Influence of aging on microvascular supply of the gluteus medius tendon.Introduction.Aging deeply influences several morphologic and functional features of the musculoskeletal structures.Previous studies have reported hypovascular zones in different tendons of the human body.However, there are no studies showing the relationship between aging and vascular supply of the gluteus medius tendon that may effect for increased vulnerability and healing potential.Purpose.The purpose of this cadaveric study was to assess the relationship between age and microvascular supply of three areas of the gluteus medius tendon utilizing a previously validated CD31 immunohistochemistry staining technique.Methods.Twenty-four fresh-frozen gluteus medius specimens were obtained through a postererolateral approach to the hip.The average age of donors was 47.3 years (range, 18 to 68 years).Each sample was divided in three portions (musculotendinous -MT, tendinous -T, and tendon-bone junction -TB).Hematoxilin&Eosin was utilized for qualitative structural analysis and then all samples were stained with CD31 immunohistochemistry for quantitative vessels per square millimeter.The comparison of the microvessel density between zones according to age was performed using an Analysis of Variance.To evaluate the relationship between microvessel supply and age a regression model with curvilinear estimation was used.Data were fitted to a quadratic model.