High correlation between inner and outer glenoid circle diameters and its clinical relevance

Area of Science:

• Orthopedic surgery
• Radiology
• Anatomy

Background:

• Glenoid bone loss measurement in shoulder instability often relies on the best-fit circle method.
• Current methods lack precision, especially with missing glenoid rim segments, leading to errors in radius definition.
• A more consistent method is needed for accurate paleo-glenoid assessment.

Purpose of the Study:

• To investigate the relationship between the Sugaya inner circle and the Itoi outer circle for glenoid measurement.
• To establish a more consistent method for assessing paleo-glenoid morphology and bone loss.

Main Methods:

• Examined 95 normal dry scapulae using digital photography and HOROS® imaging software.
• Drew inner (best-fit inferior) and outer (tubercles tangent) circles by two investigators.
• Analyzed diameters and areas, assessing inter- and intra-observer agreement using ICC and a Bayesian regression model.

Main Results:

• Demonstrated a very strong significant correlation between inner and outer circle diameters (r=0.92) and areas (r=0.94).
• Excellent inter- and intra-observer agreement (ICC ≥ 0.93) was found for both circle measurements.
• The ratio of inner to outer circle diameter was consistently 0.74.

Conclusions:

• A strong correlation exists between inner and outer glenoid circle measurements.
• The combined use of inner and outer circles and their ratio provides a more reliable estimation of bone loss.
• This method enhances paleo-glenoid morphology appreciation and aids surgical decision-making in shoulder instability.