Grip and shoulder strength correlation with validated outcome instruments in patients with rotator cuff tears

The ability to better define preoperatively the extent of rotator cuff (RC) dysfunction is desired. The study’s purpose was to prospectively examine the relationships between absolute and percentage loss (affected compared to unaffected) of grip and shoulder strength, and RC dysfunction. Forty-seven consecutive patients with proven RC tears participated in this study. Prior to surgery, bilateral strengths of grip, shoulder abduction, and shoulder external rotation (ER) were measured with a handheld dynamometer, and subjective outcome measures were gathered. RC tear size was determined via arthroscopy. Patient-reported outcomes were gathered on the day of the examination or via e-mail following initial evaluation. Descriptive statistics, difference analysis, and correlation coefficients (reported as either direct or negative) were used to analyze data. Grip, abduction and ER strengths, and percentage loss of grip, abduction, and ER strengths (percentage loss affected vs. unaffected), and tear size were analyzed in relation to all of the scores on selected subjective outcome measurement tools. The P value was set at .05. Fair direct correlations were found between grip strength and the Veterans RAND 12-Item Health Survey (VR-12) mental health scores, ER strength and Simple Shoulder Test (SST), abduction strength, and both the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) function score and SST score. Abduction and ER strengths were also found to possess a fair direct correlation. Fair negative correlations were found between the ASES function score and each of the following: percentage loss of abduction strength, percentage loss of ER strength, and tear size in centimeters. Another fair negative correlation was found between the Single Assessment Numerical Evaluation (SANE) score and tear size in centimeters. Our findings suggest that as shoulder strength decreases, ipsilateral shoulder RC dysfunction increases. Grip strength was not related to shoulder RC dysfunction. Grip strength was not found to correlate with RC tears. Those with decreased abduction and ER strengths and low ASES scores should be considered more likely to have an RC tear.