San Francisco Spine Surgeons

Thoracic
Procedures

Bone Graft

Bone graft is the material that is used to promote fusion or adjoining several vertebrae together. It can come from the patient himself (autograft) from another human (allograft) or another species, such as coral (xenograft). Also, a bone graft extender can be utilized, in which case it does not come from any living organism and is purely synthetic. Occasionally we utilize synthetic protein, which is a growth factor called bone morphogenetic protein (BMP-2 or INFUSE). It is a growth factor that promotes bone formation and has been successfully used in clinical application anywhere from skull to spine and extremities in the past decade or so. Depending on the procedure, the patient’s preferences, as well as the patient’s medical history (such as smoking, diabetes, and history of prior surgeries), the surgeon may choose one or more from the above. Another option for bone grafting involves drawing bone marrow from the iliac crest or vertebrae and hyperconcentrating it to yield concentrate of the stem cells. Derived from the patient himself, the stem cells are known as pluripotent, meaning that they are able to mature into multiple types of tissue. In the case of spine surgery, the goal is to promote maturation of the stem cells into bone-forming cells (osteocytes and osteoblasts). We have successfully utilized a bone marrow aspirate concentrate system (BMAC from Harvest) at St. Mary’s Spine Center for more than a year, with excellent clinical results. The main advantage of bone marrow aspirate concentrate is decreased morbidity of the bone graft harvest.

Fusion

Fusion is a tool that is utilized in spine surgery to join several vertebrae together. It is a common procedure that has been used since 1911 for treatment of a variety of spinal conditions, including degenerative conditions, deformity (scoliosis and kyphosis), infections, tumors, and congenital and inflammatory conditions. Historically, the fusion process frequently involves placing instrumentation into the spine—for example, pedicle screws in the thoracolumbar spine for an operation done for the back (posterior approach), lateral mass screws in the cervical spine (for posterior approach). The screws are anchors grabbing onto particular vertebrae, and they have to be connected to another anchor (another screw at a different level), usually with a small rod. The materials that are used for instrumentation in spine surgery are either pure commercial titanium (PCT), titanium alloy, stainless steel, or cobalt-chrome alloy. Depending on the situation, the surgeon may choose to utilize one or a combination of the above. Also, another frequently used biomaterial is PEEK (polyether ether ketone), which is used mostly for interbody devices such as ALIF, TLIF, PLIF, and XLIF cages. The screws connected by rods serve as an internal bracing or scaffold, which allows for the spine to fuse while maintaining the appropriate alignment. In essence, the function of the screws is temporarily holding the spine while the fusion takes its place. The fusion process—depending on the situation, age of the patient, and the number levels treated—can take anywhere from three to 24 months. In this sense, the function of the screws is usually temporary; however, in the majority of cases, after the fusion is completed, the screws stay in place. The majority of patients do not feel the screws (so-called hardware), and therefore additional operation to remove the screws is not warranted. However, very infrequently, some patients do feel the screws and require hardware removal.


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