These authors contributed equally
Version of Record online: 1 NOV 2003
Copyright © 2003 ASBMR
Journal of Bone and Mineral Research
Volume 18, Issue 11, pages 2023–2032, November 2003
How to Cite
Barr, A. E., Safadi, F. F., Gorzelany, I., Amin, M., Popoff, S. N. and Barbe, M. F. (2003), Repetitive, Negligible Force Reaching in Rats Induces Pathological Overloading of Upper Extremity Bones. J Bone Miner Res, 18: 2023–2032. doi: 10.1359/jbmr.2003.18.11.2023
This work was presented in part as an abstract at the 39th Annual Meeting of the American Society for Cell Biology, Washington, DC, December 11–15, 1999.
The authors have no conflict of interest.
- Issue online: 2 DEC 2009
- Version of Record online: 1 NOV 2003
- Manuscript Accepted: 10 JUN 2003
- Manuscript Revised: 13 MAY 2003
- Manuscript Received: 24 JAN 2003
- repetitive motion;
- work-related musculoskeletal disorder
Work-related repetitive motion disorders are costly. Immunohistochemical changes in bones resulting from repetitive reaching and grasping in 17 rats were examined. After 3–6 weeks, numbers of ED1+ macrophages and osteoclasts increased at periosteal surfaces of sites of muscle and interosseous membrane attachment and metaphyses of reach and nonreach forelimbs. These findings indicate pathological overloading leading to inflammation and subsequent bone resorption.
Introduction: Sixty-five percent of all occupational illnesses in U.S. private industry are attributed to musculoskeletal disorders arising from the performance of repeated motion, yet the precise mechanisms of tissue pathophysiology have yet to be determined for work-related musculoskeletal disorders. This study investigates changes in upper extremity bone tissues resulting from performance of a voluntary highly repetitive, negligible force reaching and grasping task in rats.
Materials and Methods: Seventeen rats reached an average of 8.3 times/minute for 45-mg food pellets for 2 h/day, 3 days/week for up to 12 weeks. Seven rats served as normal or trained controls. Radius, ulna, humerus, and scapula were collected bilaterally as follows: radius and ulna at 0, 3, 4, 5, 6, and 12 weeks and humerus and scapula at 0, 4, and 6 weeks. Bones were examined for ED1-immunoreactive mononuclear cells and osteoclasts. Double-labeling immunohistochemistry was performed for ED1 (monocyte/macrophage lineage cell marker) and TRACP (osteoclast marker) to confirm that ED1+ multinucleated cells were osteoclasts. Differences in the number of ED1+ cells over time were analyzed by ANOVA.
Results: Between 3 and 6 weeks of task performance, the number of ED1+ mononuclear cells and osteoclasts increased significantly at the periosteal surfaces of the distal radius and ulna of the reach and nonreach limbs compared with control rats. These cells also increased at periosteal surfaces of humerus and scapula of both forelimbs by 4–6 weeks. These cellular increases were greatest at muscle attachments and metaphyseal regions, but they were also present at some interosseous membrane attachments. The number of ED1+ cells decreased to control levels in radius and ulna by 12 weeks.
Conclusions: Increases in ED1+ mononuclear cells and osteoclasts indicate that highly repetitive, negligible force reaching causes pathological overloading of bone leading to inflammation and osteolysis of periosteal bone tissues.