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Fusion of coccyx to sacrum in humans Prevalence correlates and effect on pelvic size with obstetrical and evolutionary implications.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 145:426–437 (2011)
Fusion of Coccyx to Sacrum in Humans: Prevalence,
Correlates, and Effect on Pelvic Size, With Obstetrical
and Evolutionary Implications
Robert G. Tague*
Department of Geography and Anthropology, Louisiana State University, Baton Rouge, LA 70803-4105
KEY WORDS
obstetrics; pelvis; sacral–coccygeal fusion; sexual dimorphism
ABSTRACT
Humans do not have a tail, but we have
four rudimentary coccygeal vertebrae. This study considers several issues pertaining to fusion of the coccyx to the
sacrum, including prevalence, sexual differences, effect on
pelvic size, and obstetrical and evolutionary implications.
Previous research on sacral–coccygeal fusion has
reported: (1) lower prevalence in females than males, (2)
prevalence increases with age, (3) range in prevalence
among 13 samples from 0 to 72%, and (4) obstetrical complications. This study uses a sample of 2,354 American
skeletons of known sex, age 20 years and older to ascertain prevalence of sacral–coccygeal fusion and to evaluate
some of its correlates. Results show that the sexes do not
differ in prevalence of sacral–coccygeal fusion for five of
seven decades of life, but that prevalence does increase
with advancing age—from 24 to 47% from the third to
eighth decades of life in females. Pelvimetric analysis of
132 females shows that those with sacral–coccygeal fusion
have a shorter posterior sagittal diameter of the outlet
compared to those without fusion; more than half of those
with sacral–coccygeal fusion have an obstetrically contracted posterior sagittal diameter. Shortening of the posterior sagittal diameter is important, because its conjoint
occurrence with a narrow subpubic arch may result in an
obstetrically inadequate outlet. This study concludes that
sacral–coccygeal fusion is a principal contributor to the
evolution of sexual dimorphism in sacral angulation,
which is a determinant of the length of the posterior sagittal diameter of the outlet. Am J Phys Anthropol
145:426–437, 2011. V 2011 Wiley-Liss, Inc.
Humans do not have a tail. Nevertheless, we retain
‘‘rudimentary’’ (Standring, 2005: 754) and ‘‘vestigial’’
(Willis, 1923: 95; Last, 1978: 459; Spinney, 2008: 45) tail
bones—coccygeal vertebrae. This study considers several
issues pertaining to fusion of the coccyx to the sacrum,
including its prevalence, sexual differences, effect on pelvic size, and obstetrical implications.
The number of coccygeal vertebrae in humans ranges
from two to five, with four being the mode (Paterson,
1893; Staderini, 1894; Dieulafé, 1933; Duncan, 1937;
Schultz and Straus, 1945). Duncan (1937) reported that
there is no difference between the sexes in number of
coccygeal vertebrae, but Breathnach (1965) stated that
the sexes do differ in this number, with females having
four or fewer vertebrae and males having four or more.
Despite their diminutive size, these vertebrae are functional, serving as site of attachment for four muscles—
coccygeus, gluteus maximus, levator ani, and sphincter
ani externus—and several ligaments, including sacrospinous and sacrotuberous, as well as those binding coccyx
to sacrum (Standring, 2005). The coccyx can be a locus
of pain, affecting females more often than males
(Duncan, 1937; Wilkinson, 1947). Trauma to the coccyx,
including its fracture or dislocation during delivery, is
the most frequent cause of this pain [Moir, 1947; Morris,
1947; Brunskill and Swan, 1987; Peyton, 1988; Wray et
al., 1991; Jones et al., 1997; but see Wilkinson (1947)
and Cooper (1960)].
The sacral–coccygeal and intercoccygeal joints are typically symphyseal, although both can be synovial
(Standring, 2005). Although the coccyx is mobile at its
articulation with the sacrum (Bø et al., 2001; Standring,
2005; Grassi et al., 2007), this study considers issues
pertaining to sacral–coccygeal fusion. Based on 13
samples reported in the literature, the prevalence of sacral–coccygeal fusion ranges from 0 to 71.7% (Table 1).
The reason for intersample differences in prevalence in
sacral–coccygeal fusion is not known, but Merbs (1974:
16) observed that ‘‘New World aborigines, at least those
occupying the more northerly regions of the hemisphere,
exhibit a strong tendency toward caudal shift [of the vertebral column].’’ Caudal shift of the vertebral column
can be systemic or regional; caudal shift includes sacral–
coccygeal fusion.
A coccyx that is not fused to the sacrum is of little
obstetrical importance (Morris, 1947), because the coccyx
can extend at the sacral–coccygeal joint (Bø et al., 2001;
Grassi et al., 2007), thereby increasing pelvic outlet
capacity at delivery. Williams (1918: 739) also argued
that sacral–coccygeal fusion ‘‘is without obstetrical significance, as its only effect is to increase the length of
the sacrum.’’ However, others contend that sacral–
coccygeal fusion is obstetrically important: ‘‘prominent
coccyx with anterior angulation and ankylosis at the
sacrococcygeal articulation . . . may hinder natural deliv-
C 2011
V
WILEY-LISS, INC.
C
Additional Supporting Information may be found in the online
version of this article.
*Correspondence to: Robert G. Tague, Department of Geography
and Anthropology, Louisiana State University, Baton Rouge, LA
70803-4105. E-mail: rtague@lsu.edu
Received 1 July 2010; accepted 30 January 2011
DOI 10.1002/ajpa.21518
Published online 3 May 2011 in Wiley Online Library
(wileyonlinelibrary.com).
427
SACRAL–COCCYGEAL FUSION IN HUMANS
a
TABLE 1. Prevalence of sacral-coccygeal fusion among 13 samples reported in the literature
Sample—geographical
location (population)
Prevalence of
sacral-coccygeal
fusion (n)
Method by which sacrum
was analyzed—dry bone
or radiograph
Italy
London
South Africa (Cape Bush)
United States
South Africa (Bantu)
Peru, highlands (prehistoric)
New Zealand (Maori)
London
Rome
0%
2.0%
16.0%
17.5%
20.0%
27.1%
28.0%
33.0%
36.7%
Northwest Coast North America
(Native American)
Northwest Territories,
Canada (Eskimo)
Aberdeen
France (most or all individuals)
37.1% (26 of 70)
Dry bone
Grassi et al. (2007)
Young and Ince (1940)
Slome (1929)
Duncan (1937)
Shore (1930)
MacCurdy (1923)
Scott (1893)
Saluja (1988)
Postacchini and
Massobrio (1983)
Merbs (1974)
50.0% (35 of 70)
Dry bone
Merbs (1974)
67.6% (23 of 34)
71.7% (99 of 138)
Dry bone
Dry bone
Saluja (1988)
Dieulafé (1933)
a
(0 of 112)
(10 of 510)
(4 of 25)
(35 of 200)
(17 of 87)
(13 of 48)
(7 of 25)
(31 of 94)
(44 of 120)
Reference
Radiograph
Radiograph
Dry bone
Radiograph
Dry bone
Dry bone
Dry bone
Dry bone
Radiograph
Dieulafé (1933: 43, 67, Table 2) stated that his sample size was 136, but his Table 2 shows data for 138 individuals.
ery’’ (Guerriero et al., 1940: 841); ‘‘[i]f the coccyx . . . is . . .
ankylosed it may form an obstruction to labor’’ (Anon,
1946: 420); and ‘‘if the coccyx [is fused to the sacrum
and] also projects sharply forward . . . it may then
obstruct delivery’’ (Moir, 1947: 20). There are a number
of case reports in which sacral–coccygeal fusion necessitated operative intervention for successful delivery,
including use of forceps, cesarean section, and operative
fracture of the synostosed coccyx (Graff, 1924; Jarcho,
1933; Morris, 1947; Ernst, 1950; Fliegner, 1987; Peyton,
1988).
As sacral–coccygeal fusion has obstetrical consequences, sexual differences in its prevalence and age at onset
may be expected. MacCurdy (1923) reported that 0% of
females (n 5 22) but 50% of males (13 of 26) had sacral–
coccygeal fusion in a sample of prehistoric Peruvians.
Saluja (1988) reported that females have a lower prevalence of sacral–coccygeal fusion than males in an historic
sample from London (22.5% vs. 40.7% in samples of 40
and 54, respectively), but not in one from Aberdeen
(66.7% for females and 68.4% for males in samples of 15
and 19, respectively). Duncan (1937: 1090) stated that,
‘‘In advanced life the coccyx may join with the sacrum,
the union occurring earlier and more frequently in the
male than in the female.’’ Saluja (1988) also observed a
sexual difference in age of sacral–coccygeal fusion, with
males over age 40 having a higher prevalence than those
younger than this age, but females did not show this age
difference in prevalence.
Collectively, previous research suggests that sacral–
coccygeal fusion is an obstetrical hazard, occurs less frequently in females than males, and occurs principally
among individuals of advanced age. However, previous
research is not uniform in these results, and samples differ markedly in their prevalence of sacral–coccygeal
fusion. Therefore, the present study was undertaken to
address the following issues pertaining to sacral–coccygeal fusion: (1) prevalence in females and males, including number of fused coccygeal vertebrae, (2) association
with age, fusion between presacral vertebrae, and sacral–lumbar fusion, and (3) effect on pelvic size. The
reason for this study is to understand the impact of
sacral–coccygeal fusion on obstetrical success and
TABLE 2. Sample distribution by sex, age at death,
and ancestrya
Females
Age at death
20–29
30–39
40–49
50–59
60–69
70–79
80–89
90–99
1001
Males
Black
White
Black
White
98
102
85
62
33
29
20
5
2
15
30
46
55
64
56
33
2
0
168
264
254
89
63
21
2
0
0
51
158
306
98
84
46
13
0
0
a
‘‘Black’’ and ‘‘white’’ imply African and European ancestry,
respectively.
whether this fusion has contributed to the evolution of
pelvic sexual dimorphism.
MATERIALS AND METHODS
Skeletons of 2,354 humans from the Hamann-Todd
Osteological and Robert J. Terry Anatomical Collections
were used in this study. Both collections consist principally of individuals who were not claimed by relatives
from morgues and hospitals in or near Cleveland, Ohio,
USA (Hamann-Todd Collection) and St. Louis, Missouri,
USA (Terry Collection) from the late-19th to the middle20th centuries (Hunt and Albanese, 2005; Kern, 2006).
Only individuals 20 years of age and older were used.
The sample consisted of 436 black females, 301 white
females, 861 black males, and 756 white males; the sample of females represented all of those available in these
Collections. Museum records were used for information
on age, sex, and ancestry; the classifications ‘‘black’’ and
‘‘white’’ imply African and European ancestry, respectively (Table 2).
Individuals were included in this study only if they
had the modal number of presacral vertebrae—24
American Journal of Physical Anthropology
428
R.G. TAGUE
(Schultz and Straus, 1945; Standring, 2005). As a result
of this stipulation, 255 individuals who had been surveyed were removed from the sample, because they had
23 or 25 presacral vertebrae (i.e., initial sample surveyed was 2,609 individuals). The reason for using only
individuals with 24 presacral vertebrae was to eliminate the potentially confounding effect of cranial and
caudal shifting of vertebrae on the identification of sacral–coccygeal fusion. For example, cranial shifting
results in complete transformation of the 24th vertebra,
which is modally the fifth lumbar, into the first sacral
vertebra. The result is 23 presacral vertebrae and a 6
segment sacrum. However, because the 24th vertebra is
not identifiably lumbar, the sacrum may be misclassified as having coccygeal fusion. Caudal shifting, in
turn, results in complete transformation of the 25th
vertebra, which is modally the first sacral, into a lumbar vertebra. This can be accompanied by the 30th vertebra, which is modally the first coccygeal, becoming
assimilated with the sacrum. The result is 25 presacral
vertebrae and a 5 segment sacrum. However, the sacrum may not show identifiable sacral–coccygeal fusion.
Derry (1912: 189) similarly observed that, ‘‘As the first
sacral vertebra tends to be released from the sacrum,
so an additional vertebra tends to be taken in from the
caudal series.’’
Individuals were also included in the study only if the
superior and inferior aspects of the sacrum were complete enough to ascertain with certainty the number of
fused vertebrae. The modal number of sacral vertebrae
is five (Schultz and Straus, 1945; Abitbol, 1987; Standring, 2005). For sacra with six or more fused vertebrae,
the following methodology was used to determine
whether the extra vertebra(-e) was lumbar or coccygeal.
First, the number of fused sacral vertebrae was counted.
Second, the sacrum was evaluated to determine whether
a lumbar vertebra was fused to it (i.e., incomplete cranial shifting wherein the lumbar vertebra was identifiable). Third, if the sacrum had six vertebrae and did not
show lumbar fusion, then it was classified as coccygeal
fusion. Some sacra with seven or more vertebrae had
dual lumbar and coccygeal fusion. A lumbar vertebra
that was fused to the sacrum was included in the count
of presacral vertebrae. Anatomies that were used to
identify sacral–lumbar fusion included the following
(Tague, 2009). First, in the absence of sacral–lumbar
fusion, the arcuate line of the ilium, which demarcates
the false pelvis from the true pelvis, becomes confluent
posteriorly with the body of the first sacral vertebra
when the sacrum and hipbone are articulated. Visually,
this confluence is at or above the transverse ridge
between the first and second sacral vertebrae, or alternatively stated, at or above the first anterior foramen of
the sacrum. With sacral–lumbar fusion, the body of the
fused lumbar vertebra is entirely superior to the arcuate
line. Second, the body of the fused lumbar vertebra is
sometimes retroflexed, creating two promontories
(Kirchhoff and Kräubig, 1957). Third, the bodies of the
fused lumbar and sacral vertebrae are sometimes widely
separated anteriorly. The bodies may or may not be connected to one another by a bony bridge. Fourth, the lumbar vertebra fused to the sacrum does not contribute to
the auricular surface in the majority of cases (Tague,
2009). In contrast, the first sacral vertebra always contributes to the auricular surface (Scheuer and Black,
2000; Standring, 2005).
American Journal of Physical Anthropology
Pelves were measured for 132 females—72 (42 blacks
and 30 whites) without sacral–coccygeal fusion or sacral–
lumbar fusion and with a 5 segment sacrum—and 60 (31
blacks and 29 whites) with sacral–coccygeal fusion involving only the first coccygeal vertebra (i.e., 6 segment sacrum). Only individuals who were 25–49 years of age were
used in the pelvimetric analysis. Individuals 20–24 years
of age were not included, because the linea terminalis
may continue to grow in the early part of the third decade
of life in females [Tague, 1994; but see Fuller (1998)]. Individuals 50 years of age and older were not used, because
females are generally considered to be reproductively senescent by age 50 (McFalls, 2007). To take some pelvic
measurements, the hipbones were articulated with the
sacrum and held together with thin strips of adhesive
tape and rubber bands. The pubes touched in the midline;
no compensation was made for a symphyseal disk. Seventeen variables of the hipbone, sacrum, and articulated pelvis were measured, seven variables were computed from
these measurements, and three nonpelvic variables were
measured (Fig. 1; Appendix 1). Two nonpelvic variables—
lengths of femur and clavicle—were measured to the nearest millimeter using an osteometric board. Sliding calipers
were used for all other measurements, which were taken
to the nearest 0.1 mm. From this suite of variables, 15 pelvic and the 3 nonpelvic variables were analyzed and
reported here. Within each sample, difference among variables in number of individuals was due to damage to
bones. The nine variables not reported in this study were
taken in order to compute some of the variables that are
reported. The three nonpelvic measurements—lengths of
the femur and clavicle and head diameter of the femur—
are skeletal correlates of stature, shoulder breadth, and
_ can, 1986; Felbody mass, respectively (Krogman and Is
desman et al., 1990; Ruff et al., 1991; Feldesman and
Fountain, 1996; Walrath and Glantz, 1996; Tague, 2000).
Anteroposterior and posterior sagittal diameters of the
outlet and sacral length were measured from the fifth sacral vertebra in individuals without sacral–coccygeal
fusion and from the first coccygeal vertebra in individuals
with fusion. Despite the different point of measurement
for these three variables, direct comparison of individuals
with and without sacral–coccygeal fusion is appropriate,
because these dimensions are obstetrically comparable.
Morris (1947) argued that the anteroposterior and posterior sagittal diameters of the outlet should be measured
from the lowest fixed point of the sacrum, that is, from the
coccyx when it is fused to the sacrum.
For the 18 variables reported in this study, 26 individuals had been remeasured in a previous study to evaluate the level of intraobserver measurement and computational precision (Tague, 2009). The level of precision
was 0.98 or higher for 17 variables and 0.95 for posterior
sagittal diameter of inlet.
Precision ¼ 1 ðjoriginal value repeat valuej=
original valueÞ
ð1Þ
PASW Statistics 18 (2010) was used for all statistical
analyses but partition analysis, which was done with a
scientific calculator. For analyses of associations between
categorical variables, chi-square test, Fisher’s exact test,
and partition analysis were used. Fisher’s exact test was
used when sample size was small, and partition analysis
SACRAL–COCCYGEAL FUSION IN HUMANS
429
Fig. 1. Osteological and computed points for pelvic variables. Orientations of pelvic bones: (A and E) medial view of sacrum and
left hipbone articulated; (B) medial view of left hipbone; (C) superior view of pelvis; and (D) posterior view of pelvis. Osteological
points: (a) promontory of sacrum; (b) superomedial border of pubic symphysis; (c) transverse ridge between fourth and fifth sacral
vertebrae; (d) inferomedial border of pubic symphysis; (e) apex of fifth sacral vertebra for individuals without sacral–coccygeal
fusion or of first coccygeal vertebra for those with sacral–coccygeal fusion; (f) ischial spine; (g) medial border of transverse ridge of
ischial tuberosity; (h) point of articulation between sacrum and confluence of apex of auricular surface of ilium and arcuate line; (i)
posterior inferior iliac spine; (j) point along linea terminalis representing maximum transverse diameter of inlet. Computed points:
k, m, and n, midpoints of transverse diameters of inlet, midplane, and outlet, respectively; and l, midpoint of sacral breadth. Solid
lines are directly measured variables; dashed lines are computed variables. Figure 1 is reproduced from Tague (2009: 432, Fig. 3);
Figure 1A,C,D,E is reproduced or modified from Tague and Lovejoy (1998: 84, Fig. 1).
was used as a post hoc test when the preceding chi-square
test having more than one degree of freedom was significant (Siegel and Castellan, 1988). Pearson’s product–
moment correlation coefficient analysis was used to test
for an association between two of the pelvic variables. The
Student’s t test was used to test for a difference in means
between females with and without sacral–coccygeal
fusion. The Mann–Whitney test was used in place of
the Student’s t test if the assumptions of the latter were
not satisfied (i.e., samples derived from normal populations with equal variances). The level of significance
was set at P 0.05, but this level was adjusted by applying Bonferroni’s correction when there were multiple
comparisons.
RESULTS
The first issue is to determine the appropriateness of
combining blacks and whites into a single sample for
analysis. Using the chi-square test and Fisher’s exact
test to compare the prevalence of sacral–coccygeal fusion
in blacks and whites by decade of age at death within
each sex, results show one significant difference among
eight decades for females (Table 3; prevalence of fusion
is higher in whites than blacks for age group 50–59, X2
5 20.237, df 5 1, P \ 0.001) and one significant differ-
ence among seven decades for males (prevalence of
fusion is higher in whites than blacks for age group 40–
49, X2 5 21.766, df 5 1, P \ 0.001). These results suggest that combining blacks and whites into a single sample for further analyses of prevalence of sacral–coccygeal
fusion is appropriate.
The second issue is to determine whether females and
males differ in their prevalence of sacral–coccygeal fusion.
Chi-square analysis shows two significant differences
among seven decades—females have a significantly lower
prevalence than males for decades 40–49 (Table 4; X2 5
17.148, df 5 1, P \ 0.001) and 80–89 (X2 5 16.124, df 5 1,
P \ 0.001).
The third issue is to determine whether sacral–coccygeal fusion is related to age at death; the sexes are analyzed separately. Chi-square analysis shows a significant
relationship between these variables in both females and
males (Table 4; for females, X2 5 20.764, df 5 7, P 5
0.004, with individuals age 1001 not included in the
analysis due to small sample size; for males, X2 5
57.314, df 5 6, P \ 0.001). Partition analysis of this contingency table shows the following results for males: (1)
prevalence of sacral–coccygeal fusion is not significantly
different between the decades 20–29 and 30–39, and
prevalence of this fusion is not significantly different
among the decades 40–49, 50–59, 60–69, and 70–79; and
American Journal of Physical Anthropology
430
American Journal of Physical Anthropology
a
‘‘Black’’ and ‘‘white’’ imply African and European ancestry, respectively. Level of significance set at P 0.006 for comparison of females and P 0.007 for comparison of males,
based on Bonferroni correction; significant results are underlined.
0.962
0.608
\0.001
0.038
0.140
0.009
1.000 (FE)
–
–
51
158
306
98
84
46
13
–
–
(29.4)
(39.2)
(57.2)
(51.0)
(53.6)
(71.7)
(100.0)
–
–
15
62
175
50
45
33
13
(70.6)
(60.8)
(42.8)
(49.0)
(46.4)
(28.3)
(0.0)
–
–
36
96
131
48
39
13
0
168
264
254
89
63
21
2
–
–
(29.8)
(36.7)
(37.4)
(36.0)
(41.3)
(38.1)
(100.0)
–
–
50
97
95
32
26
8
2
(70.2)
(63.3)
(62.6)
(64.0)
(58.7)
(61.9)
(0.0)
–
–
118
167
159
57
37
13
0
1.000 (FE)
0.028
0.221
\0.001
0.397
0.767
0.058
1.000 (FE)
–
15
30
46
55
64
56
33
2
–
(20.0)
(56.7)
(34.8)
(61.8)
(48.4)
(48.2)
(51.5)
(50.0)
–
3
17
16
34
31
27
17
1
(80.0)
(43.3)
(65.2)
(38.2)
(51.6)
(51.8)
(48.5)
(50.0)
–
12
13
30
21
33
29
16
1
98
102
85
62
33
29
20
5
2
24
35
21
13
13
13
5
1
2
20–29
30–39
40–49
50–59
60–69
70–79
80–89
90–99
1001
(75.5)
(65.7)
(75.3)
(79.0)
(60.6)
(55.2)
(75.0)
(80.0)
(0.0)
74
67
64
49
20
16
15
4
0
(24.5)
(34.3)
(24.7)
(21.0)
(39.4)
(44.8)
(25.0)
(20.0)
(100.0)
Prob.
Total n
Yes n (%)
Whites
No n (%)
Total n
Yes n (%)
Age at death
No n (%)
Total n
No n (%)
Yes n (%)
Total n
Prob.
No n (%)
Yes n (%)
Males: sacral–coccygeal fusion
Blacks
Females: sacral–coccygeal fusion
Whites
Blacks
TABLE 3. Number of individuals with, and prevalence of, fusion and without fusion of coccyx to sacrum by sex, ancestry, and age at death; chi-square test and Fisher’s exact (FE)
test used to compare blacks and whites within each sex by decade of age at death; probability (Prob.) based on chi-square test unless otherwise indicateda
R.G. TAGUE
(2) age group 20–39 has a significantly lower prevalence
of sacral–coccygeal fusion than age group 40–79, which,
in turn, has a significantly lower prevalence than age
group 80–89 (Supporting Information Table S1). For
females, partition analysis shows no significant difference in prevalence of sacral–coccygeal fusion among the
eight decades analyzed: 20–29 through 90–99 (Table S1).
The inconsistency in results for females between the
chi-square test and the partition analysis is discussed
below.
The fourth issue is whether the sexes differ in number
of coccygeal vertebrae fused to the sacrum. Chi-square
analysis shows no significant association between sex
and number of coccygeal vertebrae fused to the sacrum
(Table 5; X2 5 0.478, df 5 3, P 5 0.924). For the combined sample of females and males with sacral–coccygeal
fusion (n 5 976), the percentages of individuals with
one, two, three, and four coccygeal vertebrae fused to
the sacrum are 93.8% (n 5 915), 4.7% (n 5 46), 1.4%
(n 5 14), and 0.1% (n 5 1), respectively.
The fifth issue is to determine whether sacral–coccygeal fusion is related to fusion between presacral vertebrae and to sacral–lumbar fusion; the sexes are analyzed
separately. Chi-square analysis shows significant associations in males between sacral–coccygeal fusion and
both fusion between presacral vertebrae and sacral–
lumbar fusion, but the relationships are nonsignificant
in females (Table 6; for sacral–coccygeal fusion and
fusion between presacral vertebrae—males, X2 5 12.352,
df 5 1, P \ 0.001, and females, X2 5 2.640, df 5 1, P 5
0.104; for sacral–coccygeal fusion and sacral–lumbar
fusion—males, X2 5 11.119, df 5 1, P 5 0.001, and
females, X2 5 0.890, df 5 1, P 5 0.346). In males, dual
sacral–coccygeal fusion and fusion between presacral
vertebrae occur in 5.8% of individuals (91 of 1,579),
which is more frequent than expected by chance. In contrast, dual sacral–coccygeal fusion and sacral–lumbar
fusion occur in 0.5% of males (8 of 1,617), which is less
frequent than expected by chance.
The sixth issue is to determine whether females with
sacral–coccygeal fusion differ from those without fusion
in pelvic or nonpelvic size. Blacks and whites are analyzed separately.1 Use of the Student’s t test and Mann–
Whitney test shows the following significant results: (1)
in both blacks and whites, individuals with sacral–coccygeal fusion have a shorter posterior sagittal diameter
of the outlet than those without fusion, and (2) in whites
only, those with sacral–coccygeal fusion have a shorter
anteroposterior diameter of the outlet and longer sacrum
than those without fusion (Table 7).
DISCUSSION
Results of this study show that blacks and whites are
comparable in their prevalence of sacral–coccygeal
fusion. This study also shows that sacral–coccygeal
fusion is associated with age. Therefore, comparison of
prevalence of sacral–coccygeal fusion between studies is
appropriate only when the age profiles of the samples
are known. Of the 13 samples mentioned earlier for
which prevalence of sacral–coccygeal fusion has been
1
Black and white females without sacral–coccygeal fusion were
compared for the 15 pelvic and three nonpelvic variables. Results
show that these two groups differ significantly for four pelvic variables: transverse diameters of the inlet and outlet, sacral breadth,
and posterior sagittal diameter of the inlet, with whites larger than
blacks for these variables (Supporting Information Table S2).
431
SACRAL–COCCYGEAL FUSION IN HUMANS
TABLE 4. Number of individuals with, and prevalence of, fusion and without fusion of coccyx to sacrum by sex and age at death;
chi-square test used to compare females and males by decade of age at deatha
Sacral–coccygeal fusion
Females
Yes
No
Males
Total
No
Yes
Total
Age at
death
n
%
n
%
n
n
%
n
%
n
Prob.
20–29
30–39
40–49
50–59
60–69
70–79
80–89
90–99
1001
86
80
94
70
53
45
31
5
0
76.1
60.6
71.8
59.8
54.6
52.9
58.5
71.4
0.0
27
52
37
47
44
40
22
2
2
23.9
39.4
28.2
40.2
45.4
47.1
41.5
28.6
100.0
113
132
131
117
97
85
53
7
2
154
263
290
105
76
26
0
–
–
70.3
62.3
51.8
56.1
51.7
38.8
0.0
–
–
65
159
270
82
71
41
15
–
–
29.7
37.7
48.2
43.9
48.3
61.2
100.0
–
–
219
422
560
187
147
67
15
–
–
0.264
0.723
\0.001
0.528
0.653
0.083
\0.001
–
–
a
Level of significance set at P 0.007 is based on Bonferroni correction; significant results are underlined.
TABLE 5. Number of coccygeal vertebrae fused to sacrum by sex
Number of coccygeal
vertebrae fused
to sacrum
1
2
3
4
Total
Females
257
12
4
0
273
Males
658
34
10
1
703
TABLE 6. Frequency distribution of sacral-coccygeal
fusion with fusion between presacral vertebrae and
sacral-lumbar fusiona
Total
915
46
14
1
976
reported, three comparisons can be made with this
study. The first two comparisons are with samples from
Aberdeen (20th century) and London (18th–19th centuries; Saluja, 1988; his analysis was based on dry bones).
Results show no significant differences between the
prevalences of sacral–coccygeal fusion in the present
study with those for either Aberdeen or London (Supporting Information Table S3). The third comparison is
with a sample of females from London, ‘‘mainly from
20–30 years of age’’ and inferentially circa 1940 (Young
and Ince, 1940: 370; their analysis was based on radiographs of living individuals). Prevalence of sacral–
coccygeal fusion among these females was 2% (10 of
510 individuals), whereas the prevalence among females
in the present study between the ages of 20–29 years is
23.9% (Table 4). This difference in prevalence is significant (chi-square test, X2 5 79.659, df 5 1, P \ 0.001).
However, the prevalence of 2% should be regarded with
caution, because Young and Ince (1940: 371) acknowledged that they had ‘‘imperfect data obtained from the
enumeration of the sacral and coccygeal segments.’’ The
present study cannot resolve whether this difference in
prevalence of sacral–coccygeal fusion is due to a genetic
difference [e.g., populational difference in frequency of
vertebral shifting (Merbs, 1974)], an environmental difference (e.g., the Terry Collection consists partly of
‘‘those who . . . came from the lowest socioeconomic
strata’’ (Hunt and Albanese, 2005: 416), whereas the
sample of females from London represents an ‘‘unselected series of the apparently normal healthy population . . . [and are] healthy young married women’’
(Young and Ince, 1940: 370), or a methodological difference (e.g., analysis of dry bone versus radiographs).
One methodological difference between the present
Sacral–coccygeal fusion
Females
Fusion between presacral
vertebrae
No
Yes
Total
Sacral–lumbar fusion
No
Yes
Total
Males
No
Yes
Total
No
Yes
Total
406
55
461
228
44
272
634
99
733
822
70
892
596
91
687
1,418
161
1,579
440
24
464
263
10
273
703
34
737
879
35
914
695
8
703
1,574
43
1,617
a
Four females and 38 males could not be evaluated for fusion
between presacral vertebrae due to damage to bones.
study and other studies is that this study used only
individuals who had 24 presacral vertebrae (see above).
The prevalence of sacral–coccygeal fusion reported here
may have differed had individuals with a different
number of presacral vertebrae been included in the
analysis.
Results of this study are consistent with those of previous studies showing that prevalence of sacral–coccygeal fusion increases with advancing age (Duncan, 1937;
Saluja, 1988). Among males, prevalence of sacral–coccygeal fusion is comparable among individuals in their third
and fourth decades of life. Compared to these individuals, those in their fifth decade of life have a higher prevalence, and the prevalences among individuals in their
fifth, sixth, seventh, and eighth decades of life are comparable. There is another increase in prevalence among
individuals in their ninth decade of life. Among females,
chi-square analysis shows a significant relationship
between sacral–coccygeal fusion and age at death, but
partition analysis shows no significant increase in prevalence from the third through tenth decades of life. Saluja
(1988) reported similar results for a sample of Londoners
from the 18th–19th centuries—among males, those
between the ages of 20–39 had a lower prevalence of sacral–coccygeal fusion compared to those 40–89 years of
age, whereas among females there was no significant
association between sacral–coccygeal fusion and age. In
the present study, this researcher interprets the conflicting results in females between the chi-square analysis
American Journal of Physical Anthropology
432
R.G. TAGUE
TABLE 7. Summary statistics for females with and without sacral-coccygeal fusion for pelvic and nonpelvic variables;
results of Student’s t test and Mann-Whitney (MW) test comparing individuals with and without sacral-coccygeal fusion in
blacks and whites; probability (Prob.) based on Student’s t test unless otherwise indicated; all variables in mm, except sacral
angulation in degreesa
Blacks
Variable
Anteroposterior diameter
Inlet
Midplane
Outlet
Transverse diameter
Inlet
Midplane
Outlet
Sacrum
Breadth
Straight length
Angulation
Anterior sagittal diameter
Inlet
Midplane
Outlet
Posterior sagittal diameter
Inlet
Midplane
Outlet
Femoral length, maximum
Femoral head diameter
Clavicular length, maximum
Whites
No
sacral-coccygeal
fusion
Sacral-coccygeal
fusion
Mean
SD
n
Mean
SD
111.0
126.2
121.0
10.5 42
6.6 42
7.1 42
113.1
127.5
117.8
10.3 31
8.9 31
10.3 29
123.6
99.8
113.2
8.6 42
7.9 23
11.4 42
122.8
97.6
114.6
103.8
98.2
70.1
7.1 42
9.8 42
4.5 42
72.4
76.5
64.4
5.5 42
5.9 23
5.5 42
29.8
49.9
69.1
438.7
42.4
141.0
4.0
6.0
7.2
25.0
2.0
8.5
42
23
42
42
42
42
No
sacral-coccygeal
fusion
Sacral-coccygeal
fusion
Mean
SD
n
Mean
SD
0.417
0.471
0.132
116.8
128.8
120.7
11.6 30
8.3 30
8.3 30
120.7
126.2
113.8
10.1 29
7.8 29
7.9 29
7.7 31
7.4 14
11.3 31
0.680
0.766 (MW)
0.621
135.0
97.9
122.5
10.1 30
6.6
5
9.2 30
131.2
98.2
119.0
8.7 29
8.3
7
6.9 28
102.0
105.8
68.1
7.6 31
12.8 30
5.0 31
0.312
0.005
0.076
111.8
99.1
71.0
7.9 30
9.1 30
5.7 28
109.1
114.0
67.2
73.8
78.4
66.0
5.8 31
5.1 14
5.0 31
0.327
0.301 (MW)
0.216
75.9
76.6
68.3
7.2 30
4.4
5
6.3 30
77.7
78.0
68.5
31
0.524
12
0.627 (MW)
29 \0.001
31
0.800
31
0.347
31
0.229
33.7
49.8
63.6
427.8
43.2
138.7
30.5
50.8
61.4
440.3
43.0
138.6
6.0
9.5
9.4
27.3
3.0
8.4
n
Prob.
5.0
7.7
9.3
23.8
2.3
6.9
30
5
30
30
30
30
32.9
45.9
53.6
421.3
42.6
135.2
n
Prob.
0.176
0.231
0.002
0.132
0.871 (MW)
0.110
8.8 28
0.230
10.9 29 \0.001
5.4 28
0.011
7.4 29
3.8
7
6.3 28
3.9
5.2
12.3
27.7
2.4
8.6
28
7
28
29
29
29
0.368
0.372 (MW)
0.881
0.524
0.465 (MW)
0.001
0.336
0.313
0.091
a
Mann-Whitney test used if sample size \ 15 for either group in the comparison. Level of significance set at P 0.003 is based on
Bonferroni correction; significant results are underlined.
and partition analysis as follows. The prevalence of sacral–coccygeal fusion among females 20–29 years of age
(23.9%) is about half that of individuals 70–79 years of
age (47.1%). This difference in prevalence likely was
responsible for the significant chi-square result. However, the difference in prevalence between successive
decades is low enough that partition analysis shows
these differences to be nonsignificant. Collectively, this
researcher draws two generalizations from the results on
prevalence of sacral–coccygeal fusion with age: (1) prevalence is lowest for the youngest age group 20–29; 23.9%
in females and 29.7% in males, and (2) prevalence is
higher by age group 50–59 (significantly higher by age
group 40–49 in males), with no significant change in
prevalence in the age group 50–79—range in prevalence
in age group 50–79 is 40.2–47.1% in females and 43.9–
61.2% in males.
Previous reports suggest that females have a lower
prevalence of sacral–coccygeal fusion than males (MacCurdy, 1923; Saluja, 1988) and that fusion occurs later
in females than males (Duncan, 1937), because it is an
obstetrical hazard. However, the present study shows
that females and males do not differ from one another in
prevalence of sacral–coccygeal fusion for five of the seven
decades analyzed (20–29 through 80–89): 20–29, 30–39,
50–59, 60–69, and 70–79. Moreover, the sexes do not differ from one another in number of coccygeal vertebrae
fused to the sacrum, with 94% of instances of sacral–coccygeal fusion involving only one coccygeal vertebra.
Nevertheless, the comparability between the sexes in
their prevalence of sacral–coccygeal fusion and number
American Journal of Physical Anthropology
of coccygeal vertebrae fused to the sacrum belies an inference that they may differ in the etiology(-ies) for this
fusion. For example, this study shows that sacral–coccygeal fusion in males is associated positively with
fusion of presacral vertebrae and negatively with sacral–
lumbar fusion. In contrast, these relationships are nonsignificant in females. Therefore, this study does not
proffer an etiology for sacral–coccygeal fusion in females.
However, this study suggests two variables that influence sacral–coccygeal fusion in males. First, both fusion
between coccyx and sacrum (Table 4) and fusion between
presacral vertebrae are associated with advancing age
(Supporting Information Table S4; chi-square test, X2 5
158.485, df 5 6, P \ 0.001). This suggests that agerelated ankylosis explains, in part, sacral–coccygeal
fusion. Second, the negative association between sacral–
coccygeal fusion and sacral–lumbar fusion suggests that
incomplete cranial shifting inhibits sacral–coccygeal
fusion. With incomplete cranial shifting, the 24th vertebra, which is modally the fifth lumbar, is partly transformed and fuses with the first sacral vertebra but
remains identifiable as lumbar. The 29th vertebra, which
is modally the fifth sacral, is in turn partly transformed
into the first coccygeal vertebra (modally the 30th vertebra), but remains fused to the 28th vertebra. (This
researcher did not take observations on the anatomy of
the 29th vertebra among individuals with sacral–lumbar
fusion.) As this study shows that the first coccygeal vertebra fuses with the second in only 6% of the cases of
sacral–coccygeal fusion (61 of 976; Table 5), partial
transformation of the 29th vertebra may inhibit its
SACRAL–COCCYGEAL FUSION IN HUMANS
fusion with the 30th. Among males, this results in a low
prevalence of sacral–coccygeal fusion for those with sacral–lumbar fusion. This low prevalence is consistent
with Merbs’ (1974: 17) assertion that, ‘‘rare instances
have been reported . . . in which a single [vertebral] column appears to show both cranial and caudal shift’’
(with sacral–lumbar fusion being a cranial shift and sacral–coccygeal fusion being a caudal shift).
The comparison of pelvic and nonpelvic size between
females with and without sacral–coccygeal fusion shows
the following significant results: (1) in both blacks and
whites, individuals with sacral–coccygeal fusion have a
shorter posterior sagittal diameter of the outlet than
those without fusion, and (2) in whites only, individuals
with sacral–coccygeal fusion have a shorter anteroposterior diameter of the outlet and longer sacrum than those
without fusion. For whites, the explanation for the longer sacrum among those with sacral–coccygeal fusion is
intuitively obvious—their sacrum has six fused vertebrae
compared to five fused vertebrae for individuals without
sacral–coccygeal fusion. However, the difference in sacral
length between blacks with and without sacral–coccygeal
fusion only approaches significance. As sacral length in
this study is the straight length between the first and
last fused vertebrae, perhaps black females with sacral–
coccygeal fusion have greater curvature of the sacrum
compared to those without fusion. Among whites, the
shorter anteroposterior diameter of the outlet among
those with sacral–coccygeal fusion compared to those
without fusion is likely due to the coccyx being ‘‘directed
downwards and ventrally from the sacral apex’’
(Standring, 2005: 754). The more ventral position of the
coccyx compared to the fifth sacral vertebra shortens the
anteroposterior diameter. The reason for the nonsignificant difference in the anteroposterior diameter of the
outlet in blacks between those with and without coccygeal fusion is not evident, but could again be due to a difference between these groups in sacral curvature.
The principal result of the pelvimetric analysis is the
commonality in blacks and whites that females with sacral–coccygeal fusion have a shorter posterior sagittal diameter of the outlet compared to those without fusion.
The anatomical basis for the shorter posterior sagittal
diameter among females with sacral–coccygeal fusion is
simple. The apices of both the fifth sacral and first
coccygeal vertebrae are posterosuperior to the transverse
diameter of the outlet (Fig. 1E shows this position for
the fifth sacral vertebra). The fused coccyx, being positioned inferior and ventral to the fifth sacral vertebra
(see quotation above), is closer to the transverse diameter, and, thereby, the posterior sagittal diameter is shortened. Females with a short posterior sagittal diameter
may face an obstetrical hazard. Williams (1909: 626)
stated that, ‘‘in cases of transverse contraction [of the
pelvic outlet] . . . the possibility of spontaneous labor will
depend . . . upon the space available posterior to the
tubera ischii’’ (i.e., posterior sagittal diameter), and Moir
(1947: 22) asserted that, ‘‘a[n] . . . accurate indication [of
pelvic outlet contraction] . . . is the size of the posterior
sagittal diameter of the outlet.’’ Suonio et al. (1986)
regarded the posterior sagittal diameter of the outlet to
be contracted if it is more than 9% shorter than the
‘‘normal, ample’’ diameter. Using the mean value for
females without sacral–coccygeal fusion in the present
study as representing the ‘‘normal, ample’’ diameter,
55.5% (16 of 29) of black females and 57.1% (16 of 28)
of white females with sacral–coccygeal fusion have a
433
contracted posterior sagittal diameter of the outlet, that
is, their diameter is more than 9% shorter than the
mean of females without coccygeal fusion.2 In contrast,
among females without sacral–coccygeal fusion, 16.7% (7
of 42) of blacks and 26.7% (8 of 30) of whites have a posterior sagittal diameter of the outlet that is at least 9%
shorter than the mean.
The obstetrical significance of the posterior sagittal
diameter of the outlet is as follows. The fetus is
normally delivered through the subpubic arch, which is
in the anterior compartment of the outlet. However, if
the subpubic arch is narrow, the fetus is forced posteriorly until there is sufficient space for delivery. The
obstetrical disadvantage of a narrow subpubic arch can
be offset by a compensatory increase in the posterior
compartment of the outlet, that is, in the posterior sagittal diameter (Williams, 1909, 1911; Thoms, 1915;
Acosta-Sison and Calderon, 1919; Caldwell and Moloy,
1932). Cunningham et al. (2001: 56) stated that, ‘‘In
obstructed labors caused by a narrowing of the midpelvis or pelvic outlet, the prognosis for vaginal delivery
often depends on the length of the posterior sagittal
diameter of the pelvic outlet.’’ However, conjoint contraction of the subpubic arch and posterior sagittal
diameter (e.g., latter due to sacral–coccygeal fusion)
may result in an obstetrically inadequate outlet—‘‘If
the narrow [subpubic] arch is also associated with a
forward projecting sacral tip or fused coccyx (causing a
shortening of the lower antero-posterior, and posterior
sagittal outlet diameters) delivery may be arrested by
an outlet obstruction’’ (Moir, 1947: 23). The obstetrical
hazard of dual contraction of subpubic arch and posterior sagittal diameter may necessitate operative intervention to ensure successful delivery, such as use of
forceps, cesarean section, and operative fracture of the
fused coccyx (Graff, 1924; Jarcho, 1933; Morris, 1947;
Ernst, 1950; Fliegner, 1987; Peyton, 1988).
Although the reproductive histories of the females in
this study are not known, 31% of those of reproductive
age have sacral–coccygeal fusion (116 of 376 in age
group 20–49; Table 4), and more than 50% of those with
sacral–coccygeal fusion have a contracted posterior sagittal diameter of the outlet (see above). The implication is
that there must be an etiology to minimize the conjoint
occurrence of contracted posterior sagittal diameter of
outlet and subpubic arch lest a number of females have
obstetrically inadequate outlets. The explanation is that
the posterior sagittal diameter of the outlet and subpubic
arch are part of different anatomical complexes. The posterior sagittal diameter is determined, in part, by displacement of the lower part of the sacrum and coccyx
from the ischia by sacral angulation, and the subpubic
arch are determined by lateral flare of the ischia and
ischiopubic rami (Caldwell and Moloy, 1932; Caldwell
et al., 1934; Thoms et al., 1939; Tague, 1992, 2000). This
2
That females with sacral–coccygeal fusion have a short, and
inferentially obstetrically disadvantageous, posterior sagittal diameter of the outlet is also seen in that they are male-like in the length
of this diameter. Student’s t test analysis shows a nonsignificant difference in length of the posterior sagittal diameter of the outlet
between the combined sample of black and white females with sacral–coccygeal fusion in this study and a sample of black and white
males without sacral–coccygeal fusion (Tague, 2009: 435, Table 7);
these males were also sampled from the Hamann-Todd, and Terry
Collections and had 24 presacral vertebrae: summary statistics—
females, 57.6 ± 11.5 mm, n 5 57; males, 58.4 ± 7.8 mm, n 5 75; P 5
0.671.
American Journal of Physical Anthropology
434
R.G. TAGUE
anatomical independence between the posterior sagittal
diameter and subpubic arch lowers the probability of
their conjoint contraction.3
Sacral angulation is one of the principal sexual dimorphisms of the pelvis, with females having a higher sacral
angulation than males (Tague, 1992). As mentioned earlier, sacral angulation is a determinant of the length of
the posterior sagittal diameter of the outlet (sacral
length and length from ischial tuberosity to apex of auricular surface also influence the length of this diameter;
see Fig. 1A,B, Appendix Table 1). As a short posterior
sagittal diameter of the outlet can be obstetrically hazardous, and as sacral–coccygeal fusion contributes to
shortening of this diameter, the inference is that sacral–
coccygeal fusion in females may be a principal contributor to evolution of sexual dimorphism in sacral angulation.
This researcher is not aware of any case report documenting that sacral–coccygeal fusion was a proximate
cause of maternal or neonatal mortality. Therefore, the
natural selective disadvantage of sacral–coccygeal fusion
is inferential. Nevertheless, the results of this study in
conjunction with the obstetrical literature reporting that
sacral–coccygeal fusion can be a hazard during delivery
provide a compelling argument that this fusion can influence a woman’s lifetime reproductive success. The
obstetrical peril of sacral–coccygeal fusion is not absolute, but depends on the orientation of the fused coccyx,
capacity of the subpubic arch, size of the fetus, and
strength of uterine contractions.
Finally, the evolutionary origin in humans of sacral–
coccygeal fusion is not known. Based on the published
descriptions of fossils and this researcher’s examination
of two casts, two of eight earlier hominid sacra show sacral–coccygeal fusion: SH Pelvis 1 (Homo heidelbergensis)
3
Anatomical independence between posterior sagittal diameter of
outlet and subpubic angle is demonstrated by the nonsignificant correlation between these variables. Using the combined sample of
black and white females for the two groups in this study—those
with and without sacral–coccygeal fusion—Pearson’s correlation
coefficients are as follows: females with sacral–coccygeal fusion, r 5
0.042, P 5 0.757, n 5 57; and females without fusion, r 5 0.097, P
5 0.418, n 5 72. All correlations are also nonsignificant for the subsets of each group (i.e., blacks with sacral–coccygeal fusion, whites
with fusion, blacks without fusion, and whites without fusion). Subpubic angle is calculated using the triangle solution, with sides 1
and 2 of the triangle being the left and right anterior oblique diameters of the outlet, and side 3 being the transverse diameter of the
outlet [Fig. 1A,D, Appendix Table 1 and its Eq. (1)].
American Journal of Physical Anthropology
and La Ferrassie 1 (Neandertal). The SH Pelvis 1 sacrum
has six elements, with the sixth element ‘‘conspicuously
coccygeal in form . . . and (the) sixth element’s body shows
incomplete fusion, both in the ventral and dorsal surfaces, to the fifth sacral vertebral body’’ (Bonmatı́ et al.,
2010: 3, Supporting Information). ‘‘La Ferrassie 1 Cx1
[i.e., first coccygeal vertebra] exhibits an ossification of
the right lateral sacrococcygeal ligament that undoubtedly fused it to the S5’’ [i.e., fifth sacral vertebra] (Trinkaus, 1983: 205). The six fossils not showing sacral–coccygeal fusion are as follows: A.L. 288-1an (Australopithecus afarensis), DNH 43A (Paranthropus robustus),
Kebara 2 (Neandertal), Shanidar 3 (Neandertal), Shanidar 4 (Neandertal), and SH AT-1005 (Homo heidelbergensis) (Johanson et al., 1982; Trinkaus, 1983; Rak, 1991;
Gommery et al., 2002; Bonmatı́ et al., 2010). Based on
comparative study of 41 genera of extant primates,
Schultz and Straus (1945) reported that the number of
sacral vertebrae is more variable in genera without tails
than in those with tails, and this greater variability is
due, in part, to sacral–coccygeal fusion. A future line of
inquiry would be to test the hypothesis that sacral–coccygeal fusion is more prevalent in species without a tail
(e.g., humans) than in those with a tail.
ACKNOWLEDGMENTS
I thank Yohannes Haile-Selassie, Bruce Latimer, and
Lyman Jellema of the Cleveland Museum of Natural
History, and David Hunt of the National Museum of
Natural History, Smithsonian Institution for permitting
me to study skeletal material in their care. I also thank
Mary Lee Eggart of the Department of Geography and
Anthropology, Louisiana State University for drawing
Figure 1.
Computed, Eq. (2)
Computed, Eq. (2)
Computed, Eq. (3)
Computed, Eq. (4)
Computed, Eq. (4)
Anterior sagittal diameter of midplane
Anterior sagittal diameter of outlet
Posterior sagittal diameter of inlet
Posterior sagittal diameter of midplane
Posterior sagittal diameter of outlet
Measured
Measured
Measured
Measured
Chord of linea terminalis
Ischial tuberosity to apex of auricular surface
Ischial tuberosity to posterior inferior iliac spine
Apex of auricular surface to posterior
inferior iliac spine
Fig. 1C: b–h
Fig. 1B: g–h
Fig. 1B: g–i
Fig. 1B: h–i
Fig. 1A: d–f
Fig. 1A: d–g
Fig. 1A: c–f
Fig. 1A: e–g
Superomedial border of pubic symphysis to point on linea terminalis
representing transverse diameter of inlet
Inferomedial border of pubic symphysis to ischial spine
Inferomedial border of pubic symphysis to ischial tuberosity
Transverse ridge between fourth and fifth sacral vertebrae to ischial spine
Apex of fifth sacral vertebra for individuals without sacral–coccygeal
fusion or of first coccygeal vertebra for those with sacral–coccygeal
fusion to ischial tuberosity
Superomedial border of pubic symphysis to apex of auricular surface
Ischial tuberosity to apex of auricular surface
Ischial tuberosity to posterior inferior iliac spine
Apex of auricular surface to posterior inferior iliac spine
Promontory of first sacral vertebra to superomedial border of pubic symphysis
Transverse ridge between fourth and fifth sacral vertebrae to inferomedial
border of pubic symphysis
Apex of fifth sacral vertebra for individuals without sacral–coccygeal fusion
or of first coccygeal vertebra for those with sacral–coccygeal fusion to
inferomedial border of pubic symphysis
Maximum diameter between linea terminales, visually oriented to be
perpendicular to the anteroposterior diameter of inlet
Minimum diameter between ischial spines
Diameter between ischial tuberosities
Transverse diameter of sacrum at plane of pelvic inlet
Straight length from promontory of first sacral vertebra to apex of fifth
sacral vertebra for individuals without sacral–coccygeal fusion or of first
coccygeal vertebra for those with sacral–coccygeal fusion
Angle between sides 1 and 2 of the following triangle: side 1—ischial
tuberosity to apex of auricular surface; side 2—apex of auricular surface
to posterior inferior iliac spine; side 3—ischial tuberosity to posterior
inferior iliac spine
Superomedial border of pubic symphysis to midpoint of transverse
diameter of inlet
Inferomedial border of pubic symphysis to midpoint of transverse
diameter of midplane
Inferomedial border of pubic symphysis to midpoint of transverse
diameter of outlet
Midpoint of sacral breadth to midpoint of transverse diameter of inlet
Transverse ridge between fourth and fifth sacral vertebrae to midpoint
of transverse diameter of midplane
Apex of fifth sacral vertebra for individuals without sacral–coccygeal
fusion or of first coccygeal vertebra for those with sacral–coccygeal
fusion to midpoint of transverse diameter of outlet
Maximum straight length of femur
Maximum diameter of femoral head
Maximum straight length of clavicle
Description of variables
Equations used to compute variables: Eq. (1), angulation of sacrum (Fig. 1B, h; see above for descriptions of sides 1, 2, and 3 of triangle) 5 arccos [(side 1)2 1 (side 2)2 2 (side 3)2]/[2(side
1)(side 2)]; Eq. (2), anterior sagittal diameter of inlet (Fig. 1C: b–k), midplane (Fig. 1E: d–m), outlet (Fig. 1E: d–n) 5 [(anterior oblique diameter)2 2 (0.5(transverse diameter))2]0.5, with appropriate diameters of each plane used; Eq. (3), posterior sagittal diameter of inlet (Fig. 1C: k–l) 5 [((chord of linea terminalis)2 2 (0.5(sacral breadth))2)0.5] 2 anterior sagittal diameter of inlet;
and Eq. (4), posterior sagittal diameter of midplane (Fig. 1E: c–m) and outlet (Fig. 1E: e–n) 5 [(posterior oblique diameter)2 2 (0.5(transverse diameter))2]0.5, with appropriate diameters of
each plane used.
a
Osteological points are described in Figure 1.
Measured
Measured
Measured
Measured
Anterior oblique diameter of midplane
Anterior oblique diameter of outlet
Posterior oblique diameter of midplane
Posterior oblique diameter of outlet
Not illustrated
Not illustrated
Not illustrated
in study
Fig. 1C: b–j
Fig. 1E: e–n
Fig. 1C: k–l
Fig. 1E: c–m
Fig. 1E: d–n
Fig. 1E: d–m
Fig. 1C: b–k
Fig. 1B, h: side 1, g–h;
side 2, h–i; side 3, g–i
Fig. 1D: f–f
Fig. 1D: g–g
Fig. 1C: h–h
Fig. 1A: a–e
Fig. 1C: j–j
Fig. 1A: d–e
Fig. 1A: a–b
Fig. 1A: c–d
Figure illustration
and osteological points
Femoral length
Measured
Femoral head diameter
Measured
Clavicular length
Measured
Variables not reported in study but used to compute other variables that are reported
Anterior oblique diameter of inlet
Measured
Computed, Eq. (2)
Measured
Measured
Measured
Measured
Transverse diameter of midplane
Transverse diameter of outlet
Sacral breadth
Sacral length
Anterior sagittal diameter of inlet
Measured
Transverse diameter of inlet
Computed, Eq. (1)
Measured
Anteroposterior diameter of outlet
Sacral angulation
Measured
Measured
Variables measured
or computed
Variables reported in study
Anteroposterior diameter of inlet
Anteroposterior diameter of midplane
Variables
TABLE APPENDIX 1. Description of pelvic and nonpelvic variablesa
436
R.G. TAGUE
LITERATURE CITED
Abitbol MM. 1987. Evolution of the sacrum in hominoids. Am J
Phys Anthropol 74:65–81.
Acosta-Sison H, Calderon F. 1919. Pelvimetry and cephalometry
among Filipino women and newborn babies. Philippine J Sci
14:253–271.
Anon. 1946. Fracture of coccyx and dystocia. J Am Med Assoc
132:420.
Bø K, Lilleås F, Talseth T, Hedland H. 2001. Dynamic MRI of
the pelvic floor muscles in an upright sitting position. Neurourol Urodyn 20:167–174.
Bonmatı́ A, Gómez-Olivencia A, Arsuaga JL, Carretero JM, Gracia
A, Martinez I, Lorenzo C, Bérmudez de Castro JM, Carbonell E.
2010. Middle Pleistocene lower back and pelvis from an aged
human individual from the Sima de los Huesos site, Spain. Proc
Natl Acad Sci USA 107:18386–18391.
Breathnach AS, editor. 1965. Frazer’s anatomy of the human
skeleton, 6th ed. Boston: Little, Brown and Co.
Brunskill PJ, Swan JW. 1987. Spontaneous fracture of the coccygeal body during the second stage of labour. J Obstet
Gynaecol 7:270–271.
Caldwell WE, Moloy HC. 1932. Sexual variations in the pelvis.
Science 76:37–40.
Caldwell WE, Moloy HC, D’Esopo DA. 1934. Further studies on
the pelvic architecture. Am J Obstet Gynecol 28:482–497.
Cooper WL. 1960. Coccygodynia: an analysis of one hundred
cases. J Int Coll Surg 33:306–311.
Cunningham FG, Gant NF, Leveno KJ, Gilstrap LC III, Hauth
JC, Wenstrom KD. 2001. Williams obstetrics, 21st ed. New
York: McGraw-Hill.
Derry DE. 1912. The influence of sex on the position and composition of the human sacrum. J Anat Physiol 46:184–192.
Dieulafé R. 1933. Le coccyx: étude ostéologique. Arch Anat Histol Embryol 16:41–91.
Duncan GA. 1937. Painful coccyx. Arch Surg 34:1088–1104.
Ernst S. 1950. Das Steißbeins als Geburtshindernis. Zentralbl
Gynakol 72:1363–1368.
Feldesman MR, Fountain RL. 1996. ‘‘Race’’ specificity and the
femur/stature ratio. Am J Phys Anthropol 100:207–224.
Feldesman MR, Kleckner JG, Lundy JK. 1990. Femur/stature
ratio and estimates of stature in mid- and late-Pleistocene fossil hominids. Am J Phys Anthropol 83:359–372.
Fliegner JRH. 1987. Pelvic outlet contraction: a forgotten entity.
Asia Oceania J Obstet Gynaecol 13:401–403.
Fuller K. 1998. Adult females and pubic bone growth. Am J
Phys Anthropol 106:323–328.
Gommery D, Sénut B, Keyser A. 2002. Description d’un bassin
fragmentaire de Paranthropus robustus du site Plio-Pléistocène de Drimolen (Afrique du Sud). Geobios 35:265–281.
Graff E. 1924. Steißbeinresektion unter der Geburt. Wien Klin
Wochenschr 37:1260–1261.
Grassi R, Lombardi G, Reginelli A, Capasso F, Romano F, Floriani
I, Colacurci N. 2007. Coccygeal movement: assessment with
dynamic MRI. Eur J Radiol 61:473–479.
Guerriero WF, Arnell RE, Irwin JB. 1940. Pelvicephalography:
an analysis of 503 selected cases. South Med J 33:840–844.
Hunt DR, Albanese J. 2005. History and demographic composition of the Robert J. Terry anatomical collection. Am J Phys
Anthropol 127:406–417.
Jarcho J. 1933. The pelvis in obstetrics: a practical manual of
pelvimetry and cephalometry including chapters on roentgenological measurement. New York: Paul B Hoeber.
Johanson DC, Lovejoy CO, Kimbel WH, White TD, Ward SC,
Bush ME, Latimer BM, Coppens Y. 1982. Morphology of the
Pliocene partial hominid skeleton (A.L. 288-1) from the Hadar
Formation, Ethiopia. Am J Phys Anthropol 57:403–451.
Jones ME, Shoaib J, Bircher MD. 1997. A case of coccygodynia
due to coccygeal fracture secondary to parturition. Injury
28:549–550.
Kern KF. 2006. T. Wingate Todd: pioneer of modern American
physical anthropology. Kirtlandia 55:1–42.
Kirchhoff H, Kräubig H. 1957. The obstetric importance of the
‘‘long pelvis.’’ J Int Coll Surg 27:607–612.
American Journal of Physical Anthropology
_ can MY. 1986. The human skeleton
Krogman WM, Is
in forensic medicine, 2nd ed. Springfield, IL: Charles C
Thomas.
Last RJ. 1978. Anatomy: regional and applied, 6th ed. Edinburgh: Churchill Livingstone.
MacCurdy GG. 1923. Human skeletal remains from the highlands of Peru. Am J Phys Anthropol 6:217–329.
McFalls JA Jr. 2007. Population: a lively introduction, 5th ed.
Popul Bull 62:1–31.
Merbs CF. 1974. The effects of cranial and caudal shift in the
vertebral columns of northern populations. Arctic Anthropol
11:12–19.
Moir JC. 1947. The use of radiology in predicting difficult
labour. J Obstet Gynaecol Br Emp 54:20–33.
Morris WIC. 1947. Outlet contraction of the pelvis. Edinb Med J
54:89–110.
PASW Statistics 18. 2010. Chicago: SPSS.
Paterson AM. 1893. The human sacrum. Sci Trans R Dublin Soc
5:123–204.
Peyton FW. 1988. Coccygodynia in women. Indiana Med
81:697–698.
Postacchini F, Massobrio M. 1983. Idiopathic coccygodynia.
Analysis of fifty-one operative cases and a radiographic
study of the normal coccyx. J Bone Joint Surg Am 65:1116–
1124.
Rak Y. 1991. The pelvis. In: Bar-Yosef O, Vandermeersch B,
editors. Le squelette Moustérien de Kébara 2. Paris: Éditions
CNRS. p 147–156.
Ruff CB, Scott WW, Liu AY-C. 1991. Articular and diaphyseal
remodeling of the proximal femur with changes in body mass
in adults. Am J Phys Anthropol 86:397–413.
Saluja PG. 1988. The incidence of ossification of the sacrococcygeal joint. J Anat 156:11–15.
Scheuer L, Black S. 2000. Developmental juvenile osteology.
San Diego: Elsevier.
Schultz AH, Straus WL Jr. 1945. The numbers of vertebrae in
primates. Proc Am Philos Soc 89:601–626.
Scott JH. 1893. Contribution to the osteology of the aborigines
of New Zealand and of the Chatham Islands. Trans NZ Inst
26:1–64.
Shore LR. 1930. Abnormalities of the vertebral column in a series of skeletons of Bantu natives of South Africa. J Anat
64:206–238.
Siegel S, Castellan NJ Jr. 1988. Nonparametric statistics for the
behavioral sciences, 2nd ed. New York: McGraw-Hill.
Slome D. 1929. The osteology of a Bushman tribe. Ann S Afr
Mus 24:33–60.
Spinney L. 2008. The old curiosity shop. New Sci 198:42–45.
Staderini R. 1894. Ricerche statistiche sulla frequenza delle
varietà numeriche delle vertebre nell’uomo e considerazioni
sulla loro genesi. Monit Zool Ital 5:56–68,95–108.
Standring S, editor. 2005. Gray’s anatomy: the anatomical basis
of clinical practice, 39th ed. Edinburgh: Elsevier.
Suonio S, Saarikoski S, Räty E, Vohlonen I. 1986. Clinical
assessment of the pelvic cavity and outlet. Arch Gynecol
239:11–16.
Tague RG. 1992. Sexual dimorphism in the human bony pelvis,
with a consideration of the Neandertal pelvis from Kebara
cave, Israel. Am J Phys Anthropol 88:1–21.
Tague RG. 1994. Maternal mortality or prolonged growth: age
at death and pelvic size in three prehistoric Amerindian populations. Am J Phys Anthropol 95:27–40.
Tague RG. 2000. Do big females have big pelves? Am J Phys
Anthropol 112:377–393.
Tague RG. 2009. High assimilation of the sacrum in a sample
of American skeletons: prevalence, pelvic size, and obstetrical and evolutionary implications. Am J Phys Anthropol
138:429–438.
Tague RG, Lovejoy CO. 1998. AL 288-1—Lucy or Lucifer: gender confusion in the Pliocene. J Hum Evol 35:75–94.
Thoms H, Foote WR, Friedman I. 1939. The clinical significance
of pelvic variations: a dimensional study of the upper, mid,
and lower pelvis in 200 white primiparous women. Am J
Obstet Gynecol 38:634–642.
SACRAL–COCCYGEAL FUSION IN HUMANS
Thoms HK. 1915. A statistical study of the frequency of funnel
pelves and the description of a new outlet pelvimeter. Am J
Obstet Dis Women Child 72:121–132.
Trinkaus E. 1983. The Shanidar Neandertals. New York: Academic Press.
Walrath DE, Glantz MM. 1996. Sexual dimorphism in the pelvic
midplane and its relationship to Neandertal reproductive patterns. Am J Phys Anthropol 100:89–100.
Wilkinson WR. 1947. Coccygodynia: review of the literature and
presentation of cases. South Surg 13:280–293.
Williams JW. 1909. Frequency, etiology and practical significance of contractions of the pelvic outlet. Surg Gynecol Obstet
8:619–638.
437
Williams JW. 1911. The funnel pelvis. Am J Obstet Dis Women
Child 64:106–124.
Williams JW. 1918. A consideration of some of the anatomical
factors concerned in the production of deformed pelves. Am J
Obstet Dis Women Child 77:714–758.
Willis TA. 1923. The lumbo-sacral vertebral column in man, its
stability of form and function. Am J Anat 32:95–123.
Wray CC, Easom S, Hoskinson J. 1991. Coccydynia: aetiology
and treatment. J Bone Joint Surg Br 73:335–338.
Young M, Ince JGH. 1940. Transmutation of vertebrae in
the lumbo-sacral region of the human spine. J Anat
74:369–373.
American Journal of Physical Anthropology
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