Frontonasal Sutures Research Articles

A Study on Morphological and Morphometrical Parameters on the Skull of the Konya Merino Sheep

Objective: In this study, it was aimed to determine the craniometric measurements of the skull of the Konya Merino breed and to reveal the differences between it and other sheep breeds. 
 Material-Method: For this study, ten Konya merino heads were used and craniometric measurements were made from 46 points on the skull. 
 Result: In the study, the skull length of the Konya merino was 274.03 ± 5.23, the frontal width (ectorbitale – ectorbitale) which is the widest region of the skull 123.47 ± 2.60, zygomatic width (the distance between two zygomatic arches) 110.30 ± 1.96 and the distance between the foramen supraorbitales 49.06 ± 2.38. has been found to be. It was determined that both the fronto-nasal and palato-maxillar sutures resembled the letter "V" in Konya merino, while the pariato-frontal suture was in the form of a straight line. When the correlation between index values was examined, it was seen that there was a statistically significant strong positive correlation between I1 (Nasal index) and I2 (Facial Index), but the relationship between other examined features was insignificant. When the statistically significant correlation values of the skull measurements are examined, it is seen that there is a strong negative or positive correlation between the features. While the highest positive correlation was between L5 (premolare – prosthion) and L39 (greatest palatal breadth (measured across the outer borders of the alveoli) features (0.943), the highest negative correlation was L33 (greatest neurocranium breadth-greatest breadth of the alveoli)). braincase (euryon - euryon) and L46 (supraorbital foramina distance) features were found to be (-0.908). 
 Conclusion: As a result, in this study, it is thought that the difference in the craniometric values of Konya merino, which is accepted as the native breed of Turkey, with other sheep breeds, depending on the skull morphology, may be caused by the breed of sheep.

Effect of reciprocal headgear forces on the calvarium: A finite element study

Orthopedic appliances continue to be used for various sagittal, vertical, and transverse corrections of the maxilla. Although cranial growth can continue to adulthood, no study has drawn attention to the effects of headgear forces on the calvarium, in which anchorage is taken. This study focused on the different biomechanical responses on the calvarium of young children wearing a high-pull headgear of varying forces, using a 3-dimensional finite element analysis and the possible implications of such changes on the human skull. A 3-dimensional finite element model of a 9-year-old child was designed from the computed tomography scan. The material properties of the juvenile skull were assigned. Varying orthopedic forces (400, 500, and 600 g of force) were applied, and the magnitude of displacement and stresses generated on the cranial bones and sutures were interpreted using ANSYS software (version 12.1; Canonsburg, Pa). Maximum displacement was found for the parietal bone in the inferior direction; parietal and temporal bones in the transverse direction; and frontal, parietal, and temporal bones in the sagittal direction. The least displacement was noted for the occipital bone in all the 3-dimensions. The maximum stresses were concentrated over the region of the lateral margins of the piriform aperture and the medial walls of the orbit. Higher stress values were also found on the parietal bone adjacent to the sagittal suture. The highest value of stresses among the sutures of the craniofacial complex was found to be in the region of the frontonasal, frontomaxillary, and nasomaxillary sutures. The effects of displacement and stresses obtained from this study suggest a restriction to the growth of the cranial vault and its normal mobility, in turn altering the intracranial tension and causing altered cranial morphology in young, growing children undergoing high-pull headgear therapy. The human cranial system is dynamic throughout life and may be restricted or altered by hereditary or environmental factors.

Short-term effects of microimplant-assisted rapid palatal expansion on the circummaxillary sutures in skeletally mature patients: A cone-beam computed tomography study

This study aimed to investigate the short-term effects on the circummaxillary sutures induced by microimplant-assisted rapid palatal expansion (MARPE) in skeletally mature patients. Cone-beam computed tomography (CBCT) images of preexpansion (T0) and postexpansion (T1) of 23 patients (mean age, 20.9±3.65years) treated with MARPE were evaluated. The T0 and T1 CBCT images were reoriented and superimposed on the basis of the anterior cranial base, using OnDemand3D software (Cybermed, Seoul, Korea). Then, width changes of 9 circummaxillary sutures (frontonasal, frontomaxillary, frontozygomatic, nasomaxillary, zygomaticomaxillary, intermaxillary, midpalatal, zygomaticotemporal, and pterygopalatine sutures) were measured on 1 section of each patient's T0 and T1 CBCT images. In addition, correlation coefficients between changes in the midpalatal sutures, the amount of appliance activation, age, and the changes in other circummaxillary sutural widths were also calculated. Statistically significant (P<0.05) width increases were found in all 9 circummaxillary sutures. The changes in midpalatal suture at the maxillary central incisor level positively correlated with the intermaxillary sutures at the anterior nasal spinelevel, midpalatal sutures at the posterior nasal spine level, and frontomaxillary sutures (P<0.05). In addition, the changes in the midpalatal sutures at the posterior nasal spine level also positively correlated with the changes in the intermaxillary sutures at the anterior nasal spine level, frontomaxillary sutures, and medial pterygopalatine sutures (P<0.05). All 9 circummaxillary sutural widths increased in skeletally mature patients immediately after MARPE. The greatest increases in width were measured in the midpalatal sutures and the intermaxillary sutures, followed by the frontomaxillary sutures.

Preliminary Evaluation of Three-dimensional Cinematic Rendering Computed Tomography Images of Frontonasal Sutures in Personal Identification

• The preliminary result shows that the morphology pattern of the frontal suture is unique and can be use in personal identification. • A frontonasal suture is a trough on the skull surface which can be well demonstrated by cinematic volume rendering 3D images. • CT scans of craniofacial region used in routine clinical practice have potential to be renderred and used as an ante mortem data to match with an unknown skull. To evaluate cinematic rendering 3DCT of frontonasal suture in personal identification Four readers completed three questionnaires: matching a 3DCT of 50 skulls with the photographs, evaluating the clarity of 3DCT, and determining the suitability of 20 clinical scans. Correct matching were high (98-100%). Clarity of 3DCT (mean 10-point-Likert scores 5.64-8.04) was higher than required (3.78-4.78). Sixty percent of clinical scans were suitable. 3DCT of frontonasal suture potentially be used for identification.

How I do it. 3D endoscopic treatment of metopic craniosynostosis through a single incision.

Endoscopic approaches for craniosynostosis are a growing field in pediatric neurosurgery. In metopic synostosis, previous reports for complete fronto-orbital remodeling have proposed an intervention with multiple incisions (bregmatic, tarsal, and preauricular) to open frontonasal and frontoethmoidal synostotic sutures, and orbital roof. We propose a technique to complete all these osteotomies with a unique incision anterior to the bregmatic fontanel under 3D endoscopic vision, and review possible complications, limits, and pitfalls. Under endoscopic assistance, a complete fronto-orbital remodeling could be completed with a unique incision without mayor drawbacks.

Evaluation of rapid maxillary expansion through acoustic emission technique and relative soft tissue attenuation

ObjectivesAcoustic emission (AE) is a non-destructive test to detect energy release. This technique was applied during rapid maxillary expansion (RME) to evaluate the reaction of the craniofacial skeleton. Materials and methodsA swine model was analysed. Soft tissues were removed from two heads, while other two were preserved intact. A palatal expander (PE) was positioned and AE sensors were placed on the intermaxillary, fronto-nasal, and maxillo-lacrimal sutures. The PE was activated and AE recorded during RME. Differences between parameters were analysed with Mann-Whitney U test and Kruskal-Wallis test, and correlations with Spearman-Rho test (significance p<0.05). ResultsPE activations were accompanied by clusters of AE hits. In the presence of soft tissues, amplitudes were generally lower (p<0.001) and durations were higher (p<0.001). No differences were found in the respective energy values. Differences were found in the AE (p<0.05) among the four channels, with AE characterised by higher values in proximity of the maxillo-lacrimal sutures. High-energy hits were represented by burst-type waves, and low-energy ones by continuous-type. ConclusionsAlthough soft tissues create possible attenuation of the signal, AE can be detected during RME with sensors on the skin. AE provided further information of energy release, on top of the mechanical parameters. Source location was one of the main limitations.

Metopic Frontal Suture in a Patient With Severe Dentofacial Deformity Undergoing Bimaxillary Surgery

Six cranial fontanelles are present in newborns along with cranial sutures. Cranial sutures are a synarthrosis type of joints that occur in the skull after closure of fontanelles. Because of ossification up to 24 months, all fontanelles should be closed. Normal frontal bone consists of only frontonasal, frontozygomatic, frontomaxillaris, frontolacrimalis, and main coronal sutures. Metopic frontal suture occurs very rarely in adults. Some metopic frontal sutures might be related to genetic or general disorders or perhaps are related to an improper ossification. In some cases, it persists as a complete suture extending from the nasion to the anterior angle of the bregma, and this condition is called metopism, or metopic suture. In this article, we present a patient with metopic frontal suture diagnosed accidentally during preparation for bimaxillary orthognathic surgery.

An assessment of the maxilla after rapid maxillary expansion using cone beam computed tomography in growing children.

IntroductionWith the advent of cone beam computed tomography (CBCT), it is now possible to quantitatively evaluate the effects of rapid maxillary expansion (RME) on the entire maxillary complex in growing patients. ObjectiveThe purpose of this study is to use three-dimensional images to evaluate the displacement that occurs at the circummaxillary sutures (frontonasal, zygomaticomaxillary, intermaxillary, midpalatal, and transpalatal sutures) following rapid maxillary expansion in growing children. MethodsThe CBCT scans of 25 consecutively treated RME patients (10 male, 15 female) with mean age of 12.3 ± 2.6 years, were examined before expansion and immediately following the last activation of the expansion appliance. ResultsStatistically significant (P < 0.05) amounts of separation were found for the displacement of the bones of the frontonasal suture, the intermaxillary suture, the zygomaticomaxillary sutures, and the midpalatal suture. The change in angulation of the maxillary first molars due to RME was also statistically significant. There was no statistically significant displacement of the transpalatal suture. ConclusionsRapid maxillary expansion results in significant displacement of the bones of circummaxillary sutures in growing children.

Stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall: A 3-dimensional finite element analysis

The purpose of this study was to compare the pattern and amount of stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall. Three-dimensional finite element models for the skull and the curvilinear type of miniplate were constructed. After a protraction force (500 g/side) was applied to the distal end of the miniplate with a forward and 30° downward vector to the maxillary occlusal plane, stress distributions in the circummaxillary sutures and displacements of the surface landmarks were analyzed. There was a difference in the maximum stress distribution area according to the site of the miniplate: infrazygomatic crest and middle part of the maxilla in the infrazygomatic crest and paranasal area adjacent to the pyriform aperture in the lateral nasal wall. Stress values of the frontonasal, frontomaxillary, zygomaticomaxillary, and pterygomaxillary sutures were greater in the infrazygomatic crest than in the lateral nasal wall. The site of the miniplate produced differences in the major displacement areas: infrazygomatic crest, maxillary dentition, anterior maxilla, and upper part of the maxillary tuberosity in the infrazygomatic crest and the lateral nasal wall, maxillary dentition, anterior maxilla, and lower part of the maxillary tuberosity in the lateral nasal wall. The lateral nasal wall exhibited forward, downward, and outward displacements of ANS, Point A, and prosthion. However, the infrazygomatic crest showed forward and upward displacements of ANS, Point A, and prosthion, and outward displacement of the zygomatic process of the maxilla and the maxillary process of the zygomatic bone. The site of miniplate placement should be considered to obtain proper stress and displacement values in different areas with maxillary hypoplasia.

Effects of rapid maxillary expansion on the cranial and circummaxillary sutures

The aim of this study was to determine whether the orthopedic forces of rapid maxillary expansion cause significant quantitative changes in the cranial and the circummaxillary sutures. Twenty patients (mean age, 12.3 ± 1.9 years) who required rapid maxillary expansion as a part of their comprehensive orthodontic treatment had preexpansion and postexpansion computed tomography scans. Ten cranial and circummaxillary sutures were located and measured on one of the axial, coronal, or sagittal sections of each patient's preexpansion and postexpansion computed tomography scans. Quantitative variables between the 2 measurements were compared by using the Wilcoxon signed rank test. A P value less than 0.05 was considered statistically significant. Rapid maxillary expansion produced significant width increases in the intermaxillary, internasal, maxillonasal, frontomaxillary, and frontonasal sutures, whereas the frontozygomatic, zygomaticomaxillary, zygomaticotemporal, and pterygomaxillary sutures showed nonsignificant changes. The greatest increase in width was recorded for the intermaxillary suture (1.7 ± 0.9 mm), followed by the internasal suture (0.6 ± 0.3 mm), and the maxillonasal suture (0.4 ± 0.2 mm). The midpalatal suture showed the greatest increase in width at the central incisor level (1.6 ± 0.8 mm) followed by the increases in width at the canine level (1.5 ± 0.8 mm) and the first molar level (1.2 ± 0.6 mm). Forces elicited by rapid maxillary expansion affect primarily the anterior sutures (intermaxillary and maxillary frontal nasal interfaces) compared with the posterior (zygomatic interface) craniofacial structures.

An ENU-induced mutation in the Ankrd11 gene results in an osteopenia-like phenotype in the mouse mutant Yoda

The mechanisms that regulate bone mass are important in a variety of complex diseases such as osteopenia and osteoporosis. Regulation of bone mass is a polygenic trait and is also influenced by various environmental and lifestyle factors, making analysis of the genetic basis difficult. As an effort toward identifying novel genes involved in regulation of bone mass, N-ethyl-N-nitrosourea (ENU) mutagenesis in mice has been utilized. Here we describe a mouse mutant termed Yoda that was identified in an ENU mutagenesis screen for dominantly acting mutations. Mice heterozygous for the Yoda mutation exhibit craniofacial abnormalities: shortened snouts, wider skulls, and deformed nasal bones, underlined by altered morphology of frontonasal sutures and failure of interfrontal suture to close. A major feature of the mutant is reduced bone mineral density. Homozygosity for the mutation results in embryonic lethality. Positional cloning of the locus identified a missense mutation in a highly conserved region of the ankyrin repeat domain 11 gene (Ankrd11). This gene has not been previously associated with bone metabolism and, thus, identifies a novel genetic regulator of bone homeostasis.

Stress and displacement patterns in the craniofacial skeleton with rapid maxillary expansion: A finite element method study

The purpose of this finite element study was to evaluate stress distribution along craniofacial sutures and displacement of various craniofacial structures with rapid maxillary expansion (RME) therapy. The analytic model for this study was developed from sequential computed tomography scan images taken at 2.5-mm intervals of a dry young human skull. Subsequently, a finite element method model was developed from computed tomography images by using AutoCAD software (2004 version, Autodesk, Inc, San Rafael, Calif) and ANSYS software (version 10, Belcan Engineering Group, Downers Grove, Ill). The maxilla moved anteriorly and downward and rotated clockwise in response to RME. The pterygoid plates were displaced laterally. The distant structures of the craniofacial skeleton--zygomatic bone, temporal bone, and frontal bone--were also affected by transverse orthopedic forces. The center of rotation of the maxilla in the X direction was somewhere between the lateral and the medial pterygoid plates. In the frontal plane, the center of rotation of the maxilla was approximately at the superior orbital fissure. The maximum von Mises stresses were found along the frontomaxillary, nasomaxillary, and frontonasal sutures. Both tensile and compressive stresses could be demonstrated along the same suture. RME facilitates expansion of the maxilla in both the molar and the canine regions. It also causes downward and forward displacement of the maxilla and thus can contribute to the correction of mild Class III malocclusion. The downward displacement and backward rotation of the maxilla could be a concern in patients with excessive lower anterior facial height. High stresses along the deep structures and the various sutures of the craniofacial skeleton signify the role of the circummaxillary sutural system in downward and forward displacement of the maxilla after RME.

Restricting facial bone growth with skeletal fixation: A preliminary study

Conventional orthodontic treatment of vertical or anterior maxillary excess by growth modification can be problematic in children because of the high levels of patient compliance required. The purpose of this preliminary study was to investigate the use of rigid skeletal fixation to modify facial bone growth without compliance. Three 30-day old female pigs from the same litter were included in phase I. Pediatric miniplates were rigidly fixated with monocortical screws in the experimental pig to bridge the zygomaticomaxillary suture and both the frontonasal and nasomaxillary sutures, bilaterally. In the sham experimental pig, the same surgical protocol was followed, but miniplates were omitted (ie, screw placement only). In the control pig, surgery was not performed. All 3 pigs were housed and fed a normal diet under identical conditions postoperatively for 63 days; then they were killed, their right hemi-skulls were prepared for and underwent 3-dimensional coordinate landmark analysis, and en-bloc specimens from the zygomaticomaxillary, frontonasal, and nasomaxillary sutures of the left hemi-skulls underwent histologic analysis. Two 50-day-old female pigs from the same litter were used in phase II. The same experimental protocol was followed as before for the experimental pig and the sham experimental pig. Both pigs were fed a normal diet for 105 days; then they were killed, and their skulls were prepared for and underwent 3-dimensional coordinate landmark analysis. Rigid plating restricted zygomaticolacrimal suture length, maxillary bone length, nasal bone length, midfacial breadth, and frontal bone length by an average of -14% to -15% (range, -4% to -36%). No growth differences were noted between the animals in maxillary height, mid-premaxillary length, bregma-lambda length, palatal lengths, or mandibular length. Also, plating the sutures produced a clear depressed concavity in the infraorbital region, altered the alignment of the infraorbital plane lateral to the concavity, inhibited the anterior migration of the maxillary tuberosity, and resulted in raised folding on the bony surface adjacent to the zygomaticomaxillary suture. Rigidly fixating frontonasomaxillary and zygomaticomaxillary sutures inhibits growth of facial bones and might provide a means of restricting excess growth without having to rely on patient compliance. In addition, these altered growth patterns in the plated pig model produced similar and potentially homologous infraorbital features shared by living humans in comparison with ancestral fossil forms.

Biomechanical study of maxillary expansion treatment using bone-anchors—Three dimensional finite element analyses

This study aimed to investigate the short-term effects on the circummaxillary sutures induced by microimplant-assisted rapid palatal expansion (MARPE) in skeletally mature patients.Cone-beam computed tomography (CBCT) images of preexpansion (T0) and postexpansion (T1) of 23 patients (mean age, 20.9 ± 3.65 years) treated with MARPE were evaluated. The T0 and T1 CBCT images were reoriented and superimposed on the basis of the anterior cranial base, using OnDemand3D software (Cybermed, Seoul, Korea). Then, width changes of 9 circummaxillary sutures (frontonasal, frontomaxillary, frontozygomatic, nasomaxillary, zygomaticomaxillary, intermaxillary, midpalatal, zygomaticotemporal, and pterygopalatine sutures) were measured on 1 section of each patient’s T0 and T1 CBCT images. In addition, correlation coefficients between changes in the midpalatal sutures, the amount of appliance activation, age, and the changes in other circummaxillary sutural widths were also calculated.Statistically significant (P <0.05) width increases were found in all 9 circummaxillary sutures. The changes in midpalatal suture at the maxillary central incisor level positively correlated with the intermaxillary sutures at the anterior nasal spine level, midpalatal sutures at the posterior nasal spine level, and frontomaxillary sutures (P <0.05). In addition, the changes in the midpalatal sutures at the posterior nasal spine level also positively correlated with the changes in the intermaxillary sutures at the anterior nasal spine level, frontomaxillary sutures, and medial pterygopalatine sutures (P <0.05).All 9 circummaxillary sutural widths increased in skeletally mature patients immediately after MARPE. The greatest increases in width were measured in the midpalatal sutures and the intermaxillary sutures, followed by the frontomaxillary sutures.

Frontonasal process-specific disruption of AP-2α results in postnatal midfacial hypoplasia, vascular anomalies, and nasal cavity defects

A majority of the bones of the vertebrate cranial vault and craniofacial complex develop via intramembranous ossification, and are separated by fibrous sutures that undergo osteogenic differentiation in response to growth stimuli. Craniosynostosis is a common human birth defect that results from the premature bony fusion within skull sutures, and causes a myriad of complications including mental retardation and craniofacial anomalies. Synostosis of facial sutures has been reported to cause midfacial hypoplasia in some craniosynostosis cases, but most studies focus on cranial vault sutures. In this study, we have generated a mouse model of frontonasal suture synostosis and midfacial hypoplasia through the tissue-specific elimination of the AP-2α transcription factor. We report here the generation AP-2CRE, a frontonasal process (FNP)- and limb-specific CRE recombinase allele that is directed by human AP-2α promoter and enhancer elements. We used the AP-2CRE line in combination with the conditional AP-2α line to produce a new frontonasal knockout (FKO) mutant that lacks AP-2α in the FNP and limbs. FKO mice exhibit shortened snouts and wide-set eyes that become apparent at postnatal day 15. The most prominent defects in FKO snouts are (1) a lack of growth within the frontonasal sutures, and (2) a reduction in the snout vasculature. Additional defects are observed in the FKO nasal bones and sutures, the nasal cavity cartilage and bony projections, and the olfactory epithelium. The characteristics of the FKO mouse model are a unique combination of midfacial growth anomalies, and provide the first evidence that AP-2α is essential for appropriate postnatal craniofacial morphogenesis.

Gross growth and regrowth of sutures: reflections on some personal research.

A series of experiments was performed on young monkeys, rabbits, and turtles to study gross sutural growth of bones. Radiopaque implants in conjunction with serial, direct gross, and indirect radiographic measurements were employed. Differences in growth were observed in the monkey among five facial sutures and also the same suture at different times. Growth was greatest at the zygomaticotemporal suture and least at the premaxillomaxillary suture. In the rabbit, the nasal bone side of the frontonasal suture grew about twice as fast as the frontal bone side. In the turtle shell, the midsagittal suture grew faster than the transverse suture. In all of the animals, the rate of sutural growth decreased with an increase in age. No gross regional growth disturbance was noted after resection of the frontonasal, midpalatine, or transpalatine sutures. The frontonasal suture reformed presumably because of the underlying nasomucoperiosteum, as in a cranial suture, presumably because of the underlying dura. After extirpation of the midpalatine suture with the formation of a complete cleft and despite no underlying membrane, a new suture reformed in an eccentric position in a number of instances. Bone growth at sutures is secondary or compensatory to some other factors.

Correction of coronal suture synostosis using suture and dura mater allografts in rabbits with familial craniosynostosis.

Resynostosis following surgical correction of craniosynostosis is a common clinical correlate. Recent studies suggest that the dura mater is necessary to maintain suture patency. It has also been hypothesized that dura mater from synostotic individuals may provide aberrant biochemical signals to the osteogenic fronts of the calvaria, which result in premature suture fusion and subsequent resynostosis following surgery. This study was designed to test this hypothesis by surgically manipulating the coronal suture and dura mater in rabbits with familial craniosynostosis to prevent postsurgical resynostosis. Craniofacial growth and histomorphometric data were collected from 129 rabbits: 72 normal controls and 57 rabbits with bilateral coronal suture synostosis (15 unoperated on controls; 13 surgical controls; 9 dura mater transplant only; 10 suture transplant only; and 10 suture and dura mater transplant). At 10 days of age, all rabbits had radiopaque amalgam markers placed on either side of the coronal, frontonasal, and anterior lambdoidal sutures. At 25 days of age, 42 synostosed rabbits had a 3 to 5-mm wide coronal suturectomy. Coronal sutures and/or underlying dura mater allografts were harvested from same-aged, wild-type, isohistogenic control rabbits and transplanted onto the dura mater of synostosed host rabbits. Serial radiographs were taken at 10, 25, 42, and 84 days of age, and the suturectomy sites were harvested at 84 days of age in 44 rabbits and serially sectioned for histomorphometric examination. Results revealed that cranial vault growth was significantly (p < .05) improved following surgical release of the fused coronal suture compared with synostosed rabbits who were not operated on but was still significantly different (p < .05) from that of normal control rabbits. By 84 days of age, significant (p < .05) differences were noted in calvarial suture marker separation, cranial vault shape indices, and cranial base angles between rabbits with and without dura mater allografts, probably as a result of resynostosis of the suturectomy site or suture-only allografts. Qualitative histological examination revealed that at 84 days of age rabbits with suture and dura allografts had patent coronal sutures, suture-only allografts had fused coronal sutures with extensive endosteal hyperostosis, dura mater-only allografts had some new bone in the suturectomy site that resembled rudimentary osteogenic fronts, and suturectomy controls had extensive endosteal bone formation and resynostosis of the suturectomy site. Significantly (p < .05) more bone was found in the suturectomy sites of rabbits without dura mater allografts compared with rabbits with dura mater allografts. Results support the initial hypothesis that normal dura mater allografts will maintain suture or suturectomy site patency and allow unrestricted craniofacial growth. However, it is still unclear whether the dura mater from normal rabbits was providing biochemical signals to the transplanted sutures or suturectomy sites or simply acting as a barrier to prevent abnormal biochemical signals from the dura mater of synostosed rabbits from reaching the calvaria. The clinical and therapeutic implications of these procedures are discussed.

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

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.

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

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.

A rabbit model of human familial, nonsyndromic unicoronal suture synostosis. I. Synostotic onset, pathology, and sutural growth patterns.

Poswillo has stated, "The more severe anomalies of the calvaria, such as plagiocephaly, Crouzon [syndrome], and Apert syndrome still defy explanation, in the absence of an appropriate animal system to study" (p. 207). This two-part study reviews data from a recently developed colony of New Zealand white rabbits with familial, nonsyndromic unilateral coronal suture synostosis. Part 1 presents pathological findings and compensatory sutural growth data from 109 normal rabbits and 82 craniosynostotic rabbits from this colony. Synostotic foci, onset, and progression were described in the calvariae from 102 staged (fetal days 21, 25, 27, 33; term = 30 days) fetuses (39 normal, 63 synostosed). Calvarial suture growth patterns from 10 to 126 days of age were assessed from serial radiographs obtained from 89 rabbits (70 normal rabbits and 19 rabbits with unicoronal suture synostosis) with amalgam bone marker implants. Perinatal results revealed that by fetal day 25 the synostotic focal point in synostotic rabbits consistently originated from the endocortical surface of the calvaria in the middle of the coronal suture at a presumed high-tension, interdigitating zone. Histological analysis revealed hyperostotic osteogenic fronts on the affected side compared with the unaffected side. Postnatal sutural growth data revealed a predictable pattern of plagiocephaly (contralateral coronal sutures growing more than ipsilateral sutures and ipsilateral frontonasal and anterior lambdoidal sutures growing more than contralateral sutures), which resulted in early cranial vault deformities and a double "S" shape torquing towards the affected side. The advantages and disadvantages of these rabbits as a model for human familial, nonsyndromic unicoronal suture synostosis are discussed, especially in light of recent cytokine and genetic findings from human craniosynostotic studies.