Cranioplasty Introduction Cranial defect Indications Contraindications Graft Definition Cranioplasty is a neurosurgical procedure to repair cranial defects to restore functional anatomy preventing any neurological drawbacks and taking into account the cosmetic issues. History Archeological evidence has demonstrated that cranioplasty dates back to 7000 BC → gold, gourds Aetiology Trauma (including electrical burns), tumours, infections, radionecrosis, congenital anomalies (cf CANTIBED) Preamble 65% of DC are secondary to TBI or strokes Summary: cosmesis, relief, protection, others Cosmesis (restoration of external skull symmetry) Brain protection from trauma Relief of symptoms due to defect (pain, syndrome of the trephined, sinking skin syndrome, seizures) Others: restoration of the dynamics of a closed cavity by eliminating influence of atm pressure Prevent pseudo-meningocele formation Syndrome of the trephined: definition I = headaches, dizziness, intolerance of vibration and noise, irritability, fatigability, loss of motivation and concentration, depression, and anxiety; definition II = any symptoms reversible with cranioplasty Flopping syndrome: flap collapsing in the erect position and bulging in the supine position (Indian) Infection, hydrocephalus, and brain swelling Ideal Qualities: strong, lightweight, malleable, thermally non-conductive, sterilizable, radiolucent, aesthetically good, easily secured, inert, non-magnetic, readily available, inexpensive, resistant to biomechanical processes Classification Preamble Broad categorization: autologous and synthetic Autologous Previously removed bone flap, split-thickness bone graft/calvaria, ribs, fibula Biocompatible Risk of bone resorption Remains the most used material across the world Relatively low cost, depending on the method of storage/preservation Isograft Genetically-identical; monozygotic twins Allograft Same species, different individual Xenograft Other species: ox horn, buffalo horn, and ivory were used with satisfactory results Bone substitutes Preamble Alloplastic bone graft: are synthetic, inorganic, biocompatible, and bioactive bone substitutes that are believed to promote healing of bone defects through osteoconduction. Polymer PMMA Bio-inert, no exothermic reaction, easy to contour Hand-formed, pre-fabricated, templated Antibiotic incorporation through soaking—beneficial for the management of repeat procedure secondary to infection Widely used, low cost PEEK Bio-inert, mechanically resistant Lack of long-term studies In-house sterilization required Ceramic/polymer Porous HA (Porous hydroxyapatite); bioceramic porous material Metal Graft storage In vivo medium Ex vivo medium Operative principles Timing Pre-op planning Technique Post-op Titanium Close biomimetic characteristics of the bone Customizable Shown to have a positive impact on bone generation and repair Biocompatible, non-corrosive and non-ferromagnetic Mechanically resistant Plate, mesh Options for manufacture: plate, mesh, or a 3D porous implant. Associated with better cosmetic and functional outcomes High cost Tantalum Aluminum Adjuncts 3D prosthesis/molds Abdominal or thigh subcutaneous pouches Provides a sterile environment but requires further operation(s) in the abdomen/thigh. Deep freezing (cryopreservation) (temperature of at ≤−80oC) and tissue banking Has been correlated with devitalization of tissue, with the potential for ↑ed risk of bone resorption. However, a recent systematic review by Corliss et al. found no statistically significant differences in terms of infection and resorption rates while comparing the two methods of storage. Preamble Delineation of the threshold for “early” and “late” cranioplasty has classically come at, before, and after 12 weeks, but this is continuously challenged. A recent international consensus meeting → 4x time frames were agreed upon (86.8% agreement): Overlying scalp must be well healed and vascularized Intracranial pressure stabilized Infections (both systemic and cranial) fully treated Ultra-early Up to 6 weeks; easier discrimination of tissue layers Early 6 weeks to 3 months Intermediate 3 – 6 months Delayed More than 6 months Head CT + 3D reconstruction, ± brain MRI if ?soft tissue relationship, r/o contra-indications Titanium cranioplasty: Computer-generated 3D image of the skull → 3D-printing of the defect → laboratory (wax the defect) → plaster room (press, shape, cut, adjust the titanium plate) Incision follows prior incision Separate the temporalis muscle from where it has scarred onto the dura Avoid CSF leak by not violating the dura (or pseudo-dura) or by closing any opening that is identified (Protect brain from exothermic reaction if using heat cure resin) Repair the bone defect available option; perforate to prevent fluid accumulation Replace the temporalis muscle outside the bone graft and, if necessary, tack it into position Definitions** Hand-formed is defined as a cranioplasty implant formed intra-operatively by the surgeon using no specialized tools Prefabricated is defined as a cranioplasty implant which has been manufactured independent from and prior to the surgical procedure Templated is defined as a cranioplasty implant formed intra-operatively by the surgeon using specialized, prefabricated tools.
