Background: Although different cranioplasty storage methods are currently in use, no study has prospectively compared these methods. The authors compare freezing and subcutaneous storage methods in a rat model.
Methods: Trephine defects (10 mm) were created in 45 Sprague-Dawley rats. The cranial bone grafts were stored in an autologous subcutaneous pocket (n = 15), frozen at –80°C (n = 15), immediately analyzed (n = 12), or immediately replanted into the defect (n = 3). After 10 days of storage, the subcutaneous or frozen grafts were either replanted (subcutaneous, n = 3; frozen, n = 3) or analyzed (subcutaneous, n = 12; frozen, n = 12). Grafts underwent histologic analysis, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase assay, mechanical testing, and micro–computed tomographic imaging.
Results: After 10 days of storage, physiologic assays demonstrated a significant decrease in cellular functionality (e.g., alkaline phosphatase assay concentration: fresh, 18.8 ± 0.77 mM/mg; subcutaneous, 12.2 ± 0.63 mM/mg; frozen, 8.07 ± 1.1 mM/mg; p < 0.012 for all comparisons). Mechanical integrity (maximal load) of fresh grafts was greatest (fresh, 9.26 ± 0.29 N; subcutaneous, 6.27 ± 0.64 N; frozen, 4.65 ± 0.29 N; fresh compared with frozen, p < 0.001; fresh compared with subcutaneous, p = 0.006). Replantation of subcutaneously stored and frozen grafts resulted in limited bony union and considerable resorption after 12 weeks; in contrast, replanted fresh grafts demonstrated bony union and little resorption.
Conclusions: Current preservation methods for interval cranioplasty do not maintain bone graft viability. Subcutaneous storage appears to provide a small advantage compared with freezing.
New York, N.Y.
From the Institute of Reconstructive Plastic Surgery Laboratories, New York University Medical Center, and the New York University College of Dentistry.
Received for publication October 1, 2010; accepted November 8, 2010.
Presented in part at the 67th Annual Meeting of the American Cleft Palate–Craniofacial Association, in Fort Worth, Texas, March 16 through 20, 2010, and at the 55th Annual Meeting of the Plastic Surgery Research Council, in San Francisco, California, May 23 through 26, 2010.
Disclosure: The authors have no financial interest to declare in relation to the content of this article.
Stephen M. Warren, M.D., Institute of Reconstructive Plastic Surgery, New York University Medical Center, 560 First Avenue, TCH-169, New York, N.Y. 10016, firstname.lastname@example.org