Multivariate analyses of rotator cuff pathologies in shoulder disability

Area of Science:

• Orthopedic Surgery
• Musculoskeletal Imaging
• Biomechanical Analysis

Background:

• Rotator cuff (RC) tears are a common cause of shoulder joint disability.
• The supraspinatus and infraspinatus muscles are most frequently torn, but their individual contributions to pathology are unclear.
• Muscle atrophy and fatty infiltration are indicators of RC muscle degeneration and may predict shoulder dysfunction.

Purpose of the Study:

• To investigate the relationship between rotator cuff muscle degeneration (atrophy and fatty infiltration) and superior humeral head translation.
• To determine the predictive value of specific rotator cuff muscle characteristics on shoulder functional disability.

Main Methods:

• Magnetic Resonance Imaging with arthrography (MRA) was used to assess RC muscle surface area, fatty infiltration, and superior humeral translation.
• Patients with superior (supraspinatus) and posterosuperior (supraspinatus and infraspinatus) RC tears were compared to controls with intact RC.
• Univariate and multivariate models were employed to analyze the contribution of RC measures to superior humeral translation.

Main Results:

• Univariate analysis showed infraspinatus surface area and fatty infiltration in both supraspinatus and infraspinatus significantly contributed to RC dysfunction.
• Multivariate analysis revealed that only infraspinatus surface area significantly affected superior humeral translation and differentiated tear types.
• Neither tear size nor fatty infiltration of either muscle predicted superior humeral translation in the multivariate model.

Conclusions:

• Infraspinatus muscle atrophy is the primary contributor to rotator cuff tear pathologies.
• The findings highlight a critical role for the infraspinatus muscle in maintaining shoulder stability and preventing functional disability.