Osteochondral Allografts: The Future of Treatment of Joint Injuries

Priya Sagar

Abstract

As joint and bone injuries become more frequent, especially amongst younger patients living highly active lifestyles, surgery has often been used to repair damage of the articular cartilage of these areas. The increased risk of osteoarthritis that arises from articular cartilage injuries makes it is imperative to find efficient methods to treat such injuries. Arthroplasties, which replace the joint, often with a metal or plastic implant, have been used commonly as a form of treatment for articular cartilage damage. However, this treatment is limited to smaller osteoarticular injuries. Osteochondral allografts involve the replacement of a patient’s joint with the joint of a donor, and has shown promise in effectively treating articular cartilage injuries.

Articular cartilage is vital for the proper, painless functioning of the joints. This is especially true for hip joints and knee joints, where damage to articular cartilage may result in multiple surgeries to repair the joints as well as early-onset osteoarthritis [1][2]. Located at the ends of the joints, the tissue serves as a cushion for the joints and allows for joints to move without excessive pain by reducing any friction produced by the joints.

Articular cartilage is composed of water, chondrocytes (cells embedded within the cartilage which maintain balance within the joint), and proteoglycans (compounds that consist of proteins present in connective tissue)[3]. Proteoglycans bind with water to allow the cartilage to swell to be firm enough to protect the joint, and a type of proteoglycan known as nonaggregated proteoglycans bind with collagen. Injuries to the joints often disrupt this composition, thus weakening or damaging the articular cartilage[3]. Since articular cartilage is surrounded by few blood vessels, therefore classifying it as avascular, it may take an extensive time to heal on its own. Even worse, patients with articular cartilage damage are younger than before, posing a unique predicament to physicians and surgeons.

Traditionally, those with damaged articular cartilage would receive implants made of metal or plastic. These implants would be surgically installed, known as arthroplasty. However, as patients for the procedure tend to be younger currently, arthroplasty may not be an ideal treatment to resolve the issue. For instance, it is more ideal for the a younger patient’s own bone and cartilage to remain preserved for better functioning, which arthroplasty may not account for[1]. In addition, arthroplasties are ideal for situations where smaller regions of the cartilage are damaged. Thus, they may be ineffective for lesions with an area greater than 4 cm2[1]. Other procedures include an osteochondral autograft (or osteochondral autologous transplantation), in which cartilage or bone is taken from another region of the patient’s body and is used to replace the damaged articular cartilage. This method encounters the same problem as arthroplasties: it is ideal for smaller injuries between 1 and 2 cm2 in area[4].

Diagram of a damaged articular cartilage in the knee, indicated by the irregularly shaped tan region on the bone.

Osteochondral allografts, abbreviated to OCA, are ideal for larger lesions of articular cartilage and still allow for the preservation of native cartilage and tissue of patients, making the procedure suitable for younger patients. A donated articular cartilage sample is inserted into the joint of the patient with the damaged articular cartilage. Throughout the surgical procedure, measurements are taken of the damaged cartilage, the size of the incision made to insert the donated cartilage, and the size of the donated cartilage itself. Similar to plugging in a hole where necessary, the donated articular cartilage is “plugged” into the hole where the patient’s damaged cartilage was just removed [1].

A diagram displaying how the donated tissue is “plugged” into the patient once the damaged cartilage has been removed during an OCA procedure.

OCAs are not perfect, however. Donated cartilage must be meticulously chosen to fit the patient and avoid any form of rejection from the patient receiving the donated cartilage. Moreover, since the cartilage must be preserved for its proper usage, surgeons must insert the donated tissue within 28 days of harvest, thus imposing a time constraint on surgeries for this procedure [3]. As OCAs are used when other forms of treatment have failed to improve the patient’s condition (known as a salvage procedure), any surgeries on the region where the OCA had been performed increase in difficulty for surgeons[3].

However, compared to arthroplasties and autografts, OCAs have been observed to work more effectively on younger patients and athletes. Its ability to work on larger lesions make them ideal for many patients. Although it is certainly far from a perfect procedure, osteochondral allografts have shown promise to many patients afflicted by joint injuries, and improvements to account for its flaws may make it suitable for even more patients in the future.

References

[1] Cinque, Mark E., Chahla, Jorge, Hussain, Zaamin B., Kennedy, Nicholas I., LaPrade, Robert F., Moatshe, Gilbert, Vinagre, Gustavo. (25/09/2017). Osteochondral Allograft Transplants for Large Trochlear Defects. The Journal of Arthroscopic and Related Surgery. https://www.arthroscopytechniques.org/article/S2212-6287(17)30193-7/fulltext. Retrieved: September 13, 2018.

[2] Chahla, Jorge, Cruz, Raphael S., Dean, Chase S., LaPrade, Robert F.. (15/02/2016). Fresh Osteochondral Allograft Transplantation for Treatment of Articular Cartilage Defects of the Knee. Arthroscopy Techniques. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4886188/. Retrieved: September 13, 2018.

[3] Belton, Matthew E., Vidal, Armando F., Wydra, Frank B., York, Phillip J.. (20/06/2017). Joint Preservation Techniques in Orthopaedic Surgery. Sports Health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5665111/. Retrieved: September 13, 2018.

{4] Bugbee, William D., Early, Samuel A., McCauley, Julie C., Tircio, Luis E.P. (03/10/2017). Fresh Osteochondral Allograft Transplantation for Spontaneous Osteonecrosis of the Knee: A Case Series. Orthopaedic Journal of Sports Medicine. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5665111/. Retrieved: September 13, 2018.