Rotator cuff strength in recurrent anterior shoulder instability

Area of Science:

• Orthopedics
• Sports Medicine
• Biomechanics

Background:

• Rotator cuff muscles are crucial for glenohumeral joint stability.
• The role of rotator cuff strength in recurrent anterior instability is not well understood.
• This study investigates the link between rotator cuff muscle strength and glenohumeral joint instability in non-surgically treated patients.

Purpose of the Study:

• To analyze the association between isokinetic internal rotator and external rotator muscle strength and glenohumeral joint instability.
• To compare strength in patients with recurrent anterior instability to healthy controls.
• To determine the influence of hand dominance on strength differences.

Main Methods:

• Thirty-seven patients with recurrent anterior shoulder dislocation and eleven healthy controls were studied.
• Isokinetic strength of internal and external rotators was measured using a Con-Trex dynamometer at various speeds (180°/s, 120°/s, 60°/s).
• Peak torque normalized to body weight and the external rotator to internal rotator ratio were calculated; side-to-side and control group comparisons were performed.

Main Results:

• Significant side-to-side differences in rotator cuff strength were observed in patients with instability (p < 0.05).
• Patients with instability showed lower strength in the pathological shoulder compared to controls at 180°/s and 120°/s (p < 0.05).
• Strength deficits were more pronounced in the non-dominant arm and less so in the dominant arm; no association was found between instability and the external rotator to internal rotator ratio.

Conclusions:

• Weakness in internal and external rotator muscles is associated with recurrent anterior glenohumeral joint instability.
• The degree of strength difference is influenced by hand dominance.
• Further research is needed to establish causality between rotator cuff weakness and instability.