I went with my sister-in-law (Mary) to her appointment with the orthopedic surgeon about her new hip replacement coming up. She will get a cementless type of implant. They showed us what it will look like. There were also photographs in the office of a goop around the implant. The surgeon said it was a special bone producing gel. How does that work? Should we ask if Mary will get that, too?
Cementless implants are press-fitted into the bone. They are held in place by the porous (roughened) surface of the implant next to the bone. During the natural process of healing, the inflammatory process brings new blood cells to the surgical site and the stem cells form new bone cells to fill in and around the implant. Growth factors speed up the whole process.
The gel you saw is considered osteoinductive which means it fosters bone growth. It contains proteins that act as growth factors to stimulate bone growth. This new gel is made up of bone chips, platelet-rich plasma (the growth factors), and bone marrow. Bone marrow contains stem cells that can form into any other cell, including new blood and bone cells needed to form new bone tissue.
The gel is made up of the patient's own bone cells, bone marrow, and growth factors. When the old, arthritic hip joint is taken out, the bone marrow from inside the upper shaft of the femur is collected. The top of the femur and the hip socket (also removed in preparation for the new implant) are ground up and used as bone stock.
The bone is rich in bone cells that promote bone growth. The bone stock also contains morphogenic protein, another type of growth factor. Once the gel is all mixed up, it is smeared all over the implant socket and stem before inserting these into the patient's hip.
With the osteoinductive gel, the hope is that the process will not only be faster, but also provide joint stability sooner. That could mean patients can get back to full function as soon as possible with fewer complications.
Wolfram Thomas, MD, et al. Osteoinductive Gel in Cementless Hip Joint Replacement: A Randomized Prospective Study. In Current Orthopaedic Practice. November/December 2009. Vol. 20. No. 6. Pp. 655-659.
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