Endoscopic microsurgery in herniated cervical discs AndreaFontanella Depaftment of Neurosurgery, Hospital ,Cittä di parma,, parma, ltalv The purpose of this study was,jo make public our resultsusing endoscopic microsurgery in herniated cervical discs' This technique allows us to'avoid complications aä to iirr"ntional expoiur|, as is thte case in traditional approaches. T!,is.study wa.s carried ou.t'from January tggl-io'i"rr^ry | 99g. one hundredand seventy-one patients should have undergone traditional tyrgui for 296 herniated cervicaldisls. They were, instead, treatedbLu:,ng endoscöpic.microsu.rgica! iurhniqrii tn 223 herniationsthe surgical procedure waspefformed by a iaramidlin'e right anteriir approach, ändin 23 herniatiotnts iy ^'p,iu-Äiatir" posterior approach, with a workingsleeve of 2.6 mm outer äiametör in boti cases. ln the uit*'[o, ipprourn the tu,be ,was firmly placed lsains{1he anterior longituctinat ligaÄ"it ^rlit'n" edge of the anterior pili of the vertebral bodies. The neurovascular structures wdre placed"lat"ru! i tni iorling sleeveand th" iirr"rrl structures wereplacedmedialto the, working sleeve.' Then, under endoscopic ciaxial.contro!, removal of the herniated paft.w1speiormed, through ihe intervertebral discs, with mlicrosurgical instruments. ln the posterior approach,the tu.be.was plac.edinstead between theinferior and superior lamina,then under the nerveroot up to the herniation,which was removecl. This posterior approac'h was used only in ti"-iut"ral disc herniations' There were^1o-jlcidgnts.or maior .cöm-plications räitoiing these operations. After one month the success rate was 94.7%, after threemonths gi.sr, after six ^init,, ga.q,i" ani afte,ir" y.u, 97%' There wereno cases o.f,relapse during thefollow-up p"i"i ir tnite'"patients. rni, stiay sigj"rt, tt,"t for herniated cervicaldiscs,the.eÄdoscopiä microsurgicu't i"in:,i,quu'ii "i {i,u-"ty advantageous and safe method. M9reoy9r, tonger fotlow-.upperiods and-an increasädnu^aui "i'p;;r;;;; ä;;;-,üiin ,ni, procedure shouldfurther confirm the u'sefulness of this techniqr". fNi;r;i Res 1999;21: 31-3Bl Keywords:Cervical vertebrae; intervertebra! disk displacement; ntyelopathy; spine; neurosurgical treatment; endoscopy INTRODUCTION Cervical myelopathy and/or cervical radiculooathv caused by compressive lesions from herniated cervicjl ltsc. hal been surgically treated either by a posterior laminectomy or by an anterior approach with oi without Interbody fusion.The posterior approach was first oes '?ed in 1950 by Spurling and Scoviller to lreat prtmarily laterally displaced discherniation. lt has been used less frequently since the development of the anterior. approac.h to the cervical spine2?. positioning l!1, n"1i"1't in, the prone position, the complication! assocrated with posterior approach includenerveroot 11111, prrtjgularly when more thanone rooris exposed, ilj,l.ul,.old injurysecondarv to cord retraction, particu- larl) during. transdural approach to a herniated disc, sprn.' instability, particularly. when the facet joint is IlTi""9,_i"d posterior muscle trauma and injury.For :ne past 30 years, the anterior approach has'betome very popular. Three co^mmon techhiques of fusionare oescribed, by,Clowa,rd2,s,u, Bailey and Badgleyr, ;; )mrtn and Robinsona. In Cloward,s tOSapLibliäation2, he described hisoperative techniquL. i-,e cämplicationi associated with thä anterior approach i".f rJ" in juries to the spinal cord, the nerve roots7,8, the veftebralartery, the sympathetic chain and the anterior soft tissue structures,such as the esophagus, carotid artery, llr.h:9, recu.rrent .laryngeal nerve änd, very rarely, the thyroid gland. Wirh rhe anterior approach at the ör_T, level, injury to the dome of the öärietal pleura of the lung with secondary pneumothoiax is a bossible risk. When fusion is performed, in the immediate Dost_ operative period, graft extrusion should oc.urn. öser_ doaft.hrosis may be presentafter a one-segment fusion, but this d_oes not necessarily preclude a äood clinical outcomelo'1t. Other compliiations, typicaiof the fusion with au.tograft, are represented by the'ihjuryto the lateral femoralcutaneous nerve, hematoma,iliac wing fracture and post-operative wound infection10,l2. When"allograft is used to make the fusion, transmission of communic- able diseases is possible. When fusion is performed, the inevitable stresses applied to adjacent interspaces are present. This increasesthe probability of disc herniätions and/or degenerative changes in the adjacent interspaces. Kyphoticdeformity, developing long-termsecond'ary to an anteriorcervical discectomy with or without fusion. may be present.Scar tissue formation in the cervicai spinalcanal and/or in the foraminamay develop in all the cervical spinal surgery and particularly in the posterior approach. Taking into considerati'on these llrrespondence " reracani 12, 431oo parma, ttaly. Ä..uptJ for'frbl;r;;" April 1998. EJ,'1'. i3Än1'rä:iri sh i n g c rouP Neurological Research,| 999, Volume 2l , Januarv 31
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Endoscopic microsurgery in herniatedcervical discs
Andrea Fontanella
Depaftment of Neurosurgery, Hospital ,Cittä di parma,, parma, ltalvThe purpose of this study was,jo make public our results using endoscopic microsurgery in herniatedcervical discs' This technique allows us to'avoid complications aä to iirr"ntional expoiur|, as is thte casein traditional approaches. T!,is.study wa.s carried ou.t'from January tggl-io'i"rr^ry | 99g. one hundred andseventy-one patients should have undergone traditional tyrgui for 296 herniated cervical disls. Theywere, instead, treated bLu:,ng endoscöpic. microsu.rgica! iurhniqrii tn 223 herniations the surgicalprocedure was pefformed by a iaramidlin'e right anteriir approach, änd in 23 herniatiotnts iy ^'p,iu-Äiatir"posterior approach, with a working sleeve of 2.6 mm outer äiametör in boti cases. ln the uit*'[o, ipprournthe tu,be ,was firmly placed
lsains{1he anterior longituctinat ligaÄ"it ^rlit'n" edge of the anterior pili of thevertebral bodies. The neurovascular structures wdre placed"lat"ru! i tni iorling sleeve and th" iirr"rrlstructures were placed medial to the, working sleeve.' Then, under endoscopic ciaxial.contro!, removal ofthe herniated paft.w1s peiormed, through ihe intervertebral discs, with mlicrosurgical instruments. ln theposterior approach, the tu.be.was plac.edinstead between the inferior and superior lamina, then under thenerve root up to the herniation, which was removecl. This posterior approac'h was used only in ti"-iut"raldisc herniations' There were^1o-jlcidgnts.or maior .cöm-plications räitoiing these operations. After onemonth the success rate was 94.7%, after three months gi.sr, after six ̂ init,, ga.q,i" ani afte, ir" y.u,97%' There were no cases o.f,relapse during the follow-up p"i"i ir tnite'"patients. rni, stiay sigj"rt, tt,"tfor herniated cervical discs, the.eÄdoscopiä microsurgicu't i"in:,i,quu'ii
"i {i,u-"ty advantageous and safemethod. M9reoy9r, tonger fotlow-.up periods and-an increasäd nu^aui
"i'p;;r;;;; ä;;;-,üiin ,ni,procedure should further confirm the u'sefulness of this techniqr". fNi;r;i Res 1999;21: 31-3Bl
Keywords: Cervical vertebrae; intervertebra! disk displacement; ntyelopathy; spine; neurosurgicaltreatment; endoscopy
INTRODUCTIONCervical myelopathy and/or cervical radiculooathvcaused by compressive lesions from herniated cervicjlltsc. hal been surgically treated either by a posteriorlaminectomy or by an anterior approach with oi withoutInterbody fusion. The poster ior approach was f i rstoes '?ed in 1950 by Spurl ing and Scovi l ler to l reatprtmari ly lateral ly displaced disc herniat ion. l t has beenused less frequently since the development of theanterior. approac.h to the cervical spine2?. positioning
l!1, n"1i"1't in, the prone position, the complication!assocrated with posterior approach include nerve root11111,
prrtjgularly when more than one roor is exposed,ilj,l.ul,.old injury secondarv to cord retraction, particu-larl) during. transdural approach to a herniated disc,sprn.' instability, particularly. when the facet joint isIlTi""9,_i"d posterior muscle trauma and injury. For:ne
past 30 years, the anterior approach has'betomevery popular. Three co^mmon techhiques of fusion areoescribed, by,Clowa,rd2,s,u, Bai ley and Badgleyr, ; ;)mrtn and Robinsona. In Cloward,s tOSa pLibl iäat ion2,he described his operative techniquL. i-,e cämplicationiassociated with thä anterior approach i".f rJ" in juries to
the spinal cord, the nerve roots7,8, the veftebral artery,the sympathetic chain and the anterior soft t issuestructures, such as the esophagus, carot id ar tery,
llr.h:9, recu.rrent .laryngeal nerve änd, very rarely, thethyroid gland. Wirh rhe anterior approach at the ör_T,level, injury to the dome of the öärietal pleura of thelung wi th secondary pneumothoiax is a bossib le r isk.When fusion is performed, in the immediate Dost_operative period, graft extrusion should oc.urn. öser_doaft.hrosis may be present after a one-segment fusion,but this d_oes not necessarily preclude a äood clinicaloutcomelo'1t. Other compliiations, typicaiof the fusionwith au.tograft, are represented by the'ihjury to the lateralfemoral cutaneous nerve, hematoma, i l iac wing fractureand post-operative wound infection10,l2. When"allograftis used to make the fusion, transmission of communic-able diseases is possible.
When fusion is performed, the inevitable stressesapplied to adjacent interspaces are present. Thisincreases the probabil ity of disc herniätions and/ordegenerative changes in the adjacent interspaces.Kyphotic deformity, developing long-term second'ary toan anterior cervical discectomy with or without fusion.may be present. Scar tissue formation in the cervicaispinal canal and/or in the foramina may develop in a l lthe cerv ica l sp inal surgery and par t icu lar ly in theposterior approach. Taking into considerati 'on these
llrrespondence "reracani 12, 431oo parma, t taly. Ä..uptJ for ' frbl;r ; ;" Apri l 1998.
E J,'1'. i3Än1'rä:iri sh i n g c rouPNeurological Research, | 999, Volume 2l , Januarv 31
Endoscopic
complications and thä outcomes in the open spinalsurgery, we used 'closed' surgical techniques. Withminimally invasive spinal neurosurgery the trauma forthe patient in the surgical area is minimised, andconsequently iatrogenic öffects may be avoidedl r. Theseclosed techniques took r ise from the associat ion of manydifferent procedures used in neurosurgery. Stereotaxywas the f irst step towards minimally invasive neuro-surgery. Subsequently, the introduction of the operatingmicroscope permitted reduction of surgical f ield withconsequent improvement of surgical techniques, to thepatient's benefit. Furthermore, the development of'neuroimaging methods' l ike CT and MRl, revolut ionised
32 Neurological Research, 1999, Volume 21, January
A
Figure .l:
During surgery, in the AA, the patient is placed in the supine position. A: Anterior part of the neck with ananterior posterior projection of the ceruical spine; the midline and the level of the disc herniation has ben drawn on theskin. 8: Lateral view of the patient on the operating table. A pil low is placed under the patient's neck to maintainphysiological cervical lordosis and the patient's face is kept straight. A blunt obturator can be seen firmly placed againstthe anterior longitudinal l igament and the edge of the anterior part of the adjacent vertebral bodies, at the appropriateinteruertebral level
Figure 2: A trephine is inserted in the working sleeve and carefully advanced in intervertebral späce up to the herniation.In these fluoroscopic views it is possible to see A: an anterior posterior projection and B: a lateral projection of theceruical spine with the working sleeve and the trephine
neuroradiologic diagnostics, permitt ing precise surgicalplanning and three-dimensional programming. The useof the computer applied to surgery, the so called'neuronavigator ' has yielded high precision surgicaltechniques, and can be l inked with very sophist icatedcontrol systems, such as intra-operative echography,intra-operative CT or intra-operative MRl, to achieve theoptimum therapeutic effect with the minimum surgicaltrauma. More recently, endoscopes, i .e. optic instru-ments capable of transferr ing images from one place toanother (from an area inside the body to the outside) andl inked with microcamera systems, have been consider-ably improved and al lowed the beginning of the
Endoscopic microsurgery in herniated certical discs: Andrea Fontanella
Figure 3: Schematic draw-ings of the anatomy ofthe neck in axia l sect ion.A: A trephine inserted inthe working sleeve up tot h e h e r n i a t i o n . B : T h em ic roendoscop i c canu lainserted in the tube wi than ang led m ic ro fo r cepsremov ing t he hc rn i a tedpart
Figure 4 A: Fluoroscopic view of microforcepsremoving the herniation. B: The microforcepsin use
Figure 5 A: Microscissors used to separate thedural sheath from the underlying herniated partand reactive adhesions. B: The microscissors inuse
B
Neurological Research, 1999, Volume 21, January 33
Endoscopic microsurgery in herniated ceruical discs: Andrea Fontanella
sophy, k'eyhole surgery was- developed. This techniqueenabied the surgeoä to reach the surgical target throughstereotaxic method, and perform the intervention bymeans of endoscopic systems r-rsing part icular. probes,
the so-cal led 'working sleeves"' . Our personal experl-
ence in the f ield of keyhole neurosurgery began in 1989
and we introduced this technique in the cervical spine in
January 1991, using either anterior approach or, less
irequently, posterio'r approachl o. Endoscopic micro-
neurosurgery al lows us to easi ly reach and expose the
herniated"part which can be removed with great faci l i ty,
of the operation with somatosensory and motor evoketpotentials may be helpful. Al l the operative technique
must be fol lowed careful ly, step by step' The operatin;
surgeon must be properly lrained in these endoscopi '
tecEniques. In the'PA the patient is placed in the pron'
oosit ioÄ on the operating table with the neck sl ightl
i lexed. Before makine a skin incision, a lateral f luorc
scopic image should be obtained to verify the exa<
intervertebäl level. Then, a very small incision, less tha
5 mm long, is made over the ligamentum flavum at th
.orru.t uött"bral space, in paiamidl ine area'.A blur
obturator is introduced first in dorsal fascia, and then, iparasp ina l musc les up to the l igamentum f lavun
Successively the working sleeve is - introduced anthus reducing the r isk of complications. With thistechnioue i t i i oossible to avoid the formation of pos!technique i t is possible to avoid I postoperative scar t issue and secondary iatrogenic events,such as rerlehral instabi l i ly. Therefore interbody fusionis not required and, thus, the patient is immediatelymobil ised a{ter surgery.
MATERIALS AND METHODSThis study was carr ied out from January 1991 to January' l 998. One hundred and seventy-one patients should
have undergone tradit ional surgery for 296 herniatedcervical disis. Al l patients had symptoms of cervicalmyelopathy and/or 'radiculopathy. They were, instead,treated by using the endoscopic microsurgical tech-niques. ln 148 pätients with 273 herniat ions, the surgicalprocedure was.performed by a paramidl ine r ight anteriorapproach (AA, while in 23 patients with 23 herniat ionsby a paramid l ine pos ter io r approach (PA) . Pre-
operatively al l patients had plain f i lms and magneticresonance imaging (MRt) (Figures BA, 104) and thepalients with böny changes had computed tomography
iCT) r.unr Gigure 9A) with or without associatedmyelography (mielo-CT). Ninety-eight of these 17i
oatients weie males, while 73 were females. Average
age was 45 years. The youngest subject was 1 6-years-o"ld and the oldest was B5-years-old. Six patients hadfour herniations, 27 patients had three, 53 patients hadtwo, while 85 had only one herniat ion. The herniatedcervical disc was at the C2-C3 level in four cases, at theC3-Ca level in 28 cases, at the Ca-C5 level in 56.cases,aithe C5-C6 level in 99 cases, at the C6-C7 level in 91
cases, and at the C1T1 level in 1 B cases. These surgicaltechniques were studied and practised over a longperiod bf time on cadavers, before they were applied tobatient care. When in cervical disc herniat ion there was
iai lure of nonoperative management, progressive neu-rological defici t or myelopathy, operative. interventionwas*considered: these patients were included in the
Dresent studv. We used for the first time endoscopic*icrosrrgetf with posterior approach for far lateral disc
herniat ioä when there was no imbrication of adiacentlamina. We used endoscopic microsurgery with anterior
aoproach in the other cases. In recent years we were
iÄi l ined to use instead only anterior approach' ln both
techniques we administered prophylactic. antibiot ictreatment and surgery was performed under.generalendotracheal anesthesia, sometimes in neÜrolept an-algesia with local anesthesia. In some cases, monitoring
34 Neurological Research,1999, Volume 21, January
ided bv'the blunt obturator unti l i t reaches thgu logo Dy Ine D lun I o ( ) l ' u ld tu l u t r t r r r t
igamentum f lavum, which. is passed using a sma
, r , , ' : ii : - t : f:T:;l-:
,ir i .
täphine passing through the working sleeve' Ther
,rins u fine bllnt instiument, palpation beneath tl'
nervä root is done from both above and below, undr
endoscopic control, which is obtained by a microend<
scopic r igid or f lexible canula, previously inserted in t f
*oiking'.un"l. Bleeding from epidural veins can I
control led with t iny cofton pledgets. During surgerirr igation and suction in the operating f ield are achievt
by"suitable microinstruments. A bipolar coagulat icmicroelectrode must be avai lable, i f required. l t
important not to cause pressure on the dural sheat
anä greal care is necessary in separating the dural slee'
of thä nerve root from the underlying herniated disc ar
reactive adhesions (Figure 5. The nerve root is th(
retracted superiorly (Sometimes inferiorly), thus t l
herniated part can be removed using different micr
instruments, such as microforceps (Figure 4), micr
scissors (Figure 5, microknives of different shaptmicroprobei Gieure 6i), microhooks, and microresectoIt is important tö verify that the nerve root is complete
decombressed and mobile by following the nerve rc
out latöral ly and medial ly, using microhooks graduat
in dif ferent 'ways (Figure '6)
andluitable f lexible or r i1
endoscope. In this phase, del icate movements ;
required to avoid iniury to the nerve root and to t
duial column. A drain is not necessary using endoscolmicrosurgery. In the AA the patient is placed in t
supine päsi i ion, a pi l low is pLaced under the neckrnäintain physiological cervical lordosis, and the ;tient's face is keptitraight Gigure lB). The arms shor
be placed at the i ide, pül led distal ly and held in place
faci l i tate posit ioning of the surgeon and obtaining int
operative f luoroscöpic imagei. The midl ine and t
intervertebral level of the herniat ion are then drawnthe skin of the neck under fluoroscopic control (Frg
1A). A very small incision, less than f ive mil l imetersmade vertically at the correct intervertebral sPace,the r ight side, about 15mm from the midl ine. Iplatvsäa muscle is also incised in the entire width of
skin' incision. A blunt obturator (Figure I B), is introdu<
through the skin and the platysma muscle. After incis
of the pre-tracheal fascia, which is. ope.ned just.ante
to the sternocleidomastoid muscle, the subplatysr
dissection can be done. Using a blunt obturator,strap muscles, the trachea and the esophagus
Figure 6A: Fluoroscopic view of microprobe angled at 45 degrees used to verify that the nerve root and spinal cord arecompletely decompressed and mobile. In this phase, delicate movements are required to avoid injury to the spinal cord,the nerve root and the dural sheath. B: The microorobe in use
tndoscopic microsurgery in lrcrniated cervical discs: Anclrca ['ontanella
RESULTSIn this study we considered success as the disappear-ance or the improvement of patient's rynptoms, such asmyelopathy, radiculopathy or neck pain. In our s tudythere were nei ther inc idents dur ing surgery, nor majorcompl icat ions fo l lowing these operat ions. The per iod offo l low-up ranged f rom 12 months to 84 months. Pat ientswere examined one month, three months. s ix monthsand one year after surgery, and thereafter on a yearlvbasis . No pat ient exper ienced re lapse fo l lowing opera-tion in this study period. After one month the successrate was 94.7% (162 of the 17'l patients), after threemonths 95.9% (164 of 171) , af ter s ix months 96A% (165of 171), after one year 97.0o/o (166 of 171\ (Figure 7\.We saw the same results after a period of longer thanone year. In this study there were three patients with alarge and lateral herniation compressing the vertebralartery. In these three patients the symptoms correlatedwith vertebral artery compression disappeared aftersurgery. In our series of patients disc space narrowingwas not present in the subsequent radiographs of all thecases operated either with AA or PA. In the dynamicv iew radiographs, the mobi l i ty of cerv ica l sp ine inflexion, extension and in lateral bending was completelypreserved, as with previous surgery. Kyphotic changeswere never noted in the time using this endoscopicmicrosurgery. The MRI and CT post-operative controlsdemonstrated a comolete removal of the herniations(Figures 8-10).
D ISCUSSION AND CONCLUSIONThis study suggests that for hern iated cerv ica l d iscs, theendoscopic microsurgical technique is an extremely
retracted medially, while carotid sheath is held laterally.The working sleeve is then introduced and guided by theblunt obturator unti l i t reaches the or€vertebräl fascia.rvhich is opened by a small microknlvä At this point the
ork ing canal is p laced against the anter ior longi tudinal, ,gament and the edge of the anter ior par t of the ad jacentver tebra l bodies. An appropr iate s ized t rephine isinserted in the working sleeve and carefully advancedin intervertebral space up to the herniation (Figures 2and - lA) . Using a microendoscopic r ig id or f lex ib lecanula for endoscopic control, the herniated part can beremoved (Figure 3B). Many instruments may be used,
rch as various types of microforceps, for exampleirpwards, downwards, straight (Figure 4), and flexible,several types of microknives, microscissors (Figure 5,microprobes (Figure 6) and microhooks, with differentangulations, and various microresectors. During surgery,as well as PA, irrigation and suction in the operatingfield are necessary and a bipolar microelectrode must beavailablel3. No ionclusive evidence exists for removaloi all osteophytes from the posterior part of vertebral, : iy or_ for removal of the posterior longitudinall igamentl0,ls-22. We believe that it is important toremove only the part of the osteophytes'which iscompressing the nerve root and/or the spinal cord. Asmal l and lengthened h igh-speed dr i l l wi th d iamond bi tand curettes of different sizes and shapes, are used toremove osteophytes. The drain is not used. The patientcan be up 20 h after surgery and be discharged within a' j v or two. He is p laced in a cerv ica l co l lar when he isii; i in bed, for four weeks after surgery. Activit ies arel imi ted in the f i rs t weeks. There is a fu l l resumpt ign ofact iv i t ies, inc luding work, wi th in four weeks.
Endoscopic microsurgery in herniated cervical discs: Andrea Fontanella
Figure 7: Changes over time in success rates (green) and failuie iutei (r"dl in the present study. After one month thesucccss ra tewasg4 .T "ß (162o f t he171 pa t i en t s ) , a f t e r t h reemon ths95 .97 . (16ao f 171 ) , a f t e r s i xmon ths96 .a%(165o (171), af ter onc year 97.O% (166 of 17' l ) . Wc saw the same rcsul ts af ter pcr iods of longer than one year
A
Figure I A: MRI v iew of a pat ient wi th a d isc herniat ionremoval of the herniated part
36 Neurological Research, 1999, Volume 21, January
B
at Cs-C6 level . B: Post-operat ive MRI conf i rms a complete
Endoscopic microsurgery in hcrniated cervical discs: Andrea Fontanella
Figure 9 A: C I v iew cr f a pat ient wi th a d isc herniat ion at Cs-C6 level . B: Post ,opcrat ive CT scan demonstrates a conrpleteremoval of the herniation
F igu re^10^A :MR l v i ewo fapa t i en tw i t h two la rgeek t ruded f ragmen tso fd i sche rn i a t i ona t t heCo C5 l eve l and theC5-c6level . B: Post-operat ive MRr shows a whole removal of the disc herniat ions
A
I
I .:i'::,
Neurological Research, 1999, Volume 21, January )7
Endoscopic nticrosurgery in herniated cervical discs: Andrea Fontanella
advantageous and safe methodla'1s. The goal of ttr is
surgical"technique was to achieve direct and effective
ana"tomica! cleiompression of the spinal cord and/or
nerve root and/or v'ertebral artery, without fusion of the
adiacent vertebral bodies and without post-operative
imkobi l isat ion by maintenance of in tegra l sp inal
s tabi l i tv . Wi th th is 'endoscopic technique i t is possib le
to mainta in a normal mobi l i ty of in terver tebra l space,
avoidine the inevitable stresses applied to adiacent
interspaies following fusion and the consequent sec-
ondary morbid i ty . Fol lowing th is keyhole surgery,
complications are very improbable and there are no
iutroiuni. changes seiondary to the surgery' In all the
oatielnts we dii not remove most of the disc in the
intervertebral space, which maintains spinal stabil ity'
This technique'allow us to operate on several levels of
the cerv ica l sp ine at the same t ime. The operat ion t ime
of th is endosiopic techniquc is s igni f icant ly shor ler than
in the open t radi t ional techniq-ues- Average t ime in
endoscopic microsurgery to. perform a. standard herni-
ec[omy was 25 min. iomprehensive training in this kind
of surg'ery is necessary before performing operations' We
think ihat cont inued development and improvement of
instruments, longer folloiv-up periods and a greater
number of pat ients t reated, wi l l fur ther conf i rm th is
enr loscopic microsurgical techniquera.
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2 Cloward i . The anter ior approach for removal of ruptured cerv ical
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fusion. / Bone Joint Surg 196O;42A: 565
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inteöodv fusion. ,f Bone loint Surg 1958;404: 607
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