T he reconstruction of a skull vault defect, termed cranioplasty, has a rich and fascinating history. For at least 5 millennia, surgeons have patched cranial defects with an immensely diverse range of materials ranging from fruit shells to sheep scapulae and man-made plastics. 42 Even today, the pursuit of the perfect cranioplasty material and technique continues.Skull defects are often the direct result of surgical decompressive craniectomy performed for acute neurosurgical emergencies. 23 The use of a patient's original bone flap for cranioplasty is theoretically sound and avoids the problems related to the use of bone from other sources, such as human cadavers (allografts) or animals (xenografts), or the use of synthetic materials. In practice, however, cranioplasty using these bone flaps, which have been stored for a period of time either in a surgically created subcutaneous pocket or in a medical freezer, is plagued with a not insignificant risk of infections and bony resorption. 8,11,22 With unnatural storage, the nature and content of these bone flaps are changed permanently, hindering successful reincorporation as part of the skull vault. Loss of osteogenesis probably plays a role; studies on human calvarial bone flaps have shown a diminution of osteoblasts after both subcutaneous 44 The feasibility of producing patient-specific acrylic cranioplasty implants with a low-cost 3D printer eddie t. w. tan, mrcsed, Ji min ling, mrcsed, and shree Kumar dinesh, FrcsDepartment of Neurosurgery, National Neuroscience Institute, Singapore obJective Commercially available, preformed patient-specific cranioplasty implants are anatomically accurate but costly. Acrylic bone cement is a commonly used alternative. However, the manual shaping of the bone cement is difficult and may not lead to a satisfactory implant in some cases. The object of this study was to determine the feasibility of fabricating molds using a commercial low-cost 3D printer for the purpose of producing patient-specific acrylic cranioplasty implants. methods Using data from a high-resolution brain CT scan of a patient with a calvarial defect posthemicraniectomy, a skull phantom and a mold were generated with computer software and fabricated with the 3D printer using the fused deposition modeling method. The mold was used as a template to shape the acrylic implant, which was formed via a polymerization reaction. The resulting implant was fitted to the skull phantom and the cranial index of symmetry was determined. results The skull phantom and mold were successfully fabricated with the 3D printer. The application of acrylic bone cement to the mold was simple and straightforward. The resulting implant did not require further adjustment or drilling prior to being fitted to the skull phantom. The cranial index of symmetry was 96.2% (the cranial index of symmetry is 100% for a perfectly symmetrical skull). coNclusioNs This study showed that it is feasible to produce patient-specific acrylic cranioplasty implants with a low-cost 3D printer. Further studies...

Transpedicular screw fixation is generally feasible in our population except for 8 % with at least one PW < 4.00 mm. However, in view of significant sex and ethnic morphometric variability, pre-operative CT evaluation together with image-guided screw placement is highly advised to ensure safety and accuracy.

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The COVID-19 pandemic creates unique challenges in the practice of spinal surgery. We aim to show how the use of a high-definition 3D digital exoscope can help streamline workflows, and protect both patients and healthcare staff.

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