Age-Dependent Closure of Bony Defects after Frontal Orbital Advancement

Craniofacial growth in patients with FGFR3Pro250Arg mutation after fronto-orbital advancement in infancy

BACKGROUND

The facial features of children with FGFR3Pro250Arg mutation (Muenke syndrome) differ from those with the other eponymous craniosynostotic disorders. We documented midfacial growth and position of the forehead after fronto-orbital advancement (FOA) in patients with the FGFR3 mutation.

METHODS

We retrospectively reviewed all patients who had an FGFR3Pro250Arg mutation and craniosynostosis. Only patients who had FOA in infancy or early childhood were included. The clinical records were evaluated for type of sutural fusion; midfacial hypoplasia and other clinical data, including age at operation; type of procedures and fixation (wire vs resorbable plate); frequency of frontal readvancement, forehead augmentation, midfacial advancement; and complications. Preoperative and postoperative sagittal orbital-globe relationship was measured by direct anthropometry. Outcome of FOA was graded according to the Whittaker classification as category I, no revision; category II, minor revisions, that is, foreheadplasty; category III, alternative bony work; category IV; redo of initial procedure (ie, secondary FOA). Midfacial position was determined by clinical examination and lateral cephalometry.

RESULTS

A total of 21 study patients with Muenke syndrome (8 males and 13 females) were analyzed. The types of craniosynostosis were bilateral coronal (n=15), of which 3 also had concurrent sagittal fusion, and unilateral coronal (n=5). Two patients had early endoscopic suturectomy, but later required FOA. Mean age at FOA was 22.9 months (range, 3-128 months). Secondary FOA was necessary in 40% of patients (n=8), and secondary foreheadplasty in 25% (n=5) of patients. No frontal revisions were needed in the remaining 35% of patients (n=7). Mean age at initial FOA was significantly younger in the group requiring repeat FOA or foreheadplasty compared with patients who did not require revision (P<0.05). Location of synostosis, type of fixation, and bone grafting did not significantly affect the need for revision. Only 30% (n=6) of patients developed midfacial retrusion.

CONCLUSIONS

The frequency of frontal revision in patients with Muenke syndrome who had FOA in infancy and early childhood is lower than previously reported. Age at forehead advancement inversely correlated with the incidence of relapse and need for secondary frontal procedures. Midfacial retrusion is relatively uncommon in FGFR3Pro250Arg patients.

Cranial vault remodeling for sagittal craniosynostosis in older children

Object

Sagittal craniosynostosis is the most common form of craniosynostosis and is commonly treated within the first year of life. Optimal treatment of patients older than 1 year of age is not well characterized. The authors reviewed cases of sagittal craniosynostosis involving patients who were treated surgically at their institution when they were older than 1 year in order to determine the rate of intracranial hypertension (ICH), potential to develop nonhealing cranial defects, and the need for various surgical procedures to treat the more mature phenotype.

Methods

A retrospective chart review was conducted of all cases in the Children's Hospital of Pittsburgh Neurosurgery Database involving patients who underwent cranial vault remodeling for scaphocephaly after 1 year of age between October 2000 and December 2010.

Results

Ten patients were identified who met the inclusion criteria. Five patients underwent anterior two-thirds cranial vault remodeling procedures, 3 patients underwent posterior vault remodeling, and 2 patients underwent 2-staged total vault remodeling. All patients had improved head shapes, and mean cephalic indices improved from 65.4 to 69.1 (p = 0.05). Six patients exhibited signs of ICH. No patients with more than 3 months of follow-up exhibited palpable calvarial defects.

Conclusions

Patients with sagittal synostosis treated after 1 year of age demonstrate increased rates of ICH, warranting diligent evaluations and surveillance to detect it; rarely develop clinically significant cranial defects if appropriate bone grafting is performed at the time of surgery; and achieve acceptable improvements in head shape.

Exchange cranioplasty using autologous calvarial particulate bone graft effectively repairs large cranial defects

BACKGROUND

Autogenous particulate cranial bone graft has been proven to be effective for inlay cranioplasty but does not provide structural contour. This limitation can be overcome using an exchange cranioplasty technique. This study probes the effectiveness of this method for large (>5 cm(2)) or complicated cranial defects.

METHODS

The authors conducted a retrospective review of patients managed with autologous exchange cranioplasty between 2005 and 2010. Full-thickness calvarial bone was removed from the intact cranium; particulate bone graft was harvested from the graft endocortex or ectocortex of intact cranium. The original defect was repaired with the full-thickness graft and the donor site was covered with particulate graft. Patient records were reviewed for age at cranioplasty, operative indication, size and location of defect, operative time, blood loss, and length of follow-up. Outcome variables included complications, osseous defects, and need for revision cranioplasty.

RESULTS

Twenty patients underwent exchange cranioplasty at a mean age of 8.3 ± 6.2 years. Average values for the group included length of procedure, 4.7 hours; estimated blood loss, 288 ml; hospital stay, 3.1 days; and follow-up, 1.57 years (range, 24 weeks to 3.7 years). Eighty-five percent of patients underwent postoperative computed tomographic scanning to document healing. Fifteen patients had complete healing; five patients had residual bone defects (four by computed tomography and palpation, and one by computed tomography only). The cranial defect area decreased 96 percent on average from a preoperative mean of 85.2 cm(2) to a postoperative combined defect size (donor plus recipient) of 3.3 cm(2).

CONCLUSION

Autologous exchange cranioplasty using particulate bone graft is safe and highly effective for reconstructing even large cranial defects.

Differential expression of sclerostin in adult and juvenile mouse calvariae

BACKGROUND

An understanding of the molecular mechanisms controlling bone formation is central to skeletal tissue engineering efforts. The observation that immature animals are able to heal calvarial defects while adult animals are not has proven to be a useful tool for examining these mechanisms. Thus, the authors compared expression of sclerostin, a bone inhibitor, between the calvariae of juvenile and adult mice.

METHODS

Parietal bone was harvested from juvenile (6-day-old; n = 20) and adult (60-day-old; n = 20) mice. Sclerostin transcript and protein levels were compared between the parietal bone of juvenile and adult mice using polymerase chain reaction, Western blotting, and immunohistochemistry. Finally, osteoblasts from the parietal bone of juvenile and adult mice were harvested and cultured under osteogenic differentiation conditions with and without recombinant sclerostin (200 ng/ml). Terminal osteogenic differentiation was assessed at 21 days with alizarin red staining.

RESULTS

Polymerase chain reaction, Western blot analysis, and immunohistochemistry all confirmed greater expression of sclerostin in the parietal bone of adult mice when compared with that of juvenile mice. Osteoblasts, whether from juvenile or adult parietal bones, demonstrated reduced capacity for osteogenic differentiation when exposed to recombinant sclerostin.

CONCLUSIONS

Given the role of sclerostin in inhibiting bone formation, the authors' findings suggest that differences in expression levels of sclerostin may play a role in the differential regenerative capacity of calvariae from juvenile and adult animals. These findings suggest it as a potential target to abrogate in future tissue engineering studies.

Global age-dependent differences in gene expression in response to calvarial injury

Children less than 2 years of age are capable of healing large calvarial defects, whereas adults have been found to lack this endogenous ability. In this study, we used microarray analysis to compare genomewide expression patterns during active regeneration after injury with calvaria in skeletally immature and mature mice. Parietal bone defects were created in 6-day-old (juvenile) and 60-day-old (adult) mice using a 4-mm trephine bit (n = 20 mice per age group). The calvarial disc was removed, leaving the underlying dura mater intact. Two weeks after injury, the region of regeneration with the underlying dura mater was harvested, and RNA was extracted for microarray analysis. The 25 most differentially upregulated genes in juvenile regenerates compared with adults were listed, as well as selected bone-related genes. In addition, QRT-PCR confirmation of specific genes was performed for validation. Juvenile regenerates expressed significantly greater amounts of BMP-2, -4, -7, as well as FGF-2 and its receptor FGFR-1. Various other growth factors were also noted to be upregulated, including IGF-2 and Ptn. This corresponded with the increased expression of markers for osteogenic differentiation of Sparc and Oc. Markers of osteoclast activity, Acp5, Ctsk, and Mmp2, were noted to be greater in juvenile regenerates compared with adults. The observation of Mmp14 upregulation, however, highlights the importance of balanced osteoclast-mediated bone resorption for ultimate healing. The 2 most differentially regulated genes, transthyretin (Ttr) and prostaglandin D2 synthase (Ptgds), highlight the potential role of retinoic acid signaling and the prostaglandin axis on skeletal regeneration. These findings underscore the multitude of biomolecular mechanisms at play, allowing juvenile calvaria to heal after injury. The identification of various growth factors and cytokines involved also suggests novel therapeutic strategies for tissue-engineering purposes.

Growth of the orbit after frontoorbital advancement using nonrigid suture vs rigid plate fixation technique

PURPOSE

To demonstrate whether a measurable difference occurs on the growth of the orbit when using 2 forms of stabilization of the supra-orbital rim after upper orbital osteotomy in children with craniosynostosis. The 2 methods of fixation include sutures providing nonrigid fixation and titanium or resorbable osteosynthesis plates.

PATIENTS AND METHODS

In this prospective randomized study, the influence of the mentioned fixation materials was analyzed in a tertiary care center (university hospital). Sixteen consecutive children with craniosynostoses (trigonocephaly, brachycephaly, plagiocephaly) were included. All patients underwent bilateral frontoorbital advancement surgery. In 8 patients each, the fixation of the mobilized and reshaped supraorbital rim was carried out using either miniplates or sutures, resulting in a rigid or nonrigid fixation. By means of computed tomography scans taken preoperatively (mean age, 8months) and postoperatively (mean age, 6.5years), the development of the orbit was measured using the anterior interorbital distance, lateral orbital distance, medial orbital-wall length, lateral orbital-wall length, and medial orbital-wall protrusion. The results were compared to norm values and statistically evaluated.

RESULT

In all patients, a long-term improvement of the orbit was achieved with absolute distances staying below norm values. The choice of the fixation material was of minor importance.

CONCLUSION

Sutures providing nonrigid fixation of bone flaps seem to be feasible in reaching the aims of surgery in craniosynostotic children.

Applications of an athymic nude mouse model of nonhealing critical-sized calvarial defects

Calvarial bone defects are a common clinical scenario in craniofacial surgery. Numerous approaches are used to reconstruct skull defects, and each possesses its own inherent disadvantages. This fact underscores the opportunity to develop a novel method to repair osseous defects in craniofacial surgery. Recent literature strongly suggests that cell-based therapies in the form of regenerative medicine may be a developing paradigm in reconstructive surgery. Although numerous studies have probed osteoprogenitor cells from mice, few have explored the biology of human cells in the setting of osteogenesis in an equally rigorous manner. This study proposes a nude mouse model of critical-sized calvarial defects to study the in vivo biology of human osteoprogenitor cells. Critical-sized 4.0-mm calvarial defects were created in nude mice (n = 15) with a custom trephine drill bit outfitted to a dental drill handpiece. During the craniotomy, the dura mater was spared from injury. Gross inspection, routine histology, and micro-computed tomographic scanning were performed at 2, 4, 8, and 16 weeks postoperatively. There was no calvarial healing in any of the animals by 16 weeks. The dura mater remained intact in all subjects. Gross, histologic, and radiographic assays confirmed these findings. Although several studies have implanted human osteoprogenitor cells in vivo in various animal models, few have documented the appropriate controls or conditions necessary to support the potential to translate benchtop findings into clinical applications. We propose in this study that the nude mouse critical-sized calvarial defect model will be valuable with increasing investigations with human osteoprogenitor cells.