Heckman JD, Ryaby JP, McCabe J, Et Al. Acceleration of Tibial Fracture Healing by Non Invasive,...

8/4/2019 Heckman JD, Ryaby JP, McCabe J, Et Al. Acceleration of Tibial Fracture Healing by Non Invasive, Low-Intensity Pulse

1/10

The PDF of the article you requested follows this cover page.

This is an enhanced PDF from The Journal of Bone and Joint Surgery

1994;76:26-34.J Bone Joint Surg Am.JD Heckman, JP Ryaby, J McCabe, JJ Frey and RF Kilcoyne pulsed ultrasoundAcceleration of tibial fracture-healing by non-invasive, low-intensity

This information is current as of May 25, 2009

Reprints and Permissions

Permissions] link.and click on the [Reprints andjbjs.orgarticle, or locate the article citation on

to use material from thisorder reprints or request permissionClick here to

Publisher Information

www.jbjs.org20 Pickering Street, Needham, MA 02492-3157The Journal of Bone and Joint Surgery
http://www.jbjs.org/http://www2.ejbjs.org/misc/reprints_perms.dtlhttp://www.jbjs.org/http://www2.ejbjs.org/misc/reprints_perms.dtlhttp://www.jbjs.org/http://www.jbjs.org/http://www.jbjs.org/http://www.jbjs.org/http://www.jbjs.org/http://www2.ejbjs.org/misc/reprints_perms.dtl


2/10

Copy r i gh t 1994 by Th e Jou rna l o f B one and J oint Su rge ry . I ncorpora ted

26 THE JOUR NA L O F BON E AND JO IN T SU RGERY

A cce lera tion o f T ib ia l F rac tu re -H ea lin gby N on -Invasiv e , L ow -In ten sity Pu lsed U ltra sound*

BY JAMES D . H ECKM AN . M .D .t, JOHN P . R YA BY t, JO A N M CCABE , R .N .I , JOHN J. F REY . PH .D 1 . A ND R AY F . K ILC OYN E . M .D .# .SA N AN TON IO . TEXAS

inv est iga tion p erform ed a t Th e U niv ers ity o f Te xas H ea lth S cie nce C en te r a t Sa n Anton io , S an A nto n io

ABSTRACT : S ix ty -seven c losed o r grad e -I op en frac -tu res o f th e tib ia l sh a ft w ere ex am in ed in a p rosp ec tiv e,random ized , d oub le-b lind eva lua tion of u se o f a n ewu ltra sou nd stim u la tin g d ev ice as an ad junc t to conv en -tiona l tr ea tm en t w ith a cas t . Th ir ty -th ree fra c tu re s w eretrea ted w ith th e ac tive d ev ic e an d th ir ty -fo u r , w ith ap lacebo con tro l d ev ic e . A t th e end of th e trea tm en t,th ere w a s a sta tis tica lly s ig n ifican t d ecrease in th e tim eto c lin ica l h ea lin g (86 5. 8 days in th e a ctive -trea tm en tg roup com pared w ith 114 10 .4 days in th e con tro lg roup ) (p = 0 .01 ) and a lso a s ign ifican t d ecrea se in th et im e to over -a ll (c lin ica l and rad iograph ic ) h ea lin g (9 6 4 .9 days in th e ac tive -tr ea tm en t group com pared w ith154 13 .7 d ay s in the con tro l g roup ) (p = 0 .0001). Thepatien ts com p lian ce w ith th e u se o f th e d ev ice w asexce llen t, a nd th ere w ere n o serio u s com p lica tion s re -la ted to its u se . T h is s tudy con firm s ea rlier an im a l andc lin ica l s tud ies th a t d em onstra ted th e effica cy o f low -in ten sity u ltrasound stim u la tion in the acce lera tion o fth e no rm al frac tu re -repa ir p rocess .

U ltra soun d h as m any m ed ica l ap p licatio ns, in clu d -in g the rapeu tic , o pe rat ive , and d iagn os tic p ro cedu res .B o th u ltra sou nd the rapy and ope rative u ltra sou nd sub -je ct tissue to pow er leve ls tha t a re capab le o f caus ingcon s ide rab le h ea tin g and b io lo g ic a l e ffec ts . In co nv en -tiona l u ltra so un d the rap y , u ltra son ic in ten s itie s o f on eto th ree w atts pe r squ are cen tim e te r a re used to de -c rea se jo in t s tiffn ess , red uce pa in and m u scle sp asm s,and im p rov e m usc le m ob ility . T he op era tive app lica -

*O ne or m o re of the au tho rs hav e rece ived or w ill rece iv e ben-e fits fo r p ersona l or p rofess ion al use from a comm ercia l pa rty re-la ted d ire ctly o r in d ire ctly to th e sub jec t o f th is art ic le . In add itio n ,benef its h ave b een o r w ill b e d irec ted to a re sea rch fund o r fou nda -tio n , e duc ationa l inst itu t ion . o r o the r no n-p rof it o rg an iza tion w ithw hich o ne or m o re of the au th ors a re as soc iate d . F unds w e re re-c eived in to tal o r p art ia l supp ort o f th e re sea rch o r clin ic al stud yp resen ted in th is ar tic le . Th e fund in g sou rce w as E xog en , Inco rpo -rated .

tD ep artm ent o f O rth op aed ics . Th e U n iversity of T ex as H ea lthSc ien ce C en ter at S an A nton io , 770 3 F loy d Cu rl D rive, San A nto n io ,T ex as 7 82 84 -7 77 4.

lExogen , In corporate d . 8 10 P assaic A v enu e, W est C a ldw ell ,N ew Jersey 0 7006-6489 .

3 8 R andolph Ro ad . W h ite P lain s, N ew Y ork 10607 . lHeal th P ro duc ts D eve lopm ent, Inco rpo rated , 1 853 W illiam

Penn W ay , L ancas te r, Pennsy lvan ia 17601 .#D epar tm ent o f R ad io lo gy , Th e U n ive rsi ty of Co lorado H ealth

Scienc e C ente r, 4200 E ast N in th A v enu e, D env er, C olo rad o 80262 .

tion o f u ltraso un d em p loy s in ten si ty lev els o f five tom ore than 3 00 w atts pe r squ are cen tim e te r to fragm en tca lcu li an d to ab la te d ise ased tissue s such a s catara cts2 0 .T hese re la tive ly h igh u ltra sou nd in tens itie s a re em -p loy ed to g en era te h ea t w ith in th e tissu e s, th rou ghw hich th e u ltra soun d signa l p asses5 . D iag no s tic ap p lic a -tio ns o f u ltra so und in clu de exam ina tion of v ital o rgans ,eva lua tio n o f fe tu ses , v ascu la r an d pe rip he ral flow stu d -ie s , and oph tha lm ic echo grap hy . T he d iag nos tic ap p lica-tio ns o f u ltrasou nd use m uch low er in ten s itie s , typ ic allyfive to fifty m illiw atts p er squa re cen tim ete r, to av o idexcess ive h ea tin g o f t issu es.

X av ie r and D ua rte2 rep o rted the acce le ra tion o fth e n o rm al frac tu re-repa ir p rocess in hum ans w ith useo f low -in tens ity (d iag no stic-rang e ) u ltra sou nd an d alsoin d ic ated th at low -in tens ity u ltra so un d can ind uce h ea l-in g o f un un ited d iaph yseal frac tu re s22 . W ith use o f arab b it fib u la r o s teo tom y m ode l an d a seco nd m ode lth at em plo yed a d ril l-ho le in th e co rtex o f the fem ur o fa rabb it, D u a rte dem on stra ted acce lera tion of th e nor-m al frac tu re -repa ir p ro cess w ith u se o f u ltraso un d .P il la e t a !., w ith u se o f a s ligh tly d ifferen t fibu lar o steo t-om y m ode l, a lso d em on stra ted tha t n on -inv as iv e , low -in ten s ity pu lsed u ltraso und accelera ted fra ctu re -h ealingin the rabb it. K lug et a l . u sed a sc in tig raph ic te chn iqu eto dem onstra te qu ick er m a tu ra tio n o f the callu s an dearlie r h ea lin g in ex pe rim en ta lly ind uced c losed fra c -tu re s in a rab b it m od el a fter u ltra sou nd s tim u lat ion w ithin tensity leve ls tha t w ere an orde r o f m agn itu de h igh erthan th ose used b y D ua rte o r by P illa e t a l. B ecau se w ebe lieve tha t th ese p re lim in ary s tu d ie s c le arly sh ow ed apo sitive e ffe c t o f u ltra sou nd on th e ra te o f o sseou s re-pa ir , w e de s ign ed the p re sen t s tud y to in ve st iga te th eeffe ct o f specifica lly p ro g ramm ed , low -in ten si ty p u lsedu ltra sou nd on th e rate o f h ea lin g o f co rtic a l frac tu resw h en u sed in p atien ts a s an ad jun ct to co nv en tio na lo rth opaed ic m an ag em en t.

M ater ia ls and M ethod sThe s tud y w as m u lti- in s titu tio na l, p ro spective , ran -

d om ized , d oub le -b lin d , and p la cebo -co n tro lled . T he rew e re co -in ve s tiga to rs from six te en s ite s in v ario us geo -g rap h ica l are as o f the U n ited S ta te s an d from on e s itein Is ra el.

An opportun ity to p art ic ip a te in the s tu dy w as o f-fe red to all ske le ta lly m atu re m en and non-p reg nan t


3/10

A CC EL ER A T IO N OF T I BIA L FRA C T U RE-H EA L IN G B Y N O N -IN V A SIV E. L OW -I N T EN SIT Y PU L SED U L T R A SOU N D 27

V O L . 76.A , N O . 1 . JA N U AR Y 1994

w omen seen at our institutions betw een September 1986and D ecember 1990 who were at most seventy-five yearsold and who had a closed or grade-I open tibial diaphys-eal fracture that w as primarily transverse, short oblique,or short spiral and that could be treated effectively withclosed reduction and immobilization in a cast.

A nteroposterior and lateral radiographs w ere madeimmediately after the reduction. W e excluded patientsif either the anteroposterior or the lateral radiographsshowed that the length of the fracture line w as morethan tw ice the diameter of the diaphyseal shaft (a longspiral or long oblique fracture), the displacement w asmore than 50 per cent of the w idth of the shaft, or thefracture gap w as more than 0.5 centimeter. O ther exclu-sion criteria were open fractures, except grade I as de-fined by Gustilo and A nderson; fractures of the tibialmetaphysis; fractures with persistent shortening of morethan one centimeter after reduction; fractures that w erenot sufficiently stable (recurrent or persistent angula-tion of 10 degrees or more in any plane) for treatmentw ith immobilization in an above-the-knee cast; fracturesw ith a large butterf ly fragment (larger than two timesthe diameter of the tibial shaft); pathological fractures;and comminuted fractures (comminution w ith frag-ments of less than one centimeter in length w as accept-able). Patients were also excluded if they had stated thatthey could not comply with the protocol: were receivingsteroids, anticoagulants, prescription non-steroidal anti-inflammatory medication, calcium-channel blockers, ordiphosphonate therapy; had a history of thrombophle-bitis or vascular insufficiency; or had a recent history ofalcoholism or nutritional deficiency, or both.

A fter they had agreed to participate in the studyand gave informed consent, the patients were random-ized into groups of four at each study site to receive anactive or a placebo-treatment device according to a pre-determined computer-generated code. T he code wasbroken only after the radiographic reviews had beencompleted.

N inety-six patients, who had a total of ninety-sevenfractures, were entered into the study. Forty-eight ofthe fractures w ere randomized to the active-treatmentgroup and forty-nine, to the placebo-treatment controlgroup. T hirteen patients (thirteen fractures [13 percent]) w ere lost to follow-up, leaving eighty-four pa-tients (eighty-five fractures [88 per cent]) in w hom thehealing status of the fracture was know n. A n additionalseventeen patients (seventeen fractures [18 per cent])w ere excluded from the study because of deviationsfrom the protocol.

Of the thirteen patients (four who had active treat-ment and nine, placebo treatment) w ho were lost tofollow-up and for w hom the final healing status w as notknown, seven had withdrawn from the study, five hadbeen w ithdraw n by the site investigator, and one haddied of unrelated causes seven w eeks after the fracture.Of the five patients who were withdrawn by the site

investigator, one had had an open reduction and inter-nal fixation of the fracture and the remaining four hadnot complied with the outlined treatment protocol.

O f t he seventeen patients (eleven who had activetreatment and six, placebo treatment) who were cx-cluded because of deviations from the protocol, six (twowho had active treatment and four, placebo treatment)had had an operative procedure w ithin six w eeks afterthe injury because of severe angulation of the fractureafter treatment had begun, seven were excluded be-cause the fracture did not meet the inclusion criteria ofthe protocol, and four were withdrawn by the investiga-tor because of failure to comply with the treatmentprotocol. T hese seventeen patients were still followedand the outcomes of treatment were obtained.

T he remaining sixty-seven fractures (thirty-threethat were treated with an active unit and thirty-four,w ith a placebo unit) represent the core group of frac-tures in patients w ho adhered to the study protocol andhad sufficient follow-up data. I t is this group from w hichthe clinical and statistical inferences were drawn.T here were sixty-four closed fractures (thirty-onein the active-treatment group and thirty-three in theplacebo-treatment group) and three grade-I open frac-tures (two in the active-treatment group and one in theplacebo-treatment group). T he fractures were treatedconventionally with closed reduction and immobiliza-tion in an above-the-knee cast. T he three grade-I openfractures were treated with initial d#{ 233} bridement, and thewounds were allowed to heal by secondary intention. Aretaining and alignment fixture made of molded plasticwas inserted into a window centered over the antero-medial surface of the cast, at the site of the tibial frac-ture. T his fixture held the treatment head module inplace during the daily twenty-minute treatment period.Between treatment periods, a circular, felt plug was in-serted in the fixture and a cap was placed over it tomaintain an even pressure on the skin and to minimizethe risk of edema at the site of the window.

T reatment was started within seven days after thefracture and consisted of one tw enty-minute periodeach day. T he treatment head module w as positioned inthe window after removal of the felt plug and the appli-cation of a small amount of ultrasonic coupling gel tothe surface of the head. I t was attached to a portablemain operating unit that contained the necessary cir-cuitry to drive the treatment head module and to mon-itor the proper attachment of the module in the castfixture. A warning signal was sounded by the main op-crating unit if there was not proper coupling to the skin.I n addition, the main operating unit contained an inte-gral timer that monitored treatment times and automat-ically turned the unit off after twenty minutes. A visualand audible signal alerted the patient that the treatmentwas complete. T he patients compliance with instruc-tions for use of the device was measured by both a timerinside the main operating unit and a patient-maintained


4/10

TA BL E IA SSESSMENT OF TREA TMENT -GROUP COMPA RA B IL ITY

Sex25

8

312

4171 1

1517

312

267

924

36 2.3

33 4.7(n = 30)23 2.5

6 1 . 0(n=30)

4 0 . 54 0.34 0.24 0.3

250 18.192-438

45 4 . 9( n =33)

0.37*29

50.64*

33

0 . 4 9 *8

15

110

0 . 6 0 *3

151 6

0.43*29

50.77*

286

0.13*4

3 031 1.8 0.091

38 4 .9 0.481(n=31)23 2.7 0.981

6 0.8 0.741

4 0 .4 0 .8 0 1

4 0.3 0.9214 0.2 0.5514 0.3 0.891

( n = 33)2 8 4 1 9 . 2 0.211

142-58649 5.9 0.621

A fter reducti ontAngulation (degrees)

B ef or e reducti ont

After reductiontM aximum fracture gapt (mm)L ength of fracturet (cm)D ays until start of treatmentt

D uration of follow-upt (days)Range

D ays to start of w eight-bearingt

28 J . D . H E C K M AN E T AL .

T H E JO U R N A L OF B O N E A N D JOIN T SU RG ER Y

daily treatment log. T he active and placebo devices w ereidentical in every way (they had the same visual, tactile,and auditory signals) except for the ultrasound signalemitted.

T reatment was continued for twenty w eeks or untilthe clinical investigator believed that the fracture w ashealed sufficiently to discontinue the active or the pla-cebo ultrasound therapy.

T he treatment head module delivered an ultra-sound signal that w as composed of a burst w idth of200 microseconds containing 1 .5 megahertz sine waves,with a repetition rate of one kilohertz and a spatialaverage-temporal average intensity of thirty milliw attsper square centimeter.

T he regimen for treatment of the fracture was iden-tical for all patients. Immobilization in an above-the-knee cast w as maintained until the investigator thoughtthat the fracture w as sufficiently stable for application ofa short cast or a brace. A fter immobilization in a cast wasdiscontinued, additional protection with either a splintor a brace w as at the discretion of the investigator. Castchanges were permitted as clinically indicated. W eight-bearing w as controlled on the basis of the investigatorsclinical judgment and the tolerance of the patient. T heonly difference in the common protocol of fracture man-agement w as the initiation of w eight-bearing. T he firstforty-two patients (forty-tw o fractures) enrolled in thestudy were instructed not to bear weight during the firsteight weeks after the fracture, and the remaining fifty-four patients (fif ty-five fractures) were allow ed to bearw eight as tolerated.

A ll patients were scheduled to return for follow-up radiographs at four, six, eight, ten, twelve, four-teen, tw enty, thirty-three, and fifty-two weeks after thefracture. A nteroposterior and lateral radiographs w eremade and standardized w henever possible, w ith use ofthe same x-ray machine at each site, the same exposuresetting, and a leg-positioning device that w as furnishedto each site investigator. Clinical follow -up evaluationsw ere performed by the site investigator at the time ofany cast change (usually at six and ten weeks) and at thefollow-up visit when radiographic evaluation indicatedthat the fracture had healed sufficiently to allow re-moval of the cast.

T he end-point of the study w as a healed fracture, asjudged both on clinical examination and on radio-graphic examination (three of four cortices bridged). I naddition to the healed-fracture end-point, intermediatestages of the fracture-healing process w ere assessed forthe difference betw een the active-treatment and theplacebo-treatment groups.

W ith regard to the intermediate clinical stages ofhealing, two parameters w ere evaluated: the time toclinical healing was defined as the time at w hich theindividual site investigator thought that, on clinical cx-amination, the fracture w as stable and was not painfulto manual stress, and the time to discontinuation of the

ParameterTreatm

Activeent G roup

Placebo P V alueN o. of fractures 33 34

MaleFemale

Fracture gradeClosedG rade-I open

T ype of fractureTransverseShort obliqueShort spiralComminuted

L ocation of fractureProximalM iddleDistal

C omminuted fractureN oY es

B utterfl y fractureNoY es

Fibular fractureNoY es

Age t (yrs.)Displacement (pe r c ent)

B ef or e r educt iont

*W i t h the Fisher exact test or chi-square test.tT he values are given as the mean and the standard error of themean.IW ith analysis of variance.

cast was documented as the time at which the site inves-tigator discontinued use of the cast.

W ith regard to the intermediate radiographic signsof healing, two parameters were evaluated. T he first,cortical bridging, was defined as the gradual disappear-ance of the interruption of the cortex at the fracture siteas a result of callus formation. T he amount of corticalbridging was quantified as none (no change at the cor-tical interruption compared with that seen on a radio-graph made in the immediate post-reduction period),initial (when a periosteal reaction at the cortical inter-ruption of the fracture site was first noted), intermedi-


5/10

A CC EL ER A T IO N OF T IB IA L FRA CT U R E-H EA L IN G B Y N O N -IN V A SIV E. L OW -IN T EN SIT Y PU L SED U L T RA SO U N D 29

V O L . 76-A , N O. I . JA N U A R Y 1994

TABL E I IIN TERMED IATE RAD IOGRAPH IC H EALING STAGES

D ays afte r F rac tu re P V al uetA ctive Placebo K ruskal-W all is

T reatment* T reatment R ank(N = 33) (N = 34)1 A N O V A A N OV A L og-Rank

3 bridged corticesPrincipal investigator 89 3.7 148 13.2 0.0001 0.0001 0.0001Independent radiologist 102 4.8 190 18.3 0.0001 0.0001 0.00()l

C omplete cortical bridging(4 bridged cortices)

Principal investigator I 14 7.5 182 15.8 0.0002 0.0001 0.0001Independent radiologist 136 9.6 243 18.4 0.0001 0.0001 0 .0001

Endosteal healingPrincipal investigator 117 8.5 167 13.9 0.002 0.0004 0.0004I ndependent radiologist 171 13.6 271 19.6 0.0001 0.0001 0.( )001

* T he values are given as the mean and the standard deviation of the mean, as calculated with analysis of variance.t A N O V A = anal ysi s of variance.IN o clinical data were available for one fracture that w as treated with the placebo device.

ate (an increase in the density or size of the initial pen-osteal reaction) or complete (the peniosteal reactioncompletely bridged the cortical interruption). O n eachradiographic evaluation at each time-point, four cortices(two on the anteropostenior radiograph and two on thelateral radiograph) were evaluated for the amount ofcortical bridging.

T he other parameter, endosteal healing, was definedas the gradual disappearance on obliteration of the frac-ture line and its replacement by a zone of increaseddensity formed by endosteal callus. T he amount of en-dosteal healing was quantif ied as none (no change in thefracture line compared with that on the post-reductionradiograph), initial (the fracture line had become lessdistinct), intermediate (there was marked consolidationof the fracture line), and complete (the fracture line hadbeen replaced by a zone of increased density formed byendosteal callus). A judgment as to the extent of endos-teal healing was made on both the antenopostenior andthe lateral radiographs at each follow-up visit.

T o minimize the effect of subjective interpretationof the radiographs by the individual investigators, allradiographs were assessed in independent, blind ne-views by the principal investigator (J. D . H .) and, sepa-rately, by the independent radiologist (R. F. K .). T heprincipal investigators assessment of radiographic heal-ing was used for purposes of statistical analysis to com-pare the efficacy of treatment with the results of use ofthe placebo device. T he site investigator s assessment ofclinical healing w as used for analysis of the clinical corn-ponents of fracture-healing. T ime to response w as cal-culated as the number of days after the fracture to thefirst occurrence of the specif ied event.

T he active and the placebo-treatment groups werecompared w ith regard to important characteristics ofthe fractures and patients. A statistical analysis7 was per-formed with use of the Fisher exact test (or the chi-square test if there w ere more than tw o category levels)for the sex of the patient; the grade, type, and location

(proximal, middle, or distal) of the fracture; the pres-ence of minor comminution; the presence of a butterf lyfragment; and the presence of a fibular fracture (T ableI ). S t a t is t ica l an a ly sis w a s p er f o r m ed b y t h e analysis ofvariance for the mean age of the patients in years, meanpre-reduction and post-reduction displacement, meanpre-reduction and post-reduction angulation in degrees,maximum fracture gap in millimeters, maximum lengthof the fracture in centimeters, mean number of daysafter the fracture before the start of treatment, meannumber of days of follow -up, and mean number of daysto the start of weight-bearing (T able I ).

Patient compliance was measured as the adherenceto the scheduled follow-up visits as dictated by the pro-tocol and the frequency of use of the device as measuredby the internal device clock and a w ritten log kept bythe patient. A dverse reactions, patients complaints, andcomplications were specifically sought by each site in-vestigator at each visit and w ere recorded if found.

Previous animal and clinical studies5 222 clearlyshow ed a positive effect of ultrasound on the rate ofosseous repair. T herefore, an accelerated time to heal-ing for the active-treatment group was hypothesized atthe protocol-design phase of this study. Consequently,one-sided statistical tests of hypothesis and one-sided pvalues were calculated to assess the superiority of treat-ment with the active device compared with treatmentwith the placebo, control device. T he null hypothesisthat the time to response for fractures treated with theactive device was the same or worse than the time toresponse for those treated w ith the placebo device wastested against the alternate hypothesis that the time toresponse w as superior for the fractures treated w ith theactive device. Superior was defined as an accelerated(shorter) time to the attainment of a specific healingresponse, such as a healed fracture status. T he result wassignificant when the p value was 0.05 or less in favor ofthe active-treatment group.

T hree statistical approaches are presented for all


6/10

30 J . D . H ECK M A N ET A L .

T H E JOURN A L O F BONE A ND JO I N T SURGER Y

T A BL E I I INUM B ER A ND CUMUL A TIVE NUMB ER OF FRA C TURES FOR DA YS

AFTER THE FR AC TU R E TO THE S TAR T O F W E IG HT -BEAR IN G

D ays after Fracture N o.Active

Cumulative No .Placebo*

Cumulative0 - 1 4 5 5 4 4

15-28 5 1 0 4 829-35 6 16 7 1536-49 3 19 5 2 050-63 7 26 5 256 4 - 7 7 3 29 1 26

> 77 4 33 7 33*No data were available on the start of weight-bearing for one

fracture in the placebo-treatment group.

analyses. A nalysis of variance was used to calculate themean time and the standard error of the mean, in days,to the attainment of a healed fracture status for theactive-treatment and placebo-treatment groups. A naly-sis of variance, K ruskal-W allis analysis of variance byranks32, and log-rank life-table analysis43t4 w ere used tocompare the mean times to healing for the two groups.T he K ruskal-W allis analysis was used because it doesnot make the statistical assumptions of a Gaussian dis-tribution or homogeneity of variances. T he log-ranklife-table analysis was used because it analyzes rightcensored observations as censored observations anduses days to the last follow-up visit as the time-to-eventvalue (one fracture that had active treatment and onethat had the placebo treatment had right censored esti-mated values for the time to a healed fracture).

I n addition, Cox regression analysis was used toassess whether potential covariates, such as the sexand age of the patient, the days to the start of weight-bearing, and the grade, type, or location of the frac-ture, had an effect on the healing response in the activecompared w ith the placebo-treatment group. I f an ef-fect w as observed because of the covariate, the resultsof active treatment compared with those of placebotreatment were statistically adjusted for the covariatein order to determine w hether the superiority of theactive-treatment group compared w ith the placebo-treatment group w as maintained in the presence of thecovariate effect.

A ll data observations were entered into a computerfile and then the computer printout w as proofread care-fully against the case-record form. A n independent, thor-ough comparison of all data used in the statisticalanalyses with those in the case-record form was donebefore the statistical analysis, to ensure the accuracy ofthe data further. A ll analyses were performed w ith theStatistical A nalysis System software (SA S I nstitute, Cary,N orth Carolina) on an I BM 3081 mainframe computer.

A ll of the fractures that were randomized into eachstudy group were analyzed for the time to healing in anintention-to-treat log-rank life-table analysis. Each frac-ture w as considered to be healed only at the time of a

scheduled follow-up visit (for example, at ten, twelve,fourteen, twenty, thirty-three, or fifty-two weeks) and nointerim visit (planned or otherwise) was used to assigna healing time. T he number of days to the last completedfollow-up examination was used for the time to healingfor the fractures that had not reached a healed status bythe last follow -up visit. T his intention-to-treat analysisevaluated w hether exclusion of the withdraw n and non-protocol-compliant patients biased the results obtainedin the analysis of the time that the fractures in the coregroup took to heal.

Resu l tsW ith regard to the seventeen patient and fracture

parameters that w ere studied (T able I ), w e could notdetect any appreciable differences between the thirty-three fractures in the active-treatment core group andthe thirty-four fractures in the placebo-treatment coregroup, with the numbers studied. T herefore, we believethat the placebo-treatment group was quite similar tothe active-treatment group.

T he patients compliance with the follow-up proto-col was analyzed by calculation of the ratio of actualclinical visits to the expected (scheduled) number ofclinical visits for each group. T he patients w ho receivedactive treatment returned for the scheduled follow-up visits 89 per cent of the time (245 of 276 visits), andthe patients who were treated with the placebo, 90 percent of the time (256 of 283 visits). U sage of the devicewas comparable between the active-treatment and theplacebo-treatment core groups, as recorded by both thedevice timer and the patient log, and all of the patientsin the active-treatment group used the unit for at leastthirty-six treatment sessions.

T he total duration of follow -up, in days, w as compa-rable in the active and the placebo-treatment groups; itwas 250 18.1 days (mean and standard error of themean [analysis of variance]) (range, ninety-two to 438days) for the active-treatment group compared w ith 284 19.2 days (range, 142 to 586 days) for the placebo-treatment group (p = 0.21) (T able I ). O ne patient in theactive-treatment group sustained a fracture in the samearea of the tibia seven months after the initial fracturewas considered to be healed both clinically and radio-graphically. T he second fracture occurred during a soc-cer game, from simultaneous kicks to the tibia by tw oother players. T his fracture healed four months later.

A subsequent, long-term follow -up w as done at therequest of the Food and D rug A dministration to deter-mine whether all healed fractures in both groups in thestudy remained healed at a minimum of tw o years afterthe injury. Fifty-f ive patients (f if ty-six fractures) of thesixty-six patients (sixty-seven fractures) who had beenenrolled in the protocol were contacted. A ll fifty-six ofthe fractures were still healed. T he duration of follow-upfor twenty-three fractures was more than four years andfor thirty-three fractures, it was two to four years.


7/10

N =33 N =34 N=33 N=34PR INC IPA L INVESTIGATO R INDEPENDENT RAD IO LOG IST

A CCEL ERA T ION OF T IB IA L FRA CTURE-H EA L ING BY NON -INV A SIV E, L OW -IN TENSITY PU L SED U L TRA SOUND 31

V OL . 76-A , NO . 1. JA NU A RY 1994

TA BL E IVSUMM ARY OF TH E C ox REGRESS ION ANALYSES FOR A SSESSM EN T OF TH E S IGN IF IC ANCE OF

POTENT IA L COVAR IA TES ON ThE T IM E TO A H EA LED FRAC tU RE

Potenti al C ov ari ateCore-G roup Fractures

L og-L ikel ihood Chi -Square P V al ue Signi f i cant CovariateSex 0.01 0.92 N oAg e 1 . 7 8 0 . 1 8 NoD ays to start of w eight-bear ing 4.55 0.03 Y esA dj usted di ff erence* 17.97 0.0001 -Fracture grade 1.38 0.24 NoType of f racture 0.10 0.76 NoL ocation of f racture 1.27 0.26 No* The act i ve compared w i th the placebo p value, w hen adjusted for the star t of w eight-bear ing, compared f avorably w i th the anal ysis of

v ariance and l og- rank p values of 0.0001.

A nal ysi s of vari ance show ed that the mean time tothe end-point of the study (a healed f racture), asjudged both cl i ni cal l y by the si te investigator and ra-diographi cal ly (three of f our bridged corti ces) by thepri ncipal i nvesti gator , w as 96 4.9 days f or the acti ve-treatment group compared w i th 154 13.7 days for theplacebo- treatment group (p < 0.0001 [analy si s of van-ance, K ruskal -W al l i s rank anal ysi s of vari ance, and log-rank l i f e- table analysi s] ) (Fig. 1). A t 120 days af terthe f racture, 88 per cent of the f ractures in the acti ve-treatment group w ere healed compared w i th 44 percent i n the placebo-treatment group; at 150 days, 94per cent of the f ractures i n the acti v e-treatment groupwere healed compared w i th 62 per cent in the placebo-treatment group (Fig. 2).

T he mean time to cl i ni cal heal i ng, as assessed bythe si te investigator, w as 86 5.8 days f or the acti ve-treatment group compared w i th 114 10.4 days f or theplacebo-treatment group (p = 0.01, 0.03, and 0.01 [anal -ysi s of variance, K ruskal -W al lace analy si s, and log-rankl i f e- table analysi s, respecti vel y ] ). T he mean time to dis-conti nuati on of the cast w as 94 5. 5 days for the acti ve-treatment group compared w i th 120 9.1 days f or the

placebo-treatment group (p = 0.008, 0.005, and 0.01).T he time to cl i ni cal heal i ng w as not recorded f or onepatient in the placebo-treatment group.

T he intermediate stages of radiographic heal i ngw ere determ ined by the principal i nvestigator for al lsi x ty -seven patients. A nal ysi s of v ariance of the time tocomplete heal i ng f or the f i rst, second, thi rd, and f ourthcorti ces demonstrated an increased rate of bridging inthe acti v e-treatment group compared w i th that in theplacebo-treatment group. There w as a signi f i cant in-crease (accordi ng to anal ysi s of v ariance, rank analy si sof vari ance, and log-rank l i f e-table anal ysi s) i n the d i f-f erences betw een the groups w i th regard to the numberof days af ter the f racture that br idging had occurred;these di f f erences w ere thi rty , f i f ty -ni ne, and si x ty -ei ghtdays for the second, thi rd, and f ourth corti ces, respec-ti vel y (Fi g. 3).

The radiographi c assessments of the principal i nves-ti gator and the independent radiologist f or the time tocorti cal bridging for three and four corti ces and the timeto complete endosteal heal i ng produced comparablestati sti cal resul ts, w i th the radiologist s assessments re-f lecti ng more conserv ati ve evaluati ons (Table I I ). T he

F IG . I

= S .E .M .. ACT IVEL I PLACEBO

Graph show ing the days to heal ing of the f racture (cl i nical l y and radiographical l y ) as assessed by the pr inci pal i nvestigator and theindependent radiol ogi st. S. E. M . = standard error of the mean.


8/10

L u-JLUI

LUI--I

U

% q q,c DA Y S TO HEA LING O F THE FR A C TUR E

FIG. 2G raph show i ng the cumulati ve percentage of cl in i cal l y and radiographical l y heal ed f ractures in the core group as a functi on of time. T he

super ior i ty of the act i ve-treatment group is seen, w i th 56 per cent of the f ractures healed compared w i th 18 per cent of the f ractures in thepl acebo- treatment group, at ninety day s af ter the f racture. One f racture i n the placebo-treatment group heal ed at 465 days af ter the f racture,and no cl ini cal data w ere avai lable for one f racture in this group. T he p value is for analysis of v ari ance, rank analy sis of variance, and l og- rankl i f e-table analysi s. SEM = standard error of the mean.

32 J. D . H ECK M AN ET A L .

THE JOURNA L OF BONE A ND JOIN T SURGERY

pr incipal i nvesti gator determ ined the time needed f orbr i dging of three corti ces to be 89 3.7 days for theacti ve-treatment group compared w i th 148 13.2 daysf or the placebo-treatment group (p = 0.0001 [ analy si s ofvariance, K ruskal -W al lace analy si s, and log-rank l i f e-table analysi s] ) , and the independent radiologi st s assess-ment was 102 4.8 days f or the acti ve-treatment groupcompared w i th 190 18.3 days f or the placebo-treatmentgroup (p = 0.0001 [ anal ysi s of vari ance, K ruskal -W al l aceanaly si s, and log-rank l i f e-table analy si s] ) .

The time to complete corti cal bridging (al l f our con-ti ces), as assessed by the pr incipal i nvesti gator, w as 114 7.5 days f or the acti ve-treatment group compared w i th182 15.8 days for the placebo-treatment group (p =0.0002, 0.0001 , and 0.0001 [ analysi s of variance, K ruskal -W al lace analysis, and log-rank l i f e-table analysis] ), andthe independent radiologi st s assessments w ere 136 9.6 days f or the acti ve-treatment group compared w i th243 18.4 days f or the placebo-treatment group (p =0.0001 [ analy si s of variance, K ruskal -W al lace analysi s,and log-rank l i f e-table analysi s] ) .

The time to complete endosteal heal i ng, as assessedby the pr incipal i nvestigator, w as 117 8.5 days f or theacti ve-treatment group compared w i th 167 13.9 daysf or the placebo-treatment group (p = 0.002, 0.0004, and0.0004 [ analysi s of var iance, K ruskal -W al lace analysi s,and log-rank l i f e- table analysi s] ) , and the independentradiologi st s assessment was 171 13.6 days for theacti ve-treatment group compared w i th 271 19.6 daysf or the placebo-treatment group (p = 0.0001 , 0.0001 , and0.0001).

A smok ing history w as obtained f rom thi r ty -sevencore-group patients (thi rty -eight f ractures). A mong thef ourteen f ractures in thi rteen patients who had never

A CTIVE (N=3 3)MEAN SE M96 4.9P LACEBO (N - 3 4 )MEAN SE M154 13 .7P V a Iu = O .0 0 0 1

T PLACEBO -.- ACTIVE

smoked, nine w ere treated w i th the acti ve dev i ce andhealed in a mean of 87 3.9 days, compared w i th 132 11.2 days f or the f i ve that w ere treated w i th the placebodev i ce (p = 0.002). A mong the f ractures in the remainingpatients, w ho w ere ex-smokers or who were smok ingduring the treatment per iod, eleven that w ere treatedw i th the acti ve dev ice heal ed in a mean of 115 11.2days, com pared w i th a mean of 158 28.6 days forthi rteen f ractures that w ere treated w i th the placebodev ice (p = 0.09).

A s mentioned prev iousl y , the only di f ference w i thregard to the management of the patients w as the timeto the start of weight-bearing. The justi f i cation for thecombinati on of al l core-group f ractures in the ef f i cacyanal ysi s w as the essenti al l y i denti cal pattern of f ractureand mean time af ter the f racture to the start of w eight-bearing in the acti ve-treatment and placebo-treatmentgroups (Tables I and I I I ) and on the stati sti cal analysi sby Cox regressi on of the ef f ect of the start of w eight-bearing on the ef f i cacy resul ts of the acti ve treatmentcompared w i th the placebo treatment. The Cox regres-sion analysi s establ i shed that w hen the acti ve-treatmentand the placebo-treatment groups w ere stati st i cal l y ad-j usted to a common start of weight-bearing ef f ect, theacti ve-treatment group maintained a si gni f i cant supe-niori ty f or the time to a healed f racture (p = 0.0001)(Table IV ). This resul t i s i denti cal to the p value of0.0001 i n the analysis of var iance, K ruskal -W al l is rankanal ysi s of vari ance, and log-rank l i f e-tabl e anal ysis (Fi g.1) and conf i rm s that the day that w eight-bear ing starteddid not signi f i cantl y af f ect the ef f i cacy resul ts of time toa healed f racture.

I n addi ti on, the Cox regression analysis establ i shedthat other cl i ni cal l y relevant covaniates, such as the sex


9/10

COR TE XBRIDGED

4T H -

3R D

2N D

1S T -89 3.7

86 3.9

p VALUE0.00020 . 00010 . 0001

0 . 00010 . 00010 . 0001

__x -11 4 . -. - 1 8 27 .5 .---.- 158

- .x.- 14 8- 13.2

13 .1

3 .9

0.020.050 . 01

- A CT IV E (NXPLACEBO (N -34(

0.10.50.2

70 80 90 100 110 120 130 140 150 160 170 180 190DAYS AFTER THE FRACTURE

F IG . 3

A( ( ELERAT ION OF T IB IA L FRA CTURE-H EA L ING BY NON -INV A SIV E. L OW -IN TENSITY PU L SED U L TRA SOUND 33

VOL . 76-A, NO . I. JA NU A RY 1994

Graph showing the rate of progression of heal i ng by the amount of cortex bridged. The values are gi ven as the mean and the standard errorof the mean. P values are gi ven f or analysis of v ariance, rank analysis of v ariance, and log-rank l i f e-table analyses.

and age of the patient and the grade, ty pe, and locationof the f racture, al so had no signi f i cant ef f ect on theef f i cacy resul ts of time to a healed f racture (T able IV ).

L og-rank l i f e- table analysi s w as used in an intention-to-treat anal ysis f or al l f ractures randomized into thestudy . T he time to a healed f racture w as signi f i cant f orthe acti ve-treatment group at the 0.005 probabi l i ty l evel ,which compares favorabl y w i th the analysi s of variance,K nuskal -W al l i s, and log-rank p values f or time to a healedf racture in the core group. T his resul t conf i rm s the val i d-i ty of the use of the core group of protocol -compl iantpatients f or cl i ni cal and stati sti cal inf erences.

There w ere tw o adverse reactions and one compl i -cati on i n the si x ty -si x pati ents i n the core group. Onepatient (w ho had acti v e treatment) reported muscle-cramping at one week . T he cramping resol ved, w i thouttreatment, by the second w eek . One patient (w ho hadplacebo treatment) had sw el l i ng in the cast at the six -week f ol low -up v i si t. T hi s problem had resolved bythe nex t v i si t. N o other adverse reactions were reported.One patient who used a placebo dev ice had a pul -monary embolus at the f our-w eek fol l ow -up v isi t. T hepatient w as managed successful l y w ith anti coagul anttherapy and remained in the study .

DiscussionThe intri gui ng cl i ni cal f i ndi ngs of X av ier and D u-

ante2, supported by placebo-control l ed animal studiesby D uarte and by Pi l l a et al ., demonstrated that ul tra-sound accelerates the normal f racture-repai r process indiaphy seal bone. T hese f i ndings l ed us to design a pro-spectiv e, random ized, doubl e- bl ind, pl acebo- contr ol ledstudy to assess both the saf ety and the ef f ecti veness ofthe use of l ow -i ntensi ty ul trasound to accelerate heal -

i ng of f resh f ractures in humans. T he random izationprocess created tw o very sim i lar groups of patients andtherefore perm i tted an unbiased assessment of the ef -f ect of the acti ve-treatment dev i ce. W hen these tw ogroups w ere compared, the time to a healed f racturew as found to be signi f i cantl y accelerated w hen theacti ve-treatment dev ice w as appl ied for one tw enty -minute period each day for as many as tw enty w eeksi n the immediate post-f racture period in patients w hohad a closed or grade-I open tibial diaphyseal f racture.

The treatment regimen w as tolerated w el l by thepatients, and no serious compl i cati ons attr i butable tothe treatment w ere identi f i ed. N o pati ent had notice-able edema at the si te of the w indow or sk in i rr i tati onas a consequence of use of the dev ice. The patientsfound the portable uni t easy to use and were able toachieve adequate coupl i ng contact betw een the sk inand the treatment head surface. No speci f i c mechanicalor technical problems w ere encountered during thestudy.

The speci f i c mechanism by which low -intensi typulsed ul trasound accelerates the normal diaphysealf racture-repai r process is unknow n. T he present studydoes not address thi s question. O ther authors have re-ported on bi ological ef f ects caused by stati c mechani -cal f orces and by the pressure w aves of ul trasound smechanical perturbation2 7. These pressure w aves maymediate biological acti v i ty di rectl y by mechanical de-f ormation of the cel l membrane or i ndi rectl y by anelectr i cal ef fect caused by cel l deformation.

K nisti ansen reported on the accelerati on of the timeto a healed f racture and on other radiographi c parame-tens of heal i ng of metaphyseal bone in a sim i lar double-bl ind, random ized, pl acebo-control led study w i th use


10/10

34 J . D . H ECK M A N ET A L .

TH E JOU R N A L OF B ON E A N D JO IN T SU R GERY

of the same ultrasound treatment on Colles fractures. W e believe that additional clinical corroboration of theK noch and K iug reported an increased rate of healing acceleration of healing of fresh fractures with use ofof fractures at various locations in humans with use of specifically programmed, pulsed, low-intensity ultra-ultrasound treatment with signal intensities that were sound treatment may lead to its useful application in theone order of magnitude more than the signal intensities treatment of fractures.used in the present study.

Beyond the preliminary clinical studies of X avier N oi T he authors thank the follow ing site i nvestigators: W . C . Brady. D . Cahorn. K .1 Ch i l l a g . R . M. C hris tia n. J . C ro nk ey . J. R . D eA nd ra d e. J . W . D unlap. Jr.. D . N. Ervin. J.and D uarte---, K nlstlansen, and the present study, we Gam wel l . R . G ar land . M . lu s m. T . K r ist i an sen . P . E . L ev in, T . M cE ll i got , M . C . M eier . D . G .

are not aware of any other studies that document the T hca sal I hank Kerneffectiveness of low-intensity pulsed ultrasound in the Char les. R oger T al i sh. and A r th u r L ifshey for t hei r engineer i n g ass st an ce and t he late Saw nie. , . . G as to n. M .D .: A rt h u r Pilla. Ph.D.: J am es R yabs. Ph .D .: and Rober t Si f fer t . M .D . for t h ei racceleratlon of the fracture-healing process in humans. in vU ua ble c ou ns el du r ing the p r epar at i on of th i s st ud y .

References1 . B i nd er ma n, I .; Z or , U .; K aye, A . M .; Sh im shon i , Z .; H ar el l , A .; an d Som j en , D .: T h e t r an sdu ct i on of m echan ical f orce i nto bi om echani cal

events in bone cells may involve activation of phospholipase A 2. C alc if T issu e In tern a t., 42: 261-266, 1988.2. Chapm an , I . V .; M acN al l y , N . A .; an d f l i ck er , S.: U l t r asoun d- ind uced changes in rates of influx and eff lux of potassium ions in rat

thymocytes in vitro. U ltra sou nd M ed . an d B io l ., 6: 47-58, 1980.3. Conover, W . 3.: P ra ctic a l N on param etr ic S ta tist ics. Ed. 2. N ew Y ork. W iley, 1980.4. Cox, D . R .: R egr essi on models and life-tables. J . Ro y. S ta tis t. S oc . , S er ies B , 34: 187-220, 1972.5. D uane, L . R .: T he stimulation of bone growth by ultrasound. Arch . O rth op . an d T raum a Su rg . , 101: 153-159, 1983.6. Dyson , M : T h er apeu t ic applications of ultrasound. I n B io log ica l E ffec ts o f U ltrasoun d , pp. 121-133. Edited by W . L . N yhorg and M . C.

Ziskin. N ew Y ork, C hurchill L ivingstone, 1985.7 . F lei ss, J. L .: S ta tis tica l M eth ods for R a tes an d P rop ort ion s. Ed. 2. N ew Y ork, W iley, 1981.8. Gust i l o, R . B ., and A nder son , J . T .: Pr even t ion of in fect ion in the treatment of one thousand and twenty-five open fractures of long

bones. R etrospective and prospective analyses. J . B one an d Jo in t S urg ., 58-A : 453-458, June 1976.9. M ug, W .; F r ank e, W . G .; an d K noch , H . G .: Scin t igr aph ic con t r ol of bone-f r actu r e healing under ultrasonic stimulation: an animal

experimental study. Europ ean J. N u cl. M ed ., 11: 494-497, 1986.10. K noch , G . H ., and K lu g, W .: S tim u la t ion o fF racture H ea ling w ith U ltrasou nd , translated by T . C. T elger. B erlin, Springer, 1991.1 1 . K ristiansen, T . K .: T he effect of low power specifically programmed ultrasound on the healing time of fresh fractures using a Colles

model. J . O rth op . T raum a, 4 : 2 2 7- 2 28 , 1990.12. L ehmann, E. L .: Nonpa ram etric s: S ta tist ica l M e tho ds Based on Ran ks. San Francisco, H olden-D ay. 1975.13. M antel, N .: Evaluation of survival data and tw o new rank order statistics arising in its consideration. Cance r C h em o the r. R ep ., 50:

1 63 - 17 0, 1 96 6.14. M antel, N .: R anking procedures for arbitrarily restricted observation. Biometrics, 23: 65-78, 1967.15. N ybor g, W . L .: M echan ism s. I n B io log ica l E ffec ts o f U ltraso un d , pp. 23-33. Edited by W . L . N yborg and M . C . Z iskin. N ew Y ork.

Churchill L ivingstone, 1985.16. Pi l la , A . A .; M on t , M . A .; N asser , P . R .; K han , S. A .; F i guei r edo, M .; K au fm an , J . J .; and Si f f er t , R . S.: N on-invasive low -intensity pulsed

ultrasound accelerates bone healing in the rabbit. J . O r tho p . T raum a, 4: 246-253, 1990.17. Ryaby , J . T .; M ath ew , J .; P i l l a, A . A .; and D uar te-A l ves, P .: L ow -in ten si t y pu lsed u l t r asoun d modulates adenylate cyclase activity and

transforming grow th factor beta synthesis. I n E lectrom ag net ics in M ed ic in e an d B io log y , pp. 95-100 . Edited by C. T . Brighton and S. R.Pollack. San Francisco, San Francisco Press, 1991.

18. Schef fe, H .: T he A na lysis o f Va rian ce . N ew Y ork, W iley, 1959.1 9 . St . John B r ow n , B .: H ow saf e is di agnostic ultrasonography ? Canad ian M ed . A ssn . J ., 131: 307-311, 1984.20. W el ls, P . N . T .: Surgical applications of ultrasound. I n B io log ica l E ffe c ts o f U ltrasoun d , pp. 157-167. Edited by W . L . N yborg and M . C .

Z iskin. N ew Y ork, Churchil l L ivingstone, 1985.21. X av ier , C . A . M ., an d D uar te, L . R .: E st im u lac#{ 227} u l t r a-son ica de cab osseo: applicac#{226} clinica. R ev. B ras i/e ira O rto p ., 18: 73-80, 1983.22. X avier, C . A . M , and D uarte, L . R.: T reatment of nonunions by ultrasound stimulation: f irst clinical applications. R ead at the M eeting of

the L atin-A merican O rthopedic A ssociation, at the A nnual M eeting of T he A merican A cademy of O rthopaedic Surgeons, San Fran-cisco, California, Jan. 25, 1987.

23. Z isk in , M . C .: A pp l i cat i ons of u l t r asoun d i n m edi ci ne - comparison w ith other modalities. In U ltrasoun d: M ed ica l A pp l ica tion s,B io log ica l E f fec ts, a nd H azard Po ten tia l, pp. 49-59. Edited by M . H . R epacholi, M . G randolfo, and A . Rindi. N ew Y ork, PlenumPress, 1987.

Heckman JD, Ryaby JP, McCabe J, Et Al. Acceleration of Tibial Fracture Healing by Non Invasive,...

Documents

Transcript of Heckman JD, Ryaby JP, McCabe J, Et Al. Acceleration of Tibial Fracture Healing by Non Invasive,...