Purpose
Partial rotator cuff tears can cause shoulder pain and dysfunction and are more common
than complete tears. However, few studies examine partial injuries in small animals
and, therefore a robust, clinically relevant model may be lacking. This study aimed
to fully characterize the established rat model of partial rotator cuff injury over
time and determine if it models human partial rotator cuff tears.
Methods
We created a full-thickness, partial-width injury at the supraspinatus tendon-bone
interface bilaterally in 31 Sprague-Dawley rats. Rats were euthanized immediately,
and at 2-, 3-, 4-, and 8-weeks after surgery. Fourteen intact shoulders were used
as controls. Samples were assessed biomechanically, histologically, and morphologically.
Results
Biomechanically, load to failure in controls and 8 weeks after injury was significantly
greater than immediately and 3 weeks after injury. Load to failure at 8 weeks was
comparable to control. However, the locations of failure were different between intact
shoulders and partially injured samples. Bone mineral density at 8 weeks was significantly
greater than that at 2 and 3 weeks. Although no animals demonstrated propagation to
complete tear and the injury site remodeled histologically, the appearance at 8 weeks
was not identical to that in the controls.
Conclusions
The biomechanical properties and bone quality decreased after the injury and was restored
gradually over time with full restoration by 8 weeks after injury. However, the findings
were not equivalent to the intact shoulder. This study demonstrated the limitations
of the current model in its application to long-term outcome studies, and the need
for better models that can be used to assess chronic partial rotator cuff injuries.
Clinical Relevance
There is no small animal model that mimics human chronic partial rotator cuff tears,
which limits our ability to improve care for this common condition.
Key words
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Article info
Publication history
Published online: October 21, 2022
Accepted:
August 17,
2022
Received:
January 19,
2022
Publication stage
In Press Corrected ProofFootnotes
Supported by the United States Department of Veterans Affairs Rehabilitation Research and Development Service (JC) and American Foundation for Surgery of the Hand (PF).
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Identification
Copyright
© 2022 by the American Society for Surgery of the Hand. All rights reserved.
