Wrist extensor muscle pathology in lateral epicondylitis

Area of Science:

• Orthopedics
• Sports Medicine
• Muscle Physiology

Background:

• Lateral epicondylitis (tennis elbow) is a common condition causing elbow pain.
• The extensor carpi radialis brevis (ECRB) muscle is often implicated in this condition.
• Understanding ECRB muscle morphology is crucial for explaining functional deficits.

Purpose of the Study:

• To investigate the morphological characteristics of the extensor carpi radialis brevis (ECRB) muscle in patients with lateral epicondylitis.
• To compare ECRB muscle morphology in patients versus healthy controls.
• To identify potential pathological changes contributing to lateral epicondylitis.

Main Methods:

• Muscle biopsies were obtained from the ECRB in 20 patients with lateral epicondylitis.
• Enzyme- and immunohistochemical analyses were performed on the biopsies.
• Morphological features and fibre type percentages were assessed.

Main Results:

• Patients with lateral epicondylitis showed significantly more frequent morphological abnormalities compared to controls.
• Observed abnormalities included moth-eaten fibres, fibre necrosis, and signs of regeneration.
• A higher percentage of fast-twitch oxidative (type 2A) fibres was noted in patients.
• These changes were equally distributed in proximal and distal ECRB portions.

Conclusions:

• The observed ECRB muscle changes may result from cumulative mechanical and/or metabolic overload.
• Physical damage to the ECRB muscle, alongside elbow pain, likely contributes to reduced muscular performance in lateral epicondylitis.
• These findings highlight the structural basis for functional impairment in tennis elbow.