rhBMP-2 in Cervical Arthrodesis

Overview

This prospective study will investigate the use of recombinant human bone morphogenetic protein (rhBMP-2) in the current surgical standard of care for cervical spine pathology. Specifically, the outcomes of three forms of cervical fusion will be investigated: 1. Anterior cervical fusion with rhBMP-2, allograft corticocancellous bone as an interbody device, and anterior cervical plate fixation. 2. Posterior cervical fusion with rhBMP-2, local bone graft, with or without posterior screw fixation. 3. A combination of the previous two approaches: a combined anterior-posterior cervical fusion with rhBMP-2.

SURGICAL TECHNIQUES 1. Anterior cervical fusion The technique of anterior cervical discectomy and arthrodesis of the spine has been previously described by Smith-Robinson (ref) and is an accepted technique for anterior cervical fusion. Upon completion of adequate decompression, a gentle distraction maneuver may be performed by using either Caspar distraction pins or an interbody spreading device, taking care to avoid injury to the endplates. The endplates are then prepared with the use of a rasp or high speed burr taken to both superior and inferior endplates to remove the cartilagenous material and identify the bony endplate. Once hemostasis is obtained, the appropriate size allograft implant is chosen. That implant is then defrosted and brought into the surgical field. Concurrently, rhBMP-2 ((INFUSE®) Medtronic, Inc. Minneapolis, MN) has been reconstituted with sterile water, placed on an absorbable (type I bovine) collage sponge (ACS), cut to deliver the appropriate dose to each spinal level and is on the field as well. The partial BMP/ACS sponge is inserted into each disc space level, posterior to the structural implant. The dosage of rhBMP-2 used is approximately 0.525 mg per disc level or interbody space treated. The interbody device utilized is LifeNet Health's VertiGraft® VG2®. In the case of these allograft intervertebral implants, product safety and efficacy has been validated and patented by LifeNet Health using both an Allowash® and Allowash XG® technology. This is an intensive decontamination, disinfection and scrubbing regimen to remove and inactivate both viruses and bacteria which may be present from the donor harvesting process. The Allowash® process removes virtually all cellular elements of the bone thereby providing an additional line of defense against infectious disease. The second step consists of terminal sterilization of the cortico-cancellous allograft tissue. These processes have been validated and render the tissue sterile without compromising either the biomechanical or biochemical properties of allograft tissue intended for spinal applications. Plate fixation with the Atlantis® Cervical Plate (Medtronic, Inc. Minneapolis, MN) is carried out by serially drilling each of the screw holes and placing the appropriate length (3.5 x 14-15 mm) screw into each of the holes. The locking screw mechanism on the plate is then secured and a lateral cervical radiograph is called for to confirm appropriate levels and instrumentation placement. A medium Hemovac drain is placed in the anterior prevertebral space and brought out through a separate stab incision. Routine closure is then carried out. 2. Posterior Cervical Arthrodesis A longitudinal incision is made in the midline of the posterior neck, directly over the involved spinal level(s). The fascia and muscle are gently divided, exposing the spinous processes and lamina. An x-ray is obtained to confirm the appropriate spinal levels to be fused. A laminectomy and foraminotomy can be performed if necessary. Two (3.5 mm x 14mm) cortical screws ((Vertex (TM) Medtronic, Inc. Minneapolis, MN) are affixed to each lateral mass in the method previous described by Magerl (ref) and connected with a titanium rod on each side of the spine. The bony surfaces and facet joints are then decorticated. One sponge of the BMP/ACS product is placed over the decorticated bone surfaces on each side. The bone removed during the decompresion laminectomy is morsellized and placed in and around the facet joints. The amount of rh-BMP-2 used will be a total of 2.1 mg placed bilaterally, to a total of 4.2mg. 3. Combined Anterior-Posterior Cervical Arthrodesis This surgical procedure combines a posterior cervical decompression and fusion with an anterior cervical fusion. The techniques described for the individual surgical procedures are applicable to the combined Anterior-Posterior procedure. In an anterior-posterior surgery, the amount and positioning of rhBMP-2 will be similar to the anterior surgery (0.525 mg placed anteriorly at each level) or similar to the posterior surgery (2.4 mg across the entire lateral mass on each side posteriorly).

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Eligibility

Locations (1)

Outcomes