User:Abyssal/MVL Citing 22

Dinosaur peri
The right humerus of a Camarasaurus grandis exhibits a spur-like juxtacortical lesion resulting from the healing process following a "stress injury or repetitive overexertion of the muscles resulting in an avulsion." This spur-like lesion would have caused long term fascitis and myosistis.

The humerus is partially complete and was discovered in 1992 at the Bryan Small Stegosaurus Quarry of the Morrison Formation near Canon City, Colorado. Associated back vertebrae and centra from tail vertebrae were also recovered.

A ceratopsian scapula was also found to have infectious periostitis.

The mass caused by the periostitis has the appearance like woven fibers. The lesion's fusion and lack of porosity at its proximal and distal ends indicate the periostitis was inactive or healed. An area of periosteal stripping may have been caused by "violent injury to the humerus." "Undulating fibrous bundles" were observed oriented in the direction of the M. brachialis. The lesion is 25 by 18 cm wide. The axis of the spur is 25 degrees relative to the vertical axis of the humerus, and so this exostosis is not an osteochondroma, which would have formed at 90 degrees. An osteoblatic response "caused by the flexor motion of the M. brachioradialis" is the most likely cause for the extension of the bone. The authors infer that the inflammation of the muscles and periosteum would have also caused additional complications in the lower region of the forelimb as well. Characteristics of the mass limited its potential diagnosis to one of five possible diagnoses:


 * 1) Hypertrophic osteoarthropathy- couldn't be because of the development of the spur-like process.
 * 2) Osteoid osteoma- doesn't explain the spur or osteoblastic reaction.
 * 3) Shinsplints/Tibial stress syndrome- A possible origin as many symptoms would be held in common, but doesn't explain the spur.
 * 4) Myositis ossificans traumatica (circumscripta) - Possible source.
 * 5) Avulsion injury - Most likely source.

The pathology was believed to have originated with an avulsion injury of the M. brachialis causing "a downward sloping elliptical mass" and a tear at the base of the M. brachioradialis producing the bone spur. The movements of the limb would have been moderately to severely affected and "made everyday activities such as foraging for food and escaping predators harder to accomplish."

Procrastinated

 * 2001 in paleontology
 * 2001 in sauropodomorph research
 * 2001 in paleopathology
 * 1992 in paleontology

Reference

 * McWhinney, L., Carpenter, K., and Rothschild, B., 2001, Dinosaurian humeral periostitis: a case of a juxtacortical lesion in the fossil record: In: Mesozoic  Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University  Press, pp. 364-377.