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Ceratopsian pathology and dinosaur arthritis (NOT!)



 On Jan. 30th, Rob Meyerson asked about the fusion of the tail vertebrae in
our recently collected Tyrrell Museum ceratopsian and queried about the
possible role of arthritis. This posting is to address the presence (or
shall I say virtual non-presence) of arthritis in dinosaurs. I work mostly
on dinosaur trauma and bone fractures, so much of what I'm about to relate
is taken directly from what American paleopathologist Dr. Bruce Rothschild
(an arthritis expert- mostly modern HOMO, but has extensively investigated
the problem in extinct taxa) has published or related to me. The following
abstract was taken from:

 Rothschild, B.M. 1990. Radiologic Assessment of Osteoarthritis in
Dinosaurs. Annals of the Carnegie Museum, Vol. 59(4):295-301.

 "Osteoarthritis has been erroneously considered common in dinosaurs because
of semantic confusion. Gross remodeling of diarthrodial (articulating,
synovial-lined) bone, characteristic of osteoarthritis is extremely rare in
dinosaur specimens examined in this study. Radiologic techniques were used
to assess subtle signs of osteoarthritis that could not be recognized on
gross specimen examination. X-ray analysis of 664 weight-bearing metaphyses
of 121 individual dinosaurs, representing 18 genera, confirmed the rarity of
osteoarthritis in dinosaurs and suggests that weight alone does not have a
direct role in the development of osteoarthritis."

 Dr. Rothschild regularly travels worldwide and with portable X-ray
equipment in his quest for arthritis in dinosaurs and osteopathy in other
extant/extinct forms. As far as he can tell- there are only 2 examples of
true osteoarthritis known in dinosaurs and they are both from members of the
Belgian IGUANODON herd. Dr. Rothschild goes on to say it is important to
recognize that osteoARTHRITIS affects limb joints (ie. fingers, wrist,
elbows, hip, knee, toes) and that osteoPHYTOSIS involving bone spur
development and fusions affects the vertebral column. The two are manifestly
different.

 I'm aware of several major conditions that also cause vertebral fusions in
dinosaurs.

 1. Congenital defect (born/hatched) this way.
 2. DISH (diffuse idiopathic skeletal hyperostosis) a common condition
especially affecting sauropod tails with fusions of up to 4-5 contiguous
vertebrae. Despite its "painful appearance" I'm told DISH is not even a
pathologic condition per se, but is natures way of assisting the animal to
deal with stress points on the vertebral column. All the "arthritis" on the
sides of the vertebrae actually represents the ossification of ligaments
lateral to the vertebral bodies. Even though it is not truly a pathological
condition- it looks it and is often misinterpreted as arthritis.
Cross-section or X-ray of the specimen is quite revealing in showing
absolutely no involvement of the articulating surfaces of the affected
bones- despite massive fusion and osteophyte (ie. bone spur) development
externally, inside all centrum endplates and pre- and postzygapopyseal
articulations remain open. Neck vertebrae in tyrannosaurids occasionally
show fusion of two bones- I'm not sure if this is DISH but it would help
support the heavy head. 
 3. Trauma. Take the end of a normal hadrosaur tail. Normal, healthy
vertebrae, each enclosed in a periosteal lining. Now take said tail and have
another 3 ton hadrosaur accidently (deliberatly?) step on it. Result?
Unhappy, fractured, crushed and mangled vertebrae with ruptured periosteum,
massive internal-external bleeding- one homogenous gooey mass of pain.
During the subsequent healing process, the mangled bone pieces of each
individual vertebra will fuse back together and to other pieces of the next
vertebra, etc. etc. In this way fusions of up to 4 vertebrae (but usually
just 2) can be achieved. Often the vertbrae don't fuse back together in a
straight line so the tail would heal with a kink near the tip. This kink
would angulate the distal (tip) end of the tail off to either side or
slightly upwards. The healing process here is similar to when a person has a
bad back and in an operation the Doctor scrapes away at the centrum
endplates of two articulating vertebrae and they subsequently respond by
both putting out new bone tissue to repair the "damage", this new bone
tissue comes together and forms one contiguous mass, resulting in the fusion
of the two bones and bringing about increased support.     

 I suspect DISH was the cause of the fusion in the ceratopsian tail. In the
field it certainly looked like other examples of DISH from Albertan
ceratopsians. However, the tail still needs to be prepared before a firm
diagnosis can be made. Don't expect this to happen soon as it is not very
high on the preparation priority list.

 Given Dr. Rothschilds extensive knowledge of the topic, his continuous
extensive travels worldwide and other paleopathologists continuing search
for possible osteoarthritis in dinosaurs- one can deduce that this form of
osteopathy is most conspicuous in its absence or extreme rarity. One can
confidently say that dinosaurs were basically unaffected by arthritis. This
is one advantage they had over us. But why is the question. 
 
 Despite our knowledge, the use of the term arthritis/osteoarthritis as
being a common ailment in dinosaurs continues, even in popular/technical
literature published AFTER Dr. Rothschilds late 1980's-early 1990's medical
papers published in paleontological journals disproving so. This is
unfortunate. Hopefully this posting will help address this problem.,

 My paleopathology bibliography homepage (http://dns.magtech.ab.ca/dtanke)
will be undergoing a massive facelift sometime this Spring (hopefully around
Easter). The update will include photographs of bone fusions, DISH, trampled
hadrosaur caudal vertebrae, etc., etc. An annotated bibliography of dinosaur
paleopathology and related topics will also be added to the site. These
citations were culled out of the main bibliography. There are 559 citations
so far, 105+ pages.

 

 
Darren Tanke
Technician, Dinosaur Research Program
Royal Tyrrell Museum of Palaeontology
Drumheller, Alberta, Canada

             and

Senior Editor on the:
Annotated Bibliography of Paleopathology, Dento-Osteopathy and Related Topics
11,037 citations as of Jan. 19, 1997.
Visit our homepage at: http://dns.magtech.ab.ca/dtanke
Can you help with this ongoing project? Email me at: dtanke@dns.magtech.ab.ca