Anatomy and pathology of the aging spine

European Journal of Radiology 27 (1998) 181–195

Anatomy and pathology of the aging spine1

Andreas Prescher

Institut fur Anatomie, Uni6ersitatsklinikum der RWTH Aachen, 52057 Aachen, Germany

Received 12 November 1997; accepted 14 November 1997

Abstract

The vertebral column is a complicated anatomical structure which is composed of the intervertebral discs and the vertebrae.Both components develop special degenerative changes and morphologic features during life. This paper first reviews theanatomical fundamentals and then describes the morphological features of the aging intervertebral disc and the subsequentosseous changes of the vertebral bodies and the zygapophyseal joints. The aging intervertebral disc is characterised by processeswhich are labeled as intervertebral chondrosis and intervertebral osteochondrosis. Often these processes are combined with typicaldislocations of intervertebral disc tissue in an anterior or dorsolateral direction. The well known Schmorl’s nodules must also bementioned in this context. Furthermore calcification and ossification of the intervertebral disc tissue can take place. More severeprocesses lead to osseous changes of the vertebral bodies. In particular, an osteophytosis of the vertebral bodies can beestablished. These sturdy osteophytes are able to stiffen the vertebral column. Furthermore the arthrotic changes of thezygapophyseal joints are delineated in this paper. The special appearances of these changes are discussed according to the differentand specialised regions of the vertebral column. The advanced degenerative changes of the zygapophyseal and uncovertebral jointsof the cervical spine are of essential clinical interest because the compression of the vertebral artery or the narrowing of theintervertebral foramina by these processes may cause severe neurological symptoms. The arthrotic changes of the medialatlantoaxial joint, which lead to the crowned odontoid, and the pseudospondylolisthesis (so called M. Junghanns) of the lumbarspine must also be mentioned. It is the aim of this paper, not only to explain and review the degenerative changes, but to illustratethe anatomy and pathology of the aging spine on the basis of macerated osseous specimens in order to make radiologicalinvestigations and pictures more understandable and clear. © 1998 Elsevier Science Ireland Ltd. All rights reserved.

Keywords: Degenerative changes; Spine; Spondylosis; Intervertebral disc

1. General anatomical fundamentals

The spine represents a movable column composed of24 presacral vertebrae, disci intervertebrales and liga-ments. Reflecting the increasing loads, the vertebraeand intervertebral discs increase in a harmonic orderfrom the cranial end in the caudal direction.

For the changes in the structure and composition ofthe spine with increasing age, the anatomy of theintervertebral discs is of prime importance. An interver-

tebral disc consists basically of an external fibrous ring,the anulus fibrosus, and a jelly-like center, the nucleuspulposus. The anulus fibrosus can be subdivided intoan outer and an inner zone, which show differenthistological structures. The outer zone is structured intoconcentric lamellae of tight, collagenous fibers (Fig. 1a),which in the inner zone are followed by fibrous-carti-laginous tissue. Without a distinct borderline, that tis-sue gradually exhibits a transition into the nucleuspulposus (Fig. 1a). The fibers in the outer zone areprimarily type I collagen fibers, while the fibers of theinner zone are mostly collagen fibers of type II. In theindividual lamellae of the outer zone, which are sequen-tially structured similar to the layers of an onion, thefibers are arranged crossing each other clockwise and

1 Dedicated to Professor Dr med D. Graf von Keyserlingk on theoccasion of his 60th birthday.

0720-048X/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved.PII S0720-048X(97)00165-4

A. Prescher / European Journal of Radiology 27 (1998) 181–195182

Fig. 1. (a) Horizontal section of a normal intervertebral disc, illustrat-ing the concentric laminated anulus fibrosus and the eccentric locatednucleus pulposus with a brown degeneration forming. (b) Normalosseous vertebral endplate exhibiting a porous surface structure and asmooth ossified vertebral rim. A little step can be seen between thesetwo areas (36 years, female). (c) Structural changes of the osseousvertebral endplate and the ossified vertebral rim due to osteochondro-sis. Many little bony excrescences and irregularities are present (79years, female).

counterclockwise in helical turns, connecting theossified vertebral rims of two adjacent vertebrae. Inthese places the collagenous fibers penetrate into thebony structure as Sharpey’s fibers. This special configu-ration of the fibers is particularly suitable for compen-sation of shear forces. The fibers additionally take careof the forces transmitted from the nucleus pulposus asa response on central as well as eccentric loads.

The nucleus pulposus, located eccentrically at thetransition between the central and the posterior part ofthe intervertebral disc [1] contains glycosaminoglycanes,which during youth and middle age comprise particu-larly chondroitine-4-sulphate, chondroitine-6-sulphateand keratane-sulphate. However, in persons of ad-vanced age, dermatane-sulphate is mainly found. Thehigh proportion of glycosaminoglycanes and the lowcontent of fibers result in a considerable capacity toretain water. Accordingly, the nucleus pulposus has theproperties of a water-filled cushion.

The intervertebral discs exhibit a typical angioarchi-tecture which varies during the various periods of life[2]. In foeti with a crown-rump length of 7 cm, bloodvessels can first be demonstrated between the lamellaeof the anulus fibrosus. However, these vessels neverreach the nucleus pulposus. Following the second yearof life, these blood vessels degenerate. Accordingly, themoistness and hydration of the intervertebral discs de-creases and the tendency towards changes characteristicof advanced age is initiated. In healthy persons, thesystem of vessels of the vertebral body is completelyseparated from the corresponding system of the inter-vertebral disc by the cartilage endplates.

In adults, lateral fissures penetrating into the anulusfibrosus and possibly subdividing the entire disc intotwo halves, occur regularly in the area of the interverte-bral discs of the cervical part of the spine. Thesefissures were first described in 1858 by Hubert Luschka[3] and designated as hemidiarthroses laterales. In 1893,Trolard [4] called them articulationes uncovertebrales,an expression presently still in use. The designations‘Luschka-joints’ or ‘neurocentral joints’ are also fre-quently used. These fissures are not present in infantsand children of low age [2,5,6] and they can first beobserved in children at an age of 9 years [7]. Thisauthor associates the development of these fissures withthe rising of the uncinate processes. Recently, the ap-pearance of such a fissure was reported in a 1-month-old infant [8]. As far as this observation is concerned,the presence of a true uncovertebral joint remains ques-tionable however, as the fissures did not extend into theanulus fibrosus. These fissures form in perfectly healthytissue of the intervertebral discs, and cannot be com-pared with the formation of fissures due to chondrosisintervertebralis. After the formation of the fissures inthe anulus fibrosus, a joint-pseudocapsule develops, andcloses the fissure laterally. Within this capsule, vascular-

A. Prescher / European Journal of Radiology 27 (1998) 181–195 183

Fig. 2. (a) Vertebra C6 and C7 completely fused due to synostosingosteochondrosis (88 years, male). (b) Macerated cervical vertebralcolumn. Between C5 and C6 an isolated, heterotopic ossification(arrow) lies in the region of the former anulus fibrosus (76 years,male).

in shape, particularly in postmenopausal women in thecourse of osteoporosis of the skeleton. As these changesrepresent an entity of their own, they are not discussedin more detail in this paper.

The chronic degenerative changes of the spine aresummarized as spondylopathia deformans (earlier syn-onyms: spondylitis deformans, polyspondylitis mar-ginalis osteophytica or spondylchondrosis). As far as theconditions for development of spondylopathia defor-mans are concerned, it was convincingly argued that adegeneration of the intervertebral discs with a decreaseof their elasticity marks the onset of the disorder [10,11].The subsequent inability to distribute loads equally in alldirections later causes the typical modifications at theinterface between the bones and the associated cartilagein the spine and the minor joints of the spine (zygapo-physeal joints).

The heading spondylopathia deformans can be sub-classified, depending on the location of the degenerativechanges. In cases of spondylosis deformans the vertebralbodies are affected while the term spondylarthrosisdeformans describes degenerative processes at the minorjoints of the spine.

2.2. Chondrosis inter6ertebralis

As the age of a person increases, the quantity of waterpresent in the nucleus pulposus decreases and conse-quently the swelling by that water and the cushioningeffect previously present are reduced. In section, thenucleus pulposus no longer bulges out, but has theappearance of a dry, crumbling mass. The color haslikewise changed from a glassy greyish-blue to a yellow-ish color with a tendency towards brown. This changein color is due to deposition of a brown coloring agentbelonging to the class of melanines [12,13] and resultedin the designation of this change as ‘browndegeneration’.

Additionally gaps and systems of fissures develop inthe intervertebral discs, which not are not only presentin the nucleus pulposus, but partly radiate also into theanulus fibrosus. Occasionally these fissures appear inroentgenograms brighter than the surrounding tissue, afeature designated as ‘vacuum phenomenon’. Nitrogenwas demonstrated to be present in this system of fissures[14]. All these changes, collectively described as ‘chon-drosis intervertebralis’, result in considerable reductionof the elasticity of the intervertebral disc, while theheight of the space occupied by the intervertebral discdecreases only to a minor extent.

The variable anatomical manifestation of ‘chondrosisintervertebralis’ as a gradual aging process and a de-crease in water-content, is termed primary chondrosisintervertebralis. In this context, chronic overloadingcertainly represents an important factor. Identical mor-phological changes, which are however consequences of

ized synovial folds have been observed. The details ofthe formation of these fissures are presently still largelyunknown. The development of the cervical lordosisresults in a change of the configuration and the magni-tude of the loads acting on the cervical spine. Thereforethe sections subsequently loaded are mostly located inthe region of C3 through C5. In that region, the lateralfissures in the intervertebral discs also first appear. Thestrong shear forces acting on the intervertebral discs,particularly during rotational movements and lateralinclinations, additionally increase the loads present inthis region. The formation of these fissures may there-fore be assumed to be the consequence of large loads [9].

2. Degenerative disc disease

2.1. General features

During the human lifespan, the spinal column isexposed to many continuously recurring loads, whichresult in almost consequential changes in the morpho-logical conditions. These changes can be described asdegenerative chronic processes on the intervertebraldiscs, the zygapophyseal joints and the ligaments. Addi-tionally the aging spine undergoes considerable changes


pathological changes outside the intervertebral discs,e.g. following spondylolysis or abnormal deformationof the spine, are designated as secondary chondrosisintervertebralis [15].

If chondrosis intervertebralis has started, the degen-erative destruction of the intervertebral disc continuesand experiences a transition into osteochondrosis inter-vertebralis. This stage is characterized by participationof the cartilage endplates and gradual sclerosis of theadjacent spongiosa of the vertebral body.

2.3. Osteochondrosis inter6ertebralis

Osteochondrosis intervertebralis has to be consideredas a process changing the structure of the intervertebraldisc into a condition prone to crumbling, accompaniedby a considerable reduction in the height of the spaceoccupied by the intervertebral disc. The material of theformer intervertebral disc presents as dry, crumbly,grayish-white or brown-dark tissue between the verte-bral bodies and frequently contains a cavity resultingfrom the process of decomposition. Within such acavity, sequestra may be present as detached particles.The process in the direction of crumbling may spreadinto the inner layers of the anulus fibrosus, with theouter fibrous systems remaining, and appearing con-vexly arched towards the outside [16]. The cartilageendplates of the vertebral bodies are likewise affectedby the degenerative changes or even destroyed com-pletely. Frequently numerous irregular proliferations ofcartilage and ossifications within small foci are locatedon the endplates of the vertebral bodies (Fig. 1b,c). Theadjacent spongiosa of the vertebral body shows reactivesclerotization since the function of the disc equalizingand distributing pressures and shocks has largely de-creased. The processes described may basically developin all intervertebral discs, but take place predominantlyin the two lowest lumbar and less frequently in thelower cervical intervertebral discs. Osteochondrosis in-tervertebralis may materialize in two special manifesta-tions. In one, the brittle bony structure of the endplatesof the vertebral bodies and the sclerotized spongiosamay break like the two wings of a door, resulting inerosive osteochondrosis [17]. In the other manifestation,blood vessels grow into the intervertebral discs andtrigger an ossification, which can result in a completeossification of the intervertebral disc (synostosing os-teochondrosis) (Fig. 2a).

2.4. Calcification and ossifications

In 1858, Luschka [3] mentioned small foci of calcifi-cation in the area of the nucleus pulposus. However,Schmorl was the first to investigate this manifestationin more detail and to classify it into primary andsecondary forms [15]. According to his opinion, the

primary calcification is the consequence of degenerativeprocesses, while secondary calcification is the result ofearlier inflammation (e.g. tuberculosis). Another clas-sification separates chronically degenerative manifesta-tions from inflammatory-rheumatoid calcification [18].

Chronic degenerative calcification is predominantlylocated in the central thoracic and the upper lumbarvertebrae and may be localized in the nucleus pulposusas well as in the anulus fibrosus. In the jelly-like part ofthe nucleus pulposus it appears as small, crumbly, whitespots, mostly associated with the system of fissures ofthe nucleus pulposus.

In the anulus fibrosus the calcification appears asirregular particles in small foci, often associated withtears and necroses; 71% of the calcification is located inthe anulus fibrosus and 6.5% in the nucleus pulposus[19].

In this context, the deposits of bony structures withinthe intervertebral disc, manifesting as a consequence ofdegenerative changes, merit attention. These ossifica-tions may manifest themselves in two different ways:First as a consequence of the healing of a chondrosis or

Fig. 3. (a) Osseous top-plate of a thoracic vertebra exhibiting anirregular cavity resulting from a cartilaginous nodule (Schmorl’snodule) (72 years, male). (b) Frontal section through a cavity result-ing from a cartilaginous nodule (Schmorl’s nodule). The arrow pointsto the sclerotising osseous reaction (85 years, male).


Fig. 4. (a) Macerated cervical vertebral column with moderate, caudally orientated osteophytes localised in the midline from C2 to C5 (91 years,female). (b) Macerated cervical vertebral column with large osteophytes, blocking the last two cervical and the first thoracic vertebral bodies (91years, female).

an osteochondrosis intervertebralis. In the course of theprocess of healing, blood vessels sprout from the verte-bral bodies through defects in the cartilage endplatesinto the degeneratively damaged intervertebral disc andinduce the formation of bony structures. In most cases,these structures result in the blockade of the respectivesegment of motion. This course of the healing processmay be described as healing and amending of thedegenerative processes by rigidization.

The second manifestation is present in the anteriorparts of the anulus fibrosus. Here, blood vessels maysprout into radial or concentric fissures between thefibers and trigger formation of bony structures. Asmall, spongious bony body results, located between thebony margins of two adjacent vertebral bodies (Fig.2b). These small ossicles should not be confused withosteophytes, isolated osteophytes or intercalate bonesdue to spondylosis deformans. These ossifications ofthe anulus fibrosus definitely do not represent a distur-bance in the ossification of the vertebral rim as wasassumed in literature [20].

3. Dislocations of intervertebral tissues


In the aftermath of chronic degenerative changes inthe intervertebral disc, a dislocation of tissues of theintervertebral disc (of the anulus fibrosus as well as ofthe nucleus pulposus) may occur. Such a dislocationmay take place in two major modes: as a protrusion or

as a prolapse. Bulging of an intervertebral disc in adorsal, lateral or ventral direction is called a protrusion.In most cases, a protrusion derives from a fissure in theinner zone of the anulus fibrosus. The tissue of thenucleus pulposus pushes outwards and bulges the fibersof the outer zone outwards while no tissue of thenucleus pulposus will prolapse or escape. If the fibers ofthe outer zone tear however, the pressurized tissue ofthe nucleus pulposus is pushed outwards and a prolapseof the intervertebral disc results. Depending on thetopology, such a dislocation of tissue may be directedcranially or caudally or in the dorsal, dorsolateral orventral direction.

3.2. Schmorl’s nodules

Schmorl’s nodules of cartilage represent a dislocationof tissue of the nucleus pulposus through the cartilageendplate into the vertebral body. Subsequently prolifer-ation of cartilage and reactive ossification may developin the vicinity of the tissue dislocated from the nucleuspulposus. This ossification encloses the dislocated tissuelike a shell and segregates it from the spongiosa of thevertebral body (Fig. 3a,b and Fig. 4).

The structure, which can now be demonstrated radio-logically, represents the typical cartilaginous nodule(Schmorl’s nodule) [21]. For compensation of a largerSchmorl’s nodule, in juveniles an increased growthopposite to the nodule may develop on the cartilageendplate on the adjacent vertebral body and results inan osseous projection resembling an exostosis (Edgren-Vaino’s sign). If no cartilaginous or bony barrier is


established, more and more material of the nucleuspulposus can enter into the vertebral body, resulting inan extensive process, which should be termed a nucleuspulposus prolapse or an intraspongious prolapse of thenucleus pulposus [21]. Unfortunately, the actualnomenclature reflects the conditions in an abbreviatedform only. Sometimes no distinction is therefore madebetween the cartilaginous nodule and the intraspon-gious prolapse of the nucleus pulposus and both termsare used synonymously.

Schmorl’s nodules are seen more frequently in menthan women, a condition attributed to larger spinalloads in men [15]. Frequently the nodules are located inthe lower thoracic and in the lumbar region of thespine. In most cases they are established in the center ofthe vertebral body, since in that region the cartilageendplate is thin because of the earlier passage of thechorda dorsalis. The mechanical loads damage thislocus minoris resistentiae until it finally yields and thepressurized tissue of the nucleus pulposus penetratesinto the spongiosa of the vertebral body. If the pro-lapsed tissue of the nucleus pulposus necrotizes, the

Fig. 6. (a) Anterolateral view of the macerated cervical vertebralcolumn (92 years, female). The intervertebral foramen between C3/4is narrowed by an osteophyte of the zygapophyseal joint. (b) Antero-lateral view of the macerated cervical column (65 years, male). Theintervertebral foramen between C3/4 is severe encroached by anosteophyte of the zygapophyseal joint and an osteophytary structureof the uncinate process.

Fig. 5. (a) Normally configured cervical vertebra, exhibiting thetypical morphology of the uncinate process (arrow). It is noticeablethat the lateral parts of the uncinate process are located medial to thetransverse foramen, whereas the dorsal parts lie anteromedial to theintervertebral nerve sulcus (arrowhead) (36 years, female). (b) Cervi-cal vertebra affected with severe degenerative changes. The uncinateprocess (arrow) is bent outwards and narrows the intervertebral nervesulcus. Furthermore degenerative changes of the minor joint facetscan be seen (88 years, male).

cartilaginous nodule may become ‘resorbed’. If this rare‘healing process’ does not take place, Schmorl’s nodulesmay continue to exist throughout the remaining life ofthe carrier.

3.3. Lateral or dorsolateral dislocation

In Schmorl’s autoptical series of investigations, adislocation of tissue of the nucleus pulposus in thedorsal or dorsolateral direction takes place in 15.2% of


spines and shows a slight preference for the female sex[15]. These prolapses are located in 95% of the casesbetween L4 and L5, or between L5 and S1 [22].

In the cervical region such prolapses occur predomi-nantly in the segments of motion C5/6 and C6/7 [23].The dorsal prolapse is located between the dorsal sideof the intervertebral disc and the posterior longitudinalligament, in most cases slightly lateral to the ligament.In the prolapsed tissue fine spots of calcification can bedemonstrated, which cannot be identified radiologicallyhowever. Depending on the shape and morphology ofthe dorsal or dorsolateral prolapse of the intervertebraldisc, various configurations can be distinguished: (1)Dangling prolapse—in this case, tissue of the nucleuspulposus issues from a fissure in the anulus fibrosus,but may return into the initial place in the course ofparticular motions. (2) Incarcerated prolapse—the pro-lapsed tissue is trapped in the fissure of the anulusfibrosus in such a fashion that a return is impossible.This configuration of a prolapse represents an earlystage of a sequestrated prolapse, in the course of whichthe prolapsed material becomes detached and may sub-sequently be dislocated cranially or caudally. Such casesare also described as ‘migrating prolapses’. If seques-trated material penetrates the dura mater and floatssubsequently in the liquor, an intradural prolapse ex-ists, which only happens extremely rarely. In cases of adorsolateral prolapse, the displaced tissue is located inthe intervertebral foramen and causes a compression ofthe spinal nerves. In the cervical region a compressionof the vertebral artery may also occur. The topographi-cal location of the spinal nerves relative to the interver-tebral disc is decisive for the efficiency of themechanism of compression. In the cervical and lumbarregion of the spine the intervertebral disc is located atthe same level as the spinal nerve in the intervertebralforamen. For this reason a compression of the nervemay occur easily in this region. In the thoracic region,the spinal nerve is located cranially of the intervertebraldisc behind the vertebral body. Accordingly, the nervewill rarely be contacted by the prolapse and the symp-toms of nerve compression are seldom observed.

3.4. Ventral dislocation

Ventral dislocation of intervertebral disc tissue mayoccur in two different ways: The anteriorly prolapsedtissue rarely penetrates ventrally between the frontalside of the spine and the anterior longitudinal ligamentcranially or caudally. Such cases are therefore of onlyminor importance in practice [15].

Schmorl [21] drew the physician’s attention to asecond form of ventral dislocation of intravertebral disctissue. At the inner edge of the ossified vertebral rim astepwise transition exists from the smooth rim into theporous endplate of the vertebral body (Fig. 1b) and

forms a locus minor resistentiae, into which tissue ofthe nucleus pulposus may penetrate. If this should bethe case, the prolapsed tissue works its way in anoblique direction outwards through the bone, finallydetaching the ventral edge of the vertebral body as atriangular piece of bone [21]. The prolapsed tissuesubsequently becomes crushed by the now abnormallymobile detached piece of bone and on the correspond-ing areas of the bones a fibrous-cartilaginous coatingdevelops as some kind of pseudoarthrosis. These mani-festations are mainly observed at the upper edges of thelumbar vertebrae and at the upper edge of the sacralbone. Based on pathological investigations an incidenceof 5% was quoted [21]. In the course of a series ofradiological investigations an incidence of 1% wasfound [24]. The difference was explained by the impos-sibility of identifying all pieces of detached bone radio-logically. Following the same principle ofmaterialization, lateral or infrequently even dorsalpieces of bone may break off the edges of the vertebralbodies [25]. The triangular bony elements resultingfrom these detachments from the edges of the vertebraewere formerly considered as persistent epiphyses of thevertebral bodies [20,26], an opinion which has beendisproved by extensive investigations [21,24,27–29].The anterior detachment of bone from the edge of thevertebral body has to be distinguished unambiguouslyfrom pieces of bone torn from the edge of the vertebratraumatically [30]. Degenerative detachments of theanterior edge of the vertebral bodies are only of minorclinical importance [24].

4. Spondylosis deformans


In cases of spondylosis deformans, bony osteophytesand excrescences develop in the region of the vertebralbodies. These manifestations represent chronic degener-ative changes, which are predominantly located in thecervical, lower thoracic and lumbar region of the spine.The incidence increases with advanced age. InSchmorl’s series of 4253 specimens of the spine col-lected in the course of autopsies, at an age of 49 years,60% of female and 80% of male spines showed os-teophytes of the vertebral bodies. At an age of 79 years,both sexes were equally affected in approximately 95%of cases [15]. The results of a large-scale investigation ofspondylosis deformans in the cervical region of thespine were published by Aufdermaur (1960) [23] whoalso added comments on the interpretation of the statis-tically determined incidences during various periods oflife. A connection between the manifestation and theextent of this disorder and the occupational loads andstresses seems to be questionable and is discussed con-


troversially in the literature [31,32]. Concerning theinitiation of spondylosis, two different pathogeneticconcepts are currently discussed: the first hypothesis isbased on the extensive investigations by Schmorl andhas been discussed exhaustively [15]. In his opinion, theformation of fissures in the outer zone of the anulusfibrosus (the ‘Randleistenanulus’ according to Schmorl)is the cause of subsequent changes. The anatomicalconditions at the ‘Randleistenanulus’ are characterizedby the prominent fibers of Sharpey, which extend intothe bony structure of the ossified vertebral rim of thevertebral body. If this fixation is reduced or torn as aconsequence of the formation of a fissure, or evensuspended, the intervertebral disc maintains less con-nection with the adjacent vertebral bodies and mayengage in unphysiological movements. These circum-stances may cause excessive loading of the anteriorlongitudinal ligament and result in the formation ofbony peaks at the insertions of the ligament. If thenucleus pulposus has not yet been degenerated, pressureexerted against the anterior longitudinal ligamentcauses additional pulling forces on the points of liga-ment-insertion. This concept explains the observationof particularly large osteophytes predominantly in per-sons in which the nucleus pulposus has not degeneratedand the height of the spaces occupied by the interverte-bral discs has dropped only to a minor extent. Thisinterpretation of the processes involved clearly confirmsthe earlier opinions [10,11] of the cause for spondylosisdeformans to be located in the intervertebral discs andnot in the vertebral bodies.

A second concept addressing the development ofspondylosis deformans has been presented by Collins[33], who also confirms the degeneration of the interver-tebral disc to mark the early stage of the disorder andbelieves the special anatomical conditions in the regionof the anterior longitudinal ligament to be responsiblefor the development of the osteophytes. He claims thisligament retains tissue from the intervertebral disc ex-panding as a consequence of the formation of fissuresand the detachment of the ‘Randleistenanulus’. Later-ally, where the anterior longitudinal ligament ends com-paratively sharply and abruptly, changing to a weakmembrane of connective tissue, such a dislocation oftissue is not stopped, but results in detachment of theperiost from the vertebral body. Consequently, pe-riosteal development of bone starts, resulting in theformation of osteophytes.

A unilateral partisanship for the first or second con-cept does not appear to be advisable, since the typicalmanifestations of spondylosis deformans very likelydevelop both ways, in a combined action [30].

Evidence supporting the concept of Collins [33] is theossifications histologically frequently to be found belowthe anterior longitudinal ligament and showing no con-nection or at most a secondary extension to the anterior

longitudinal ligament only. Details observed at thecervical region of the spine, such as the osteophyteslocated ventrally (Fig. 4a) in most cases also favor theconcept of Collins. As the anterior longitudinal liga-ment of the cervical region of the spine is much weakerthan in the thoracic or lumbar region, pressing back ofthe tissue of the intervertebral disc will be much lesseffective. This condition may be advantageous for theformation of ventral osteophytes, as this has beenobserved.

4.2. Spondylosis cer6icalis and spondylosisunco6ertebralis

The degenerative changes in the cervical region of thespine have to be subdivided into the actual spondylosiscervicalis and the spondylosis uncovertebralis.

The capacity for motion is most pronounced in theregion of the segment of motion C5/C6 and continu-ously decreases cranially. This anatomical conditioncorrelates with the observation that spondylosis defor-mans manifests mostly in the region of the segmentsC5/C6 and C6/C7 and seldom occurs cranially [23].

Fig. 7. (a) Cervical vertebra exhibiting a typical, dorsal locatedaccessory transverse foramen on both sides (arrows) (72 years, male).(b) Cervical vertebra exhibiting a medial located, pseudoaccessorytransverse foramen (arrow) in an osteophytary addition of the verte-bral body (92 years, female).


Fig. 8. (a) Macerated thoracic vertebral column (88 years, male) exhibiting strong, fused osteophytes predominantly on the right side. (b) Frontalsection through two thoracic vertebral bodies with marked osteophytes on the right side. It is clearly seen that the osteophytes are locatedsomewhat below or above the vertebral limbus (72 years, male).

Spondylosis deformans in the cervical region is char-acterized by osteophytes primarily developed in theventral direction (Fig. 4a), because of the weakly devel-oped anterior longitudinal ligament. Osteophytes devel-oped in the dorsal direction also occur but are oftenonly of minor size. The configurations of the os-teophytes are very diversified, and they can merge,blocking the respective segment of motion (Fig. 4b).Osteophytes never start at the edges of a vertebralbody, but only slightly below [23]. They are composedof lamellar bone structure and contain a more or lesscompact spongiosa, the marrow spaces of which areconnected to the marrow spaces of the vertebral bodies.

Osteophytes on the uncinate processes characterizethe spondylosis uncovertebralis [30]. The variousconfigurations of spondylosis uncovertebralis can alsobe observed in the region C3–C7. Distinct manifesta-tions are however found predominantly on the lowersegments C5/C6 and C6/C7 [30,34]. The regular unci-nate processes are positioned higher and steeper in thecranial region of the cervical spine than in the caudalregion. Additionally, in most cases they are dorsolat-eral, i.e. where they assume a topographical connectionto the intervertebral canal, and with a flatter shape thanin the lateral region, where they are located next to thetransverse foramen (Fig. 5a). A flat uncinate process isa preferred place for the development of osteophytes[30]. Fully developed osteophytosis however results inbrimming of the uncinate process into a shape similarto a console. Such a console may have a height of 2–3

mm and accordingly almost define a horizontal plateauon which the next vertebral body above rests with acorresponding lateral trough.

In cases in which the lateral brimming of the unci-nate processes is located in the dorsal region, a narrow-ing of the intervertebral foramen results (Fig. 5b),causing a corresponding compression of the spinalnerve. A simultaneous spondylarthrosis will worsen thesituation, since in such a configuration, osteophytesalso grow from the dorsal direction into the interverte-bral foramen and the spinal nerve will partly be trappedby these projections like the jaws of pliers (Fig. 6b).

If the console-shaped brimming also takes place inthe opposite region of the uncinate process at theadjacent higher vertebral body, such an arthrotic os-teophyte can project into the transverse foramen. Aperforation and formation of a hole may develop in theosteophyte, simulating a partitioned transverse foramen(Fig. 7b). The true partitioned transverse foramen is aninsignificant anatomical variety, observed frequently,particularly in the caudal cervical vertebrae for thepassage of veins. This accessory transverse foramen isregularly located dorsal of the transverse foramen (Fig.7a) while the pseudoaccessory transverse foramen islocated medial. Furthermore it is closed by connectivetissue or fibrous cartilage. The osteophytes developed atthe anterior section of the uncinate processes maycompress the vertebral artery from the medial direction.Such a configuration has quite some significance, aschiropractical manipulations may result in dissection of


Fig. 9. (a) Thoracic vertebra (Th9) exhibiting a typical dorsal osteophyte (arrow). This osteophyte is shaped like the flame of a candle and arisessomewhat below the ossified vertebral limbus (76 years, male). (b) Dorsal aspect of two thoracic vertebral bodies (Th11–12) exhibiting osseouschanges due to a dorsal cartilaginous nodule (Schmorl’s nodule). The arrow points to an irregular cavity, surrounded by an irregular, prominent,osseous margin. The ossified vertebral rim is destroyed (68 years, male).

the vertebral artery on the osteophytes of the unci-nate processes with serious consequences for theblood supply to the vertebro-basilar region [35].

4.3. Spondylosis thoracalis

Inspection of a macerated preparation will be moreinstructive for the characteristic details of pronouncedspondylosis thoracalis than any description (Fig. 8a).The osteophytes always arise slightly below or abovethe ossified rim of the vertebral body (Fig. 8b). Theymay contact each other, interlock mutually andfinally fuse together. They are frequently located be-low the anterior longitudinal ligament and ossificationof this ligament will be a secondary phenomenononly. The large thoracic osteophytes will cause ablockage of the respective segments of motion (Fig.8a).

The formation of osteophytes in the region of thethoracic part of the spine occurs predominantly ven-trolaterally, but also dorsally (Fig. 9a). However,these dorsal osteophytes are small in size, shaped likethe flame of a candle and are mostly located parame-dian. The low extent of the dorsal osteophytosis isbased on the anatomical conditions determined by theposterior longitudinal ligament. This ligament insertsprimarily at the rear of the intervertebral disc andwith only a few fibers at the vertebral body. Thevertebral body is not available for insertion of a liga-ment across a large area, as it shows the basivertebralforamen offering passage for voluminous veins. The

typical dorsal osteophytes (Fig. 9a) must be differenti-ated from calcification and ossification formingaround the ‘posterior Schmorl’s nodules’. These bonyobjects are located in an irregular pattern at the backedge of the vertebral body and are frequently associ-ated with depressions harboring these nodules (Fig.9b).

4.4. Spondylosis lumbalis

The manifestations of spondylosis lumbalis are sim-ilar to the configurations in spondylosis thoracalis,except for their substantially larger size, which mayreach grotesque dimensions, and the higher incidenceof isolated bony elements located as intercalate bonesbetween the osteophytes. In cases of pronounced de-crease in the height of the intervertebral discs, thespinous processes of adjacent vertebra may contacteach other. Between the grinding bony parts sclerot-ization, grinding-facets and also pseudoarthroses maydevelop (Fig. 10a–c). These manifestations are knownas osteoarthrosis interspinosa [36], kissing spines orBaastrup’s disease.

As a peculiarity, a helmet-shaped sclerotization ofthe spongiosa on top of an intervertebral disc maydevelop, in most cases in the two lower lumbar verte-bral bodies. This manifestation, in most cases seenagainst a generally degenerative background, is desig-nated spondylosis hemisphaerica or Dihlmann’s syn-drome [37,38].


5. Spondylarthrosis


The term ‘spondylarthrosis’ describes degenerativechanges in the zygapophyseal joints. Unfortunately, insome careless generalizations this terminology is alsoused in the current literature for changes in the inter-vertebral discs and vertebral bodies. This practiceshould be discontinued to maintain a clearly definednomenclature without ambiguities. A continuously in-creasing incidence of degenerative changes in the minorjoints of the vertebrae, particularly in the cervical andlumbar region of the spine, is seen in patients of morethan 30 years of age, as these joints are substantiallyloaded by the large range and frequency of motion [39].

Changes in the intervertebral discs (chondrosis inter-vertebralis and osteochondrosis intervertebralis) result-ing in a decrease in the height of the intervertebral disc,are assumed to be responsible for the pathogenesis ofspondylarthrosis. Such a decrease in height results inloosening of the segment of motion and in unphysiolog-

Fig. 11. (a) Anterior aspect of the atlas (89 years, male). A semilunar-shaped arthrotic coulisse (arrows) is located on the anterior arch. (b)Posterolateral aspect of a ‘crowned odontoid’ (87 years, male). Thearrow points to the typical osteophytary addition, which exhibitscysts and trabeculae at its dorsal side.

Fig. 10. (a) Lateral aspect of two lumbar vertebra (L2–3), exhibitingtypical ‘kissing spines’ (86 years, female). (b) Cranial aspect of thesurface of the spinous process of L4. Irregular osteophytary addi-tions, grinding facets, cysts and eburnisations can easily be seen. (c)Caudal aspect of the surface of the spinous process of L3. Corre-sponding changes, as described in (b) are visible.

ical loading of the minor joints of the vertebral column.The decrease in height also causes a caudal dislocationof the inferior articular processes and stressing of thecapsules of the joints. Additionally a dorsal dislocationof a vertebra (retrolisthesis) may develop. All threefactors mentioned contribute to the degenerativechanges in the zygapophyseal joints. In this contexthowever, the simple pathogenic concept ‘decrease in theheight of the intervertebral discs and subsequent irregu-lar loading of the minor joints of the vertebral column’only partially represents the whole truth, for time andagain, cases with manifest osteochondrosis interverte-bralis are seen in which no spondylarthrosis of theassociated minor joints of the vertebrae is present at all.On the other hand, cases with considerable degenera-tive changes of the zygapophyseal joints without simul-taneous damage to the intervertebral discs are known.Within these inconsistencies, the observation must bementioned that the spondylarthrosis develops most fre-quently in the segment Th 4/5 [39]. However, thissegment of motion exhibits the lowest degree of mobil-ity of the entire spine. Other, unknown factors, musttherefore be considered contributing to the pathologicalconcept just presented. The morphological manifesta-tions of spondylarthrosis do not differ from the mani-festations in cases of arthrosis deformans of the largejoints. Progredient damage of the cartilage, showingfissures, grinding-facets and eburnizations have beenobserved. The subchondral lamella also show strongsclerotization and cysts may develop. Furthermore typi-


cally osteophytes may be formed at the joint facets. Themeniscoid folds of the minor joints of the vertebralcolumn are much less delicate and show fibrozation andhyalinization. Frequently detritus, consisting of frag-ments detached from the cartilage, rests in the joints.The articular capsule shows ribbon-like fibrozationscausing isolation of the joint from the surroundingstructures [30]. Since spondylarthrosis exhibits specialpeculiarities in the various parts of the spine resultingfrom the anatomical conditions typical for the respec-tive section of the spine, the characteristic details arepresented separately below.

5.2. Spondylarthrosis cer6icalis and arthrosis of themedian atlantoaxial joint

In the cervical region of the spine some peculiaritiesresult from the special morphology of the two uppercervical vertebrae. In this context, the expression‘spondylarthrosis cervicalis’ not only covers the degen-erative processes in the minor joints of the vertebrae,but also the degenerative processes of the atlantooccip-ital joints, of the median atlantoaxial joint and the

Fig. 13. (a) Inferior articular processes of a lumbar vertebra (L4)showing severe degenerative changes. Not only are osteophytaryadditions, grinding facets, cysts and eburnisations visible, but also agrotesque deformation is present (82 years, female). (b) Superiorarticular processes of L5 corresponding to the inferior articularprocesses shown in (a). A grotesque deformation and all signs ofdegenerative changes document a severe spondylarthrosis lumbalis.

Fig. 12. (a) Cranial aspect of a cervical vertebra, showing normallyfigured articular facets (36 years, female). (b) Cranial aspect of acervical vertebra exhibiting serious degenerative changes of the articu-lar facets. Osteophytary additions, cysts, grinding facets and enlarge-ment of the facets are present and document a severespondylarthrosis cervicalis (88 years, male).

lateral atlantoaxial joints. Only in the median at-lantoaxial joint do the degenerative changes represent amajor disorder however, resulting in extensive andcharacteristic morphological changes. According to ra-diological investigations, persons above 61 years of ageshow degenerative alterations of this joint in 88% of thecases [40]. The morphological changes in the medianatlantoaxial joint are on the one hand characterized bythe typical joint-changes seen in degenerative disorders.On the other hand, manifestations specific for thislocation are also seen. At the upper edge of the anteriorarch of the atlas, bony excrescences are established in asemilunar shape, resembling a coulisse (Fig. 11a), whichmanifest on a.p. roentgenograms as a peridental aure-ole. These bony appositions may isolate themselves,and subsequently form independent accessory elements[41], located between the anterior rim of the occipitalforamen and the anterior arch of the atlas. This‘coulisse of the atlas’ may also extend substantially inthe cranial direction, resulting in physical contact withthe anterior border of the occipital foramen. The


coulisse of the atlas resulting from arthrosis can alsoget bent in the dorsal direction and be placed over theapex dentis like a roof. This configuration was termed a‘Processus opercularis atlantis’ [42]. Recently a pictureof a typical specimen was published [41]. The degenera-tive changes in the median atlantoaxial joint causetypical manifestations on the dens axis itself. Here theanterior articular facet is partly dislocated in the cranialdirection by rolling action, resulting in a bony additionin the shape of a coulisse at the anterior edge of theapex dentis (Fig. 11b). In the literature, this configura-tion is designated as ‘crowned odontoid process’,‘crowned dens’, ‘peridental aureole’ or ‘arthroticcoulisse of the dens’ [43–46]. This coulisse of the densis characterized by the smooth structure of the frontalarea (possibly forming an articulation with a coulisse ofthe atlas) and by numerous cysts on the back area andstructures similar to trabeculae (Fig. 11b). Parts maybreak away from the coulisse and turn into independentbony elements [43] which in the course of differentialdiagnosis must not be mixed up with isolated ossicles ofphylogenetic origin.

The typically degenerative changes of the ‘crownedodontoid’ and in the coulisse of the atlas should not be

mixed up with calcination (tendinitis calcarea) or ossifi-cation of the ligaments. Spondylarthrosis cervicalis alsomanifests at the zygapophyseal joints of the cervicalregion of the spine, resulting in a grotesque deforma-tion and enlarging of the joint surfaces due to os-teophytary additions (Fig. 12a,b). As the anterior partsof the zygapophyseal joints approach the intervertebralforamen directly from the rear, such osteophytes resultin considerable reduction of this narrow passage (Fig.6a) and in compression of the spinal nerve. In caseswith simultaneous spondylosis uncovertebralis, thecompression of the spinal nerve, which, figurativelyspeaking, is caught by the osteophytes partly ‘betweenthe jaws of pliers’ (Fig. 6b), represents a particularlyserious condition. Narrowing of the intervertebral fora-men is caused most frequently solely by spondylosisuncovertebralis, less frequently by a combination ofspondylosis uncovertebralis and spondylarthrosis, andleast frequently solely by spondylarthrosis [23,34].

5.3. Spondylarthrosis thoracalis

Spondylarthrosis thoracalis shows no significant de-viations from the common arthrosis deformans. Thedescension of the inferior articular processes, initiatingformation of bulges similar to consoles in the arcusvertebrae of the next vertebra below and thus limitingthe degree of descension, is noteworthy however. If thespaces occupied by the intervertebral discs experiencefurther reduction in height, the vertebral bodies tiltforwards to some extent and increased kyphozationtakes place. Because even in cases of pronouncedspondylarthrosis thoracalis, major osteophytes willrarely grow into the intervertebral foramen, compres-sion of the spinal nerves is only observed infrequently.Other conditions reducing the incidence of compressionof the nerves by prolapses of intervertebral discs from aventral direction are the protected cranial location ofthe spinal nerves and the comparatively large dimen-sions of the intervertebral foramina.

5.4. Spondylarthrosis lumbalis

The degenerative changes developing in the course ofthis disorder are distinctly serious and result ingrotesque deformation of the zygapophyseal joints (Fig.13a,b). All manifestations of arthrosis deformans, suchas cysts, porozation, grinding-facets, eburnizations andjoint-deformations may simultaneously be seen in agreat variety of combinations. In cases of advancedspondylarthrosis lumbalis, a vertebra may slide for-wards (Fig. 14), predominantly in females. In mostcases the vertebra L4 is involved. This anterior disloca-tion takes place while the arch of the vertebra is intact.No relationship with spondylolisthesis exists therefore.Junghanns [47,48] noticed this phenomenon and termed

Fig. 14. Median-sagittal section of the lumbar vertebral column (82years, female). The arrow points to the typical cavity of a cartilagi-nous nodule (Schmorl’s nodule). Furthermore a remarkable anteriordislocation of L4 can be seen and represents a typical pseudospondy-lolisthesis (M. Junghanns).


it ‘Pseudospondylolisthesis.’ Cases of pseudospondy-lolisthesis show pronounced spondylarthrosis of theminor joints of the affected section of motion, which isusually less severe in the adjacent joints. Based on thisobservation, a hypoplastic or excessively flat develop-ment of the articular facets between L4 and L5 trigger-ing this anterior sliding dislocation has therefore beenassumed. The resulting unphysiologic distribution ofthe loads then causes the development of substantialspondylarthrosis in this segment of motion. This pseu-dospondylolisthesis (M. Junghanns) has however to bestrictly set apart from spondylolisthesis in cases ofspondylolysis, mostly affecting L5 and predominantlyoccurring in men. At the present time, no final rating ofthe role of the inherent factors in the manifestation ofpseudospondylolisthesis is possible however [49,50].

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