Women in Neurosurgery: Historical Path to Self-Segregation and Proposal for an Integrated Future.

Despite the rising percentage of women accessing the medical profession over the last few decades, surgical specialties are still largely male-dominated; in particular, a remarkable gender disparity is evident in neurosurgery, where only 19% of practitioners are females. Although women may be reluctant to choose a challenging specialty like neurosurgery due to concerns around how to balance family and career, it must be admitted that prejudices against female neurosurgeons have been deeply rooted for long, prompting many to give up and switch track to less demanding subspecialties. Among those who have persisted, many, if not most, have experienced difficulties in career progression and received unequal treatment in comparison with their male counterparts. In 1989, a group of 8 female neurosurgeons founded Women in Neurosurgery (WINS), an organization that aimed to guarantee inclusivity in neurosurgery, encouraging a better and more egalitarian working environment. Thereafter, WINS sessions were regularly promoted at international conferences, offering female neurosurgeons a platform to report issues related to gender discrimination. Over recent years, the mission of WINS sessions in national and international conferences has taken an unexpected deviation; they have progressively become supplementary scientific sessions with only women neurosurgeons as speakers, thus paving the road to a form of self-segregation. This tendency has also resulted in the establishment of sections of only female neurosurgeons within some national societies. Although there remains a faction that fiercely supports the WINS mindset of reserved spaces for women, such segregation is an upsetting prospect for those who believe that science and professionalism have no gender; a growing part of the global neurosurgical community believes that the conception of a "female neurosurgery" and a "male neurosurgery" is misguided and counterproductive and consider the existence of the WINS as anachronistic and no longer necessary.

Stereotactic radiosurgery for metastatic spine tumors.

Spinal metastases invariably affect the majority of patients with cancer. Many will develop symptoms related to pain and disability from epidural spinal cord compression as well as pathologic fracture of the vertebrae. With the emergence of targeted systemic therapies and a better understanding of cancer biology, patients are living longer with bony metastases. This poses particular challenges, as palliation of pain and maintenance of local tumor control are paramount to quality of life and overall functional independence for these patients. Stereotactic radiosurgery (SRS) has emerged as a potent primary standalone and adjuvant treatment option for spinal metastases. To date, the primary indications for SRS include 1) upfront standalone treatment for painful bony metastases in the oligometastatic patient, 2) standalone or post-operative treatment following progression or recurrence of local disease despite previous conventional external beam radiation therapy (cEBRT), and 3) following surgery during which epidural disease is decompressed and the spine stabilized when indicated. SRS has demonstrated a significant advantage over cEBRT for tumors traditionally regarded as relatively radioresistant such as sarcoma, melanoma, renal cell carcinoma, non-small cell lung cancer and colon carcinoma.9 The radiobiological advantage of increased tumoricidal dose delivery and spinal cord dose sparing in SRS have made this a powerful treatment alternative to cEBRT particularly within the context of re-irradiation. Given the limitations of spinal cord dose constraints, surgery is still the first-line therapy in patients with high-grade epidural spinal cord compression (ESCC). Epidural compression can be treated with SRS, however this risks radiation-induced myelopathy and challenges the safety of effective dose delivery at the dural margin.11 With increasing dose, radiation-induced vertebral fracture is the most serious and prevalent side effect of SRS.53 An overview of SRS, including the most common indications, complications, and outcomes for spinal metastases are presented here.

Robotic assisted spinal surgery--from concept to clinical practice.

After several years of product development, animal trials and human cadaver testing, the SpineAssist--a miniature bone-mounted robotic system--has recently entered clinical use. To the best of the authors' knowledge, this is the only available image-based mechanical guidance system that enables pedicle screw insertion with an overall accuracy in the range of 1 mm in both open and minimally invasive procedures. In this paper, we describe the development and clinical trial process that has brought the SpineAssist to its current state, with an emphasis on the various difficulties encountered along the way and the corresponding solutions. All aspects of product development are discussed, including mechanical design, CT-to-fluoroscopy image registration, and surgical techniques. Finally, we describe a series of preclinical trials with human cadavers, as well as clinical use, which verify the system's accuracy and efficacy.

Anterior cervical plating.

Although anterior cervical instrumentation was initially used in cervical trauma, because of obvious benefits, indications for its use have been expanded over time to degenerative cases as well as tumor and infection of the cervical spine. Along with a threefold increase in incidence of cervical fusion surgery, implant designs have evolved over the last three decades. Observation of graft subsidence and phenomenon of stress shielding led to the development of the new generation dynamic anterior cervical plating systems. Anterior cervical plating does not conclusively improve clinical outcome of the patients, but certainly enhances the efficacy of autograft and allograft fusion and lessens the rate of pseudoarthrosis and kyphosis after multilevel discectomy and fusions. A review of biomechanics, surgical technique, indications, complications and results of various anterior cervical plating systems is presented here to enable clinicians to select the appropriate construct design.

Silicon dermabrasion tools for skin resurfacing applications.

Miniature abrasion tools for potential skin resurfacing applications are created using microelectromechanical systems (MEMS) fabrication technology. The abrading microstructures are formed on silicon wafers by a bulk micromachining process based on isotropic xenon difluoride etching. The micromachined abraders (microdermabraders) are packaged and applied to human cadaveric skin to assess abrasion quality. Plastic (acrylic) microreplicated structures, non-coated and aluminum-coated versions, are also used in a similar fashion. Non-textured silicon and plastic samples are used as study controls. Dermabraded and intact skin regions are analyzed qualitatively and quantitatively by light microscopy, image processing techniques, and histology. The microdermabraders exhibit a cleaner, more uniform abrading pattern on the cadaveric skin compared to the plastic microreplicated structures. Furthermore, the microdermabraders provide a consistently uniform cut through the epidermal layer, leaving little debris and minimal pitting. In contrast, the plastic microreplicated structures exhibit non-uniform abrading patterns and leave behind more debris and eccentric pits. The results suggest micromachined dermabraders can successfully abrade fine dermatological flaws in human skin.

Microelectromechanical systems and neurosurgery: a new era in a new millennium.

MICROMACHINES AND MICROELECTROMECHANICAL SYSTEMS (MEMS) are terms that are new to neurosurgeons but certain to become "household terms" in neurosurgery in the near future. These new terms serve as an introduction to a new world of sensors, actuators, and "smart systems" that will change the ways in which neurosurgeons interact with their environment. Through the use of microelectronics and micromachining technologies, MEMS will allow neurosurgeons to perform familiar tasks with greater precision, perform tasks that previously were not done at all, and monitor physiological and biochemical parameters more accurately and with greater safety. This review provides the information necessary to understand the fundamental concepts of MEMS and their application to the neurosurgical arena. It defines the relevant terms and describes the history behind the "micromachine revolution," the capabilities and limitations of MEMS technology, and how this revolution is germane to neurosurgery and to neurosurgeons.

Evaluation of cervical spine in intensive care patients following blunt trauma.

The aim of this study was to review a Level 1 trauma center's use of early (< 72 hours from injury) limited MRI to "clear" cervical spine extradural soft tissue injuries in ICU patients sustaining blunt trauma. A retrospective review of the records of patients meeting entry criteria during 1997 was performed. Demographic data, cervical spine radiographic and imaging evaluation, results, and follow-up information were gathered. One hundred and fifty patients met criteria. Forty-one patients had initial static radiographs that revealed cervical spine trauma. Twenty-seven of the 108 patients with normal initial static radiographs had evidence of extradural soft tissue injury on MRI indicating potential spinal column instability. Twenty-one of the 108 patients had negative MRI and were liberated from cervical spine precautions at a mean of 2.9 +/- 0.9 days from injury. The remaining patients were cleared of cervical spine precautions by plain radiographs and reliable clinical examinations, or by dynamic radiographs, or they died before complete evaluation. The diagnosis of acute injury to the cervical spine from blunt trauma in ICU patients must include evaluation of the osseous spine and extradural soft tissues. Dynamic studies such as flexion and extension views place the obtunded ICU patient at risk of potential neurologic injury. MRI is a noninvasive imaging technique that allows evaluation of extradural soft tissue injury with potentially less patient risk and with fewer personnel. MRI allows early liberation of cervical spine precautions in those patients with negative studies. Further studies are needed to compare specific ligamentous injury patterns by MRI with dynamic studies of the C-spine to further define MRI injury patterns indicating risk of acute spinal instability.

Spinal stabilization by using crossed-screw anterior-posterior fixation after multisegmental total spondylectomy for thoracic chondrosarcoma. Case report.

The authors describe the case of a 41-year-old man with high-grade chondrosarcoma who presented with a paraspinous mass extending into three thoracic vertebrae (T10-12). Crossfixed long anterior and posterior instrumentation was placed after three complete spondylectomies (T10-12). This technique augments spinal stability with an outrigger effect by using crossfixators placed between paired dorsal rods, as well as between the anterior and posterior hardware components. This technique may be used as an alternative when multiple vertebrae or all three spinal columns are involved by radioresistant malignant tumors in patients in whom there is a relatively long life expectancy.

History of thoracolumbar decompression and stabilization.

This article organizes the history of thoracolumbar spine surgery around its two major purposes: spinal decompression and spinal stabilization. Only select turning points of this history are addressed. Emphasis is given to important surgical obstacles and perioperative and anesthetic problems, as they have influenced the development of thoracolumbar spine surgery.

Effects of cervical spine posture on axial load bearing ability: a biomechanical study.

OBJECT: The authors conducted a study to assess the effects of cervical posture on the loadbearing ability of the cervical spine. METHODS: Twelve cervical spine specimens obtained in 12 adult sheep were tested. The specimens were randomly separated into two groups. In Group I the specimens were fixed in a lordotic posture, and in Group II they were fixed in a straight posture. Axial compressive loads were applied at a constant rate of 5 cm/minute. Load-to-failure, time-to-failure, piston displacement at failure, and failure modes were recorded. Statistical analyses were performed to detect differences between the groups. There was no significant difference in load-to-failure values between the two groups. However, the time-to-failure and the piston displacement values for the straight spines were significantly less than those for the lordotic spines. Additionally, the straight spines failed predominantly through ventral elements, whereas the lordotic spines predominantly failed dorsally. CONCLUSIONS: It is concluded that a loss of a lordosis increases the risk of injury to the cervical spine following axial loading.

Effects of hole preparation on screw pullout resistance and insertional torque: a biomechanical study.

OBJECT: The authors conducted a study to assess the effect of a pilot hole preparation on screw pullout resistance and screw insertional torque. METHODS: Three different screws were tested: cancellous lateral mass screws, cortical lateral mass screws, and pedicle screws. Synthetic bone blocks were used as the host material. Each screw group was separated into two subgroups. The first subgroup of screws was inserted into the test material following pilot hole preparation. Pilot holes were prepared; a drill bit diameter size smaller than the core diameter of the screws was used. The second group of screws was inserted into the test material without pilot hole preparation (a 3- or 4-mm hole drilled for entrance site preparation only). The insertional torque was measured as the screw was advanced into the material. The screws were axially extracted from the host material at a constant speed of 2.5 mm/minute. The pullout resistances and insertional torques for the pilot hole and the nonpilot hole groups were then statistically compared. The authors found that preparation of a pilot hole caused a significant decrease in the insertional torque. The screws inserted without a pilot hole showed greater pullout resistances compared with those inserted following a pilot hole preparation; however, there was no statistically significant difference. CONCLUSIONS: The optimum screw insertion technique may involve drilling a short pilot hole and using a drill bit with a smaller diameter than the screw core diameter to increase bone-screw purchase. This applies to cancellous and cortical lateral mass screws as well as pedicle screws.

Management of metastatic tumors of the spine: strategies and operative indications.

The spinal column is the most frequent site of bone metastasis in the body. Spine surgeons are often involved in the care of these patients only after nonoperative management has failed. Because surgery has been viewed as no better than radiotherapy in the treatment of metastasis of the spine, it has only been used as a salvage approach. These views are based on a body of literature in which laminectomy combined with radiotherapy was compared with radiotherapy alone. Anterior approaches to the spine are now popular and familiar to most surgeons. These approaches allow direct access to the metastatic lesion, reconstruction of the anterior vertebral column, and the placement of anterior instrumentation. Outcomes are frequently much better when this combined treatment is used instead of radiotherapy alone. In selected patients, surgery may be desired as first-line therapy before radio- or chemotherapy has been initiated. The controversy surrounding surgery for metastatic spinal disease is reviewed. Treatment strategies, both operative and nonoperative, are presented. Indications and strategies for surgery are also presented, and the supporting literature is reviewed.

Biomechanics of thoracic discectomy.

The thoracic spine is a structurally unique region that renders it uniquely susceptible to thoracic disc herniation. Surgical management strategies are complicated, in part, by the regional anatomical and biomechanical nuances. Surgical approaches include posterior, posterolateral, and anterior routes. Each is associated with specific indications and contraindications. The biomechanical principles and safe anatomical trajectories must be considered in the surgical decision-making process. These issues are discussed in the pages that follow.

Biomechanics of bone fusion.

Bone fusion can be achieved by one or more of three methods: in situ, onlay, and interbody fusion. Interbody implants provide the spine with the ability to bear an axial load. They function optimally when placed along the neutral axis and produce little, if any, significant bending moment. Interbody implants may be comprised of bone, non-bone materials such as acrylic, or a combination of both such as in interbody cages. In this report the authors' goal is to provide some insight into the theoretical, as well as practical, biomechanical factors that influence bone fusion, focusing on interbody implants. They review the concept of stress shielding and its impact on fusion. With the attendant biomechanical nuances of the different regions of the spine, they discuss region-specific strategies involved in successful fusion. Finally, they review intraoperative techniques that will improve the chance of achieving a successful arthrodesis.