Celso Agner

Biomechanical properties of calvarium prosthesis.

Abstract There are many materials available for the reconstruction of calvarial defects. Even though their biomaterial properties are well known, the biomechanical properties as part of the calvarium have not been investigated. In this article, calvarial implants are reviewed with their historic development into modern cranioplasty. Materials for trephined skulls are classified by their category. Individual parameters to describe their mechanical properties are collected and revealed in detail. The laboratory testing methodology for cranioplasty material is introduced to understand each parameter. At last, we discuss an engineering technique to look into the implant behavior. Since there is no standard goal for the biomechanical and biomaterial point of view for cranioplasty, this article suggests the finite element method for evaluation of the implant behavior and the degree of damage upon the impact injury. [Neurol Res 2001; 23: 267-276]

An innovative approach for cranioplasty using hydroxyapatite cement.

T he search for an ideal implant for skull and facial defects began as far back as the 17th century when Fallopius tried to correct a calvarial defect with a gold plate [9]. Today, there are many biomaterials available for reconstruction of such defects; however, most of them have at least one drawback. According to Constantino et al, the ideal implant has eight characteristics: it must (1) be able to resist infection; (2) be strong enough to endure any trauma to the region; (3) be pliable enough to contour to any defect; (4) remain stable over time; (5) elicit minimal inflammatory responses; (6) be radioneutral for visualization on imaging tests; (7) be nonallergenic and noncarcinogenic; and (8) be synthetic. A synthetic implant would eliminate secondary donor site morbidity and rule out the possibility of disease transmission [9]. The most widely used implant materials for facial and skull reconstruction are silicone, polytetrafluoroethylene (PTFE), methylmethacrylate, and biologic materials such as autogenous bone and adipose grafts. Although some of these materials have achieved a degree of success with certain surgical procedures, most of their difficulties concerning biocompatibility arise during application or after implantation. Synthetic materials such as silicone and PTFE have caused moderate to severe inflammatory responses when fibrous tissue has formed around the implant and giant cells were in the vicinity [9]. Silicone is a viscous gel; PTFE is an in-

Stereolithography: Neurosurgical and medical implications

Abstract We present material to define and understand the concept of Stereolithography (STL) and its potential benefits to the field of neurosurgery and other medical specialties. A historical and scientific review of the literature on stereolithography, its evolution and uses in neurosurgery, forensic medicine, and other medical specialties are described. Considerations regarding different techniques used to obtain STL are discussed. The reproduction of cranial and vascular structures using this technique is evaluated. Data acquisition and model fabrication are the two basic steps required for stereolithography to create custom models for multiple applications in cranio-facial surgery, vascular studies, orthopedic surgery, urology and forensic medicine, among others. Stereolithography is a relatively new technique which continues to grow in many medical fields. Pre-operative education of patients, better understanding of patient anatomy, and the creation of custom-made prostheses are proven benefits of this technique.

The neurochemical basis for the applications of the greater omentum in neurosurgery

Abstract The omentum has been utilized in neurosurgery for over 30 years. However, the anatomical and physiological bases for its applications have not been described in great detail. In this paper, we will review the current status of the omentum applications for the management of central nervous system disorders. [Neurol Res 2001; 23: 7-15]

Retrospective analysis of parenteral magnesium sulfate administration in decreased incidence of clinical and neuroradiological cerebral vasospasm: a single center experience

Abstract Objective: Experimental work suggests a neuroprotective role for magnesium sulfate in aneurysmal subarachnoid hemorrhage. We retrospectively review the incidence of clinically relevant vasospasm in patients treated or not with continuous magnesium infusion after onset of subarachnoid hemorrhage. Methods: All patient records in Albany Medical Center with the diagnosis of SAH between January 1999 and June 2004 were reviewed. Patients who presented to the emergency department within 72 hours of onset were entered in the study. Patients were defined as in clinical vasospasm if there was an acute neurological change in association with abnormal trancranial Doppler (TCD), CT angiogram (CTA) or digital subtraction angiography (DSA). Results: A total of 85 patients were selected. Magnesium sulfate was infused in 43 patients. When compared with patients who did not receive MgSO4, there was a statistically significant lower incidence of clinical and radiological vasospasm in those who had the continuous infusion of magnesium sulfate (p<0.01). There was no statistically significant difference between patients who were coiled or clipped. Conclusion: Continuous magnesium sulfate infusion for the management of clinically significant cerebral vasospasm is safe and reduces the incidence of clinically significant cerebral vasospasm. Large, multicenter, controlled studies should be performed in order to determine the true effectiveness of the treatment in a controlled setting.

Historical evolution of neuroendovascular surgery of intracranial aneurysms: from coils to polymers

Abstract Objectives: The backbone of neuroendovascular surgery was developed in the decades of the 1960s, 1970s and 1980s. Catheter, balloon and coil technologies were further added to the armamentarium of endovascular treatment of cerebral arterial aneurysms and vasospasm. Material and methods: Development of detachable coils in the early 1990s was a major breakthrough in the management of intracranial arterial aneurysms. We reviewed available literature and evidence and summarized historical landmarks in the development of neuroendovascular surgery for intracranial arterial aneurysms. Conclusion: Current management of intracranial aneurysms is a merge between derived knowledge of early generational concepts and current technology.

Microsurgical anatomy of the short central artery.

We studied the origin, length, external diameter, disposition, branching patterns and the perforators of short central artery in the circle of Willis in eighty fresh, unfixed cerebral hemispheres (40 brains). We also examined the relationship of the short central artery, the recurrent artery of Heubner, and M1 perforators to the anterior perforated substance, caudate and putamen. The short central artery arises at 5.2 +/- 3.36 mm from the origin of the anterior cerebral artery, hidden and overlapped by the internal carotid artery bifurcation. The recurrent artery of Heubner arises distally to the origin of the short central artery. Four main anatomical variations were found: 1. Presence of short central artery and recurrent artery of Heubner (37.5%). 2. Isolated presence of the short central artery (27.5%). 3. Isolated presence of the recurrent artery of Heubner (21.25%). 4. Absence of short central artery and recurrent artery of Heubner (13.75%). Two different branching patterns were observed: 1. 2-4 straight perforators from the short central artery, perforators from the recurrent artery of Heubner and lenticulostriate from the most medial portion of the M1, in 42 of 80 hemispheres (52.5%). 2. 8-10 perforators from only short central artery in 10 of 80 hemispheres (12.5%) with absent or hypoplastic recurrent artery of Heubner and lenticulostriates from M1 and M2.

Cerebral arterial aneurysms: the early period of neuroendovascular therapy

Abstract Objectives: Anatomical concepts derived by surgical management of intracranial aneurysms provided a pathway to the current integration and practice of aneurysm treatment. These important early developments, such as the surgical microscope in the late 1960s, the development of new surgical techniques and catheters and the evolution of imaging technology, have all provided a fundamental sequence to current clinical practice. Material and methods: The 1960s can be recognized as the dawn of the current era of aneurysm management. It was during this time period that the quest for novel methods of treatment that carried less risk and severity to the patients was being considered with comparable results. Conclusion: The current management of intracranial aneurysms is a merge between derived knowledge of early generational concepts and current technology. A clear and conclusive understanding of these current achievements is, however, still in their infancy.

Attenuation of pain perception after transposition of the greater omentum to the cauda equina region of rats—a preliminary observation

Abstract Background: This paper addresses a specific experimental design to suggest the possible role of the greater omentum in the modulation of pain in rats. Methods: Fifteen male Sprague–Dawley rats weighing between 275 and 325 g were selected. The animals were randomized and then anesthetized with pentobarbital (35 mg/kg) and divided into three groups: (1) sham: laparotomy followed by laminectomy with exposure of the spinal epidural space (n=5); (2) transposition of pedicled omentum (n=5) to the cauda equina epidural space; and (3) transposition of pedicled omentum (n=5) to the cauda equina intradural space. The animals were operated upon and once more randomized by an independent investigator, so that the groups were thought to be similar during post-operative testing. The latency of paw withdrawal to noxious heat stimulation was tested and the values (seconds) plotted for 1, 3, 6, 11, 14 and 30 days after surgery. Randomization codes were open after the animals were euthanized. The analysis of variance (ANOVA) without replication was applied for each of the dataset and comparisons established among the different study groups involved. The omenta were removed and standard immunohistochemistry was performed for gamma-amino-butyric acid (GABA), serotonin, calcitonin-gene related protein (CGRP), vascular intestinal peptide (VIP) and Met-enkephalin. Results: The response to high heating rates of stimulation favored intradural versus sham and epidural omental transpositions. High and low noxious heat stimulation suggested an increased threshold to noxious stimulation after the 3 and 30 days of omental transposition. In the low heat stimulation series, responses were comparatively higher than in the sham animals. Conclusions: The suggested increased threshold of response to noxious stimulation after transposition of the greater omentum onto the spinal cord of rats suggested a novel role of the omentum and a potential future application in the clinical arena.

THE USE OF HIGH POWER DRILLS FOR LAMINECTOMY IN SPINAL STENOSIS : TECHNICAL REPORT

High power drill systems are being used for cervical and lumbar spinal stenosis surgeries. The use and comparative analysis of several systems are presented.