Current Concepts in Restoring Acquired Cranial Defects

Cranioplasty in Oman: Retrospective review of cases from the National Craniofacial Center 2012-2022

Objectives

Cranioplasty is a complex craniofacial and neurosurgical procedure that aims to reinstate the architecture of the cranial vault and elevate both its aesthetic and neurological function. Several reconstructive materials have been thoroughly explored in the search for the optimal solution for cranioplasty. This study aimed to evaluate different material used for cranial reconstruction in Oman.

Methods

This retrospective study included all patients who had had cranioplasty procedures performed at Khoula Hospital, Muscat, Oman, from 2012 to 2022. Demographic information, the characteristics of the cranial defect and any complications that occurred post-operatively were analysed.

Results

A total of 47 patients were included in this study. The most common cause of cranial defects was craniectomy following traumatic head injury (70.2%) along with excision of fibrous dysplasia (10.6%). The most frequently utilised material for cranial repair was autologous bone grafts (n = 28), followed by polyetheretherketone (PEEK; n = 14). Interestingly, the replacement of bone grafts from previous craniectomy showed a notably high resorption rate (71.4%), in contrast to split calvarial grafts (0%) and other types of bone grafts (14.3%). Additionally, delayed graft infection was observed in 3.6% of the bone graft group and 7.1% of the PEEK group.

Conclusion

Patient-specific alloplastic implants such as PEEK have gained popularity for large and complex cranioplasty, as they provide excellent aesthetic outcomes and leave no donor site morbidity. In contrast, bone grafts remain the gold standard for small to medium-sized cranial defects.

The Multiple Rib Osteomyocutaneous Split Latissimus Dorsi Flap for Calvarial Reconstruction: Indication, Operative Technique, and Review of Literature

Major complex cranial defects may be challenging for the reconstructive microsurgeon. Affected patients often present with impaired soft tissues including dura exposure or fistulas. The lacking structural bony support may cause severe neurological issues and in select patients, there is a need for well-vascularized autologous tissue repair. The authors herein elucidate the role of the multiple rib osteomyocutaneous split latissimus dorsi flap for reconstruction of composite skull defects, providing an indication, an exemplary case, operation technique, and literature review. A 40-year-old woman after anaplastic oligodendroglioma resection suffered multiple extrusions and allograft cranioplasty infections. The defect was reconstructed with an osteomyocutaneus split latissimus dorsi flap including costae 3 ribs and a skin island. The included ribs were nourished via the anterior periosteum, while the posterior periosteum was left in place for the protection of the pleura parietalis. A proper amount of craniomedial latissimus dorsi muscle was spared to reduce donor site morbidity. The patient presented after 6 months with stable bony and soft tissue conditions without neurological symptoms, and acceptable donor site morbidity. After failed alloplastic cranioplasties, the free latissimus dorsi flap including vascularized ribs is well suitable for coverage of large compound cranial defects, providing skeletal support, improved contour, and enhanced functional outcome.

Diversifying the rehabilitation of calvarial defects: Rejuvenating precision: A case series

Cranial vault defects are either congenital or acquired in origin. Cranioplasty is most commonly done in patients after trauma, decompressive craniectomies, tumor resections, infections or because of congenital malformations. The purpose of a Cranioplast is to protect the underlying brain tissues, reduce pain, and to improve the calvarial contour, symmetry, and esthetics. Rehabilitation of these defects possesses a challenge to the surgical team and prosthodontist. With advancement in three-dimensional (3D) engineering technology, the use of rapid prototyping technology (RPT) can be used in the fabrication of 3D skull eliminating conventional impression for recording defect region. Custom-made cranial prosthesis now can be fabricated using the conventional method of wax-up and lost-wax method. Case 1 had a history of road traffic accident followed by decompressive craniectomy, which led to frontoparietotemporal defect of the right side. The 3D model was fabricated using RPT technology. The wax pattern fabricated on 3D prototyped skull was contoured using digital photographic superimposition method. Case 2 had a history of trauma on the head causing intracerebral hemorrhage followed by decompressive craniectomy which led to frontoparietotemporal defect of the right side. The 3D model was fabricated using RPT. The wax pattern fabricated on 3D prototyped skull was contoured using the compass method. The use of these methods with the added advantage of RPT resulted in prosthesis with good esthetics and better fit. The contour of the prosthesis was replicated in the same manner as compared to the contralateral side. These techniques are easy to use and are less time consuming and had few chances of errors.

Load-Bearing Capacity and Design Advantages of a Custom-Made, Thin Pure-Titanium Cranioplasty (CranioTop)

BACKGROUND

Adequate and stable coverage of cranial contour and continuity defects of any origin is a common challenge in neurosurgical clinics. This study presents the results of investigations concerning the mechanical load-bearing capacity and design advantages of custom-made implants made from a thin, pure-titanium sheet (CranioTop) (CLinstruments, Attendorn, Germany) for covering complex cranial defects.

METHODS

In 9 test series, the stability of three differently shaped and sized thin titanium sheet implants was tested using vertical, uniaxial compression with 3 different compression stamps, to investigate the behaviour of these implants in relation to punctiform as well as planar forces.

RESULTS

All 9 model implants showed elastic behavior in the synchronously recorded force/displacement diagrams at an impression of up to 2 mm. The forces at 2 mm deformation were between 170.1 and 702.7 Newton.

CONCLUSION

Cranioplasty using CranioTop is a stable procedure for covering skull defects, even those of large dimensions. An added advantage is the significant reduction in effort required to prepare the area of the bone margins compared to other current techniques of cranioplasty.

Case report: chronic inflammatory ulcer and osteoradionecrosis of the skull following radiotherapy in early childhood

INTRODUCTION

Chronic inflammatory diseases of the skin are the most common differential diagnosis of tumorous lesions of the craniofacial region. Detailed information about a patient's medical history is important for the clinical diagnosis of such cases. Previous radiotherapy should be taken into account, especially in cases of chronic dermatitis, since complications include osteoradionecrois of the adjacent bone strucutres with surrounding inflammation.

CASE REPORT

We present the case of a 77-year-old femal patient who was admitted to our department with a slightly progressive ulcerating lesion of the frontotemporal skull. The patient had received radiotherapy in early childhood as primary therapy for hemangioma. Diagnostic imaging and biopsies revealed a diagnosis of chronic ulceration with underlying osteonecrosis and fibrotic osteomyelitis of the skull. A complex reconstruction of osseous structures and soft tissue was necessary to resolve her complaints.

CONCLUSION

Chronic radiodermatitis and osteoradionecrosis in adults, occurring as late complications, are uncommon, but can be observed even nearly 80 years after radiation. Large defects of the skull require a complete reconstruction to avoid several complications.

Rapid prototyping technology for cranioplasty: A case series

Cranial vault defects may be acquired or congenital in origin. Rehabilitation of these patients often poses challenge to the operating team and prosthodontist. Polymethylmethacrylate is a commonly used alloplastic graft material which is used for the fabrication of cranial prosthesis. Nowadays, with the advancement in the bioengineering, custom-made template and cranial prosthesis can be made by rapid prototyping technology (RPT) by patient three-dimensional (3D) computed tomography (CT) scan images. This series of two cases explained two different techniques for the rehabilitation of the patient with frontotemporoparietal cranial defect. Case 1 had a history of cerebrovascular accident, followed by decompression craniotomy which led to frontotemporoparietal defect of the left side. This defect area was associated with the cerebrospinal fluid accumulation which made delineation of underlying bony margins difficult and interfered with conventional impression procedures. Case 2 had a road traffic accident which led to intracerebral hemorrhage followed by decompression craniotomy which resulted in frontotemporoparietal defect of the right side. The patient had a poor neuromuscular control which impedes with the upright posture of the head during impression making of the defect area. Therefore, these cases were planned to rehabilitate by RPT. In these techniques, the prosthesis was made using custom-made skull template produced by RPT, using the data of 3D-CT scan images. This technique resulted in the prosthesis with good esthetics and better fit of the prosthesis. The contours of the prosthesis were replicated in the same manner as compared to the contralateral side. RPT is an additive manufacturing technology which is now used in the field of dentistry too. This technique is easy to use; fabricate prosthesis with high precision is less time-consuming and has fewer chances of error.

3D printing of hybrid biomaterials for bone tissue engineering: Calcium-polyphosphate microparticles encapsulated by polycaprolactone

Here we describe the formulation of a morphogenetically active bio-ink consisting of amorphous microparticles (MP) prepared from Ca²⁺ and the physiological inorganic polymer, polyphosphate (polyP). Those MP had been fortified by mixing with poly-ε-caprolactone (PCL) to allow 3D-bioprinting. The resulting granular PCL/Ca-polyP-MP hybrid material, liquefied by short-time heating to 100 °C, was used for the 3D-printing of tissue-like scaffolds formed by strands with a thickness of 400 µm and a stacked architecture leaving ≈0.5 mm²-sized open holes enabling cell migration. The printed composite scaffold turned out to combine suitable biomechanical properties (Young's modulus of 1.60 ± 0.1 GPa; Martens hardness of 153 ± 28 MPa), matching those of cortical and trabecular bone, with morphogenetic activity. This scaffold was capable of attracting and promoting the growth of human bone-related SaOS-2 cells as demonstrated by staining for cell viability (Calcein AM), cell density (DRAQ5) and SEM studies. Furthermore, the hybrid material was demonstrated to upregulate the steady-state-expression of the cell migration-inducing chemokine SDF-1α. EDX analysis and FTIR measurements revealed the presence of hydroxyapatite in the mineral deposits formed on the scaffold surface. Based on the results we conclude that granular PCL/Ca-polyP-MP hybrid material is suitable for the fabrication of bioprintable scaffold which comprises not only biomechanical stability but also morphogenetic potential.

STATEMENT OF SIGNIFICANCE

In present-day regenerative engineering efforts, biomaterial- and cell-based strategies are proposed that meet the required functional and spatial characteristics and variations, especially in the transition regions between soft (cartilage, tendon or ligament) and hard (bone) tissues. In a biomimetic approach we succeeded to fabricate amorphous Ca-polyP nanoparticles/microparticles which are highly biocompatible. Together with polycaprolactone (PCL), polyP can be bio-printed. This hybrid material attracts the cells, as documented optically as well as by a gene-expression studies. Since PCL is already a FDA-approved organic and inert polymer and polyP a physiological biologically active component this new bio-hybrid material has the potential to restore physiological functions, including bone remodelling and regeneration if used as implant.

The effect of manufacturing techniques on custom-made titanium cranioplasty plates: A pilot study

OBJECTIVE

This study investigated the effect of varying techniques on the surface characteristics of pressed titanium cranioplasty plates, commonly manufactured in laboratory practice. The aim was to highlight the variety of techniques currently used, assess these methods of manufacture and produce manufacturing recommendations.

METHODS

A questionnaire identified manufacturing methods commonly used by maxillofacial prosthetists. The plate surfaces were examined using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometry. The surface differences and titanium compositions were statistically analysed.

RESULTS

Bead blasting with aluminium oxide (Al₂O₃) showed a significant decrease (p < 0.001) in titanium surface composition, replaced by a large aluminium content. Trimming tool choice had a significant impact (p = 0.001) on surface contamination by smoothing wheel material deposition; however passivation and anodising techniques had no significant effect (p = 0.293 and p = 0.257, respectively) on the surface composition or roughness of titanium samples.

CONCLUSIONS

A large range of manufacturing techniques of titanium cranioplasty plates was confirmed and significant differences were found. Amongst other recommendations, bead blasting with Al₂O₃ is not recommended for commercially pure titanium implant surface finishing due to aluminium contamination. The recommendations outlined will minimise manufacturing time, reduce risk of complication (thus costs) and unify methods to enable a safe, reliable treatment.

Comparison of Complications Following Cranioplasty Using a Sterilized Autologous Bone Flap or Polymethyl Methacrylate

Objective

The aims of current study are to compare complications following cranioplasty (CP) using either sterilized autologous bone or polymethyl methacrylate (PMMA), and to identify the risk factors for two of the most common complications: bone flap resorption (BFR) and surgical site infection (SSI).

Methods

Between January 2004 and December 2013, 127 patients underwent CP and were followed at least 12 months. Variables, including sex, age, initial diagnosis, time interval between decompressive craniectomy (DC) and CP, operation time, size of bone flap, and presence of ventriculo-peritoneal shunt, were analyzed to identify the risk factors for BFR and SSI.

Results

A total of 97 (76.4%) patients underwent CP using PMMA (Group I) and 30 (23.6%) underwent CP using autologous bone (Group II). SSI occurred in 8 (8.2%) patients in Group I, and in 2 (6.7%) in Group II; there was no statistically significant difference between the groups (p=1.00). No statistically significant risk factors for SSI were found in either group. In Group I, there was no reported case of BFR. In Group II patients, BFR developed in 18 (60.0%) patients at the time of CP (Type 1 BFR), and at 12-month follow up (Type 2 BFR) in 4 (13.3%) patients. No statistically significant risk factors for BFR were found in Group II.

Conclusion

CP using sterilized autologous bone result in a significant rate of BFR. PMMA, however, is a safe alloplastic material for CP, as it has low complication rate.

Review of Cranioplasty after Decompressive Craniectomy

Cranioplasty is an in evitable operation conducted after decompressive craniectomy (DC). The primary goals of cranioplasty after DC are to protect the brain, achieve a natural appearance and prevent sinking skin flap syndrome (or syndrome of the trephined). Furthermore, restoring patients' functional outcome and supplementing external defects helps patients improve their self-esteem. Although early cranioplasty is preferred in recent year, optimal timing for cranioplasty remains a controversial topic. Autologous bone flaps are the most ideal substitute for cranioplasty. Complications associated with cranioplasty are also variable, however, post-surgical infection is most common. Many new materials and techniques for cranioplasty are introduced. Cost-benefit analysis of these new materials and techniques can result in different outcomes from different healthcare systems.