Muscle atrophy and fatty infiltration after an acute rotator cuff repair in a sheep model.
BACKGROUND
rotator cuff tears (RCTs) are the most common tendon injury seen in orthopedic patients. Muscle atrophy and fatty infiltration of the muscle are crucial factors that dictate the outcome following rotator cuff surgery. Though less studied in humans, rotator cuff muscle fibrosis has been seen in animal models as well and may influence outcomes as well. The purpose of this study was to determine if the rotator cuff would develop muscle changes even in the setting of an acute repair in a sheep model. We hypothesized that fatty infiltration and fibrosis would be present even after an acute repair six months after initial surgery.


METHODS
twelve female adult sheep underwent an acute rotator cuff tear and immediate repair on the right shoulder. The left shoulder served as a control and did not undergo a tear or a repair. Six months following acute rotator cuff repairs, sheep muscles were harvested to study atrophy, fatty infiltration, and fibrosis by histological analysis, western blotting, and reverse transcription polymerase chain reaction (RT-PCR).


RESULTS
the repair group demonstrated an increase expression of muscle atrophy, fatty infiltration, and fibrosis related genes. Significantly increased adipocytes, muscle fatty infiltration, and collagen deposition was observed in rotator cuff muscles in the tendon repair group compared to the control group.


CONCLUSIONS
rotator cuff muscle undergoes degradation changes including fatty infiltration and fibrosis even after the tendons are repair immediately after rupture.


METHODS
Basic Science Study.
Department of Veterans Affairs, San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States.
Tammy
T
Luan
Department of Veterans Affairs, San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States ; Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States.
Xuhui
X
Liu
Colorado State University, Fort Collins, CO, USA.
Jeremiah T
JT
Easley
Department of Veterans Affairs, San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States ; Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States.
Bharat
B
Ravishankar
Colorado State University, Fort Collins, CO, USA.
Christian
C
Puttlitz
Department of Orthopaedic Surgery, University of California, San Francisco, CA, United States.
Brian T
BT
Feeley
PPARγ; SREBP-1; acute rotator cuff repair; fatty infiltration; fibrosis