Assessment of bone healing in rabbit calvaria grafted with three different biomaterials.

This study evaluated the bone regeneration process in rabbit calvaria induced by three types of biomaterials: two xenogenous, consisting of deproteinized bovine bone, while the other was alloplastic, based on biphasic calcium phosphate. Five New Zealand white rabbits weighing between 2,900 and 3,500 g were submitted to four standard 8 mm-diameter perforations at the parietal bone. Three perforations were filled with three grafts and biomaterials, two of them received bovine Bio-Oss® and Endobon® Xenograft Granules, and the other consisted of fully alloplastic Straumann® Bone Ceramic. The fourth remaining cavity was used as control with coagulum. After eight weeks, the animals were sacrificed, and the samples were prepared for morphometric and qualitative analysis. The cavities filled with alloplastic biomaterials showed higher percentages of newly formed bone (p<0.05), while the cavities with xenogenous biomaterials showed higher amount of residual graft (p<0.05). Although the results showed greater bone formation with Straumann® Bone Ceramic, further studies are required to prove which is the more effective biomaterial for bone induction process.

Percentile-based assessment of craniosynostosis.

Perioperative assessment of craniosynostosis is based mostly on subjective scores. In this study, we sought to find an objective method to assess cranial deformation based on normative craniofacial percentiles. Anthropometric datasets from 104 (79 males, 25 females) patients with craniosynostoses were included. Anthropometric data were compared with normative age-dependent percentiles. Deviations above the 90th or below the 10th percentile were defined as significant cranial deformation. The cohort comprised 69 children with sagittal, 22 metopic, nine coronal, two bicoronal, one lambdoid, and one with coronal + lambdoid craniosynostosis. Most children with sagittal synostosis were above the 90th percentile for cranial circumference and length, whereas only 27.9% were below the 10th percentile for cranial width. Most (83%) children with scaphocephaly had cranial indices below the 10th percentile. For trigonocephaly, we found normal cranial circumference values in most patients (10th-90th percentile), 40.9% were above the 90th percentile for cranial length, and 63.1% and 57.9% were above the 90th percentiles for sagittal and transverse circumferences. For unicoronal synostosis transverse circumference was above the 90th percentile in 83.3% of children. Matching of anthropometric data of craniosynostosis patients with craniofacial norms could be useful in grading the clinical picture and potentially adapting the operative procedure.

Correlation between micro-computed tomography and histomorphometry for assessment of new bone formation in a calvarial experimental model.

Conventional histologic or histomorphometric evaluation provides clear evidence of the bone healing process. However, the sample preparation process is tedious and destructive, and the three-dimensional (3D) anisotropic information of the bone trabeculae is compromised. Micro-computed tomography (microCT) has been introduced as an alternative to these traditional evaluation methods. microCT is noninvasive and provides a faster approach to evaluate and quantify cancellous bone. Most previous studies that used microCT have focused on studying trabecular structures of cancellous bone. In this study, we used microCT to analyze the micro-architecture of the regenerated membranous bone using a rabbit cranial defect model. Two 1 cm diameter circular bony defects were created in 12 New Zealand white rabbits. Specimens were harvested at 6 weeks and 12 weeks after surgery and were scanned using a MicroCT machine (Skyscan 1072, Aartselaar, Belgium). The specimens were then sectioned and stained with Goldner's trichrome. Bone volume density (BV/TV), bone surface density (BS/BV), and trabecular thickness (TbTh) were determined from histomorphometric and two-dimensional (2D) and 3D microCT analysis. Pearson's correlation coefficient (gamma), paired t-tests, and intraclass correlation coefficients from measurements between the 2D and 3D microCT and histomorphometry were calculated. There were very strong positive correlations of BV/TV between histomorphometric and 2D or 3D microCT measurements. Correlation between histomorphometric and 2D microCT measurements for BS/BV was moderate, whereas correlation between histomorphometric and 3D microCT measurements was weak. Weak correlations in TbTh among the three methods were found. In conclusion, the present study suggests that, in evaluating micro-architectures in regenerated bones, the correlation between measuring methods vary according to the features measured.

Quantitative and qualitative assessment of morphology in sagittal synostosis: mid-sagittal vector analysis.

Consensus remains lacking regarding the optimal surgical treatment modality for sagittal synostosis. There is, however, wide agreement that objective analytical methods are required to demonstrate the characteristic morphology of the condition and to substantiate the benefits of specified surgical techniques. Simple calculated anthropomorphic indices, such as the cranial index, are commonly used but fail to provide satisfactory representation of morphology, which is far more complex than can be represented by its simple length-width ratio. Techniques to provide more comprehensive, yet practical, assessment of morphology are needed for analytic purposes. Herein, we introduce vector analysis as an objective, computed tomography (CT)-based morphometric technique for assessment of cranial morphology; this work represents the first application of the technique mid-sagittal vector analysis (MSVA). MSVA is a single plane application that was devised to address dysmorphology in sagittal synostosis. It was our hypothesis that MSVA would quantitatively and qualitatively depict preoperative morphology and postoperative correction in specific regions. Sixteen patients undergoing cranial reshaping surgery for sagittal synostosis were included in the study. All patients underwent routine preoperative and 1 year postoperative CT scans, from which the MSVA was derived. MSVA is a radial vector analysis in which distances to the cranial surface are measured from a single reference point origin in the sagittal plane. Preoperative morphology, characterized by respective vectors, was analyzed in three regions: the frontal, vertex, and occipital regions. Comparison with postoperative paired data was conducted for each patient. The analysis of postoperative change demonstrated (1) decrease in prominence in the frontal and occipital regions, (2) increase in height and forward translation of the vertex, and (3) ability to distinguish and qualify frontal versus occipital bossing and correction thereof. We conclude that the longitudinal differences associated with scaphocephaly are well characterized and differentiated by MSVA. Quantitative and qualitative assessment identifies three relevant regions affected by the condition and its treatment: the frontal, vertex, and occipital regions. The transverse dimension is not addressed in this single plane analysis; a more comprehensive application will require additional planes of analysis and the development of a normative database.

Assessment of the effects on growth of porous hydroxyapatite granule cranioplasty in the immature guinea pig craniofacial skeleton.

The immature guinea pig was used to study the effects on growth of porous granular hydroxyapatite used as an onlay cranioplasty and inlay cranioplasty to reconstruct full-thickness cranial defects in a growing craniofacial skeleton. Forty Hartley guinea pigs, 20 immature animals and 20 mature animals, were divided into four groups each containing five mature and five immature animals. The mature animals served as controls. Group I underwent elevation and replacement of the parietal periosteum. Group II underwent placement of hydroxyapatite between periosteum and parietal bone. Group III underwent elevation and replacement of autogenous bone flap after the formation of a 1 x 1-cm craniectomy defect in the parietal skull. Group IV underwent elevation of a 1 x 1-cm parietal craniectomy and reconstruction of the defect with hydroxyapatite granules placed between the dura and periosteum. Immature animals were killed at maturity at 3.5 months and mature animals were killed 2.5 months postoperatively. Macroscopic examination of the operative field, transverse and longitudinal cephalometric measurements, and histological sections encompassing the operative sites were compared. Macroscopically, all reconstructed operative sites were fully incorporated into the cranium. Histological staining of the sectioned operative site revealed no hydroxyapatite migration through the cranial bone or dura. No inflammatory or foreign body reaction was evident in the subcutaneous tissue, periosteum, or dura. No statistically significant cephalometric intergroup or intragroup differences were found at the conclusion of the study. The results of this study indicate that a granular porous form of hydroxyapatite may be used as an onlay or inlay cranioplasty in the immature guinea pig craniofacial skeleton without evidence of dural inflammation, granule migration, or growth restriction or retardation.

A quantitative assessment of the healing of intramembranous and endochondral autogenous bone grafts.

The aim of the study was to assess quantitatively the amount of new bone formed in the early stages of healing of intramembranous and endochondral autogenous bone grafts so as to gain further insight into their integration with host bone. Eighteen critical size defects were created in the parietal bone of nine New Zealand White rabbits. In the experimental group (five rabbits), each rabbit was grafted with intramembranous bone in one defect and with endochondral bone in the other. In the control group (four rabbits), one defect was left empty (passive control) and the other was grafted with rabbit skin collagen (active control). After 14 days, the rabbits were killed and the defects were prepared for histological analysis. Serial sections were made across the whole defect. Each defect was divided into five regions spaced 1500 microns apart. Two sections were randomly drawn from each region. Quantitative analysis was performed on 100 sections using an image analyser computer software system to assess the amount of new bone formed in each defect. No bone was detected across the defect in either the active or passive controls. One-hundred-and-sixty-six per cent more new bone was formed in defects grafted with intramembranous bone than those grafted with endochondral bone. This represented an extremely significant difference (P < 0.0001, unpaired t-test) between the two groups. The results show that intramembranous autogenous bone produced more bone than the endochondral bone when grafted in the skull. Clinically, it is recommended that intramembranous bone is used to replace lost membranous bone in the oral cavity, as well as in skull defects, whenever possible.