Biomechanical comparison of calcium phosphate cements for split cranial bone graft donor sites

Although harvesting of in situ split cranial bone is a well-established technique, few data have been generated regarding the biomechanical effect of bone harvest on the cranial bone donor site, and even fewer data have been generated regarding the biomechanical effect of calcium phosphate bone cement inlay on the donor site. The authors documented the weakening of the skull at the in situ cranial harvest site and determined the benefit, if any, when the site is inlayed with calcium phosphate cements.

Cadaver skulls were divided into three groups: group 1, an in situ cranial bone defect was created in the frontal bone area on one side and the mirror-image, full-thickness area was untreated; group 2, a similar defect was created in the parietal area and repaired with calcium phosphate bone cement inlay, and on the opposite side, a similar defect was created but not repaired; and group 3, donor sites were created in the parietal area bilaterally and reconstructed with different cements. Mirror-image areas were harvested and testing was performed. The Wilcoxon rank sum test was used to evaluate all mirror-image specimens.

There was a statistically significant difference in strength to fracture when the in situ defect was compared with the in situ calcium phosphate construct (p = 0.008). No difference was demonstrated when the defect was compared with full-thickness bone or when calcium phosphate cements were compared.

Repair of the defect with calcium phosphate cement significantly increased strength at the donor site and may provide added safety from injury.