Pediatric Cranioplasty Using Particulate Calvarial Bone Graft:

Autologous Cranioplasty Using a Dental SafeScraper Device

SUMMARY

Conventional methods to reconstruct cortical bone defects introduced by pediatric cranial vault remodeling (CVR) procedures have shortcomings. Use of bone burr shavings as graft material leads to variable ossification, and harvesting split-thickness cortical grafts is time-intensive and often not possible in thin infant calvaria. Since 2013, the authors' team has used the SafeScraper, originally developed as a dental instrument, to harvest cortical and cancellous bone grafts during CVR. The authors assessed the effectiveness of this technique by analyzing postoperative ossification using computed tomography scans of 52 patients, comparing cohorts treated with the SafeScraper versus those who received conventional methods of cranioplasty during fronto-orbital advancement. The SafeScraper cohort had a greater reduction in total surface area of all defects (-83.1% ± 14.9 versus -68.9% ± 29.8; P = 0.034), demonstrating a greater and more consistent degree of cranial defect ossification compared with conventional methods of cranioplasty, suggesting potential adaptability of this tool. This is the first study that describes the technique and efficacy of the SafeScraper in reducing cranial defects in CVR.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

A Narrative Review of Cell-Based Approaches for Cranial Bone Regeneration

Current cranial repair techniques combine the use of autologous bone grafts and biomaterials. In addition to their association with harvesting morbidity, autografts are often limited by insufficient quantity of bone stock. Biomaterials lead to better outcomes, but their effectiveness is often compromised by the unpredictable lack of integration and structural failure. Bone tissue engineering offers the promising alternative of generating constructs composed of instructive biomaterials including cells or cell-secreted products, which could enhance the outcome of reconstructive treatments. This review focuses on cell-based approaches with potential to regenerate calvarial bone defects, including human studies and preclinical research. Further, we discuss strategies to deliver extracellular matrix, conditioned media and extracellular vesicles derived from cell cultures. Recent advances in 3D printing and bioprinting techniques that appear to be promising for cranial reconstruction are also discussed. Finally, we review cell-based gene therapy approaches, covering both unregulated and regulated gene switches that can create spatiotemporal patterns of transgenic therapeutic molecules. In summary, this review provides an overview of the current developments in cell-based strategies with potential to enhance the surgical armamentarium for regenerating cranial vault defects.

Autologous Calvarial Bone Remodeling Technique for Small to Medium-Sized Cranial Defects in Young Children: The "Switch-Cranioplasty" Technique

INTRODUCTION

Reconstruction of cranial defects in children less than 2 years of age, particularly when there is an associated dural defect, is challenging due to the need to accommodate active skull growth, limited options for autologous bone graft and thin calvarial bones. We use a simple remodeling technique that exploits the normal dura's inherent potential for new bone growth while covering the dural defect with adjacent skull.

CASE PRESENTATION

We describe an alternating, two-piece craniotomy or "switch-cranioplasty technique" to repair an occipital meningocele. The two pieces of craniotomy bone flap created around the existing skull and dural defect are switched in the horizontal plane in order to cover the site of the defect and the abnormal dura of the meningocele closure. The area of the original skull defect is transposed laterally over the normal dura. The healing of the lateral skull defects is facilitated with autologous bone chips and dust and covered by periosteal flaps that stimulate spontaneous re-ossification.

DISCUSSION

The advantages of this technique are the use of autologous bone adjacent to the skull defect, incorporation of the autologous bone into the growing skull, an acceptable cosmetic and functional outcome in a simple manner. The indications can be extended to include small to medium-sized calvarial defects secondary to leptomeningeal cyst and trauma.

Split Calvarial Bone Graft for Reconstruction of Skull Defect in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease in which histiocytes proliferates in several tissues. It mainly occurs in children between 1 and 15 years of age, and affects bone especially the skull being the most common site of invasion. It is desirable to reconstruct the skull defect after surgical removal of the lesion with autologous bone considering the fact that this disease affects children who continuously experience the deformation and growth of the frontal head. We introduce a case report who reconstructs the skull defect using split calvarial bone graft in LCH. A 3-year-old male visited the hospital with a painful, palpable protruding mass in the frontal area lasting 1 month. Craniectomy with skull tumor removal was performed by neurosurgeon, after that we harvested a calvarial bone graft and carefully separated the outer cortex from the inner cortex. Then, we covered the donor site with the inner cortex while covered the bone defect with the outer cortex and fixed with absorbable plates. The patient showed palpable mass at 1-year follow-up but it disappeared. After 5 years, there was no recurrence, the lytic lesion of the skull was resolved, and showed cosmetically good result. We conclude that the palpable lesion was more likely to be the result of postoperative swelling of the plate. We propose split calvarial bone graft as a good treatment option for reconstruction of the skull defect in LCH.

Visualization of skull remodeling and re-ossification after reconstructive surgery and mosaic-like cranioplasty in sagittal synostosis and deformational brachycephaly1

INTRODUCTION

Extended vertex craniectomy in sagittal synostosis (SS) and transposition craniectomy in severe deformational brachycephaly (DB) combined with mosaic-like cranioplasty (M-LC) have been performed in 17 and 24 infants from 2001 to 2003. The hitherto not well-known mechanisms of remodeling and effectiveness of M-LC is assessed by X-ray and anthropometry.

METHODS

Follow-ups included skull radiograms preoperatively and 3 and 15 months postoperatively, which were analyzed by craniometry according to Haas, long-term anthropometry, and clinical follow-up till mean age of 7.6 and 7.4 years. Analysis included the following: time course of cephalic indexes (CI), sizes of distances (breadth, length, height) and modulus, and mean deviation of distances and modulus from the normal age- and sex-dependent values; evaluation of re-ossification of the operative defects covered by M-L C.

RESULTS

CI in SS is normalized in early follow-up with stabilization thereafter; CI of DB is gradually normalized till late follow-up. Remodeling occurs in both disorders by active and passive mechanisms: increased growth of distances with preoperative minus and decreased growth of distances with surplus. The latter mechanism adds more to the postoperative remodeling. M-LC leads to concentric and final complete re-ossification of the defects.

DISCUSSION

Significant remodeling of the skull vault is observed in both disorders by the demonstrated time course and mechanisms. M-LC does not hinder early remodeling and guarantees re-ossification of the defects.

Cranioplasty after craniectomy in pediatric patients-a systematic review

INTRODUCTION

Complications following cranioplasty with either autografts or cranial implants are commonly reported in pediatric patients. However, data regarding cranioplasty strategies, complications and long-term outcomes are not well described. This study systematically reviews the literature for an overview of current cranioplasty practice in children.

METHODS

A systematic review of articles published from inception to July 2018 was performed. Studies were included if they reported the specific use of cranioplasty materials following craniectomy in patients younger than 18 years of age, and had a minimum follow-up of at least 1 year.

RESULTS

Twenty-four manuscripts, describing a total of 864 cranioplasty procedures, met the inclusion criteria. The age of patients in this aggregate ranged from 1 month to 20 years and the weighted average was 8.0 years. The follow-up ranged from 0.4 months to 18 years and had a weighted average of 40.4 months. Autologous bone grafts were used in 484 cases (56.0%). Resorption, infection and/or hydrocephalus were the most frequently mentioned complications. In this aggregate group, 61 patients needed a revision cranioplasty. However, in 6/13 (46%) papers studying autologous cranioplasties, no data was provided on resorption, infection and revision cranioplasty rates. Cranial implants were used in 380 cases (44.0%), with custom-made porous hydroxyapatite being the most commonly used material (100/380, 26.3%). Infection and migration/fracturing/loosening were the most frequently documented complications. Eleven revision cranioplasties were reported. Again, no data was reported on infection and revision cranioplasty rates, in 7/16 (44%) and 9/16 (56%) of papers, respectively.

CONCLUSION

Our systematic review illuminates that whether autografts or cranial implants are used, postcranioplasty complications are quite common. Beyond this, the existing literature does not contain well documented and comparable outcome parameters, suggesting that prospective, long-term multicenter cohort studies are needed to be able to optimize cranioplasty strategies in children who will undergo cranioplasty following craniectomy.

The application of polyetheretherketone (PEEK) implants in cranioplasty

Cranioplasty is a challenge to neurosurgeons, especially considering protection of intracranial contents. In recent years, material choice for cranioplasty is still controversial, which brings complexity to this seemingly straightforward procedure. PEEK, a tough, rigid, biocompatible material, has been used more recently in cranioplasty to provide better protection. The aim of this review is to summarize the outcome of research conducted on the material for cranioplasty applications. We also reviewed the comparison of PEEK with several common materials in previous articles. This is also the most complete data review article at present. In addition, the combination of nano-materials and PEEK is also a hotspot of research, so we have made a careful review of this aspect. We also summarized our own experience, telling about the future prospects of PEEK in the field of clinical cranioplasty should be highlighted. Improving the bioactivity, porosity, thinning, biocompatibility, antibacterial ability, integration and cost reduction of PEEK implants without affecting their mechanical properties is a major challenge.

Bone Transport Distraction Osteogenesis in the Reconstruction of Pediatric Posttraumatic Calvarial Defects

Supplemental Digital Content is available in the text.

Reconstruction of posttraumatic calvarial bone defects in pediatric patients is a challenge due to the growing brain and limited autogenous bone supply. Traditional techniques such as split calvarial and particulate bone grafts are associated with prolonged operative time and significant blood loss, which is a major concern in children under the age of 3 years. Bone transport distraction osteogenesis has proven efficacy and safety in the reconstruction of other craniofacial deformities. This procedure is less invasive and requires shorter operative times and hospital stay. We report our experience with 2 cases of bone transport distraction osteogenesis for the reconstruction of large posttraumatic calvarial defects in pediatric patients.

Long-Term Characterization of Cranial Defects After Surgical Correction for Single-Suture Craniosynostosis

INTRODUCTION

Craniosynostosis is typically corrected surgically within the first year of life through cranial vault reconstruction. These procedures often leave open calvarial defects at the time of surgery, which are anticipated to close over time in a large proportion of cases. However, residual calvarial defects may result as long-term sequelae from cranial vault remodeling. When larger defects are present, they may necessitate further reconstruction for closure.Better understanding of the calvarial osseous healing process may help to identify which defects will resolve or shrink to acceptable size and which will require further surgery. Our study aims to assess the long-term changes in defect size after cranial vault reconstruction for craniosynostosis.

METHODS

One-year postoperative and long-term computed tomography scans were retrieved from the craniofacial anomalies archive. Analysis used custom software. All defects above the size of 1 cm were analyzed and tracked for calvarial location, surface area, and circularity. Monte Carlo simulation was performed to model the effect of initial defect size on the rate of defect closure.

RESULTS

We analyzed a total of 74 defects. The mean ± SD initial defect surface area was 3.27 ± 3.40 cm. The mean ± SD final defect surface area was 1.71 ± 2.54 cm. The mean ± SD percent decrease was 55.06% ± 28.99%. There was a significant difference in the percentage decrease of defects in the parietal and frontoparietal locations: 68.4% and 43.7%, respectively (P = 0.001). Monte Carlo simulation results suggest that less than 10% of defects above the size of 9 cm will close to the size of 2.5 cm or less.

CONCLUSIONS

We describe and make available a novel validated method of measuring cranial defects. We find that the large majority of initial defects greater than 9 cm remain at least 1 in in size (2.5 cm) 1 year postoperatively. In addition, there appear to be regional differences in closure rates across the cranium, with frontoparietal defects closing more slowly than those in the parietal region. This information will aid surgeons in the decision-making process regarding cranioplasty after craniosynostosis correction.

Pediatric Cranioplasty

Historically, the approach to pediatric cranioplasty has been largely extrapolated from the treatment of adults. More recently, however, the intricacies of pediatric cranial reconstruction have become better understood, and the surgical management has been refined contemporaneously. Each patient's cranial defect bears a unique set of challenges and, as such, the choice of cranioplasty technique must be tailored accordingly.

Single-stage Total Cranial Vault Remodeling for Correction of Turricephaly: Description of a New Technique

Background:

Turricephaly is considered one of the most difficult cranial deformities to correct as addressing cranial height can result in increased intracranial pressure. We describe a new technique of total calvarial remodeling with bony transposition to simultaneously correct turricephaly and brachycephaly while preserving intracranial volume.

Methods:

A retrospective review of patients undergoing single-stage cranial vault remodeling by a single surgeon (J.G.M.) at a single center between 2007 and 2015 was performed. The procedure consists of a frontal bandeau followed by a 1 cm 360^o axial strip craniectomy. The strip is then rotated 90 degrees into a coronal orientation and interposed between fronto-parietal and parito-occipital segments. Modification for occipital widening can also be performed.

Results:

Six patients with turribrachycephaly underwent the procedure over the 8-year period. Four patients were operated at less than 1 year of age, one patient underwent surgery at 2 years, and one at 9 years. Mean operative time was 4 hours, and mean transfusion was 300cc. There were no major complications. Mean cranial height reduction achieved was 1.6 cm (range, 1.0–2.0 cm), and mean anterior–posterior expansion was 3.4 cm (range, 2.3–4.5 cm). Patients also showed improvement in supraorbital retrusion.

Conclusion:

Single-stage cranial vault remodeling with axial strip craniectomy and coronal interposition is safe and allows for simultaneous correction of turricephaly and brachycephaly while preserving intracranial volume.

Power-Assisted Particulate Bone Grafting Effectively Prevents Osseous Defects After Cranial Vault Reconstruction

BACKGROUND

Cranial vault reconstruction (CVR) is the gold standard in the operative treatment of craniosynostosis. Full thickness osseous defects (FTOD) of the calvaria have been observed in 5% to 15% patients after CVR, with higher rates cited in the fronto-orbital advancement (FOA) subset. Particulate bone graft (PBG) harvested manually has been shown to decrease FTOD after FOA from 24% to 5.5%. The authors used a modified technique using a powered craniotome, with the hypothesis that the technique would also improve outcomes.

METHODS

A retrospective review was performed of patients who underwent CVR for craniosynostosis between 2004 and 2014. Patient demographics, diagnosis, age, operative details, and postoperative care were reviewed in detail. Categorical, nonparametric variables were compared by Fisher exact tests.

RESULTS

A total of 135 patients met inclusion criteria. The most common diagnoses were metopic (n = 41), sagittal (n = 33), and unilateral coronal craniosynostosis (n = 31); 65% (n = 88) underwent FOA, 29% (n = 39) underwent single-stage total vault reconstruction, and 6% (n = 8) had a posterior vault reconstruction. CVR was performed without PBG in 95 patients and with PBG in 40 patients. Without PBG, FTOD were discovered on clinical examination in 18% of patients (n=17): 11 presented with subcentimeter defects, while 6 had larger defects requiring revision cranioplasty (6% operative revision rate). Among those receiving PBG, 1 patient presented a subcentimeter FTOD (2.5% FTOD incidence and 0% operative revision rate).

CONCLUSION

Particulate bone graft harvested with a powered device decreases the rate of FTOD and reoperation rate after CVR for craniosynostosis.

Calvarial Reconstruction

Calvarial reconstruction is a challenge to reconstructive surgeons, especially considering protection of intracranial contents. In recent years, the advent of multiple reconstructive materials adds tools to the surgical armamentarium. Options include autologous split calvarial and rib grafts and alloplastic materials such as titanium mesh, methyl methacrylate, calcium hydroxyapatite, and polyetheretherketone. The most important aspect of cranial reconstruction still lies in finding the most aesthetic, safe, and reliable means of filling a defect.

Autogenous Bone Reconstruction of Large Secondary Skull Defects

BACKGROUND

The authors sought to ascertain the upper limits of secondary skull defect size amenable to autogenous reconstructions and to examine outcomes of a surgical series. Published data for autogenous and alloplastic skull reconstructions were also examined to explore associations that might guide treatment.

METHODS

A retrospective review of autogenously reconstructed secondary skull defects was undertaken. A structured literature review was also performed to assess potential differences in reported outcomes between autogenous bone and synthetic alloplastic skull reconstructions. Weighted risks were calculated for statistical testing.

RESULTS

Ninety-six patients underwent autogenous skull reconstruction for an average defect size of 93 cm (range, 4 to 506 cm) at a mean age of 12.9 years. The mean operative time was 3.4 hours, 2 percent required allogeneic blood transfusions, and the average length of stay was less than 3 days. The mean length of follow-up was 28 months. There were no postoperative infections requiring surgery, but one patient underwent secondary grafting for partial bone resorption. An analysis of 34 studies revealed that complications, infections, and reoperations were more commonly reported with alloplastic than with autogenous reconstructions (relative risk, 1.57, 4.8, and 1.48, respectively).

CONCLUSIONS

Autogenous reconstructions are feasible, with minimal associated morbidity, for patients with skull defect sizes as large as 500 cm. A structured literature review suggests that autogenous bone reconstructions are associated with lower reported infection, complication, and reoperation rates compared with synthetic alloplasts. Based on these findings, surgeons might consider using autogenous reconstructions even for larger skull defects.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

An Outcomes Comparison Between Autologous and Alloplastic Cranioplasty in the Pediatric Population

BACKGROUND

The use of alloplastic material in cranial reconstruction has been well described in the adult population, especially when a paucity of autologous tissue exists. In children it is unknown how long-term growth, however, may be affected by the implantation of nonexpansible alloplastic material. Therefore, the authors sought to compare the outcomes of pediatric patients undergoing alloplastic versus autologous cranial reconstruction.

METHODS

To assess the safety and long-term outcomes of alloplastic cranioplasty in children, an institutional review board-approved, retrospective, single institution review of pediatric patients undergoing cranioplasty was performed from 2000 to 2014. The age at surgery, cause of the cranial defect, defect size, time since initial surgery to reconstruction, implant type, and complications were assessed. Postreconstruction imaging was reviewed if available.

RESULTS

A reconstructive cranioplasty was performed in 41 pediatric patients (ages 1-19 years, average 7.35 years). Thirty patients underwent alloplastic reconstruction (age 4.37 ± 5.57 years), and 11 underwent autologous reconstruction (age 2.00 ± 3.74 years). The size of the cranial defects was 144.01 ± 393.04 cm for autologous and 405.31 ± 572.96 cm for alloplastic reconstructions. Follow-up for all patients was an average of 2.33 ± 2.76 years (0.1-9 years). No patients in either group showed evidence of elevated intracranial pressure after cranioplasty. In long-term follow-up, none of the implants were exposed or lost because of infection. Computed tomography and physical examination demonstrated that there was no skull growth restriction in either group.

CONCLUSIONS

Our data show that alloplastic cranioplasty in the pediatric population is a safe alternative, when autologous cranial bone is not available.

A Novel Local Autologous Bone Graft Donor Site After Scalp Tissue Expansion in Aplasia Cutis Congenita

Aplasia cutis congenita (ACC) is a rare condition often presenting as an absent area of cutaneous scalp. The calvarium and dura may also be affected. Scalp reconstruction with tissue expansion is often needed for large defects. Patients involving deficient calvarial bone present a dilemma for the reconstructive surgeon, because bone graft donor sites are limited in young children.A thick, bony rim has been noted to form around the periphery of scalp tissue expanders. The authors present a series of 3 patients with ACC for whom this bony hyperostosis was used as donor particulate bone graft at the time of scalp tissue expansion. There was 85 to 100% graft ossification on postoperative computed tomography scan. There were no bone graft-related complications.In conclusion, the hyperostotic rim that forms after scalp tissue expansion can be successfully used as particulate bone graft, decreasing the number of procedures needed for patient with ACC and obviating the need for other donor sites.

Titanium cranioplasty in children and adolescents

Full thickness calvarial defects present considerable challenges to reconstructive surgeons. In paediatric cases, the use of biomaterials as a substrate for cranioplasty rather than autologous bone is controversial. Alloplastic cranioplasty in adults is supported by several large case series however long term outcome of biomaterial use in paediatric cases is limited. Retrospective seven year analysis of departmental database and clinical records identified 22 patients aged under 18 who had undergone 23 custom made titanium cranioplasties by a single surgeon using the same technique. Data including patient demographics, reason for craniectomy and complications experienced following surgery was obtained. The mean age at operation was 12 years 9 months. The mean defect size was 44.3 cm(2). No significant complications related to the cranioplasty were recorded in the early post operative period or during long term review (average follow up 4 years 6 months). No cranioplasty implant required removal. This retrospective case series shows that custom made patient specific titanium cranioplasty is a viable alternative to autologous bone as a reconstructive material in paediatric patients under specific circumstances.

Fabrication of Gelatin/PCL Electrospun Fiber Mat with Bone Powder and the Study of Its Biocompatibility

Fabricating ideal scaffolds for bone tissue engineering is a great challenge to researchers. To better mimic the mineral component and the microstructure of natural bone, several kinds of materials were adopted in our study, namely gelatin, polycaprolactone (PCL), nanohydroxyapatite (nHA), and bone powder. Three types of scaffolds were fabricated using electrospinning; gelatin/PCL, gelatin/PCL/nHA, and gelatin/PCL/bone powder. Scaffolds were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. Then, Adipose-derived Stem Cells (ADSCs) were seeded on these scaffolds to study cell morphology, cell viability, and proliferation. Through this study, we found that nHA and bone powder can be successfully united in gelatin/PCL fibers. When compared with gelatin/PCL and gelatin/PCL/nHA, the gelatin/PCL/bone powder scaffolds could provide a better environment to increase ADSCs' growth, adhesion, and proliferation. Thus, we think that gelatin/PCL/bone powder has good biocompatibility, and, when compared with nHA, bone powder may be more effective in bone tissue engineering due to the bioactive factors contained in it.

Exchange hybrid cranioplasty using particulate bone graft and demineralized bone matrix: the best of both worlds

Reconstruction of craniofacial defects in children presents several challenges that are not encountered in the adult population. Autologous bone grafts have long been the criterion standard for repairing these defects. Recently, several new materials and techniques have expanded our arsenal of reconstructive options. In this clinical report, we describe the use of both particulate bone grafting and demineralized bone matrix together to repair craniofacial defects encountered in pediatric patients.

Repair of tegmen defect using cranial particulate bone graft

Bone paté is used to repair cranial bone defects. This material contains bone-dust collected during the high-speed burring of the cranium. Clinical and experimental studies of bone dust, however, have shown that it does not have biological activity and is resorbed. We describe the use of bone paté using particulate bone graft. Particulate graft is harvested with a hand-driven brace and 16mm bit; it is not subjected to thermal injury and its large size resists resorption. Bone paté containing particulate graft is much more likely than bone dust to contain viable osteoblasts capable of producing new bone.

Evolution of cranioplasty techniques in neurosurgery: historical review, pediatric considerations, and current trends

Cranial bone repair is one of the oldest neurosurgical practices. Reconstructing the natural contours of the skull has challenged the ingenuity of surgeons from antiquity to the present day. Given the continuous improvement of neurosurgical and emergency care over the past century, more patients survive such head injuries, thus necessitating more than ever before a simple, safe, and durable means of correcting skull defects. In response, numerous techniques and materials have been devised as the art of cranioplasty has progressed. Although the goals of cranioplasty remain the same, the evolution of techniques and diversity of materials used serves as testimony to the complexity of this task. This paper highlights the evolution of these materials and techniques, with a particular focus on the implications for managing pediatric calvarial repair and emerging trends within the field.

Transforming growth factor beta 1 augments calvarial defect healing and promotes suture regeneration

BACKGROUND

Repair of complex cranial defects is hindered by a paucity of appropriate donor tissue. Bone morphogenetic protein 2 (BMP2) and transforming growth factor beta 1 (TGFβ1) have been shown separately to induce bone formation through physiologically distinct mechanisms and potentially improve surgical outcome for cranial defect repair by obviating the need for donor tissue. We hypothesize that a combination of BMP2 and TGFβ1 would improve calvarial defect healing by augmenting physiologic osteogenic mechanisms.

METHODS/RESULTS

Coronal suturectomies (3×15 mm) were performed in 10-day-old New Zealand White rabbits. DermaMatrix™ (3×15mm) patterned with four treatments (vehicle, 350 ng BMP2, 200 ng TGFβ1, or 350 ng BMP2+200 ng TGFβ1) was placed in suturectomy sites and rabbits were euthanized at 6 weeks of age. Two-dimensional (2D) defect healing, bone volume, and bone density were quantified by computed tomography. Regenerated bone was qualitatively assessed histologically. One-way analysis of variance revealed significant group main effects for all bone quantity measures. Analysis revealed significant differences in 2D defect healing, bone volume, and bone density between the control group and all treatment groups, but no significant differences were detected among the three growth factor treatment groups. Qualitatively, TGFβ1 treatment produced bone with morphology most similar to native bone. TGFβ1-regenerated bone contained a suture-like tissue, growing from the lateral edge of the defect margin toward the midline. Unique to the BMP2 treatment group, regenerated bone contained lacunae with chondrocytes, demonstrating the presence of endochondral ossification.

CONCLUSIONS/SIGNIFICANCE

Total healing in BMP2 and TGFβ1 treatment groups is not significantly different. The combination of BMP2+TGFβ1 did not significantly increase bone healing compared with treatment with BMP2 or TGFβ1 alone postoperatively at 4 weeks. We highlight the potential use of TGFβ1 to regenerate calvarial bone and cranial sutures. TGFβ1 therapy significantly augmented bony defect healing at an earlier time point when compared with control, regenerated bone along the native intramembranous ossification pathway, and (unlike BMP2 alone or in combination with TGFβ1) permitted normal suture reformation. We propose a novel method of craniofacial bone regeneration using low-dose, spatially controlled growth factor therapies to minimize potentially harmful effects while maximizing local bioavailability and regenerating native tissues.

An Experimental Study of Particulate Bone Graft for Secondary Inlay Cranioplasty Over Scarred Dura

BACKGROUND

Inlay cranioplasty in children is challenging because autologous bone is limited. Cranial particulate bone graft effectively closes defects when placed over normal dura. The purpose of this study was to determine if particulate bone graft will ossify when used for secondary cranioplasty over scarred dura.

METHODS

A 17 × 17-mm critical-sized defect was made in the parietal bone of 16 rabbits. Four animals had no implant (group 1). Twelve animals had the defect remade 16 weeks postoperatively, which was managed in 2 ways: group 2 (no implant; n = 6) and group 4 (particulate bone graft; n = 6). Particulate graft was obtained using a brace and bit from the frontal bone. Computed tomography was used to determine the area of ossification and thickness of the healed graft. Eight animals previously managed with particulate bone graft over normal dura were used as an additional control (group 3).

RESULTS

Critical-sized defects filled with particulate bone graft over scarred dura (group 4) exhibited superior healing of the area (83.8%; range, 73.0%-90.6%) compared to control defects over normal dura (group 1: 62.9%; range, 56.5%-73.4%) or scarred dura (group 2: 56.9%; range, 40.0%-68.3%) (P = 0.0004). Particulate bone on scarred dura exhibited less ossified area (P = 0.002), and thinner bone (0.95 mm, range, 0.71-1.32 mm) compared to defects in which graft was placed over normal dura (group 3: area, 99.2%; range, 96.8%-100%; thickness, 1.9 mm, range; 1.1-3.1 mm) (P = 0.04).

CONCLUSIONS

Particulate bone graft ossifies inlay cranial defects over scarred dura although inferior to placement over normal dura. Clinically, particulate bone graft may be used for secondary inlay cranioplasty.

A comparison between autograft alone, bone cement, and demineralized bone matrix in cranioplasty

OBJECTIVES

To compare bone autograft, bone cement, and demineralized bone matrix in functional and aesthetic outcomes and complications following cranioplasty for reconstruction of cranial defects.

STUDY DESIGN

Retrospective chart review.

MATERIALS AND METHODS

A retrospective chart review was performed of patients who underwent cranioplasty at a single institution between 1992 and 2012. The patients were divided based on whether bone autograft, demineralized bone matrix, or bone cement was used for reconstruction of their craniofacial defect. Demographics and diagnosis data were collected. Complications and cosmetic outcomes were examined for each group.

RESULTS

There was no significant difference between groups regarding follow-up and age at time of surgery. The bone cement group had a higher infection rate. There was more dehiscence and scalp scarring in the autograft and bone cement groups. However, residual bone defects and the need for a revision cranioplasty were higher in the bone matrix group. Likewise, patient, parent, and surgeon satisfaction with the appearance was lower in the bone matrix group.

CONCLUSIONS

There appears to be a trend toward a lower success rate in patients with fibroblast growth factor receptor-related craniosynostosis and in those reconstructed with bone matrix compared to bone autograft and bone cement.

LEVEL OF EVIDENCE

4.

Does the Use of Particulate Bone Graft Increase the Incidence of Postoperative Infection in Surgery for Craniosynostosis?

Objective

The use of particulate bone graft (PBG) has become an accepted technique for filling cranial defects created during cranial vault expansion for craniosynostosis. However, the use of PBG may be a risk factor for postoperative infection. The aim of this study was to compare the rate of postoperative infection in patients who received particulate bone graft (PBG+) with that in patients who did not (PBG–).

Design

An Institutional Review Board–approved, retrospective, cohort study of consecutive patients was performed. Twenty-seven consecutive patients in the PBG– group were compared with 21 consecutive patients in the PBG+ group. The two cohorts were assessed for incidence of surgical-site infection.

Results

Statistical analysis was performed using the Fisher exact probability test. Surgical site infection occurred in none of the PBG– patients (0%) versus one of the PBG+ patients (4.76%). This difference in infection rates between the two cohorts was not statistically significant ( P = .4375).

Conclusions

Although there may be concern that PBG could serve as a facilitative medium for bacterial growth, this study demonstrates no statistically significant increase in infection rates with its use. Particulate bone grafting of cranial defects resulting from cranial vault expansion in craniosynostosis remains a useful and valuable technique.

Cranioplasty for large-sized calvarial defects in the pediatric population: a review

Large-sized calvarial defects in pediatric patients pose a reconstructive challenge because of children's unique physiology, developing anatomy, and dynamic growth. We review the current literature and outcomes with autologous and alloplastic cranioplasty in the pediatric population.

Split cranial bone grafting in children younger than 3 years old: debunking a surgical myth

BACKGROUND

In cranioplasty patients split cranial bone provides excellent structural support and fundamentally "replaces like with like." However, traditional teaching in craniofacial surgery is that cranial bone cannot be split before the age of 3 years because of the lack of diploic space. The authors have found this not to be the case and describe their experience with splitting cranial bone in children with craniosynostosis younger than 3 years.

METHODS

The authors completed a retrospective review of 418 cranioplasties performed between 1997 and 2013 by a single surgeon on patients younger than 3 years with syndromic and nonsyndromic craniosynostosis. Average patient age at the time of the procedure was 328 days. The youngest patient was 58 days old.

RESULTS

Of the 418 cranial procedures performed in this study, cranial bone could be split and used as bone graft in every case. Although the presence of Lückenschädel prevented a complete split of the inner table from the outer table of the bone flap, split cranial bone grafting could still be performed, providing significant grafting material to foster reconstruction. No complications from split cranial harvest were observed.

CONCLUSIONS

Contrary to popular belief and the misconception perpetuated by the Plastic Surgery In-Service Examination, the cranium of children younger than 3 years can indeed be safely and predictably split between the inner and outer cortex. This important finding provides the craniofacial surgeon with a valuable, expanded source of rigid bone for cranial vault remodeling in the pediatric patient population.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Use of a customized 3D "basket" to create a solitary split-thickness cranial graft from numerous split fragments in an infant

While autologous split calvaria remains the preferred material for use in pediatric cranioplasty, it may be difficult to split the bone neatly into two distinct pieces, especially in infants and young children. In this paper, the authors present a technique in which numerous split pieces of bone can be readily joined together and conformed to the shape of the specific defect using a customized template and 3D trellis-like basket.

Comparison of bone dust with other types of bone grafts for cranioplasty

PURPOSE

Split calvarial bone graft is preferred in the reconstruction of calvarial defects. However, it is not feasible for use in some challenging cases and in children. Particulate bone graft containing viable osteoblasts could be an attractive alternative.

MATERIALS AND METHODS

A total of 32 female rats were randomly separated into 4 groups. Full-thickness bone graft from rat calvaria was harvested in diameters of 8 × 8 mm. In group 1, the periosteum and skin were closed without any bone graft; bone dust particles were placed in group 2; bone fragments were placed in group 3; and full-thickness cranial bone graft was placed in group 4. After 12 weeks, all rats were killed. Degrees of resorption, foreign body reaction, and bone spicule length were assessed histologically, and an immunohistochemical study was used to show bone graft viability.

RESULTS

In graft viability, osteogenesis, and osteoblastic differentiation, groups 3 and 4 were similar and superior to groups 1 and 2. No osteoblastic activity and no viable bone dust were detected in groups 1 and 2. Resorption was observed in every preparate that contains bone tissue, and foreign body reaction was prominent in small bone groups, such as in group 2.

CONCLUSIONS

In the full-thickness cranial bone graft group and the bone fragment group, the preservation of bone viability was obviously superior to the bone dust group and the periosteum-only group. In conclusion, bone dust behaved like the periosteum and could not create new bone, whereas bone particles behaved like the full-thickness cranial bone graft and were capable of preserving viability.

Cranioplasty with polymethylmethacrylate prostheses fabricated by hand using original bone flaps: Technical note and surgical outcomes

Background:

Decompressive craniectomies (DC) mandate future cranioplasties, accounting for the large array of biomaterials for this purpose. Polymethylmethacrylate (PMMA) is a very reliable thermoplastic that can be prefabricated or even molded intraoperatively to create an adequate prosthesis. Preformed PMMA implants made by hand have been superseded by newer 3-D printed implants, but this is accompanied by higher costs and timing issues, apart from having limited availability in developing and third-world countries.

Methods:

A total of 26 patients were operated over a span of 11 years. A total of 26 custom hand-made PMMA prostheses were fabricated using original bone flaps with the aid of a prosthodontist, in a process that took approximately 70 minutes for each implant. The result was an exact duplication of the patient's bone flap.

Results:

Of the 26 patients who underwent cranioplasty, the majority of patients were males, with a mean age of 39.2 years and traumatic brain injury as main indication for DC. After a mean interval of 2.4 months, all 26 patients underwent a cranioplasty and prosthesis placement. Only two patients (7.6%) suffered from direct cranioplasty-related complications after a median follow-up of 10.4 months. Median Glasgow Outcome Scale scores improved significantly from 3 to 4 after cranioplasty (P = 0.008).

Conclusion:

Prefabrication of custom PMMA prostheses by hand when original bone flaps are available is an excellent alternative to newer 3-D printing techniques, because it is relatively cheaper, less time consuming, and offers excellent results in terms of anatomical reconstruction and improvement of neurological function in long-term follow-ups.

Syndromic craniosynostosis

Although most cases of craniosynostosis are nonsyndromic, craniosynostosis is known to occur in conjunction with other anomalies in well-defined patterns that make up clinically recognized syndromes. Patients with syndromic craniosynostoses are much more complicated to care for, requiring a multidisciplinary approach to address all of their needs effectively. This review describes the most common craniosynostosis syndromes, their characteristic features and syndrome-specific functional issues, and new modalities utilized in their management. General principles including skull development, the risk of developing increased intracranial pressure in craniosynostosis syndromes, and techniques to measure intracranial pressure are discussed. Evolving techniques of the established operative management of craniosynostosis are discussed together with more recent techniques including spring cranioplasty and posterior cranial vault distraction osteogenesis.

Experimental Comparison of Cranial Particulate Bone Graft, rhBMP-2, and Split Cranial Bone Graft for Inlay Cranioplasty

Background

Particulate bone graft and recombinant human bone morphogenetic protein-2 (rhBMP-2) are options for inlay cranioplasty in children who have not developed a diploic space. The purpose of this study was to determine whether particulate bone graft or rhBMP-2 has superior efficacy for inlay cranioplasty and to compare these substances to split cranial bone.

Methods

A 17 mm × 17 mm critical-sized defect was made in the parietal bones of 22 rabbits and managed in four ways: Group I (no implant; n=5), Group II (particulate bone graft; n=5), Group III (rhBMP-2; n=7), and Group IV (split cranial bone graft; n=5). Animals underwent microcomputed tomography and histologic analysis 16 weeks after cranioplasty.

Results

Defects without an implant (Group I) demonstrated inferior ossification (41.4%; interquartile range [IQR], 28.9% to 42.5%) compared to those treated with particulate bone graft (Group II: 99.5%; IQR, 97.8% to 100%), rhBMP-2 (Group III: 99.6%; IQR, 99.5% to 100%), or split cranial bone (Group IV: 100%) ( P < .0001). There was no difference between Groups II, III, and IV ( P = .1). Defects treated with rhBMP-2 exhibited thinner bone (0.90 mm; IQR, 0.64 to 0.98) than particulate bone graft (1.95 mm; IQR, 1.09 to 2.83) or split cranial bone (1.72 mm; IQR, 1.54 to 1.88) ( P = .006); particulate and split cranial bone grafted defects had a similar thicknesses ( P = .6).

Conclusions

Particulate bone graft, rhBMP-2, and split cranial bone close inlay calvarial defect areas equally, although the thickness of bone healed with rhBMP-2 is inferior. Clinically, particulate bone graft or split cranial bone graft may be superior to rhBMP-2 for inlay cranioplasty.

Autologous cranial particulate bone graft: an experimental study of onlay cranioplasty

The purpose of this study was to determine whether particulate bone graft maintains its volume when used for onlay cranioplasty. Twenty-five adult, male, New Zealand white rabbits were divided into 5 groups (n = 5/group). Groups 1 to 3 were controls: group 1, untreated; group 2, sham procedure; and group 3, burring the cortical surface. Group s 4 and 5 had augmentation of the parietal bones with particulate graft harvested from the frontal bone with a brace and bit. The particulate graft was placed on native parietal bone (group 4) or on parietal bone that had been abraded to punctuate bleeding with an electric burr (group 5). Volume maintenance and osseointegration of the grafts were determined by micro-computed tomography and histology. At 16 weeks postoperatively, the mean (SD) volumes of the parietal bones in control groups 1, 2, and 3 were 555.8 (29.2), 550.8 (36.8), and 539.0 (39.0) mm, respectively. Immediately after cranioplasty, the mean (SD) volumes of augmented parietal bone were 846.0 (10.8) mm for group 4 and 831.8 (11.8) mm for group 5. Sixteen weeks postoperatively, 100% of the group 4 grafts had resorbed (551.8 [SD, 24.0] mm), and parietal volume was no different from controls (P = 0.89). Group 5 maintained 54.2% of volume (695.6 [SD, 22.0] mm), which was greater than those of the controls (P < 0.0001). Particulate graft may be used for onlay cranioplasty if the recipient site is burred. Approximately one half of the onlay graft is resorbed, and its original shape is not maintained.

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.

Use of occipital bone graft in pediatric posterior cervical fusion: an alternative paramedian technique and review of the literature

An alternative method of bone grafting for pediatric posterior cervical and occipitocervical fixation is presented in detail. Full-thickness autografts from small craniectomies of the occipital bone are used to augment posterior segmental fusion in pediatric patients. Twelve patients have been treated successfully without bone graft donor site complications. The technical differences from previously reported uses of calvarial autograft in spine fusion are reviewed.

A rare case of psammomatoid ossifying fibroma in the sphenoid bone reconstructed using autologous particulate exchange cranioplasty

Psammomatoid ossifying fibroma (POF), a variant of ossifying fibroma, is a benign fibroosseous lesion typically arising within the nasal cavity, paranasal sinuses, and orbit. Cranial vault involvement is exceedingly rare, with very few cases reported in the literature. The authors report a case of POF in the neurocranium of an 11-year-old child, 4 years after chemotherapy and radiation therapy for acute lymphoblastic leukemia. This case is reported in view of its rarity, novelty of presentation, and the difficulty in diagnosis due to its radiological resemblance to aneurysmal bone cyst or monostotic cystic fibrous dysplasia, further aggravated by the clinical scenario. A novel technique of cranial reconstruction called autologous particulate exchange cranioplasty was used following tumor excision.

Repair of a large congenital frontal bone defect with autologous exchange cranioplasty

The authors report the case of a large idiopathic frontal bone defect and concomitant sagittal synostosis corrected by autologous exchange cranioplasty by using a corticocancellous bone graft and cranial vault expansion. An otherwise healthy, developmentally normal 6-year-old girl presented to our clinic with a large frontal bone defect. The osseous defect was midline and inferior to the coronal sutures, and the underlying dura was slightly tense. She had no signs or symptoms of increased intracranial pressure, and her head circumference and cephalic index were normal. Imaging demonstrated fusion of the sagittal synostosis. The defect was repaired using full-thickness autologous bone harvested from the bilateral parietal regions, which were widened using barrel-stave osteotomies to reduce pressure on the graft site in the setting of sagittal synostosis and mild cranial narrowing. The donor sites were covered with autologous particulate bone graft harvested from the endocortical surface of the grafted segments and the ectocortical surface of the intact parietal bones. The donor and recipient sites healed. Imaging revealed that the particulate bone healed with a thickness similar to the surrounding bone. This bony defect is analogous to parietal foramina and may have a similar etiopathogenesis. The technique of autologous exchange cranioplasty using corticocancellous particulate bone graft provides a simple and reliable method to repair large structural calvarial defects.

Waterjet dissection in pediatric cranioplasty

OBJECT

Waterjet dissection has been shown to separate tissues of different resistance, with preservation of blood vessels. In cranioplasty, separation of subcutaneous tissue and dura mater is often difficult to achieve because the various tissue layers strongly adhere to each other after decompressive craniotomy. In the present study, the potential advantages and drawbacks of the waterjet technique in cranioplasty after craniectomy and duraplasty are addressed.

METHODS

The waterjet effect on fresh human cadaveric dura mater specimens as well as on several dural repair patches was tested in vitro under standardized conditions, with waterjet pressures up to 80 bar. Subsequently, 8 pediatric patients (5 boys, 3 girls; mean age 9.9 years, range 1.2-16.7 years) who had been subjected to decompressive craniectomy (7 with duraplasty including bovine pericardium as a dural substitute, 1 without duraplasty in congenital craniosynostosis) underwent waterjet cranioplasty. The waterjet was used to separate the galea and the dura mater. The technique was applied tangentially between the dura and the galea, with different pressure levels up to 50 bar.

RESULTS

In vitro, fresh cadaveric human dura mater as well as 2 different dural repair substitutes showed a very high resistance to waterjet dissection up to 80 bar. The human dura and the various substitutes were dissected only after long-lasting exposure to the waterjet. Human dura was perforated at pressures of 60 bar and higher. Bovine pericardium dural substitute was perforated at pressures of 55 bar and higher. Artificial nonabsorbable polyesterurethane dural substitute was dissected at pressures of 60 bar and higher. In the clinical setting, the waterjet was able to separate galea and dura with minimal bleeding. No blood transfusion was required. Dissection of scarred tissue was possible by a waterjet of 40 bar pressure. Tissue layers were stretched and separated by the waterjet dissection, and a very reliable hemostasis resulted. This resulted in an effective reduction of bleeding, with < 60 ml blood loss in 7 of the 8 cases. Neither a dural tear nor a perforation of any duraplasty occurred during operative preparation. There were no operative or postoperative complications.

CONCLUSIONS

The experimental and clinical data show that waterjet separation of dura mater, dural substitute, and galea can be performed with a high level of safety to avoid dural tears. The waterjet dissection stretches tissue layers, which results in a reliable hemostasis effect. This potentially results in an effective reduction of surgical blood loss, which should be the focus of further studies.