Is posterosuperior contact a normal occurrence in the shoulder?

Area of Science:

• Orthopedic Surgery
• Sports Medicine
• Anatomy

Background:

• Posterosuperior (internal) impingement involves the supraspinatus or infraspinatus tendons contacting the posterosuperior labrum.
• This contact can lead to rotator cuff tendon and labrum damage.

Purpose of the Study:

• To determine if this contact occurs physiologically in shoulders without rotator cuff tears.
• Investigate the relationship between arm-cocking movements and internal impingement.

Main Methods:

• Evaluated 100 shoulders in 100 patients during surgery.
• Assessed rotator cuff and labrum contact in 90° abduction/90° external rotation (90/90) and 140° abduction/maximal external rotation (140/Max) positions.

Main Results:

• Contact was observed in 69% of patients in the 90/90 position and 94% in the 140/Max position.
• A correlation was found between rotator cuff/labrum lesions and regular arm-cocking movements (p=0.035).

Conclusions:

• Contact between the rotator cuff underside and posterosuperior labrum is a normal physiological occurrence.
• Repetitive arm-cocking movements may cause macroscopic lesions in the rotator cuff and posterosuperior labrum.