Article PEMF Lumbar Fusions

8/2/2019 Article PEMF Lumbar Fusions

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A Random ized Double-B lind P rospectiveS tudy of the Efficacy of Pulsed

E lectromagnetic F ield s for In terbodyLumbar Fusions

VERT MOONEY, MD

A randomized double-blind prospective study of pulsedectromagnetic fields for lumbar lnterbody fusions waser;tormedon 195 subiect~. There were 98subjects in thective group and 97 SUbjects in the placebo, group., Ara~ .containing e~ui,pment. to induce an ,electromag-et!c field wasa.pphed to pat'lents undergoing InterbodyUSion in the active group, and a sham brace was used inhe control group ..In th e active group there was a 9.2%uccess rate, while the control group had a 65% successate (P > 0.005). The effectiveness of bone graft stimula-on with the device is thus established. [Key words:umbar interbody fusion, pulsed electromagnetic field,usion rate]

LUMBAR FUSIONS with or without internal fixation are slow toachieve tot~ union and t~e s~ccess ra~estill remains unpredict-able. The interbody fUSIOn IS artracuve, but incorporation 10

chieve solid union is slow. Because of the anatomic setting, there is awide avascular space between the vertebral bodies. Although the boneraft is typically under compression loading, revascularization and,hus, ossification of the bone graft takes many months. Some of theroblems in using lumbar fusions and specifically interbody fusions areecause of this phenomenon.Certainly it is reasonable from a clinical. standpoint 1 .0 search for

mechanisms that might enhance the rate and percentage of success ofnterbody lumbar fusions.

BACKGIROUND

What can bedone to enhance the biologic factors that control the rar-of fusion? 1 .n the 1960& it was discovered thaI mechanical stressesenerated electrical potentials in bone. 3.12 Thus it seemed reasonable tossume that manipulation of electrical energy might enhance bone

epair. Bassett later demonstrated this." Finally by the mid19705,

lectrical energy in the form of electromagnetic fields was demonstratedo accelerate bone repair.sThe efficacy of this form of bone stimulation remained controversial

n the area.of fracture repair because of the great difficulty of providingmatched fractures in a real- life setting. Although it. appeared to beuccessful in homogeneous patient populations,IO,I3.Z4 it was verydifficult to draw a solid conclusion because of the relatively smallnumbers, which did not allow statistical interpretation. 2 1 Eventually, agood model emerged for fracture healing in the form of comparison of a

P re se nt ed a t t he Fou rt h Annual Meet in g o f t he No rt h Ame ri ca n Spi ne Soc ie tyJune 29-Ju ly 2. 1989, Quebec City , Canada. 'Subm it te d f or p ub li ca ti on Novembe r 1 , 1 989.From tb~ Un iv er si ty o f Cal if or ni a, I rv in e, D i vi si on o f O rt hopa ed ic Surge ry.

rvine, Californla.

standardized operation. Intertrochanteric osteotomy provides such amodel. Recently, Borsalino et al ? demonstrated that pulsed electromag-netic fields in a double-blind prospective study of 32 consecutivepatients showed a statistically significant differenl (P > 0 .0 I) betweencontrols in stimulated patients. [11 thisseries, a blinded observer read theroentgenograms of the intertrochanteric osteotomies at 40 and 90 daysafter osteotomy. Criteria for union was 50% obliteration of the osteot-omy site. This study had the advantage of unbiased radiographicreading of a standardized surgical procedure at standardized timespostsurgical time.

Although direct current s timulation has been demonstrated to en-hance fusion, 9.17 these studies were neither blinded nor strictly random-ized. The potential advantage of pulsed electromagnetic fields for theachievement of enhanced lumbar fusion certainly is apparent in thar thedirect current devices are invasive and potentially require removal of thestimulating device, which is an additional disadvantage. Kahanovitz!"performed a eries of lumbar fusions on dogs and demonstrated anenhanced rate of early repair but could not demonstrate an ultimatelyhigher success rate of fusion at IS weeks. The results were based on

histologic as well as radiographic evaluation. Rate of new boneformation of course. is extremely difficult to monitor, even histologi-cally. Quantif ication of bone formation requires s tandardization ofevaluation and test situations.

At our laboratories at the University of Texas Southwestern MedicalSchool in Dallas, a system of quantitative analysis of new boneformation was developed." This system used an osteoconductivelattice of porous hydroxyapatite (HA). This structure was made fromsea coral. This form is a very consistent structure and thus offers astandardized framework. In addition, quantitative morphometry usingback scatter scanning electron microscopy was used for objectiveevaluation. With this method, the density of new bone versus implantversus sof t tissue or void space could be differentiated. The density

specific images were digitized and counted by computer. This resultedin a quantitative measure of the percentage of new bone versus implantversus soft tissue space. Also the boundary fraction could be deter-mined, ie, the percentage of implant covered by new bone. With th ismethod it was possible to determine the efficacy of various types ofbone substitutes. 22

Because of the potential for very precise quantification of the rate ofnew bone formation, this appeared to be an excellent model to evaluateadjuncts to bone formation. Thus this study was initiated. whichcompared bone in-growth into porous structures under the influence ofpulsing electromagnetic fields. 22 In th is study, rabbits were placed inplastic cages w ii h a pair of parallel transducers placed around the plasticcage for 8 hours. A magnetic field of 1.8 gauss with a f requency of 1.5Hz. was used. The control rabbits were placed in similar plastic cagesremote from the electromagnetic f ields. Three millimeter diameter


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im plants were placed Jnto the tibia of the animals. Each tibia had ahy drox yapatite im plant and triealcium ph osp hate im plant. Th etrieal-eium ph osp hate im plant hada m uch sm aller pore size. Thespecimenswere obtained at . 1, 2, 3, 4, and 6 weeks after s urg er y. P re vi ou sexperience bad identified that m ax im um am ount of new bone form ationin this sp ec ific m od el w as a ch iev edin rabbits at 6 weeks.

As noted in Figure 1, a volume fraction of bone was signmcam lyg re at er i n t he imp la nt sefanimals re ce iv in g p ulse d e le ctroma gn eti c fie ldtreatm ent. The sam e w as trueo f .t hemean t ra be cu l a rthickness of newbone. Interestingly, there was no affect. on im plants of tricalciump ho sp ha te w it h[he diminished pore size. The po res of the hydroxyap-atite (Interpore Jnternational, Ine., Irvine, CAl averag e 600 ,!-Lmind ia me te r w ith in te rc on ne ctio ns a ve ra gin g26 0 !-Lm i n diam eter. T hetricalcium p ho sp ha te p ore s m ea su redLOO-300 l !- lm wi th i nconsi st entinterconnections. The effect of pulsed electrom agnetic fields thusappeared most b en efi ci al e arlyin the healing phase. Certainly by thiswell-controlled study, 3. d efi ni te e ffe ct o f p uls ed e le ct rom ag ne ti cfieldsc ou ld b e i de nt if ie d.

'Because of the dem onstration of positive affect by this controlled

study, i t seem s reasonable to progress into clinical application of thisnon invasive m ethod. O n this basis, a pro tocol for clinical applicationwa s d ev el op ed i n coopera ti o n w ith A merican M edical Electronics ..Itw as recog nized fromth e be gin nin g Ih alt hi s s tu dywould have to beap ro sp ect iv e blin de d stu dy inan e ffo rt t oo ffer sc i en ti fi cc re di bi li ty t o t heapplicat ion of pulsed electrom agnetic fields. The only m ethodofevaluation bya . m ulticenter study w ould be radiographic.It wasrecognizedthat ra di og ra ph ic c ri te ria w ere e xtre me ly d iffic ultto stan-d ard ize .. I nte rbo dy fu sio ns a tlea st h av e g re at er p ote nt ia l fo r re pe ata bleradiographic evaluat ion as to union status com pared w ith posterior orp os te ro la te ra l f us io ns .It was recognized that a m ore ideal method ofu nio n e va lu at io n w ou ld be ra ng e-o f-m oti on fi lm s.It se-e me d im po ssi bleto assum e a standardized m ethod of range-of-m otion, w hich w ouldbe

com parable in the m any centers to be used for this procedure.Jt washoped that theus e of bl ind ed observers w ou ld offer at leasta standard-ized m eth od o f ra dio gra ph ic re ad in g.

100,

eo

60

40

20

OL----~~--~--~----~--------~2. 34 6

WEEKS

Mean trabscular t,h,ickness of new bone in ttle cor-tical window area. Vertical bar: mean widttlof bone trabec-ulae (""m). Horizontal bar: postoperative period (weeks.). Hy-droxyapatite (HAl in the pu'lsing electromagnetic held(PEMF) group '.- ). HA in the oontrol group (0--0): TCPin the P,EMFgroup (.-.): Tep in the 'can tro I, group (0--0).Resul ts are expresssdas the mean :!: SEM. StimullatedHA

demonstrated significant differences from the control HA at.p < 0.025 and ",p < 0.01 by norrparametric analysis andWelch's approxima tion to the r test

PULSED ELECTR OM AGNETIC FIELDS M OO

MATERIALS AND M ETHO DS;

Surg eo ns fam ili arwith interbody fusions were recrui ted forproject. In the group of patients w ho w ould receive a nonfunctibra ce , in stitu tio na l re vi ew bo ard s o fth e v ario us c oo pe rat in g i nst iiasistedthat th e p ati en ts be aware of this when they agreedtopart icipate. It was inappropriate to ask insurance com panies to papotent ially n onoperat ing electro magnetic field braces. T he equwas therefore do nated by th e m anufacturer. T he num berof cases eachsu rgeon cont ri but edto this study are H stedin Table 1 .

Patients included inthis study w ere adults of either sex underg oinitial attem pts at interbody spinal fusion ei therfrom am anterior orposterio r approach. C andidates w ere excludedif they p resented w ittraum a, inflam matory condit ions of the spine, severe osteoporosm etabolic problem s such as diabetes, renal dysfunction, o r m etcancer.A fter surgery, patients w ere fitted w ith aspecial b ra ce Wi th e le ct ro

magnetic coils, which they were instructed to wear at least 8 hday. Neitherthe patient nor the surgeon w asaware o f t he fu nc ti on in gc ha ra ct eri st ic s o fth e brace. Th ey w ere aw are. how ever,that t he b ra ceitself m ayor m ay notbe functioning. The patients w ere not aw areth e am ount ofusage w as m onitored by the brace.

S uc ce ss c rit eria w ere ba se d o n ra dio gra ph ic e va lu at io n.A fu si on wasdefined as solid ifit was more than50% assim ilated. T he su rgeoi de ntifie d t he ra dio gra ph ic st at usat the tim eof a nio n, bi ll a n in de pe nd en t blin de d radiologist confirmed this reading. In cases wheredisagreem ent betw een th e clin ician and rad iologist o ccu rred, apendent blinded orthopaedic surgeon acted. as the third review ei nv estig ato rs' d ia gn osis o f fa ilu re w as n ev erallowedto be overruled byth e i nd ep en de nt re vi ew.In am a rt hr od es is s pa nn in g2 se gm en ts, bo thl ev els h adto b e g ra de d.as solidly fused fo r t he patient to be classified aa success.

Safety was evaluated on the basis of the incidence of sucomplaints and a dv er se r ea ct io ns .In a dd it io n, t he c li ni ci an i de nt ifw hether the clin ical result was excellent, good, fair, or poor.characteristics such as disabili ty tim e befo re surgery, sm oking,

bers of previous surgeries, and graft ty pe w ererecorded,

RESULTS

A to tal of195 p atie nt s c om plet ed th is stu dy. T he re w ere98 patients inthe active group and97 patients in th e p la ce bo g roup .In t ha t t he b ra ce

Table 1. Part icipat ing Surgeons Ranked by Number 01 ' CasesContributed


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PULSE D ELECTROMAGN ETIC FIELD S M OO

Table 6. Randomized Double-Blind Phase Results by Diagnosis

Active group Placebo group

Diagnosis rota I number Total healed Success rate TOlal number Tote! healed Success rate

Herniated nucleus pulposus .20 17 85,0% 17 13 76.5%Spondylolisthesis I 4 4 100,0% 5 4 80,0%Degenerat ive disc pisease 19 17 89,5% 13 8 61,5%Internal disc disruption 25 25 100,0% 23 15 65,2%Failed fusion 1 .0%

1 1 100,0%Stenosis 2 2 100,0% 1

.0%

Other 3 3 100.0% 1 1 100.0%

Table 7. Randomiz.ed Double-Blind Phase Results by Number of Fusion Levels

A Clive group Placebo group

Fusion level Tot.al number Total healed Success rate Total number Total healed Success rale

Single level 46 43 93.5% 40 29 72.5%Double level 18 16 86,9% 13 7 53.8%3 or more levels 0

.0% ,0%Total 64 59 92.2% 53 36 67.9%

37.6 years of age at the start of treatm ent . The differential of agebetween older than 50 years and younger than 50 years offered nos ta ti st ic al s ig ni fi canc e. Th e dura ti on o f t ime bef ore s urgi ca l c ar e a ls ooffered no s igni f icant d i fference.T hu s, 92.2% o f p at ien ts re ceiv ing ac tiv e d ev ices an d u si ng t hem

co nsisten tly h ad a solid fu si on a s d efi ned by blin ded rad io grap hi c

eva lu at io n o f t he bon egraft T ho se i n th e p la cebo g ro up fu sed at a rat eof 67 ,9%. Th is i s s ta t is ti ca ll y s ign if ican t a tP > 0 ,005 , F ac to rs s uch a ssex , age, fus ion l eve l, number o f g ra ft s, g ra ft t ype , and in te rna l f ixa ti onmade no d if fe renc e. Smok ing made li tt le d if fe renc e.P at ie nt t ole ranc e o f t he d ev ic e was f ai rl y good, a lt hough i t was f ound

to be u nc om fo rtable an d bu lky by abo ut. 13% o f th e p atie nts. O th erfac to rs were rel at ive ly i n si gni fi can t (Tab le 8 ). There was some co rrel a-t io n b etween r ad io gr aphi c s uc ce ss and c li ni ca l s uc ce ss (Tab le 9 ). A llp at ie nt s h ad b ee n e va lu at ed a m in imumof 12 mont hs a ft ersurgery,Clin ical charac te ri st i cs a t a l onger fol low-up were no t t abu la t ed .1 rIthep la cebo g roup , c er ta in ly radi og raph ic s uc ce ss cor re la te d w i th a goodresul t and rad log raphi c fai lu re co rrel at ed wi t h a poorer r esu lt . However,t he numbers were t oo smal l t o o ffer s ta ti st i ca l s ign if icance,

Table a , Randomized Double-Blind Phase Safety byPatient Complaints

Acllve group Placebo group

Category n % n %

None 90 84.1% 84 84,8%Patient finds device bu lky 14 13.1% 13 13,1%or uncomfortableMinor skin ra sh 2 1.9% 0,0%Insomnia 0 0.0%

0,0%

Pain whil e using device 1 0.9% 1 1.0%Fainting 0.0% 0,0%Nausea! diarrhea 0.0% 0.0%

DISCUSSION

P ulsed electremag neti c fie ld s h av e bee n ap plied w ith su ccew id e a rra y o f p hy si olo gi c h ea li ng p ro blems ,This seems to makedi fference in neuroregeneration ,l~.19 i n h ea li ng o f s ki n wou nd s,2 oin th e h ealin g of lig am en ts.II It has been dem onstrated to m akd iffere nce in h um an so ft ti ssu e h ealin g u ch as ep ico nd yli tis/rot at o r cu ff r endou i ti s.6 O ur ow n studie identified that the effebon e h ea li ng o ccur s e ar lyin th e h ealin g p hase, Wheth er t hi s is ds timul at io n o f n ew b lood s upply i sundefmed.P Apparen t ly t herei aneffec t o f rev ascu lariza tio n in fem oral h ea d ne cro si s.l! A ll ostudies confirm thal there is a physiologic event related toelect romagnetic f ields.An apparen t conf irmarory s ta ti st i c o f t h isstudy i s ' thecorre lat ion w

comp li an ce and s ucce ss . Thi s s pe ci fi c f ac to r may be an exp lanas ome b lu r i n ou r und er st andi ng o f t he e ff ic acyof t h e method.Certainlyclin ica l comp lian ce i s o ften o ne of th e m ost co nfo un di ng feat he rapeut ic t ri als . The s peci fi c equ ipmen t u sed i n t h i s s tu dy a llevalua ti on o f t hat a spect .Certainly one m ight crit icize this rudy for usfa i lu re tobe more

specific in the analysis of fusion, G iven the scope of thehowever, there seem s no other alternative than to rely purrad iog raphi c c ri t er ia . Even th isis d if fi cu lt i n t ha t o bv ious ly t he quof fi lm s from24 d ifferen t in vestig at ors can no t be u ni form .v ar ia bi li ty, h oweve r, s hould b e c an ce led out w i th t heU 5 1: :o f a b li nd eobs er ve r w i th no know ledg e' o ft he s urgeon o r t re atmen t me thoAn invest i ga ti on o f t he pu ls ed e lec tromagne t ic f ieIds for pseudarthro

s is h as a ls o b een p er fo rmed. Thi s, o f cou rs e, c ou ld not .b e a p ro sdoub le -b li nd s tudy in that t he surgi cal care had a lr eady been carNonethel es s, pa ti en t s couldbe ra nd om iz ed o n t he b as is o f c on si s 8 hours a day) and inconsistent use, A group of126 patientsp artic ip ate d i n a m ulti cen te r sm dy.ls In t hi stu dy . 10 0 p at ie

co nsist en t u se h ad a 6 7% rad io grap hic su ccess (5 0% a ssim ild ef in ed by b li nd ed r ad io lo gi st s). I ncon si st en t u se rs h ad onlysu ccess In th is g ro up th ere w as a m uch c lo se r c orre lat io n b


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12 SPINE VOLUME 15 NUMBER 7 1990

Table 9. Handornlzed Double-Bllnd Phase Results by Clinical Assessment

Active grOIJP Placebo grolJp

Radiographic Radiographic Radiographic Radiographicsuccess failure success failure

Clinical assessment n % n % n % n %

Excellent 30 50.8% 1 20.0% 13 36.1% 3 17.6%Good 21 35 .. 6% 1 20.0% 1B 50.0% 5 29.5%Fair 5 B.5% 1 20.0% 5 13.9% 4 23.5%Poor 3 5.1% 2. 40.0% 0 .0% 5 29.4%

Total 59 100.0% 5 100.0% 36 100.0% 17 100.0%

Table 10. Randomized Double-Blind Phase Completed,OngOing, Withdrawals, and Lost to Follow-up Subjects

Active group Placebo group

Type n % n %

CompletedConsistent use 64 59.8% 53 53.5%

Inconsistent. use 34 31.8% 44 44.4%Ongoing 0 0.0% 0 0.0%

Withdrawn from analysisSurgical intervention 1 0.9% 1 1.0%Medical disqualification 4 3.7% 1 1.0%Lost 10 t oil ow- up 4 3.7% 0 0.0%

Talai subjects 107 100.0% 9 9 100.0%

treatm ent by pulsed electrom agneticfields for pseudarthrosis perhaps isrelated to the lim ited ability for revascularization in this particularsetting. This perhaps is related to the greater correlation of failurewiththe sm oking population as w ell. Technical factors m aybe significant. [0a n e arli er st ud y, a h ig he r su cc essrate was noted when a double coil was

u se d r at he rthan a single coil. A sioglecoil offered a success rate of7 7%(to of 13). The d ou ble c oi l o ffe rsa success of92.2%. App aren tly t hed ou ble c oi l o ff er sa sli gh tly h ig he r m ag ne ti c fi eld(1.8 gau ss c ompar edw ith 4 gauss). W hether these factorsare really significant, of course.wou ld n ee d f ur th er e va lu at io n.

The use of the electrom agnetic brace offers a. sm all intrusion ontopatient com fort. Certainly patient com pliance isan important factor.Discomfort with the use of the brace is a realistic complaint, butim provem ent in brace design should resolvethis. The re a re a pp ar en tlyno adverse affects of significance with the useof this treatment.Potential for benefit is dem onstrated in a statistical m anner. Thus it isreasonable to advocate its usefo r f ur th er a pp li ca ti onin f us io n p ro ce -dures.

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2 2. S him az aki K . Mo on ey V:C omp ara ti ve s tu dy o f p oro u h yd ro xy ap at it et ri ca lc ium phospha te a s bone sub st it ut e.J Onh op R es3:301-310.1985

2 3. S hi rn iz uT, Z erwe khlE. Vid eman T. G il lK , Moon ey V: B on e i ng rowt h i ntporous calcium phosphate ceramics : in fluence of pu ls inge lec tromagne ticfield.J O rt ho p R es 6 :2 48 -1 58 . 1 .9 88

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Add re ss r ep rin t r eq ue st s/0

Vert Mooney, MD

University of California, IrvineDivision O fOrt ho pa ed ic Sur ge ry

Irvine, CA.92717

Accept ed for publ ic at ion MarchI, 1990.

Article PEMF Lumbar Fusions

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