Abstract
AimTo investigate if there is a correlation between grip strength (GS) and rotator cuff (RC) strength in patients with atraumatic shoulder instability (ASI) and to compare the relationship between these two measures with that previously published for a healthy population. Moreover, to determine if testing GS could be incorporated as a surrogate clinical assessment for RC strength in these patients.MethodsA total of 20 subjects with ASI were included. Out of the 20 patients, eight presented with bilateral instability, which constituted a total of 28 atraumatic unstable shoulders (N = 28). GS was measured using a Jamar hand-dynamometer. External rotation (ER) and internal rotation (IR) strength was tested in inner and outer ranges using a hand-held dynamometer (HHD). Pearson’s correlation test was computed to investigate the relationship. Multiple linear regression was conducted to predict GS based on RC strength.ResultsSignificant and strong positive correlations were found between GS and inner-range IR (r = 0.764, P < 0.001), inner-range ER (r = 0.611, P = 0.001), outer-range IR (r = 0.817, P < 0.001), and outer-range ER (r = 0.736, P < 0.001). A significant regression equation was found (F (4, 23) = 13.254, P < 0.001), with an R2 of 0.697 indicating that RC strength explained 69.7% of the variance in GS.ConclusionsThe results support the hypothesis showing that GS is strongly associated with RC strength in ASI patients. The simplicity of handgrip testing allows it to be used in clinical scenarios where sophisticated assessment tools are not available. GS is a convenient means to monitor patient progress during shoulder rehabilitation programs.
Highlights
Rotator cuff (RC) muscles are considered to be the key dynamic muscles in shoulder stabilization since they contribute significantly to shoulder stability in a number of different ways [1]
The purpose of this study was to investigate if there is a correlation between grip strength and rotator cuff function in patients with atraumatic shoulder instability and to compare the relationship between these two measures with that previously published for a healthy population
Descriptive statistics A total of 20 patients with atraumatic shoulder instability participated in this study
Summary
Rotator cuff (RC) muscles (supraspinatus, infraspinatus, subscapularis, and teres minor) are considered to be the key dynamic muscles in shoulder stabilization since they contribute significantly to shoulder stability in a number of different ways [1]. They work as a dynamic stabilizer and as static stabilizers because of their orientation and location around the shoulder joint [2]. They allow a wide range of shoulder movement through rotational moments [3]. Rotator cuff muscles form attachments with the joint capsule, which contribute to the increased capsular tension during shoulder active range of motion [2] further stabilizing the joint.
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