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531

Review 42

..

.,.

.

Automated

Percutaneous

Gary Onik1 and Clyde

A. Helms2

Lumbar

The use of automated percutaneous lumbar diskectomy for the treatment of herniated lumbar disks is increasing. More than 3000 physicians have been trained to perform the procedure, and over 40,000 cases have been completed worldwide. This review de-

scribes the development kectomy,

the selection

is performed,

of automated of appropriate

and its efficacy

percutaneous patients,

lumbar dis-

how the technique

relative to other methods

of treat-

ment.

Automated

percutaneous

lumbar

diskectomy

(APLD)

is a

relatively new advance in the treatment of herniated lumbar disks. The technique involves the placement, under fluoroscopic guidance and with local anesthesia, of a small auto-

mated suction probe into the affected disk. A small portion of the central nuclear material is then aspirated. The concept of the procedure is to decrease the intradiskal pressure and to transmit this decreased anulus to the herniation,

pressure through the rent thereby relieving the pressure

in the on the

Diskectomy

accepted procedure for the treatment disks, and the National Blue Cross/Blue Assessment Committee has determined

efficacious moving

in treating it from

experience

contained

investigational

accumulating,

Development Diskectomy

of Automated

Percutaneous

and the perception lumbar

and significant Over

3000

procedures

that the traditional disks

was

associated

throughout

surgical with

medicine

treatment variable

for

results

morbidity. physicians

have

been

trained

in small

group

workshops to perform the APLD procedure, and more than 40,000 cases have been completed on a worldwide basis (Allen R, personal communication). In their recent policy statement on herniated disks [1 ], the American Academy of Orthopedic Surgeons has listed percutaneous diskectomy as an

complications

associated

[2], in a prospective 13%, including

with

© American

Roentgen

disks,

me-

extensive

at this point

to

Lumbar

procedure.

neumosurgeons,

one death,

found

Stolke

et al.

performed

a complication

by

mate of

three nerve injuries, and an apRamirez and Thisted [3] mediskectomies performed in a that one in 64 patients had a had a major neumologic com500 had a cardiovascular died from the procedure. It is

with open diskectomy

that has prompted the search for less morbid procedures. Chymopapain injection was the first of the less invasive treatments for herniated lumbar disks. Unfortunately, treat-

Received May 14, 1 990; accepted after revision September 1 2, 1990. 1 Department of Radiology, Presbyterian-University Hospital, DeSoto and O’Hara Sts., Pittsburgh, Department of Radiology, University of California, San Francisco, San Francisco, CA 94143.

March 1991 0361-803X/91/1563-0531

this

study of 481 procedures

the concern over these risks associated

2

AJR 156:531-538,

this

The recent literature dealing with the morbidity of simple open diskectomy has emphasized the potential for possible

proximate diskitis mate of 1 %. viewed 28,000 simple open community setting and found major complication, one in 335 plication, one in approximately complication, and one in 1700

invasive

lumbar

With

it is appropriate

trend

less

herniated

review the knowledge available about this procedure. In this review we discuss the indications and patient selection for the procedure, as well as provide a description of the technique and review the available results.

experienced

toward

of herniated lumbar Shield Technology APLD to be safe and

status.

affected nerve root and resolving the patient’s symptoms. Development of this technique was instigated by the general

herniated

Article

Ray Society

PA 15213. Address reprint requests to G. Onik.

532

ONIK

AND

ment

with chymopapain had associated problems: anaphysevere back spasms in a significant number of patients, disk space narrowing, and associated transverse myelitis with laxis,

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paraplegia.

It was this last complication,

with its possible

legal

ramifications, that greatly curtailed the use of chymopapain in the United States. Percutaneous diskectomy, a mechanical decompression of the disk, is an attempt to effect the same results as chymopapain without the associated complications. Percutaneous diskectomy was introduced by Hijikata et al. [4] in 1975 as a form of treatment for herniated lumbar disks. Since that original article, a number of other investigators have used manual disk removal techniques similar to that of Hijikata et al. and have reported success mates of 72-87% [5-i 1]. All these hand methods of percutaneous diskectomy have the common elements of a relatively large cannula (6 mm or larger) being used to gain access to the disk space with the disk being removed by some form of grasping forceps. Although these recently published articles have shown this technique to be efficacious, the method has not been without significant morbidity. At least two instances of major vascular injuries have been reported with this type of procedure [5-9]. In addition, since the disk is entered multiple times, the

N UC PU

LEUS

IPOSU

S

HELMS

ii

B

___luLl.. := .ASPIRATED

March

1991

diskitis mates reported with this method have been consistent with the 1% diskitis rate reported for open diskectomy [12, 13]. APLD,

first

reported

by Onik

et al. [1 4], takes

advantage

of a 2-mm reciprocating suction cutter that can cut separate pieces of disk material up to 200 times per minute. The Nucleotome aspiration probe (Surgical Dynamics, Inc., San Leandro, CA) works by aspirating nucleus pulposus into its recessed side port. A flared inner cutter is pneumatically driven across the port, cutting off disk material, which is then suspended in saline and aspirated away (Fig.1 ). Since anulus fibrosus cannot be sucked into its side port, the Nucleotome cannot cut its way out of the disk, adding to the safety of the procedure. By automating the process, it is possible to decrease the size of the instrumentation, thereby decreasing the chances for nerve injury, vessel damage, and soft-tissue trauma in a large patient population. Because the instrument is placed into the disk and remains there without being removed, the chances of contamination and diskitis are lowemed to approximately one fifth that of an open procedure or of percutaneous diskectomy done by hand [1 5]. Since that first report by Onik et al., a large amount of data has accumulated showing the concept of APLD to be successful. Currently, 19 studies on APLD, comprising over 3600 patients, are either published or in press [1 5-33]. Twelve of the reports show a success mate of 80% or greater, and six of the studies show a success mate of 70-80%. In all these studies, no major complications were reported; specifically, no death, permanent nerve injury, or vessel damage was reported. A diskitis rate of 0.2%, three to five times lower than that for other diskectomy methods, was reported.

Selection A

AJR:156,

of Patients

As with all back operations, good results depend on proper selection of patients (Table 1 ). As with any disk operation, the procedure is predominantly for those patients with leg pain secondary to a herniated disk and is not for patients with chronic or acute low back pain. Before considering APLD, an adequate course of at least 6 weeks of simple conservative care, including rest, analgesics, and physical therapy, should have been attempted without success. In practice, it is Unusual to operate on any patient who has not had 3 months of conservative treatment. APLD should be performed only on those patients whose disk hemniations are contained by the anulus fibrosis or pos-

....

TABLE

NCLE5

1: Criteria

Percutaneous

Used to Select

Patients

for Automated

Lumbar Diskectomy

.

Criteria Clinical

C

Sciatica

Fig. 1.-A, Drawing of Nucleotome illustrates how suction is applied to central bore, thereby aspirating disk material into side port. B, An inner cutting sleeve is pneumatically driven across side port, effectively guillotmning disk material. C, Disk material is suspended in saline, which flows between walls of

Nucleotome (Reprinted

and inner cutting sleeve, and is aspirated away. from Onik et al. (14].)

Physical Failure Radiologic

(leg pain predominates findings that of conservative

correlate therapy

Herniated nucleus pulposus gitudinal ligament Exclusion of free fragments,

over back pain) with pain (6 weeks)

contained spinal

by anulus

stenosis,

or posterior

calcified

disks

Ion-

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AJR:156,

March

AUTOMATED

1991

PERCUTANEOUS

tenor longitudinal ligament, that is, a protrusion (Fig. 2). Performing the procedure in patients with extruded or free fragments of disk would lead to a large number of failed procedures. The major burden in selecting patients for APLD falls on radiologic imaging. Preoperative CT or MR scans should be obtained to confirm the presence of a small to moderate focal bulge or hemniation that is consistent with the patient’s symptoms (Fig. 3) and to exclude a free disk fragment. Myelography alone is not adequate because it does not exclude complicating abnormalities such as lateral recess stenosis, calcified disk hemniations, or far lateral disk herniations. It is extremely important to determine the size of the disk hemniation. In one report, 90% of patients with herniated disks comprising 50% or more of the thecal sac had extruded or free fragments (Fig. 4) [34]. In addition, the shape of the hemniation can be used as an indication of whether the hemiation is extruded or contained. Contained herniations tend to have smooth obtuse margins that blend at its base with the rest of the anulus fibmosus.

Normal

E xtrus

Protrusion

10 fl

5eques

trat

ion

Fig. 2.-Diagram of stages of herniated nucleus pulposus illustrates various stages of disk herniations. Automated percutaneous lumbar diskectomy

should

be performed

only in a protrusion.

LUMBAR

DISKECTOMY

Irregular hemniations, that is, those with sharp angles to the anular margin, probably have extruded fragments (Fig.4). CT or MR demonstration of a piece of disk material above or below the disk space or filling a lateral recess is a contraindication to APLD because a migrated fragment of disk certainly would not be affected by central disk decompression (Fig. 5). When theme is any doubt as to whether the hemniation is extruded through the posterior longitudinal ligament, diskogmaphy can be performed to investigate the integrity of the anulus and posterior longitudinal ligament. Free flow of contrast material into the epidumal space indicates a complete tear of the anulus and posterior longitudinal ligament and a high likelihood that the herniation has extruded (Fig. 6). Demonstration of flow of contrast material through the anulam tear to cover the disk hemniation also indicates that a communication still exists between the center of the disk and the hemniation. This confirms the possibility that extraction of disk material or transmission of pressure differences between the disk hemniation and the center of the disk can still occur (Fig. 7). When diskogmaphy does not demonstrate a hemniation that is seen on CT or MA, percutaneous diskectomy should not be undertaken. Edwards et al. [35] showed that when herniations did not stain when contrast material was injected into the center of the disk for CT diskography, chymopapain was successful in only 1 0% of cases because the anular tear had closed, not allowing communication between the herniated nucleus pulposus and the nucleus. It stands to reason that this criterion is applicable to percutaneous diskectomy as well. Considering that APLD is a procedure for patients with contained hemniations only, what proportion of the disk herniation population might be helped by APLD? In a recent prospective surgical series [36], 20% of patients operated on with an open procedure had contained disk hemniations. Considering that over 200,000 disk operations are performed

Fig. 3.-CT scans of focal disk protrusions (arrows) that are good candidates radiologically for percutaneous diskectomy. A, Focal protrusion at L4-L5 level is consistent with leg pain. Automated percutaneous lumbar

diskectomy

533

was performed, and the patient did well for 2 years.

B, CT scan 2 years later after recurrence of right leg pain. Contained herniated nucleus at L5-Si level was successfully treated with automated percutaneous lumbar diskectomy.

pulposus

Fig. 4.-CT scan shows a large disk herniation that is not a candidate for percutaneous diskectomy owing to its large size (50% of thecal sac). Sharp angulation between margin of anulus and herniation (arrow) indicates a probable extrusion.

ONIK

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534

Fig. 5.-CT

scan through lateral recess reveals

migrated disk material (arrow), which suggests a free fragment. This patient is not a candidate for percutaneous diskectomy.

AND

HELMS

AJR:156,

March

1991

Fig. 6.-CT diskogram shows free flow of contrast material into epidural space, which indicates a noncontained disk. This patient is not

Fig. 7.-Diskogram shows staining of disk protrusion (arrow) without free flow of contrast material. This patient is a good candidate for

a candidate for percutaneous

percutaneous

each year in the United States, approximately 40,000 patients could be spared a major surgical procedure.

diskectomy.

diskectomy.

of these

Technique A detailed description of the APLD technique is beyond the scope of this review; however, a number of technical points are pertinent because they help explain why APLD has such a low morbidity rate. APLD reaches the disk via a posterolateral approach. The instruments pass just anterior to the superior articular facet, behind the nerve, in a trajectory toward the center of the disk (Fig. 8). Certain radiologic landmarks prevent injury to vital structures during placement of the instruments. A line that connects the posterior vertebral bodies, anterior to which lie the nerve, bowel, and great vessels, prevents injury to these structures (Fig. 9). When the instruments are against the anulus, they should be at this line but not anterior to it. On the anteroposterior view, an imaginary line connecting the medial border of the pedicles indicates the lateral border of the thecal sac. If the instruments are lateral to this line when they are lying against anulus fibrosus, they will not be impinging on the thecal sac (Fig. 10). The procedure must be performed with only local anesthesia used, to allow the patient to react to any nerve root impingement. If the patient experiences radicular pain during the procedure, the instruments are redirected, thus preventing a nerve root injury. Localization of the instruments to the center of the disk is first carried out with an 1 8-gauge trocam. Once this trocam is localized to the center of the disk, the larger 2.8-mm cannula and dilator are brought down over the trocar to the disk. The dilator is removed, and the anulus is incised with a tmephmne. The trephine and trocam are removed, and the Nucleotome is then placed within the disk (Fig. 1 1). The procedure is monitored by watching the disk material being aspirated, which is visualized in the aspiration line. When no more disk material is seen, the procedure is concluded and the instruments are removed. The position of the

Fig. 8.-Diagram ivc

=

inferior

vena

shows path taken during

percutaneous

diskectomy.

cava.

cannula on the anulus prevents the Nucleotome from injuring surrounding soft-tissue structures if it is inadvertently brought out of the disk. The approach to the L5-S1 disk space is essentially the same as for L4-L5 and has been described in detail elsewhere [37]. The introduction of a curved cannula, through which the straight Nucleotome, which is flexible, can be placed, allows consistent entry into the L5-Si disk in over 90% of cases [38].

Results

of APLD

Compared

with Other

Techniques

The findings of a prospective multiinstitutional study to evaluate APLD have been reported [1 5]. Satisfying the inclusion criteria for selection were patients with classic sciatica whose herniated lumbar disks on imaging studies were consistent with their symptoms. Patients were prospectively excluded from this study ifthey had had previous lumbar surgery or chymopapain injection; if they had worker’s compensation

AJR:156, March 1991

AUTOMATED

PERCUTANEOUS

LUMBAR

DISKECTOMY

535

Fig. 9.-Tip of trocar is lying against an imaginary line (whIte line) that joins posterior vertebral bodies when anulus is felt. This ensures that structures such as nerve, colon, and great vessels,

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which

lie anterior

to this line, will not be injured.

Fig. 10.-when lying against anulus, tip of ticcar Is lateral to imaginary line (black vertical line) joining medial border of pedicles. Therefore, thecal sac, which lies medial to this line, will not be injured.

Fig. 11.-A and B, Anteroposterior (A) and lateral (B) views show Nucleotome in a posterocentral position within disk.

claims; or if imaging studies revealed other causes for pain such as severe degenerative facet disease, spinal stenosis, or evidence of a free disk fragment. The criteria for success were stringent, the most essential being patient satisfaction with the results of the procedure. If a second procedure was required, be it another percutaneous diskectomy or an open procedure, APLD was considered a failure. From November 1 984 through May 1 987, 506 APLD procedumes were performed by 1 8 different surgeons. Of he 506 cases, 1 1 cases were lost to follow-up and 327 cases met the prospective study criteria; 1 68 cases were knowingly done that did not meet the protocol and were reported as such by the study group. The mean duration of preoperative conservative care for the study group was 1 1 .5 months, making it extremely unlikely that the symptoms in this patient population would have resolved with further conservative care. In the 327 patients who met the protocol and had followups of 1 year or more, the success rate was 75%. In those patients outside the protocol, procedures were successful in 49%. Of the 81 patients within the protocol for whom APLD was considered to have failed, 41 patients underwent either a laminectomy, a microdiskectomy, or a fusion. Nineteen of these patients underwent another percutaneous diskectomy;

only three of these required a subsequent open operation. If these 16 patients who were successfully treated by a second percutaneous diskectomy are included, the success rate of the procedure rises to 80%. Of the 44 patients who subsequently underwent an open procedure, 30 (68%) had free fragments of disk unsuspected by preoperative imaging. The findings in this study have been reproduced by other investigators. In another prospective multiinstitutional study conducted in Italy [1 6], 650 patients were treated with APLD with a 72% success mate; the selection and success criteria were the same as in the first multiinstitutional study. In a French prospective multiinstitutional study [1 7], 286 patients were treated with a success rate of 78%, again confirming these results. Currently, 1 9 studies comprising over 3600 patients are either published or in press that confirm the results obtained by the initial multiinstitutional study (Table 2). A success rate of 80% or greater was reported in 12 of these and of 70% or greater in 1 8. Only one retrospective study comprising 17 patients reported a success rate less than 70% [23]. Of note is the small number of patients in this study as well as the fact that patients with back pain only were included in this series.

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536

ONIK

AND

The efficacy of APLD appears to compare favorably with the results previously reported with chymopapain injection and open diskectomy, although it is difficult to draw conclusions without a comparative randomized study. In a number of studies, the efficacy of treatment with chymopapain has been reported to be from 40% [39] to 85% [40] and that of open diskectomy has been reported as 77% [41 ] to 99% [42], whereas success rates reported for microdiskectomy (the same approach as a traditional Iaminectomy or laminotomy performed with an operating microscope) have consistently been as high as 95% [43, 44]. It must be pointed out, however, that success in open diskectomy has always been defined as relief of leg pain, disregarding any new or residual back pain that may have been left over or have been caused by the procedure. In the only prospective study meported for microdiskectomy, 25% of patients had chronic back pain after the procedure [45]. In a recent study by

TABLE

2: Results

Automated

of Studies

Percutaneous

the Success

No. of Patients

R esearc hems Onik et al. [i5] Bocchi et al. [16] Benazet and Roy-Camille Maroon and Allen [1 8]

Evaluating

of

Lumbar Diskectomy

[1 71

506 650 286

Success Rate (%) 75#{149}4a

72.0a 78.3

1 054 30 49 50

82gb 83.3 79.0 80.0

200 17 62 94

77.5 53.0 79.0 83.0

[26]

1 00

83.0

CapannaandCapanna[27] Cooney[28j Corkhill et al. [29] Rezaian and Silver [30] Cartolari et al. [31] Kaps and Cotta [32] Davis et al. [33]

iO 50 21 27 24 67 5i8

80.0 82.0 88.0 94.0 83.0’ 82.0 86.0

Lesoin et al. [19] Hammon [20]

Flynn et al. [2i I Davis and Onik [22j Goldstein et al. [23] Gill and Blumenthal [24] Russell et al. [25] Swiecicki

Note-Major diskitis, and

cone

complications comprised “one case of diskitis, btwo cases of case of diskitis and one transient nerve root irritation.

HELMS

AJR:156, March 1991

Hanley and Shapiro [42], 14% of patients had new disabling back pain after open diskectomy. In the only comparative study reported to date comparing APLD with open diskectomy and chymopapain injection, APLD, with its reported success mate of 83% in 1 00 patients treated, was equal to lammnectomy and superior to treatment with chymopapain [25]. Even if the most optimistic success mates reported for microdiskectomy are considered, the difference in efficacy between open diskectomy and APLD appears to be only 101 5%. If APLD is to be a viable procedure, the advantages of the procedure have to outweigh this lower success rate, which appears to be due to missed free fragments of disk material. We believe the advantages of APLD outweigh its slightly lower efficacy for several reasons: (1 ) Its performance under local anesthesia markedly decreases the chance for nerve injury while avoiding the risks associated with general anesthesia. (2) With the postemolateral approach, there is no violation of the spinal canal. Therefore, the procedure is not associated with epidural fibrosis and the chronic pain syndrome that can result. Because of this, a patient in whom percutaneous diskectomy fails can later undergo an open procedure without negative effects. (3) No bone or ligament removal is associated with the procedure; therefore, the chances of postoperative instability are decreased. (4) The disk is entered only once with the automated removal probe. Therefore, APLD is associated with a markedly decreased infection rate compared with open diskectomy. (5) Because of the minimal trauma associated with the procedure, the procedure can be done on an outpatient basis; 70% of patients can return to work within 2 weeks of the procedure [22]. Compared with chymopapain treatment, APLD has a very low prevalence of associated back spasm, with virtually no risk of anaphylaxis or transverse myelitis, which have made chymopapain injection risky. A comparison of the postoperative imaging of APLD with that of laminectomy is interesting. While immediate postoperative resolution of the herniated nucleus pulposus can occur (Fig. 1 2), it has been shown that in most cases the herniated nucleus pulposus appears unchanged even in patients who have obtained symptomatic

Fig. 12.-CT scans before and immediately after automated percutaneous lumbar diskectomy. A, L4-L5 herniated nucleus pulposus is slightiy to the left. (Reprinted from Onik et al. (14].) B, CT blink-mode image immediately after the procedure shows complete resolution of herniated nucleus pulposus.

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AJR:156,

March

AUTOMATED

1991

Fig. 13.-MR

PERCUTANEOUS

scans before and 3 and 15 months after automated

LUMBAR

percutaneous

DISKECTOMY

lumbar diskectomy.

A, Before diskectomy. Protrusion is noted at L5-S1 level (arrow). B, 3 months after procedure, patient is markedly improved and has returned to work; however, herniation (arrow) appears unchanged. C, 15 months after procedure, patient remains asymptomatic. MR shows complete resolution of herniation (arrow). Note that there epidural scarring and disk space has not lost any height.

relief from the procedure [46]. These patients presumably have improved because the herniated nucleus pulposus is softer and exerts less pressure on the nerve. It is possible, however, that it may take longer periods of madiologic followup to demonstrate the morphologic changes in the herniated nucleus pulposus associated with APLD (Fig. 1 3). Long-term radiologic follow-up studies on successfully treated patients are not yet available. What is clear, however, is that APLD is not associated with epidural scarring, which makes postoperative imaging after laminectomy so difficult (Fig. 13). Conclusions APLD has been shown to be both efficacious and extremely safe in treating patients with herniated lumbar disks contained by the anulus and posterior longitudinal ligament. APLD fulfills the most important criteria for an excellent interventional radiologic procedure: a high success mate with minimal associated morbidity. We should not forget that our first goal as physicians is “to do no harm.” APLD has the least potential to do harm compared with other available procedures for treating herniated lumbar disks, thereby making it the procedure of first choice. However, caution must be exercised in the careful selection of patients and attention given to radiologic localization to ensure safe and effective results.

.

American Academy of Orthopaedic AAOS Bull October 1989:13-15

Surgeons

14.

1

5.

1

6.

1 7. 1

8.

1

9.

(AAOS). Policy statement.

2. Stolke D, Sollman W-P, Seifert V. Intra- and postoperative in lumbar disk surgery. Spine 1989;14:56-58

3. Ramirez LF, Thisted A. Complications patients undergoing lumbar gery 1989;25:226-231

and demographic

diskectomy

in community

complications

characteristics

hospitals.

4. Hijikata 5, Yamagishi M, Nakayama T, et al. Percutaneous new treatment 5:5-13

method

for lumbar

disk

herniation.

of

Neurosur-

diskectomy:

J TodenHosp

1975;

is no evidence

of

5. Hijikata S. Percutaneous nucleotomy: a new concept technique and 12 years’ experience. Clin Orthop 1989;238:9-23 6. Hoppenfeld S. Percutaneous removal of herniated lumbar disks: 50 cases with ten-year follow-up periods. Clin Orthop 1989;238:92-97 7. Kambin P. Schaffer JL. Percutaneous lumbar diskectomy: review of 100 patients and current practice. Clin Orthop 1989;238:24-34 8. Monteiro A, Lefevre A, Pieters G. Wilmet E. Lateral decompression of a pathological disk in the treatment of lumbar pain and sciatica. C/in Orthop 1989:238:56-63 9. Schreiber A, Suezawa MD, Leu H. Does percutaneous nucleotomy with diskography replace conventional diskectomy? Eight years of experience and results in treatment of hemiated lumbar disks. C/in Orthop 1989;238:35-42 10. Sheppard JAN, James SE, Leach AB. Percutaneous disk surgery. C/in Orthop 1989:238:43-49 1 1 . Stem MN. Early experience with percutaneous lateral diskectomy. C/in Orthop 1989;238:50-55 1 2. Wilson DH, Harbaugh R. Lumbar diskectomy: a comparative study of microsurgical and standard technique. In: Hardy A, ed. Lumbar disk disease. New York: Raven, 1982:147-1 56 1 3. El-Gindi 5, Arefs AJ. Infection of intervertebral disks after operation. J

REFERENCES 1

537

20. 21 .

a 22.

Bone Joint Surg [Br] 1976:58-B: 114-116 Onik GM, Helms CA, Ginsburg L, Hoaglund FT. Moms J. Percutaneous lumbar diskectomy using a new aspiration probe. AJNR 1985:6:290-293 Onik G, Mooney V. Maroon JC, et al. Automated percutaneous diskectomy: a prospective multi-institutional study. Neurosurgery 1990;26(2):228-233 Bocchi L, Ferrata P. Passarello F, et al. La neucleoaspirazione secondo Onik nel trattamento dellemia discale lombare analisi multicentria del primi risultate su oltre 650 trattamenti. Rh, Neuroradiol 1989:2:119-122 Benazet JP, Roy-Camille A. Automated percutaneous lumbar diskectomy: results of French multicenter study of 287 cases. Rachis (in press) Maroon JC, Allen AC. A retrospective study of 1 .054 APLD cases: a twenty-month clinical follow-up at 35 US centers. J Neurol Orthop Med Surg 1989;10(4):335-337 Lesoin F. Autricque A. Clarisse J, Villette L, Jomin M. La Nucleotomie percutanee automatisee en pathologic discal lombaire. J Chir (Paris) 1989:126:185-188 Hammon W. Percutaneous lumbar nucleotomy. Neurosurgery 1989:24:635 Flynn LM, Morrow RE, Brannon J, et al. Arthroscopically assisted lateral percutaneous lumbar diskectomy using the Onik Nucleotome. J Neurol Orthop Med Surg 1988:9:45-47 Davis GW, Onik G. Clinical experience with automated percutaneous lumbar diskectomy. C/in Orthop 1989;238:98-102

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23. Goldstein TB, Mink JH, Dawson EG. Early experience with automated percutaneous lumbar diskectomy in the treatment of lumbar disk herniations.

24. Gill

C/in Orthop 1989:238:77-82 K, Blumenthal SL. Clinical experience

diskectomy-the

Nucleotome

system.

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25. Russell GS, Highland 1, Dreisinger

26.

27.

with automated

Orthopedics

T. Percutaneous

one-year follow-up in private practice. Surg Rounds Orthop (in press) Swiecicki M. Results of percutaneous lumbar diskectomy compared to laminectomy and chemonucleolysis. In: Mayer HM, Brock M, eds. Percutaneous lumbar diskectomy. Berlin: Springer-Verlag, 1989: 133-1 37 Capanna AH, Capanna DM. Correlations of amount of disk removed by percutaneous lumbar diskectomy and clinical results. In: Mayer HM, Brock M, eds. Percutaneous lumbar diskectomy. Berlin: Springer-verlag, 1989: 138-1 40

ger-Verlag, 1989:163-168 Corkhill G, Kimple J, Corkhill A. Automated percutaneous nucleotomy by pain scale. In: Mayer HM, Brock M, eds. Percutaneous lumbar diskectomy. Berlin: Springer-verlag, 1989: 169-1 72

30. Rezalan SM, Silver ML. Percutaneous

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