Labral morphology does not compensate for reduced bony glenoid concavity in stable shoulders

Area of Science:

• Orthopedics
• Biomechanics
• Radiology

Background:

• Glenoid concavity is crucial for shoulder stability through the concavity-compression mechanism.
• The bony glenoid concavity (bony shoulder stability ratio, BSSR) is a key stability determinant.
• The labrum's role in compensating for reduced bony concavity in stable shoulders is not well understood.

Purpose of the Study:

• To investigate the relationship between labral and bony glenoid concavity.
• To determine if the labrum compensates for reduced bony concavity using the labral shoulder stability ratio (LSSR) and BSSR.
• To test the hypothesis that lower BSSR correlates with higher LSSR.

Main Methods:

• Retrospective analysis of 36 patients undergoing shoulder CT arthrography for non-instability reasons.
• Calculation of BSSR and LSSR from 3D multiplanar reconstructions of CT images.
• Measurement of concavity depth and radius for both bony and chondrolabral contours; correlation and subgroup analyses performed.

Main Results:

• Mean BSSR was 28.3% and mean LSSR was 77.9%.
• No significant correlation was found between BSSR and LSSR (r = 0.01, P = 1.000).
• Subgroup analysis of low vs. high BSSR groups showed no significant difference in LSSR.

Conclusions:

• Labral morphology does not compensate for reduced bony glenoid concavity in stable shoulders.
• The study did not find an inverse relationship between bone and labral concavity.
• Findings contradict the hypothesis of a compensatory labral mechanism for bony concavity deficits.