Suture Autotransplantation and Dural Stripping for Craniosynostosis: A Long-Term Growth Study in Humans.

OBJECTIVE: Craniosynostosis treatment by suture autotransplantation and dura stripping has proven to be successful in animals. When applied clinically, it may reduce operative morbidity and postoperative growth disturbances known to occur after radical remodeling. It may prevent resynostosis, which is known to occur after simple synostostectomy. It may prevent subcutaneous fluid collections known to occur after synostectomy and dura stripping. STUDY DESIGN: Four synostostic infants have been treated using this concept and followed up by computerized scans. The distance between markers on each side of the transplanted sutures (6 in total) has been monitored from 1.5 to 7 years. RESULTS: The transplanted suture areas remained intact, and the sutures remained patent and experienced growth. A fifth patient with similar results was published earlier as a case report. CONCLUSIONS: Suture transplantation and dural stripping should be further studied in future multicenter studies with larger series, comprising syndromic and nonsyndromic synostosis patients.

Ex vivo model of cranial suture morphogenesis and fate.

BACKGROUND/AIMS: Craniosynostosis, the premature fusion of cranial sutures, is a common congenital defect. In vivo models for studying cranial suture biology impose inherent restrictions on tissue accessibility and manipulation. The present study was performed to investigate the utility of the renal capsule assay in overcoming these limitations and providing a reproducible model system for studying cranial suture morphogenesis and fate. MATERIALS AND METHODS: The posterior frontal suture, which fuses physiologically, and the coronal and sagittal sutures, which remain patent, were dissected from postnatal and embryonic mouse calvaria and placed under the renal capsule of syngeneic recipient mice (n = 72 in total). Sutures were harvested from 1-14 days after transplantation for histological and morphometric analysis. Suture transplants were compared with nonmanipulated sutures at equivalent developmental stages. The derivation of cells associated with the growing transplants was analyzed using beta-actin-GFP (green fluorescent protein) transgenic mice. RESULTS: Sutures transplanted under the renal capsule maintained normal suture morphology and fate with the posterior frontal suture fusing and the coronal and sagittal sutures remaining patent. In posterior frontal suture transplants, the fusion process mimicked in vivo suture fusion with a delay of 1-2 days. In comparison to in vivo suture complexes, transplant thickness and trabeculation were significantly increased. In addition, we found that osteoblasts within the growing transplant were derived from the transplant itself rather than the host. CONCLUSION: The renal capsule supports the growth of cranial sutures. In this system transplanted sutures recapitulate the anatomical development and fate (fusion or patency) of cranial sutures in vivo. This model system will facilitate controlled ex vivo manipulations of both embryonic and postnatal sutures.

Neurocranial suture autotransplantation and periosteal dura stripping to provide a passive growth site in craniosynostosis--a case report.

AIM: The behaviour of a neurocranial suture autograft in a plagiocephalic infant is described. PATIENT AND METHODS: In a 7-month-old girl, born with right-sided unicoronal synostosis, part of the left-sided unicoronal suture was transplanted to the right-sided synostosectomy site. Also, in the pathological area, the periosteal 'layer' of the dura was surgically removed. The suture autotransplantation was integrated into the classical concept of radical remodelling, planned in a computer design environment. Growth of the suture was monitored by CT. RESULTS: Suture patency and osseous growth within the autograft could be demonstrated over a 1-year period. CONCLUSION: Neurocranial suture autotransplantation together with the prohibition of fusion-inducing dural signals seems to be a promising technique in the treatment of certain premature synostoses. This warrants a prospective clinical trial.

Unicoronal suture autotransplantation in the rabbit.

INTRODUCTION: Our hypothesis was that a neurocranial suture autograft will, when shielded from dura, grow and be incorporated into the calvarium. METHODS: Growth was monitored by marker separation in three isohistogenic groups of rabbits, between postnatal days 9 and 90. In order to simulate increased neurocapsular expansion force, the left-sided coronal suture of a group of 20 rabbits was immobilised with a resorbable suture on gestational day 25. The other group of 10 rabbits was sham-operated. On postnatal day 9, 10 of the experimental rabbits underwent transplantation of the suture contralateral to the defect resulting from extirpation of the immobilised suture. The transplant was shielded from dural influence by a platinum foil. RESULTS: The growth of the immobilised coronal sutures was severely impaired, and also that of the contralateral unicoronal sutures to a lesser extent. A significant catch-up of growth occurred in the transplanted unicoronal sutures. Overgrowth occurred at the donor sites. CONCLUSION: The results allow us to consider suture transplantation combined with endosteal dura stripping in craniosynostosis surgery.

Experimental study of the frontal sinus development on Goettingen miniature pigs.

According to the literature, the development of the frontal sinus cavity is a result of the active immigration of cells from the ethmoidal complex into the os frontale. This migration theory is in contrast to the operative outcome of Apert's syndrome patients, after fronto-orbital advancement. When a fronto-orbital advancement at the age of a few months is performed in these patients while the frontal suture is yet closed, a sinus developed even the distance between nasal root and frontal bone bing up to 2 cm. In order to study the development of the frontal sinus, an animal study on 12 five-week-old infant Goettingen minipigs (GMP) was conducted, which did not have any clinical or histological signs of a frontal sinus development to investigate the development of the frontal sinus in "orthotopically" transplanted frontal bone with an open frontal suture. A comparison was made to a control group. The macro- and microscopical comparison with a control group revealed that the orthotopical transplants in the occipital bone developed epithelium-lined sinus, beginning from the thirty-fifth week. Based on these histomorphological results, a development scheme for the genesis of the sinus frontalis as a model were drawn.

The faith of a coronal suture grafted onto midline synostosis inducing dura and deprived from tensile stress.

OBJECTIVE: To discuss possible reasons for the synostosis of a coronal suture that was transplanted onto synostosis inducing dura in a scaphocephalic human cranium. DESIGN: Case report. SETTING: Supraregional teaching hospital, center for craniofacial anomalies. PATIENT: A bathmocephalic boy, followed from age 7(1/2) to 26 months. INTERVENTION: Radical synostosectomy, radial osteotomies in the parietal bone with outward fracturing of the barrel staves, and left-sided coronal suture transplantation onto the midline was undertaken at the age of 11 months. METHODS: Computer tomography and clinical follow-up. RESULTS: The sutural graft, initially deprived from tensile stress and quickly exposed to the anomalous dura, turned synostotic in one year. CONCLUSIONS: Both cell signaling and biomechanical theories on calvarial morphogenesis, sutural development, and synostosis can apply. An animal experiment is recommended to test which hypothesis prevails.

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

OBJECTIVE: 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. DESIGN: 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: 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. CONCLUSIONS: 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.

Regeneration of the sagittal suture by GTR and its impact on growth of the cranial vault.

The aim of this study was to investigate the effect of bone grafting, suture transplantation, and guided tissue regeneration (GTR) treatment on healing of craniectomy defects involving the sagittal cranial suture and on the growth of the cranial vault. Fifty 4-week-old rats were included in the study. A 5.0 mm wide trephine defect was created with its midline corresponding to the sagittal cranial suture between the coronal and occipital cranial vault sutures. The animals were randomly allocated to five groups of 10 animals. Group A: The cranial defect was left untreated. Group B: An occipital bone graft was placed into the cranial defect. Group C: A cranial bone graft including a portion of the frontal suture was placed in the cranial defect. Group D: The cerebral and galeal aspect of the defect were covered with an e-PTFE membrane. Group E: The animals were sham-operated, no defect was created. In all animals, two gutta-percha points were placed demarcating the lateral borders of the parietal bones. Histological analysis at 4 months following surgery showed that the untreated cranial defects healed with fibrous connective tissue. The bone-grafted defects healed partially with bone and connective tissue in the periphery of the bone graft. The healing of suture-grafted defects resembled that of the bone-grafted defects, since the transplanted suture became completely obliterated with bone. The membrane-treated defects healed with bone and a suture-like tissue resembling the sagittal suture of the sham-operated controls. Cephalometric measurements demonstrated that membrane-treated and sham-operated control animals exhibited significantly more (P < 0.05) coronal growth (approximately 1.2 mm) than that of the remaining three groups of animals (approximately 0.7 mm). These findings were supported by the craniometry measurements demonstrating that sham-operated control and membrane-treated specimens presented significantly more cranial width than that of the remaining groups of animals (P < 0.05). It can be concluded that complete osseous healing, creation of a new sagittal suture, and increased cranial growth can be achieved by the treatment of craniectomy defects with the GTR technique.

Effect of cranial suture autotransplantation from metopic to coronal suture.

The aim of this study was to determine the outcome of autotransplanting part of the metopic suture to a defect in the coronal suture in a pig model and to explore further the concept of functioning and nonfunctioning recipient sites. The authors harvested 15-mm x 10-mm bone grafts, incorporating a part of the metopic suture, in 10 Yorkshire pigs under general anesthesia. The authors immediately autotransplanted the grafts to a surgically created defect along the line of the coronal suture. Both donor and graft were either covered with pericranium or left bare. Radiopaque titanium markers were inserted to assess growth 1) of the transplanted suture; 2) across both coronal sutures; and 3) across the metopic suture. Serial radiographs were taken immediately after surgery and at 3-week intervals. The pigs were then killed at 21 weeks. The cranium was harvested, and blocks of donor site and graft were taken, incorporating the embedded titanium markers. Histologic analysis confirmed graft take in all pigs. All grafts continued to function as active cranial sutures with no growth disturbance compared with the contralateral coronal suture (P = 0.953). There was also regeneration of the donor defect, as confirmed by histologic analysis, with no growth disturbance across the metopic suture (P = 0.972). Pericranium did not alter graft take or subsequent growth (P = 0.964). However, pericranium resulted in a much smaller defect (P = 0.045). These results show that after autotransplanting a cranial suture to replace another cranial suture, the graft continues to grow and function as a cranial suture to meet the functional demands of the new recipient site. Pericranium has a significant effect on calvarial regeneration but does not affect cranial suture autotransplantation.

Coronal suture transplantation to correct fronto-orbital constriction in metopic synostosis.

Surgical correction of non-syndromatic trigonocephaly is generally considered to be ideally performed at the age of 3 to 6 months. Conventional procedures include flattening of the forehead and straightening of the supraorbital bar by multiple osteotomies. Hypotelorbitism is generally not addressed. Long-term follow-up studies have shown that the orbital configuration does not improve spontaneously. Recently, some centres have proposed simultaneous correction of hypotelorbitism by a median widening osteotomy in the supraorbital bar. In our opinion, these procedures are indicated for patients over the age of 2 years, since further transverse growth is restricted by the plates and bone grafts in the glabella region. A procedure is presented by which both the initial and presumably the long-term correction of the transverse constriction in the forehead, glabella and orbital region is safeguarded by midline transplantation of a suitable piece of coronal sutural area.

In the absence of periosteum, transplanted fetal and neonatal rat coronal sutures resist osseous obliteration.

Normal craniofacial development depends on expansion of the cranial vault by growth at the sutures. Inappropriate development of the sutures leads to global disruption of patterns of craniofacial growth. Tissue interactions between dura mater and suture matrix play a critical role in the phenotypic maintenance of cranial sutures. However, the function of the periosteum in this process remains under-reported and controversial. To examine the contribution of periosteum in maintaining the patency of coronal sutures, fetal and neonatal rat coronal sutures were transplanted to surgically created defects in adult rat host parietal bones. These sutures were examined for their ability to persist in the host milieu in the presence and absence of both donor and host periosteum. This study established that removal of both host and transplant periosteum, unlike removal of dura mater, did not lead to obliteration of either fetal or neonatal sutures. Thus, periosteum and dura mater are nonequivalent tissues with respect to influence on suture patency.

Tissue interactions with underlying dura mater inhibit osseous obliteration of developing cranial sutures.

Cranial sutures play a critical role in calvarial morphogenesis, serving as growth centers during skull development. Both biomechanical tensile forces originating in the cranial base and biochemical factors present in dura mater have been postulated as determinants of suture morphogenesis and patency. A rat transplant model free of the putative biomechanical influence of the dura and cranial base was used to investigate the role of the dura mater in both the initial morphogenesis and maintenance of sutures during skull growth. Day 19 fetal presumptive (F19) and day 1 neonatal differentiated (N1) coronal sutures, including associated frontal and parietal bones, were transplanted with or without underlying dura mater to the center of adult parietal bones. After 1, 2, and 3 weeks, transplanted tissues were examined histologically and histomorphometrically to determine whether sutures formed and whether they were obliterated by ossification in the absence of dura mater. Both F19 and N1 sutures remained patent for 2 weeks either in the presence or the absence of transplant dura mater. However, at 3 weeks, in the absence of transplant dura mater, sutures were obliterated by bone, while in the presence of dura mater sutures resisted ossification, demonstrating an essential requirement for interactions with the transplant dura mater in maintaining functional sutures. Both F19 and N1 transplants showed comparable bone growth (cross-sectional surface area), regardless of the presence of transplant dura mater. These experiments suggest that tissue interactions of a biochemical nature, rather than biomechanical forces generated through the cranial base, are required to maintain the suture as a non-ossified growth center. Furthermore, while the presence of dura mater was essential for maintenance of suture patency, fetal dura mater was not required for initial suture formation.

Sutural growth.

As the skull develops, the tissue of the coronal and sagittal sutures (serrated sutures) assumes a specific structure which in part is practically identical to that of a gomphosis joint and may therefore be regarded as a 'multigomphosis'. The nature of this structure justifies the assumption that it has to resist mechanical forces exerted on the suture. The results of transplantation experiments with portions of sutures suggest that the sutural structures are determined hereditarily, but that environmental factors are required for these qualities to manifest themselves.