the stages of disc degeneration as revealed by discograms
Transcription
the stages of disc degeneration as revealed by discograms
THE STAGES OF DISC DEGENERATION BY A. M. One hundred radio-opaque Examination and thirty-nine fluid and dye. of the sections The discs REVEALED DISCOGRAMS ADAMS, From AS P. DOLAN, Poh’technic from W. C. ofCentra! cadaveric HUTTON London lumbar spines were injected with a mixture of Discograms were taken and the discs were then sectioned in the sagittal plane. revealed that injected fluid did not at first mix with the disc matrix but pushed it aside to form pools of injected fluid. The location of these pools, and hence the appearance of a discogram, depended on the stage of degeneration of the disc. It is concluded that useful clinical information can be obtained from discograms. The usefulness ofdiscography established. characteristic 1964; has Certain types of patients Fraser et a!. 1983) and asymptomatic volunteers Unfortunately, the not been of “abnormal” with low back are satisfactorily discogram are pain (Feinberg relatively uncommon (Holt 1968). fact that abnormal in between 8 and 60 years, who had been fully mobile prior to death. Three of the spines were tested “fresh”. The others were stored at 20 C in sealed plastic bags for up to four weeks, until required for testing. They were then - thawed Method. discograms in their bags at room temperature One hundred and thirty-nine for I 2 hours. of the discs were sometimes occur in asymptomatic people has led to discography being dismissed as being an unreliable diagnostic test (Holt 1968). However, it is likely that discograms reveal a great deal about the state of degeneration injected with a mixture of dye and radio-opaque fluid. Seventeen discs were not injected and these were used as controls. For the injection. a straight 21-gauge needle on a ofan intervertebral disc; after all, they are patterns which represent the distribution of radio-opaque fluid injected into a disc, and this distribution must depend on the physical properties of the nucleus and on the presence of S ml syringe was inserted the disc; up to 2 ml of blue dye, was injected. inserted between thumb fissures in the ing degenerative graph of applied injection pressure) was the minimum toms ignoring evidence changes if this evidence can reliable. The present investigation demonstrate what happens be shown and (and does annulus. The difficulties changes in the disc not justify to determine hence the degeneration. rent vogue papain. about whether discogram) This work for injecting often whether concerning such to be precise and was carried out in order to injected into a disc or not the fluid distribution is a reliable guide to disc first the disc in relatsymp- to fluid was partly intervertebral without involved to patients’ prompted discs obtaining is degenerate by the curwith chymo- direct evidence Cadaveric removed at material. routine AND taken plane Sixty-two necropsies lumbar from M. A. Adams, PhD, Research Fellow P. Dolan, PhD, Research Fellow W. C. Hutton, DSc, Professor of Biomechanics School of Engineering and Science, Polytechnic 115 New Cavendish Street, London WIM 8JS, Requests for reprints 1986 British 0301-620X/86/1035 36 shouldbesentto Editorial $2.00 Society in the sagittal plane (and sometimes in the frontal also) and the spine was frozen at - 20#{176}C. While still frozen, the spines were cut up to obtain and spines subjects, of Central England. W. C. Hutton. Joint Surgery ___________________________ London, each below with about it. Thirty-two 5 mm of the of vertebral injected body discs above along with the I 7 control discs were then cut into 3-mm-thick slices in the sagittal plane, using a hacksaw with a thin blade. The slices were wiped with damp cotton-wool to remove cutting examined Professor of Bone and were aged to the disc slowly and smoothly until no more could be injected or until dye was observed to be leaking from a fissure in the disc; this procedure took up to 20 seconds. About 5 to 10 minutes after injection, discograms of the spine were or not. METHODS force (which can easily be converted to against time. The pressure recorded required to inject any fluid into the disc; it was zeroed by measuring the pressure required expel the viscous Conray plus dye mixture from needle into the air. The fluid was injected into the the discs, MATERIAL anteriorly along the midline of Conray 480, containing aniline A strain-gauged load cell was and syringe in order to obtain a were debris, under preserved Several then thawed, photographed a binocular microscope. Some in formalin for histological injection tests were performed pieces of nucleus and annulus so that the methods could be observed directly under and slices investigation. on isolated fluid the transport binocular microscope. THE JOURNAL OF BONE AND JOINT SURGERY THE STAGES OF DISC showed that DEGENERATION RESULTS Examination of the disc slices the fluid did not at first mix with the disc matrix it aside, creating pools of fluid. After this bution, the fluid slowly mixed with bination of fluid flow (caused the hydrophilic proteoglycans) mixing processes were too 5 to 10-minute interval discogram being taken. mixing took place during and this was revealed rounding discs. slowness characteristic only on the much effect slices were washed gel ofthe in ofthe slices mixing under away, in the matrix. from This meant Types was non- that the discograms of the injected in the annulus. In this way the to the degree ofdisc degeneration. a but sur- young, processes shapes seen on initial distribution in the the injection and the a certain amount of and slicing of the disc the depended fluid into The location of these pools was determined of fibrosis of the nucleus and the presence fissures related by the of any discogram was of the radio-opaque of the discograms and five of these discogram stages in disc which Table I. The they represent Discogram shadow. degeneration. types Close the disc slices showed types corresponded In is summarised five were distinguished on the features in the shape and in Table ofdiscogram and type the comparison that only to distinct following classifica- I, the discogram the stages Stage ofdisc ofdisc types degeneration degeneration ofdiscogram. or centrally These annulus specimens is followed by a descripusually associated with Then the stage ofdegeneration located. discs showed no signs is of degeneration. was white and unfissured the nucleus was a soft and white The in non-injected amorphous that contained no fissures or fibrous lumps (Fig. The injected fluid was contained within the forming a continuous system of pools surrounding blobs matrix of matrix tended to gel I b). nucleus, small (Fig. Ic). Mixing of the fluid with the occur rather quickly in this type of nucleus washing. so that little of the The fluid distribution location of the needle-tip dye within could be removed by was not affected by the the nucleus. However, if the needle-tip was placed in the annulus, the fluid could only be injected very slowly and under high pressure; it would tend to flow around between the lamellae and not pass of discogram density type each definition of degeneration used to explain the distribution of injected fluid, and hence the appearance of the discogram. 1. Cottonball. The radio-opaque shadow appears to be contained within the nucleus and is of uniform density (Fig. Ia, level L3-4). The shape is not necessarily round nucleus pressure Various types of discogram basis ofconsistently identifiable tion, to have pressure of Both these pools could be washed be seen as a slight halo noticeable degenerated The pools. degree slow proteoglycan-water particularly by a com- by the swelling and diffusion. between However, freezing if the tap: the fluid in the some blue dye could the matrix that pushed distri- 37 BY DISCOGRAMS are defined and tion of the stage injected but initial AS REVEALED into the nucleus. Injection into required very little pressure, associated with these discs be due to the deform and reluctance make of the room isolated pieces so the high (see Table annulus and of injection II) must end-plate to for the fluid. 2. Lobular. The radio-opaque shadow appears to be contamed within the nucleus and has a lobular appearance, being denser near the end-plates and less dense or absent in the centre (Fig. burger or horseshoe. superficial appearance lobular nature Occasionally These starting 2a). Typical shapes The lobes can of a cottonball is revealed by the resemble overlap (Fig. a ham- to give 2b) but variation in density. only one lobe is filled on injection. were typical mature discs with the to coalesce into fibrous lumps the the which nucleus were separ- I . Cottonball No signs of degeneration. Soft white amorphous nucleus ated from the annulus and cartilage end-plates (and occasionally from each other) by softer material. Usually, these areas of softer material contained clefts or lines of fracture (Fig. 2c). The lamellae of the annulus 2. Lobular Mature starting fibrous were distinct, and sometimes bulged into the nucleus, but they were not disrupted by fissures. The injected fluid stayed in the nucleus and formed 3. Irregular Degenerated 4. Fissured ;iii:: - - 5. Ruptured disc with nucleus to coalesce into lumps disc with pools lumps. nucleus and inner annulus cartilage fissures and clefts in the slowly Degenerated disc with radial fissure leading to the outer edge of the annulus fluid has to escape. Disc a completeCan be radialin fissure that allows injected any state of degeneration in the softer material surrounding These pools were particuarly large end-plates with 68-B, No. I, JANUARY 1986 (Figs matrix 2d and 2e). so a considerable The fibrous to the fluid amount mixed of it could be removed by washing. could depend on the needle nucleus: fluid injected very near The fluid distribution placement within the one end-plate may not reach end-plate the clefts near the opposite and the disco- gram would then show only half of the hamburger. Very little fluid could be injected into isolated pieces of annulus, but injection into pieces of nucleus was easy, unless the needle-tip VOL. the soft the adjacent was in the centre ofa fibrous lump. M. A. ADAMS, 38 3. Irregular. shape The and (Fig. radio-opaque appears 3a). These discs to shadow penetrate showed distinct with a fibrous nucleus and nucleus and inner annulus. has into the signs P. DOLAN, an irregular inner annulus There was little mixing with the matrix (Fig. jection into isolated pieces of disc was generally all locations except the outer annulus. shadow haps trast (Fig. limit The pictures tile should t;1() read he pages. . . ‘ of degeneration. between nucleus and annulus. The injected fluid formed pools around the fibrous lumps of nucleus and in the fissures in the inner annulus. Fissured. The acros.c C. HUTTON clefts and small fissures in the There was poor differentia- tion 4. W. discogram shows the 3b). Ineasy in radio-opaque Figure l-Cottonhabl In a young non-degenerated disc the nucleus consists of soft blobs that can be easily separated (Fig. lb). When dyed radio-opaque solution is injected into this type of disc it forms a continuous system of pools in the nucleus (Fig. lc) and yields a cottonball discogram (Fig. la, level L3-4). w M-14 L3-S1 reaching to the outer edge of the annulus (perbeyond the edge of the vertebral body), but no conmaterial escapes from the disc through the annulus 4a, at levels L I 2 and L3- 4). There is a definite (usually I to 3 ml) to the volume offluid that can be Fig. Ia injected. and These often discs were discoloured usually degenerated, and narrowed. There one or more radial fissures usually led to the posterior the disc. The fissure occurred being were fibrous always in the annulus and these or posterolateral border of either in the mid-plane of . the often disc or near one end-plate. bulged beyond the edge The injected fluid usually The posterior of the vertebral formed large annulus bodies. pools in the Fig. F-37 L4-5 2b annulus and nucleus. It flowed down the radial fissure, but was prevented from escaping by either the outermost lamellae of the annulus or the posterior longitudinal ligament (Fig. 4b). Injection into isolated pieces ofdisc was generally easy 5. Ruptured. in all locations. The discogram extending to the outer from the disc entirely. contrast material Fig, I a; and levels escape on the volume edge There shows of the might material annulus and escaping be a large quantity of within the disc space (see level L5-Sl, L2- 3 and L5-Sl , Fig. 4a) or most may injection offluid (L4 5, Fig. 4a). There that can be injected. These discs come in all stages there is always a complete radial posterior annulus. The injected fluid sometimes the fissure. and annulus contrast In other cases as well (Figs from the disc could posterior longitudinal is no limit Fig. 3a to of degeneration, fissure, usually but in the flowed down straight Figure 3-Irregular When dyed radio-opaque solution is injected into a mildly degenerated disc it forms pools in the nucleus and tills clefts in the inner annulus (Fig. 3b). The resulting discogram has an irregular appearance (Fig. 3a). it formed poois in the nucleus 5a and Sb). The escape route be obstructed ligament. and diverted by the Occasionally, dye was observed in the vertebral bodies on the discogram. revealing a fracture of the vertebral end-plate. This happened in five discs, all of which were in the upper three lumbar levels. Two were Type 2 discs, while three were Type 5, but none of these are included in Table II. We could have classified these as a sixth type but we decided against it since this classification is based on the disc rather than the end-plate. The histological sections showed that the clefts Fig. THE 4a JOURNAL OF BONE AND JOINT SURGERY THE STAGES OF DISC DEGENERATION AS REVEALED 39 BY DISCOGRAMS A Figure 2-Lobular In a mature disc, the nucleus consists of fibrous lumps separated by softer material, often containing clefts (Fig. 2c). When dyed radio-opaque solution is injected into this type ofdisc it forms pools in the softer material and these can be particularly large near the end-plates (Figs 2d, 2e). The resulting discogram has a lobular appearance (Fig. 2a) though lobes may overlap (Fig. 2b). Fig. Fig. 4b Figure 4-Fissured When dyed radio-opaque solution is injected into a fissured disc, it flows down the fissure but is prevented from escaping by the outermost annulus or the posterior longitudinal ligament (Fig. 4b). The resulting discogram shows a radio-opaque shadow up to or beyond the edge of the vertebral body as shown at levels L I -2 and L3 -4 (Fig. 4a). VOL. 68-B, No. I, JANUARY 986 Sb Figure 5-Ruptured Figure 5a-When dyed radio-opaque solution was injected into this disc, it flowed down the fissure, but was diverted by the posterior longitudinal ligament and escaped from a posterolateral corner. The discogram is shown in Figure 4a, level L2-3. Figure Sb-In this young disc, the injected solution formed a large pool in the nucleus before escaping down the fissure. As in Figure 5a, the escaping solution was diverted by the posterior longitudinal ligament. The discogram is shown in Figure Ia, level L5-Sl. 40 M. A. ADAMS, P. DOLAN, observed in and around the nucleus (Figs 2c, 2d and 3b) were not artefacts caused by injection on cutting; their smooth edges indicated a natural origin. W. C. HUTTON ing of the vertebral end-plates disc height on injection (Brinckmann therefore At the end of the experiment, each discognam was assessed by the authors (acting together) and assigned to one of the five types. At the time of assessment, the age deformation tance rises of the end-plate until eventually and sex of each spine was known, and it was also known if any dye had been observed to leak from the disc during injection. The object of this exercise was to indicate the age range, spinal level, injection pressure and injection (Galante volume normally associated with each type of discogram. This could possibly aid the interpretation of difficult discograms in life. Table II shows the frequency of each type of discogram. Fissured. and ruptured discs are most common in old spines but also occur in some young ones. Older require discs accept a greater volume a lower injection pressure. Table II must be viewed tion as it was compiled even, we repeated our of injected with by only classification some fluid and statistical three observers. after a period cauHowof six months had elapsed in order to see how reproducible it was. One hundred and seventeen (87%) of the discograms were assigned to the same type, and of the 1 7 that were not. 9 involved the distinction between Types 2 and 3. young discs fluid high The results has shown it is injected are consistent happens to an aqueous an intervertebral disc. with the observations of Erlacher (1952) who described similar patterns of injected fluid distribution in cadaveric discs, but did not relate the patterns to stages in disc degeneration. Let us now consider how the disc makes space for the injected solution. This is achieved by outward bulgTable II. Details of the discs to discogram type and the injection -- --- type 2 3 Discogram I-Number ofdiscs each age range: Number at each Injection (kgcm Injected (ml) in of discs level: pressuret 2) volumet * 5 discs had are not given t Measurements discs fractures data ------ tabulated according 5 Total number ofdiscs 4 increase is stiffer this is probably injection were in The pressure resistance to and this resisis accepted. In and less why they pressure. recorded extensible accept less Occasionally in older discs although these may be due to injection into a fibrous part of the nucleus. If more and more fluid is forced into a disc under ever-increasing pressure, the result is a fractured end-plate Herbert and and Barks not a ruptured annulus (Jayson, 1973). The relative weakness and deformability of the end-plate compared explains why the largest poo1s are located neath the end-plates and not between to the annulus directly undernucleus and annulus. ent Our from position pressures tone, large ferent injection pressures those measured (Quinnell, should be were not significantly differin living people in the prone Stockdale slightly and higher, Willis 1983). In vivo because of muscle but this effect has apparently variation in injection pressure ages and stages of degeneration. Discograms what into an overall and annulus, no more fluid annulus and and require greater injection pressures DISCUSSION This experiment solution when the 1967), and and Horst 1985). depends upon the are determined been masked between discs by the fluid pools, and hence by the The first four types of discogram initial by the of dif- pattern degeneration of the that we have called of disc. cot- tonball, lobular, irregular and fissured represent successive stages in disc degeneration. The fifth type denotes a rupture, and this can occur in a disc at any stage of degeneration. Viewing a good indication tion. The soft the four stages ofthe natural history amorphous nucleus in succession gives ofdisc degeneraof a young disc becomes less homogeneous with age. At an early age it has regions of greater and lesser cohesion (Fig. lb) that gradually become more exaggerated and coalesce (Fig. 2e). By about several discrete material which the fifth decade the nucleus fibrous bodies surrounded may contain large fissures 6 3 3 3 33 the nucleus 0 14 6 12 15 47 cated, fissures and clefts appear in the inner annulus (Fig. 3b) and develop into radial fissures (Fig. 4b). A complete 19 48 15 22 30 134* LI -2 L2-3 L3-4 L4-5 L5-Sl 2 3 6 5 3 10 15 12 7 4 3 1 3 5 3 0 2 3 6 11 2 4 3 9 12 17 25 27 32 33 Mean SD n 2.41 1.16 15 1.96 1.02 39 1.84 0.54 7 1.20 0.63 16 1.36 0.73 25 Mean SD n 0.62 0.40 17 0.71 0.32 42 1.20 0.56 9 1.54 0.36 5 >2.0 <30 31-40 4 1-50 51-60 18 Total in the of pressure ? vertebral and volume end-plates, were more fibrous and dessi- radial fissure (rupture) can be the final stage of degeneration (Fig. 5a). However, ruptures can also appear in young non-degenerated discs (Fig. Sb) where they are probably related to disc injury (Adams and Hutton 1982) or fatigue damage (Adams account of disc degeneration tural features in the nucleus vious work (for example, We 28 made to become and Hutton 1985). This naturally focuses on strucbut it is consistent with preVernon-Roberts and Pine 1977). so discogram only continues consists of by softer (Fig. 2c). As on results the later material the same tnibution this have shown that discognams on reveal the state ofdegenenation be said ofdiscograms on living of injected experiment fluid because THE must exactly JOURNAL be the same the same OF BONE cadavenic ofthe discs. Can people? The dis- AND in vivo patterns JOINT as in of dis- SURGERY THE cograms on living 1969). preting image have been described people (for example, However, discograms is reduced; in numerous investigations by Gnesham and Miller approach could lead and the needle track; discograms in life than the majority of patients’ in to confusion and Types 4 us now consider the usefulness of this so give of the Types 1 , 2 and 3 discs are not prolapsed, degenerate and it is difficult to see how others. severely could be responsible for symptoms. Type 4 may or they well be symptomatic since an incomplete radial fissure can represent an intermediate stage in the gradual prolapse of the disc (Adams and Hutton 1985). When this is the case, there will probably be nuclear pulp in the fissure causing the outermost annulus and adhering posterior longitudinal ligament to bulge outwards. This is often injection (Fraser et a!. 1983). Type 5 discs may also be symptomatic since a disc rupture could indicate a recent no extrusion of nuclear the rupture may have and may after fifth the nucleus has and sixth decades probably symptoms longer why disc in people people (Gresham the Type 5 discs a!. 1983). that disc probably leak; In and give certainly coalesced (Adams ruptures aged pulp (Fernstrom occurred long ago it is unlikely into fibrous and Hutton are under to do so lumps 1985). in the This is often associated with 35, but not in older Miller 1969) and why only 21% rise to pain on injection (Fraser summary, the available Types I , 2 and 3 are is, and Type 5 may evidence not symptomatic, be, especially of et suggests Type 4 in a young the five types ofdiscogram may be useful in predicting the likely effect of chemonucleolysis on that disc. Chymopapain seemingly binds rapidly to the disc matrix and breaks down proteoglycans. Its action should VOL. 68-B. No. I, JANUARY 1986 the potential 5 disc with symptomatic) to be both effective a soft pulpy nucleus rupture (Fig. 5b and and and a Ia). How- ever, the whole question of the usefulness of chymopapain in relieving symptoms at all is in some dispute. Conclusions. When an aqueous solution is injected into a initial distribution the matrix Useful discograms. and hence the we fissured with the of injected in pools, the fluid of degeneration have called represent disc matrix, fluid. After slowly by the processes ofdiffusion clinical information can The location the appearance stage types but this mixes with and fluid flow. be obtained from of the pools of injected fluid, of a discogram, depends on of the disc. cottonball, successive The lobular, stages discogram irregular in disc and degeneration. This work is supported by a grant from the Arthritis and Rheumatism Council. Our many discograms were taken by Mrs A. Pettitt and Mr D. Horsfield of the X-ray Department at the Royal National Orthopaedic Hospital: we are most grateful to them. We also thank Michael Sullivan, FRCS, who contributed to our discussions on the best classification of the different types of discogram. REFERENCES Adams MA, Hutton WC. Prolapsed injury. Spine l982;7: 184-91. Adams MA, Hutton WC. Gradual intervertebral disc disc: prolapse. Spine a hyperfiexion 1985 ; in press. Brinckmann P, Horst M. The influence of vertebral body fracture, intradiscal injection, and partial discectomy on the radial bulge and height ofhuman lumbar discs. Spine 1985; 10: 138-45. Erlacher PR. Nucleography. J Bone Joint Feinberg SB. The place of diskography cases. AJR l964;92:127581. Fernstrom discs. Fraser U. A discographical Acta Chir Scand study 1960;Suppl Surg [Br] 204-10. as based of ruptured lumbar 258: 1-60. lumbar EP [Am] Jr. The question of lumbar 1968;5O-A : 720-6. MIV, phology Herbert CM, and bursting Quinnell RC, Stockdale within normal discs HR, Willis in the lumbar Vernon-Roberts B, Pine discs of the lumbar 1977:16: 13-21. CJ. Degenerative spine and their fibrosus. spine by diskography of the herniated disk J Bone Dis Joint Surg discs: nuclear 1973:32:308- mor15. DS. Observations spine. Spine 1983:8: changes sequelae. 2320 in degener- annulus discography. Barks JS. Intervertebral pressures. Ann Rheurn on intervertebral J, McCall 1W, Park WM, O’Brien JP. Discography ating disc disease. Orthop Trans l983:7(3):466. Gresham JL, Miller R. Evaluation of the lumbar and its use in selection of proper treatment syndrome. C/in Orthop 1969:67:29-41. Holt 1952;34-B: in radiology Galante JO. Tensile properties of the human Ada Orthop Scand I967;Suppl 100. Jayson person. Finally, in the disc, If this is the suggested by the appearance of the discogram. Type 4 discs are common in patients with back pain and are the type most often associated with symptomatic pain reproduced by prolapse with 1960). However, chymopapain has useful is the Type disc it does not at first mix pushes it aside to form pools informa- tion. Holt (1968) showed that asymptomatic volunteers can have abnormal discograms. Evidently there is no simple correspondence between pathological changes in the disc and patients’ symptoms. Nevertheless, certain discogram types are much more likely to be symptomatic than even on its initial distribution of fibrosis of the nucleus. should be the least efficiently digested (Fig. 4b). Unfortunately, Type 4 discs are most likely to be symptomatic and Type I are least likely. The category of disc where (possibly disc. Let 41 BY DISCOGRAMS case then Type I discs should be most effectively digested because they have a non-fibrous nucleus that mixes intimately with any injected fluid (Fig. Ic) and Type 4 discs this experiment. discograms clearly types described above and on the state of degeneration AS REVEALED therefore depend and on the degree to distinguish since there is no when injected fluid is escaping reasons it will be more difficult to show one of the five accurate information injected DEGENERATION is more scope for error in intertaken in vivo: the contrast of the the position of the needle-tip is less cer- be difficult confirmation For these categorise Nevertheless, OF DISC there tam; the posterolateral between disc fissures and 5 may direct visual from a disc. STAGES of pressures 166-9. in the intervertebral Rheumatol Rehabil