CHAPTER 264 Overview and Historical Considerations
Spinal disorders have been recognized as a serious affliction of humans since ancient times. Early accounts of spinal disorders reflected the pessimism appropriate for the period, given the serious morbidity involved and the complexity of managing many of these conditions. The Hippocratic record was probably the first to describe active therapeutic intervention in the form of closed reduction of spine injuries.1 True surgical treatments of disorders of the spine were rare before the beginning of the 20th century. The dismal results of surgical attempts discouraged most surgeons,2–4 but a few reports from remarkable pioneers described successful outcomes.5–7
In 1891, the ability to diagnose spinal disorders in vivo was revolutionized by the discovery of x-rays by Wilhelm Conrad Roentgen.8 This new technology was rapidly incorporated into clinical problem solving.9 Concurrently, neurologists and their surgical colleagues were gaining confidence in the concept of localizing lesions in the central nervous system on the basis of physical neurological examination.10,11 Emboldened by improvements in anesthesia and asepsis, the concepts of clinical localization, and the diagnostic power of radiology, 20th century surgeons began to address a broader spectrum of spinal lesions.
In the field of diagnostic imaging that emerged after Roentgen’s discovery, several key developments enhanced the diagnosis of spinal conditions. Dandy’s use of gas instillation for ventriculography and myelography allowed visualization of the spinal cord and nerve roots and delineation of pathologic compression.12 The introduction of iodinated contrast material soon followed and provided improved image quality.13 The replacement of lipid-based media with water-soluble agents continued to refine the technique, further improved the images, and obviated the need to manually remove the contrast material through lumbar puncture. Diskography, which remains controversial, was described by Lindblom in 1948.14 Epidural venography, performed through a transfemoral route, also enjoyed a period of use despite some difficulty in interpretation.15
Axial computed tomography (CT) revolutionized diagnostic imaging of the central nervous system. CT represents the synthesis of work of numerous investigators into a tool for clinical problem solving. Although often credited to Hounsfield,16,17 numerous others played key roles in the theoretical background required for its development.18–20 Further technical refinements for spinal imaging, including combination with myelography, spiral acquisition, sagittal and coronal reformatted images, and three-dimensional reconstruction, continue to enhance its utility.21–23
Similar to the story for CT, the development of magnetic resonance imaging (MRI) was the result of numerous individuals building on the efforts of others. After years of basic investigations, Damadian patented a device in 1972 for body imaging that used the principles of magnetic resonance.24 Countless others have since contributed to the state of spinal imaging available today. MRI is the diagnostic imaging modality of choice for most clinical conditions involving the spine and spinal cord. Although CT remains superior for the evaluation of fine bony detail, the ability to image all tissues related to the spine in multiple planes gives MRI a clear advantage in many situations. The chief disadvantage of this modality is the time involved in performing the study, which may limit its use in trauma or emergency circumstances.
Historically, surgeons operated on the spine from a posterior approach. This was logical because it was the most direct path to the bony elements, but the potential benefits of alternative approaches tailored to the offending pathology were soon realized. Posterolateral approaches first developed in the context of surgical treatment of Pott’s disease. Menard described an approach that he called costotransversectomy in 1984.25 Menard’s primary objective for this approach was drainage of tuberculous paravertebral abscesses. Subsequent major modifications to costotransversectomy were the lateral rachiotomy approach developed by Capener26 and the lateral extracavitary approach of Larson and colleagues.27 Both these modifications achieved an even more lateral view that allowed direct decompression of the neural elements. These classic approaches continue to undergo modification, such as McCormick’s retropleural approach.28
Anterior approaches to the spine were often developed in response to problems presented by tuberculous spondylitis. In 1956, Hodgson and Stock reported their experiences with anterior decompressive operations.29 Cloward30 and Robinson and Smith31 are generally acknowledged as establishing the anterior approach to the cervical spine for the management of disk herniation. The transoral approach was described soon after and was also developed initially for treating tuberculosis.32
Hibbs33 and Albee34 independently described surgical treatments of Pott’s disease, which are usually cited as the initial reports of fusion procedures for the spine. Subsequent surgeons applied similar techniques to other conditions, including fractures, degenerative disease, and spondylolisthesis.35–38 Posterolateral intertransverse fusion techniques were further refined by Ghormley39 and others. Unfortunately, many of the early methods of spinal fusion were flawed by relatively high rates of nonunion. Improved results, particularly in patients with previous instability, had to wait for the development of satisfactory spinal instrumentation. Anterior and posterior lumbar interbody fusion techniques were described by Burns40 and Cloward,41 respectively.
The use of metal implants to correct deformity and provide internal stabilization began in the late 19th century. Reviews often cite Wilkins’ use of a carbonized silver wire suture to stabilize T12-L1 in an infant42 as the first recorded use (1988) of internal fixation of the spine. Hadra described placement of internal wire fixation in the cervical spine in 1891.43 Lange44 and a few other surgeons reported attempts at internal fixation in the early 20th century, but further development of spinal instrumentation systems required advances in the art of spinal fusion, improved understanding of biomechanics, and noncorrosive metallic implants.
Harrington’s distraction rod system was first used in the late 1940s.45–47 Luque’s L-rod with segmental sublaminar wires was developed in the 1970s.48 A posterior, multiple hook-rod system was described by Cotrel and Dubousset in 1982.49 Several other universal implant systems were introduced, including the Texas Scottish Rite Hospital (TSRH) and the Moss Miami spinal systems.50,51
Screws placed into the facets were used by King52 and others to promote fusion. The screw trajectory was later modified to provide fixation into the pedicle.53 Transpedicular screw fixation was refined and clinically used in the 1960s and 1970s by Roy-Camille and colleagues54 and by Louis55 and was further developed and popularized in Europe in the 1980s. Pedicle fixation began to be widely used in North America as an adjunct to fusion in the 1980s and 1990s.56
Devices for anterior fixation of the spine in scoliosis were developed in part because of early problems with Harrington’s distraction rod. Dwyer and coworkers described a device for the anterior correction of scoliotic deformity in 1969.57 Although drawbacks to this form of correction were soon recognized, the Dwyer device stimulated further development of anterior instrumentation systems.58,59
Anterior plating of the cervical spine was a natural adjunct to the expansion of anterior approaches to this region and provided the surgeon with better segmental immobilization than could be achieved with orthotic devices. Oroszco and Llovet60 first applied plates to the anterior cervical spine, followed by Caspar61 and others. During the 1970s and 1980s, implants for posterior cervical fixation with plates with screws inserted into the lateral masses were also undergoing development by several clinical investigators.62,63Chapter 298 and Chapter 299 define the range of current surgical techniques for spinal instrumentation from the occiput to the thoracic spine. These techniques have permitted progression from segmental immobilization in situ to active correction of most cervical deformities. Advances in instrumentation with active correction of deformity have reduced the need to perform procedures such as transoral odontoid resection for basilar impaction caused by rheumatoid arthritis.
The continued dramatic expansion in the use of internal fixation for the gamut of spinal disorders is further testament to its utility. Today’s spine surgeons are continually challenged to adapt their techniques to newer instruments and techniques. Building on previous developments in spinal instrumentation and improvements in intraoperative imaging, many traditional spine surgery procedures can now be performed with minimally invasive techniques to decrease muscle injury and potentially reduce complications and improve outcomes. Chapter 307 details the progressive advances in surgical technique over the past decade and discusses future trends in treating a greater spectrum of clinical pathology with minimally invasive techniques for lumbar disorders.
Basic Science
Spinal cord injury is among the most devastating of injuries because it robs the individual of neurological function and offers limited prospect for recovery. Advances in basic neurobiology and neurophysiology have altered the historical view that the spinal cord has no potential for neural plasticity. Chapter 267 and Chapter 268 discuss the spectrum of theoretical and practical pharmacologic and physiologic treatments undergoing laboratory and clinical evaluation and how these treatments are having an impact on current management of spinal cord injury. The recent literature cited in these chapters provides current information on the benefits and risks of early and delayed surgical intervention for spinal column injury with associated neurological deficits.
Chapters 265 and Chapter 266 provide an extensive overview of spinal biomechanics for all current forms of spinal instrumentation, including arthroplasty. Concepts such as load sharing, cantilever bending, and forces leading to implant failure are discussed. The current understanding of the effect of various biomaterials on implant durability and wear and their role in lumbar and cervical arthroplasaty is also detailed.
As the surgical techniques for managing spinal disorders have become more powerful and greater forces are used for spinal realignment, the concept of intraoperatively monitoring the physiologic status of the neural elements during operative manipulation has become more important. Procedures that decompress the spinal cord or cauda equina, reduce fractures or subluxations, or correct deformity all have the potential to alter neurological function through direct or indirect injury to the neural elements. The goal of continuously assessing the status of the cord and nerve roots in nearly real time is now feasible. Chapter 269 describes the role of intraoperative physiologic monitoring as applied to spine surgery and discusses the reliability and validity of such measurements.
A surgeon who routinely performs spinal instrumentation, treats fractures, or manages spinal disorders in the elderly must understand normal bone metabolism, its hormonal regulation, and the impact of aging on bone density. An appreciation of the effects of various physical and pharmacologic agents on bone deposition and resorption is imperative, as is an understanding of altered states of bone metabolism such as osteoporosis, Paget’s disease, and osteomalacia. Chapters 271 and Chapter 321 describe normal and pathologic bone metabolism, the challenges of patients with reduced bone mineral density, and treatment strategies to best manage these challenging cases, including the use of vertebroplasty and kyphoplasty.
A host of disorders occur as a result of derangements in the normal embryonic development of the spine. Chapters 289 and Chapter 290 discuss the evaluation and management of congenital and developmental abnormalities of the craniocervical junction and thoracolumbar spine. Although many of these conditions are present from infancy, they frequently become evident only after skeletal maturity. These chapters discuss the latest surgical techniques for reducing complications and improving outcomes in these often demanding cases.
Approach to the Patient
Low back pain is a problem that constantly confronts the spine surgeon with diagnostic and therapeutic dilemmas. Chapter 270 describes the physiologic concepts of disk degeneration and current laboratory techniques under development to either slow degeneration or promote disk regeneration. Managment of chronic lower back pain is a substantial burden to the surgeon and society. The treating physician must maintain an organized, methodical but individualized approach. Most patients referred to a spine surgeon with complaints of low back pain are best treated by medical management, and it is therefore essential to remain abreast of current medical treatments. Patients who have failed previous operative interventions represent a particularly difficult group for whom surgery must be considered only with extreme caution and attention to strict operative indications. Chapters 272, Chapter 273 and Chapter 274 provide useful insight into the evaluation and management of spine patients in general and those with intractable spine-related pain in particular. Surgeons must remain aware of a variety of other nondegenerative causes of low back pain and other medical conditions that may initially be manifested as pain in the spinal area. Multiple studies have detailed generally poorer outcomes with revision spine surgery than with primary surgery. Chapter 275 discusses evaluation, appropriate patient selection, and differences in technique for patients who have failed a primary surgical intervention.
Infections
Spontaneous spine infections are becoming increasingly common in clinical practice as a result of the prevalence of intravenous drug abuse and the greater incidence of patients in the population with immunoincompetence, diabetes, and other predisposing conditions. Improved diagnostic accuracy with MRI has allowed earlier and often less extensive treatment in many cases. Nonetheless, surgical débridement and reconstruction are often indicated. Multimodality management is typically optimal; it combines antimicrobial therapy with decompression of the neural elements, removal of necrotic tissue, and spinal stabilization, followed by physical rehabilitation. Chapter 276 and Chapter 277 address these issues with respect to a spectrum of pyogenic, fungal, and tubercular causes.
Degenerative Disease
Several chapters in this section describe issues related to degenerative conditions of the cervical spine. Spondylosis and disk degeneration of the cervical spine can be manifested as radiculopathy, myelopathy, or both simultaneously. Therapeutic decisions must be individualized and take into account the patient’s wishes, the natural history of the process, the specific pathoanatomy, and the newer techniques available. Chapter 279 and Chapter 280 review these topics and describe the evaluation and general surgical options. Chapter 293 describes in detail the indications, contraindications, results, and operative technique for cervical arthroplasty.
Ankylosing spondylitis and other spondyloarthropathies pose unique problems for the surgeon, as does ossification of the posterior longitudinal ligament. The special issues related to these disorders are reviewed in Chapter 281 and Chapter 282.
Despite the increased frequency with which thoracic disk herniations are visualized on MRI, the frequency of symptomatic lesions remains low. Nonetheless, these herniations can be associated with considerable neurological morbidity. An expanding surgical armamentarium of open and thoracoscopic approaches is available to manage thoracic disk herniation. Chapter 283 and Chapter 306 describe the range of surgical procedures currently used for the management of these conditions and discuss the need to individualize the approach based on factors such as thoracic disk location, calcification, and size. Chapter 306 also discusses the increasing range of thoracic pathology that can be successfully managed with thoracoscopic approaches with potentially less morbidity than seen with traditional thoracotomy.
Degenerative conditions of the lumbar spine consist primarily of disk herniations, spondylosis and stenosis, spondylolisthesis of multiple origins, and deformity. Chapter 284, Chapter 285 and Chapter 287 review the clinical and physical findings, evaluation, and therapeutic options for these common conditions. More recently, the introduction of newer techniques such as lumbar arthplasty, nucleoplasty, dynamic stabilization, and other motion-sparing techniques has gained increased interest. Chapter 288 and Chapter 289 provide a history of the development of these devices, detail the results of recently completed and ongoing clinical trials, and discuss the current indications for the use of these devices.
The topic of evaluation and management of adult thoracolumbar deformity is not typically included in most neurosurgical texts. With the trend toward subspecialization in spine surgery, however, both neurosurgical and orthopedic spine surgeons are increasingly being exposed to progressively more complex cases. Aging of the population and the consequences of previous surgical interventions have increased the overall incidence of adult spinal deformity. Most neurosurgeons treating degenerative spinal conditions will encounter patients with spinal deformity. Chapter 287 discusses the clinical findings, diagnosis, and management of adult thoracolumbar scoliosis. Chapter 288 details the evaluation and management of sagittal spinal deformites, including iatrogenic flat back, which has been increasing recognized as a major cause of failure in management of deformity. Chapter 290 discusses the indications and fixation techniques for spinopelvic instrumentation.
Conditions Affecting the Craniocervical Junction
The craniocervical junction remains a challenging area for surgeons. Congenital abnormalities, tumors, and traumatic injuries each present problems in diagnosis and surgical management. Operative approaches to this area include anterior, lateral, anterolateral, posterolateral, and posterior procedures. Chapter 289, Chapter 298, Chapter 308, Chapter 313 and Chapter 314 detail the range of pathologic conditions and nicely illustrate these different options. Advances in instrumentation have expanded the options for occipitocervical stabilization.
Techniques and Instrumentation
Despite the continued evolution of spinal implant systems, basic principles apply to their application. It is axiomatic that an instrumentation construct is only a means to successful spinal fusion. In Chapter 291, an overview of the techniques of instrumention of the spine and the fundamental principles that must be considered for successful surgery are provided. The nuances and technical aspects of autologous bone harvest and its use in spinal fusion are provided in Chapter 292. This chapter also discusses the range of bone graft extenders and substitutes, including the use of bone morphogenetic protein.
The revolution in imaging technology coupled with advances in frameless stereotaxy has resulted in the development of methods for intraoperative navigation in relation to the spine. In Chapter 305, Kalfas provides an overview of this rapidly evolving surgical tool and its use for the placement of pedicle fixation, tumor resection, and other applications.
Intradiskal and percutaneous treatment of disk herniation and radiculopathy has sparked the imagination of surgeons and patients for decades. The potential use of intradiskal proteolytic enzymes, called chemonucleolysis, was suggested by Hirsch65 in 1959 and first performed by Smith66 in 1963. Physical removal of nuclear material through a percutaneous approach was reported as early as 1975.67 Continued interest in a less invasive treatment of symptomatic lumbar disk herniation and other degenerative processes has fueled ongoing investigation. The progress in this field and the current status of many of these modalities are reviewed by Fessler and associates in Chapter 307.
Tumors of the Spine
Tumors affecting the spinal cord have been treated by neurosurgeons for decades, but more sophisticated techniques have recently been developed. These techniques, along with a number of postoperative pearls, are nicely described by McCormick and colleagues in Chapter 309. The management of benign and malignant vertebral tumors continues to evolve. Primary tumors of bone are much more effectively treated today as surgeons have become more adept at recognizing these lesions and applying an expanding array of approaches and reconstruction techniques. As oncologists continue to extend the life expectancy of patients with malignant disease, the frequency with which spinal metastases are encountered can also be anticipated to increase. MRI has dramatically facilitated the diagnosis of these lesions and greatly enhances surgical planning. Because metastases so commonly involve the vertebral body, greater familiarity with anterior and anterolateral techniques significantly improves the quality of canal decompression routinely achieved. Options for spinal reconstruction have also been expanded by advances in surgical technique and implant design. Significant surgical obstacles remain to be overcome, however. The use of more aggressive surgical resection and reconstruction techniques, the role of stereotactic radiosurgery, and the use of multimodality treatments are detailed in Chapter 310 and Chapter 311. Widespread multilevel disease, sacral lesions, and involvement of the cervicothoracic region tax our ability to provide adequate palliation.
Trauma
The highly mobile cervical spine is the region most vulnerable to traumatic injury and represents the most common site of spinal cord injury. In Chapter 312, Jenkins and colleagues provide an overview of the diagnosis and management of injuries in this region. The odontoid, hangman’s, and subaxial cervical injuries discussed in Chapter 315 and Chapter 316 are among the most common spine injuries seen in neurosurgical practice. The unique anatomic arrangement of the atlantoaxial complex produces distinct patterns of injury that require equally unique management. Chapter 313 and Chapter 314 discuss the spectrum of bony and ligamentous injuries that can be encountered in this location. Chapter 317 focuses on the evaluation, criteria for return to play, and factors precluding athletic participation after transient quadriparesis and athletic injuries to the cervical spine.
Injuries to the thoracic spine are usually the result of extreme physical force. As a result, the incidence of neurological involvement is high. Surgical approaches include standard posterior approaches, posterolateral trajectories, and anterior transthoracic approaches. The techniques and indications for each are presented in Chapter 318.
Fractures of the thoracolumbar junction are second in frequency only to those of the cervical spine because the junction represents a transitional zone between the rigid thoracic spine and the relatively mobile lumbar region. Compression fractures are common, especially with minor trauma and coexisting osteopenia. Burst fractures are the most frequent pattern necessitating treatment. A variety of approaches are available to treat fractures of the thoracolumbar and lumbar region, including standard posterior operations, the lateral extracavitary approach popularized by Larson and coworkers,27 and anterolateral retroperitoneal approaches that facilitate clearance of the anterior canal and reconstruction of the anterior column. A thorough overview of the evaluation and management of thoracolumbar trauma, including advances in classification and surgical technique, is included in Chapter 319.
Traumatic injuries to the sacrum are usually managed nonsurgically with success. In Chapter 320, Perin and colleagues describe the indications for surgical and nonsurgical treatment.
Challenges
Challenges for the future include greater understanding of the degenerative process as it affects the spine. Biologic, nonsurgical solutions to degeneration of the disk, ligaments, and articular cartilage may allow reversal of some changes. Less invasive means of accessing the spine and dealing with the affected segments will surely continue to progress. Spinal fusion, which clearly reflects a tradeoff of greater stability for loss of joint function, will be perfected, perhaps through the use of agents such as bone morphogenetic protein or other osteoinductive agents or drugs. Many recent advances in spinal instrumentation and technique are discussed in Chapter 304, including transforaminal, posterior, and anterior lumbar interbody fusion procedures. The impact of these different procedures used for the management of degenerative lumbar conditions is detailed with respect to spinal alignment, fusion rates, and complication rates.
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