Classification of the Residual Cranial Defects and Selection of Reconstruction Materials

Evaluation of Vitamin D-enriched Bone Graft in Surgically-induced Critical-sized Bone Defects: An Experimental Study

BACKGROUND

Restoration of bone defects in the craniac vault may require the use of autografts, allografts, xenografts, or synthetic grafts. There are promising data that vitamin D may play a positive role in graft incorporation. The purpose of the present study is the evaluation of the impact of vitamin D addition to human-derived bone grafts in the healing of critical-sized bone defects in porcine skulls.

MATERIALS AND METHODS

Four identical critical-sized defects were created in the calvaria of 8 adult Landrace Large White pigs. The first defect was left blank as control, the second defect was filled with human-derived bone graft, the third defect was filled with human-derived bone graft enriched with a low concentration of vitamin D (2 mg/mL), and the fourth defect was filled with human-derived bone graft enriched with a high concentration of vitamin D (10 mg/mL). The animals were sacrificed after 12 weeks. Harvested tissue specimens were qualitatively evaluated by histology. New bone formation (bone volume/tissue volume) was quantitatively measured by histomorphometry.

RESULTS

Signs of bone formation were evident in all bone sockets. Mean values of the bone volume/tissue volume of the 4 defects were 10.91%, 11.05%, 10.40% and 10.87% respectively, at 12 weeks. In 5 animals, high concentration of vitamin D caused a significant improvement in bone formation in relation to controls. In 3 animals, a high concentration of vitamin D was associated with decreased bone formation compared with controls. No statistical difference was observed in the graft healing among the 4 graft sites ( P > 0.05).

CONCLUSIONS

The results of this study have shown that the addition of vitamin D to human-derived bone grafts does not have a significant effect on bone formation and graft incorporation in critical-sized bone defects of the porcine calvaria. Further high-quality studies are needed to fully elucidate the role of vitamin D in bone formation and bone graft union.

"Bridging the Breach": Cranioplasties Using Different Reconstruction Materials-An Institutional Experience

Introduction

Cranioplasty is a time tested surgical procedure to restore the form and function of either congenital or acquired calvarial defects. Both autologous bone flaps and alloplastic substitutes have been surgically explored over time to achieve the pre-morbid contour and eliminate the existing and anticipated complications like the "Sinking flap Syndrome". Though autologous bone flap, if preserved, is generally considered the first choice for reconstruction, however its absence/large defect reconstruction calls for alternative options. The selection of the reconstructive material is governed by various patient factors and material-related issues. The current study is an institutional experience of calvarial reconstruction with different materials. Though the aim of the surgery is always maximum patient comfort and satisfaction, post-operative outcome may vary from case to case.

Materials and Method

Patients with calvarial defects post decompressive craniectomy, referred to the Department of OMFS from the Department of Neurosurgery/Neurology at our tertiary care centre, were successfully managed for the same using autologous Bone flap, customized Titanium and PEEK patient specific implant (PSI). Post-op evaluation for aesthetics, ease of adjustment/workability, thermal conductivity and infection/exposure was done at 01 and 06 months.

Results

Fifteen patients of cranial defects post decompressive craniectomy were taken up of calvarial reconstruction using autologous Bone flap (n = 5), Titanium (n = 5) and PEEK (n = 5) patient specific implant (PSI). Satisfactory restoration of cranial contour was seen in all cases immediately after surgery. One patient underwent flap necrosis in bone flap group, while thermal conductivity was reported in 2 out of 5 cases of titanium PSI. Ease of workability was relatively low in all cases of PEEK group while increased overall surgical duration was encountered in bone flap group owing to second surgical site in abdomen.

Conclusion

A variety of reconstruction materials may be used for cranial contouring depending on the defect and surgeon's experience, however the results may vary from case to case thus mandating tailor-made treatment for each patient.

A Medical-Grade Polycaprolactone and Tricalcium Phosphate Scaffold System With Corticoperiosteal Tissue Transfer for the Reconstruction of Acquired Calvarial Defects in Adults: Protocol for a Single-Arm Feasibility Trial

Background

Large skull defects present a reconstructive challenge. Conventional cranioplasty options include autologous bone grafts, vascularized bone, metals, synthetic ceramics, and polymers. Autologous options are affected by resorption and residual contour deformities. Synthetic materials may be customized via digital planning and 3D printing, but they all carry a risk of implant exposure, failure, and infection, which increases when the defect is large. These complications can be a threat to life. Without reconstruction, patients with cranial defects may experience headaches and stigmatization. The protection of the brain necessitates lifelong helmet use, which is also stigmatizing.

Objective

Our clinical trial will formally study a hybridized technique's capacity to reconstruct large calvarial defects.

Methods

A hybridized technique that draws on the benefits of autologous and synthetic materials has been developed by the research team. This involves wrapping a biodegradable, ultrastructured, 3D-printed scaffold made of medical-grade polycaprolactone and tricalcium phosphate in a vascularized, autotransplanted periosteum to exploit the capacity of vascularized periostea to regenerate bone. In vitro, the scaffold system supports cell attachment, migration, and proliferation with slow but sustained degradation to permit host tissue regeneration and the replacement of the scaffold. The in vivo compatibility of this scaffold system is robust—the base material has been used clinically as a resorbable suture material for decades. The importance of scaffold vascularization, which is inextricably linked to bone regeneration, is underappreciated. A variety of methods have been described to address this, including scaffold prelamination and axial vascularization via arteriovenous loops and autotransplanted flaps. However, none of these directly promote bone regeneration.

Results

We expect to have results before the end of 2023. As of December 2020, we have enrolled 3 participants for the study.

Conclusions

The regenerative matching axial vascularization technique may be an alternative method of reconstruction for large calvarial defects. It involves performing a vascularized free tissue transfer and using a bioresorbable, 3D-printed scaffold to promote and support bone regeneration (termed the regenerative matching axial vascularization technique). This technique may be used to reconstruct skull bone defects that were previously thought to be unreconstructable, reduce the risk of implant-related complications, and achieve consistent outcomes in cranioplasty. This must now be tested in prospective clinical trials.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12620001171909; https://tinyurl.com/4rakccb3

International Registered Report Identifier (IRRID)

DERR1-10.2196/36111

Regenerative matching axial vascularisation of absorbable 3D-printed scaffold for large bone defects: A first in human series

BACKGROUND

We describe the first clinical series of a novel bone replacement technique based on regenerative matching axial vascularisation (RMAV). This was used in four cases: a tibial defect after treatment of osteomyelitis; a calvarial defect after trauma and failed titanium cranioplasty; a paediatric tibial defect after neoadjuvant chemotherapy and resection of Ewing sarcoma; and a paediatric mandibular deficiency resulting from congenital hemifacial microsomia.

METHOD

All patients underwent reconstruction with three-dimensional (3D)-printed medical-grade polycaprolactone and tricalcium phosphate (mPCL-TCP) scaffolds wrapped in vascularised free corticoperiosteal flaps.

OUTCOME

Functional volumes of load-sharing regenerate bone have formed in all cases after a moderate duration of follow-up. At 36 cm, case 1 remains the longest segment of load bearing bone ever successfully reconstructed. This technique offers an alternative to existing methods of large volume bone defect reconstruction that may be safe, reliable, and give predictable outcomes in challenging situations. It achieves this by using a bioresorbable scaffold to support and direct the growth of regenerate bone, driven by RMAV.

CONCLUSION

This technique may facilitate the reconstruction of bone defects previously thought unreconstructable, reduce the risk of long-term implant-related complications and achieve these outcomes in a hostile environment. These potential benefits must now be formally tested in prospective clinical trials.

A Retrospective Study of Complications in Cranioplasty: 7-Year Period

Objective

To discuss the intraoperative and postoperative complications of cranioplasty and management during a 7-year period.

Method

Retrospective study of 7-year period of 63 patients including both male and female.

Results

Highest experienced complications were seizures and dural tear, i.e., 6%, followed by EDH in 3% patients, hydrocephalus and pneumocephalus combined 3%, 1.6% CSF collection and flap necrosis each. All the complications were managed successfully.

Conclusion

Complications of cranioplasty can be managed by following sound surgical principles. Serious complications like meningitis, air embolism and death are rare.

Pediatric Cranial Defects: What Size Warrants Repair?

PURPOSE

Identifying which cranial defects among children warrant surgical repair is integral to providing adequate protection of the skull whereas minimizing exposure to surgical complications. This review examines the available evidence regarding the role of defect size in determining the appropriateness of nonsurgical versus surgical management.

METHODS

An electronic literature review was performed using PubMed and Google Scholar to identify publications that provided rationales for nonsurgical management of cranial defects in the pediatric population based on size. Titles and abstracts were reviewed by the authors to determine eligibility for full-text analysis. Ineligible studies were categorized and relevant data from fully analyzed texts were recorded.

RESULTS

Of the 523 articles that were reviewed, 500 were ineligible for full-text analysis due to the following most common reasons: no cranial defect described (227, 45%), did not discuss management of cranial defects (68, 14%), or surgery was performed on all defects in evaluation of a technique or protocol (86, 17%). Ten publications provided relevant data. The suggested size below which surgery was not recommended varied widely between articles. Beyond the age of 1 to 2 years, no general agreement on recommended management in children was found. Craniofacial surgeons had divergent views on the minimum diameter for a "critical" defect and the size for which surgical repair is necessary.

CONCLUSIONS

Little guidance or consensus exists regarding the indications for surgical correction of cranial defects based on the size of the defect. Objective data is needed to classify "clinically critical defects" in the pediatric population.

Custom-made Hydroxyapatite Cranioplasty: Radiological and Histological Evidence of Bone-Biomaterial Osteointegration in Five Patients

Custom-made cranial implants facilitate the surgical reconstruction of destructive pathologies of the skull or extensive demolitive skull surgery. Customized cranioplasty allows for an immediate restoration of the functional integrity of the cranial defect (restitutio ad integrum), with excellent functional and esthetic outcome and a quick, safe, and simple procedure. In this context, bioceramics like hydroxyapatite (HA) claim high biocompatibility and bone-binding capability. The osteoconductive properties of the HA have been reported in animal models and humans. The purpose of this study is to demonstrate with radiological and histological examination and how HA prosthesis may integrate after their implantation showing data related to five patients that needed primary HA cranial reconstruction with secondary removal after few years. The histological examination showed neo-formed lamellar/trabecular bone tissue fragments accompanied by the amorphous reticular tissue (HA prosthesis) revealing diffuse ossification sites in all included cases.