Reconstruction of mandibular continuity defects with bone morphogenetic protein-2 (rhBMP-2)

Several autogenous bone grafting techniques are available for the restoration of large continuity defects of the mandible. However, these procedures are associated with limitations involving postoperative morbidity, difficulty in ambulation, and pain. The development of a technique of surgical reconstruction not involving autogenous bone would offer new opportunities for facial bone reconstruction, particularly of the mandible. This study was instituted to observe the effect of rhBMP-2 in a collagen carrier without concomitant bone grafting material in the restoration of continuity critical-sized defects of the mandible.

A case review was made of 14 patients who were selected from a larger group having received BMP-2 in different categories of mandibular defects. The rhBMP-2 in all the cases reported here was used alone with the collagen carrier without concomitant bone materials. The cases involved lesions of the body and angle of the mandible in 2 categories: 1) defects resulting from neoplastic diseases, and 2) defects secondary to osteomyelitis (related to bisphosphonates or irradiation). A total dose of 4 to 8 mg of rhBMP-2 was delivered to the surgical site in concentrations of 1.5 mg per cc (depending on the size of lesion). Cases were followed over a period from 6 to 18 months. Occlusal function was restored with implant-borne or conventional prosthesis.

All of the cases reported here had successful osseous restoration of the edentulous area followed by prosthetic treatment. Bone formation in the surgical area could be palpated at the end of 3 to 4 months and identified radiographically at the end of 5 to 6 months. The maintenance of a periosteal envelope was effected by the use of a superiorly placed minibar in the upper portion of the defect, or with the use of titanium mesh superiorly. This metallic tenting up to the mucosa is thought to be necessary to maintain the space for osseous regeneration.

This study indicated that the use of rhBMP-2 without concomitant bone grafting materials in large critical sized mandibular defects produced excellent regeneration of the area establishing the basis for the return of prosthodontic function. This study tends to support the use of cytokines, particularly rhBMP-2, in osseous regeneration or repair of facial bones. The technique describes a new alternative to various types of autogenous bone grafting procedures for the treatment of critical sized bony lesions of the mandible.