Reconstruction of Secondary Calvarial Defects with Ex Situ Split Calvarial Bone Grafts: Long-Term Evaluation of Outcomes

Generative design approach to combine architected Voronoi foams with porous collagen scaffolds to create a tunable composite biomaterial

Regenerative biomaterials for musculoskeletal defects must address multi-scale mechanical challenges. Repairing craniomaxillofacial bone defects, which are often large and irregularly shaped, requires close conformal contact between implant and defect margins to aid healing. While mineralized collagen scaffolds can promote mesenchymal stem cell osteogenic differentiation in vitro and bone formation in vivo, their mechanical performance is insufficient for surgical translation. We report a generative design approach to create scaffold-mesh composites by embedding a macro-scale polymeric Voronoi mesh into the mineralized collagen scaffold. The mechanics of architected foam reinforced composites are defined by a rigorous predictive moduli equation. We show biphasic composites localize strain during loading. Further, planar and 3D mesh-scaffold composites can be rapidly shaped to aid conformal fitting. Voronoi-based composites overcome traditional porosity-mechanics relationship limits while enabling rapid shaping of regenerative implants to conformally fit complex defects unique for individual patients. STATEMENT OF SIGNIFICANCE: Biomaterial strategies for (craniomaxillofacial) bone regeneration are often limited by the size and complex geometry of the defects. Voronoi structures are open-cell foams with tunable mechanical properties which have primarily been used computationally. We describe generative design strategies to create Voronoi foams via 3D-printing then embed them into an osteogenic mineralized collagen scaffold to form a multi-scale composite biomaterial. Voronoi structures have predictable and tailorable moduli, permit stain localization to defined regions of the composite, and permit conformal fitting to effect margins to aid surgical practicality and improve host-biomaterial interactions. Multi-scale composites based on Voronoi foams represent an adaptable design approach to address significant challenges to large-scale bone repair.

Generative design approach to combine architected Voronoi foams with porous collagen scaffolds to create a tunable composite biomaterial

Regenerative biomaterials for musculoskeletal defects must address multi-scale mechanical challenges. We are developing biomaterials for craniomaxillofacial bone defects that are often large and irregularly shaped. These require close conformal contact between implant and defect margins to aid healing. While we have identified a mineralized collagen scaffold that promotes mesenchymal stem cell osteogenic differentiation in vitro and bone formation in vivo, its mechanical performance is insufficient for surgical translation. We report a generative design approach to create scaffold-mesh composites by embedding a macro-scale polymeric Voronoi mesh into the mineralized collagen scaffold. The mechanics of architected foam reinforced composites are defined by a rigorous predictive moduli equation. We show biphasic composites localize strain during loading. Further, planar and 3D mesh-scaffold composites can be rapidly shaped to aid conformal fitting. Voronoi-based composites overcome traditional porosity-mechanics relationship limits while enabling rapid shaping of regenerative implants to conformally fit complex defects unique for individual patients.

Unveiling the "Kebab" technique: A case report on a two-stage reconstruction method for repeated complex cranioplasty

RATIONALE

Cranioplasty after decompressive craniectomy provides brain protection and improves cerebral hemodynamics. However, recurrent infection and sinking skin flap syndrome after cranioplasty remain cumbersome complications that require a well-planned reconstruction strategy.

PATIENT CONCERNS

A 74-year-old man presented with traumatic subdural hematoma and underwent decompressive craniectomy. Cranioplasty using an original bone flap, bone cement with wires, and a titanium mesh were complicated and resulted in recalcitrant infection and sinking skin flap syndrome.

DIAGNOSES

Recurrent infection and sinking skin flap syndrome post-cranioplasty.

INTERVENTIONS

We designed a two-stage "kebab" reconstruction technique using a combination of free latissimus dorsi myocutaneous flap and delayed non-vascularized free rib graft. A well-vascularized musculocutaneous flap can obliterate dead space in skull defects and reduce bacterial inoculation in deep infections. Subsequently, delayed rib grafts act as the scaffold to expand the sunken scalp flap.

OUTCOMES

At the 3-year follow-up, the patient showed improvement in headache, without evidence of surgical site infection.

LESSONS

The novel "kebab" technique using a combination of a free myocutaneous flap and delayed rib graft can eliminate bacterial growth in infected calvarial defects, reverse sinking skin flap syndrome, and minimize potential donor-site morbidity, and is therefore suitable for patients who require multiple cranioplasties and are unable to withstand major reconstructions.

Autologous bone fragments for skull reconstruction after microvascular decompression

Background

Various methods are used to reconstruct the skull after microvascular decompression, giving their own advantages and disadvantages. The objective of this study was to evaluate the efficacy of using autologous bone fragments for skull reconstruction after microvascular decompression.

Methods

The clinical and follow-up data of 145 patients who underwent microvascular decompression and skull reconstruction using autologous bone fragments in our hospital from September 2020 to September 2021 were retrospectively analyzed.

Results

Three patients (2.06%) had delayed wound healing after surgery and were discharged after wound cleaning. No patient developed postoperative cerebrospinal fluid leakage, incisional dehiscence, or intracranial infection. Eighty-five (58.62%) patients underwent follow-up cranial computed tomography at 1 year postoperatively, showed excellent skull reconstruction. And, the longer the follow-up period, the more satisfactory the cranial repair. Two patients underwent re-operation for recurrence of hemifacial spasm, and intraoperative observation revealed that the initial skull defect was filled with new skull bone.

Conclusion

The use of autologous bone fragments for skull reconstruction after microvascular decompression is safe and feasible, with few postoperative wound complications and excellent long-term repair results.

Decision-Making in Adult Cranial Vault Reconstruction

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Define and classify different types of cranial defects 2. Compare both autologous and alloplastic options for reconstruction 3. Develop an optimal approach for cranial vault reconstruction in various clinical scenarios.

SUMMARY

Defects of the cranium result from various causes, including traumatic loss, neurosurgical intervention, skull tumors, and infection. Cranial vault reconstruction aims to restore both the structural integrity and surface morphology of the skull. To ensure a successful outcome, the choice of appropriate cranioplasty reconstruction will vary primarily based on the cause, location, and size of the defect. Other relevant factors that must be considered include adequacy of soft-tissue coverage, presence of infection, and previous or planned radiation therapy. This article presents an algorithm for the reconstruction of various cranial defects using both autologous and alloplastic techniques, with a comparison of their advantages and disadvantages.

Long-term Effect of Cranioplasty on Overlying Scalp Atrophy

Scalp thinning over a cranioplasty can lead to complex wound problems, such as extrusion and infection. However, the details of this process remain unknown. The aim of this study was to describe long-term soft-tissue changes over various cranioplasty materials and to examine risk factors associated with accelerated scalp thinning.