MINIREVIEW SERIES FOR THE 50TH
VOLUME
Development of new surgical treatments in spinal surgery:expansive open-door laminoplasty andpercutaneous nucleotomy
Kazuhiro Chiba and Yoshiaki Toyama
Department of Orthopaedic Surgery, School of Medicine, Keio University, Tokyo, Japan(Received for publication on May 15, 2001)

Abstract. The outstanding achievements of two renowned spine surgeons, who are alumni of the
Department of Orthopaedic Surgery, Keio University, are described. Anterior decompression followed
by fusion and laminectomy had been the standard techniques for cervical myelopathy due to disc herniation, spondylosis and ossi®cation of the posterior longitudinal ligament. However, both techniques
were not without certain comorbidities. Dr. Kiyoshi Hirabayashi devised an epoch-making expansive
open-door laminoplasty, in which both suf®cient posterior decompression and preservation of cervicalstability are achieved simultaneously with reduced risk of such complications. Dr. Sadahisa Hijikata is
the pioneer of a totally new concept treatment, percutaneous nucleotomy, for lumbar disc herniation,
one of the most prevailing diseases that cause low back pain and sciatica. He devised this technique to
avoid prolonged conservative treatment with associated suffering of the patients and to minimize thechance of morbidity that is occasionally associated with an open surgery. This technique, together withchemonucleolysis, has led to the establishment of intradical or intermediate treatments which lie between conservative and surgical treatments. Both techniques have not only brought the relief of pain
and suffering in numerous patients, but have also opened the door to the development of many newmodi®ed procedures and technologies. Most importantly, these two techniques still remain as the mostviable choice among various similar modi®cations. The rationale, indictions, technique as well as thepresent status and future perspective for these two innovative yet fundamental techniques are introduced and discussed. (Keio J Med 50 (3): 142±151, September 2001)
Key words: spinal surgery, expansive laminoplasty, cervical myelopathy, percutaneous nucleotomy,
lumbar disc herniation

Introduction
It is our great honor as well as privilege to be able
to make a worthwhile contribution to the commemorative 50th volume of the Keio Journal of Medicine,
one of the few English journals published by a single
school. Through this journal, Keio Medical Society has
continuously conveyed its brilliant scienti®c achievements to the medical communities outside Japan. In
the present paper, we would like to introduce the accomplishments of two renowned spine surgeons who
are alumni of Keio. They both developed new surgical techniques for the most common spinal disorders

and furthermore has signi®cantly contributed to theestablishment of totally new concepts that formed thebasis for the development of many other treatment
options.
Dr. Kiyoshi Hirabayashi, former Dean of the Keio
Junior College of Nursing and former Professor of the
Department of Orthopaedic Surgery, Keio University,
developed a novel technique ``expansive open-doorlaminoplasty (ELAP)'' which has brought remarkable
improvement in the surgical results of cervical myelopathy caused by a variety of cervical disorders including
disc herniation, spondylosis and ossi®cation of the posterior longitudinal ligaments (OPLL).

Reprint requests to: Dr. Kazuhiro Chiba, Department of Orthopaedic Surgery, School of Medicine, Keio University, 35 Shinanomachi,
Shinjuku-ku, Tokyo 160-8582, Japan, e-mail: kchiba@sc.itc.keio.ac.jp142Keio J Med 2001; 50 (3): 142±151

Dr. Sadahisa Hijikata, Vice President of the Tokyo
Den-ryoku Hospital and former Director of the Department of Orthopaedic Surgery of the same hospitalinvented an entirely new concept treatment, ``percutaneous nucleotomy (PN)'', for lumbar disc herniation,
one of the most prevailing diseases that causes low backpain and sciatica.
Expansive Open-Door Laminoplasty
Until the late sixties, conventional laminectomy that
totally removes laminae piece by piece with attachedligamentous structures had been the standard surgical
technique for cervical myelopathy caused by multi-levelspondylosis and OPLL. However, both patients andsurgeons had suffered from unpredictable surgical results due to the inherent traumatic nature of the technique leading to various complications.1,2
In 1968, Kirita devised a sophisticated technique inwhich the laminae were thinned and divided at the
midline using a high speed drill followed by their enbloc resection to achieve total decompression of thecompressed spinal cord.3 This technique added muchsafety to conventional laminectomy and signi®cantly
reduced the rate of neurological complications, however, vulnerability of the unprotected spinal cord andthe recurrence of myelopathy due to the developmentof postoperative kyphosis or due to the formation oflaminectomy membrane remained as unsolved problems.4
To address such problems, Hattori and his coworkers devised an expansive Z-plasty of the laminae
in 1973, in which the laminae were preserved and reconstructed (Fig. 1).5,6 However, this technique did not

Fig. 1 Schematic drawing of a variety of laminoplasties, including A)
open door, B) midsagittal splitting and C) Z-plasty. (taken fromreference 7, with permission obtained from Lippincott Williams &Wilkins, Baltimore, MD, USA)143

gain widespread acceptance because of its complicatedtechnical aspects.
Hirabayashi modi®ed Kirita's method and decompressed the spinal cord by making bilateral bony guttersby a high speed drill at the junction of laminae andfacet joints followed by en bloc resection of the laminae.7 The idea of open-door laminoplasty evolved
when he noticed the presence of dural pulsation, a signof decompression of the dural tube, at the lift of one
side of the laminae just before their complete removal.8
Instead of laminectomy, he performed the ®rst case ofthis procedure in 1977 and named the technique ELAP.
In 1981, he presented his ®rst series of patients treatedby ELAP with encouraging results in the English literature for the ®rst time.9 Since then, more than 500
patients underwent this procedure in our University Hospital and af®liated hospitals with satisfactory
results.
Rationale
Anterior decompression and fusion used to be thegold standard technique for the treatment for cervicalmyelopathy because it was considered logical to remove
anterior pathological structures such as protruded discs,
osteophytes and ossi®ed ligaments, from an anterior
approach. However, anterior fusions were not withoutcomplications, especially when a lesion involves multiple levels.10 Long-term results of anterior fusions revealed that the recurrence of myelopathy was not uncommon, especially in patients with spinal stenosis.11
Unlike anterior decompression, anterior pathological structures cannot be directly removed by ELAP.
However, it has a total decompression effect induced by
the dorsal shift of the spinal cord, in addition to the
local decompression effect by the displacement of thelaminae, provided the patient's cervical alignment ismaintained in lordosis (Fig. 2).12
The posterior structures including the lamina, supraand interspinous ligaments are preserved to reconstruct
the spinal canal and the cervical muscles are reattachedto maintain cervical alignment, thereby restoring cervical stability.13 Herkowitz concluded from his biomechanical study that the stability of the cervical spine
after ELAP was not signi®cantly different from that of
the intact spine14 and several other studies have proventhat the decompression effect of ELAP is not different
from that of laminectomy and anterior decompression
followed by fusion.15±17 The incidence of instability anddegenerative changes in the adjacent levels, which maylead to a recurrent myelopathy, was signi®cantly lower
after ELAP than after anterior decompression andfusion.7 Kyphotic deformity or instability after ELAP
that required salvage anterior correction and fusion has
never been experienced in our clinic.7,18

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Chiba K and Toyama Y: Development of novel techniques in spinal surgery

Fig. 2 Difference in the decompression mechanism between anterior
decompression followed by fusion and expansive laminoplasty. A)
The spinal cord is compressed by an anterior pathologic structure,in this case, by an ossi®ed ligament. B) In anterior decompression,
the ossi®ed mass is directly removed. C) In posterior decompression,
the spinal cord shifts posteriorly and is decompressed even though theossi®ed mass remains.

Indication
Hirabayashi considers ELAP as the treatment ofchoice for almost all patients with spinal canal stenosis
whose anteroposterior diameter of the spinal canalis less than 13 mm even if they have single level disease
including disc herniation, spondylosis or segmental
OPLL.7,19 For those without spinal canal stenosis, if thepatient has a multilevel lesion, which extends beyond
two segmental levels, ELAP is preferred over anterior
fusion. Indication of anterior cervical fusion for cervicalmyelopathy has, therefore, been limited to patients witha single level lesion who have no spinal canal stenosis.11
When a patient has severe established kyphosis associated with spinal stenosis, a two-staged surgery, which
consists of ®rst-stage ELAP followed by second-stage
corrective anterior fusion, is planned. However, thesecondary anterior fusion becomes unnecessary in mostcases, because satisfactory improvement of myelopathy
could be obtained after the ®rst-stage ELAP.
Procedures and postoperative care
The patient is placed in a prone position on a surgical table with the head securely ®xed with a May®eld®xator ®rmly attached to the surgical table, and thetable is tilted cranially upward at an angle of approximately 30 degrees. Tips of the spinous processes are
exposed through a midline incision, then the bilateralparacervical muscles are stripped off from the laminae
usually between C3 and C7 by cautery or a periosteal
elevator. Once the paracervical muscles are detachedfrom the laminae, the open side gutter is made at thejunctions of the laminae and facet joints by a high speed

drill with a cutting bur. The ventral cortex is either
resected with a thin bladed Kerrison rongeur or perforated with a diamond bur. The ligamentum ¯avum atthe upper and lower ends of the laminar door, usuallyat C2/3 and C7/T1 are resected with a thin bladed Kerrison rongeur. Then the bony gutter in the hinge side ismade with the cutting bur slightly more lateral than the
one in the open side. The stability of the hinge ischecked frequently by applying a gentle bending force
to the spinous processes to prevent hinge breakage byoverdrilling. When all spinous processes and laminae
become slightly mobile yet retaining spring-like resistance, the laminar door is ready to be opened. Pieces ofsuture are placed through the facet joint capsule andsurrounding soft tissues at each level in the hinge side
and are passed through interspinous ligaments aroundthe base of the corresponding spinous process. Justprior to opening the laminar door, the patient's neckposition is converted from a ¯exed to a neutral position.
The tip of the blade of a large Kerrison rongeur isplaced under the excised margin of one lamina and its
edge is lifted slightly. The spinous process is held in the
expanded position by ®ngers of an assistant. Then thenext lamina is lifted in the same manner until all laminae are opened to the same extent. Repeat this procedure slowly and open the laminar door gradually. Release adhesions between the laminae and the dura withthe spatula every now and then. Do not try to open one
lamina extensively at one time or the hinge will break.
Usually, dural pulsation can be observed in the middleof the opening procedure even before complete expansion. These maneuvers should be continued until thelaminae of the open side become almost horizontal. To
maintain the expanded position and to prevent thereclosure, threads previously placed at the base of the
spinous processes are securely tied. A drainage tube isplaced in the epidural space. The bilateral neck muscles
are approximated to minimize the dead space and thenuchal ligament is tightly closed with nonabsorbablesutures. (Fig. 3)7,8,13,20
Postoperatively, the patient is ambulated at the 3rd
postoperative day with a soft collar, which is worn for
an average of a week. After its removal, the patient isencouraged to start gentle ROM exercise of the neck.
Stitches are removed at 10 days postoperatively. The
patients usually return to their work after 3 to 4 weeks.
Rigorous activities including sports are permitted after
3 months postoperatively.
Re®nement in surgical techniques
Since the advent of ELAP, Hirabayashi kept revising
the technique.7,13,21 These revisions include retention
sutures placed around the base of the spinous processes
to prevent laminar reclosure that had led to recurrent

Keio J Med 2001; 50 (3): 142±151

145

operatively but also enables him or her to tie the stay
sutures and reconstruct the muscular layers in the neutral position.
Clinical results

Fig. 3

Radiograph and CT after expansive open-door laminoplasty.

myelopathy requiring salvage laminectomy in one earlycase.22
Also in some early cases, breakage of the hinge wasexperienced while excising the ventral cortex of theopen side with a Kerrison rongeur, because Hirabayashi initially made the gutters in both sides with a cutting
bur followed by the resection of the ventral cortex in
the open side. He therefore changed the sequence ofthe procedures, and made the hinge side gutter after
completion of all other procedures, including the resection of the ventral cortex in the open side and ¯avectomy at the cephalad and caudal ends of the laminardoor.13,21
To maintain and con®rm cervical lordosis, which isimportant for the decompression mechanism of ELAP,
Hirabayashi also added a number of improvements. He
excluded the expansion of the C2 lamina wheneverpossible to preserved its spinous process where thesemispinalis muscles attach.7,13,21 He also tried to preserve the supraspinous and interspinous ligaments asmuch as possible. In some cases, these ligaments at thecaudal end of the laminar door become tight and exert
strong resistance, making suf®cient expansion dif®cult.
In such cases, the spinous process just below the caudal
end of the expansion, usually that of T1, is exposed, andan osteotomy is carried out with a high-speed drill at its
base and the process is bent toward the hinge side torelieve the tension of these ligaments.7,21 The conversion of the patient's neck position from a ¯exed to aneutral position just before the laminar opening is another tip added by Hirabayashi. This not only allows
the surgeon to con®rm the lordotic alignment intra-

The long-term surgical results of 80 patients who
underwent ELAP for myelopathy due to cervical spondylosis and OPLL with minimum 10 years follow-up
were satisfactory.23,24 Their recovery rates calculatedusing pre and postoperative Japanese Orthopaedic Association (JOA) scores were 53.1% for spondylosis and47.9% for OPLL after an average follow-up of 14 years.
Overall, 60% of the patients were rated as either excellent or good for cervical spondylotic myelopathy(CSM) and 55.0% for OPLL patients.
The preoperative duration of myelopathy, the age ofthe patient at the time of surgery, predisposition to
trauma and the severity of spinal canal stenosis were
the factors that signi®cantly affected the clinical results.
Patients over 65 years of age, those having myelopathy
lasting over 2 years, those with an onset of the symptoms after trauma and those with severe spinal canalstenosis and kyphosis had signi®cantly poor surgicalresults.18,21
Late gradual neurological deterioration, mainly inlower extremity motor function, developed in seven
CSM and 16 OPLL patients whose average age atthe ®nal follow-up were 70 and 77 years respectively.
Probable causes of the deterioration included comorbidities such as cerebrovascular, heart and degenerative
lumbar diseases as well as progression of OPLL. However, such motor dysfunction may partly be due to normal aging processes.23,24
Suf®cient decompression was veri®ed in postoperative MR images in both CSM and OPLL patients
although asymptomatic, degenerative changes at thecranial and caudal ends of laminar expansion were
found in some patients and need further observation.
The percentage of patients with lordosis decreased
from 70% preoperatively to 50% at the ®nal follow-up
and patients with non-lordotic alignment increased accordingly. Severe kyphotic deformity, however, did not
develop in any patient. Even though there were no
signi®cant differences in the ®nal recovery rates among
patients with different alignments in both CSM andOPLL groups, those with kyphosis in the OPLL patients
had much lower average recovery rate (9%) comparedto those with lordosis (52%) and straight (38%).
Postoperative ROM on extension radiographs between C2 and C7 decreased signi®cantly, while thatbetween Occiput and C2 increased slightly making an
overall decrease of approximately 35%.
Motor weakness in C5 or C6 segments was the mostnotorious complication, whose incidence was reported

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Chiba K and Toyama Y: Development of novel techniques in spinal surgery

to be between 5 and 10%, although most of themrecovered completely within 2 years postoperatively.25
Approximately one third of patients complained ofaxial symptoms postoperatively such as shoulder andneck stiffness and pain. However, less than 10% weretaking daily anti-in¯ammatory drugs due to such symptoms. Also, approximately one third of patients hadcomplaints due to restricted ROM, mainly dif®culty inturning back their heads and looking down at their toetips, but most of them had minor disturbances in their
ADL.23,24
A decrease in ROM due to fusion at the hinge side
may stabilize the spine maintaining favorable long-term
results, while at the same time may become a sourceof axial complaints. However, such drawbacks were, insome degree, compensated by upper cervical spine
motion resulting in less ADL disturbances.23,24
Present status and future perspective of ELAP
Inspired by Hirabayashi's concept of ELAP and its
favorable surgical results, various modi®cations havebeen developed in expansive laminoplasty, mostly inJapan, such as midsagittal splitting laminoplasties.26
The open-door technique itself also has undergone a variety of modi®cations and additions including the use ofbone grafts, spacers and plates trying to address problems of reclosure or postoperative malalignment.27,28
However, this fundamental yet innovative techniqueforms the basis for all other procedures and still remains to be the most viable options for the surgicaltreatment of compressive myelopathy. When comparedwith other modi®ed laminoplasties, ELAP is the simplest and safest with less surgical impacts, i.e., shorter
operating time, less bleeding and lower incidence ofcomplications.7,10,17,29
With respect to the postoperative cervical stability,
we feel that any spacers, grafts or instruments are unnecessary if we carefully follow the procedures mentioned above. ELAP seems to be a rational indication
for the majority of cases of typical cervical stenotic
myelopathy, whereas other expansive laminoplasties
that use bone grafting, spacers, or plates may be indicated for those with a high degree of instability such ascerebral palsy.7
There still remain several problems to be solved in
ELAP. The etiology of segmental motor paralysis is
yet to be elucidated and no one has established effective preventive measures. Even though preservation ofpreoperative alignment has been possible to a certain
degree, nobody has succeeded in correcting the preoperatively established kyphosis into physiological lordosis to date. So far, there is no effective way to regenerate the spinal cord function, once it is damaged
irreversibly. We therefore recommend to perform

ELAP as early as possible and ELAP is an ideal procedure which is considered to be reliable because it has
the same decompression effect as laminectomy and isconsidered much safer and easier than anterior fusion
for the severely deteriorated spinal cord. Such safety
and reliability are the keys to make early operation
possible, thereby achieving better clinical results.7
Percutaneous Nucleotomy
Lumbar disc herniation due to disc degeneration is
one of the most common lesions affecting the back in allindustrialized countries. The treatment for lumbar discherniation had long been divided into two widely divergent modalities, conservative and surgical. At thosetimes, if the patient failed conservative treatments, open
surgery was the only remaining option available. However, results of surgeries were not always satisfying.
Moreover, some patients were not available for surgery
because of their poor general conditions and somerefused surgery even though they were good candidates.
In an attempt to avoid prolonged suffering from unsuccessful conservative treatment and to minimize thechance of morbidity often associated with open surgery,many surgeons sought alternative ways of decompressing a pathological disc. In 1964, Smith introduced chemonucleolysis, a dissolution of the nucleus pulposus
using a proteolytic enzyme, chymopapain,30 which subsequently gained wide popularity with acceptable results. However, the use of chemonucleolysis has declined dramatically in recent years because of a varietyof complications, particularly those involving anaphylaxis and neurological loss which are rare but can becatastrophic.
Hijikata, who had actively participated in basic andclinical studies concerning the intervertebral disc degeneration, had much interest in novel treatment possibilities such as chemonucleolysis. He also was attracted by a paper published by Hult which suggested
the possibility of partial discectomy and decompressionof the intradiscal pressure through an anterolateral annular window that could bring relief from sciatica.31 As
a clinician, Hijikata had extensive experience in lumbar
discography with hundreds of cases and through thisexperience, he noticed that in some patients, their
symptoms were dramatically relieved on the day following discography.32 Through these studies and experiences, the idea evolved that decompression of
intradiscal pressure could be achieved percutaneously
thereby relieving the symptoms of patients with a discherniation without invasive surgery. After a great dealof anatomic research and re®nement of appropriate
instruments, the ®rst percutaneous procedure was performed on March 6, 1975, in a 16-year-old boy with anexcellent result.33

Keio J Med 2001; 50 (3): 142±151147

classi®ed as one of the intradiscal or intermediate
treatments that are located on the spectrum of treatment for lumbar disc herniation somewhere between
conservative and surgical treatments.
Indications

Fig. 4 Mechanism of pain relief in percutaneous nucleotomy. (takenfrom reference 32 with permission obtained from Lippincott Williams& Wilkins, Baltimore, MD, USA)

More than 25 years have passed since the ®rst caseof this new concept treatment, which he initiallytermed ``percutaneous nuclectomy''. This technique,now known as PN, has gained widespread acceptance asanother alternative minimally invasive option for lumbar disc herniation.32,34
Rationale
Posterolateral disc puncture is followed by the sequential insertion of the guide pipes and the cannula.
The annulus is perforated by a special cutter and avariety of punch forceps are inserted through the cannula, thus, fenestration of the annulus, partial removalof nuclear substance could be achieved percutaneously.32 The restrictions imposed by the surgical approach and the instrumentation make it impossible toextract the herniated mass itself. However, intradiscalpressure is reduced considerably and relief from irritation of the nerve root or the pain receptors around thedisc could be obtained (Fig. 4).32
In this procedure, the disc material mainly composedof the nucleus pulposus is extracted, which ultimately
leads to decompression of intradiscal pressure. However, fenestration of the annulus may also play a signi®cant role in the decompression mechanism. Many
investigators therefore used a term percutaneous discectomy rather than nucleotomy, and Hijikata thinksthat both terms are interchangeable.32
PN can be done in a radiology department underlocal anesthesia, just as the conventional discography
and together with chemonucleolysis, this procedure is

PN is indicated in patients with clinical symptoms
and signs typical of lumbar disc herniation such as painor numbness extending into one leg with or without low
back pain, restricted straight leg raising, neurologicalimpairment including re¯ex abnormality, sensory disturbance and motor weakness, all of which were con®ned to an appropriate segmental distribution. The
presence of evidence of a herniated disc in radiographic
examinations such as myelography, discography, CT
and MRI are imperative. Contained discs including
protrusions and subligamentous extrusions are the bestindications. All patients should undergo at least six
weeks of conservative treatments, which include bracing, physical therapy and epidural steroid injections
before being considered candidates for PN. Patients
whose complaints are reproducible at discography areespecially good candidates for this procedure.
Contraindications are sequestrated herniation, associated spinal stenosis, compensation and litigation
cases, and patients with psychosocial problems. To improve clinical results of PN, it is essential to clearly de®ne clinical and radiographical criteria for patient
selection. Many investigators have recommended criteria based on their own experience.35±37 For the patient
who has no improvement postoperatively, Hijikata recommends conventional disc surgery within two or three
weeks in order to minimize the patient's disability.
Instruments and procedures
Surgical instruments for PN have been designed toachieve rapid extraction of the disc material safely andaccurately. A standard set of instruments for the procedure consists of a discography needle with a pilot
sheath, three guide pipes with a different diameter andlength, a cannula, an annulus cutter, and a variety ofpunch forceps. (Fig. 5)32,33
The procedure can be conducted in either an operating room or a ¯uoroscopy room in the radiology department. A ®ne ¯uoroscopic image control is essential.
The patient is placed in a lateral decubitus position withsymptomatic side uppermost should there be the laterality in leg symptoms. Pillows or towel rolls are placed
underneath the patient's waist to insure a convexity ofthe patient's lumbar column at the site of puncture.
After thorough sterilization and draping, an abundant amount of 0.5% Xylocaine is injected into the skin
all the way down to the disc. The target disc is punc-

148

Chiba K and Toyama Y: Development of novel techniques in spinal surgery

Fig. 5 A standard set of instruments for percutaneous nucleotomy.
(taken from reference 32 with permission obtained from Lippincott
Williams & Wilkins, Baltimore, MD, USA)

tured with a 19-gauge discography needle with a special
pilot sheath through a posterolateral approach as in theconventional discography. In cases of the L5-S1 disclevel, the entry point in the skin is near that of the L4±
L5 disc with a needle inclined more caudally to avoid
the iliac crest. Radiating pain is a sign of the irritationof the cranial nerve root and a small adjustment of theneedle direction is necessary. Once the needle perforates the disc, the tip of the needle must be at orslightly posterior to the true center of the disc. A±P andlateral radiographs are taken to con®rm the correct
position of the needle tip.32,34
First, a mixture of radiopaque dye and methylene
blue dye is injected into the disc. Reproduction of pain
and radiographical ®ndings are checked and are compared with those of the preoperative discography. Afteradvancing the outer pilot sheath approximately 5 mm
into the annulus, the discography needle is withdrawn,
leaving the pilot sheath alone, which acts as a guidefor the later procedures. A 5 mm skin incision is madeat the entry point. Three progressively larger dilating
pipes are placed over the initial guide pipe and one
over the other. Finally, the cannula, the outside diameter of which is 4 mm, is advanced over the guide pipes
to the disc margin. During these procedures, thepatient's pain response should be monitored carefully
to avoid nerve and vascular injuries. While the cannula
is pushed ®rmly against the disc, the pilot sheath andthe pipes are removed and the annulus cutter, which issaw-toothed, is inserted into the cannula and the annulus is perforated. Fluoroscopic control is used in order
to avoid penetration of the endplates. The punch forceps are then inserted and disc material is removed.
The patient complains of no pain as long as the forceps
stay within the nucleus. If the extracted materials are
not stained with the blue dye or the patient complainsFig. 6 Extraction of disc materials with a punch forceps through thecannula.

of pain, the forceps may be in the annulus and thedanger of injuring the peripheral tissues becomes high.
The direction of the cannula is changed carefully toremove as much nucleus as possible. At least 1 g, preferably 3 g of disc material should be extracted. Insert
the annulus cutter into the disc once in a while so that asuction could be applied with a 30±50 mm syringe thatis connected to the lurlock connector at the caudal endof the cutter. Extraction is ®nished when no further discremoval can be achieved. The cannula is then withdrawn quickly and surgical adhesive tape is used toclose the skin. The entire procedure usually takes
approximately 40 to 60 minutes. (Fig. 6)
The patient can be ambulated soon after the procedure. Hijikata recommends a relative rest periodof three days after the procedure so as to monitor thepatient's general and neurological status frequently
within this period.32
Clinical results
Hijikata reported his experience in 136 patients withan average success rate of 72% in 1989. Among 28%
unsuccessful cases, 19% were treated by subsequentconventional open surgery, mainly standard discectomy.32 Clinical evaluations in his studies were done
according to the criteria based on the Modi®ed Japanese Orthopedic Association's score for low-back pain.
By these criteria, `excellent' indicates that the patient isalmost free of complaints and has no restrictions in his
or her daily life. `Good' indicates that the patient has
some or occasional complaints but is improved considerably and almost free of symptoms in daily activities.
`Fair' indicates that the patient's complaints andKeio J Med 2001; 50 (3): 142±151

restrictions still remain. `Poor' indicates no improvement or worsening of symptoms with considerable restrictions in daily activities. The success rates reported
by others are similar and in the range between 53% and
94% with an average of 75%.
L4±L5 discs were most commonly and easily treatedwith favorable results. In the cases of L5-S1 discs, eventhough the punctures with a guide wire were possible inmost cases, it was more dif®cult to place the needle tip
in an ideal position due to anatomical reasons and discextraction tended to be insuf®cient, therefore making
the procedures less effective. Patients with contained
herniations (i.e., bulging, protrusion, and subligamentous extrusion) had better results than those withuncontained transligamentous extrusions. Patients who
had less disc material removed, and older patientstended to have inferior results.
On postoperative radiographs, disc narrowing was
not found in most cases since only 1±3 g of disc material
was extracted and only 4% of the discs showed signi®cant narrowing of the disc space. Meanwhile, postoperative discograms in two cases showed that the opening
made into the annulus was still patent even after ninemonths. In one case with an unsatisfactory result, postoperative discography revealed that too much of theanterior part of the disc had been removed. This patientunderwent another PN, in which additional material
was successfully removed from the posterior portion of
the disc, ultimately providing a favorable result. Postoperative discograms often revealed the progression ofdisc degeneration after the procedure. MRI is effective
in demonstrating the diminished size of the herniatedmass and the site of disc removal as well as progressionof disc degeneration. In his 25 years of experience,
Hijikata had two infections and one minor vascular
injury only. However, there have been reports on major
vascular injury that required the open repair. Hijikata
also experienced aggravation of leg pain immediately
after the procedure in two patients. Emergency MRI
revealed an increase in the size of the herniated massin both cases. He assumed that the insertion and themanipulation of the punch forceps might have caused
the increase in the intradiscal pressure and pushed out
the disc fragment further into the spinal canal. In suchcase, he recommends emergency MRI followed by asurgical intervention to immediately salvage the patients'
suffering.34
Present status and future perspective of PN
After 1983, many papers on PN have been publishedwith satisfactory results, which had proven that Hijikata's initial idea of percutaneous disc decompressionthat could lead to the relief of sciatica and back pain is
feasible.36,38±45149Over the years, PN has undergone a wide variety oftechnical modi®cations. Suezawa, also an alumnus of
Keio, took the instruments and technique from Japan
to Zurich, Switzerland, and together with Schreiber,
developed and improved a technique and instrumentswith the combined use of intradiscal optical visualization using discoscopy.43,45 Kambin and colleagues
revised the technique and re®ned the instruments to ®t
the size of Western patients and published excellent
clinical results of their PN.38 Monteiro developed his
own instruments and has reported over 400 cases withvarious kinds of back problems.40 Onik, et al. havedeveloped a new aspiration probe and a new technique of automatic percutaneous discectomy. One of
the major advantages of Onik's method is that it uses
smaller and thinner cannulas, the diameter of which isonly 2.8 mm.41,46
The development of this initial PN procedure has
opened the door to many other possible uses of thetechnique. Percutaneous cervical discectomy has been
performed throughout the world, mostly using a nucleotome.47 Techniques to achieve spondylodesis or arthorodesis through percutaneous approaches have beendeveloped.48 Introduction of laser vaporization of thenucleus pulposus was ®rst reported by a Japanese spine
surgeon and now has become one of the most preferredalternative treatments for disc herniation.49 Intradiscal
thermal modulation of the disc for internal derangement of the disc is now widely used in the U.S. as apopular alternative treatment for low back pain.50
One of the most signi®cant contributions of Hijikata
is the development of the sophisticated technique toaccess the disc safely and effectively using a guide wireand soft tissue dilating devices. The concept of thistechnique is now commonly used in various minimallyinvasive procedures including laparoscopic surgeries
and microendoscopic discectomy.51
The prevalence of these minimally invasive treatment alternatives has led to the establishment of a newform of treatment called ``intermediate therapy'', representing these alternative therapies that are locatedbetween conservative and surgical treatments in the
spectrum of treatment for lumbar disc herniation.
However, because of their inherent indirect nature,clinical outcomes of these procedures are in the 70%
range.32,37±39,41,43,44
The surgeons who use these alternative treatments
should, therefore, always be reminded that PN is not apart of conservative treatments that can be prescribedeasily nor an absolute replacement for conventional
surgeries. It is a treatment in its own right and allconservative, intermediate and surgical treatments havetheir own advantages and disadvantages. However,there is concern about the risks that may be encounteredby the rapid use of this procedure by less-experienced

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Chiba K and Toyama Y: Development of novel techniques in spinal surgery

persons without the proper indications for its use.34
When indicating PN for patients with disc problems,
there are two fundamental ideas that could be chosen.
One is to select patients carefully through strict criteria
in order to obtain a higher success rate.36,37 The otheris to apply PN aggressively, before any major surgery iscontemplated, if the patient falls into any category thatis amenable to PN.34 Hijikata believes that both arepractical as long as the selection is made on the basis ofpatients' bene®ts and the best choice may lie somewhere between the two ideas. However, he has kept
warning that the abuse of the technique based on thecommercialism on the surgeons' side or excessive enthusiasm for new treatments on the patients' sideshould strictly be prohibited. Even though PN is muchless invasive to surrounding soft tissues, the damage tothe disc itself is comparable or, in some cases, greaterthan open surgery.34 Many patients with disc herniations or back pain without sciatica caused by disc degeneration, can be satisfactorily treated by PN. Bothsurgeons and patients would bene®t from having PN asa choice among a variety of treatment modalities forlumbar disc herniation.
It is our great pleasure to know that our alumni haveestablished innovative treatment modalities that havechanged the stream of managements for the most common spinal disorders and have greatly contributed to
the relief from pains and disabilities of many patients.
Both of them were devoted to look for a better patientcare, had the ability to get inspirations from their dailyclinical experiences that most of us would overlook andhad the courage and strong will to put their ideas into
reality. It is our obligation to keep revising the originaltechniques to improve the outcome yet to preserve thefundamental rationale that reside in these original ideas
and concepts and pass them on to the next generation.
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