Evaluation of implant properties, safety profile and clinical efficacy of patient-specific acrylic prosthesis in cranioplasty using 3D binderjet printed cranium model: A pilot study

There exists a significant demand to develop patient-specific prosthesis in reconstruction of cranial vaults after decompressive craniectomy. we report here, the outcomes of an unicentric pilot study on acrylic cranial prosthesis fabricated using a 3D printed cranium model with its clinically relevant mechanical properties.

METHODS

The semi-crystalline polymethyl methacrylate (PMMA) implants, shaped to the cranial defects of 3D printed cranium model, were implanted in 10 patients (mean age, 40.8 ± 14.8 years). A binderjet 3D printer was used to create patient-specific mould and PMMA was casted to fabricate prosthesis which was analyzed for microstructure and properties. Patients were followed up for allergy, infection and cosmesis for a period of 6 months.

RESULTS

As-cast PMMA flap exhibited hardness of 15.8 ± 0.24Hv, tensile strength of 30.7 ± 3.9 MPa and elastic modulus of 1.5 ± 0.1 GPa. 3D microstructure of the semi-crystalline acrylic implant revealed 2.5-15 µm spherical isolated pores. The mean area of the calvarial defect in craniectomy patients was 94.7 ± 17.4 cm². We achieved a cranial index of symmetry (CIS -%) of 94.5 ± 3.9, while the average post-operative Glasgow outcome scale (GOS) score recorded was 4.2 ± 0.9.

CONCLUSIONS

3D printing based patient-specific design and fabrication of acrylic cranioplasty implant is safe and achieves acceptable cosmetic and clinical outcomes in patients with decompressive craniectomy. Our study ensured clinically acceptable structural and mechanical properties of implanted PMMA, suggesting that a low cost 3D printer based PMMA flap is an affordable option for cranioplasty in resource constrained settings.

Real-time respiratory monitoring workstation--software and hardware engineering aspects

We have applied advanced real-time techniques in software, that are intensively used in critical areas like space research and defence applications, to realise an Integrated Real-Time Respiratory Monitoring System at the Thorax Anesthesiology, Academic Hospital Rotterdam. The system is called the 'SERVO WINDOW'--a window to the servo ventilator. The heart of the system is a real-time kernel that uses preemptive scheduling to achieve multitasking on a IBM PC compatible hardware platform. To the clinician this means that he gets all relevant information from one source i.e. the Respiratory Workstation. The waveforms of the airway pressure, airway flow and the expired CO2 curve are displayed continuously on the screen. The Vector Loops like Pressure Volume, Flow Pressure and Flow Volume loops are also available in addition to the lung mechanics parameters like Expiratory and Inspiratory Resistances, Compliances, Peak Pressure, PEEP, etc. The Single Breath Diagram i.e. expired CO2 concentration versus volume and dead space ventilation is also calculated. The blood gas analysis data is plotted in convenient diagrams like the O2-CO2 diagram, Oxygen Chart, etc. The trend of all these parameters are available with a granularity of one minute. An industry standard laser printer is used for report generation to produce reports of the real-time waveforms, parameter values and the trends. User interface is through easy menus with the traditional keyboard, touchscreen including keyboard on screen for data entry and the mouse.

Breath detection algorithm in digital computers

An algorithm for the detection and delineation of breaths is described. The proposed algorithm takes into account the different, common modes of ventilation like the pressure controlled, volume controlled and patient triggered modes of ventilation. Airway flow curve is used as the basic delineator and the airway pressure and the Co2 concentration curves are used to confirm the delineation. A flow chart is also included to explain the algorithm. The detailed explanation and modifications, for additional confirmation and for the selections of constants, to check for the rise or fall of the pressure and Co2 curves, are also included.