Sports Medicine Research: In the Lab & In the Field: Joint Mechanics and Strength Still Altered After Rotator Cuff Repair (Sports Med Res)
Friday, September 16, 2011

Joint Mechanics and Strength Still Altered After Rotator Cuff Repair

In Vivo Shoulder Function After Surgical Repair of a Torn Rotator Cuff: Glenohumeral Joint Mechanics, Shoulder Strength, Clinical Outcomes, and Their Interaction.

Bey MJ, Peltz CD, Ciarelli K, Kline SK, Divine GW, van Holsbeeck M, Muh S, Kolowich PA, Lock TR, Moutzouros V. Am J Sports Med. 2011 Jul 7. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/21737834


Rotator cuff tears occur frequently in both overhead athletes and the elderly. Shoulder arthroscopy is the current recommendation to repair rotator cuff tears; however the effect of surgical intervention on several functional parameters has not been examined in depth. Therefore, Bey et al. examined 21 patients with supraspinatus tears, and 35 control participants. Each participant was measured bilaterally for glenohumeral joint kinematics and joint contact patterns during coronal-plane abduction using biplane radiographs. Isometric shoulder strength (abduction, forward flexion, IR, & ER) and patient reported outcomes (WORC Index) were tested in the rotator cuff group at 3, 12, and 24 months post repair. The same outcomes were only tested once for the control group. Ultrasound images were also collected at the 24 month time point to assess rotator cuff integrity. They found that the shoulders of the rotator cuff tear group was positioned more superior during abduction, compared to the contralateral shoulder and control group. This remained over the 24 months. Shoulder strength was found to improve overtime; however deficits remained at 24 months compared to contralateral shoulder. Patient reported outcomes also improved overtime and correlated with shoulder strength. Twenty of the 21 cuff repairs remained intact at the 24 month time point based on the ultrasound data.

This study was one of the first to follow rotator cuff tear patients overtime and evaluate several levels of function. Rotator cuff repairs have been performed for several decades; however the effectiveness of restoring normal joint mechanics and strength has not clearly been defined. It is interesting that the surgery is unable to restore normal arthrokinematics. Previous research has suggested a link between rotator cuff tears and shoulder osteoarthritis due to abnormal arthrokinematics. Without proper restoration of joint kinematics the patients may still be at risk for shoulder osteoarthritis. In addition, shoulder strength improved but was still decreased at 24 months post surgery. Strength was also correlated with patient reported outcomes. This provides further support for the already common philosophy that strength is needed for function. As clinicians this information can be helpful to identify areas of rehabilitation that can be improved. Superior positioning of the humeral head may suggest that the repaired supraspinatus is no longer acting as a humeral head depressor. The upper portion of the subscapularis has been demonstrated as an effective humeral head depressor and rehabilitation exercises may need to be designed to improve this function. Shoulder strength exercises may need to be emphasize more due to remaining deficits at 24 months. Muscle inhibition may still be present due to previous pain and the use of electrical stimulation may be beneficial in the shoulder similar to its use at the knee following ACL replacement. What do you think about these findings? Do you think this may help us to design more effective rehabilitation programs in the future?

Written by: Stephen Thomas
Reviewed by: Kyle Harris

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