Effectiveness of 3D Bone Matrix in Cranioplasty

The study will be a parallel-arm clinical trial (8 patients randomly divided into 2 groups), where the participants will be patients with cranial defects requiring cranioplasty at the Department of Neurosurgery of Base Hospital of Valdivia, Chile. Previously, data of each participant will be collected, such as sex, age, basic comorbidities and clinical diagnosis.

The outcome variables to be considered in this study are: The volume of bone reconstruction measure in axial computed tomography (CT) using the tool available in Mimics software delivering the value in cm3 , and the scaffold attachment to adjacent bone using the linear density scale in Hounsfield units (HU) where it will be considered from +3000 HU as dense bone formation and presence of GAP \<1mm. The last variable will be the patients' perception of esthetics and quality of life, which will be measured using the "QOLIBRI" scale, where the items with the greatest difference in scores between the two groups will be highlighted; in addition, \>80 total points will be considered as good quality of life.

Sample calculation: Considering the need to observe the maintenance of skull volume in functional and aesthetic aspects, according to the results of Park et al., the use of PCL/ß-TCP material observed a volume difference of 4.4 ± 2.5% at six months postoperatively versus the average initial volume, calculating the need for four study subjects per group (Effect size d= 1. 76; alpha error probability= 0.05; Power= 0.7; Allocation ratio N2/N1= 1. G\*Power software U. Düsseldorf) An experimental group (PCL scaffold + β-TCP) and a control group (PMMA cement).

Surgical intervention PCL + β-TCP intervention protocol: Prior to surgery, the patient must answer a survey of concept of quality of life through the QOLIBRI guideline, followed by this the patient will undergo an initial CT scan where the necessary measurements of the bone defect will be performed to transfer this information to a graphic design software such as CAD 3D, the design and printing of the PCL + β-TCP segment will be performed in the Polymer Laboratory of the Universidad Austral de Chile, once obtained the digital files will be converted to a printable format (.gcode) compatible with fused deposition 3D equipment (FDM), using the Creality Ender-3 printer with PCL filament from Canada Filament Store with a diameter of 1.75 mm.

Subsequently, the prototype will be obtained where it will be verified that the graft has the required characteristics for each patient. Once this is approved, the sterilization protocol of the PCL+ß-TCP matrices will be carried out, which will be placed in a container with 70% ethanol and submerged for 15 minutes, after which time they will be placed on sterile absorbent paper to eliminate excesses. Finally, the scaffolds are exposed to UV light for 20 minutes. Finally, the matrices are packed. Then the surgery will be performed and a control CT scan will be taken 6 months after the intervention, together with the second QOLIBRI guideline.

PMMA surgical cement intervention protocol: The initial CT scan will be performed on each patient, then intraoperatively, the solid and liquid component of the PMAA cement will be mixed with enveloping movements until a homogeneous mass will be obtained that allows molding, With the surgical gloves moistened with physiological solution, the molding of the intraoperative PMMA platelet begins, taking the bone defect as a reference, looking for a thickness similar to the adjacent bone of the bone defect, previously, placing a latex patch (included with the PMMA prosthesis) protects the brain tissue. When the plate begins to increase its temperature during the exothermic polymerization process, it is removed from the surgical field and once the formed platelet is solid and cold, it is placed again in the bone defect, in order to adhere to the bone of the cranial calotte by means of a titanium fixation system. All patients are monitored in the intensive care unit for at least 24 hours in the immediate postoperative period, where a clinical and radiological (CT) follow-up will be performed to rule out ongoing clinical complications. Finally, a control CT scan will be taken 6 months after the intervention, together with the second QOLIBRI guideline.

• Perception of aesthetics and quality of life [Time frame: 6 months]