Frontonasal Suture Research Articles

Some Factors Related to Experimental Snout Growth

This is a review and synthesis of several different studies over a 25-year period on growth of the rabbit snout. Included are growth of the nasal bone region, cellular activity of the cartilaginous nasal septum, growth at the frontonasal suture, growth of the snout after resection of the frontonasal suture, and growth of the snout after resection of the cartilaginous nasal septum in both young and adult rabbits. Each experiment contributed different knowledge to factors important in rabbit snout growth. The frontonasal suture is a site of rapid growth, as much as 1 cm in 4 weeks. However, after extirpation of the frontonasal suture, growth of the snout was not altered. Therefore, it was concluded that the frontonasal suture is a secondary and not a primary site of growth. After resection of the cartilaginous nasal septum in young rabbits, the snout became snubbed. This was not true in the adult rabbit, which maintained its usual length after resection of the nasal septum.

An Automatic Recognition of the Frontal Sinus in X-Ray Images of Skull

In the present paper, a procedure is developed for fully automatic recognition of the frontal sinus in cranial radiographs. An X-ray image of a whole skull is required at the input of the procedure, which consists of three subsequent steps: the selection of a rectangular region of interest, containing the sinus; detection of the line of brow ridges; and fronto-nasal suture, detection of the borders of the frontal sinus. The recognition algorithm is based on a method of connectivity-preserving thresholding, introduced in the present study, and on watersheds from markers. Totally, 50 X-ray images have been analyzed. The frontal sinus borders were recognized correctly in 41 cases.

Three-dimensional evaluation of surgically assisted implant bone-borne rapid maxillary expansion: A pilot study

The purpose of this study was to evaluate 3-dimensional changes in dental, alveolar, and skeletal structures caused by a bone-borne implant-supported rapid maxillary expansion device (Dresden distractor). Axial computed tomography scans of 10 patients (mean age, 25.3 years) treated with the Dresden distractor were examined. Scans were taken immediately before and 9 months after expansion. Distances in all 3 dimensions were calculated for 38 skeletal, alveolar, and dental landmarks with respect to the reference point ELSA (point equidistant to both foramina spinosa). In the transverse dimension, a V-shaped opening of the suture was shown; the greatest amount of opening was anteriorly directed, with convergence of the suture opening in the posterior aspect of the palate. The expansion of the maxillary dental arch showed a V pattern similar to the opening of the suture. In the frontal view, expansion caused a wedge-shaped opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. The alveolar processes tipped buccally (9.9 degrees to 13.3 degrees) as did the molars (2.5 degrees to 3.5 degrees) and the premolars (3.0 degrees to 3.9 degrees). Less tipping of teeth compared with skeletal tipping (about 6 degrees to 9 degrees less) is related to the torque effect of the fixed appliance. The Dresden distractor is a minimally invasive bone-borne expansion appliance that protects teeth by inducing more skeletal than dental changes. This might be a precondition for stable postsurgical occlusion.

Landmark‐based shape analysis of the archaic Homo calvarium from Ceprano (Italy)

The Ceprano calvarium represents one of the most important sources of information about both the dynamics of the earliest hominid dispersal toward Europe and the evolution of the genus Homo in the early-to-middle Pleistocene. In this paper, the midsagittal vault profile and the 3D frontal bone morphology of Ceprano are investigated comparatively, using landmark coordinates and Procrustes superimposition. In fact, despite the fact that the skull appears partially distorted by diagenetic pressures (thus precluding a comprehensive landmark-based analysis), some aspects of the overall morphology are suitable for consideration in terms of geometric morphometrics. The midsagittal profile shows an archaic shape, comparable with the H. ergaster/erectus range of variation because of the fronto-parietal flattening, the development of the supraorbital and nuchal structures, and the occurrence of a slightly larger occipital bone. By contrast, the frontal bone displays a derived 3D shape that, mostly because of the widening of the frontal squama, appears comparable with the Afro-European variation of the Middle Pleistocene (i.e., H. heidelbergensis/rhodesiensis). Taking into account the unique morphological pattern displayed by Ceprano, its role as a link between early Homo and the Middle Pleistocene populations of Europe and Africa is not falsified. Thus, when aspects of the Ceprano's morphology are described within the analytical framework provided by geometric morphometrics, the relationships between Ceprano and the subsequent Afro-European fossil record are emphasized, suggesting the occurrence of an ancestral stock of H. heidelbergensis/rhodesiensis that is properly represented by the Italian specimen.

Osteologia craniana de Platalea ajaja (Linnaeus) (Aves, Ciconiiformes), comparada com outras espécies de Threskiornithidae

Platalea ajaja (Linnaeus, 1758) pertence Threskiornithidae (curicacas e afins e colhereiros), Threskiornithoidea, Ciconiiformes. Threskiornithidae (colhereiros, curicacas e afins) são subdivididos em dois grupos: Threskiornithinae que compreende curicacas e afins, caracteriza-se por seus representantes possuírem um bico longo, estreito e curvo, ao passo que Plataleinae inclui os colhereiros, que apresentam bico longo e achatado na ponta. O presente trabalho teve como objetivo descrever a osteologia craniana de P. ajaja (Plataleinae) e comparar com outras espécies pertencentes à Threskiornithinae. As espécies utilizadas para tal comparação foram: Mesembrinibis cayennensis (Gmelin, 1789), Phimosus infuscatus (Lichteinstein, 1823), Theristicus caudatus (Boddaert, 1783) e Plegadis chivi (Vieillot, 1817). Outras espécies pertencentes a ordem Ciconiiformes também foram utilizadas para comparação. A partir do presente estudo, observou-se que P. ajaja (Plataleinae) apresenta como características que a separa dos Threskiornithinae: 1) sutura frontonasal conspícua; 2) processo supra-orbital do osso lacrimal curto; 3) maxila superior achatada dorsoventralmente, sendo alargada na extremidade, tomando forma de uma colher; 4) narina curta e de forma oval; e 5) processo retroarticular curto. Entretanto, são necessários estudos osteológicos que contemplem as outras espécies da família, bem como um estudo filogenético do grupo para maior compreensão das relações existentes entre os Threskiornithidae.

CT-based description and phyletic evaluation of the archaic human calvarium from Ceprano, Italy

The discovery in 1994, of a fossilized human calvarium near Ceprano, Italy, dated about 800-900 thousand years before present, opened a new page for the study of human evolution in Europe. It extended the continental fossil record over the boundary between Early and Middle Pleistocene for the first time and revealed the cranial morphology of humans that where probably ancestral to both Neanderthals and modern Homo sapiens. A tomographic analysis of the Italian specimen is reported here in order to describe size and shape, vascular traces, and other features of the endocranium, as well as some relevant ectocranial traits (particularly of the frontal region). Our results show that the Ceprano calvarium displays plesiomorphies shared by early Homo taxa, involving a general archaic phenotype. At the same time, the presence of some derived features suggests a phylogenetic relationship with the populations referred to the subsequent polymorphic species H. heidelbergensis. The morphology of the supraorbital structures is different from the double-arched browridge of the African H. ergaster, while its superior shape shows similarities with African Middle Pleistocene specimens (Bodo, Kabwe). In contrast, the relationship between supraorbital torus and frontal squama points to an archaic pattern of the relationship between face and vault, associated to moderately narrow frontal lobes and limited development of the upper parietal areas. Despite a nonderived endocranial shape, the increase of cranial capacity (related to a general endocranial widening) and the probable absence of a clear occipital projection also suggest an evolutionary independence from the Asian H. erectus lineage. This analysis therefore supports the conclusion that the Ceprano calvarium represents the best available candidate for the ancestral phenotype of the cranial variation observed among Middle Pleistocene fossil samples in Africa and Europe. Nevertheless, a proper taxonomic interpretation of this crucial specimen remains puzzling.

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.

Tgf-beta1, Tgf-beta2, Tgf-beta3 and Msx2 expression is elevated during frontonasal suture morphogenesis and during active postnatal facial growth.

It is hypothesized that regulation of facial suture morphogenesis is similar to that of cranial sutures, with expression of similar regulatory molecules, governing suture formation and patency. The present study was designed to characterize the morphology of the frontonasal (FN) suture of the rat at different developmental stages and to investigate the presence and temporal-spatial expression of transforming growth factor-beta 1 (Tgf-beta1), Tgf-beta2, Tgf-beta3 and Msx2 mRNA within these structures. The Department of Biomedical Sciences at Texas A&M University System Health Science Center, Baylor College of Dentistry, Dallas, TX USA. Histological sections and RNA isolated from FN suture tissues of Sprague-Dawley rats, aged embryonic day 16 through postnatal day 20. Sections were examined after immunohistochemical staining. Gene expression was determined by densitometric analysis of RT-PCR products run on agarose gels. FN sutures develop slightly later than cranial sutures and show increased complexity over time when compared to cranial sutures. FN sutures were closely associated with the nasal capsular cartilage, with intervening layers of perichondrium and periosteum. The pattern of expression of Tgf-betas within the FN suture tissues was similar to that seen in the cranial sutures. However, mRNA and protein of the Tgf-betas were differentially expressed over time compared to cranial sutures. In FN sutures, Tgf-beta mRNA levels were elevated both during the period of suture morphogenesis and during active bone growth from the suture in the early postnatal period. Msx2 mRNA expression was elevated in both the prenatal and postnatal periods, similar to Tgf-beta mRNA expression. Tgf-beta and Msx2 are present in facial sutures similar to cranial sutures, but are differentially expressed over time, perhaps reflecting different bone growth rates from these sutures.

Diagnosis of a captive-bolt injury in a skull extremely destroyed by fire

The authors report on a combined suicide of a 71-year-old farmer who fired a shot to his forehead with a livestock stunner before burning himself. As the fire was fueled by a pile of firewood it burnt for many hours, thus, causing subtotal incineration of the body. The remaining bones were calcined and reduced to a residual mass of only 3 kg. In spite of the extreme destruction, a circular bone defect corresponding to the site where the captive-bolt had entered the skull could be identified in the frontal squama. The example of this suicide is used to illustrate the problems of distinguishing between mechanical and thermal fractures. As expected, the attempted isolation and amplification of both nuclear and mitochondrial DNA for the purpose of identification was not successful.

A newHomo erectus cranium from Sangiran, Java

A newHomo erectus cranium was found on May 18, 1993 by Budi, a local farmer, at Sangiran. It dates from the Middle Pucangan Formation approximately 1.6–1.8 mya. The braincase is essentially complete and as is most of the face. The vault has the typicalH. erectus gable shape. There is a clear sagittal ridge beginning below the middle of the frontal squama and running to mid-parietal. Parasagittal ridges are rounded angulations halfway up the parietals, and coincide with poorly marked temporal lines. In all measurements, this skull is longer and consistently narrower than Trinil. It is chronologically and morphologically similar to the famousH. erectus skull from east Africa, KNMER-3733. Although existing much older, this new specimen is what one would expect a female counterpart to Sangiran 17 to look like.

Prospective anthropometric analysis of sagittal orbital-globe relationship following fronto-orbital advancement in childhood.

Fronto-orbital advancement is a common procedure for correction of supraorbital retrusion in patients with coronal craniosynostosis. The aim of this study was two-fold: to quantitate change in the sagittal orbital-globe relationship following fronto-orbital advancement in childhood and to determine the ratio of skeletal-to-soft tissue movement. Soft-tissue points on the orbital rim, orbitale superius (os), orbitale laterale (ol), orbitale inferius (oi), and nasion (n), referenced to apex corneae (ac), were measured preoperatively and postoperatively by a custom-made anthropometer. Intraoperative bony advancement was measured with a caliper. Patients were selected with uniform advancement at the fronto-nasal suture and laterally at the mortise and tenon. Fifteen patients with syndromic craniosynostosis were included in the study (six male, nine female): Apert (n = 2), Crouzon (n = 5), Pfeiffer (n = 4), Saethre-Chotzen (n = 3), and Boston type (n = 1). Average age at operation was 8.7 years (range, 4.5 to 10.5 years). Age, sex, method of fixation, postoperative interval, diagnosis, and skeletal movement were analyzed for possible effect on the magnitude of soft-tissue advancement. Average intraoperative skeletal advancement was 12.1 mm, and average postoperative soft-tissue movement was 10.3 mm (p < 0.001), measured at the midpoint of the supraorbital rims (os). The soft tissue: skeletal movement ratio was 0.9:1. Os was the only point at which soft-tissue advancement could be predicted (Spearman's rank correlation coefficient = 0.67); soft-tissue changes at ol, oi, and n were unpredictable. Skeletal movement was the only determinant of soft-tissue advancement of all variables tested, i.e., diagnosis, age, sex, previous fronto-orbital advancement, and wire versus plate fixation. We make recommendations for calculating the magnitude of fronto-orbital advancement, based on preoperative anthropometry and a soft-to-hard tissue advancement factor.

Thin-plate spline analysis of the cranial base in subjects with Class III malocclusion.

The role of the cranial base in the emergence of Class III malocclusion is not fully understood. This study determines deformations that contribute to a Class III cranial base morphology, employing thin-plate spline analysis on lateral cephalographs. A total of 73 children of European-American descent aged between 5 and 11 years of age with Class III malocclusion were compared with an equivalent group of subjects with a normal, untreated, Class I molar occlusion. The cephalographs were traced, checked and subdivided into seven age- and sex-matched groups. Thirteen points on the cranial base were identified and digitized. The datasets were scaled to an equivalent size, and statistical analysis indicated significant differences between average Class I and Class III cranial base morphologies for each group. Thin-plate spline analysis indicated that both affine (uniform) and non-affine transformations contribute toward the total spline for each average cranial base morphology at each age group analysed. For non-affine transformations, Partial warps 10, 8 and 7 had high magnitudes, indicating large-scale deformations affecting Bolton point, basion, pterygo-maxillare, Ricketts' point and articulare. In contrast, high eigenvalues associated with Partial warps 1-3, indicating localized shape changes, were found at tuberculum sellae, sella, and the frontonasomaxillary suture. It is concluded that large spatial-scale deformations affect the occipital complex of the cranial base and sphenoidal region, in combination with localized distortions at the frontonasal suture. These deformations may contribute to reduced orthocephalization or deficient flattening of the cranial base antero-posteriorly that, in turn, leads to the formation of a Class III malocclusion.

TGF-β1, TGF-β2, and TGF-β3 Exhibit Distinct Patterns of Expression During Cranial Suture Formation and Obliteration In Vivo and In Vitro

Cranial sutures function as bone growth centers while themselves remaining unossified. Rat frontonasal sutures become obliterated by neonatal day 21 (N21), while coronal sutures do not fuse over the life of the animal. Coronal sutures induced to undergo osseous obliteration in vitro after removal of the dura mater were found to require soluble, heparin-binding factors present in dura mater to resist osseous obliteration. Transforming growth factor beta 1 (TGF-beta 1), beta 2, and beta 3, heparin-binding factors known to regulate bone cell proliferation and differentiation, were considered likely candidates. The presence and distribution of these factors in calvarial tissues both in vivo and in vitro were established by immunohistochemical analysis, while reverse transcription followed by polymerase chain reaction (RT/PCR) was employed to determine the presence of transcripts for these factors in mRNA isolated from microdissected dura mater. Results indicated that the presence of TGF-beta 1 and TGF-beta 2 were associated with developing coronal and frontonasal sutures, and that the continued presence of these factors was associated with osseous obliteration of the frontonasal suture. However, increased TGF-beta 3 immunoreactivity was associated with the coronal suture remaining unossified. RT/PCR demonstrated the presence of transcripts for TGF-beta 1, beta 2, and beta 3 in dural tissues isolated from rat calvaria. These data support the notion of a role for TGF-beta s in regulating cranial suture morphogenesis and establish the in vitro model as a valid system for examining mechanisms by which growth factors regulate both suture morphogenesis and bone growth at the suture site.

Endocranial hyperostosis in Sangiran 2, Gibraltar 1, and Shanidar 5.

Sangiran hominid 2 (S-2), Gibraltar hominid 1 (G-1), and Shanidar hominid 5 (SH-5) exhibit previously undescribed bilateral, paramedian hyperostosis of the endocranial frontal squama that spares the frontal crest, sagittal sinus, and ectocranial surface. The hyperostosis is localized to the frontal (usually the middle third) and parietal and is consistent with a diagnosis of hyperostosis calvaria interna (HCI), inclusive of hyperostosis frontalis interna. The hyperostosis in these specimens is compared to fossil hominids from Indonesia and Europe and to modern human cases of HCI. The three cases of HCI reported here documented the existence and frequency of HCI in fossil hominids and push the antiquity of the disease back to nearly 1.5 million years. The relatively great incidence of HCI in fossil hominids adds another confounding factor to the problematical issue of the taxonomic significance of cranial vault thickness.

Development of plagiocephaly in rabbits with unicoronal synostosis.

Human unicoronal synostosis results in plagiocephaly of the cranial vault due to predictable compensatory growth patterns of the contralateral coronal, sagittal, and ipsilateral squamosal sutures. The present study describes the development of plagiocephaly and tests compensatory growth predictions in a naturally occurring rabbit model of uncorrected unicoronal synostosis. Cranial vault and sutural growth data were collected from serial x-ray films in 70 normal rabbits and 19 rabbits with congenital unicoronal synostosis from 1.5 to 18 weeks of age. One-way analysis of variance results revealed that rabbits with unicoronal synostosis had significant (p < 0.05) growth inhibition at both coronal sutures and the contralateral frontonasal suture and a significantly wider (p < 0.05) cranial vault compared to controls. Paired Student's t-tests between affected and unaffected sides of the vault in rabbits with synostosis revealed significant (p < 0.05) asymmetry, with ipsilateral coronal sutures growing less than contralateral ones. Gross qualitative examination of the adult brains revealed severe asymmetry and anteroposterior reduction on the ipsilateral side. These results demonstrate that this congenital rabbit model effectively simulates human cranial vault growth predictions from unicoronal synostosis and produces a plagiocephalic morphology.

Frontonasal suture expansion in the rabbit using titanium screws

Purpose: This study investigated the ability to use titanium screws to provide stable skeletal points in the growing craniofacial region of the rabbit for suture expansion. These screws provided sites for direct application of external forces to alter growth and anatomic form. Material and Methods: Twenty-one rabbits (30 days old) were divided into three groups: control (n = 9), experimental (n = 9), and sham (n = 3). Four four-holed AO/ASIF commercially pure titanium craniofacial plates were contoured into an L-shape with a 90° angle at the midpoint. The plates were placed bilaterally in the frontal and nasal bone sites and secured with 2.0-mm diameter, 4-mm long, commercially pure titanium screws in both the sham and experimental groups. After 4 weeks of healing, a spring mechanism with a distraction force of 55 g was activated between ipsilateral plates and across the frontonasal sutures bilaterally in the experimental group for 5 weeks. No force was applied between the plates in the sham group. A preliminary evaluation of the bone-implant interface and the changes in the sutures was done histologically. Morphologic changes were measured using cephalometric radiographs and direct anatomic measurements. Results: The experimental group showed a significant increase in growth across the frontonasal suture in comparison with the sham group ( P < .05). In addition, an increase in the length of the nasal and frontal bones in the expanded group was observed in comparison with the control and sham groups ( P < .05). Histologically, a mixture of woven and lamellar bone was seen in the suture region and lamellar bone was seen in the screw-bone interface. Conclusion: This study indicates that titanium screws in the developing rabbit skull can provide stable sites for the direct application of external forces, producing secondary changes in skeletal mrophology. This laboratory model provides a useful system for the further study of growth modification using such external mechanical forces.

Rhinoplasty with nasal bone disarticulation to deepen the nasofrontal groove: Experimental and clinical results

Deepening of the nasofrontal groove is considered a fiddly task. The unwonted chisel ostectomy technique (Skoog, 1974; McCarthy, 1990; Aiach and Levignac, 1991) was therefore modified and evaluated both experimentally and clinically. The hump is removed in one piece together with the nasal bones up to the horizontal part of the frontonasal suture. To accomplish this, the reduction osteotomy has to be performed in a wave line fashion. The depth of resection in the sellion area depends upon the aesthetic planning. In cases with most severe hypertrophy, the osteotome enters the vertical frontonasal suture behind the nasal bones and in front of the nasal spine of the frontal bone. The nasal bones are disarticulated with a levering movement. Cadaver studies demonstrate the safety of the technique: no fracture lines were detected in the frontal process of the maxilla, ethmoid, frontal or lacrimal bones, by either clinical inspection, or by standardised radiological examination. The clinical cases show a convincing outcome.

Angles among main cranial sutures in Japanese

To examine a relation of angles among the coronal, sagittal and lambdoid sutures to the size of the calvaria as well as to the remains of the metopic suture, 158 adult Japanese calvae or calottes were observed. The calvae used consisted of four groups: group M composed of 74 male calvae without the metopic suture; group F, of 41 female calvae without the same suture; group Un, of 27 sex-unknown calvae without the same suture; and group Um, of 16 sex-unknown calvae with the same suture. The angles among the sutures were measured at both bregma and lambda. The size of the calvaria was represented by bistephanic arc and breadth (distance between the stephanions), and by parietal sagittal arc and chord (distance from the bregma to the lambda). Results obtained were as follows. The distances both between the stephanions and from the bregma to the lambda were larger in M than in F, though these distances in M, F and Un were much the same as those in Um. The bistephanic index (breadth/arc) was higher in Um than in F, whereas the sagittal parietal indices (arc/chrod) in M, F and Um were similar to one another. Apical angle of the frontal squama was larger in M than in F, and was larger in Um than in M and F. However, apical angle of the occipital squama showed no difference among M, F and Um.(ABSTRACT TRUNCATED AT 250 WORDS)

Histomorphological analysis of the effect of rigid fixation on growing sutures in the rabbit

The effect of internal rigid fixation (IRF) on bone growth was studied in an experimental model set up in the rabbit. The frontonasal suture of the right side was surgically bridged by a microplate. As reference for bone growth, four screws were placed symmetrically in the four bony segments including the frontonasal suture on both sides. The suture development was followed dynamically for 40 days on the basis of the position of the screws established radiographically. The rate of bone formation along the sutural bones was evaluated by means of the tetracycline labelling technique. The structure of the newly formed bone and its degree of mineralization were respectively analysed under polarized light and with microradiography. It was demonstrated that IRF prevents growth of the sutural membrane but not of the osteogenic process; as a consequence the constrained sutures soon undergo synostosis. This fact must be taken into consideration when IRF is employed in children in order to avoid delayed removal of the plate irreversibly stopping the growth of the constrained suture.