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Rotator cuff (RC) tear is a common cause of shoulder pain and shoulder dysfunctions, especially in elderly population. Four RC muscles coordinate shoulder movement and stability, including supraspinatus (SSp), infraspinatus (ISp), subscapularis and teres minor. Among this muscles the SSp and ISp muscle which are predominant muscle predispoed to tear.
The RC tears prevalence is high (20%) in the general population and increases with age (over 50% in the population above 65 years). The type I collagen, type III collagen and elastin are major composition of extracellular matrix of the tendon. Strength and viscoelasticity of tendon are associated with collagen and elastin, respectively, however the denaturation of collagen is associated with rotator cuff tears. Murata et al (2014) in an experimental study evaluated the age-related changes in collagen of the RC in rat model. Their results showed that the mRNA expression of Col1a1 and Col3a1 was reduced during aging and these changes can increase the chance of RC tear.
The study of da Rocha Motta et al. (2015) showed that there was a genetic evidence associated with RC disease. The number of gene pathways was altered in RC tears and polymorphisms in these genes could lead to an extended tendon degeneration process. Their results showed that DEFB1, ESRRB, FGF3, FGF10, and FGFR1 genes had specified role of in RC disease which explained why subsets of patients were more susceptible to this type of diseases. They suggested that these variants could provide a clue for therapeutic targets.
In RC tears, the dynamic stabilization of the shoulder is lost. The tear pathology and contribution of each RC muscle is not fully understood. However, Henseler et al. (2015) showed that infraspinatus atrophy had the strongest contribution to RC tear pathologies according to the magnetic resonance imaging with arthrography (MRA). This suggests a pivotal role for the infraspinatus in preventing shoulder disability.
The arthroscopic techniques are developed as the gold standard surgical repair strategies for RC Tears. There is not strong agreement between orthopaedic surgeons for the best type of Arthroscopic repair of RC, single-row or double-row fixation. According to recent literature, Double row fixation can be more effective. In a meta- analysis study, Xu Et al. (2014) showed that double-row RC repair techniques, compared with single-row repair techniques, had a significantly better results including higher American Shoulder and Elbow Surgeons (ASES) score, lower re-tear rate and greater range of motion of internal rotation. Especially in cases with RC tears with a size of >30 mm, the double-row technique was the best method for repair.
According to the literature, patients with RC tears often have some changes in injured area such as substantial weakness, fibrosis, inflammation, and fat accumulation. Prevention of these pathologic processes can have positive effects on clinical outcomes. Davis et al (2015) in an experimental study showed that Simvastatin, as an anti-inflammatory and antifibrotic drug, could partially protect muscles from the weakness in rats with chronic RC tear. Also, fibrosis was markedly decreased in simvastatin-treated animals. However, more studies are necessary to show that statin medication can potentially improve outcomes for patients with RC tears.
Local analgesic injections are commonly used for pain relief after shoulder surgery. In a prospective clinical trial, Lee et al. (2015) compared glenohumeral, subacromial, and a combination of glenohumeral and subacromial injections after arthroscopic rotator cuff repair. They results showed that the injection of local analgesics after arthroscopic RC arthroscopic repair could relieve pain after surgery regardless of the injection area.