Seminars in

ARTHRITIS AND RHEUMATISM AUGUST

VOL 20, NO 1

Anatomy

and Physiology

of the Cervical

By John H. Bland and Dallas Although

the

studied spine

lumbar

from

1934

has received

physiological,

of the are

authors

spines

and

logically, article

collected

studied

them

and

nucleus

nerve

root

(anterior) volume

to

anatomy

spinal canal,

size

menisci

and the anatomy autonomic

0 1990 by W.B. INDEX

WORDS:

physiology:

in this

anatomic

charac-

the

sites,

position

uncinate

relation

shape

anterior

system

of the

of spinal

of the and

spinal

posterior

of the zygapophyseal

and clinical

nervous

human physio-

pulposus,

and

of the

The

in 1955,

whole

Reported

root,

often

warrant

to

anatomically,

exit

nerve

are spine.

Beginning 171

important

of the

cord

spine

histologically.

are clinically

Anatomic,

cervical

correlation.

cervical

biomechanical

extensive

have

process,

canal,

lumbar

too

teristics motor

and

to the

far

such an assumed the

extensively the

far less attention.

to apply

differences

was

present,

biochemical,

characteristics presumed

spine

to the

significance

in the cervical

joints, of the spine.

Saunders Company. Neck:

cervical

spine;

anatomy:

pathology.

C

LINICAL SYMPTOMS and signs usually reflect abnormal function of a tissue or organ system. Disease in most instances has a visible component and the study of morbid anatomy was, and should now be, the classic approach to its understanding. Recently, there has been considerable interest in molecular and cell biology; gross anatomic studies are regarded as outmoded, old fashioned-even irrelevant! Still, as William Blake wrote, one need not be limited to the “Vegetated Mortal Eye’s perverted and single, flat vision” if one looks not with, but through, the eye.*?

*Blake W: Jerusalem, in Keynes G (ed): The Writings of William Blake (vol 3). London, England, Nonesuch Press, 1925, Ch 3, line 11. *Buliough PC: Understanding osteoarthritis: The value of anatomic studies. J Rheumatoi 14:189-190,1987

1990

Spine

R. Boushey

The major medical advances over the last 100 years stem from an intensive study of biochemistry and immunology; evolution and maturation of cell biology illuminated morbid anatomy, but only because morbid anatomy was studied in great detail, eg, immunofluorescent studies in renal pathology allowed us to see “through the eye,” disclosing the detailed cellular and molecular understanding of these diseases. Although it is too little appreciated, morbid anatomy remains a key to understanding clinical disease. In the case of the cervical spine, there has been relatively little morbid and microscopic anatomy, presumably because of difficulty of obtaining whole human cervical spine specimen. This article reflects our deep, enduring interest in cervical spine anatomy dating to a single clinical experience in 1955 when the first spine studied was bequeathed to one of the authors (JHB). Over this period, a total of 17 1 whole human cervical spines have been removed post mortem, obtained from anatomical laboratories and the coroner’s office.

From the University of Vermont College of Medicine, Department of Medicine, the Rheumatology and Clinical Immunology Unit, and the Department of Anatomy and Neurobiology, Section of Gross Anatomy, Burlington. John H. Bland, MD: Professor Emeritus of MedicineRheumatology. Department of Medicine. and the Rheumatology and Clinical Immunology Unit, University of Vermont, Burlington; Dallas R. Boushey, Assistant Professor Emeritus of Anatomy and Neurobiology, the Department of Anatomy and Neurobiology, Section of Gross Anatomy. Supported by Research Grants from the National Institutes of Health, Arthritis and Rheumatism Branch and by the Irene Heinz Given and John LaPorte Given Foundation. Address reprint requests to John H. Bland, MD. University of Vermont College of Medicine, Rheumatology and Clinical Immunology Unit, Given Medical Bldg. Rm 0302, Burlington, VT 05405. Q 1990 by W.B. Saunders Company. 0049-0172,f90/2001-OOOl$5.00/0

Seminars in Arthritisand Rheumatism, Vol 20, No 1 (August). 1990: pp l-20

2

BLAND AND BOUSHEY

The cervical spine is the most complicated articular system in the body; there are 37 separate joints that function to carry out the myriad movements of the head and neck in relation to the trunk and subserve all specialized sense organs, eg, eyes, ears, nose, and tongue. The seven small cervical vertebrae with their ligamentous, capsular, tendinous, and muscle attachments are poorly designed to protect their contents, compared with the skull above and the thorax below. The contents of this anatomical cylinder interposed between skull and thorax include carotid and vertebral arteries, the spinal cord, the anterior and posterior nerve roots, and in its uppermost portion, the brain stem. The extremely flexible cervical spine balances a 10 to 15 pound ball, the head, on the lateral masses (zygapophyseal joints) of the atlas. The head acts as a cantilever on top of the highly mobile neck. Normally the neck moves over 600 times an hour, whether we’re awake or asleep; no other part of the musculoskeletal system is in such constant motion. The cervical spine is subject to stress and strain in ordinary, every day activities, such as speaking, gesturing, rising, sitting, walking, turning, and even at rest lying down. The position of the cervical spine discloses mood and attitude. The spine in flexion suggests depression, withdrawal, sadness, mourning, and sometimes prayer, (“bowing” the head in supplication); while “chin extension of the cervical spine, reflects up,” optimism, confidence, and savoir faire. A “pain in the neck” is such an unpleasant experience that it is used as an invective for any annoying event, even a person. The word “neck” is also used as a verb-to neck-as in kissing and caressing in love making, currently out of style! Normal function requires that all movements be made without damaging the spinal cord, vascular supply, and millions of nerve fibers.

CLINICAL SIGNIFICANCE

Is the cervical spine clinically important? In one epidemiological study, over 10% of the population recalled having had at least three episodes of pain in the neck last year. Another reports that at any one specific time as much as 12% of the women and 9% of the men in the population experience neck pain with or without associated arm pain, and 35% of people can recall such an

episode.2 An important clinical epidemiological study disclosed that a history of stiff neck and arm pain was elicited in 80% of a population of male industrial and forest workers. In a second study by the same investigators, the figure was modified to 5 1% in a series of 1,193 male workers (a broad spectrum of jobs) but only 5% experienced work loss as a consequence of the pain.3*4 Further study of neck pain reports that 70% of adults who visited their doctors were well or improving within 1 month.’ There is little else known about the epidemiology of acute or chronic neck symptoms. From general clinical experience and these scant insights, we postulate that neck pain is a recurring ubiquitous clinical event, a mild to modest transitory nuisance to most of us. However, with such enormous morbidity, if even a small percentage of those with symptoms seek medical diagnosis and care, the impact on society would be striking and dramatic. We strongly suspect that such is the case, but the relevant epidemiological data are concealed in such clinical headings as disc disease, spine injuries, and injuries to the trunk where the cervical pain syndromes are overwhelmed by low back pain. With so much morbidity, there is precious little systematic information on the clinical features and natural history of neck disease. Until 1948, shoulder, scapular, chest, arm, and forearm pain syndromes were mysteries, That year Lord Russell Brain6 described a myelopathy-spinal cord compressionthat was clearly, unequivocally ascribed to primary cervical spine disc disease, promptly termed cervical spondylosis. The concept was accepted, and a whole spectrum of mysterious clinical syndromes became clearly understood.

A HISTORICAL VIGNETTE

There is an important relation between backache and neck pain. During and after World War I, backache was a rarely reported problem; but when World War II began, backache was the diagnosis in 40% of patients admitted to a general military hospital with “arthritis and allied conditions.“7 The period between wars saw backache emerge as a major medical problem for the military, industrial medicine, the insurance industry, public health, and certainly medicine in

ANATOMY

AND PHYSIOLOGY OF THE CERVICAL SPINE

general.’ Why the emergence of backache in the 193Os? The expression “my aching back” arose but was soon superseded by “my injured back.” The notion of injury implies trauma, damage, and somebody or something is at fault, ie, culpability. This general concept of injury emerged out of the coincidence of two events: first, an astute clinical observation made at the University of Vermont; second, the introduction of the Worker’s Compensation program. The clinical observation was made over 50 years ago by R.M.P. Donaghy, a neurosurgeon, and Albert Mackay, a general surgeon.g The patient was a 25year-old man injured in a twisting ski accident. The doctors suspected and formulated the idea of a herniated nucleus pulposus; such had not been described then. The patient was referred to Dr Frank Ober in Boston and seen by his associate, Dr Barr who referred him to Dr W. Jason Mixter at the Massachusetts General Hospital in Boston. Multiple sclerosis was a considered diagnosis, and following myelogram, a probable diagnosis of tumor of the high cauda equina was made and exploration followed. An “enchondroma” (nucleus pulposus) was removed, and the patient was cured (June 1932).” In 1934, Mixter and Barr attributed backache in 19 patients to herniation of the nucleus pulposus, demonstrated surgical cure, and named the condition “rupture of the intervertebral disc.“” At the time all state legislatures and judiciaries were considering Workman’s Compensation statutes. Subsequently, all states passed laws that provide medical care and compensation for wages lost due to “personal injury that arises out of and in the course of employment and occurs by accident.” Lawyers think of “rupture” as a rip, tear, or bursting of normal anatomical structure, thus it was a “personal injury.” Even in 1989 a worker with a backache given a diagnosis of “ruptured disc” will be compensated irrespective of a defined discrete cause of their symptoms. A surgical scar suppresses arguments to the contrary much more reliably than the surgical procedure results in cure. From 1934 to about 1965, both clinicians and the courts thought that “ruptured disc” was the cause of most persistent and disabling backache. These views changed gradually as the confidence

3

of diagnosticians, enthusiasm of surgeons, and self-righteousness of the compensation bureaucracy has faded. Epidemiological studies belied those views. The cause of most regional backaches today is indeterminate.“,” Ruptured disc is common in asymptomatic patients. “Backache” is no longer a surgical disease. Greater than 80% of such patients will be well or much better in 2 weeks, with most of the remainder recovering, provided they are well cared for. In this same era, valid and sophisticated research on the lumbar spine was accomplished, as was clinical, radiological, anatomic, pathological, biomechanical, biochemical, physiochemical, and histological research. This was an enormous advance in knowledge of the lumbar spine, but not the cervical spine. There has been very little penetrating research done on the cervical spine. In fact, even the basic anatomy is incompletely explored. During this historical period, the anatomic, radiological, clinical, biomechanical, and biochemical characteristics of the lumbar spine were transferred in the minds of physicians as applicable to the cervical spine. Too many gross differences between the lumbar and cervical spine allow this extrapolation. There are obvious differences. (1) The neck is designed for relatively enormous degrees of mobility. (2) Vertebrae are much smaller and far more anatomically complicated. (3) Zygapophyseal joints are oriented on very different planes. (4) Discs are grossly different-physiologically, anatomically, biomechanically, biochemically, and embryologically. (5) After age 45, there is little or no nucleus pulposus. (6) The lumbar spine is designed for weight bearing and serves a totally different biomechanical function. The lumbar spine is hydrodynamically different than the cervical spine. (7) Cervical discs are far more ligamentous and dry, with little proteoglycan present. (8) The forces operating in the neck are different, not bearing the whole body weight but being influenced by the great mobility of the upper extremities. (9) The pain patterns arising from sclerotomeand myotome-derived structures in the neck are very distinctive and perhaps more clinically usable than those of the lumbar spine. (10) Myelopathy is much more common in the cervical spine than radiculopathy. (11) The diagnostic use of roentgenogram, myelogram,

4

BLAND AND BOUSHEY

computed tomography (CT) scan, and magnetic resonance imaging is less meaningful in the cervical spine than in the lumbar spine. SOME PHYLOGENETIC MATTERS OF CLINICAL IMPORTANCE 1. The occipital bone and the posterior fossa have evolved from the reptilian upper four vertebrae. The nerve supply to this area is from Cl, 2, and 3, and clinical disease in that area is reflected in the referral patterns of those roots; myotomaland sclerotomal-derived structures, when abnormal, are perceived in the forehead and retroorbital areas. 2. The transverse processes in the cervical spine have evolved into the intervertebral foramina and the gargoyle-like structures that carry the anterior and posterior nerve roots and the posterior root ganglion. The nerves occupy about 25% of the space available. The remainder of the space is occupied by lymphatics, blood vessels, areolar and fatty tissue, constituting a compressible safety cushion allowing physiologic encroachment without damage to nerve roots. The bony prominence, the uncus or uncinate process, on the lateral and posterolateral aspect of the cervical vertebrae from C3 through C7 constitutes the phylogenetic remainder of the costovertebral joint in reptiles. Of clinical significance, this bony elevation enlarges from age 9 to 14 years, and beyond the age of 40 years it constitutes a bony bulwark preventing herniation laterally or posterolaterally. 3. The odontoid evolved from the body of the first cervical vertebra that became the atlas. Thus, free movement of the head became possible with the eccentrically located “axle” of the axis, the odontoid, allowing enormous mobility at that level, especially in rotation. 4. With the evolution of the extremities, the neural traffic increased at the level of the spine where extremities appeared. The spinal cord enlargements reflect this evolution. The nerve roots (particularly the sensory roots) are much larger in the cervical spine than in the lumbar and thoracic spine. Riblessness in the cervical and lumbar areas had great survival value because it allowed growth of limbs and their associated neural innervation. 5. The nucleus pulposus, present at birth, and

remaining until age 9 to 14 years, is made of remnants of primitive notochord and proteoglycan material. However, in the cervical spine, contrary to events in the lumbar spine, the nucleus pulposus gradually disappears. In 17 1 whole human cervical spines, we found no evidence of a gel-like nucleus pulposus after age 45. The intervertebral disc in the cervical spine is “dry,” more like a ligament than a “disc,” fibrous, and gradually breaking up in various sized pieces, seemingly a universal, probably physiological, development. CLINICAL SYNDROMES IN THE CERVICAL SPINE

In medical practice, there is an expectation that by detecting a spectrum of clinical signs and symptoms, a definitive diagnosis can be made and treatment instituted. The flaw in this expectation is that cervical spine complaints have been classified into various empirically defined syndromes, each with an alleged basis. The implication is that if one identifies the features said to be characteristic of each syndrome, a diagnosis can be made. In the case of the cervical spine, there has never been a clinical-pathological correlation. The field of cervical spine pain is dominated by descriptions of syndromes offered by various “authorities” as if their underlying pathophysiology had been determined. It has not. Authorities view similar complaints in greatly different ways. Some view neck pain as entirely discal in origin, others prefer the zygapophyseal joints, muscle imbalance, poor posture, and psychogenic origins. The most common complaint related to the cervical spine practice is pain-its localization, and origin. There is no point in proceeding to evaluate therapy if the pain-sensitive structure is not known. Traditional techniques of clinical investigation-roentgenograms, myelography, CT scans, magnetic resonance imaging-do not show sources of pain. Clinical pathological correlations have not been established to prove that a particular radiological abnormality is diagnostic of the source of pain. In fact, there is no correiation between radiological manifestations and clinical symptoms and signs. Except for studies by Tondury,13 Payne and Spillane, I4 Holt and Yates, I5 Frykholm,16 and

ANATOMY

5

AND PHYSIOLOGY OF THE CERVICAL SPINE

removed and studied 17 1 whole human cervical spines. This article reports our anatomic findings. METHODS The cervical spine was removed intact by sawing through the first thoracic vertebra, cutting the occipital membrane ligaments, connecting the posterior arch of the atlas to the occipital bone, and then, with a sharp chisel, cutting off of the occipital condyles. Each specimen included the atlantooccipital joint intact. The whole cervical spine, by blunt and sharp dissection, was complete with spinal cord, all muscles, tendons, ligaments, vessels, and joints to the middle of the first thoracic vertebra. The foramen magnum was removed from some of the later cadavers. Viscera and brain are removed in the routine manner, and the cadaver is placed in a supine position with a block under the neck. A chisel incision is made which encircles the foramen magnum from the inner side of the skull and passes posteriorly through the squamous occipital bone. The incision is marked lightly and deep incision is carried forward through the petrous temporal and basioccipital bones. Cracking the squamous occipital bone is thus avoided.14 The whole cervical spine was photographed in color anteriorly, posteriorly, and laterally (Figs 1 and 2). Roentgenograms are taken antero-posteriorly (AP), laterally, and both oblique views. The necks were fixed in 10% formalin for 14 days, after which they were cut with a thin blade band saw into sagittal, coronal, and transverse slabs of up to 10 mm thickness (Fig 3). We found that we learned the most from the sagittal slabs, the majority were so cut. Roentgenograms were taken of all the slabs, and arranged in order from one Fig

1:

spine,

Specimen vertically

posterior shows tate

aspect. the

of a whole positioned Upper

one third

cord

suspended

spinal

ligaments

(arrowheads);

canal at the foramen

magnum

arrow);

condyles

the occipital

skull with the

edges

visible arches

a sharp of

human and

the

(arrows): of the atlas

chisel

by the

capacious level (short, were

(laterally

anterior

from

of the picture denspinal open

cut off the

situated)

and

joint

are

atlanto-occipital the

cervical

viewed

and

posterior

can be identified.

Hirsch et al,” there have been relatively few detailed gross and microscopic anatomic and pathological studies on the human cervical spine. This investigation was undertaken with the belief that clinical, radiological, post mortem anatomic, and pathological studies would provide a necessary basic background knowledge for understanding and rationally managing clinical disorders of the cervical spine, mainly cervical osteoarthritis. Between 1954 and 1984 we have

Fig 2:

A close-up

odontoid

atlanto-occipital (arrows), visible.

view

“peeking”

joints

the There

surrounding

of Figure

through

hyaline

are more cartilage

is gross

the odontoid.

1 showing

(arrowhead); apparent surfaces

granulomatous

the the here being

tissue

6

BLAND AND BOUSHEY

side to the other (Fig 4). Figures 5, 6, and 7 illustrate respectively a sagittal section of a whole spine, a histological section of the whole spine, including the meninges and spinal cord, and a histological sagittal section of the axis and atlas. All gross specimens were examined simultaneously by an anatomist and a rheumatologist using a dissecting microscope with magnification up to 40x. Normal and abnormal anatomical observations were made. The transverse and AP diameter of the spinal canal was measured in millimeters. Anterior and posterior vertebral osteophytes were identified

Fig 4:

This illustration

shows the radiological

study in serial array, sagittal slabs in Figure 3, permitting microscopic

This illustration

Fig 3:

nique of obtaining

demonstrates

the tech-

sagittal sections of a whole

cervical spine, cut with a thin blade band saw from

the left through

the midline to the right

side. In this specimen

12 sagittal sections were

cut. Sections

for histological

hematoxylin

eosin staining allow a serial three

and

dimensional

build up of any desired set of microscopic tissue planes,

eg. from

intervertebral

the spinal canal through

foramina.

correlation

of roentgenograms

with

histological data.

and graded as 0, 1, 2, or 3.* Gross pathological criteria for osteoarthritis were agreed upon and the zygapophyseal joints, right and left, were graded 0, 1,2, or 3.* The ligamenta flava were assessed for hypertrophy and graded 0, 1, 2, or 3.* Intervertebral discs were graded 0, 1, 2, or 3’ depending on the extent of fissures identified and their connection with the so called joints of Luschka. Decalcification was accomplished by immersing the necks in 10% formic acid, testing for calcium every few days, and changing the solution at intervals for 10 to 16 weeks. When the test for calcium became negative the spine was removed and prepared for sectioning and histological study. In many instances whole spines were cut, serially stained with hematoxylin and eosin, and examined. Smaller sections were cut to study dural root sleeve fibrosis, lesions of the nerve roots, intervertebral foraminal lesions or specific disc joints, and zygapophyseal or Luschka joints. Individual specimens or parts of specimens were cut in one of four planes, sagittal, coronal, oblique, or transverse, depending on the study made and question asked. Sagittal sections show the degree of lordosis, shape and size of vertebral bodies, intervertebral discs, and articular columns with the zygapophyseal joints. Coronal sections best show the shape of vertebral bodies,

the

*Graded: 0, absent; 1, definite; 2, moderate; 3, severe.

ANATOMY

AND PHYSIOLOGY OF THE CERVICAL SPINE

ANATOMIC

STUDIES

Pulposus

Nucleus

The nuclei pulposi of the cervical intervertebral discs, present at birth, are progressively less evident in adolescence, and by age 40 years have disappeared. The adult disc is ligamentous-like, “dry,” and is composed of fibrocartilage, islands of hyaline cartilage, and tendon-like material,

This

Fig 5: section

specimen

of a cervical

is a gross

spine.

the atlas

at the top (arrow

is eroded

and the anterior

is filled spinal pressed

with cord

is cut

normal

matoid

very

plane

and narrow

did

C5-6,

joint

(arrow)

the

and is com-

intervertebral

but

slab

arch of

the odontoid

tissue;

level; the C2-3

height

microscopically discs were

head);

in sagittal

by extensive

midline

anterior

atlanto-occipital

granulomatous

loma at the C5-6 are

Note

disc granuand C3-4

contain C6-7,

discs

granuloma and

and destroyed

C7-Tl by rheu-

granuloma. Fig 6:

This illustration

of a whole intervertebral discs, articular columns with zygapophyseal joints, and the “Luschka joints” (uncovertebral, neurocentral). Oblique cuts in a plane at right angles to the axis of the intervertebral foramina show the dimensions of the foramina, the protrusion into foramina of osteophytes from vertebrae, Luschka or zygapophyseal joints, and the relative size and position of the nerve roots. Transverse plane serial sections show the relation of the spinal cord and nerve roots, the posterior ganglia, the dural, pial, and arachnoid investments, the diameter of the spinal canal at various levels, and the relation between the spinal canal dimension and the size of the cord. The soft tissue in the canal and the foraminal exits were examined.

(A)

and

human

seen;

ation.

The

stained.

is gross

odontoid

are

very

disc is of normal and

height

proved

destruction

throughout.

are also grossly

apparent

the

anterior

and

are inordinately

Leon Sokoloff.

posterior thin.

posteri-

cord are well

bral erosions ligaments

are

sublux-

eroded

granulomatous

Even

anterior atlas

atlanto-axial

and spinal

narrow

section

The

of the

is grossly

Meninges

The C2-3

rest

spine.

(B) arches

there

orly (arrow).

the

cervical

posterior

easily

is a histological

but all to have Verte-

(arrow).

longitudinal

Prepared

by Dr

8

BLAND AND BOUSHEY

Fig 7:

This specimen

section

of an atlas and an axis. The anterior

arch

(A)

subluxated

of the

is a histological

atlas

(left)

is in a 12

position and the posterior

has compressed

sagittal mm

arch (PI

the spinal cord at the foramen

magnum level (arrow),

ie brain stem compres-

sion. There is the remnant of disc in the lower odontoid

(arrowhead)

and both anterior

was present in all the spines studied, we believe this to be a physiologic event, peculiar to the human cervical spine and related to biomechanits. The disc demonstrates gradual disappearance of the nucleus pulposus and deposition of ligamentous, fibrocartilage-like tissue (Fig 10). In the cervical spines from people older than 60 years, the annular dissection has reached the midline, suggesting a bisected disc from uncinate process to uncinate process. The overall material in the disc has become “dry” without gel-like material, suggesting an absence of proteoglycan, and acquiring a dense, ligamentous-like character, as well as marked loss of volume of disc tissue. We propose these physiological events are a consequence of shearing planes of tissue from biophysical and biomechanical events. We frequently found pieces of hard, marginally elastic disc tissue free in the disc that conceivably could herniate.

and

posterior odontoid surfaces are eroded by rheu-

Uncinate Processes

matoid

The uncinate processes (uncus, L. a small hook) are normal bony excrescences placed laterally and posterolaterally on C3 through C7. The uncinate process preceded the evolution of the extremities and evolved from the reptilian and avian costovertebral joints, joining ribs to vertebrae. With increasing age, the uncinate processes enlarge and often flatten, losing their sharp bony characteristics (Fig 11). This osteogenic phenomenon forms a bulwark of bone laterally and posterolaterally, which, we believe, prevents disc herniation in this area. Figure 12A shows an anterior view of an articulated cervical spine from a 42-year-old man. Figures 12B, C, and D illustrate various anatomic characteristics of uncinate processes.

granuloma.

destroyed,

The

C2-3

disc is nearly

cleft all the way through,

surfaces readily apparent.

Prepared

opposing by Dr Leon

Sokoloff.

with little or no proteoglycans. Thus, after age 40 years, it is impossible to clinically herniate the nucleus pulposus as there is none. Figure 8 is a coronal section of the cervical spine of a 4-year-old child. The nucleus pulposus is clearly present in mid-disc. The uncinate processes phylogenetically represent remnants of ancient costovertebral joints in birds and reptiles. During evolution, they preceeded the development of extremities and cervical and lumbar ribless zones. By ages 9 to 14 the nucleus pulposus is far less evident and bilateral clefts have developed in the postero-lateral annulus fibrosus, medial to the growing uncinate processes of the vertebra. This cleft is the site of the alleged joints of Luschka, uncovertebral, or so-called neurocentral, joints (Fig 9). Between ages 20 and 35, the clefts gradually enlarge and dissect tissue planes toward the midline, where each finally meets its counterpart from the opposite side. Because this phenomenon

Nerve Root Exit Sites

From the level of C3-4 distal, the anterior and posterior nerve roots exit through the dural root sleeves and are below the level of the intervertebral disc by 4 mm to 8 mm. This relation is a consequence of the early formation of the nervous system, including the spinal cord and nerve roots, followed much later by rapid growth of the bony vertebral spine. With growth and lengthening of the cervical spine, physiological traction is

ANATOMY

AND PHYSIOLOGY OF THE CERVICAL SPINE

Fig 8:

(A) This specimen

is a coronal

section of a 4-year-old

nucleus pulposus in mid-disc C5-8 (arrow), uncinate

process; C =

centrum

C6-7, C7-Tl.

(vertebral

section of the cervical spine of a 4year-old three

discs shown

costovertebral

(arrow).

joints).

The

Reprinted

uncinate with

boy’s cervical

spine showing

the

0 = odontoid: N = nucleus pulposus: U =

body). (8) This specimen

is a close-up

of the coronal

boy. The nuclei pulposi are obvious in the center of the processes

permission

are well

developed

from Hall MC: Luschka’s

(homologs

of ancient

Joint. Springfield,

IL,

Charles C. Thomas, 1965.

exerted on the cord and nerve roots. The dural root sleeve exit sites are then at the level of vertebral bodies rather than at disc level. Hence, it seems unlikely that disc disease could compress cervical nerve roots because the root exit zone is below the level of the disc (Fig 13). Incidentally, virtually all dural root sleeves become fibrotic, rigid, and stiff after the age of 50 years.

Anatomy of the Anterior (Motor) Nerve Root The anterior nerve root is normally situated very low in the intervertebral foramen, preventing compression. The posterior nerve root is well protected from disc herniation. However, the zygapophyseal joints may become enlarged and osteophytic and could compress the posterior roots. We believe that radiculopathy, though

very unusual, is a consequence of zygapophyseal joints impingements, but not due to enlarged uncinate processes (so called Joints of Luschka or the discs) (Fig 14).

Relation Between Spinal Cord Volume and Bony Canal Normally there is considerable individual variation between the spinal cord volume and space available in the bony canal. This is likely a constitutional or genetic characteristic. Clinically, if one inherited a “fat” spinal cord and relatively small bony canal, the development of osteoarthritis would have a narrow margin for compromise of cord function. The ideal is thin cord and a capacious spinal canal, affording a large margin of safety (Fig 15).

BLAND AND BOUSHEY

Fig 9: (A) This specimen is of a coronal section of a 14-year-old girl’s cervical spine for comparison with Figure 8. Note postero-lateral clefts have developed in the annulus fibrosus just medial to the uncinate

process (arrows).

The uncinate

process is well developed

the uncinate process of Figure 8. The vertebral on viewer’s (arrows).

right. (8) A close-up of A illustrates

Reprinted

with

permission

from

and relatively

much larger than

artery has been cut in the coronal plane (arrowhead) the clefts in the postero-lateral

Hall MC: Luschka’s

Joint,

Springfield,

annulus fibrosus IL, Charles

C.

Thomas, 1985.

Anatomy of Anterior and Posterior Spinal Canal

In people over age 45 the anterior spinal canal is characterized by bars of osteophytes at the level of the intervertebral discs, commonly compressing the cord to varying degrees and clinically symptomatic. The ligamentum flavum is hypertrophied and hyperplastic, projecting into the spinal canal and may compress the spinal cord posteriorly. The posterior longitudinal ligament in the cervical spine is three- to fivefold thicker and more developed than in either the thoracic or the

lumbar spine, where it becomes attenuated. Because the position of the posterior longitudinal ligament prevents herniation posterolaterally and posteriorly, this may partially explain the unusual occurrence of cervical disc herniation. The anterior longitudinal ligament is attached firmly to the vertebral bodies but only loosely at the disc area. The posterior longitudinal ligament is firmly attached to the disc area but loosely to the vertebral surface. These anatomic facts may explain why osteophytes are larger and more common anteriorly than posteriorly. In the cervical region only (not in the thoracic or

11

ANATOMY AND PHYSIOLOGY OF THE CERVICAL SPINE

lumbar region), the posterior longitudinal ligament is broad throughout, while in the thoracic and lumbar region it narrows strikingly behind each vertebral body. A strange and poorly understood cervical spine characteristic is the marked remodelling, hypertrophy, and hyperplasia of cervical vertebrae that occurs with increasing chronologic age (Fig 16). Menisci of Zygapophyseal Joints

All zygapophyseal (posterior) joints have menisci in a circular arrangement with varying degrees of projection into the joint. These seem to have a propensity to proliferate in a fibrous-like pannus. Most hyaline cartilage surface is fibril-

Whole cervical spine specimen (cut Fig 11: coronally) from an 80-year-old woman. Note the striking decrease in overall disc substance, marked narrowing of all discs, completely bisected discs (arrowheads right), surfaces facing one another, in life only a potential space. Also note the large, flattened

and deformed

uncinate

posterolateral

processes

on upper,

edges of the vertebrae (arrows), a bulwark of bone that increases in volume with increasing chronologic age.

Fig 10:

A coronal section of cervical vertebrae

C4, and C5, and intervertebral adolescent dissecting

girl illustrating toward

disc from an

the annular

the midline

clefts

in collagenous

tissue planes of the anulus fibrosus (arrows). There is no evidence of synovium, subchondral bone, or joint capsule. See text.

lated with chondrocyte clone suspect the proliferation may be bilization, relative, or absolute. menisci provide the joint with 17).

formation. We related to immoWe propose the lubrication (Fig

Luschka “Joints”

Anatomically, a joint has certain structural elements, namely synovium, subsynovial space, hyaline cartilage, subchondral bone, and capsule. At the site of the alleged Luschka joints no such

Fig 12:

(A) This is an anterior

uncinate

process.

view of a normal articulated

(B) An anterior

process in the viewer’s

view of the C4 vertebrae

left and blunt remodelling

a cervical spine from an 64-year-old very large uncinate the viewer’s

processes

grown

cervical spine. The arrow illustrating

points to an

a sharp, remodelled

uncinate

uncinate process in the right. (C) A coronal view of

man. The intradiscal surfaces are shown (arrowhead). up and overlapping

the vertebrae

right is a sagittal section seen by roentgenogram.

White

There are

above (white arrow). arrows

(D) On

point to the uncinate

processes as seen from within the disc, looking from the inside out. On the left is a sagittal section of the same anatomical Note the through

specimen

and through

showing

C4 vertebrae

clefts (black arrows

permission

from Ball J: The articular pathology

Rheumatic

Diseases (ERA).

toid Arthritis.

61:25-39,

International

1964.

in the middle and the lower half of C3 above. above and below C4 vertebra).

of rheumatoid

Congress

arthritis.

International

Reprinted

with

Study Center for

Series No. 61. Radiological Aspects

of Rheuma-

ANATOMY AND PHYSIOLOGY OF THE CERVICAL SPINE

Fig 13:

(A) A sagittal

arrows than

point

to exit

section

sites

at the level of the discs.

ligaments

have

leave

spinal

having

the

been

been

laid back,

the motor

rootlets

projected

superiorly

down bulges.

(lower

severed,

canal

black

The spinal

of a whole

(dural

root

See text. allowing

at vertebral faces

(anterior) (upper arrow).

the viewer;

cord runs down

the

showing

they

the anterior the spinal while short

the middle

apart

arrows).

The

spinal

artery

exit

section, at two ventral

sites.

Note

two

of the vertebrae

the anterior levels.

Note

surface

is seen (outlined

black rather

and posterior the

nerve

roots

of the

spinal

cord,

arrow)

as well

as

cord. (Cl In this spine the upper nerve roots are

the lower open

nerve

are at the level

a sagittal

discs to spring (2 black

from

black arrow) Incidentally

spine

and that

(B) In this spine,

levels

coming

cervical

sleeves)

arrow

ones are at increasing head

points

obliquity

to posterior

from

above

disc osteophytic

of the illustration.

structures were present; therefore, it seems improper to call this region a joint. We believe the anatomic structure we describe and the physiological sequence of events we propose constitute an accurate description of cervical intervertebral disc pathophysiology. Between 9 to 14 years of age a cleft develops in the lateral and posterolateral annulus fibrosus, a function of the unusual ability to rotate the cervical spine in obligate bipeds. Rather than forming a true joint, this cleft or fissure gradually dissects toward the midline to meet the lateral cleft dissecting from the other side. In this space there are only patches of synovium. With increasing age the disc is finally bisected in a transverse plane and the two surfaces are made up of a

peculiar mix of connective tissues: anulus-like tissue, fibrocartilage, hyaline cartilage, tendonlike tissue, and bony islands. The disc becomes narrower with the passage of time, sometimes nearly disappearing. We have dubbed this the “grin of Luschka” when the process is complete (Fig 16D). This finding was universal in 17 1 the spines studied (Fig 18).

The Autonomic Nervous System A large part of our nervous system is concerned with activities and vital functions of which we are unaware and over which we have no voluntary control. Claude Bernard proposed that a divine providence considered these autonomic activities far too important to entrust to a capri-

BLAND AND BOUSHEY

Fig 14: A coronal section through the intervertebral foramen at C7-Tl. The curved arrow points to the posterior

(sensory)

straight arrow to the anterior level in the foramen root ganglion. situated tected

very from

throughout

root and the

(motor) root. The

is proximal to the posterior

The motor root is anatomically low

in the foramen,

any

osteophytic

well

pro-

compression

its course from the spinal cord. See

text. To the right of the foramen the superior, posterolateral

is the cleft in

intervertebral

disc,

the anulus fibrosus.

cious will. “We are thrust into this world by smooth muscle, which is under the control of the autonomic nervous system. From moment to moment we are dependent for our conscious existence on the moderate contraction of blood vessels, routinely kept in this state by autonomic impulses. Most of the complicated processes of digestion, from the initial outpouring of saliva to the final riddance of waste, require the participation of autonomic nerves. Any vigorous exercise in which we may engage depends on cooperation of autonomic government of appropriate effectors, thus throughout eons of past time the physical struggle for existence has been made possible by that government-which preserves the stable states of the fluid matrix that are required for ready response to every call to action.” Led by Walter B. Cannon, physiologists the world over have worked long and hard to elucidate the functions of the autonomic nervous system in maintaining “le milieu interne.” Only

in the last two decades has research attention been paid to the manner in which the autonomic nervous system participates in neurologic diseases, or how the sympathetic-parasympathetic nervous system may be selectively deranged by pathological processes. Pertinent to the cervical spine and its clinical syndromes is the fact that no preganglionic sympathetic fibers are present in the neck. All neck fibers come from Tl, 2, and 3 levels, having their first synapse in one of the three cervical sympathetic ganglia, stellate, middle, and superior. The postganglionic fibers go in three directions. (1) Into the upper extremities providing all autonomic functions, circulatory vasomotion, sweating, proprioception. (2) Reenter the spinal cord through the intervertebral foramina and have synaptic connections in the vestibular apparatus, cerebellum, thalamus and hypothalamus. (3) Follow the distribution of the vertebral and carotid arteries in the brain. The earliest description of sympathetic nervous system syndromes was by Barre’* in 1926, and further described by his student Lieott” in 1928. So diverse and bizarre were the symptoms and signs that some authors did not associate them with the cervical spine.*‘**’ The current view is that the nebulous and bizarre complaints are explicable on the basis of known autonomic, neurologic, and pathophysiologic events. The clinical results relate to the interplay between mechanical derangements of the cervical spine and the cervical sympathetic system, the brain and spinal cord, the vertebral artery, the zygapophyseal joints, the cervical vertebrae, the scalene muscle system and preexisting arteriosclerosis.22T23 Though it was known by the ancient Egyptians of the 16th and possibly the 30th century that spinal cord injury involved more than just motor and sensory loss, a full grasp of the physical and physiological complexities of autonomic functional alteration is lacking. Nevertheless, we do have valid clinical, physiological explanations for such common cervical spine occurrences as cervical dizziness and ataxia; nystagmus; various syndromes of loss of proprioception, cervicoocular, and vestibulo-ocular reflexes; pupillary dilation on neck extension; postural and pathological gaits induced by cervical spine disease; and

ANATOMY

Fig 15: (white

(A) arrow)

A transverse and the

without

cord

showing

a grossly

arrow

heads),

section

large

The three

and spinal

cervical

canal.

(D)

C6 vertebra

spinal

cord,

myelopathy. cord

From

cervical

spines

middle

sections

(arrows)

left

of osteoarthritis.

relatively

illustrating

from

to right

a series

thin

very

through

constricting

spinal

sizes of spinal

spinal

change.

cervical

spine

specimens.

and

and spinal

spine (white sagittal

a relatively

These

24 on left to 89 years cords

canal

(C) A gross

(arrow)

canal

osteoarthritis

a whole

cervical

cord

of six different in age from

spacious

for extensive

mild osteoarthritic

ranging varying

the

tolerance

sections

narrow,

a rather

patients

illustrate

illustrating

ie, a great

(B) Coronal

and a relatively

for even spine

of whole

magnitudes

through

small

ie, an intolerance

spinal

sections

section

relatively

compression

of a whole

capacious

varying

15

AND PHYSIOLOGY OF THE CERVICAL SPINE

sagittal

on the right.

canals

as well

as

See text.

ataxia during the Romberg test.24*25Table 1 lists autonomic symptoms and signs arising from pathophysiologic changes in the cervical spine. SUMMARY

The following findings derive from studying 171 whole human cervical spines. (1) The nucleus pulposus, present at birth, is absent in the adult cervical spine. (2) The uncinate process,

present at and before birth, gradually enlarges superiorly, forming a lateral and posterolateral bulwark of bone, preventing herniation of disc material. (3) The posterior longitudinal ligament is four- to fivefold thicker in the cervical spine than in the thoracic or lumbar spines, probably preventing posterior herniation. (4) From C3-4 the nerve root exit sites are below the disc level, explained by bone growth exceeding spinal cord

Fig 16: (A) On the left, the specimen illustrates the posterior surface of cervical vertebra seen from inside the spinal canal, showing massive posterior osteophytes of the intervertebral discs, protruding into the anterior cervical spinal canal (arrows). The posterior longitudinal ligament is greatly thickened. On the right is a section illustrating the posterior surface of the spinal canal with immensely thickened and protruding ligamenta flava (arrows). (B) A whole cervical spine cut sagittally down the midline, dividing spine and spinal cord into two facing halves. The white spinal cord is in mid section. The upper left black arrow points to a greatly hypertrophied and hyperplastic anterior longitudinal ligament and very narrow disc. The lower arrow points to an extremely thickened posterior longitudinal ligament and large osteophyte compressing the spinal cord anteriorly. On the right, the white arrow points to severely thickened ligamenta flava compressing the spinal cord posteriorly. (C) A cervical spine cut from the lateral aspect exposing the spinal cord with its nerve rootlets and anterior and posterior nerve roots down the middle; P, posterior; A, anterior. To the left of the spinal cord is the dura mater and the hypertrophied ligamenta flava (arrow). To the right of the spinal cord is the anterior surface of the spinal canal showing the hypertrophied anterior longitudinal ligament and large posterior osteophytes at disc levels compressing the anterior spinal cord (arrows). The spinal cord has multiple compression sites. (D) A coronal section of a cervical spine from an 68-year-old man. Note the increasing bulk of the remodelled vertebrae from above downward; each larger than its neighbor above, representing extreme, presumably physiologic remodelling, hypertrophy and hyperplasia with increasing chronologic age. Incidentally note large, deformed and flattened uncinate processes (black arrow). cleavage of all the discs with very little disc elements remaining. desiccated, pebbly to knobbly disc surfaces facing one another (white arrow).

ANATOMY

Fig 17:

AND

PHYSIOLOGY

OF THE CERVICAL

SPINE

(A) Sagittal section of tygapophyseal

(see text) and the upper arrow proliferating

joints. The lower arrow points to a normal meniscus

points to a proliferating

meniscus.

meniscus of Figure 17A. upper arrow. It is a fibrous-like

hyaline cartilage (C) surface. (Cl An illustration

of a zygapophyseal

(B) A histological

section of the

pannus (PI proliferating

over the

joint held open by the examiner.

The hyaline cartilage surfaces are seen. In the joint, the arrow points to a normal meniscus. We found circular menisci in virtually all cervical zygapophyseal joint. The joint space (JSI is in the upper thickened

subchondral

joints. (D) A section through

third of the illustration.

bone (B). the hyaline cartilage having been completely

the bone and tightly adherent

to it is the peculiar proliferating

we believe, from the meniscus.

a zygapophyseal

The lower third shows

fibrous-like

destroyed.

dense,

Overlying

pannus (brackets) deriving,

Fig 18: (A) A histological coronal section of the superior posterolateral anulus fibrosis of a cervical disc from a 14year-old girl. The cleft is dissecting in tissue planes, medially to meet its counterpart from the opposite side. The upper arrow points to the cleft. There are patches of synovial-like tissue above the arrow but no evidence of other components of a true joint. The lower arrow points to the dissecting cleft proceeding medially. See text. (8) This illustration is a coronal section of the uncinate process KJ)from a 28-year-old man. The cleft or fissure (F) medial to the uncinate process shows disc fibrocartilage fibrillation (arrow) but no evidence of synovium, capsule, subchondral bone or hyaline cartilage, normal components of a true joint. We suggest that the hyaline cartilage which Luschka, and many others since, described was that of the cartilage end plate of the intervertebral disc, a normal finding noted in this illustration. (C) This illustration (54-year-old man) of a sagittal section midline of the cervical spine shows uniformly very narrow intervertebral discs, loss of most of the disc tissue and the clefting or fissures have dissected all the way across the disc (arrow). (D) This illustration (72-year-old woman) of a sagittal section of a cervical spine shows the anterior and posterior ligaments cut allowing the anatomically bisected disc to spring apart disclosing the knobbly, irregular internal surfaces with some loose fibrocartilage pieces. The arrow points to one. Presumably these could herniate. (E) This illustration of a sagittal section of a cervical spine is cut so that the internal surfaces of the completely transected intervertebral discs may be viewed (arrows). Histologically these surfaces are a mixture of hyaline cartilage, fibrocartilage, bony fragments and fibrotic nodules, usually with some loose pieces. These findings were nearly universal in varying degree in spines from patients over age 45 to 50 years.

19

ANATOMY AND PHYSIOLOGYOF THE CERVICAL SPINE

Table 1. Symptoms and Indirectly

From

and Signs Arising Directly Tissues

in the

Cervical

Spine Signs

Symptoms Pain

Falling

Headache

Tender scalp

Dizziness

Tender bones

Vertigo

Anesthesia

Paresthesia

Hyperesthesia

Fatigue

Dysesthesia

Insomnia

Atrophy

Restless arms

Hypertrophy

and legs

Hyperplasia

Cough

Weakness upper extremity

Sneeze

Asymmetry

Nausea and vomiting

Sweating (or lack of)

Diarrhea

Nystagmus

Fainting

Tender muscle

Visual disturbances

Fasciculation

Auditory disturbance

Transient hearing loss

Drop attack

Spastic gait

Arm and leg ache

Reflex changes (deep ten-

and pain Stiff neck

don, superficial and auCarotid sinus sensitivity

Pathological gait

Proprioceptive loss

Poor balance

Benign paroxysmal posi-

Muscle twitch Mood depression Tinnitus Diplopia

ACKNOWLEDGEMENTS

tonomic reflexes)

Torticollis

Speech disturbance

growth resulting in “traction” on the spinal cord and nerves and increasing downward obliquity of the roots. Discs, normal or pathological, cannot compress nerve roots. (5) Joints of Luschka are nonexistent. (6) A cleft appears in the posterolatera1 anulus fibrosus at the age of 9 to 1.5 years and dissects medially from both sides in adolescence and young adult life, bisecting the disc with a potential space, sparsely lined with synovium. (7) The anterior nerve roots are anatomically too low in the intervertebral foramen to be subject to compression. Except for zygapophyseal joint osteoarthritis, the posterior nerve roots are remarkably well protected. Radiculopathy is an uncommon clinical phenomenon, (8) There are no preganglionic autonomic nerve fibers in the cervical spine, all arising from Tl, 2, and 3 levels, first synapsing in the stellate, mid, and superior cervical autonomic ganglia. (9) Myelopathy is a far more common clinical event than radiculopathy.

tional nystagmus (BPPN) Vertebro-basilar insufficiency Sensory ataxia Physiological head extension vertigo Cervico-collie reflex Cervico-ocular reflex Vestibulo-ocular reflex

The authors wish to make the following acknowledgements with gratitude. To Mary S. Skovira for her superb, painstaking; and ever-prompt completion of all manuscript, bibliographies, and illustrative material over the past 15 years. To Professor Dallas R. Boushey, anatomist, for excellent disseetions and education of the authors as to what was known anatomy and what anatomy had not been described. To Dr Leon Sokoloff for teaching the authors how to prepare cervical spines for gross and microscopic study and the preparation of faultless pathological specimens. To Professor John Ball for educating the author in rheumatoid arthritis and osteoarthritis pathology in many long, exciting, and always amusing discussions; he also taught the method of removing cervical spine in order to derive the best and most from anatomical and pathological studies.

REFERENCES

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low back-Cumulative trauma versus single incident. Clin Orthop201:1019-1025, 1987 8. Hadler NM: Medical management of the regional musculoskeletal diseases. Philadelphia, PA, Grune and Stratton, 1984 9. Frymoyer JW, Donaghy RMP: The ruptured intervertebral disc: A 50 year follow up of the first case. J Bone Joint Surg67A:1113-1116,1985 10. Mixter WJ, Barr JS: Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med 211:210-215, 1934 11. Hadler NM: Illness in the work place; the challenge of musculoskeletal symptoms. J Hand Surg lOA:451-456, 1985 12. Hadler NM, Gilling DB, (eds): Arthritis and Society:

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The Impact of Musculoskeletal Disease (vol 3). London, England, Butterworths, 1985 13. Tondury G: The cervical spine, its development and changes during life. Act Orthop Belg 25602-626, 1959 14. Payne EE, Spillane JD: The cervical spine. An anatomical, pathologic study of 70 specimens with particular reference to cervical spondylosis. Brain 80:571-596,1957 15. Holt S, Yates PO: Cervical spondylosis and nerve root lesions. J Bone Joint Surg 48B:407-423, 1966 16. Frykholm R: Cervical nerve root compression resulting from disc degeneration and rcot sleeve fibrosis. A clinical investigation. Acta Chirurgia Stand Suppl 160:1-49, 1950 17. Hirsch C, Schajowicz F, Galante J: Structural Changes in the Cervical Spine. Copenhagen, Denmark, Munksgaard, 1967 18. Barre J: Le syndrome sympathique cervical posterieur et sa cause for frequent l’arthrite cervicale. Rev Neurol 33:1246-1254, 1926 19. Lieou YC: Syndrome sympathique cervical posterieur

BLAND AND BOUSHEY

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