Cervical Spondylosis and Similar Disorders

The following sections are included:

• Preface

• Introductory Remarks

• Contents

The overall frequency of troublesome neck pain is estimated to be about 34%, and it was observed that the frequency of complaints lasting one month or longer was higher in women than in men. The prevalence increased with age with regards to pain duration as well as for chronic pain. A total of approximately 14% of a randomly selected population reported neck complaints lasting for more than six months, thus meeting criteria for having chronic neck pain. Epidemiologic data substantiate the importance of morphologic, age-related changes of the cervical spine.

It could be that the structural transformation of the intervertebral disc, the uncovertebral processes as well as the zygapophyseal joints, is a process accompanied by disturbed function, ultimately inducing pain.

The anatomical structure of the cervical spine is presented in the following chapter in relation to disorders of the cervical spine. The uncus, Luschka's joint, spinal canal, and upper joint articulations are identified in particular, as they relate to spinal disorders. The intervertebral disc and the ligamentous structures are also assessed. The structure of the neural tissues are presented, and the various conditions that compress these structures are explained. Among these are disc herniation, osteophytes, ossification of the posterior longitudinal ligament, and the ligamentum flavum. A narrow spinal canal also plays an important role in the development of cervical spine disorders. The vertebral artery may also cave into the vertebral body. The radicular artery would be compressed prior to nerve root compression. To hold the head in its proper position, a continuous and delicate contraction-relaxation balance of the cervical muscles is essential.

The cervical spine supports the head, protects the spinal cord and nerve roots, and also allows for movement of the neck. Firm support and rapid movements seem to be contradicting demands but the structures of the cervical spine ingeniously meet them.

The intervertebral disc is organized with a concentrated proteoglycan solution, the central nucleus pulposus, held within the strong collagen network of the outer annulus fibrosus. The disc exhibits a viscoelastic response when subjected to loads and deformations. Disc degeneration, and/or spondylotic changes that are generally considered to be associated with aging, result in a spinal segment with decreased stiffness. However, in the cervical spine of cerebral palsy patients suffering from athetotic movements of the neck, there is a very early onset of disc degeneration and spondylotic change. Acceleration of disc degeneration has been shown to take place in the spines of animals subjected to excessive extension-flexion of the head and neck. Repetitive torsion of the disc has led to structural regression in in vitro studies using animal spines. Delaminated lamellae and/or disruption of the annulus fibrosus are always recognized in the early stages of the destructive process of the intervertebral disc structure. Disruption of the collagen network may be a result of fatigue failure by repetitive loading, which in turn causes the high tensile stresses in the annulus fibrosus from the development of large hydrostatic pressures within the nucleus pulposus. Loosening of the collagen network may be a key factor leading to the loss of proteoglycans and water, finally inducing the development of disc degeneration. A “degenerated disc” can be induced through pure mechanical fatigue failure of the tissue, as an age-independent degradation of the cartilaginous tissue.

A reproducible experimental model of cervical spondylosis in rodents was established by means of detachment of the back paravertebral muscles from the vertebrae and resection of the spinous processes together with supraspinous and interspinous ligaments. Spinal instability elicited by this surgical intervention accelerated the process of intervertebral disc degeneration. It induced cervical spondylosis in mice when extended over a 6 — 12 month period. The pathologic changes in the cervical intervertebral discs of this animal model were progressive: proliferation of cartilaginous tissue and fissures in the annulus fibrosus; shrinkage or disappearance of the nucleus pulposus; and herniation of disc materials and osteophyte formation.

Basic fibroblast growth factor (bFGF) was reported to stimulate proliferation and matrix synthesis of cultured intervertebral disc cells. Using this animal model, the distributions of cells expressing bFGF and FGF receptor (FGF-R) were investigated in normal and degenerating intervertebral discs by immunohistochemistry and in situ hybridization histochemistry. Expression of bFGF protein and FGF-R messenger RNA were found in actively proliferating chondrocytes in the degenerating annulus fibrosus, whereas these were negative in normal annulus fibrosus. This suggested that bFGF might regulate the process of disc degeneration.

The availability of this experimental model should be valuable for further understanding, both biochemically and biomechanically, of the pathogenesis of cervical spondylosis.

The etiology of most of the degenerative changes in the spine continues to remain obscure. However, several lines of evidence suggest that genetic factors may play an important role in the onset of degenerative changes, in addition to various environmental factors. We have generated transgenic mice expressing mutant αl(IX) collagen in the cartilage matrix. They developed progressive intervertebral disc degeneration with age as well as joint degeneration. Both radiologic and histologic studies indicated that cervical and lumbar disc degeneration was more advanced in the transgenic mice than in control littermates. The initial degenerative changes included shrinkage and replacement of the nucleus pulposus with consolidated fibrous tissue, that resulted in a loss of nuclear-anular demarcation. Partial disruption in the lamellar structure of the anulus fibrosus also occurred at this stage. With age, the disc degeneration progressively advanced and sometimes caused herniation of disc material and mild osteophyte formation. These findings imply that genetic abnormalities of cartilage matrix components, such as type IX collagen, may be responsible for certain degenerative diseases in the spine.

The important factors causing compression myelopathy include cervical spondylosis, ossification of the posterior longitudinal ligament, and metastatic space occupying lesions in the spinal canal, as well as other lesions such as narrowness of the cervical canal and compression masses (protruded discs and/ or osteophytes, etc.). In addition to these factors, particularly in cases with cervical spondylotic myelopathy (CSM), static and dynamic shortening of the cervical canal due to disc degeneration, and flexion-extension motion of the neck, also affect the cord pathology. An absolute reduction of the transverse area of the compressed cord and the extent of the cord histopathology both closely relate to the severity of the disease and to the recovery potential from the associated clinical symptoms after surgical decompression. An exception of this is for cases of compression myelopathy caused by malignant tumors.

Discussions about the pathophysiology of chronic compressive myelopathy are shrouded by controversy, and a number of questions about our understanding of myelopathy remain unanswered. No previous animal model has adequately reproduced the condition of humans with myelopathy, and the two primary hypotheses concerning the cause (vascular and mechanical) do not fully explain the clinical aspects of cervical spondylotic myelopathy.

To simulate the course of cervical spondylotic myelopathy in humans, we developed a canine model of cervical cord compression that produced a delayed onset of neurologic abnormalities. The cervical spines of 14 dogs were compressed both anteriorly and posteriorly. Four additional dogs underwent sham operations and served as controls. Twelve of the dogs undergoing compression eventually developed clinical signs of myelopathy; the mean latent period to the onset was seven months. These 12 animals were divided into two groups matched according to the degree of neurologic deficit. The spinal cords of six of these animals were then decompressed through removal of the anteriorly-placed device, and these dogs showed subsequent neurologic-improvement. No spontaneous improvement in neurologic function was seen in the dogs whose spinal cords remained compressed. After the animals were sacrificed, histopathologic abnormalities were seen almost exclusively within the gray matter, and included necrosis, cavitation, changes in vascular morphology, and the loss of large motor neurons. The severity of the morphologic changes correlated with the neurologic deficits. Magnetic resonance images, somatosensory evoked potentials, local blood flow measurements and microangiographic data were collected throughout the study.

In comparison to previous models, this animal model of chronic compressive cervical myelopathy more accurately reflects the disease process seen in humans, and provides a basis for a more precise theory of the pathophysiology of CSM.

In patients suffering from disease of the cervical spine, most likely the upper three motion segments, there is, based on anatomical and neurophysiological experiments the possibility to experience head pain. There exists a multitude of clinical symptoms, similar to migraine headache, but distinctive enough to be its own clinical entity. The treatment strategies, either conservative or surgical, have to be focused on the pathological changes of the structures involved.

Cervical angina, resembling angina pectoris and mimicking coronary heart disease, is a well-defined clinical entity also known as pseudo angina. Pseudo angina, which occurs in different visceral manifestations (gall bladder, stomach, esophagus), may also be caused by various musculoskeletal diseases, such as osteoarthritis of the cervical spine, cervical discopathy, osteoarthritis of the dorsal spine, thoracic outlet syndrome, first rib syndrome, or the costovertebral syndrome. In the treatment of cervical angina, conservative measures such as immobilization in a soft collar, physical therapy or manipulation should be performed first.

Symptoms which arise in cervical spondylosis can be categorized as being either core symptoms, marginal symptoms and/or inexplicable symptoms. Core symptoms can be defined as the most common and characteristic signs and symptoms specific to cervical spondylosis, and may be further classified into axial symptoms, radicular symptoms and spinal cord symptoms, according to the origin of the complaints. Characteristic signs and sensitive tests are presented respectively. The tension and relaxation sign in radiculopathy and spastic or amyotrophic myelopathic hands are examples of spinal cord symptoms and are extremely useful for the diagnosis of cervical spondylosis and its associated disorders.

Marginal symptoms are not specific to cervical spondylosis, but they are related. Treatment of cervical spondylosis may eradicate marginal symptoms, such as precordial pain (pseudoangina) or a certain type of headache and vertigo. Therefore, knowledge of marginal symptoms is worthwhile in dealing with patients with cervical spondylosis. Bilateral arm paralysis is very rare, yet it is associated with cervical spondylosis. The disorder is distinct from degenerative spinal cord disease but its pathomechanism has yet to be fully understood. We propose to categorize the disorder tentatively as an “inexplicable symptom,” aiming at further investigation

Correct anatomic diagnosis is the goal of radiographic studies. Appropriate radiographic evaluation of the cervical spine is a key component, along with a thorough patient history and physical examination, in determining the specific treatment options and plans for each individual. Cost considerations demand that radiographic imaging be used prudently. Surgical planning requires that these examinations reliably demonstrate or exclude the clinically suspected pathology. This chapter briefly describes plain radiography, and more thoroughly examines CT, myelography, MRI, and the relationship between these modalities. Nuclear medicine, angiography, and biopsy techniques are less commonly used in daily clinical practice, and will not be discussed in this chapter.

Cervical spondylotic myeloradiculopathy is a very common disorder which is sometimes misdiagnosed as other neuromuscular disorders, particularly if it coexists with cervical spondylosis. Skilled neurological examination is necessary for correct diagnosis. If a patient with atypical myeloradiculopathic signs or symptoms possesses cervical spondylotic changes on roentgenogram, one should always consider another occult neurological disease, and work up the patient with appropriate electrodiagnostic methods.

Care must be exercised in interpreting the clinical and radiological findings when assessing patients with cervical spondylosis and involvement of neural structures, especially if surgery is discussed as a possible therapeutical procedure. If the clinical picture cannot be logically explained by the radiological findings, further investigation is indicated in order to exclude a systemic disease. Investigations may include electrophysiological tests, transcranial magnetic stimulation, CSF analysis and MRI.

A common logical diagnostic methodology is necessary in the identification of painful and/or paretic conditions of the cervical spine. A further requisite in making a correct diagnosis is obtaining valuable information through a thorough medical history. Finally, physicians must use this information in a logical manner to produce a well thought out differential diagnosis. Degeneration of the spine is not apparent until pain or paresis manifests itself in the trunk or extremities. Hence verbal (communication) and visual observation of a patient's distress or postural and behavioral abnormalities is imperative in making a correct diagnosis. A set of characteristic conditions, or the typical signs and symptoms characteristic for a specific disease, are commonly present in patients with cervical spine disorders.

Signs and symptoms can often indicate a particular disorder, and may even lead to a localization of the site of the lesion. None, however, is highly specific for a certain disease of the spine, and only by using a combination of characteristic signs and symptoms together with diagnostic images may one compensate for such a lack of specificity. Busy surgeons often prefer short cut diagnosis using a set of signs and symptoms, and often may not satisfy patients' needs because the whole picture of disease was overlooked. Using a well thought out differential diagnosis, the spine can be more carefully manipulated, and with the judicious use of diagnostic imaging, a correct diagnosis is more likely than if a surgeon overlooks many of the possibilities in both disease type and localization of the disease. Well-trained surgeons do not separate disease diagnosis from the localization of the lesion in the diagnosis of spine disorders. Along with such a practice, the current development of imaging technology affords enough information about “symptom producing lesions.” A problem-oriented search, together with careful observation, relevant examinations and purposeful integration of data, enables surgeons to formulate potential diagnoses with certainty, and allows them to choose the final solution for pain or paresis in a particular case.

Based upon the original pathology, a therapeutical concept should be designed according to the age of the patient. The therapeutical modality has to be adapted to the age and physical condition of the patient.

Children and young adults most commonly suffer from acute functional disorders of the cervical spine which might be treated very efficiently by the modalities of manual therapy. Ergonomics and neck school should be applied early.

In adults who do not present marked degenerative changes, mobilizing techniques for acute disorders can be chosen, but the patients should be instructed for appropriate ergonomics as well as for home exercises combined with trainings therapy.

The aging population normally presents with degenerative changes of the cervical spine, both at the disc endplates as well as in the zygapophyseal joints, thus mobilizing techniques might be rather counterproductive, while stabilization should be the main goal of therapeutical procedures. The patient should be instructed how to reduce rotatory motions of the cervical spine in daily activities in order not to evoke pain during motion, and therefore also stimulate the self-healing process.

In severe neck pain, where the indication for surgery is not justified, stabilizing aids with soft and hard collars are definitely useful, especially in conditions related to atlanto-axial osteoarthritis.

Traction with a cervical halter is efficacious for the neck-shoulder-arm pain due to cervical spondylosis unless strict indication, correct and uninterrupted application are ignored. Intractable pain due to cervical disc hernia should be treated by skull traction with epidural steroid injection on in-patient basis.

For selection of the patients suitable for traction, the nature of the neck-shoulder-arm pain, head compression signs and tension signs such as Mizuno's test are useful guides. Objective neurological deficits, such as muscle weakness, numbness, or loss of tendon reflexes are indicative of the level of radiculopathy, but do not predict the outcome of traction therapy. Cervical spondylotic myelopathy with developmental spinal canal stenosis is not favored by traction.

The following chapter describes the chronological development of the surgical approach to cervical spondylotic myelopathy. It traces the early understanding of cervical spine biomechanics and physiology, and demonstrates how this knowledge influenced the surgical treatment of cervical myelopathy. Of particular importance is the impact of the anterior cervical discectomy and interbody fusion, as described by Smith and Robinson, and its gradual acceptance by the orthopedic and neurosurgical communities. Differences of opinion still persist in the current literature regarding the choice of optimal surgical decompression for complex (i.e. OPLL with dural adhesions, multi-level compressive myelopathy) cervical myelopathies. It is hoped, however, that as our understanding of this degenerative disease process continues to expand, we will be able to apply a unified approach to the diagnosis and ultimate treatment of cervical spondylotic myelopathy.

The anterior surgical approach to cervical spondylosis, including cervical spondylotic radiculopathy and myelopathy, can produce satisfying results. An understanding of the pathophysiology of spondylosis is necessary to appreciate the role of the anterior approach. Surgical indications and techniques including the Smith-Robinson approach, Modified Cloward technique, and partial corpectomy, will be discussed and related to the development of spondylosis.

Radicular pain is a common feature in daily clinical life. Only a small percentage of patients with persisting pain and/or neurological deficit need surgical decompression. An exact anatomical localization of a decompressive agent that is correlated to the specific clinical symptoms and radiological findings is mandatory. Surgery to treat radicular pain is mainly performed by an anterior approach and removal of the causing agent. In cases with narrowing of the neuroforamen, a total uncectomy is indicated. Additional fusion provides support for physiologic cervical lordosis.

Deltoid muscle paresis develops secondary to C5 radiculopathy or myelopathy in cervical spondylosis or cervical disc hernia. Conservative treatment, such as skull traction and epidural steroid injection is usually the treatment of choice when C5 nerve root proved to be impinged by spondylotic or disc protrusion. Surgical treatment is indicated when conservative treatment failed to improve paresis. Anterior excision and fusion for a single segment lesion or subtotal spondylectomy and fusion for adjacent double lesions have been employed as our standard procedure.

When deltoid muscle paresis due to myelopathy was accompanied with multisegmental spondylosis and developmental canal stenosis, conservative treatment was generally ineffective. Expansive laminoplasty and foraminotomy was usually indicated for both compression myelopathy and potentially coexisting radiculopathy as a rule. Satisfactory results were obtained in 87% of the anterior surgery group and in 78% of the laminoplasty group respectively.

Deltoid muscle paresis in elderly persons was occasionally accompanied with multisegmental spondylosis, canal stenosis and kyphotic or lordotic malalignment. This proved hard to treat whatever sort of therapy was employed. Patients suffering from cervical spondylosis often seek treatment for their inability to raise the arm at the shoulder joint. As detailed in Chapter 6, a typical form of such a manifestation can be diagnosed as C5 radiculopathy, or if it is accompanied by spinal cord symptoms (myelopathy), it can be classified into symptom #3: spastic tetraparesis, mild or moderate, with deltoid muscle paresis.

Laminectomy was the original technique used to treat cervical spondylosis. Results were varied, with patients improving in many instances, while in others various problems were encountered. The numerous series of patients that underwent this procedure were difficult to compare because of wide variations in the operative procedures and patient selection that was used. Frequently, conditions other than spondylosis were included, further confusing an evaluation of the results.

The devlopment of relatively simple techniques for an anterior approach to the cervical spine reduced interest in laminectomy as a treatment for spondylosis. Clinical results were encouraging since the main pathology is usually ventral to the spinal cord, and can be attacked directly. As more vertebral segments were treated and longer patient follow-up became available, the limitations of anterior surgery have become clearer, along with its advantages and indications.

A re-evaluation of laminectomy occurred, prompted by several factors. Biomechanical studies have increased our understanding of individual elements allowing the surgeon to better evaluate the result expected from anatomical and biomechanical changes due to a surgical procedure. A better knowledge of the signs and symptoms of spondylosis have improved patient selection with the aid of MRI and CT scanning, which highlight the pathology.

This improved knowledge stimulated a re-evaluation of laminectomy and the realization that it is an important treatment for spondylosis. It is especially valuable when long segments of spine are degenerated and the objective is adequate treatment while preserving neck motion.

This chapter attempts to define the indications and techniques in order to achieve good results from laminectomy as a treatment for cervical spondylosis.

The following sections are included:

• INTRODUCTION

• AIMS, ADVANTAGES AND DISADVANTAGES OF LAMINOPLASTY

• INDICATIONS AND CONTRAINDICATIONS FOR LAMINOPLASTY

• TECHNIQUES OF LAMINOPLASTY AND THE SUPPLEMENTARY PROCEDURES
  • Unilateral Hinge Laminoplasty
  • Procedures Supplementary to Laminoplasty

• POSTOPERATIVE MANAGEMENTS AFTER LAMINOPLASTY

• RESULTS AND OUTCOME
  • Neurological Results
  • Roentgenographic Outcome
  • Long-Term Results (Fig. 8)
  • Complications

• REFERENCES

Choice of surgical procedure for cervical spondylotic myelopathy was discussed based upon comparative studies. Neurological results, surgical complications and invasiveness of surgery were compared with comparable groups of laminectomy, anterior interbody fusion, subtotal corpectomy and laminoplasty.

Neurological results were better and more durable in the subtotal corpectomy and laminoplasty groups. Incidence of surgical complications and invasiveness were less in the laminoplasty group. We concluded as follows: For a patient with a narrow spinal canal and multisegmental involvement with or without spinal canal stenosis, laminoplasty is the procedure of choice. This principle can be applied for myelopathy secondary to soft disc herniation. For a patient with kyphosis or instability of the cervical spine, anterior spinal surgery is indicated.

Cervical spondylosis is treated surgically either by an anterior approach or a posterior approach. The decision on whether to fuse or not to fuse can be relatively easy or quite difficult depending on which approach is used. The primary purpose of fusion is to increase stability when actual or potential instability exists, either from a disease process or other causes such as surgical intervention. In cervical spondylosis a second purpose is to put the involved area at rest, thus reducing local irritation which may result in resorption of pathological osteophytes. Since an anterior approach entails resection of disc and various parts of the vertebral body, a fusion is strongly advised and is frequently a necessity.

Posterior decompression presents different problems. Open-door laminoplasty minimally interferes with supporting structures that affect stability, so fusion is not a consideration. Laminectomy, however, does entail major bone resection, especially if a radiculopathy is present and facet or uncovertebral joint decompression is necessary. This resection is usually confined to one or, at most, two-levels and the fusion confined to these levels. Since the posterior approach is favored for multiple-level spondylosis, this limited fusion still allows movement at the remaining decompressed segments, retained movement being an advantage of the posterior approach. The types of fusion that can be done are limited since they are confined to the lateral mass or joints because of the prior bone resection.

In evaluating the desirability of fusion, the long-term effects should be carefully considered. Removing motion from one joint adds stress to adjacent joints. Five, ten or fifteen years later the resulting degenerative change may present a problem that is sometimes more serious than the original one.

Because cervical spondylosis in and of itself does not cause cervical instability, the indications for surgical instrumentation for cervical spondylosis are limited. The indications for instrumentation are non-union after anterior cervical spinal fusion, instability after extensive corpectomy, or listhesis due to spondylosis. Anterior instrumentation, using plate and screw systems, is described in another chapter. Various types of posterior instrumentation have been utilized. Alligator plate fixation is a simple and easy instrumentation for moderate instability. Lateral mass screw and plate fixation can be used in cases requiring both decompression and fusion.

Recently, various kinds of materials, such as titanium, hydroxyapatite, alumina ceramic or glass ceramic, have become available as substitutes for bone graft. One-level anterior fusion is performed using a block of substitute. However, it has been shown that autograft bone is more reliable than such substitutes. A spacer made of hydroxyapatite, alumina ceramic or glass ceramic may be used for laminoplasty. There is a relatively small donor site complication rate in this operation.

Neurologic deterioration after surgery is one of the most serious complications of surgery for cervical compression myelopathy. It is divided into two subgroups depending on the time of onset; early onset (i.e. regressions of onset within the first year after surgery) and late onset (more than one year after surgery). Early onset deterioration, of course, includes an accidental damage on neural tissue during surgery which can be prevented by meticulous operation or applying a procedure offering a wider visual field, such as subtotal corpectomy with strut bone graft (SCS). Use of a surgical microscope also provides superior illumination and magnification in a small surgical field. Management of direct complications are discussed in the other chapters, and here we describe the detection and treatment of unpreventable neurological complications.

Complications of the anterior and posterior surgical approaches to cervical spondylosis are uncommon, however, they can have devastating consequences. It is with an understanding of the potential complications that may occur that improvements in technique and results may follow. In order to treat these problems, the surgeon must first understand the etiology and consequences of their occurrence. A more appropriate plan management of a complication can then be formulated.

The morphometry of the spinal cord in patients with cervical compression myelopathy revealed a close correlation between the transverse area and the spinal cord plasticity. The latter is defined as potential recovery from neurological impairment after decompression surgery. The transverse area of the spinal cord thus proved to be a reliable parameter dictating its plasticity under compression. Various factors, such as chronicity of disease, age at surgery, and developmental or acquired dynamic canal stenosis, influenced the transverse area. Changes of intramedullary signal intensity on MR images indicated both reversible and irreversible degenerations of the spinal cord as well. An extensive intramedullary syrinx or binocular lesion with high signal intensity (T2-weighted) revealed poor prognosis of myelopathy in general.

Cerebral palsy (CP) is an inclusive term used to describe a group of nonprogressive disorders occurring in young children in which disease of the brain causes impairment of motor function.¹ Therefore, generally, patients with athetoid CP are considered to be in a fixed condition. However, patients with athetoid CP often show neurological deterioration and become more dependent after their twenties. These new deficits are most often caused by cervical myelopathy and these patients become progressively more disabled. Moreover, special attention should be given to the fact that this progressive phenomenon frequently occurs in young patients. Although it is important to be familiar with this fact in providing care to athetoid CP patients, the disorders of the cervical spine in this patient group are not widely recognized. Frequently these patients fail to be given the appropriate concern and necessary treatment with the proper timing and they progress to a completely dependent state. There are several documents reporting on the degenerative changes of the cervical spine^2–4 and the results of surgery for cervical spondylotic myelopathy and/or radiculopathy^5,6 in athetoid cerebral palsy. However, few studies addressed the actual cause of the high incidence of cervical myelopathy in athetoid CP patients. The present study deals with the premature development of cervical spondylosis in athetoid CP patients, the structural abnormalities leading to cervical myelopathy and its treatment with a focus on surgery, based upon over ten years of observation and care of these patients.

It is well known that minor trauma, not enough to cause bony damage, sometimes causes or deteriorates cervical myelopathy. The mechanism involved in myelopathy is still controversial, but increased spinal cord vulnerability to trauma is attributable to pre-existing compression of the spinal cord and its consequences. MR imaging can be used to visualize the intramedullary damage as a lesion of distinct signal intensity, which is likely to be situated at the C¾ vertebral level. These patients often present with the manifestations of central cord injury but occasionally suffer from complete spinal cord injury.

Although conservative treatment has been recommended as the choice of treatment, surgical intervention should be indicated for injured patients with developmental canal stenosis and/or compressive spondylotic lesions impinging on the spinal cord.

The incidence of cervical spine injuries in Switzerland was 272 per 100 000 insured people. The value of degenerative changes as a risk factor for a prolonged recovery after whiplash injury cannot be confirmed with satisfaction, although some evidence can be drawn from retrospective studies which demonstrate higher percentages of degenerative changes of the cervical spine in the therapy resistant groups. Careful diagnostic procedures will allow exclusion of bony lesions and initiate adequate therapy, especially intervention that promotes activity such as mobilization/manipulation and exercises in combination with analgesics or non-steroidal anti-inflammatory agents. Early return to work is recommended. Return to usual activities should be encouraged as soon as possible, typically in less than one week for grade 2. Work authorization prescription should be reassessed in three weeks.

Ossification of the posterior longitudinal ligament (OPLL) is an intractable disease which causes severe myelopathy and radiculopathy. The etiology of OPLL has not yet been fully elucidated. In recent years, however, the Investigation Committee on the Ossification of the Spinal Ligaments of the Japanese Ministry of Public Health and Welfare has concentrated its efforts on clarifying the etiology of this disease. Specifically, molecular and cellular biological studies have further elucidated the actual pathogenesis of OPLL. This chapter summarizes the most recent basic scientific and clinical findings regarding this unique entity.

The following sections are included:

• Index