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Atlanto-occipital fusion and spondylolisthesis in an Anasazi skeleton from bright angel ruin Grand Canyon National Park Arizona.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 67:381-391(1985)
Atlanto-Occipital Fusion and Spondylolisthesis in an Anasazi
Skeleton From Bright Angel Ruin, Grand Canyon National Park,
Arizona
CHARLES F. MERBS AND ROBERT C. EULER
Department ofAnthropbgy, Arizona State Uniuersity, Tempe, Arizona
85287
KEY WORDS Paleopathology, Atlanto-occipital fusion,
Spondylolisthesis, Depression fracture, American Southwest
The skeleton of a middle-aged female showing a n unusual
ABSTRACT
pattern of congenital, traumatic, and degenerative pathology was recovered
from a small Kayenta Anasazi site located near the confluence of Bright Angel
Creek with the Colorado River in the Inner Gorge of Grand Canyon. The atlas
is fused with the base of the skull and C2 is fused with C3. The cervical region
was subjected to hyperextension, perhaps through use of a tumpline, with
resultant reduction of the neural canal to 8 mm, a condition that quite likely
led to neurological problems. The skeleton also includes a depression fracture
of the lateral condyle of the left tibia. Complete, bilateral spondylolysis of L5
led to a n olisthesis of approximately 15 mm. The disc between L5 and S1 then
ossified, most likely from staphylococcus bacteremia, making the olisthesis
permanent and thereby creating a unique archaeological specimen. Although
spondylolysis is usually viewed as a stress fracture, the general pattern of
pathology in this individual makes it necessary to consider a n etiology of acute
trauma.
ARCHAEOLOGICAL CONTEXT
Near the confluence of Bright Angel Creek
and the Colorado River in the Inner Gorge of
Grand Canyon is a small Kayenta Anasazi
ruin (Ariz. B:16:1) that was occupied ca. A.D.
1050-1150. The site was first noted in 1869
by Major John Wesley Powell (1875: 87) during his initial voyage down the Colorado
River, but it was not recorded by professional
archaeologists until 1953 (Taylor, 1958: 25).
In 1969, the National Park Service contracted with the School of American &search to excavate the site (Schwartz et al.,
1979), but no human skeletal material was
recovered. However, in January of 1982, during the course of digging by a construction
crew, two burials (Ariz. B:16:1A) associated
with the pueblo were accidently discovered.
Work was immediately halted, fortunately,
before major damage occurred, and excavation was undertaken by Robert C. Euler, assisted by A. Trinkle Jones and Lisa D. Madsen.
The bodies had been interred in the only
boulder-f:ee sandy area of the entire delta,
on the west side of Bright Angel Creek, ap0 1985 ALAN R. LISS, INC.
proximately 300 m west of the pueblo, 50 m
west of the present course of the creek, and
90 m north of the Colorado River. Burial 1
contained the skeleton of a n adult woman a t
a depth of approximately 1m below present
ground surface in unconsolidated sand. The
original ground surface was not ascertainable. The skeleton was lying on its back in a
loosely flexed position with its skull to the
south on fairly compact white flecked sand.
Near the right iIium was a Tusayan Corrugated jar, the only cultural item in association with the burial. Burial 2, located a t the
same subsurface level and approximately 80
cm west of burial 1,contained the somewhat
disarticulated, partial skeleton of a juvenile.
Although the skull was lacking, the body
had probably been oriented with its head to
the northwest. The only artifact in association was a bracelet on the left wrist consisting of one olivella shell and eleven fine-
Received September 25, 1984; revised March 12, 1985; accepted March 25,1985.
382
C.F. MERBS AND R.C. EULER
grained siltstone beads. This skeleton is too
fragmentary to warrant, further discussion in
this paper.
DESCRIFTION OF ADULT SKELETON
The skeleton of the adult (burial 1)is relatively complete except for the face and mandible. The only facial parts present are the
left zygomatic, a portion of the left maxilla,
and a portion of the right zygomatic. The
occipital shows postmortem damage near the
left mastoid process, but the cranium is otherwise well-preserved. All major postcranial
parts are present, but many show postmortem damage, and in a few cases the damage
is extensive. The only parts actually missing,
however, are very small bones such as carpals and phalanges.
The skull has large mastoid processes and
moderately well developed supraorbital ridges, and it could easily be judged as male.
Evidence from the postcranial skeleton, however, strongly indicates female. The greater
sciatic notch of the pelvis (preserved on both
sides) is broad and shallow, and the pubic
element (preserved on left side) is elongated.
A well-defined preauricular sulcus is present, and the acetabulum is small relative to
the overall size of the pelvis. The lengths of
the long bones and their overall gracility also
strongly suggest the sex of the skeleton to be
female. Considering the reliability of the various criteria and their intensity of expression
in this skeleton, a judgement of female can
be made with high reliability. The application of standard aging criteria to this skeleton suggests an approximate age of 37 years
at time of death with individual criteria producing ages as young as 30 years and as old
as 48 years.
Estimates of stature for the skeleton are
based upon the maximum length of the right
femur taken by itself, and upon the maximum lengths of all long bones (except the
tibia) from the left side considered as a group.
Using the method of Genoves (1967), which
is based upon modern Mexicans of predominantly Indian origin, this individual is estimated to have been slightly less than 156 cm
(5 feet 1inch) in height.
The cranium is flattened a t lambda (actually centered 20 mm to the left of lambda)
and markedly asymmetrical. Although the
lambdoidal suture is complicated and contains tiny “inclusions,” no actual wormian
bones are present. The cranium contains unusually large, irregularly shaped tympanic
dehiscences (Fig. l), but no auditory exostoses. The dehiscence on the left side, which
is slightly larger than that on the right,
measures 9.5 mm by 5.5 mm. A “button osteoma,” measuring approximately 12 mm in
diameter, and protruding 2 mm from the surface of the frontal bone, is centered just above
the right supraorbital ridge. Dorsal to the
foramen magnum and to the right of the
midline on the occipital is a contact facet
measuring 12 x 8 mm (Fig. 2). There is little
indication of a corresponding facet on the
spinous process of the axis, but this part has
sustained postmortem damage making observation difficult.
Two examples of cervical vertebral fusion
are present. The first involves the atlas,
which is fused to the occipital (Figs. 1, a), a
condition usually referred to as occipitalization of the atlas, or atlas assimilation. Although well formed and basically normal in
appearance, the atlas nevertheless exhibits
some unusual features. First, the transverse
processes of the vertebra lack foramina; second, the inferior articular facets are unusually large and somewhat more convex in
sagittal section than normal; and third, the
left side of the posterior arch has been flattened against the base of the skull. The usual
atlanto-occipital articulations do not exist,
and the remainder of the atlas, except for the
transverse processes and a portion of the anterior arch to the right of the midline, is
solidly fused to the occipital.
The second example of cervical fusion involves C2 and C3 (Fig. 3). Except for their
separated transverse processes, these two
vertebrae form a single unit, a so-called block
vertebra. All foramina, including the intervertebral foramina defined by the two vertebrae, are well-formed, and the same is generally true of other parts of the vertebrae.
There is one exception, however, this being
the odontoid process, which shows distinct
beveling toward its apex, especially on the
right side. The odontoid has also been deeply
impressed where it contacted the anterior
arch of the atlas during extension of the neck,
and a step has formed between this surface
and the nonarticular surface below.
A facet on the superior surface of the spinous process of C4 extends back approximately 10 mm from the edge of the neural
canal (Fig. 41, while the opposing facet on C3
is much smaller and poorly defined. The inferior surface of C4 contains a small facet
similar to that on C3. Just below the superior
ATLANTO-OCCIPITALFUSION AND SPONDYLOLISTHESIS
Fig. 1. Fusion of first cervical vertebra with base of skull. Note large tympanic dehiscences
(dehiscence on right side indicated by arrow).
Fig. 2. Base of skull with facet (arrow) indicating contact with spinous process of second
cervical vertebra.
383
384
C.F. MERBS AND R.C. EULER
Fig. 3. Fusion of second and third cervical vertebrae.
Fig. 4. Fourth cervical vertebra showing osteophyte development into neural canal, facet on
superior surface of spinous process, and deep impression below left articular facet.
articular facets of C4 are impressions produced by contact with the inferior articular
processes of C3, the condition being especially pronounced on the left side. These two
vertebrae also exhibit osteophyte development extending from the margins of their
opposing bodies dorsally into the neural canal
and laterally over the pedicles. This development is more prominent on C4 and has a
markedly pitted appearance. Only two cervical vertebrae below C4 were recovered and
both are fragmentary.
Twelve thoracic vertebrae were recovered,
but all have damaged transverse and spinous
processes. In addition, units 1-3 lack bodies.
All nine of the recovered bodies, T4-Tl2,
show slight to moderate osteophyte development on their anterior margins. In addition,
the body of T11 has been slightly compressed,
an estimated 2 mm having been lost from its
anterior height.
Five lumbar vertebrae were recovered, but
only the first and last are relatively complete. The last unit (L5) is separated into two
parts (spondylolysis), the separation having
occurred between the superior and inferior
articular processes (pars interarticularis)
(Fig. 5). The portion of L5 containing the
body, pedicles, and superior articular processes, continuous with the vertebral column
above this point, shows evidence of having
shifted forward approximately 15 mm (spondylolisthesis) (Fig. 6). The shifted portion of
L5, but not the separated neural arch, then
became fused to the sacrum through ossification of the intervertebral disc (L5/S1),thus
making the olisthesis a permanent part of
the osteological record (Fig. 7).
There are large areas of contact between
the spinous processes of L3 and L4 (18 x 9
mm), and between those of L4 and L5 (18 x
11 mm), and the inferior articular processes
of L4 have been broadened and flattened into
facets (approximately 14 mm in diameter)
that articulate with the separated edges of
the pars interarticularis of L5 (Fig. 8). The
spinous process of L4 has been beveled posteriorly through contact with that of L3 (Fig.
8). All of the contact facets have irregular
surfaces and margins, and some contain
small circular pits. Evidence of disc degeneration (osteophyte formation) is present on the
superior margin of the L3 body, but this area
is too damaged to make similar observations
for L4, L5, or the sacrum. All facets composing the L4-5 apophyseal articulations show
evidence of degenerative joint disease (osteoarthritis), and the sacro-iliac articulations
have also developed a rim of new bone indicative of joint degeneration.
Evidence of degenerative joint disease is
present in the bones of both elbows. The lat-
ATLANTO-OCCIPITALFUSION AND SPONDYLOLISTHESIS
Fig. 5. Fifth lumbar vertebra and sacrum, dorsal view, showing spondylolysis (complete,
bilateral) through pars interarticularis of L5 (separation on right side indicated by arrow).
Fig. 6. Fifth lumbar vertebra, superior view, showing olisthesis (arrow) of L5 relative to S1.
385
386
C.F. MERBS AND R.C. EULER
Fig. 7. Fifth lumbar vertebra and sacrum, ventral view, with ossification of disc (arrow)
between L5 and S1.
Fig. 8. Fourth lumbar vertebra. A. Inferior view, showing faceting of spinous process and
inferior articular processes. B. Right view, showing beveling of spinous process from contact
with L3.
ATLANTO-OCCIPITALFUSION AND SPONDYLOLISTHESIS
387
Fig. 9. Left tibia, proximal end, showing depression fracture of lateral condyle.
era1 trochlear ridge of the right humerus
shows surface erosion, while that of the left
humerus shows deep pitting, which extends
dorsally as lipping between the trochlea and
capitulum. Although the capitulum itself is
free of pathology on both sides, the head of
the left radius contains a small area of erosion, while that of the right radius is too
damaged to allow observation. Both radii
show arthritic lipping at their distal ends
with that on the left side being slightly
greater than that on the right. A middle
manual phalanx contains evidence of a lytic
lesion (osteomyelitis) at its proximal end.
The lateral condyle of the left tibia has
sustained marked depression with three fracture lines evident-two straight and one curvilinear Wig. 9). One extends from the
posterolateral corner of the condyle to the
approximate center of the intercondyloid eminence; another from the approximate midpoint of the first to the anterior margin of
the condyle; and the third, curvilinear in
shape, from the lateral margin of the condyle
to the intercondyloid eminence, where it
meets the first. The third line lies several
millimeters inside the anterior margin of the
condyle over most of its route and crosses the
second line. Pronounced callus development
is evident along the second fracture line with
only traces visible along the first and third.
The fracture area covers two-thirds of the left
condyle and has produced a maximum depression of approximately 7 mm in its surface.
The patellar surface of the lateral condyle
on both femora contains an area of roughened, porous bone, typical of degenerative
joint disease, with that on the left side covering approximately twice the area of that
on the right. The superior margin of the patellar surface also shows considerably more
osteophyte development on the left side than
the right. The patellae, themselves, also contain roughened, porous areas, but here involvement is greater on the right side than
the left. The proximal articular surfaces of
the tibiae show no evidence of degenerative
change, but small “squatting facets” are
present at the distal ends. In addition, a small
bony spur extends from the margin of the
proximal articular facet of a pedal phalanx.
DISCUSSION
Some features of the pathology described
here would not be considered unusual in an
Anasazi Pueblo woman. Asymmetrical deformation centered near lambda, for example,
is typical of Anasazi crania, with the condition usually attributed to the use of a cradleboard in infancy. The presence of “squatting
facets” on the tibiae is also not unusual in
Anasazi remains, but attributing them to the
flexion of the lower extremity that occurs
during habitual squatting (Ubelaker, 1978:
388
C.F. MERBS AND R.C. EULER
74) may be inappropriate here. The faceting
in Southwest Pueblo women is more likely
due to the hours they spend kneeling before
their metates while grinding maize and other
foods, and the condition in this group would
thus more appropriately be termed “kneeling facets.”
The evidence for joint degeneration (osteoarthritis) in both elbows of the Bright Angel woman is concentrated in the flexionextension rather than the rotational aspect
of this joint. This pattern has been identified
more frequently in women than men among
Eskimos and has been attributed primarily
to movements and stresses involved in skin
preparation for clothing (Merbs, 1983). Associating the condition with food grinding in
Baja California, Merbs (1980) introduced the
term “metate elbow” as a female analog to
Angel’s (1966) well-known “atlatl elbow” in
males.
Other features of the pathology noted in
this woman are even more general in nature
and probably reflect her age more than anything else. In this category is the osteophyte
development indicative of disc degeneration
in the thoracic region of the vertebral column
and the slight compression of the T11 body.
The bony spur on the pedal phalanx, probably the result of tendon damage in a toe, may
also be included here.
The most interesting features of pathology
in the Bright Angel skeleton are those that
are unusual in themselves, and that in combination provide this individual with a
unique profile. Included here is the vertebral
fusion in the cervical region, the spondylolisthesis and disc ossification a t the thoracolumbar junction, the fracture in the left knee,
and, possibly, the Iytic lesion in the manual
phalanx.
The fusion of the atlas with the occipital
may be attributed to a failure of fetal sclerotomes to separate properly in the formation
of intervertebral spaces and discs, and the
condition would have been present a t birth.
Rare in skeletal series, and not always discernible in the living, population frequencies
are difficult to establish. However, a n incidence a t birth of approximately 0.5% has
been recorded by Correia (Gunderson et al.,
1976: 497).
Fusion of C2/3, also attributable to maldevelopment of fetal sclerotomes, frequently
accompanies atlanto-occipital fusion (McRae,
1960). Fusion of C2/3 is included under the
eponym “Klippel-Feil syndrome,” a term
which remains popular despite the recognition that it encompasses more than one etiologic and clinical entity. Estimates of frequencies vary enormously, from .002% (Luftman
and Weintraub, 1951) to .429% (Shands and
Bundens, 1956). The condition has been reported for a number of North American skeletal series, including some from the
Southwest (see Wade, 1981:123). Wade describes 5 cases of C2/3 fusion in 29 skeletons
from several closely related archaeological
sites dating between A.D. 600 and 1200 in
northeastern Arizona. However, none of
Wade’s five affected cases, all males, combine
the fusion of C2/3 with atlanto-occipital
fusion.
Congenital vertebral fusion frequently follows a familial pattern of occurrence, and
genetic inheritance is strongly suggested.
Both autosomal dominant and autosomal recessive models have been postulated, but it
is clear that the actual mode of inheritance
is far from understood. Incomplete penetrance and variable expressivity are frequently invoked to account for a lack of conformity to a simple, trustworthy Mendelian
model (Wade, 1981: 117). Environmental influences must also be considered.
Atlanto-occipital fusion has been associated with a low hairline and a short neck,
and some restriction of movement may be
experienced. In approximately 20% of cases,
the condition is associated with other developmental problems including anomalies of
the jaw, incomplete development of the nasal
cartilage, cleft palate, congenital deformation of the external ear, cervical ribs, abnormal vertebral number, and anomalies of the
urethra and urinary tract (Rothman and Simeone, 1975). Unfortunately, the Bright Angel skeleton does not lend itself to the
observation of any of these traits because
they are limited to soft tissue or because the
relevant skeletal parts are missing or too
fragmentary for study. Clinical information
on tympanic dehiscences is lacking, but given
the occasional association of ear anomalies
with atlanto-occipital fusion, the possibility
that the unusually large dehiscences in this
individual may be related to the fusion cannot be ruled out.
The combination of atlanto-occipital fusion
and fusion of C2/3 places greater than normal demands on the atlanto-axial articulation, particularly in flexion and extension.
This may be observed in the Bright Angel
adult in the greater than normal convexity
ATLANTO-OCCIPITALFUSION AND SPONDYLOLISTHESIS
of the inferior articular facets of the atlas.
The faceting on the occipital and on several
of the cervical spinous processes, the deep
impressions on C4 produced by the inferior
articular processes of C3, and the development of osteophytes on the dorsal margins of
the bodies of C3 and C4 are all indications of
extreme hyperextension of the neck. This
pattern of osteological change is compatible
with the use of a tumpline across the forehead for carrying heavy objects, the tumpline
tending to pull the head backward, thus placing considerable stress on the dorsal aspects
of the upper cervical vertebrae. In the case of
the Bright Angel skeleton, the pathological
results of tumpline usage have been exacerbated by the loss of neck mobility through
vertebral fusion.
Given the variation that exists between
the appearance of a condition and how a person is actually affected, attempts to reconstruct this relationship from prehistoric
skeletal remains must be viewed as speculative at best. The vertebral contact and resultant degenerative changes produced by
pronounced extension of the neck would certainly be expected to cause local pain, but did
the vertebral fusions also lead to impingement upon the spinal cord or other nerves
which could have resulted in more widespread neurological problems? McRae and
Barnum (1953) associate the development of
neurological signs from atlanto-occipital fusion with an odontoid process of abnormal
sue, in abnormal position, or with abnormal
mobility. The odontoid process of the Bright
Angel woman is somewhat unusual in terms
of shape, but it is not unusually large, and
its position relative to the base of the skull
(and thus the base of the brain) is well within
the range of normality. Its mobility in life is
difficult to judge.
McRae and Barnum (1953)found neurological involvement in individuals in which the
effective diameter of the neural canal, measured from the odontoid process to the closest
bony point behind it (margin of the foramen
magnum or posterior arch of the atlas), was
19 mm or less. Other authors Poznanski,
1974) suggest that a slightly smaller diameter can be tolerated with few or no symptoms. This measurement in the Bright Angel
woman is 14 mm. However, McRae and
Barnum’s standard was established on typical present-day patients, not small, prehistoric Pueblo Indians. Since the measurement
considered is not among those taken in gen-
389
eral osteological studies, standards of normality for Pueblo Indians do not exist.
However, a Sinagua woman of approximately equal size from the site of Nuvakwewtaqa (Chavez Pass), Arizona, with a
normal atlanto-occipital region, measures
only 15 mm across the neural canal. Pueblo
women thus appear to be smaller in this dimension than most present-day patients, and
the Bright Angel skeleton, with a diameter
of 14 mm, is still probably within the range
of normality for its population.
However, given the extreme extension of
the neck already discussed, and the natural
narrowing of the neural canal it would produce, the true minimal diameter of the canal
may be obvious only during this extension.
The various indications of vertebral contact
during maximum extension allow the reconstruction of this position quite accurately as
well as the measurement of the canal at various levels. In so doing, the minimal diameter is found to be no more than 8 mm
(between C3 and C4), a narrowing that very
likely did produce observable neurological
changes. Adding to the problem is the fact
that the part of C4 that would have impinged
upon the spinal cord in this individual, the
anterior margin of the neural arch, has an
unusually sharp edge. The osteophyte development between C3 and C4 is also impinging
upon the space of the fourth cervical nerve, a
situation which may have further aggravated the neurological situation.
Among the symptoms associated with reduction of the neural canal and bony impingement upon the spinal cord, according to
McRae and Barnum (19531, are numbness
and pain in the arms, weakness of the legs,
muscle control problems in both limbs, occipital headache, blurring of vision, and double
vision. McRae and Barnum add that head or
neck trauma may play some role in the onset
of these symptoms in a condition that may
otherwise have been asymptomatic since
birth.
The depression fracture of the left tibia appears to have been caused by acute trauma,
most likely produced by a fall, with the lateral condyle of the femur acting as a hammer
and the opposing tibia1 condyle as an anvil.
The femur itself shows no evidence of
trauma. The fracture would most likely have
taken place while the left leg was extended,
perhaps even hyperextended, with the full
impact of the shock passing through the knee
while it was in a position extremely vulner-
390
C.F. MERBS AND R.C. EULER
able to fracture. The lack of remodeling in
the fracture area indicates that the unaffected posterolateral one-third of the condyle
served as the sole lateral support for the femur, and that disruption of normal movement in the knee was probably not major.
However, the unaffected portion of the condyle does contain a n area of roughened bone
(9 x 4 mm), applied to the smooth articular
surface, which is indicative of some joint disfunction. The osteoarthritic degeneration involving the patellar surface of the femur and
the patella itself is very likely related to the
trauma. Both knees are affected, but overall
the pathology is distinctly more advanced on
the left side than the right.
The complete, bilateral spondylolysis affecting the last lumbar vertebra in the Bright
Angel woman is not unusual (Coyne, 1981:
153; Merbs, 1983: 35-42), nor is the olisthesis
that followed it. However, the bony ankylosis
of the affected body to the sacrum below
through ossification of the intervertebral disc
has never been reported for a n archaeological specimen (T. Dale Stewart, personal communication) and is extremely rare clinically
(Leon L. Wiltse, personal communication).
Since the degree of olisthesis is established
by the relative positions of two osseous units
to each other, held in place by soft tissue
(ligaments and disc), it, is a difficult condition
to reconstruct in archaeologically derived
material devoid of soft tissue. When such
reconstruction is possible, it is based upon
the matching of osteophytes on the bodies of
adjacent vertebrae, or other secondary osseous changes in the region of the separation,
and it is a n estimate a t best (Merbs, 1980).In
the case of the Bright Angel woman, however, the ossification of the disc formed a
bony connection that provides a permanent
and accurate picture of the olisthesis that
occurred. Spondylolisthesis ranges from cases
that are barely detectable to those in which
the column slips completely off the vertebral
body below. The shifting in the Bright Angel
woman measures 15 mm, or slightly more
than one-third the width (estimated) of the
sacral body, a degree of slippage that would
place her in terms of severity in the upper
20% of individuals with this condition (Harris, 1959).
The reason for the ossification of the disc is
not readily apparent, especially since spondylolisthesis tends to decrease the stability
of the region and thus decrease the likelihood
of immobility and fusion. The most likely
cause, however, is discitis. Tuberculosis, one
possible cause of discitis, has been identified
in prehistoric Southwestern skeletal remains
(El-Najjar, 19791, but with this disease bony
ankylosis is usually preceded by massive
bone destruction. There is no indication of
this kind of destruction in the Bright Angel
skeleton. Nor is there any evidence of ankylosing spondylitis or rheumatoid arthritis in
the region of the ossified disc, or in any other
part of the skeleton. Evidence of generalized
osteopenia leading to traumatic collapse in
the affected region is also absent.
Staphylococcus bacteremia is a much more
likely cause of infectious discitis and ultimate fusion, according to Wiltse (personal
communication), but other bacteria cannot
be ruled out. The bacteremia could have developed from a n infected foot or hand that
continued to be used. In a few days or weeks
the bloodstream might then have become
heavily infested with the bacteria that could
produce multiple areas of sepsis, or lodge in
a single place. The intervetebral disc is a
favorite place for them to lodge, according to
Wiltse, perhaps more so if the disc is subjected to inflammation and degeneration
from spondylolisthesis. This type of fusion
takes only a year to 18 months to occur. In
this context, it is tempting to see the pathological middle manual phalanx of the Bright
Angel woman as representing the point of
entry for the bacteria that eventually led to
the ossification of the disc, but this is nothing
more than speculation.
It is also possible that the fusion was caused
by a noninfectious discitis. Wiltse reports
that he has seen these spontaneous fusions
many times in patients who did not have
spondylolisthesis. Reviews of these patients’
histories disclosed no indication of infection,
or at least nothing severe enough to make
the patient sick.
CONCLUSIONS
In terms of cranial features and general
body form, the adult skeleton from Bright
Angel Ruin is typical of Pueblo Indian females. Accentuating this picture are skeletal
changes consistent with the use of a cradleboard during infancy, the carrying of heavy
objects with a tumpline, and the use of a
mano and metate in food preparation.
The skeleton also shows evidence of a congenital problem, fusion of the first cervical
vertebra with the base of the skull, and fusion of the second and third cervical vertebrae. This fusion (actually a failure of
developing vertebrae to separate) increased
ATLANTO-OCCIPITAL FUSION AND SPONDYLOLISTHESIS
the amount of movement occurring between
the first and second cervical vertebrae. In
combination with the habitual hyperextension evidenced in the upper cervical vertebrae, the result was considerable reduction
in the size of the neural canal, allowing a
sharp edge of bone to impinge upon the spinal
cord, and very likely producing neurological
problems affecting the arms and legs, and
vision.
The Bright Angel skeleton also shows evidence of trauma, a depression fracture of the
left knee, a compression fracture of a lower
thoracic vertebra, and spondylolysis of the
last lumbar vertebra. The spondylolysis was
followed by spondylolisthesis and ossification
of the intervertebral disc between the affected unit and the sacrum, thus fusing these
two units in their position of olisthesis. The
fusion appears to have been caused by a discitis, most likely owing to staphylococcus
bacteremia, and possibly initiated by a n infected finger. The fractured knee and compressed thoracic vertebra are compatible with
a fall, with both possibly representing the
same traumatic event. Although spondylolysis is generally attributed to gradual bone
separation, a “fatigue fracture” resulting
from repeated or habitual stress (Wiltse et
al., 1975), the other evidence for a fall in the
Bright Angel woman makes it necessary to
consider acute trauma as the possible cause
of the spondylolysis in this skeleton. Incomplete separation (Merbs, 1983)may be interpreted as a fatigue fracture “in progress,”
but once the separation has become complete, it is unlikely that the alternative etiologies may be distinguished from their
skeletal appearance. In other words, the fractured tibia and the spondylolysis, and possibly all three fractures, may have resulted
from a single traumatic event such as a severe fall. All that can be established with
respect to the timing of the three fractures is
that they occurred some time (perhaps years)
before the death of the individual, allowing
for secondary degenerative changes to take
place.
Although not related etiologically, the congenital condition and the fractures-may have
had a n effect upon each other. The neurological problems associated with the cervical fusions may have prompted the fall that
produced the fractures, for example, or the
trauma produced by the fall may have aggravated the neurological conditions. In any
event, the profile of pathology reconstructed
from the skeleton of this ancient occupant of
391
the Grand Canyon indicates that her life was
indeed a harsh one.
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