The things orthopedic surgeons do to help heal damaged soft tissue and bone aren’t magical and they don’t come out of a hat somewhere. Treatment techniques applied to the human body (especially bones and the surrounding soft tissues) come from basic science research.
Some of the newer ideas (e.g., using stem cells and growth factors in healing) appear to have clinical application. But they have not produced the kind of positive results expected. The reason for this disconnect isn’t clear yet but it is something scientists are paying attention to and exploring further.
Here’s what we know so far. First, when it comes to using stem cell therapy during surgery to reattach a torn tendon to the bone, it looks like more research is needed. Before this treatment can be successful, scientists must find ways to signal stem cells to form the different cells needed at the insertion site. The goal is to find ways to use the patient’s own stem cells (rather than injecting donor stem cells from someone else) to form what is needed at the specific site of injury.
The results of studies so far suggest that this transition site from tendon to bone is very complex. In normal anatomy, joint stability, and movement, there is a load transfer from tendon to bone. Tendon and bone are two uniquely different types of tissue. One type of stem cell may not be enough to accomplish the task of restoring normal anatomy and function. Some cells must be formed of stiffer collagen fibers for bone while other cells remain soft and flexible to form tendons.
Efforts to use platelet-rich plasma (PRP) with its concentrated growth factors in tendon healing have not been as successful as was first predicted. When studies have compared patient healing, pain relief, function, and return-to-sports (with and without platelet-rich plasma (PRP)), there have not been consistently better results with the PRP.
Let’s turn our attention to research into gene technology. One application of spine deformity genetics is to treat idiopathic scoliosis (curvature of the spine of unknown cause). These studies have begun with fish. The goal is to develop a genetic test that could predict which children will develop this condition. The intended final outcome is to find ways to prevent idiopathic scoliosis or minimize its effects.
In the area of osteoarthritis research, researchers continue to focus on understanding what happens to the joint cartilage in the formation of osteoarthritis. Scientists have been able to identify key molecules involved in the process. Applying this information to mice has resulted in decreased osteoarthritis.
Right now, various types of growth factors are being tested in the treatment of joint pain from early osteoarthritic changes. It has been discovered that when osteogenic (bone) protein is combined with insulin-like growth factor joint regeneration is possible.
Other biologic therapies for the regeneration of tissue such as joint cartilage currently under investigation include autologous conditioned (blood) serum and bone marrow concentrate. Autologous refers to the body’s own cells. Any time autologous sources of cells can be used, it is considered an advantage both in terms of (lower) cost and (easy) administration.
What’s new in the area of joint replacements? Implant design continues to change and improve in an effort to get bone to stick to and form around the implant. For example, titanium mesh is being replaced by a product called tantalum.
The surface of a tantalum implant is more porous and seems to stimulate faster and more bone cells to form around the implant. Tantalum implants stand up better to high levels of friction and load. The focus of future studies will be to see if this formation and incorporation of bone (called oseointegration) will last over the long-term (10 to 20 plus years).
One other area of research of interest relates to damaged menisci (the C-shaped thick cartilage inside the knee). Right now a mild-to-moderate tear of the meniscus is repaired by stitching it back together and reattaching it to the bone.
Severely torn, frayed, or destroyed meniscus may have to be removed. Knee joints without the natural meniscus are at increased risk for early osteoarthritic changes. Even removal of part of the meniscus puts the knee at a biomechanical disadvantage.
There are two new ideas on the horizon for regenerating or replacing the meniscus. The first is called non-cell-seeded scaffolds. The idea is to encourage tissue regrowth by implanting an absorbable collagen mesh. Early studies show a definite advantage of using these scaffolds over removing the meniscus (a procedure called meniscectomy.
A second regenerative or biologic therapy being studied for repair of damaged menisci (plural form of meniscus) is called nondegradable synthetic menisci. This is like a meniscus replacement. A composite material that has been reinforced with lightweight polyethylene (plastic) fiber is being tried. It acts like a replacement for the meniscus that is removed. There is even a free-floating type of synthetic meniscus being tried.
In summary, a review of the new tissue regenerating options currently available or under study in orthopedics is provided in this article. This update covers a wide range of treatment options including stem cells, growth factors, platelet-rich plasma, meniscus repairs and replacements, joint replacements, and spine healing.
Developing orthopedic therapies are aimed at finding practical (clinical) ways to use discoveries made in the lab. Not all of the techniques described are available for use yet. The goal remains to translate or transfer basic science into the most effective clinical practice with the fewest side effects possible.