The Effect of Amniotic Membrane Injection as An Addition to Physical Therapy in Patients With Rotator Cuff Tear

Rotator cuff tear (RCT) is a commonly seen pathology in shoulder disease, which causes significant disability in daily living and work. Based on a cohort study of a large population, the prevalence of rotator cuff full-thickness tear was 20.7%. More broadly, the prevalence of rotator cuff abnormalities increased with age and up to 62% in population more than 80 years old. The pathophysiology of RCT could be attributed to extrinsic factors such as impingement by surrounding tissue and intrinsic factor such as tendon degeneration. According to previous study using histochemical and immunocytochemical techniques, fibrocartilaginous metaplasia, decreasing vascularity and fibroblast numbers were found in rotator cuff tear. Besides, the inflammatory response diminished as the tear size increased.

The treatment of RCT includes surgery and non-operative treatment. The prognosis depends on the symptoms, tear size, chronicity and other structures involvement. Previous meta-analysis study reported that the effectiveness between surgery and conservative treatment is similar in treating RCT. Therefore, relative rest, oral medication, physical therapy and injection therapy were commonly used in first-line treatments. When treating shoulder pain with injection therapy, steroid was often used at first for short-term pain relief and anti-inflammation. However, the potential cytotoxic effect was found and could be harmful in tendon repair. To accelerative the healing process of soft tissue injury, regenerative injection become more popular and expectable over past few years. A meta-analysis study reported the positive long-term effect of prolotherapy and platelet-rich plasma (PRP). More recently, bone marrow concentrate (BMC) and amniotic membrane (AM) have been used in soft tissue repair and many clinical studies are processing.

In recent decades, PRP was widely used in soft tissue regeneration. Though many studies had discussed the effect of PRP injections on pain and shoulder function in RCT, the effectiveness remains controversial. Some newer scaffolds including bovine collagen and amnio-derived membranes were also applied to the RCT in recent years. The AM was separated from a donor's placenta, and is a non-immunogenic structure. In previous animal study, amniotic epithelial cells could produce transforming growth factor-β (TGF-β), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), transforming growth factor-α (TGF-α), keratinocyte growth factor and hepatocyte growth factor. AM was found having anti-inflammatory, antimicrobial, antiviral effect, regulatory effect on angiogenesis and anti-scarring effcts. AM was revealed a pluripotent tissue which makes it potential in regenerative medicine. In some case series research, positive results was reported in pain and shoulder function in rotator cuff tears.

To the best of our knowledge, there has been limited evidence of regenerative injection by AM in treating patients with rotator cuff tear. The aim of this study is to evaluate the effect of single injection of AM in addition to physical therapy on pain and shoulder function.