Citation for published version (APA): Krajenbrink, T. G. A. (1994). The silhouette of the mandibular condyle on radiographs. s.n.

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1 University of Groningen The silhouette of the mndibulr condyle on rdiogrphs. Krjenbrink, Thierry Guy Alexis IMPORTANT NOTE: You re dvised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Plese check the document version below. Document Version Publisher's PDF, lso known s Version of record Publiction dte: 1994 Link to publiction in University of Groningen/UMCG reserch dtbse Cittion for published version (APA): Krjenbrink, T. G. A. (1994). The silhouette of the mndibulr condyle on rdiogrphs. s.n. Copyright Other thn for strictly personl use, it is not permitted to downlod or to forwrd/distribute the text or prt of it without the consent of the uthor(s) nd/or copyright holder(s), unless the work is under n open content license (like Cretive Commons). Tke-down policy If you believe tht this document breches copyright plese contct us providing detils, nd we will remove ccess to the work immeditely nd investigte your clim. Downloded from the University of Groningen/UMCG reserch dtbse (Pure): For technicl resons the number of uthors shown on this cover pge is limited to 10 mximum. Downlod dte:

2 CHAPTER ].5 Surnmry l.introduction The review of the literture indictes tht numerous imging techniques of the TMJ exist, ll with their specifrc limittions. Relibility, reproducibility nd ccurcy of conventionl rdiogrphic projections hve been investigted by severl uthors. Few studies concentrte on the shpe ofthe condyle on the rdiogrph nd on the reltionship between the gross ntomy, condylr inclintion nd the rdiogrphic projection on the type of imge. 2. Aim, objectives of the study nd problem formultion The im of the study is to ssess the relibility of the determintion of the contour of the humn condyle on infrcrnil Prm rdiogrphs nd on purnormic tomogrms (OPG) s used in the Groningen longitudinl study of the temporomndibulr joint. The specific ims of the investigtions re: i How cn the condylr silhouette on the rdiogrph be quntified? Is it possible to clssify the condylr silhouette on rdiogrphs? Ifso, how ccurte, robust nd reproducible re these clsses on the rdiogrphs? Do the infrcrnil projection nd the pnormic X-ry rdiogrphy depict the condylr silhouet te in reproducible'víiy, nd cn \rye use one clssifiction system for the different projections? Do these different rdiogrphic projections produce identicl or different condylr silhouettes on rdiogrphs? Which is the reltionship between the ntomy nd inclintion of the condyle nd its silhouette on the rdiogrph? 3. Mteril The mteril used for this study consisted of series of L52 dry mndibles nd of collection of doubly tken infrcrnil rdiogrphs lredy mde before s prt of longitudinl follow up study of 172 ptients. These ptients hve been treted t the orthodontic deprtment of the University of Groningen nd hve prticipted in the Groningen longitudinl growth study. The dry mndibles were selected from lrge collection of mcerted skulls nd mndibles present t the orthodontic deprtment of the University of Groningen. They were selected on undmged condyles nd firly intct dentition. The mndibles showed no obvious pthologicl conditions. 4. Rdiogrphic methods A review of the history, development nd technicl description bout the infrcrnil Prm II, III nd Prm IV rdiogrph nd the pnormic rdiogrph (OPG) re described in this chpter. The subsequent mjor chnges nd modifictions to the Prm projection in Groningen, bsed on the originl Prm I projection, in the period 1950 until 1990, \{rill be identifred by the Prm II, Prm III nd Prm IV projection respectively. To express the totl risk of the irrdition, used with the different projections, the men orgn dose must be used to clculte the effective dose equivlent ccording to Kuijl vn der (1992). Since no dt were vilble concerning the results of the effective dose equivlent with Prm II rdiogrphs, the results of comprble study t the University of Amsterdm (Stelt vn der et l, 1987) were used in ddition to the dt published by Kuijl vn der (1992) bout the Prm IV projection. A creful interpoltion to the Prm II rdiogrph ws mde by Kuijl vn der nd Stelt vn der (pers. comm.). It ws concluded tht the Prm IV rdiogrph genertes 4 times less rdition thn the Prm II rdiogrph. r29

3 5. The condylr silhouette In this chpter clssifiction system for the condylr silhouette in itself ws described, which, not relted to n ntomic form, ws bsed on infrcrnil rdiogrphs from the Groningen longitudinl study. Using n cette sheet on which n Y- nd X-xis re drwn, which is lid over the rdiogrph with the Y-xis prllel to the posterior border of the condylr neck nd the X-xis pssing through the brodest point, ll forms of the different condyles could be clssifred in one of the 8 clsses in fig. 6. The O-clss is chrcterized by spiky nd condylr silhouette. Bsed on clinicl experience the 0- clss ws dded to the clssiíiction. The l-clss is chrcterized by verticlly elongted silhouette, \Mith steep slope of the nterior contour. There exists greter height to width rtio. The vertex is situted left of the horizontl midpoint. The 2-clss hs n equl height to width rtio, the vertex is situted left of the horizontl midpoint. The 3-clss is brod nd reltively low. There exists height to width rtio less thn 1. The vertex is situted left of the horizontl midpoint. The 4-clss hs somewht s5rmmetricl nd mostly rounded silhouette. The contour cn be round or symmetriclly flttened with the vertex situted hlfwy the X-xis. The 5-clss is chrcterized by squred or rectngulr ppernce ofthe condylr silhouette nd hs flttened superior surfce, lmost prllel to the X-xis nd without clerly deíined vertex. The dorsl nd ventrl contours run more or less prllel to ech other. The 6-clss hs its vertex over the middle of the X-xis nd often the superior prt of the rmus nd the condylr neck re lredy curved nteriorly. It is "wve" shped. There exists height to width rtio less thn 1. The 7-clss covers ll forms which do not fit in the fore mentioned clsses, including condylr projections of strnge form. These oddly shped silhouettes re considered s seprte 7-clss. 6. Reproducibility of the clssifiction of the condylr silhouette on the infrcrnil rdiogrph of dry mndibles 298 infrcrnil rdiogrphs, mde from dry mndibles, were clssified twice in rndom order by two judges until consensus ws reched. The mesurement of the mount of greement ws clculted using Cohen's kpp sttistic. It turned out tht our clssifiction for the condylr silhouette offered reproducible method to describe the two dimensionl projection of the condyle directly from the rdiogrph. The kpp vlue of 0.74 indictes tht the results cn be considered s "good". Eighty four percent ofthe rdiogrphs lvere scored identiclly. The clinicl vlue ofthis clssifiction resides in its reltive esiness to describe the silhouette ofthe condyle on the rdiogrph, without using complex mesurements llowing esy nd exct clinicl communiction. According to the two observers, the clssifiction cn be esily mstered nd does not require long clinicl experience. It is n entity of its own nd does not describe the rel ntomic form of the condyle nor does it indicte norml, deformtions or pthology, it is just descriptive item. It is furthermore independent of size nd thus independent of rdiologicl enlrgement. 7. Robustness of the clssifiction of the condylr silhouette on the infrcrnil rdiogtph of dry mndibles Altertions of the X-ry bem inclintion or smll chnges in positioning theoreticlly my cuse chnges of the shpe of the bone projected on rdiogrph. According to the literture, there is gret tolernce with regrd to form distortion before it becomes of clinicl importnce. Thirteen mndibles, from which the right condyle represented the 1-, 2-,3-, 4-,5-, nd the 6-clss on infrcrnil rdiogrphs \Mere rdiogrphed in specilly designed construction, llowing three dimensionl djustment of the mndibles towrds the X-ry source (fig. 8). Chnges of plus or minus 3 degrees resulted ín 86Vo identicl clssifictions for the condylr silhouette. lvithin chnges of plus or minus 6 degrees, 77Vo ws clssified identicl (figs. 10 through 15). No rndomly locted different clsses showed up within the digrms indicting the robustness of the clssifiction. It hs not been possible to crete 7-clss condylr silhouette just by chnging the position of the mndible which t first showed "normlly'' shped condylr contour, not even with off-centers of 12 degrees. This mens tht the?-clss is not just strnge formed condylr silhouette becuse reltive norml condyle hppened to be incorrectly projected but n entity of its own. Chnges of 6 degrees re comprble to 130

4 displcement of the X-ry tube of pproximtely 16 mm. A trined roentgenologicl technicin my be expected to djust the X-ry tube lwys mply within this rnge. 8. Method error of the Pm II, UI, rv rdiogrphs nd of the OPG The method error of the Prm II (nd III) ws tested in two different \Mys: I using dry mndibles nd i using collection of double mde Prm II rdiogrphs from ptients s prt of the Groningen longitudinl study. The dry mndibles were rdiogrphed using specil construction (figs. 18 nd 19), llowing ccurte djustment ccording to the specifictions used for ptients. The horizontl nd verticl positioning of the mndibles both covered wide rnge indicting the lrge vriety in mndibulr form. Asymmetry between right nd leít side of the sme mndible in djustment towrds the centrl X- ry bem occurred frequently. Sixty four percent of the mndibles hd different combined horizontl nd verticl positioning of more thn plus or minus 2.5 degrees. In contrst to this vrtion, the nlysis of vrince showed more or less identicl men-positioning vlues for the different condylr silhouette groups. This mens tht the form of the mndible does not systemticlly led to specifrc condylr silhouettes. The reproducibility of the (double) Prm II rdiogrphs mde from ptients resulted in kpp vlue of 0.71 nd 887 of identicl scoring. <) Method error of the Prm IV rdiogrph: Due to the exct positioning of the mndibles, the Prm IV hs high degree of reproducibility. One dry mndible ws rdiogrphed five times; the condylr silhouettes were identiclly clssified. i Method error of the OPG: A specilly designed crniostt ws used to mke OPG's from dry mndibles, provided with metl implnts t Gonion nd the highest point of the coronoid process. The relibility of the positioning ws estblished nd the influence of cnting nd/or trnsltion of the mndibles on its condylr silhouette ws investigted. The mndibles were rdiogrphed in n individulized position simulting the sme sitution s when ptient would hve been rdiogrphed (figs. 20 nd 21). The condylr silhouette ws clssified on the OPG's. Although it sometimes looked smller or broder on the provocted tomogrms, the condylr silhouette \ils constnt in its reltive shpe. It hs been demonstrted tht there is gret tolernce ginst form distortion, which in turn is of clinicl significnce. In the posterior prts of the jws the structures my be displced t considerble distnce without producing form distortion of the condylr projection. Creful positioning of the ptient in the cephlostt consequently will result in tomogrms on which the silhouette of the condyle cn be clssifred in reproducible wy. 9. Ttre condylr silhouette on the infrcrnil rdiogrphs (dry mndibles) Rdiogrphs ccording to the Prm II nd the Prm IV projection were mde from mndibles. The rdiogrphs \Mere clssifred ccording to the 8-point clssifiction nd the frequency distribution of the condylr silhouette types ws computed. The Prm II projection hs tendency for the 3-clss (52Vo), the 4-clss (23Vo) nd the 2-clss (lovo). Tlre Prm IV projection hs tendency for the 4-clss (39Vo), the 3-clss (357o) nd the 6-clss (L4Vo). The Prm II nd the Prm IV projection did not lwys depict the condyle identiclly. This diversity is probbly due to differences in geometry between both projections. The Prm IV projection hd tendency to depict the condyles somewht lower nd rounder. 10. Ttre condylr silhouette on the OPG (dry mndibles) OPG's of!52 dry mndibles were mde using the sme specifrctions nd crniostt s described in chpter 8. The condylr silhouette ws clssified nd the frequency distribution of the different clss types ws computed. The OPG hd tendency to depict the condyles s 4- nd 6- clsses, which consisted of TLVo of the mndibles. Forty two percent of the OPG's were clssified s 4-clss nd 29Vo were clssified s 6-clss. Only two condyles were clssified s 2-clss. The 3-clss constituted reltively smll percentge of the totl. The silhouette of the condyle on the OPG ws in mjority symmetric round (4-clss) to n symmetricl ovl form, where the position of the highest point hs tendency to devite to the ventrl side on the film (6-clss). 131

5 11. The ssocition between the condylr ntomy nd the condylr silhouette A clssifrction system, which cme out of combintion of existing ntomic clssifrctions for the humn condyle, presented by Yle (1966, 1969) (fig. 22), Óberg et l. (1971)(frg. 23) nd Solberg et I. (1985)(fig.2q ws developed, using 152 dry mndibles. The condyle is divided into three res, n nterior prt nd posterior prt s seen from bove, perpendiculr to the mndibulr plne, nd superior prt ofthe condyle s seen from behind, perpendiculr to the posterior border. The superior surfce, observed from dorsl, ws clssified s: (fig.25) type 1: flt, t5pe 2: the top lterlly, type 3: the top medilly, type 4: rounded, nd type X: other shpes. The crnil spect ofthe condyle hs been divided into n nterior nd posterior surfce, seprted from ech other by the long xis ofthe condyle (frg. 26). Observed from superior, they were clssified s: type A: flt, type B: concve, type C: the most nterior c.q. posterior point lterlly, type D: the most nterior c.q. posterior point medilly, type E: convex, nd type X: other shpes. The method error ws tested by clssifying the 152 mndibles two times. There rvr/ere no mrked differences between the right nd the left side condyles regrding their frequencies. Cohens's kpp resulted in n verge kpp of 0.60 for the right condyles nd 0.72 for the left side condyles. It turned out tht the ntomic clssifrction presented is n cceptble method to describe the shpe of the humn condyle on dry skull mteril. The ntomy of the left nd right condylr surfces of the dry mndibles were clssified with the ntomic clssifrction (tbs through 11.13). Evlution of the shpe of the condyle in the study showed no consistent greement with the results reported by Yle et l. Type A (fig. 26) with flt surfce occurred in26vo in Yle's study nd in20vo for the dults srdbvo for the ge gïoup of0-19 yers in Óberg's study. In our study however, this corresponded to type 1 nd occurred in 4Vo of tine totl only. Type C (fi9. 26), the ngled type, ws represented in 72Vo in Yle's study. The inverted V- shpe described by Óberg occurred in LIVo only in dults (fig. 23). This corresponds to type 2 nd 3 of our study which occurred in 23Vo of the mndibles. From the left condyles 6lVo of t}re superior surfces were clssified 4. From the nterior surfces 37Vo ws clssified n E. Sixty two percent of the posterior surfces were clssified D. From the right condyles 73V ofthe superior surfces were clssified 4. From the nterior surfces 35Vo ws clssified n E. Eighty two percent of the posterior surfces were clssifred D. Symmetry between right nd left side occurred for the superior surfce in 101 mndibles (68Vo); for the nterior surfce in 60 mndibles (40Vo) nd for the posterior surfce in 104 mndibles (7OE). Symmetry of ll the three surfces occurred only for 4 mndibles (SVo). The ssocition between the condylr surfce nd the silhouette of the condyle on the Prm II, Prm IV nd the OPG ws investigted using contingency tbles of the condylr silhouette nd the condylr surfce shpe. Although there were smll differences between the right nd the left side for ech rdiogrphic projection, the results for the Prm II nd the Prm IV were comprble. It ws shown tht ll the different prts of the condylr surfce contributed eqully to prticulr imge on the rdiogrph. It ws not evident which prts of the condylr shpes were responsible for specific condylr silhouette type on the rdiogrph. 12. The ssocition between the condylr xis nd the condylr silhouette The condylr xis cn be mesured into horizontl inclintion or lph ngle, nd verticl inclintion or bet ngle (fig. 28). It ws found in our study tht most of the mndibles were s5rmmetric in this sense tht the condylr inclintion differed often by severl degrees between the right nd left side. The method of mesuring the condylr xis in n lph inclintion nd bet inclintion proved to be ccurte within stndrd devition of 0.8 degrees. There ws wide rnge in the condylr xil position for both the lph inclintion nd the bet inclintion. The ssocition between the condylr silhouette nd the condylr xis on the Prm II nd IV rdiogrph nd on the OPG ws investigted using nlysis of vrince. There were no signiíicnt differences between the results for the right nd left side for the three rdiogrphic projections. The lph nd bet inclintion were signifrcntly ssocited to the silhouette of the condyle on the Prm II nd Prm IV rdiogrph, nd on the OPG (with exception of the left side OPG lph ngle). Contrry to Berry's study (1960), our findings indicted tht there rvs reltionship between the condylr inclintion nd its rdiogrphic silhouette. These differences my probbly be ccounted to the low number of observtions (only 24 fighlt condyles) in Berry's study. t32

6 13. Comprison of the silhouette on the Prm II rdiogrph, the Prm fv rdiogrph nd the OPG The condylr silhouette clssified on the Prm II nd Prm IVrdiogrph nd the OPG mde from the sme dry mndibles were compred with ech other. Due to the differences in geometry it ppered tht certin shpes tended to chnge from one silhouette clss into nother (figs. 31 nd 32). It ws concluded tht ech projection cretes its specifrc condylr silhouette. The difference in the direction of the centrl X-ry bem nd the geometry of the three projections re not extreme so tht we could expect to see the sme rnge of different shpes of the condyles. Combining this with erlier results we conclude tht the Prm II rdiogrph hs the brodest rnge of condylr silhouette t5pes, followed by the Prm IV, while the OPG hs the smllest rnge. The 2-clss, nd the 3-clss occur more frequently on the Prm II rdiogrph, wheres on the Prm IV the 3-clss nd the 4-clss occur more frequently nd on the OPG the 4-clss nd the 6- clss re more frequent. The 7-clss occurs on the three types of rdiogrphs in pproximtely the sme frequency. 14. Generl discussion The im of this study is to ssess the relibility of the determintion of shpe of the humn condyle on pnormic tomogrphs (OPG) nd on the infrcrnil Prm rdiogrph, s used in the Groningen longitudinl study of the temporomndibulr joint. The rdiogrphic imge is the result of n interply of ntomicl nd geometricl vribles. Since the projection obviously reflects both, it is concluded tht the condylr silhouette contins importnt informtion. This informtion is mde ccessible in this study by mens of n 8-point clssifiction scle. This clssifiction proved to be relible nd reproducible. It hs not been the intention of this study to define cliniclly wht constitutes pthology of condyle. Mrked irregulrities or lesions in the rticulr surfce were excluded from this study. Becuse of this selection criteri of n intct condylr surfce no O-clss or l-clss were noted, this in contrst to frndings in the Groningen longitudinl study where these clsses \ilere represented very clerly. The O-clss originlly hd prevlence of less tl;'n lvo nd grdully incresed to \Vo fter 15 yers (Dibbets nd Weele vn der, 1992). This lso indictes tht the collection of dry mndibles is not representtive smple. In this study it is shown tht the condylr silhouette on the infrcrnil Prm II, III nd IV rdiogrphs nd the OPG cn be clssified in reproducible wy. The Prm II rdiogrph displys the brodest rnge on the 8 point clssifiction scle. In ddition it hs been shown tht this rdiogrph is not very susceptible to rtefcts. The combintion of these properties mke the Prm II rdiogrph vluble clinicl tool, which might be expected to detect subtle differences more redily thn both other projections. Becuse this projection ws widely used l5 to 2O yers go most references re from tht period. However, the Prm IV projection genertes considerbly less rdition thn the Prm II projection with respectively totl H"g of 0.03 msv. versus Heff rnging between 0.11 msv. nd 0.12 msv. for the Prm II. For this reson the Prm II projection should not be used nymore for newly to strt project. The OPG displys smller rnge of condylr silhouette types. This is due to the fct tht the medil nd lterl pole re sometimes not included in the X-ry slice which is cut through the condyle. The condylr silhouette on the OPG is the depiction of the contour of this slice. The results of this study lso indicte tht there is signifrcnt ssocition between the ntomy of the condyle nd its condylr silhouette on the rdiogrph. This is only the cse for the condylr xis, wheres the surfce of the condyle does not significntly contribute to the condylr silhouette. An explntion for this lys in the fct tht mostly the centrl X-ry does not hit the condyle to be rdiogrphed long its long-xis. The medil nd lterl pole lrgely contribute to the speciíic condylr silhouette. Further reserch in temporomndibulr joint dysfunction studies or in methodologicl studies on rdiogrphic projections hs to be done using the 8-point clssifiction system on rdiogrphs nd combining these results with other dt such s pin, clicking, growth type etc. nd to estblish possible clinicl relevnce. If necessry the clssifiction cn be djusted to pthologicl forms (Boering, 1966; Leeuw de, 1994). The rdiogrphs mde within the fmework of the Groningen longitudinl study re no\m redy to be further nlyzed with the help of the results of this study. 133