Bone Marrow AspirationCellular Content of Bone Marrow Aspiration, Comparison

The goal of this observational clinical trial is to determine whether the posterior superior iliac spine of the hip or the humerus of the arm will produce larger amounts of bone marrow when harvested during surgery. Also, the secondary goal of this study is to determine the effects of the patient's position on the quantity of cells harvested from the hip, namely lying on back (prone) vs. lying on side (lateral decubitus). The main questions it aims to answer are:

• Will the hip or the arm have more bone marrow extracted?
• Does a patient lying in lateral decubitus position produce more bone marrow than lying in the prone position?

Participants that are to undergo rotator-cuff repair are eligible for this study. During the participant's repair, bone marrow will be extracted from the arm and from the hip. Half of the eligible participants will have bone marrow extracted from the hip while lying on their side, while the other half will have bone marrow extracted from the hip while lying on their back. Researchers will compare the results from both extraction sites on each patient, as well as compare results of the two patient position groups.