Biological meniscus and cartilage repair & transplantation

Nowadays, the golden rule for addressing a partial or total meniscus tear is to replace it with an allograft, i.e. an entire new donor meniscus or a part thereof.

In earlier times, when the vital role of menisci in normal knee function was unknown, menisci being considered as mere insignificant functional structures, the standard invasive treatment was meniscectomy.

However, both total meniscectomy and the subsequent partial meniscectomy were found to have a disastrous effect on the joint over time, and therefore they have been abandoned altogether.

This is so because these crescent-shaped cartilaginous discs are ultimately crucial for the balancing and distribution of compressive forces during movement, as well as for the lubrication and stabilization of the joint.

After their contribution to normal knee function was appreciated, several studies were conducted and efforts were made to develop therapeutic methods, in particular after the long-term consequences of meniscectomy were discovered, which require that the meniscus be preserved where possible.

What can cause a partial or total meniscus tear?

This damage can occur at any age, regardless of one’s profession.

Sometimes it happens due to meniscus deterioration caused by old age or due to excessive use or trauma.

The incidence is higher in people aged above 40, males in particular.

The medial meniscus is affected more often than the lateral meniscus.

Intense and continuous activity is a risk factor, acute tears happening more often during exercise.

What are the requirements for allograft transplantation?

Allograft transplantation is a technique used to save an aching knee that suffers from meniscus tear, which has a good clinical outcome, as a properly placed graft tends to protect the cartilage and is capable of distributing the load and absorbing the shocks on the joint.

However, a key requirement is that this complex operation is carried out by experienced and duly trained surgeons.

The operation takes about 2 to 2½ hours and requires total anesthesia. Typically, the patient needs not spend the night in the hospital.

Despite the presence of likely risks, just like in any operation, these risks are under no circumstances posed by the graft.

This is true thanks to the exclusion of any donors who belong, while alive, to high risk groups, have suffered certain infections and have tested positive for bacteria, fungi and viruses, such as HPV and HIV.

The estimated likelihood of using an infected graft is 1 in 1.6 million!

It is only after carrying out appropriate testing that the meniscus is collected, sterilized and frozen until used.

Moreover, there is no need for donor-recipient matching, neither is there a risk of the graft being rejected as there are no living cells to be attacked by the recipient’s immune system.

The only requirement is to match the size of the meniscus.

What is the benefit of allogeneic graft transplantation?

After the operation, the contact surface between the femur cartilage and the tibia cartilage in the patient is larger, which prevents friction between the two bones, thus reducing pain and enhancing joint functionality.

Most importantly, though, it puts off the need for total knee replacement.

There has been an estimated 85% success rate in five years, thus offering patients a number of years of independence and quality life.

However, it is important that one decides to be transplanted early enough, before the joint cartilage damage renders transplantation impossible or decreases the chances of a favorable prognosis.

Other requirements for transplantation, except for the loss of the meniscus and the resulting symptoms, include the patient’s young age, the existence of early degenerative changes in the knee due to the damage —without any advanced lesions, however— the stability and proper alignment of the joint, as well as that any joint cartilage damage is limited in thickness.

This is so because meniscal transplantation does not reverse the joint cartilage damage already caused in the knee.

In the event of concurrent advanced cartilage damage, it has to be treated surgically by the use of cartilage transplantation.

Where the extent of the lesion is limited, the surgeon obtains a graft from a part of the joint that carries no load and adapts it to the damaged area.

Where extensive damage prevents the obtaining of an autograft, an allograft is implanted after following the same procedure as that used for meniscus, to prevent infection.

The advantage of an allograft is increased precision in terms of shape and size as it is cut by the surgeon.

Naturally, cartilage transplantation can be carried out as an independent operation, i.e. if the meniscus is healthy.

Generally, this method for addressing the pain and the resulting dysfunction is new, but according to evidence so far, it is the future in worn cartilage replacement, which allows for maintaining a high level of activity after the operation.

Postoperative rehabilitation takes patience and perseverance.

Initially, the patient will have to use a walking aid (crutches) and then physiotherapy will be needed to ensure full recovery.

BIOLOGICAL FACTORS

Recently there has been an increasing interest in the use of orthobiologics, such as platelet rich plasma (PRP) and mesenchymal stem cells (MSCs), in an effort to utilize their healing effect on articular and meniscal tissue.

These are conservative methods for restoring worn cartilage, which have been proved to be very effective in boosting one’s physical ability to repair and regenerate musculoskeletal tissue, and therefore heal injured cartilage, muscles, tendons and linkages.

The so-called orthobiologics are autologous biomaterials, i.e. substances occurring naturally in the body.

Their use has been developed to fill the gap in the treatment of patients suffering from degenerative meniscus tears who have not responded to conservative treatment and are not eligible for meniscal replacement.

The core benefits for patients receiving these orthobiologic conservative treatments include minimizing the impact of injury or degenerative disease and ensuring faster recovery.

PLATELET RICH PLASMA (PRP)

Platelet rich plasma is an autologous blood fraction with a high platelet concentration.

Its popularity as a therapy for the management of musculoskeletal trauma has been on the rise, as the indications for dealing with certain knee disorders are very positive.

It is a simple treatment which typically lasts for two hours, requires no anesthesia and has a very short rehabilitation period.

MESENCHYMAL STEM CELLS

Μesenchymal stem cells are a subset of stem cells obtained from the bone marrow, periosteum, trabecular bone, fatty tissue or congenital teeth.

Of all types of cells, these have a better capacity of accelerating healing.

This is due to the fact that, when they are transferred to the injured area, they can develop into the type of cells that are needed to help correct the damage done.

Their clinical applications in regenerative medicine have been studied in recent years due to their capacity of taking part in various cellular processes.

It has been established by now that cellular treatment has a beneficial effect on the healing of a torn meniscus.

It is provenly a minimally invasive option for patients which requires no hospital stay and helps avoid the long rehabilitation periods typically required after an operation and its long-term effect on the knee.