Patients enrolled in the ADSC cohort will undergo the following procedures: arthroscopic resection of approximately 5cc of the infrapatellar fat pad using a motorized shaver (standard use in arthroscopy). Fat will be collected in a sterile Aquavage Collection System (AV1200, MD Resources, Livermore, CA) and kept sealed until processing. Fat will then immediately be processed in the Harvest Adiprep System to separate a population of ADSCs. This system concentrates an average of 5 x 105 cells/ml. All specimens will be processed using routine sterile procedures within the operating room; cells destined for implantation will not leave the operating room. Concurrently, patients will undergo arthroscopy and similar preparation of the chondral defect and removal of the calcified cartilage layer. However, no puncture of the subchondral bone will be performed. A layer of fibrin glue (Tisseel) will be placed at the base of the defect to seal off any bleeding from the subchondral plate followed by the application of the acellular dermal matrix (Allopatch HD, MTF Corporation, Edison, NJ, USA)and ADSCs. An additional layer of Tisseel will then be applied over the cells and matrix. No additional fixation will be applied. The matrix and cells will be recessed below the articular surface by an average of 1mm.
They will then complete outcome questionnaires and additional MRI scans at 6, 12, and 24 months post-operatively.
