Summary

Rotator Cuff Injuries, Muscle Strength Dynamometer, Arthroscopy

Abstract

Background

& Purpose:
The objective of rotator cuff repair is to restore the shoulder function including strength in the repaired rotator cuff muscles. Most patients experience improvements in pain and function after repair. Post operative improvements in shoulder strength have also been documented previously, mostly through routine clinical measures. Influence of shoulder position during shoulder strength measurements, instrumented measures of shoulder strength and improvements in different types of strength i.e.., isometric & isokinetic are not examined in a same group of patients. Also, the relationship between the improvements in strength measures and the improvements in functional outcomes of the shoulder has not been established. The present paper will report the relative influence of rotator cuff muscle strength in functional outcomes of arthroscopic rotator cuff repair.

Methodology

Patients with rotator cuff injuries, who were posted for arthroscopic rotator cuff repair were clinically assessed for preoperative range of motion. Isokinetic and isometric strength of the shoulder was assessed using a KINCOM dynamometer (Chattanooga group, Tennessee, USA). The shoulder position was in 45 degrees of abduction in the scapular plane and the strength of internal and external rotation was recorded in Newton meter (Nm). The isokinetic testing was done at speeds of 60 and 120 degrees/second and peak torque was calculated. The pre and postoperative strength values were compared with the functional outcome scores, CONSTANT and ASES score preoperatively and 6 months post operatively. Correlation analysis was done to explore the associations between rotator cuff strength and functional outcome measures.

Results

A total of 43 patients. 24 males and 19 females were enrolled in the study. 17 patients were lost to follow up. The data of 26 patients were used for the results and inferences. Postoperatively there was an average increase of 38 points in - the CONSTANT score (p >0.0001), and 53.8 points in – the ASES score (p>0.0001). Isometric strength in internal rotation increased on average by 24.69 Nm (p=0.0001) and external rotation by 18.49 Nm (p>0.0001). Isokinetic strength at speed of 60 degrees/s in internal rotation increased on average by 15.5 Nm (p=0.0001) and external rotation by 16.3 Nm (p>0.0001), and isokinetic strength at speed of 120 degrees/s in internal rotation by 16.2 Nm on average (p=0.0001) and external rotation by 15.6 Nm (p>0.0001). Correlation analyses of the data did not reveal any significant relationship between the improvements in the strength measures and the improvements in self-reported function.

Conclusion

Arthroscopic rotator cuff repair significantly improves the post-operative functional outcomes and shoulder muscle strength. However, the improvements in strength and the improvements in shoulder function are found to be not related