Histological Changes in Biceps Muscle after Tenotomizing the Biceps Long Head in a Rat Model

Area of Science:

• Orthopedics
• Muscle Physiology
• Histopathology

Background:

• Popeye deformity is a common consequence of long head biceps tendon rupture.
• This study investigates the histological alterations in biceps brachii muscles post-tenotomy of the long head biceps tendon.

Purpose of the Study:

• To examine the histological changes in biceps brachii muscles after tenotomy of the long head biceps tendon.
• To assess muscle cell size, fatty infiltration, and myostatin expression following tendon surgery.

Main Methods:

• Tenotomy of the long head biceps tendon was performed on Sprague-Dawley rats.
• Histological analysis included Hematoxylin and Eosin (H&E) staining, Oil-red O staining for fat, and myostatin immunohistochemistry.
• Muscle samples were collected at 4, 7, and 10 weeks post-surgery, with contralateral shoulders serving as controls.

Main Results:

• Hematoxylin and Eosin (H&E) staining revealed no alterations in muscle cell nuclei.
• A significant decrease in the cross-sectional area and total extent of biceps brachii muscle cells was observed post-tenotomy (p=0.00).
• Oil-red O staining and myostatin antibody immunohistochemistry showed no significant fatty infiltration or differences between operative and control sides.

Conclusions:

• Tenotomy of the long head biceps tendon leads to muscle cell atrophy and a reduction in relative muscle mass.
• No significant fatty infiltration or changes in muscle cell nuclei were detected.
• Myostatin expression remained unchanged, suggesting it is not a primary factor in these post-tenotomy muscular changes.