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.
