Description of pathological conditions in
the skeleton of an adult male brown bear
Ursus arctos from the Cantabrian range of
mountains (Reserva Nacional de Caza de
Riaño, León)
PINTO, A. C.1 & ETXEBARRÍA, F.2
Bears are generally big-sized animals
and have few natural enemies. A wound
bear therefore has good chances of recovering
from trauma or disease without being
meanwhile attacked. The lack of natural
enemies also implies that many of these
animals can reach advanced ages, favouring
the quantitative as well as qualitative
increase in pathological conditions.
The literature dealing with skeletal
diseases in the extinct cave bears is very
rich. This is due to the very many fossils of
this species recovered in caves throughout
Europe, many of them displaying spectacular
pathological conditions. On the
other hand, the literature dealing with
skeletal conditions on present day brown
bears is much more scarce, as these animals
do not use limestone caves as intensively
as cave bears did, and therefore their
remains are, more frequently than not,
lost.
When thinking on the ecological
implications of cave bear skeletal conditions,
we can only use as comparation our
present knowledge of its extant counterpart,
the brown bear or other temperate
modern bears, in order to make inferences.
It is therefore important to create a log of
information on present day bear pathologies.
In this paper we describe in detail the
pathological conditions found in the skeleton
of a present-day brown bear Ursus
arctos from the Cantabrian range of mountains
in N. Spain. This specimen is kept in
the Centro de Recuperación de Animales
Silvestres (Valladolid), and was found dead
at the Reserva Nacional de Caza de Riaño
(León). It has a very great number of relevant
pathological conditions, some of
traumatic origin, some of infectious origin,
throughout the skeleton, chiefly
affecting the functioning of the vertebral
spine, pelvis and limb elements as described.
DESCRIPTION OF THE PATHOLOGIES
This is the complete skeleton of a present
day brown bear, an adult male with a
cementum age of 20±2 years (J. Seijas,
pers. comm), and therefore a very old bear
by modern Cantabrian Mountains standards.
The skeletal remains of this specimen
show grave lesions, that have affected
to its locomotion and general quality of
life. Below we describe all the alterations
observed in each one of the skeletal elements.
Almost all of them suffer from
anomalous conditions, in greater or smaller
degree.
Lost post-mortem: Right M2, left M3,
right P1 and right and left I1.
• Lost intra-vitam: Left I2. Advanced
alveolar resorption.
• Alveolar resorption affecting the
external bone wall of right M3 and left
M2
• The enamel of the crown of the cheek
teeth is completely worn, and secondary
dentine protects the pulp cavity
Mandible
• Caries: Affecting distally the right
M2 and M3, and also to the left M2
• Intra-vitam breakage of the canine
teeth, probably in events related with
sexual competition. The stumps appear
very rounded. The pulp cavity is exposed.
• The temporo-mandibular joint
shows eburneation.
Maxilar
• Post-mortem loss of right P3, left P1
and left I1.
• Intra-vitam loss: Right I1. The alveolus
has been resorbed and there is a fistulae
discharging towards the nasal bone
between I1 and I2.
• Resorption of the external wall of the
alveoli affecting right M2.
• Right M2: loss of oclusal enamel and
caries
• Agenesia right P1
• Fistulae at the root of right M1, discharges
towards bucal
• Right canine has an intra-vitam breakage
of the cusp and resorption of the
external wall of the alveolus as well as
some signs of periodontal pathology.
• There are also some lesions with
bone resorption in the palate.
• The enamel in all molars has been
entirely worn down exposing the pulp
cavity, which appears protected by secondary
dentine.
Cervical vertebrae
Around the articular surface of the
atlas there is a complete circle of osteophytes.
The axis is in a comparatively
good condition. The next five cervical vertebrae
also show osteophytes and exostoses
along the antero-distal edge
Dorsal vertebrae
These vertebrae (14) are affected in
varying degrees by eburneation of the articular
surfaces, rings of osteophytes along
the edges and exostoses. These exostoses
acquire great size from the 6th vertebra
downwards, affecting the anterior surface.
Vertebrae 7t h, 8t h and 9t h are fused
through great exostoses and calcifications
in its anterior area. The body of vertebra 9
is greatly disfigured. The anterior exostoses
and articular osteophytes appear
through till the last vertebra, very modified
also with de-calcification and anomalous
disorganised new bone production. It
appears also fused to the first lumbar vertebra.
Lumbar vertebrae
The first lumbar vertebra appears
almost entirely fused with the last dorsal
vertebra. Exostoses and disorganised bone
formation affect the 1st and the 2nd lumbar
vertebrae. The three last ones have also
exostoses, although of smaller size.
Tail vertebrae
The three first ones show abundant
great sized exostoses (21x12x4 mm.). Las
three last ones do not show lesions.
Scapula
The right scapula shows an osteochondroma,
eburneation that exposes the
spongy bone tissue and osteophytes in the
articular surfaces. It also has an intra-vitam
rip on the blade, that appears healed
without infectious processes and without
production of new bone.
Humerus
The right humerus has an eburneation
in the inner proximal articular surface. It
shows also a great circular exostose (11
mm. diameter) in the middle of the articular
surface and circle of osteophytes
along its inner edge. Distally the humerus
shows great wear of the joint and pseudoarticular
surfaces produced by the intense
pathologies affecting radius and ulna,
explained below.
The left humerus shows in the proximal
articulation eburneation and osteophytes.
Probably to compensate the great
lesions in the right side, the muscular
insertion appears very developed. The distal
articulation has a circle of osteophytes,
not so developed. The diaphysis of the left
humerus is notoriously wider and stronger
than that of the right arm. As we will see,
the left arm is the only healthy limb this
animal had.
Radius and ulnae
The right radius and ulnae appear
crushed or with multiple fractures affecting
both bones. These are old fractures
with formation of new bone tissue, that
fuses both bones. They appear very distorted
and their functionality must have been
very limited. This lesion affects the totality
of both bones and plays also a role in
the deformations suffered by the proximal
and distal joints and by adjacent bones
The edges of the distal articulation in
the left radius show an incipient circle of
osteophytes. The left ulna shows osteophytes
surrounding the distal articulation.
Carpal and metacarpal bones
The carpal bones of the right hand
show an intense wear and eburneation of
the articular surfaces, leading to the general
loss of bone mass and to the formation
of rows of osteophytes. The metacarpal
bones have similar pathologies. The 1st
has distally a healed fracture, a fistulae and
osteophytes. The second one seems to have
also a healed fracture, as well as anomalous
bone production on the diaphysis and
exostoses, that extend to the remaining
metacarpal bones. The 4th metacarpal has
exostoses in proximal.
The carpal bones of the left arm are
bigger and have great osteophytes, that
affect also the metacarpal bones. The 1st
left metacarpal shows crushing, exostoses,
osteophytes around articular surfaces and
pseudo-arthrosis in mid diaphysis. The
remaining metacarpal bones are affected
by osteophytes in varying degrees at the
joints and exostoses at the diaphysis..
Falanges
The articular surfaces in the right hand
falanges are circled by osteophytes, have
exostoses in the diaphysis, eburneations
and arthritic deformations. The 3rd falange
of the 2nd finger is distally anomalous.
The 3rd finger has two falanges fused in an
anomalous position. The 5th finger has an
amputation in the first falange, with new
bone growth over the stump. The fingers
of the left hand have similar alterations.
Innominate
Luxation of the left innominate, that
has then formed a secondary sub-articulation
with great proliferation of newly formed
bone that grows disorganised suggesting
an infectious. The right side appears
relatively healthy, and the innominate
keeps its general symmetry.
Femur
The right femur head has eburneation
with wear discovering spongy bone tissue.
Distally, osteophytes in the articulation
with the tibia. The diaphysis show in posterior
a great development of lobular exostoses,
probably result of the ossification of
the muscle insertions. Tibia and fibulae
show amputation of the distal third.
The left femur shows bone degeneration
and resorption and loss of bone mass
and shape at the femur head, possibly due
to an infectious process associated to the
great lesions in the innominate, descried
above as luxation. Dorsally the diaphysis
shows new bone in formation.
Rotulae
Both rotulae have osteophytes around
the articular surfaces.
Tibiae and fibulae
The right tibia shows amputation of
the distal third, with bone formation as
lobular exostoses in the stump area. It has
also exostoses in the diaphysis, in the muscle
insertion area and in the articulation
with the fibula. The right fibula shows
also amputation of the distal third and
anomalous bone production covering its
whole surface.
The left tibia has osteophytes around
the proximal articulation, exostoses and
alterations in the articulation with the
fibula. The left fibula shows pseudo-arthrosis
in the diaphysis. Distally, the head
has a healed fracture with new bone formation
forming lobes.
Calcaneum, astragalus and tarsal
(left)
Both show eburneation and bone formation,
osteophytes around articular surfaces
and exostoses affect these bones.
Metatarsal and falanges (left)
The five are kept, and they show the
following alterations: anomalous bone formation
as lines of osteophytes, exostoses,
decalcifications, eburneations, sindesmophytes,
fistulas and infectious osteomielitis.
The falanges have similar arthritic
alterations in lesser degree.
Ribs
The 14 right ones have osteophytes
and deformations in the proximal area.
Eburneation, osteophytes, arthrosis and
healed fractures are also present. As for the
14 left ribs, 4 have osteophytes and deformations
in the articulation with the vertebrae.
One has a healed fracture with anomalous
bone formation.
CLASSIFICATION OF THE PATHOLOGIES:
TRAUMA VERSUS INFECTIONS
The lesions descried have two origins:
traumas or infections. Both can be related,
when the soft tissues get an infection and
transmit it to the bones through the
blood.
Traumatic pathologies
These affect to the front right limb and
to the bones in both legs. The right scapula
has a breakage which is a direct trauma.
Although there is no bone formation
in this wound, this trauma could have
affected to soft tissues around the scapula.
An infectious process started then, and
manifests itself in the vertebral spine.
The right forearm shows alterations
consistent with several traumatic lesions
–crushing or multiple fractures- affecting
the whole of radius and ulnae. Healed
fractures can be seen that affect to both
diaphysis, now fused and shortened.
The right leg has a traumatic amputation
of part of the tibia and fibula. This
amputation does not appear to have been
infected. Doubtless it has affected the ability
to move of this animal, that in its
movements had to rely strongly in the left
leg and arm. The left leg shows a double
fracture of the fibula. The proximal fracture
never re-fused and there is a pseudoarthrosis.
The bones of hands and legs
have lesions which are consistent with
infections, and are not an age triggered
degeneration.
As for the healed baculum fracture,
this is a relatively frequent lesion produced
in the heat of mating, and is of no consequence
for bears.
Therefore, and summarising, the main
traumatic lesions suffered by this specimen
were:
a) Ripping of the right scapula with
osteolysis
b) Polytraumatic "catastrophic member"
right forearm.
c) Traumatic amputation of right tibia
and fibula, with a well healed stump,
affecting the ability to move.
d) Double fracture of the left fibulae
with pseudoarthrosis of the most proximal
fracture.
Infectious pathologies
There is an infectious process affecting
sectors of the vertebral spine, producing
the fusion of some vertebrae and the
almost complete disintegration of others.
While the affected ones are very much
altered, the ones out of the affected zones
appear normal and healthy.
The anomalies concentrate in two
spots: there is a great decalcification and
complete fusion of the 7th and the 8th
through great exostoses that affect also the
9th with a great distortion of the body.
The second area with important alterations
goes from the 12th dorsal vertebrae
to the 1st lumbar, that appears greatly distorted.
The infectious process can be detected
also in the left innominate and proximal
femur. It could be therefore a septic arth-
ritis, infectious process that has produced
a proliferation of bone in the left innominate
as well as a very important resorption
in the femur head. This process has closed
the major sciatic scooping.
The symmetry between the right and
left side of the pelvis, the lack of disorganisation
or disharmony in the general
structure, and the conservation of all the
skeletal elements suggests that this is not
a healed fracture of the innominate, with
an open wound and an infectious component,
but that the infection arrived here
from a focus placed in other lesion in the
body, through the blood stream.
POSSIBLE AETIOLOGY OF THESE
PATHOLOGIES
The particular disposition of the infectious
lesions reminds of the developmental
mechanism of tuberculosis in human
being. In men, Pott’s disease lodges itself
in the 12th dorsal vertebrae, inserted in
the hideosoas muscle, responsible for the
upward movement of the thigh. The
infection gets into this muscle, from
which it spreads to its distal insertion
point, in the lesser trochanter of the
femur, entering from underneath the left
innominate, and producing the infection
and subsequent alterations in this bone.
This similarity with how this disease
develops in human beings suggested
NEIBURGER (1984) his interpretation
of the pathologies observed in a specimen
of extinct fossil bear (Arctodus simus) .
Other workers dismissed this diagnosis
(R O T S C H I L D, 1988; R O T S C H I L D &
TURNBULL, 1987), because of the lack
of new bone formation in tuberculosis as
opposed to the exuberant formation of
new bone in Neiburger’s specimen. After
finding treponema antigens in a sample
from this bear, they proposed alternatively
that it was treponematosis or syphilis
what was causing these lesions. Neiburger
however answered that the formation of
new reactive bone is not incompatible
with tuberculosis (N E I B U R G E R &
TURNBULL, 1990). The fact that the
scientific magazine Nature echoed twice
this debate, is a reflect of the interest aroused
by the origins of a disease as syphilis.
In a subsequent paper, ROTHSCHILD
et al. (1993) analyse bear collections of
every genus in several museums, and they
diagnose them with spondiloarthropaty.
They consider first rheumatoid arthritis,
but dismiss it because of the lack of reactive
tissue; then consider tuberculosis and
dismiss it because of the distinct appearance
of the new bone. There is only then
left arthritis, be it psoriasic or be reactive.
The first has not been documented in
bears, and therefore the only option left is
reactive arthritis of sexual transmission.
Although the argument till here is interesting,
then the authors put this into
relation with baculum fractures, which
leaves us short of an entirely satisfactory
answer to this problem.
A biomedical analysis of a sample from
the Riaño bear with this orientation will
doubtless yield data relevant in this context.
Antigen as well as DNA studies will
allow to determine whether this specimen
has been affected by any of these two diseases.
In the meantime, the great abundance
of grave traumatic lesions in the Riaño
bear, that compromise the functional sta-
bility of the animal, can suffice to explain
the sequence of later lesions. For example,
if this animal lost a leg to a poacher’s
leash, as it does happen to bears in the
area, will later be more liable to falling
down, and generally be more liable to further
damage.
www.udc.es/iux/almacen/articulos/cd26_art33.pdf
is a dangerous adversary for any tigers.
is a dangerous adversary for any tigers.
