Background
musculoskeletal complaint, Shoulder pain, SIS, anterolateral shoulder pain
SUBACROMIAL IMPINGEMENT SYNDROME, SUBACROMIAL IMPINGEMENT, PATHOGENESIS
Shoulder pain is the third leading musculoskeletal complaint with subacromial impingement syndrome (SIS), accounting for 44–65% of all shoulder complaints, resulting in functional limitation and disability [SIS is mechanical compression of the rotator cuff tendons, long head of the biceps and subacromial bursae under the coracoacromial arch. [SIS is diagnosed clinically as localized anterolateral shoulder pain lasting longer than 2 weeks, exacerbated by arm elevation, above-head movement and lying on the affected side [There is no consensus regarding effective treatment for SIS. This lack of consensus might be related to a proposed multifactorial pathogenesis [The regenerative and immunomodulatory properties of PRP depend on the hyperphysiological content of autologous growth factors released after platelet activation, including platelet-derived, transforming, fibroblast, endothelial, connective tissue, vascular endothelial and hepatocyte growth factors (HGFs), which stimulate epithelial cells and fibroblasts, resulting in new collagen and elastin formation [Significant variability exists among different PRP preparations, whether commercially available or non-commercial double-centrifugation techniques, with variation in the number of platelets and concentration of growth factors. The lack of standardization for an ideal number of platelets has a definite influence on clinical results [A new patented blood product named lyophilized growth factors (L-GF) [The aim of this study was to evaluate the efficacy of injection of platelet-derived L-GF in the treatment of subacromial impingement.