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.

This is a single site, comparative quantitative analysis study of the cellular characteristics of bone marrow aspirate from two extraction sites (PSIS and humerus) from patients undergoing standard-of-care arthroscopic rotator cuff repair surgery. 30 total patients will be recruited through the Andrews Institute physician practices. A recruitment flyer will be used to recruit participants. The flyer will be placed within physicians' offices and on social media platforms. Potential participants will be prescreened for inclusion and exclusion criteria through standard of care medical evaluations. Once a potential participant has agreed to be involved in the study, they will go through the described informed consent process. Patients meeting the inclusion criteria will have the study explained to them by one of the members of the research team, and they will be given an opportunity to participate if they are interested.

After the described screening and informed consent process have been completed, all participants will undergo standard-of-care arthroscopic rotator cuff repair surgery. During all surgeries, bone marrow will be aspirated from the PSIS and from the humerus. The first 15 participants will have bone marrow aspirated from the PSIS while in the prone position on the operating table. The final 15 participants will have bone marrow aspirated from the PSIS while in the lateral decubitus position on the operating table. Both cohorts will undergo humeral harvest intraoperatively in the lateral decubitus position. One mL of concentrated bone marrow aspirate (cBMA) from each harvest site from each surgery will be removed and sent to the AREF Regenerative Medicine Center (RMC) for analysis. The remaining cBMA will be used to augment the rotator cuff repair surgery.

Inclusion Criteria:

• 18-80 years of age
• Diagnosis of a rotator cuff tear requiring arthroscopic rotator cuff repair

Exclusion Criteria:

• Patients who require superior capsular reconstruction or revision rotator cuff repair
• Diabetes
• Immune Disorders
• Past medical history of a metastatic or other cancer which required chemotherapy/ radiation therapy
• Rheumatoid arthritis
• Is unable to comprehend the study documents or give informed consent

The focus demographic of this study is people within the ages of 18 and 80 that have been diagnoses with a rotator cuff tear and require reconstructive surgery.