Hydroxyapatite cement reconstruction in the growing craniofacial skeleton: an experimental model.

Hydroxyapatite cement (HAC) has been shown to osseoconduct and may even osseoconvert. These properties render it suitable for repairing cranial defects in growing children. The objective of this pilot study was to determine if growth is restricted after HAC reconstruction in a growing, nonprimate, animal model. Frontoparietal craniotomies were performed on 10 4-week-old Yorkshire piglets. In 3 control piglets, the bone flap was resutured; in 7 experimental piglets, the defect was reconstructed with HAC. Analysis 6 months after surgery included craniometric measurements, biomechanical testing, and histological sectioning. Nine craniofacial measurements did not differ between controls and experimental animals. The mean midline-to-temporal line distance contralateral to the defect was 20% larger in the experimental group (P = 0.006), however, and experimental animals had a larger difference between right and left orbital breadths (+3% difference versus -1% difference; P = 0.003). The mean stiffness of the HAC-repaired defect was not different from the contralateral side in contrast to the resutured bone flap in controls, which was significantly less stiff than unoperated bone (162 N/mm compared with 358 N/mm; P < 0.05). Based on our animal model, HAC seems to be a sound alternative method of craniotomy reconstruction in the growing skull.