advanced medical technologies

Bone Morphogenetic Proteins (BMPs) are a group of growth factors and cytokines known for their ability to induce the formation of bone and cartilage. Dr. Marshal Urist initially discovered the activity of bone morphogenetic proteins in 1965. Since then, a number of types of BMP have been discovered; some have found therapeutic uses in areas such as spinal fusion. The use of BMPs adds from $6,000 to $10,000 to the cost of surgery, but this may be slight relative to the cost of repeated surgical interventions that may be needed if BMPs are not used.

BMPs are the only known proteins capable of inducing new bone formation. In some tests, they have demonstrated bone growth stimulation superior to that of autogenous bone graft. Two recombinant rhBMPs and associated carrier/delivery systems have received approval from the FDA: OP-1 (Stryker) and the InFUSE™ system (Medtronic). OP-1 consists of rh-BMP-7 and bovine collagen, which is reconstituted with saline to form a paste. The addition of carboxymethylcellulose forms a putty. The InFUSE™ system consists of rh-BMP-2 on an absorbable collagen sponge carrier. To date, rhBMP-2 has been approved by the FDA for the treatment of L5-S1 degenerative disease and used along with titanium spacers (cages) placed anteriorly. The anterior approach was chosen because it is the easiest way to shelter the BMP within the spine. By using a collagen sponge soaked with BMP and then placing it within the cage, there is decreased possibility that the material could seep into other places and form bone where it is not needed or wanted. Use of BMPs in spine fusion has significantly changed spinal fusion, in that there is less blood loss, less pain, shorter surgery times, shorter recovery times and frequently better fusion than when autologous grafts are harvested from the iliac crest.

OP-1 received on-label indications for use as an alternative to autograft in recalcitrant long bone non-unions where use of autograft is unfeasible and alternative treatments have failed; and for use as an alternative to autograft in compromised patients requiring revision posterolateral lumbar spinal fusion, for whom autologous bone and bone marrow harvest are not feasible or are not expected to promote fusion. Depending upon the insurance system, examples of compromising factors may include osteoporosis, smoking and diabetes.

A recent study by JR Dimar and colleagues (Spine. 2006; 31(22):2534-2539) involved 98 subjects randomized to receive either autologous bone graft or rhBMP-2 for single-level posterolateral fusions of the lumbar spine for degenerative disease. The authors report a higher fusion rate at 24 months (88% vs. 73%), faster surgical times and less blood loss for the rhBMP group. No other measures were significantly different, including Sf-36 scores, Oswestry Index measures, or pain index scores.
The InFUSE Bone Graft has received FDA approval when used in conjunction with 1 of 2 interbody fusion devices, in other words, with either the LT-Cage Lumbar Tapered Fusion Device or the Inter Fix RP Threaded Fusion Device, in spinal fusion procedures in skeletally mature patients with degenerative disc disease at 1 level from L2-S1, and for the treatment of acute, open fractures of the tibial shaft.

Both OP-1 and the InFUSE Bone Graft/LT-Cage Lumbar Tapered Fusion devices are contraindicated in patients who are pregnant, who may be allergic to any of the materials contained in the devices, who have an infection near the area of the surgical incision, who have had a tumor removed from the area of the implantation site or currently have a tumor in that area, or who are skeletally immature. These contraindications reflect continued concern that BMPs may cause unwanted bone growth in adolescents, whose skeletal systems are still growing, or in or near tumors or where tumors used to be.
 

bookmark to