OATS stands for ‘osteochondral autograft transfer system,’ and the technique is very similar to mosaicplasty. In the OATS procedure the plugs are usually larger, and therefore only one or two plugs are needed to fill the area of cartilage damage. Because of this it does not take on the mosaic appearance, but the principle is the same.
The cartilage plugs are taken from areas of the knee that are non-weight-bearing areas. The hope is that the body will not miss this cartilage and it can be used where it is needed. Over time the holes left from where the plugs are taken will fill with bone and scar tissue.
The cartilage transfer procedure usually begins with an arthroscopic inspection of the knee. If there is an area of cartilage damage that is suitable to cartilage transfer, then the arthroscope is removed and an incision is made.
The first step is to prepare the area of damaged cartilage. A coring tool is used to make a perfectly round hole in the bone in the area of damage. This hole is sized to fit the plug.
The next step is to ‘harvest’ the plug of normal cartilage. The plug is taken with the underlying bone to fit into the hole that was prepared in the area of damage. The plug is just slightly larger than the hole so it will fit snugly into position.
The final step is to implant the harvested plugs into the hole that was created in the damaged area. Over time, the hope is that the implanted bone and cartilage will incorporate into its new environment.
Osteochondral Autograft Resurfacing/Mosaicplasty (OATS):
This treatment is primarily performed upon traumatic and chronic cartilage injury. Genetic disorders and osteoarthritis diseased chondrocytes potentially repeat the need for repair and continued deterioration. In OATS a plug of cells are moved from a non-load bearing area of bone and implanted into the damaged joint location. This procedure is best for small defects, <15-20mm in size, this is due to a limit in the number of harvest sites available.
This technique is only employed when the defects are small, cannot be treated with arthoscopic shaving or all “standard” treatments have been unsuccessful in ease of pain or increase in mobility.
Osteochondral Allograft Resurfacing/Mosaicplasty:
Osteochondral allograft resurfacing is a technique similar to traditional OATS except with the usage of cadaveric donor bone and cartilage. Until recently cadaveric transplantation has not been favored due to freshness of the grafts. However, with increased availability of grafts and with increased speed of donor matching, screening, and pathogen testing allografts are becoming more popular. This techinique employs the harvesting of one large bone and cartilage graft sutured to the injury/defective site along with the usage of fibrous glue. Although this technique has been used for the last 20 years within knees this practice has not been used in shoulder rehabilitation. With quicker, fresher donors we may see this technique employed in the future for severe shoulder trauma.
Autologous Chondrocyte Implantation/Transplantation (ACI or ACT):
ACI uses cell culture techniques in order to regenerated autologous chondrocytes then implant them into the site of damaged cartilage for adhesion and growth into a new joint cushion with all of the characteristics, morphology, and mechanical properties of the original tissue. This medical technology includes 5 basic steps:
- Chondrocyte biopsy : harvesting chondrocytes from a non-load bearing region of the bone
- Cell culturing : culturing the chondrocytes within a tissue culture setting in medium for up to 3 weeks
- Debridement of lesion : Debridement is the process of removing the damaged tissue site to reveal the healthy tissue cells beneath. This provides an excellent bed for cellular adhesion.
- YSurgical sewing of a flap : a flap sewn to the bone where the cartilage defect is located with create a pouch, usually a periosteum patch, for the cultured chondrocytes to be implanted into.
- Chondrocyte implantation : the cultured chondrocytes, around 12 million cells, are implanted under the previously sewn flap.