Cartilage Repair
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THERAPY METHODS: Cartilage Implantation/Transplantation
Osteochondral Autograft Resurfacing/Mosaicplasty (OATS):
OATS is a therapy that utilizes the transplantation of an individuals own cartilage cells from one area to another. 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.
One of the major problems with OATS in shoulder injuries is with accessibility of the joint surface. 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. Also, the possibility of irritation of the joint after plug implantation may lead to inflammation and cellular scarring around the site that will decrease mobility in the recovering athlete.
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.
- Surgical 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.
First developed in Sweden by Dr. Lars Peterson this tissue engineered construct has proven its capabilities as a leading therapy for damaged cartilage tissue in all joints of the body. This joint repair techniques has proven itself through many clinical trials to be as effective if not superior to competitive therapies for knee injury rehabilitation. After 3 years of knee applications, Dr. Brian Sennet and Dr. Gerald Williams at the University of Pennsylvania Health System decided to try the new technology in the shoulder of a 22-year old woman. “The procedure had never been done before in a shoulder, but indications were good that we could provide her with a new healthy cartilage to last the rest of her lifetime,” said Dr. Sennet. Although the clinical analysis of shoulder ACI therapy is incomplete due to application infancy the medical field holds high result expectations based upon knee ACI trial analysis.
The implications of this technology allows athletes to replace the cartilage that was damaged or torn instead of smoothing the edges. Theoretically, the usage of ACI should prevent reccurance through increased stability of the shoulder with the proper cartilage structural formation. Although this technology has a longer healing/rehabilitation time the potential for a permanent repair of the injury for an athlete may be worth the wait. The increased healing time is to allow proper chondrocyte adherence and remodeling within the shoulder joint before strenuous activity.
Other Techniques (11):
• Carbon fiber Matrix Implant: Dr. G. Bently with an 8 year follow-up of satisfactory results in 77% of patients
• Periosteal and Perichondral Grafts: Sandelin et al. with 4 to 13 year follow-up of satisfactory results in 77% of patients, but reported deteriorating results with longer follow-up
Future Techniques:
• Cartilage matrix integration: Groups are integrating a scaffold for chondrocyte modelling during culturing that will be sutured into the joint. Such matrix designs are constructed of biomaterials such as Polylactide-co-Glycolide 1 , poly a -hydroxy acids (12), and poly-L-lactic acid (13). One of the complications associated with this scaffold method is lack of cellular binding. Groups such as Jeschke et al at Merk Biomaterials in Germany are attempting to add chemical and natural molecules, ex. RGD-peptides, that aid in cell adhesion (14).
• Growth Factor integration: With a growing understanding of the roles of growth factors in cellular manipulation specific molecules, ex. TGF- ß 1(15), there is an increase in research into the positive role growth factors may play in faster and more complete cartilage repair.
• Neocartilage is a product developed by Isto Technology, St. Louis, MO for usage as a cartilage implant. Production and marketing is to be overseen by Zimmer Inc. (2003). This technology utilizes the growth of neocartilage upon a bone culture site without a matrix, then implanted into any cartilage defect or damage site within the body. The technology is still being developed and is applying for FDA permission to begin clinical trials.
Created by: Blair Smith, Connie Lee, Daniel Solomon, Matthew Whitson and Stephanie Chang
Date last modified: 5/2/2004