Arthroscopic Rotator Cuff Repair with UC-MSCs for Large to Massive Tears

"Biological: Allogenic Umbilical Cord - derived Mesenchymal Stem Cell~1. Injection dosage and volume of the study drugs:~ * Low dose: 2.5X10 cells/0.5mL~2. Number of injections: Only once during the study period~3. Device: Ultrasound~4. Injection technique: Injection into the lesion by investigator~Biological: Allogenic Umbilical Cord - derived Mesenchymal Stem Cell~1. Injection dosage and volume of the study drugs:~ \- High dose: 5X10 cells/1mL~2. Number of injections: Only once during the study period~3. Device: Ultrasound~4. Injection technique: Injection into the lesion by investigator"