Hello everyone.  Here are the references, and some quoted sections, on the
topic of fusion of the cranial bones, and the sacroiliac joint.

Primary reference:

Steele, D. Gentry, and Claude Bramblett  1988  The Anatomy and Biology of
the Human Skeleton.  College Station, TX: Texas A&M University Press.

p. 56 on aging the human skeleton:
"Once maturity is reached, growth ceases and the main developmental changes
seen in the skeleton are sign of suture obliteration, bone and joint
deterioration, and tooth wear."

p. 56-57, on the different stages of life, beginning with infancy:
"Generally, the bones of the infant are small, fragile, and composed of
porous cortical bone.  Many of the bones of the skull that have more than
one center of primary ossification have not yet fused.  Specifically, the
mandible is usually in two separate pieces, the hemimandibles, which fuse at
the mental symphysis at the end of the first year of life.  The sphenoid is
usually in three separate pieces at birth, the elements fusing near the end
of the first year.  The frontal is in two segments that begin to fuse during
the second year, although the metopic suture or its remnant may persist
beyond the childhood years.  The occipital bone is in four pieces at birth.
This condition continues throughout infancy into childhood.  The maxilla and
premaxilla fuse during infancy, although the suture separating them may
persist into childhood....[early childhood, 3-5 years]...The occipital
provides the best indication of age at this time since it has begun to fuse
into one mass by the sixth year....[late childhood, 6-12 years]...The skull,
and particularly the face, continues to increase in size, but separate bones
of the face and skull have not begun to fuse together.  In archeological
material, skulls of individuals in this age category still commonly separate
at the sutural junction between the bones...[adolescence, 13-24
years]l...This is the time of final maturation and completion of skeletal
growth.  Some sutures separating various bones of the face and calvaria
[brain case] may begin to fuse, but the timing of the onset of this is quite
variable, and it is unusual for noticeable progress to occur [during
adolescence].  Perhaps the only suture regular enough in its timing of
fusion to be useful at this age is the basilar suture separating the
sphenoid and occipital bones.  It begins to fuse as early as 16 years, is
actively fusing between 17 and 18, and is completely united before the age
of 21 years in males (McKern and Stewart 1957, McKern 1970)...[young
adulthood, 25-49 years]...Sutures of the face and calvaria are beginning to
fuse, but their progress is variable.  It would be unusual, however, for
mnay of the sutures to be obliterated during young adulthood.  One of the
earlier studies to document carefully the rate and pattern of fusion of the
cranial sutures on the external surface of the skull was that of McKern and
Stewart (1957).  Table 3.3 presents their findings on the rate and
variability in the fusion of the sagittal, lambdoidal, and coronal
sutures....[old adulthood, 50+ years]...Another feature commonly associated
with old age is the obliteration of many of the sutures of the face and
skull (Meindl and Lovejoy 1985).  In extreme cases the calvaria can appear
to have been formed from one bone...Meindl and Lovejoy (1985) reevaluated
the utility of ectocranial suture closure [observed from the outside of the
skull] as an indicator of age in an attempt to establish more precise
criteria.  They considered the lateroanterior region of the brain case to be
the most consistent in the pattern of suture fusion.  Five areas in the
region were chosen for examination: the pterion, the midcoronal, the
sphenofrontal, the inferior sphenotemporal, and the superior shenotemporal
regions.  For each of these regions the state of fusion was coded in a scale
of four degrees of closure: 0 = open, 1 = minimal closure (represented by a
single bony bridge across the suture to as much as 50 percent synostosis
[complete fusion]), 2 = significant closure (greater than 50% fusion but
still not complete), and 3 = complete fusion."

p. 204 on the pelvic bones:
"[infancy, 0-2 years]...the primary centers of ossification, which begin to
develop during the third month of intrauterine life, are present but not
fused...[early childhood, 3-5 years]...The primary centers continue to
increase in size but are still present as separate elements...[late
childhood, 6-12 years]...during the first half of this period the ischium
and pubis fuse at their adjoining rami, but the three elements are still
separate in the acetabulum...[adolescence, 13-24 years]...The os acetabulum
begins to ossify with the onset of puberty, and by 18 or 19 years the coxa
is a single element."

p. 129 on the sacrum fusing to the iliac across the sacro-iliac juncture:
"The sacroiliac may fuse in some individuals."



Another reference is:

Iscan, M.Y., and S.R. Loth  1989  Osteological manifestations of age in the
adult."  In M.Y. Iscan and K.A.R. Kennedy, editors, Reconstruction of Life
from the Skeleton.  New York: Alan R. Liss, Inc.

p. 24 on direct morphological examination of the skull to assess age:
"Historically, the skull was the first part of the skeleton systematically
investigated for the estimation of age at death.  By the end of the
nineteenth century, studies of cranial suture closure had been conducted
by.....(many citations).  These early researchers found a positive
correlation with age commencing with basilar suture (synchondrosis) closure
at 18-21 years followed by observations of the vault beginning endocranially
anywhere between 25 and 40 years of age and continuing through the sixties.
The general progression of sutural closure is depicted in Figure 1.
However, the extreme variability in the order and timing of closure was
noted.  At the turn of the century, Frederic introduced a five-point rating
scale (0-4) for both vault and facial sutures......[he goes on to discuss
the history of the different techniques for rating degrees of closure, and
the sites chosen for age estimation.]"


Apparently, the consensus today is that there is so much individual
variability that it is very difficult to pin a precise age on a specific
individual, and that even decade divisions may not be wide enough, but that
divisions into "young adult," "old adult" and "really old adult" are
probably still valid.  But no one is "debating" whether or not the cranial
sutures close, as they obviously do.

More references:

Masset, Claude  1989  "Age Estimation on the Basis of Cranial Sutures," in
M.Y.Iscan, editor, Age Markers in the Human Skeleton.  Springfield, IL:
Charles C. Thomas, Publisher.

This chapter begins:
"Of all age indicators, cranial sutures have been the most widely used
because they are easy to examine and skulls from archaeological excavations
are often dealth with separately from other bones....The literature dealing
with cranial sutures greatly exceeds that for all other age indicators."

Meindl, R.S., and C.O. Lovejoy, 1985  Ectocranial suture closure: A revised
method for the determination of skeletal age at death based on the
lateral-anterior sutures.  American Journal of Physical Anthropology 68:57-66.

Zivanovic, S.  1983  A note on the effect of asymmetry in suture closure in
mature human skulls.  American Journal of Physical Anthropology 60:431-435.

Becker, M.J.  1986  Mandibular symphysis (medial suture) closure in modern
Homo sapiens: Preliminary evidence from archaeological populations.
American Journal of Physical Anthropology 69:499-501.


Once again, I repeat what I said earlier, I am not disputing that whatever
manipulations are done to the skull and spine as part of cranial-sacral
therapy are not helpful, but *that* they work can be independent of our
understanding of *how* they work.  The cranial bones do indeed fuse, some in
childhood and others not til later adulthood, but they do fuse.  I can walk
out of my office and look at the examples the graduate students pulled for
me of prehistoric Native American skulls with fused cranial sutures.

I would urge people to be extremely wary of anyone claiming to be able to
manipulate cranial bones in older adults, because once they have fused, they
can only be moved if broken.  I, for one, particularly would not let anyone
manipulate my child's cranial bones who thought that:
(1) cranial bones never fuse, and/or
(2) cerebrospinal fluid circulates through the bones of the skull, across
suture lines

because neither of these statements is true.

The graduate students in my lab, who use cranial suture closure as one
indicator of approximate age in skeletons, would really like to see the
statement made by the American Medical Association that "cranial bones never
fuse".  I would appreciate having that reference to pass on to them.

----------------------------------------------------------------------------
-------
Katherine A. Dettwyler, Ph.D.                         email: [log in to unmask]
Anthropology Department                               phone: (409) 845-5256
Texas A&M University                                    fax: (409) 845-4070
College Station, TX  77843-4352