Common animal models lack a distinct glenoid labrum: a comparative anatomy study

Area of Science:

• Orthopedic Surgery
• Comparative Anatomy
• Histology

Background:

• Developing an animal model for labral healing is crucial for advancing surgical and biological strategies.
• Understanding the anatomical and histological characteristics of the glenoid labrum across species is essential for selecting appropriate models.

Purpose of the Study:

• To anatomically and histologically characterize the shoulder labrum in rats, rabbits, dogs, pigs, goats, and humans.
• To determine which animal species' glenoid labrum most closely resembles the human glenoid labrum.

Main Methods:

• Cadaveric glenohumeral joints from six species were harvested and photographed.
• Linear dimensions of the glenoid articular surface were measured, and capsulolabral complex continuity was assessed.
• Samples underwent histological staining (Safranin O/Fast green, Mallory Trichrome) for qualitative assessment of labral insertion.

Main Results:

• Goat glenoid dimensions most closely matched human glenoid dimensions.
• A continuous capsulolabral complex was observed in varying extents across species, with humans showing a distinct 2 to 8 o'clock pattern.
• No animal species exhibited an organized fibrocartilaginous labrum macroscopically or histologically, unlike humans.

Conclusions:

• The studied animal models lack a discrete fibrocartilaginous labrum comparable to humans.
• These animal models are unsuitable for research focused on evaluating labral pathology.
• Alternative models or modifications are necessary for studying glenolabral healing and pathology.