Dr. Gruber has concerns as to the reason for the surprising success of dorsal augmentation with allografts.1 Dr. Gruber's opinion is highly valued and I would like to address each concern.
The “known history” as reported in multiple recent studies in the orthopedic literature is that freeze-dried allograft bone performs very well without the addition of bone morphogenic protein.2,3 Contrary to recent literature, Dr. Gruber suggests that the “known history” of freeze-dried allograft is poor when bone morphogenic protein is not used. Spine surgeons use allograft alone in the cervical spine, where the U.S. Food and Drug Administration warns against bone morphogenic protein because of the inflammatory reaction and inordinate swelling. There is the distinct possibility of ectopic bone growth and irregularities that would show on the thin nasal dorsum.
The fact that bone morphogenic protein and other growth factors do remain inside freeze-dried allograft has been supported by multiple recent evaluations.4,5 Bone scan evidence of vascularity throughout the allograft after 42 months suggests permanent remodeled bone. Prudence dictates patience, and that is the reason that 5- and 10-year follow-up is planned.
Because there is minimal contact between the allograft and the nasal bones, osteoconduction and fusion are probably limited. We think our success is attributable to osteoinduction, which depends on the allograft stimulation of circulating monocyte stem cells to differentiate into first osteoclasts (partial resorption) and then osteoblasts (bone building). Vascularization is an important criterion for successful remodeling.
Dr. Gruber has applauded the serendipitous finding that the inert “alloimplant” maintained projection in the one case with a totally avascular scar bed. However, he minimizes the fact that the other allografts with a vascular recipient bed have thrived and remodeled. One should always strive for the most vascular recipient bed.
Because our bone scans were performed with fluorine-18 sodium fluoride, which will only concentrate in bone and not scar tissue, I think that our success is primarily through remodeling rather than replacement by scar tissue. In certain cases, it may be attributable to the preservation of an inert alloimplant.
Augmentation of the ethnic nose that has thick skin and a low, flat, wide bridge needs a strong graft to overcome the resistance of thick skin and to create a clean light reflex along the dorsum. Dr. Gruber states that the patient in Figures 1 and 2 “did not need much augmentation” and that his choice would be “at most” temporalis fascia. The preoperative and postoperative photographs speak for themselves. The computed tomographic scan and bone scan in Figure 3 demonstrate a significant 6-mm cortical tibial allograft to her dorsum and also a large allograft to her anterior nasal spine. I believe that Dr. Gruber would find fascia to be a poor cousin to mineralized cortical bone for the above reasons—it simply lacks tensile strength. On a related note, the lack of tensile strength and the failure to maintain shape under pressure is why we did not use demineralized allograft bone.
The patient provided written consent for the use of her image.
Richard P. Clark, M.D.
83 Scripps Drive, Suite 130
Sacramento, Calif. 95825
1.Clark RP, Wong G, Johnson LM, et al. Nasal dorsal augmentation with freeze-dried allograft bone. Plast Reconstr Surg
2.Hillard VH, Fassett DR, Finn MA, Apfelbaum RI. Use of allograft bone for posterior C1-2 fusion. J Neurosurg Spine
3.Ryken TC, Heary RF, Matz PG, et al. Techniques for cervical interbody grafting. Neurosurg Spine
4.Bormann N, Pruss A, Schmidmaier G, Wildemann B. In vitro testing of the osteoinductive potential of different bony allograft preparations. Arch Orthop Trauma Surg.
5.Pietrzak WS, Woodell-May J, McDonald N. Assay of bone morphogenetic protein-2, -4, and -7 in human demineralized bone matrix. J Craniofac Surg.
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