Inlay Cranioplasty: An Experimental Comparison of Particulate Graft versus Bone Dust

Abstract

Cranioplasty in children is difficult because autologous bone is limited. To expand the calvarial donor site, surgeons have used bone dust harvested with a power drill and particulate bone taken with a bit and brace. The purpose of this study was to compare bone dust and particulate bone for inlay cranioplasty. A critical-size defect was made in the parietal bone of rabbits and managed in three ways: group I (n = 5), no implant; group II (n = 6), bone dust implant; and group III (n = 6), particulate graft implant. Bone dust and particulate graft were obtained using a power burr or brace and bit, respectively. Bone dust and particulate graft volume was calculated using a micrometer. Computed tomography was performed 4, 8, and 16 weeks after cranioplasty to determine ossification; histology also was studied. The average volume of particulate bone fragments (6.2 × 10 mm) was 344-fold greater than bone dust particles (1.8 × 10 mm) (p < 0.0001). Four weeks postoperatively, the filled volume of the experimental defect was 6.8 ± 4.9 percent in group I, 8.4 ± 7.4 percent in group II, and 43.0 ± 7.2 percent in group III. Eight weeks postoperatively, the filled volume was 22.3 ± 3.9 percent in group I, 29.1 ± 6.7 percent in group II, and 80.0 ± 8.9 percent in group III. Sixteen weeks postoperatively, the defect was closed 38.6 ± 11.1 percent in group I, 41.3 ± 11.2 percent in group II, and 99.3 ± 1.5 percent in group III (p < 0.0001). Particulate bone graft ossifies full-thickness cranial defects. Bone dust is ineffective and resorbs, possibly because of its smaller particle size and/or thermal injury during harvesting. Particulate graft, and not bone dust, is suitable for inlay cranioplasty.