Greg Cooper

Nonsynostotic occipital plagiocephaly : Radiographic diagnosis of the sticky suture

Background: While the clinical differences between nonsynostotic occipital plagiocephaly and lambdoid craniosynostosis have been described, the radiographic differentiation between the two remains obscure. The aim of this study was to characterize morphological differences in the lambdoid suture between nonsynostotic occipital plagiocephaly and lambdoid craniosynostosis. Methods: Computed tomography scans of children clinically diagnosed with nonsynostotic occipital plagiocephaly (n = 26) were compared with computed tomography scans from children diagnosed with lambdoid craniosynostosis (n = 7). Suture and cranial morphology, ear position, and endocranial base angles were qualitatively and quantitatively compared. Results: Nonsynostotic occipital plagiocephaly sutures demonstrated areas of focal fusion (25 percent), endocranial ridg-ing (78 percent), narrowing (59 percent), sclerosis (19 percent), and changes from overlapping to end-to-end orientation (100 percent). No sutures demonstrated ectocranial ridging. All cases of nonsynostotic occipital plagiocephaly presented with ipsilateral occipital flattening, 85 percent with ipsilateral frontal, and 95 percent with contralateral occipital bossing producing parallelogram morphology. In contrast, a greater frequency of sutures in lambdoid craniosynostosis patients demonstrated nearly complete obliteration (p < 0.001) with ectocranial ridging (p < 0.001); significantly more of these patients presented with ipsilateral occipital flattening with compensatory ipsilateral mastoid (p < 0.001) and contralateral parietal (p < 0.01) bossing, producing a trapezoid morphology. Sutures from nonsynostotic occipital plagiocephaly patients showed endocranial ridging, focal fusions, and narrowing, previously reported as lambdoid craniosynostosis. Conclusions: In contradiction to previous reports, lambdoid craniosynostosis is not radiographically unique among suture fusions. This work establishes the radiographic diagnosis of nonsynostotic occipital plagiocephaly.

Internal Calvarial Bone Distraction in Rabbits with Delayed-Onset Coronal Suture Synostosis

&NA; Recent studies have identified a subpopulation of craniosynostotic individuals who exhibit progressive or delayed‐onset synostosis and mild craniofacial growth abnormalities. These individuals may be good candidates for nonextirpation, distraction osteogenesis therapy. The present study was designed to test this hypothesis by using internal calvarial bone distraction in a rabbit model with familial delayed‐onset craniosynostosis. Data were collected from 159 rabbits: 71 normal controls, 72 with delayed‐onset coronal suture synostosis, 8 with delayed‐onset coronal suture synostosis and coronal suturectomy, and 8 with delayed‐onset coronal suture synostosis and distraction. At 10 days of age, all rabbits had amalgam markers placed on both sides of the frontonasal, coronal, and anterior lambdoidal sutures. At 25 days of age, correction was accomplished through either a 5‐mm‐wide suturectomy or distraction osteogenesis. An internal distraction appliance was fixed to the frontal and parietal bones and percutaneously and intermittently activated at an average of 0.10 mm/day for 42 days (4.11 mm total). Serial radiographs were taken at 10, 25, 42, and 84 days of age. Results revealed that rabbits with delayed‐onset synostosis had significantly (p < 0.01) reduced coronal suture growth rates (0.04 mm/day) compared with the other three groups (0.07 mm/day). Rabbits with suturectomy and rabbits with distraction showed similar coronal suture responses. However, from 42 to 84 days of age, rabbits with distraction showed reduced growth at the vault sutures and abnormal growth patterns in cranial vault width, cranial vault shape, and cranial base angulation compared with the other three groups. Results demonstrated that, although the normal coronal suture growth rate was maintained in rabbits with delayed‐onset synostosis using intermittent distraction osteogenesis, normal adult craniofacial structure was not achieved. Such anomalous growth was probably a result of altered growth vectors and compressive forces at adjacent sutures during distraction. These findings suggest that distraction osteogenesis without corticotomy may be a treatment alternative in individuals with progressive, delayed‐onset synostosis, but that internal appliances that generate low‐level, continuous distractive forces should be investigated and developed. (Plast. Reconstr. Surg. 102: 1109, 1998.)

Transforming growth factor-β3 therapy delays Postoperative reossification and improves craniofacial growth in craniosynostotic rabbits

Postoperative reossification is a common clinical correlate following surgery. It has been suggested that an underexpression of transforming growth factor-β3 (TGF-β3) may be related to craniosynostosis and postoperative reossification. Adding TGF-β3 may delay reossification and improve postoperative growth. The present study was designed to test this hypothesis. Thirty 10-day-old New Zealand white rabbits with hereditary coronal suture synostosis were divided into three groups: (1) suturectomy controls (n = 14), (2) suturectomy treated with bovine serum albumin (n = 8), and (3) suturectomy treated with TGF-β3 protein (n = 8). At 10 days of age, a 3-mm × 15-mm coronal suturectomy was performed, and serial three-dimensional (3D) computed tomography (CT) scans and cephalographs were taken at 10, 25, 42, and 84 days of age. Calvaria were harvested at 84 days of age for histomorphometric analysis. Mean differences were analyzed using a group by age analysis of variance. Analysis of the 3D CT scan data revealed that sites treated with TGF-β3 had significantly (P < .05) greater defect areas and significantly (P < .05) greater intracranial volumes through 84 days of age compared with controls. Histomorphometry showed that sites treated with TGF-β3 had patent suturectomy sites and significantly (P < .001) less new bone in the suturectomy site compared with controls. Serial radiograph data revealed significant (P < .05) differences in craniofacial growth from 25 to 84 days in TGF-β3-treated rabbits compared with controls. Data show that TGF-β3 administration delayed reossification and improved craniofacial growth in this rabbit model. These findings also suggest that this molecular-based therapy may have potential clinical use.

Relationship of Premaxillary Bone and Its Sutures to Deciduous Dentition in Nonhuman Primates

Objective: The relationship of the human premaxillary bone (Pmx) to neighboring craniofacial structures is clouded by its embryonic union with the maxillary bone proper. Only humans among all primates have such early fusion of the premaxillomaxillary suture (PS). This study surveyed the relationship of the PS to the upper deciduous dentition in nonhuman primates, and describes the distribution of bone cells along the osseous margins of the Pmx. Method: Twenty-eight subadult primates were studied using gross, CT, and histologic observations. Location of the anterior deciduous dentition relative to the PS was assessed. In sections of selected specimens, observations of bone cells on the osseous boundaries of the Pmx were made. Osteopontin (OPN) immunohistochemistry was used to isolate osteoclastic binding sites along the Pmx boundaries. Results: The PS was consistently found between deciduous incisor and canine in strepsirrhines of all ages, whereas the suture passed variably closer to the incisor or canine in haplorhines. In all species, the anterior part of the Pmx was nonarticulating and mostly osteoblastic, except for osteoclastic margins adjacent to dentition and the nasal fossa. Superolaterally, the osteogenic fronts of the PS were osteoblastic, while more inferiorly, at the level of the deciduous canine, the PS was often osteoclastic. Results from OPN immunohistochemistry support the findings on bone cell distribution. Conclusion: Bone cell distribution patterns in perinatal nonhuman primates resemble those described for the prenatal human Pmx, suggesting that differences among species relate to magnitude rather than the pattern of osteogenesis.

The effects of testosterone on craniosynostotic calvarial cells: a test of the gene/environmental model of craniofacial anomalies.

INTRODUCTION The gene-environmental interaction model for craniofacial development proposes that if a genetic predisposition for an anomaly is coupled with an environmental factor that can exacerbate this predisposition, more severe phenotypes will result. Here, we utilize cells derived from our non-syndromic rabbit model of craniosynostosis to test the hypothesis that an insult, testosterone (TP) administration (exogenous source) will alter the osteogenic activity of these cells. DESIGN Calvarial cells from wild-type (WT) (N=13) or craniosynostotic (CS) rabbits (N=11) were stimulated with TP, an androgen receptor blocker, flutamide, and combined treatments. Proliferation and differentiation assays were conducted after 7 days. anova and t-tests were used to determine differences in stimulation and cell type. RESULTS The CS cells had significantly greater proliferation after TP administration compared to WT. There were no appreciable changes in differentiation after TP stimulation. Flutamide administration or combined TP and flutamide administration decreased both proliferation and differentiation for both cell types similarly. CONCLUSIONS Testosterone exposure caused an increase in cell proliferation for CS osteoblast cells. However, a therapy targeted to mitigate this response (flutamide therapy) similarly affected CS and WT cells, suggesting that the administration of flutamide or TP in the presence of flutamide decreases osteogenesis of these cells. Thus, although our data support a mechanism of gene-environmental interaction, these results would not support a therapeutic intervention based on this interaction.

Heilungsverhalten und Knochenregeneration von maxillären Osteotomien im experimentellen Kaninchenmodell

Einführung: Die Entstehung fibröser Ankylosen anstelle knöcherner Heilung nach orthognather Chirurgie wird Interaktionen von biomechanischen Stressfaktoren und der im Vergleich zu Osteoblasten differenzierteren und schnelleren Migration von Fibroblasten in den Wundbereich zugeschrieben. Ziel dieser Studie war die Überprüfung dieser Hypothese im experimentellen Kaninchenmodell unter Anwendung von gesteuerter Knochenregeneration (GTR) und Osteosynthesen. Material und Methode: In den Oberkiefern von 12 erwachsenen New-Zealand-White-Kaninchen wurden als Osteotomien (n = 24) beidseitig Critical-size-Defekte (4 mm) gesetzt. Die Oberkiefersegmente wurden im Vergleich zur kontralateralen Seite mit Mikroplattenosteosynthesen und -schrauben oder Drahtosteosynthesen stabilisiert. Zusätzlich wurden die Defekte entweder mit einer resorbierbaren Kollagenmembran abgedeckt oder nicht. Postoperativ, nach 2 und nach 4 Wochen wurden Fernröntgen im posterior-anterioren und seitlichen Strahlengang durchgeführt. Anschließend wurden die Oberkiefer für histologische Analysen gewonnen. Ergebnisse: Mit radiologischen und histomorphometrischen Analysen wurde nachgewiesen, dass von Membranen abgedeckte Defekte in stabil fixierten Osteotomien schnellere und früher organisierte neue Knochenformation zeigten. Diese mit Membranen abgedeckten Defekte in stabil fixierten Osteotomien enthielten im Vergleich zu nicht mit Membranen abgedeckten Defekten in stabil fixierten Osteotomien 40% mehr neuen Knochen. Defekte ohne Membranabdeckung in instabil fixierten Osteotomien zeigten Fibroblastenproliferation und fibröse Ankylosierungen. Schlussfolgerung: Die Ergebnisse dieser Studie am experimentellen Kaninchenmodell belegen, dass Interaktionen zwischen verminderter Fibroblastenproliferation durch gesteuerte Knochenregeneration und Osteotomiesegmentstabilisierung mittels Osteosynthesen postoperativ fibröse Ankylosen hintanhalten und neue Knochenregeneration und Heilung der Osteotomien fördern. Purpose: The development of fibrous nonunions following orthognathic surgery is thought to result from an interaction of biomechanical stress and the differential and more rapid migration of fibroblasts compared to osteoblasts into the wound site during healing. The present study was designed to test this hypothesis through the manipulation of guided tissue regeneration and osteotomy fixation techniques in an experimental rabbit model. Materials and methods: Bilateral critical size (4 mm) defects ¶(n = 24) were produced in the maxillae of 12 adult New Zealand White rabbits. The maxillary segments were rigidly or nonrigidly fixed using bone microplates and screws or osteosynthetic wires. The defects were then covered with a resorbable collagen membrane or left uncovered. The rabbits were followed for 4 weeks with serial dorsoventral and lateral oblique cephalographs and the maxillae were then harvested for histological analysis. Results: Radiographic and histomorphometric analysis revealed that rigidly fixed defects, covered with membrane, showed the most rapid and organized new bone formation. The rigidly fixed defects with membrane averaged approximately 40% more new bone in the osteotomy site than the rigidly fixed defects with no membrane. Nonrigidly fixed defects with no membrane also showed an ingrowth of fibroblasts and fibrous nonunions. Conclusion: These results suggest that an interaction between the decreased fibrous tissue ingrowth through guided tissue regeneration and osteotomy segment stability from rigid fixation prevented postoperative fibrous nonunions and facilitated new bone regeneration and osteotomy site healing in this rabbit model.PURPOSE The development of fibrous nonunions following orthognathic surgery is thought to result from an interaction of biomechanical stress and the differential and more rapid migration of fibroblasts compared to osteoblasts into the wound site during healing. The present study was designed to test this hypothesis through the manipulation of guided tissue regeneration and osteotomy fixation techniques in an experimental rabbit model. MATERIALS AND METHODS Bilateral critical size (4 mm) defects (n = 24) were produced in the maxillae of 12 adult New Zealand White rabbits. The maxillary segments were rigidly or nonrigidly fixed using bone microplates and screws or osteosynthetic wires. The defects were then covered with a resorbable collagen membrane or left uncovered. The rabbits were followed for 4 weeks with serial dorsoventral and lateral oblique cephalographs and the maxillae were then harvested for histological analysis. RESULTS Radiographic and histomorphometric analysis revealed that rigidly fixed defects, covered with membrane, showed the most rapid and organized new bone formation. The rigidly fixed defects with membrane averaged approximately 40% more new bone in the osteotomy site than the rigidly fixed defects with no membrane. Nonrigidly fixed defects with no membrane also showed an ingrowth of fibroblasts and fibrous nonunions. CONCLUSION These results suggest that an interaction between the decreased fibrous tissue ingrowth through guided tissue regeneration and osteotomy segment stability from rigid fixation prevented postoperative fibrous nonunions and facilitated new bone regeneration and osteotomy site healing in this rabbit model.

Abstract 81: BMP2 Stimulation of Adipose, Bone Marrow, and Muscle-Derived Stromal Cells Fails to Augment Calvarial Repair.

PurPose: Tissue engineering is becoming a viable adjunct or even alternative to autologous bone grafting in craniofacial reconstruction. Current methods focus on implantation of bioresorbable scaffolds seeded with proteins and/or osteogenic progenitor cells, although it remains unclear whether specific stromal cell types are better suited for use in craniofacial reconstruction. This study aims to determine the healing capacity of adipose (ADSC), bone marrow (BMDSC), and muscle-derived (MDSC) stromal cell populations in a calvarial defect model when this environment is optimized using bone morphogenetic protein 2 (BMP2). We hypothesize that BMP2 will augment stromal cell engraftment and differentiation within calvarial defects.