Three-Dimensional CAD in Skull Reconstruction: A Narrative Review with Focus on Cranioplasty and Its Potential Relevance to Brain Sciences

Woon-Man Kung,Muh-Shi Lin,I-Shiang Tzeng

doi:10.3390/app10051847

Abstract

In patients suffering from severe traumatic brain injury and massive stroke (hemorrhagic or ischemic), decompressive craniectomy (DC) is a surgical strategy used to reduce intracranial pressure, and to prevent brainstem compromise from subsequent brain edema. In surviving patients, cranioplasty surgery helps to protect brain tissue, and correct the external deformity. The aesthetic outcome of cranioplasty using an asymmetrical implant can negatively influence patients physically and mentally, especially young patients. Advancements in the development of biomaterials have now made three-dimensional (3-D) computer-assisted design/manufacturing (CAD/CAM)-fabricated implants an optimal choice for the repair of skull defects following DC. Here, we summarize the various materials for cranioplasty, including xenogeneic, autogenous, and alloplastic grafts. The processing procedures of the CAD/CAM technique are briefly outlined, and reflected our experiences to reconstruct skull CAD models using commercial software, published previously, to assess aesthetic outcomes of regular 3-D CAD models without contouring elevation or depression. The establishment of a 3-D CAD model ensures a possibility for better aesthetic outcomes of CAM-derived alloplastic implants. Finally, clinical consideration of the CAD algorithms for adjusting contours and their potential application in prospective healthcare are briefly outlined.

Highlights

The following important vital structures are contained in the unchanged volume of solid skull bone: (1) the brain, as the most important and complex organ, (2) blood, which flows through the arteries and veins, and (3) cerebrospinal fluid (CSF) (Monro–Kellie doctrine)
Sci. 2020, 10, 1847 a fixed cranial vault, such injury-triggered brain swelling would unstoppably cause an increase in intracranial pressure (ICP), decreased cerebral blood flow, and attenuated oxygen supply to brain, bringing further deterioration of the brain edema
Injury-driven brain swelling will result in the compromise of intracranial blood flow, and, as a consequence of Monro–Kellie doctrine, cause ischemic and hypoxic changes of brain tissues [6], which promotes further brainstem injuries

Summary

Introduction

The following important vital structures are contained in the unchanged volume of solid skull bone:. (1) the brain, as the most important and complex organ, (2) blood, which flows through the arteries and veins, and (3) cerebrospinal fluid (CSF) (Monro–Kellie doctrine) Under critical circumstances, such as a severe traumatic brain injury and massive stroke (hemorrhagic or ischemic), primary insults to the brain tissues cause disrupted osmolite transport, disturbed transendothelial sodium gradient, enhanced oxidative stress, and augmented inflammatory cascade, thereby triggering devastating impaired permeability of the blood–brain barrier and abnormal accumulation of water within the brain tissue [1,2]. Injury-driven brain swelling will result in the compromise of intracranial blood flow, and, as a consequence of Monro–Kellie doctrine, cause ischemic and hypoxic changes of brain tissues [6], which promotes further brainstem injuries. Reduced risks of complications, such as disrupted CSF dynamics, impaired brain perfusion, and even trephined syndrome, have been presented in reports of a shorter interval time frame for cranioplasty, when compared to a greater than 6-month interval after the initial surgery [18]

Brief Outline of Materials Used for Cranioplasty

Brief Overview of CAM Processing for Reconstruction of Cranial Defects

Clinical Consideration of CAD Algorithms for Adjusting Contours

Findings

12. Conclusions