCT
Length
19
21
18
17
15
15
17
15
0.5
1.0
0.3
0.1
Ambidextrous
Total width
Medullary width
CCT
Length
11
8
13
12
2
8
4
7
6.2"
0
4.84.
1.3
~~
I, observations are not included in this table
under the hypothesis that R 2 L = L R
*P<005
** P c 0 001
I
R
=
31
BILATERAL BONE MEASUREMENTS AND HAND DOMINANCE
length. The first column of this table gives the
number of participants with larger values in
the right hand, R > L, and the second column
the number of those with higher values in the
left hand, L > R. Participants with similar
measurements in both hands are not included
in this table. The last column gives the chisquare value under the hypothesis that there
should be as many R > L as L > R measurements.
The right hand dominant group has significantly (P < 0.001) higher number of R > L
measurements for both the total width and
length. The left hand dominant group comparisons show no significant differences between R
> L and L > R, while the ambidextrous have
significantly ( P < 0.05) higher R > L than L >
R only in total width. As in Table 1,there are no
significant differences in any of the bilateral
comparisons involving the medullary width.
The consistent absence of significant bilateral differences in medullary width indicates
that the larger area and mass of bone, seen in
the right second metacarpal, is not due to differential bone resporption from the medullary
area. Rather it results from differential bone
apposition at the external surface, which influences the total width.
In our earlier study (Platoet al., '78) we found
no significant correlation between age (after
the age of thirty) and total width of the second
metacarpal of either the left or right hand. In
that study we also showed that the right hands
have significantly higher total width than the
left in all age groups from 25-90 years with a
paired bilateral mean difference of 0.26 i 0.03
mm. It seems then, that differential stress, due
to hand dominance, would have to affect bone
size during the early life.
The larger, although statistically not significant, bone size of the right second metacarpal of
the left hand dominant participants suggests
that hand dominance may not be the only factor
contributing to the bilateral difference in bone
size. Garn suggested that left hand dominant
individuals may actually be using their right
hands to a greater extent than it is thought that
they do. This explanation may account for the
relatively high bone measurements of the right
hands of the left hand dominant, but it would
not account for these values (right hand) being
higher than those of the left hands. It seems
that there is an inherent tendency for larger
bone in the right side regardless of lateral dominance. Right hand dominance will increase
this difference by enhancing bone apposition on
the right hands while left hand dominance will
reduce this bilateral difference to being nonsignificant by contributing to increase of bone
in the left hand.
LITERATURE CITED
Buskirk, E.R., K.L. Andersen, and J. Brozek (1956) Unilateral activity and bone and muscle development in the
forearms. Res. 27: 127-131.
Garn, S.M. (1970)The Earlier Gain and Later Loss of Cortical Bone. C.C. Thomas, Springfield, Ill.
Garn, S.M. ( 1974) Personal communication.
Garn, S.M., G.H. Mayor, and H.A. Shaw (1976) Paradoxical
bilateral asymmetry in bone size and bone mass in the
hand. Am. J. Phys. Anthropol. 45:209-210.
Plato, C.C., J. Wood, and A.H. Norris (1978)Cross-Sectional
a nd Longitudinal Changes in Bone Loss. Book of
Abstracts. D. 112. Presented at the 31st Annual Scientific
Meeting 07 the Gerontological Society, Dallas, TX ,
November 1978 (Manuscrmt in Dress
Stone, J.L., and A.H. Norris (1966)Activities and attitudes of
participants in the Baltimore Longitudinal Study. J.
Gerontol. 21.575-580.
Watson, R.C. ( 1973) Bone growth and physical activity in
young males. In: International Conference on Bone Mineral Measurement. R.B. Mazess, ed. U.S. DHEW Publication No. (NIH) 75-683. U S . Government Printing Office.
Washington, D.C. pp. 380-386.
.
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