Roentgenographic findings of the lumbosacral spine in preemployment examinations of lumbermen with special reference to spondylolisthesis.

and j. heaLth 1 (1975) 40-44. The X-ray findings of the lumbar spine in the preemployment examination of 807 lumbermen are presented. From the applicants 11.4 % were rejected because of roent genological and/or clinical low back abnormalities. The youngest age group showed a high frequency of spondylolisthesis (8 %). The possible role of heavy work in adolescence in the etiology of spondylolisthesis is discussed.

true spina bifida, collapsed 0.1' wedged vertebra,evidence of old fractures of a vertebr.al body or a neural arch, prior bRok surgery (laminectomy or fusion), aTticulation of .a transverse process with the sacrum, mark·ed scoliosis with rotation or ,Ji;:Ylph:osis of the lumbar spine, and maDk-ed na'rrowing ,of ,an interv,ertebral joint space and advanced -osteoarthritis if in excess of aver:ag,e usual fLndings in rellation to age. As it appears, thepe i.s no unanim,ous agre.em,ent aJb:out the predetermining va'1idity of the findings, and X~ray ex,amlin.ations in preemplo.yment examinahons 'halVe even been regarded ,as cO'mpletely use-Iess (14).
On the whole I the occupation of lumberman con6ists 'of extT-em·ely heavy physical labor, and ,jilting .Jogs and bending with a chain 'saw puts stress 'on the back and the-Iimbs pairticularJy. In an investigation conducted in Sweden (13) 39 % of the lumbermen studied .reported having received ,medica.l treatment from a doctor or in the hospital because of back pain; 5 % of .the younger (25 to 34 years) and 14 % of the 01der {45 to 54 years) reported suffering fflom recurrent fits of lumbago

40
Back troubles are ,an essential 'cause of lost w-orking time and disability, espe-ciaNy in physliCially dema'l1Jding ;occup.ations with stress ,on the ba-ck. Advance identification o:f risk g,roups -has been attempted by inspecting ,roentgenogtr.a,ms of the lumbosaoral spine in preemiployment exa;minations. OhO:O,9ing predktahle and v,aHd criteria of rejection has presented dif-ficUilties, since in the 1umhosa'cral iregiQn there occur grea't numbers 'Of roentgeno--logicwl abno'Y,mahties no,t ,causing clinical sympto:ms, while ba;ck pain and insufficiency ,may :occur in persons with perfectl y normal X-ray finding,s. The Industrial Medical Assooia,tton's (IMA's) Ad Hoc Committee on Low Bad' X-rays (3) and other auVhms (5,6,7,12,19,20) m'e of the opinion that at ,least the folLowing X-ray findings predict back troubles and Lor,m gr-ounds of rejecti-on for applicants in heavy occupations: spondylolisthesis, transitional lumbosacral vertebra w~th pseudoarthrosis, Roentgenographic findings of th.e lu.mbosacral spine in preemployment examinations of lumbermen with special reference to spondylolisthesis Altogether 130 applicants (16.1 "/0) were rejected. 'Dhe number of those .rejected because of their tback totaled 92, .0,1' 11.4 {l/o, of the total. Table 1 Us!s the results according ·toage groups and grounds for r,ejection. Back diseases ,caused the rejection of 70.7 0J0 of the total number of reje-ctedappHcants. Of -the other diseases causing rejection, the camm-onest were car,diov.ascular diseases, traumatic vasospastic disease (Ray-n-aud's phenomenon of occupational .origin), osteoarthritis of the 41 RESULTS continu{lUsly. In addition many had worked on f.arms ,and in Itransportation and loading jobs. Those having been in mines or factories a.t some time were rare, The common factor wlas that they had always been doing physically healvy work, most of them even from the age of 14 to 16 years. The age distribution of the study subjects is presen ted in table 1.
The procedure of the study was as follows: The applioan.ts filled out a standardized questionnaire in reference to their earlier significant diseases and present symptoms l including inquiries .about their backs. All the applicants were submitted to a detailed clinical exa'mination involving among other things posture, muscle spasms ,and tenderness of back, its flexibility when bending, and symptoms of possible root compression. The X-r,ays of the lumbosacral spine were taken on 20 X 40 em filrrn in antero-posterior and lateral directions; ,also a later.al oone picture of the lumbos.a'cral junction was taiken When Ithe subject was standing. Ei@hty p.er cent of the pictures were interpreted by the same nadLologist. A diagnosis ocr: spondylolisthesis was made only when 1Jhe'r,e was a distinct slipping of the vertebrllJl body.
Rejection ,of the applicants was 'made o.n the basis -of ea,rIier anamnestic informahonl ,their olinical state, ·and the statement of the radiologist considered together l but in ca'ses of -spondylolisthesi:s rej.ection was made even without dinical symp.toms. The criteria for rejection on ,the basis of the X-Day findings alone wer,e less severe than those recommended by the IMA Ad Hoc Camlmittee.
or sciatica. Correspondingly, r.ecurrent stiffness, pain or tiredness occunred in 25 % and 50 % of IUhe cas'es. In the medica.l examination the following diagnoses were obtained: 20 % of the younger and 27 0J0 of the 'Old-er lumberm-en showed dorsa-lgia and insufficientia dorsi, and 'correspondingly 16 % and 24 0J0 lumbago-sciatica. The number ,of ·diagnoses per case was found higher than that in similar population studies in other groups. The diff.erenee can be explained by the higher incidence of bade .diseases in lumberm-en. In a salmpI.e studied in Firuland, which ,represe-nted all bhe lumbermen of the country, 47 % compl,ained of back pain during the two previous y.ears, and the incidence of back pain seemed to correlate with the numbe.r :of years of working with a chain saw (8). Of those Who had changed to a Ugh tel' occupation, 70 % suffered from back troubles.
From the labnv'e data it can be 'Concluded that 'an X-ray 'examination of the :lumbosaoral spine should be included in the preemp10yrment 'ex,aminations ,of lumbermen. This paper pr.esents t.he results of a ,study of the low back X-ray findings of 807 Finni.sh lum,ber,men in a pr,eemployment examination.
In winter the majority of lumbermen in Finland worJe in employ,ments of short duration Or are employed in johs with a seasonal nature. In summer they float logs or work ·on their .own small ,farms, Indus-triaEzation and urbanization have caused a decrease in this population sector of the country. Recently there has been a tendency, LespeciaJlyam-ong young anen l to find liglMer and better-paid jo.bs of a less seasemal nature in the towns. The shortage of laborers in the rur,al ·areas ,as well as the in-cr-easing demands for training due to automation and reorganization have made it imp.erative for the lumber companies to hire permanent year-round staff (8).

SUBJECTS AND METHODS
This study was .made during the years 1971 and 1972, when two companies in centra'l and nonthern F.inland we-re aruanging their .lumbermen .on·a per,manent basis. All of the 807 apphcants, 18 to 52 years of age, had worked as lumbermen more or less hon agrees with the results of p.revious studies, according to which those working i.n heavy occupations show these changes more frequently and at an earlier age than those in .control groups performing less :physically demanding wm!k (1). Such studied groups lare miners (2, 4, 11), lumbermen (9), dodk worker.s, and ;laborers in he"wy indust.riall work (10). Owing to the .la'Qk of ,control ,malteriwl interpreied by the sa.me .ra.diologist, we refrained frDID making a -closer -descriptLon and c:lassifi-eaHon '0;£ these ohanges. A mild or moderalte convex SQoliosis, pRtticuliClrly on the .left side) which was a relatively comm,on finding in our materiaI 1 can be considered a ohang.e acoompanying the oocUipation. Wor:k that inwolves bending with a chain saw r·esuJts in a static posi-Honing of the baek in this dire-ctLon. The preva<lenee of spondylolisthesis in the X-rays of an umelected "dull population is stated to be from 2 to 3 0/0 in various studies (14,18,20, .among oihers). The presenlt .study showed a preva:lenc-e of 4.2°/0; in ithe youngest age g,ljO:up it was 8 %, whioh differs significantly from the average 2.5 % (p < 0.01). An explan"tion should he sought -i.n ,addiuLon to mere coincidence -in view ,of the £oHowi'ng pos-sib~lities: 1. Spondylolisthesis may be hereditary (15,16,18). Tlhe majority of lumbermen included in this m,aterial were from northern Finland, where genetic ,isolates and clustering -of some hereditary diseases ·are known to 'occur (17). 11he possible family connections 'of the subjects have not been examined.
2. Prevalences of spondylolisthesis higlher than the average have been en- The per,eentage of rejection due to back diseases in thi,s st'udy ,totaled 11.4 % 1 which was about the same as in some eaplier studies (19,20). Even higher figures, .ranging fro.m 16 to 28 % ha'Ve been given (5,' 12). The criteria vary in the studies. Different jobs involve different requirements and Ithe question of rejection often leads toa compromise between two factors: the employer's tendency to hire workers ,of low ,disability risk and the supply of the workers available a,t the moment.
Our material .revealed, sta,rting from quite young age groups, a fairly high incidence of degenerative changes of the lumbar spine, nar.rowing of the intervertebral spaces, sclerosis of the vertebral p1ates, osteophyte £o.r-mati-on, .and. arthrosi,s of the .apophyseal joints. This observa-DISCUSSION limbs, and diabetes, As expected, their prevalence was higher in 'Older ·than in younger age groups. At the moment of the examination approximately half of the youngest gr.oup and thY.ee-fourths ,of the oldest group of rejected candidates show.ed dinka.) .symptoms of the back. In .the oldest age g,roup -various deg,rees 0.£ degenerative changes were the commDnest roentgenological findings ,detected in' conn-echon with bacl};;: pain. In the youngest age gr.oup the most com,m,on ,cause of rejection was spondylolisthesis, the prevalence ,of which sunpassed in this study the frequency genera'lly noted in studied populations. not statisticaqly .significant. In one study (4) a prevaJience ,0:£ 6.7 !J/o .a'mong ;miners was £ound. In tWiG pr,eemploy.ment examina-Hons the f.requencies of 6.5 "/0 (19) and 7.0 % (12) were given; however 1 no reference to the previJous occUJlations 'Of th'ose ,applicants was included in the reports.
The jushficaHon for ,a lumbosacra,l spine X-ray in preB.n1(ployment examinations and ,tts usefulness asa predictive ta01 in view of 'later back troubles sti:ll lack controlil.ed pr,ospe,ctive studies. The possible r:ole of p\'hy,ska1'ly demanding work in the €/bio'1ogynf s,p;ondyi1o'Hsthesis needs further investliga,ti,on, counter.ed, besides the Eski,mos of Alas'ka (even 30 %)1 also -among Norwegian Lapps (12 '/0) (15). It is not known how many of the studied nor.thern Finns wer.eof Lappish origin 1 probably not many, 3, Spondylolisthesis does not appear in newborns. Its frequency increases after the age when ,ohi'1dren stand ,up in Itlhe waUdng posit10n and after iJhe dev,e'1opmen t ;0£ the lumbar ilo.rd.:osis. lit is caffip.arativeJy ra,re in .childr,en and increases as adiolescencẽ ppr.oac:hes, T,he ,pI1ogression 'Of the diisplacement is 'Carom'on in the age group of 10 to 19 years, but rare aHer theag.e ,of about 20 years. rDhis phenomenon is explained by the pathogeny of spondylDlis-'1:Jhesis. Congenital dysplasia tOf lthe neuI'fal a·rehes and/or lSoft tissues in the lumihosacral .regi,on leads .to elongatiion of the Hbr-o:cartUaginous pars intera-rticularis, a stress fir,acture, and a sliding lof v-ertebna in the ventral direction (15, 16 1 18). Since standing u[J and learnling ,to w,aflika-re conside,red to sl-a,rt the deve1npmen t of spondylohsthesis in a small child, it could be assumed that exceptionally heaivy stress on the back in adolescencealso contributes to the deveIopment of spondylotbthesis. AccordingIy, tthe higlh frcquency of spondy,lO'l~isthe.si,s in young lumbermen could be srttribuked to 1Jhe heavy wonk which luhey hav.e he.en doing in most ·cases a.fter le,aving sohoo.1 1 so,meUmes as cady as the ages Dr 14 to 16 yea'rs. l1he decrease in the oMer groUJps 'could be traced back ,to the fact that in some of them the clinical symptoms became so -severe as ,to compel them to change to lighter occup.ations 'or to retire on a di,sability,pension. Unpublished statistics of '1Jhe pens10n -funds iof the forest industry in Finland Ireve.al that 1umbermen have been ,aJtlJowed disability pensions ibecause of ,sp-ondylolistihe.sis ,more frequently than ,those penfonming lighter wonk. This fact may be .accounted for either by the higher incidence or" spondy,l,olisthesis among 11iUmbermen or by 1Jhefaot that in spondylolisthesis symptoms do not app.ear in those performing 'lighter work.
In ,the .literature ther,e ,are few references to spondylolisthesis showing incidences higlher than the average in Iphysically demanding o:ccupati'ons. In the malterial of HuLt '(10) the frequencies in light an.d heavy ocoupations were 1.5 % and 2.5 %, respectiveJYl hut ilhe differenee w.as