Surgery for Intervertebal Disk Disease of the Lumbar Spine LEONL. WILTSE,M.D.*

What follows represents our group’s opinion as to what yields the best clinical results gained from experience with a large number of patients over many years.52 The indications for laminectomy have been well established in many previous publicat i o n ~ In . ~ general, ~ patients with intractable low back pain and sciatica are candid a t e ~ .40~ An ~ * adequate trial of conservative non-operative therapy should, of course, be given. Lapse of time is probably the single best indication that the pain will not leave without surgery. Detailed training in low back care and in the performance of the activities of daily living and training in isometric abdominal exercises are the most commonly used modalities of conservative care.34 However, the whole gamut of conservative treatment is employed. This includes necessary analgesics and muscle relaxants, traction in the hospital, epidural injections,Z3 facet injection~3~0 32 and rarely intradiscal injections with steroids.15 During the past 10 years, we have been giving all our patients a battery of psychological tests before surgery50 and many have

been put through a low back program which concentrates on training in low back care, in the activities of daily living and especially psychological counseling, particularly if the psychometrics are unfavorable. The most important single requirement for laminectomy is that the patient’s pain be severe enough and of long enough duration to warrant this rather major surgical procedure. Ordinarily no harm comes from deferring laminectomy as long as pain is the principal problem and severe progressive motor paralysis or paralysis of the bowel or bladder is not present. The exception to this rule is that, if one has reason to believe that a large extruded disk is present along with neurological change, the fragment should be removed even though pain is not forcing its removal. We believe arachnoiditis develops in a significant percentage of patients who have large extruded disks which have not been removed for several months.19 Progressively increasing neurological deficit despite complete bed rest, especially if there is bowel or bladder paralysis, is an absolute indication for laminectomy.25.29 Severe low back pain and sciatica unrelieved by complete bed rest or recurrent episodes of incapacitating back pain and sciatica are relative indications in that, while they may very well be indications for laminectomy, operation can be deferred if the patient prefers.

*2840 Long Beach Blvd., Suite 410, Long Beach, California 90806. From the Long Beach Memorial Hospital and Medical Center. Supported in Part by Research Grant No. 196, 223. Received: April 12, 1977. 22

Number 129 November-December, I977

No effort will be made in this chapter to discuss every aspect of surgery for lumbar disk disease. Nor will I discuss chemonucle0 1 y s i s ~49~ except ~ to mention the procedure which in our opinion is a valuable one but at the present time is not approved by the Food and Drug Administration. The exact cause of low back pain and especially diskogenic pain is not well understood. It would appear to be far too complex to be accounted for by simple mechanical pressure or by instability. However, in the present state of our art most surgery is directed toward either removing pressure from certain spinal nerves or stiffening a few segments of the bony spine by arthrodesis. In order that there will be absolutely no misunderstanding as to just what is being recommended, it is necessary to define some of the anatomical terms which will be used in this article. Laminectomy (Fig. 1A) refers to removal of all the bone between the base of the spinous process and about 1 cm medial to the facet. The pars interarticularis is spared. If a bilateral laminectomy is done, both laminae are removed. The spinous process is of necessity removed. If laminectomy and facetectomy (Fig. 1B) are performed, one lamina starting from the base of the spinous process out including the inferior articular process of that lamina, the pars and a portion of the superior articular process of the vertebra below are removed. FIOS.1B and C. (B, left) Laminectomy and facetectomy. (C, right) Bilaminotomy. Area of bone removed in doing an ordinary discectomy. Since two laminae have been cut through, it must be called a bilaminotomy. The medial swing of the superior articular process of L-5 (not shown here) is nipped off.

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23

FIG.1A Total laminectomy This amount of bone removal gives rather complete unilateral decompression and 2 spinal nerves are completely unroofed. Laminotomy (Fig. 1C) refers to cutting through a portion of one lamina. Since, in the ordinary disk operation, 2 laminae which are lying side by side are cut through to remove the disk, this could more correctly be called a bilaminotomy. If a foraminotomy is done in addition to a laminectomy, the pars interarticularis and a portion of the articular processes where

24

Clinical Orthopaedics ond Related Research

Wiltse LOW BACK SUMMARY Name

Duration

Date

Cause Significance Low Back

HISTORY ..- . - . .

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Neg. or Normal 90

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Slight

Moderate

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Oil Water SOI. SPINAL FLUID PROTEIN BONE SCAN

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P R E V I0US T R E ATM E NT

INTR AlllCPAl CTCRnlIl .,., ..-l."..--".C..-.l

SCIATIC STRETCI"*'c FACET INJECTIOb CHEMO L.3.4, 5 LAM.

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NOTICE TO MEDICAL RECORDS: RETURN TO: 2840 Long Beach Blvd.. Long Beach, Ca. 90606

'rABLE 1. Low back summary. This form is started in the doctor's office on the patient's first visit. Items are added as they become available. It accompanies the patient's history and physical to the hospital and items are continually added as various tests and studies are performed. When the patient leaves the hospital, the form is returned to the doctor's office and is there on the patient's return visits. It serves as a ready summary at all times. It is not intended to be complete. One must refer to the clinical chart and study the X-rays, etc. for completeness.

Number 129 November-December, 1977

Disk Disease Surgery

25

as yet of no help in diagnosing a ruptured disk but it is my ,belief that remarkable advances will be made in the next few months. Psychological studies. We have done psychological studies on all back patients since 1968.50 These have been of value in deciding on surgical treatment for the patient with severe subjective complaints but equivocal organic findings. In these patients surgery should be deferred if possible. Since psychological studies are done as a routine, patients ordinarily don’t object to them. Before surgery, most patients are sent to the low back program for more thorough training in back care, in how to perform the activities of daily living and, if they have unfavorable psychological studies, for psychological counseling. This is started before operation if possible. SELECTION OF PATIENTFOR LAMINECTOMY That way, as soon after the operation as the When a patient who seems to be a possible patient is able, he can rejoin the low back procandidate for laminectomy is seen in the office, gram. in addition to the physical examination, the Myelogram. A myelogram is done in all following studies are usually done: cases when surgery is contemplated but never Plain X-rays are always taken and are valuuntil 36 both the doctor and patient have come able in ruling out such things as metastatic disto the conclusion that surgery is indicated. ease, spondylolisthesis, bony infection, etc. They THELow BACKSUMMARY SHEET (TABLE1.) are also of help in deciding wether the patient has spinal stenosis. However, the presence of A low back summary sheet is started on all most of the congenital and other structural variback patients the first time they are seen. This ations are of little consequence. is a means of putting down on a sheet of paper If it appears that the patient is a candidate all details of the case. Every time a new bit of for surgery, he is sent to the hospital for furinformation is obtained, it is entered on the ther studies. An electromyogram is taken along sheet. A copy of this accompanies the patient with an epidural venogram, psychological studto the hospital so that it is present each time he ies and possibly a computerized axial tomois seen. This gives a readily available up-todate graph. summary of all the isolated facts about a given Electromyogmm. The EMG yields good patient, whether he is on the ward or in the confirmatory information and has the distinct office. It is returned to the office when he advantage of being harmless. leaves the hospital. Epidural Venogram. The epidural venogram THEOPERATION has been an extremely valuable test. We have done over 400 so far without one single compThe position of the patient on the operating lication of any note. If the venogram is negitive, table makes a great deal of difference as rethen the patient does not have a herniated disk gards the amount of bleeding that will come in the lower 3 segments and one need not profrom Batson’s plexus 24. The so-called Canadceed to a myelogram unless something besides ian frame designed by Hastings and others proa ruptured disk is suspected. It is slightly more duces by far the least pressure on the veins of sensitive than the myelogram and thus more Batson (Fig. 2). false positives occur but it is an excellent Di Stefan0 and associates measured the rescreening procedure and can be done on an lative pressure in the vena cava when simple ambulatory basis. bolsters, a Wilson frame or a Canadian frame Computerized axial tomography. Recently we was used 8. Of the 3, the Canadian frame prohave started doing computerized axial tomoduced by far the least pressure. We have found graphy on patients suspected of having spinal from experience that this frame has striking advantages. Note that this is not the knee-chest stenosis. It is too early to make a final evaluaposition. The knee-chest position should be contion of this modality but at this juncture it demned because of the possibility of vascular seems that it may have very real value. It is

they come together forming the facet are removed. The use of the term nerve root describing the spinal nerves in the lumbar area is thoroughly ingrained in our terminology but is slightly incorrect. T h e roots are either posterior sensory or anterior motor. As they penetrate the dura they are insheathed as far as the ganglion in a dural extension called the vagina radicis. Beyond the ganglion there is a short section called the spinal nerve which separates into the anterior and posterior rami. T h e anterior rami form the lumbosacral plexus.

26

Clinical Orthopaedicr and Ralatad Research

Wiltre

TABLE 2.

Classification of Spinal

Stenosis 1. Congenital-Developmental a ) Idiopathic b) Achondroplastic

FIG.2. This frame was designed by Hastings and others. The patient is in kneeling position (never knee chest.) This position is extremely helpful when working around the spinal nerves since it reduces the pressure in the-veins of Batson to nearly zero. The chest support can be raised or lowered by turning the removable crank.

damage during the long period of severe flexation of the knees. In doing a laminotomy, a midline approach is made. Both sides are exposed down to the laminae. We believe in a fairly extensive bony decompression in every case, even for the most simple disk excision (Fig. 3). As seen in Figure 3, we trace the spinal nerve well out along the canal. The tip of the facet of the superior articular process of the vertebra below is nipped off, but we avoid cutting through the pars interarticularis as this would unstabilize the posterior elements. SPINALSTENOSISSECONDARY To DEGENERATIVE DISK DISEASE Spinal stenosis is a condition in which there is too little room in the bony canal for the neural contents. The compression may be in the central canal or the lateral canal or both. It is likely that symptoms are more often caused by stenosis of the lateral canals. Table 2 gives a brief classification of spinal stenosis developed by Kirkaldy-willis26 with the help of a group of 20 other surgeons around the world. DISCUSSION Since this symposium is devoted to degenerative disk disease, I will discuss surgery of acquired stenosis - in particular, “de-

Stenosis

2. Acquired Stenosis Degenerative i) Central portion of spinal canal ii) Peripheral portion of canal, lateral recesses and nerve root canals (tunnels) iii) Degenerative spondylolisthesis. Combined Any possible combinations of congenital/developmental stenosis, degenerative stenosis and herniations of the nucleus pulposus. Isthmic spondylolisthesis latrogenic i) Post laminectomy ii) Post fusion (anterior and posterior) iii) Post chemonucleolysis Post-traumatic, late changes Miscellaneous i) Paget’s disease ii) Fluorosis

From Lumbar spinal stenosis and nerve root entrapment syndromes-definition and classification. By W. H. Kirkaldy-Willis, Clin. Orthop. No. 115: 92, 1976.

generative stenosis” and “combined stenosis.” I will specifically leave out spinal stenosis secondary to isthmic spondylolisthesis and to trauma. However, the basic principles set down for the types discussed here apply to all types of spinal stenosis. Some degree of spinal stenosis is very common in the human being. It is significant that most elderly people find it impossible to lie on their abdomens with any degree of comfort. It is probable that the slight decrease in the size of the spinal nerve canals produced by this relatively small amount of hyperextension is the cause of their discomfort (Fig. 4). It is only when the discom-

Number 129 November-December. 1977

fort is noted with ordinary living that a physician is consulted. The classical signs and symptoms of spinal stenosis have been well described and are clearly recognizable. z l 3 , 9 9 1 2 e 1 3 1 2 1 s 4 2 They are ( 1 ) pain in the back with either claudication or sciatic type pain in the legs.35 ( 2 ) decreasing ability to walk noted over the past 2 years. (3) pain on standing with relief of pain especially by lying down, but often by sitting down. (4) cramping and pain in the calves on walking for short distances. ( 5 ) if walking is continued, paresthesia and numbness in the legs becomes unbearable. (6) However, riding a bicycle can be done often for long distances. (7) walking up hill is easier than walking down hill. (8) gait becomes unsteady. (9) any more than a minimal amount of hyperextension of the low back is impossible because of pain. (10) the patient is usually (but by no means invariably) past 50 and may be either male or female. It has been our observation that, once the patient has severe symptoms from spinal stenosis, he does not get well with time as does the younger patient with a herniated disk.44Surgery seems to be the only solution. The elderly patient withstands lumbar spine surgery very well and should not be denied its rather remarkable benefits because of age. The clinical results as regards relief of pain in the elderly are better than in the 30-50 age group. This may be because these people have come to terms with life. They are usually under no pressure to get back to work. All they need is relief from pain.51 Of course, many have symptoms that are not so severe that surgery is warranted. These may be benefitted sufficiently by a course of conservative therapy that surgery can be postponed. Conservative treatment can safely be carried on as long as the pain is tolerable.' Only rarely do patients with lumbar spine stenosis have neurological changes which in themselves warrant surgery. (This is not true in the cervical spine stenosis.)

Disk Disease Surgery

27

-

FIG. 3 Classical diskectomy. We believe this amount of bone should be removed when a diskectomy is done. Note the medial swing of the superior articular process of L-5 has been nipped off.

The primary aim of surgery is to remove the pressure from the neural elements whether in the central canal or the lateral canals. In making the diagnosis of spinal stenosis. the history and the myelogram are the most FIG.4. Tracings of typical lateral X-rays of the lumbosacral area taken with the patient standing and lying in the fully extended position. Note the rather definitely increased lordosis and the narrowing of the L-5 disk space on standing compared with the horizontal position. This may explain why the person with spinal stenosis is so often relieved by lying down.

28

Clinical Orthopaedicr and Related Research

Wiltse

FIG.5A. In the so-called “rosary” spine, the decompression must be adequate yet the pars should be saved if possible.

F I ~5B. . Midline decompression. This is the type of decompression most frequently done by us. The pars and most of the facets are saved. The medial portion of the superior articular process is nipped off as it swings medially posterior to the spinal nerve. Stability is preserved. Removing the spinous processes seems to produce no clinically noticeable adverse effects. The L-5 spinal nerve is the one most frequently compressed in the lateral canal.

important. As stated above, use of the transaxial tomograph is being investigated and appears to have real value. The history, though often vague and apparently non-specific, may for these very reasons be diagnostic. The myelogram shows central canal stenosis very well but does poorly in diagnosing stenosis in the lateral canals. Water soluble myelography may do better because it is thinner. The spinal fluid protein is very often elevated. The physical examination may at times present all the typical changes of neural compression but more often is surprisingly negative. If a really accurate diagnosis of a single level of nerve compression is possible, a limited decompression is feasible. More often it is not possible to know the exact level causing the compression and a several-level decompression is necessary. In the case of degenerative stenosis as seen in Figure 5A, a midline incision is made. The spinous processes are removed along with the laminae out to 1 cm medial to the facets (Fig. 5B). The facets are saved. The number of levels to be decompressed is determined by the myelogram principally but at surgery, the laminae should be removed at enough levels to reach an area where the dura is pulsating and the epidural fat appears normal. The rule is decompress as much as necessary and, if you must err, err on the side of too much decompression. Where there is no congenital element, degenerative spinal stenosis is inclined to encompass only the lower 3 segments (Fig. 5C). Diskectomies are done at the levels where the annulus presents unmistakable signs of a soft herniated disk. If the annulus is hard even though bulging, a diskectomy is not done. It is better not to enter a disk space unless really necessary since entering the space tends to scar the spinal nerve and to increase instability. The L-5spinal nerve is in double jeopardy.

Number 129 November-December, 1977

It may be trapped between the superior articular process of L-5 and the lower rim of an osteoarthritic L-4 body. Or, in cases of isolated disk resorption at the L-5 disk space, it may be trapped between the superior articular processes of S-1 and the lower rim of the L-5body. The tips of these facets should be nipped off but the major part of the articulation can be saved. The S-1 spinal nerve is in less danger in the case of the osteoarthritic spine but it too should be cleared of overlying bone down into the upper sacrum. The superior articular process of the sacrum probably cannot entrap the S-1 nerve between itself and its own body but, if in doubt, free the nerve. The spinal nerves may be compressed far out laterally in the canals. In these cases it may be necessary to decompress in front of the nerve if posterior stability is to be saved. To do this, it is necessary to remove the osteoarthritic build-up in front of the spinal nerve. Although difficult, this can be done and still save the pars, and thus the posterior stability (Fig. 6). In order to remove bone from in front of the nerve, it is necessary to have removed the lamina and the spinous

Disk Disease Surgery

29

FIG. 5C. Massive decompression L-3, 4 and 5. Note the pars have been saved as have the facets. Olisthesis will seldom occur if this much bone is saved.

process. Tiny straight and curved chisels are valuable and the field must be relatively blood-free. It is enormously advantageous to have the patient in the kneeling position. The bi-polar cautery is also of great advantage when working close to the spinal nerves. Some find it advantageous to use magnifying glasses and special headlamp. We have designed some little nerve protectors which we find helpful (Fig. 7). These can be slipped along the spinal nerve out in the canal to protect it while bone is being removed. Four of these are necessary to fit the superior and inferior surfaces of the nerve on both the

Fro. 6 (left). Removing bone from in front. Note how the spinal nerve is trapped between the superior articular process of the vertebra below and the exuberant rim of bone of the vertebral body above. (right) Removal of bone and annulus anteriorly must be done from the medial side. The spinal nerve must be mobile. The spinous process must be removed along with a bilateral laminectomy. The pars and articular processes are preserved. (From Treatment of spinal stenosis by Leon L. Wiltse, W. H. Kirkaldy-Willis, G. W. McIvor. Clin. Orthop. No. $15, March 1 April, 1976, Fig. 4, p 86).

30

Clinical Orthopaedicr and Relafad Research

Wiltse

FIG.7. Nerve protectors. These are shaped to fit the curve of the nerve. They can be slipped in between the spinal nerve and the bone wbile bone is re-

moved

from

the

canal. Four are required to fit the

cephalad and caudal sides of the nerves on both the right and the left.

right and left. The osteoarthritic ridges along with a portion of the annulus are removed. The lower border of the pedicle may at times also be removed. In our experience in the lumbar area it has not been necessary to enlarge the dura by a graft or artificial membrane. Often it is difficult or impossible to decompress in front of the spinal nerves. This is especially true if there is scarring from previous surgery. If it is not possible to decompress the nerves and still save the pars,

FE. 8A. In this case there is a severe area.

it is permissible to make an open channel out along the nerve, doing a foraminotomy. This completely unstabilizes the spine posteriorly. In these cases one should not also do a diskectomy at the same level or there will be too much instability. Once all bone is removed posteriorly, it is not necessary to remove the disk anteriorly unless there is a soft herniation and, if so, one would not likely be doing a foraminotomy. The question might be asked if all posterior stability has been removed on 1 side, should not the same also be done on the other side to prevent cam action on rotation?I4 We have not felt that this is sufficient reason to routinely remove the articular processes on the painless side and, if all pain is unilateral, we leave the pars and facets on the painless side. Figures 8A and B show the rather complete massive posterior decompression which should be done in cases of severe degenerative stenosis in the very elderly where there is near total block at several spaces. In these cases we feel it is better to decompress completely posteriorly even though the posterior stability supplied by the posterior elements is lost. It happens that the severe osteoarthritis has produced enough stability so that development of iatrogenic spondylolisthesis is not likely, unless degenerative spondylolisthesis is present before operation. However, it does occur fairly often if complete foraminotomies are done bilaterally at a level where the width of the disk space is reasonably normal, especially if in addition the disk space is entered (Figs. 9A-C). Note the iatrogenic spondylolisthesis in Figure 9C but also note the nearly normal width of the L-4 disk space before surgery. The more osteoarthritic build-up there is, the more one needs to decompress posteriorly and fortunately the safer it is to do so because of the stability which has developed.

Number 129 November-December, I917

Disk Disease Surgery

31

Figure 8 shows a case where total decompression was necessary and where, because of the severe osteoarthroses, one need not bc concerned about iatrogenic spondylolisthesis. ISOLATEDDISK RESORPTION Crock has described isolated disk resorption.6 This is a condition where one disk space, usually the fifth, virtually disappears but the fourth remains reasonably normal as are those above. The patient develops spinal stenosis localized to one level. The pain may be unilateral or bilateral. If the diagnosis of nerve root compression secondary to isolated disk resorption is accurate, decompression serves very well. The decompression should usually be done bilaterally even though the symptoms are unilateral. It may be that the pars and the facets can be saved and the spinal nerves (in this case, L-5) channelled by removing the bony lipping, thus enlarging the passageway for the nerve. However, in these cases, our preference if in doubt is to completely unroof the nerves since, with the very narrow disk space which is the rule with these patients, stability is not a problem. DEGENERATIVE SPONDY LOSIS Degenerative spondylolisthesis results from forward slip of the entire vertebrae (Figs. 10A and B). The pars is intact. The most frequent site is between L-4 and L-5 with L-3 next in order of frequency.38 When the slip occurs at L-4, the L-5 vertebra is usually more stable than average and is block shaped. The lumbosacral angle is often reduced and the body of L-4 sits higher than average.16 It occurs 6 times more often at L-4 than at the next most frequent level, L-3. It occurs 5 times more frequently in women than in men.39 Sacralization of L-5 is 4 times more frequent in people with degenerative spondylolisthesis than in the general

FIG.8B. Total removal of the posterior supporting structures as shown in this drawing is not commonly done. When it is done, it is usually in cases who have had multiple operations - perhaps with anterior interbody fusion so that stability is not a problem. Even with this degree of bone removal, iatrogenic spondylolisthesis seldom occurs in the case with congenital stenosis or with ordinary degenerative arthritis, especially if there is considerable narrowing of the disk spaces with osteophyte formation. If olisthesis does occur it will be at L-4 or L-3-virtually never at L-5. (From Treatment of spinal stenosis by Leon L. Wiltse, W. H. Kirkaldy-Willis, G. W. McIvor. Clin. Orthop. No. 115, March /Apail, 1976, Fig. 5, p. 87).

population.38 Degenerative spondylolisthesis has not been reported below age 40. Treatment of stenosis due to degenerative spondylolisthesis. Symptomatic therapy will be adequate in the vast majority of patients who come to the doctor’s office but, when the pain is unrelenting and constant, surgery is most gratifying. Advanced age is not a contraindication. Pain is the primary indication for surgery.

32

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Clinical Orthopaedicr and Related Research

FIGS.9A-C. (A, left) Rather marked stenosis in a 67-year-old male. There was a d,isk extrusion at point of arrow. (B, center) The rather large decompression had already been done before the extruded disk was found. (C, right) Note the olisthesis which has developed 9 months post operation. This will happen fairly often if the dmisk space is wide and all posterior support is removed. especially if in addition the disk space is entered to curret the nucleus. Note that the olistheses developed at the L-4 space. It seldom develops at L-5 even though total removal of the posterior elements has been done at that level.

Many patients have no neurological deficit. A very few have rather severe changes. Even the EMG may be negative. The myelogram is dramatically abnormal and the spinal fluid protein is usually elevated. Circulatory change in the legs is not part of the syndrome, The inferior articular processes of L-4 at the level of slip are markedly enlarged and the enlargement gives them the appearance of being closer to the midline than average. The bone has an unusual granular appearance. The L-4 spinal nerve which passes out at the level of slip (when the olisthesis is at L-4) is seldom involved.39 In 23 cases which we have reviewed there was only one instance of slight involvement of the L-4 spinal nerve noted on the EMG and this was in a patient who had had a previous chemonucleolysis and the EMG changes may have been due

to slight nerve injury by the needle at the time of injection. It has been our custom to decompress as in Figure 11. We save the lateral % of the zygopophyseal joints at the level of olisthe~ i s . 5Even ~ so, further olisthesis at this level will usually occur. Occasionally in removing the lamina, the inferior articular process of the vertebra above is broken off.39To avoid this, Rosenberg has suggested that a motor saw be used to cut part way through the b0ne.~9 Rosenberg,39 and Fitzgerald and Newman16recommend the smaller area of decompression shown in Figure 12. They believe that removing the distal '/3 of the lamina and spinous process of the olisthetic vertebra and the proximal '/z of the one below will give sufficient decompression. Two questions naturally arise - is this an adequate decom-

Number 129 November-December. 1977

Disk Disease Surgery

33

FIGS.10A and B. Lateral and A P myelogram of a typical case of degenerative spondylolisthesis at L-4, showing a subarachnoid block.

pression? Will it prevent further olisthesis any better than a somewhat longer decompression as shown in Figure 10. One thing is certain and that is, if the articular process is inadvertently broken off on both sides, in a patient who does not have a very narrow disk space at that level, further olisthesis will invariably occur. If, in addition, the disk is entered at the level of olisthesis and a generous portion of the posterior longitudinal ligament cut, further slip may be very severe and thus should never be done. Even with increased olisthesis the L-4 nerve is not impinged because it occupies the upper half of the neural canal. If the patient is below 65, we do a transverse process fusion at the olisthetic level (Fig. 13). This produces stability if arthrodesis is achieved. If the lateral masses and facets have been preserved, the incidence of successful arthrodesis is satisfactory. There may be a thickened, scarred, blanched dura with an absence of fat at the level of compression. Often the dura will not pulsate at this level. Decompression should be large enough to get above and below this area. The question has often been asked does increased olisthesis cause increased symp-

toms? We do get the impression that those who have severe increased slip tend to have a grumbling back. However, the claudication and sciatica are gone. This residual back pain is usually tolerable and may be helped by a corset.

FIG. 11. This drawing shows the area of decompression which we have been doing in cases of degenerative spondylolisthesis with severe block.

34

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Clinical Orthopaedicr and Related Research

removing all compression. The exception would be if one intended to do an Albee typc graft between the remaining portions of the spinous processes of L-4 and L-5 as described by Fitzgerald and Newman.l6 In that case it would be advantageous to keep the gap as small as possible.

FIG. 12. In this drawing of degenerative syondylolisthesis decompression has been done as recommended by Rosenberg and Fitzgerald and Newman. This smaller amount of decompression cuts away as much support as does the larger decompression but may be advantageous if a n inter-spinous fusion is to be done as advocated by Fitzgerald and Newman. I n which case fusion is easier because the remaining portions of the spinous processes of L-4 and L-5 are closer together. (From Degenerative spondylolisthesis, surgical treatment by N. J. Rosenberg. Clin. Orthop. 117-1 12, 1976.) ( From Degenerative spondylolisthesis by J. Fitzgerald and P. Newman. J. Bone and Joint Surg. Vol. 58-B. No. 2, p 184, 1976.) The area of actual compression in L-4, L-5 degenerative spondylolisthesis is between the inferior articular processes of L-4 and the upper edge of the body of L-5 (Figs. 14 A-D) . The amount of bone which must be removed probably need not be terribly extensive. The problem is that, once even the smaller amount of bone has been removed, the connection is broken and further olisthesis may occur. So one may as well do a bilateral laminectomy of both L-4 and L-5 and thus be absolutely certain of

CASES WITH PREVIOUS POSTERIOR FUSION BUT WITH RESIDUAL SYMPTOMS If the patient has a solid posterior lumbar fusion and still has severe residual symptoms, surgery may be resorted to. The following procedure is usually followed. Very complete studies are done to see if we can pick up the area of stenosis. Occasionally we do a diskogram above the area of fusion, not with the idea of finding a degenerated disk because the disk probably will be degenerated but to see if we can reproduce the pain at the time of diskogram. If so, this gives us a clue that the pain may be coming from the area above the fusion. This is the so-called saline acceptance test. More often than not, we find the area above the fusion not to be the cause of the pain. We then know that the problem is down in the fusion area. If we decide on surgery, the patient is sent to the low back program so as to get him introduced to the program. If the sciatica is unilateral, unilateral decompression is done, completely freeing the nerves as in Figure 15A. It is not necessary to remove the fused bone clear to the midline but one should concentrate on decompressing the nerves out laterally in their canals. We remove all bone and free the nerve completely, clear out to the lateral sides of the vertebral bodies, carefully preserving a strong fusion. If the sciatica is bilateral and the fusion is solid, then we trace the nerves out on both sides (Fig. 15B), still preserving the fusion. This is easily done if the fusion is wide but, if there is a narrow posterior fusion, then we must channel out along the nerves under the

Number 129 November-December, 1977

fusion and still preserve the solidity of the arthrodesis. Often, when one finishes, the nerves are lying in the channels of raw bone. Gel1 foam is packed between the nerves and the raw bone.28 If the patient has had attempts at fusion which have,failed, then we have another problem. If only one attempt at fusion has failed, our tendency is to decompress the offending nerves and rearthrodese. The offending nerve may be localized by a selective nerve block. This fusion is usually done through the paraspinal approa~h.~59 47 This approach gets out into virgin territory and makes it possible to decompress the nerves farther laterally. Also our fusion rate has been considerably better, probably because the circulation to the laminae and the residual stability are better maintained. If the 2 previous attempts to get fusion have failed, we are likely to ignore fusion and concentrate on decompression, being sure all the spinal nerves are completely decompressed clear out beyond the foramina.52 Wound closure. If there is a rent in the dura, this should be carefully closed even if it is only the size of a needle hole as spinal fluid may continue to leak when the patients stand up. A sinus, leaking spinal fluid out through the skin, may develop. The musc!e

Disk Disease Surgery

35

FIG. 13. In patients who have a wide disk space at the olisthetic level, further slip is virtually inevitable. Unless there is a contraindication. we do a fusion as shown here.

and fasical layers likewise should be closed well. We had a patient who developed a subarachnoid infection through a single hole in the dura made by an 18-gauge needle during myelography . Medium-sized siliconized drains (3.2 mm)

FIGS.14A and B. (A, left) Drawing of a parasagittal section through the area of olisthesis in degenerative spondylolisthesis. Note how the inferior articular process of L-4 compresses the L-5 nerve between itself and the upper border of the body of L-5. (B, right) Drawing from a computerized axial tomograph of degenerative spondylolisthesis at L-4. Note again how the inferior articular processes of L-4,compress the L-5 spinal nerves (not the L-4 spinal nerves).

36

Wiltse

FIG. 14C. The cross-hatched area of bone is

removed. are left in for 48 hours if there has been no spinal fluid leak. If there has been a leak, even though repaired, we compromise and remove the drains after 12 hours.

FIG.14D. The small stippled area represents the inferior articular processes of L-4 as seen in cross section. One can readily see why the remaining portions of the inferior articular processes of L-4 often break during surgery unless great care is exexised.

Clinical Orthopaadics and Related Research

We believe early postoperative drainage important because we have had 2 cases who after decompression developed a very tense hematoma, causing partial paralysis in the legs. If this complication should occur, the hematoma should be evacuated immediately, a search made for the bleeder and the wound reclosed but drained very well. Postoperative cure. Anti-embolism stockings are worn and the patient is trained to exercise his ankles, He is allowed up as soon as possible. For the first 2 weeks his feet are elevated during the time he is in bed. At this moment we are giving each patient 20gr of aspirin by suppository twice a day until he can eat well and then 10gr of Bufferin orally twice a day until he leaves the hospital. If the nerves have been exposed over a considerable area, passive stretching of the legs is done by having the feet put in supports attached to ropes and pulleys which he can pull with his hands. This he continues even after going home, This is passive and not active exercise. Active exercises are too painful and are less effective. He is started on isometric abdominal exercises and then enrolled in the low back program as soon as able. This is a 3-pronged program. It encompasses physical therapy, occupational therapy and psychological therapy. The psychological counseling and operant conditioning portion of the program are the most important.

LUMBAR SPINALFUSION The place of spinal fusion in the treatment of lumbar disk disease has been the subject of some critical reexamination during the past 1 2-1 5 years.48 It was felt at one time that a solid fusion assured a painless low back. If pain persisted, then the fusion was not solid and an exploration should be done to find the pseudarthrosis and rearthrodese the area. I n the light of present information, it would appear . - that

Number 129 November-December, 1977

Disk Disease Surgery

37

FIGS.15A and B. (A, left) Unilateral decompression of fusion. If the pain is unilateral and the arca is solidly fused, the nerves arc completely decompressed on one side only, taking care to preserve the solidity of the fusion. (B, right) Bilateral fusion decompression. If the pain is bilateral and the fusion is solid, the midline is decompressed. Often the nerves must be channelled to get enough decompression. Extra bone removed from the midline may be placed out laterally to reinforce the fusion.

this attitude is not justified. We are seeing many cases who have an unquestionably solid fusion yet persist in experiencing severe pain. There is no doubt that the child or young adult with spondylolisthesis responds well to fusion. Likewise, the case with instability due to fracture-dislocation or the one with tuberculosis does well with a fusion. However, in disk disease where pain alone is the problem, the value of the spinal fusion is in question. For many years a narrowed disk space was considered an indication for the addition of a spinal fusion if a laminectomy were to be done. Yet following laminectomy or chemonucleolysis, 79% of the disk spaces will narrow at least 0.5cm.j2 If this line of reasoning were to be followed to its logical conclusion, then every laminectomy or chemonucleolysis would have to be followed by a fusion. While statistics vary, not over one in 10 laminectomy patients came to reoperation even 25 years ago when belief in spinal fusion was at its zenith and in our experience with 1600 cases of chemonucleolysis where we now have a 9-year experience, only one in

18 of our private primary cases have required any further surgery. Many of the common anomalies of the low back, either congenital or acquired, which were once considered indications for spinal fusion, are no longer thought to be. In the past most patients who failed to obtain relief from laminectomy underwent decompression ot the apparently offending nerve root along with fusion from L-4 to the sacrum. Fusions from L-3 to the sacrum are almost a thing of the past in our practice, mainly because in the adult we were getting such a low incidence of solid arthrodesis when all 3 levels were attempted. At present, if a laminectomy has failed and another surgery is done, we are likely to repeat the laminectomy but do a wide decompression. Only when this fails also, do we consider spinal fusion. Thus spinal fusion is the third operation in the series, and third operations on the spine notoriously yield poor clinical results. All our patients are carefully tested psychologically and, if these tests indicate that surgery for the relief of pain is not likely to be successful, fusion is not often performed. This further reduces

38

Wiltse

Clinical Orthopardicr and Related Research

FIG.16. Area of fusion when a midline approach is made.

by a sizeable percentage the number who might have had a fusion. The paraspinal approach for lumbar arthrodesis. When we do perform a fusion? we usually use a paraspinal approach.45:47 In this operation, a midline skin incision is made since most of these patients have already had a midline incision and we are loathe to make 2 more scars. Once through the skin however, we retract the skin and go paraspinally through the muscle. Essential to the paraspinal approach is that the muscle be split approximately 2 finger-breadths lateral to the midline so that soft tissue attachments remain on the spinous processes. This retains more stability but also saves some circulation to this part of the posterior elements. It also makes exposure further out laterally easy and is convenient for decompressing the nerves. Actually decompression of the nerves far out laterally is easier through a paraspinal approach than it is through the midline. The midline approach for lumbar arthrodesis. There are still many occasions when spinal fusion is done through a midline approa~h.~OThe following is the technique which we have used for many years (Fig. 16). The patient is placed on the Canadian

frame. A midline skin incision is made. The muscles are stripped subperiosteally from the sides of the spinous processes and the laminae. Care is taken not to extend the stripping higher than the vertebra that is to be fused. The facets are denuded of capsule and the cartilage in the outer % of the facets is excised. The fusion is extended to the tips of the transverse processes. The posterior primary divisions of the lumbar nerves along with the posterior extensions of the lumbar arteries and veins come posteriorly just above the bases of the transverse processes and also at the cephalomedial corner of the ala of the sacrum, These are always cut. If bleeding is a problem, these bleeding holes can be plugged with a wad of surgicel until bleeding stops. The bipolar cautery is of use in coagulating these bleeders. A good deal has been said about the production of spinal stenosis if the posterior surfaces of the lamina are feathered and covered with bone. Anterior growth of bone may occur at the top of a fusion or at a point of nonunion but we believe simple anterior growth of bone from the front of a lamina or the front of the posterior wall of the sacral canal does not occur secondary to bone grafting.

Number 129 November-December, I977

Posterolateral fusion of the lumbar spine using Knodt rods. KnodtZ7rods which are really a modification of the Harrington rods are being used in lumbar spinal fusions. Usually these are put in in such a way as to spread the vertebrae, thus opening up the foramina for the nerve roots. The following X-ray demonstrates the method of placing the Knodt rods (Fig. 17). Our experience has not been great using this method but it may be a valuable adjunct in the treatment of the patient who still has pain after previous surgery. In the cases where we have used these rods, the fusion rate has been extremely high. Since the Knodt rods used as distraction open up the foramina and stabilize the spine quite well and fusion takes place readily, at least theoretically they should be helpful. However, Dubuc et al. reviewed the reports of a fairly large number of patients who had had Knodt rods and reported that except in the hands of a few surgeons experience with these rods generally has not been favorable.11 Interbody fusion. Interbody fusion of the lumbar spine has been used in our practice largely as a salvage p r o c e d ~ r e46. ~I~think we can say that there are 3 or 4 good reasons why anterior interbody fusion done for disk disease does not enjoy a good reputation at (1) The success rate of this time.l0> most surgeons for obtaining solid fusion is low. (2) The incidence of success in relieving pain in most series is rather low. This is not entirely the fault of the procedure but rather due to the fact that the operation is done as a salvage procedure and, after 3 or 4 unsuccessful back surgeries, any further surgery usually gives a poor clinical result. (3) There are considerably more complications with a fusion done through the anterior approach than posterior fusions done through the posterior approach. (If interbody fusion is done through the posterior

Disk Disease Surgery

39

FIG.17. If Knodt rods are used, the spinous processes and laminae of L-5 are removed. The pars are saved. Distraction rods go from the laminae of L-4 to the laminae of S-I. Fusion of the transverse processes and lateral masses is done.

approach, the complication rate is also fairly high.) (4)The incidence of retrograde ejaculation (not impotence) in a male is a definite factor. Fortunately it usually disappears in one or two years. It varies from one in 25 to one in 100 in various reports. ( 5 ) Another problem has been evaluating the subjective clinical end results. The good or excellent results have been about the same whether solid fusion was obtained or not. 5, 7, 17, 41

Sacks41 and Flynnl7 especially note this fact. This would seem a marked incongruity but we must realize that because these were done largely as salvage procedures, many other factors enter into the subjective clinical end result besides solidity of fusion. For example, compensation problems, the need to continue on disability income, emotional fac-

40

Wiltse

FIG.18. Freebody interbody fusion. A midline transperitoneal approach is made. A trap door is removed from the front of L-5. A thumb-sized graft is put in. The trap door is tamped back in place. The remaining disk spaces lateral to the graft are packed with cancellous bone.

tors or actual objective factors such as scarring around the spinal nerves in their canals, or arachnoiditis. A number of techniques for anterior lumbar spine fusion have been developed. Most are not beyond the capabilities of a good orthopedic surgeon.46 I will illustrate a few of the more prominent ones which we have used. Freebody technique. Mr. Douglas Freebody of London has developed the technique which bears his name (Fig. 18).18 The details are as follows: A midline abdominal skin incision and transperitoneal approach are made. A trap door is removed from the front of the body of L-5 as shown. Through this trap door, using a curett or a bone drill, a hole is made through the remainder of the body of L-5 and on into the body of S-1 to a depth of about 4cm. The disk tissue remaining laterally is curetted and the end plates excised with a chisel. A piece of the crest of the ilium about the size of a man’s thumb is driven into this prepared hole and the trap door tamped back in place. Cancellous bone is packed in the remaining lateral disk space. The patient is kept in a double half-shell body cast from knees to sternum for 6 weeks and then allowed up in a body jacket. We have used this technique in cases of spondylolisthesis who have very high-grade slip and who have had unsuccessful attempts

Clinical Orthopardlcr and Relatd Research

FIG.19. Raney interbody fusion. Note the block of ilium behind the fibular struts.

at posterior fusion and are unstable. The success rate by this technique is satisfactory but still in our hands is not better than 80% for a given level. R a w y technique. Raney has developed a technique for anterior interbody fusion in which he uses a retroperitoneal approach and puts in both struts of fibula and blocks of ilium (Fig. 19).37 It has the advantage that the fusion rate is good and the patient need not be kept down post operation. It has the disadvantage that bone must be removed from 2 sites. Interestingly, the fibula often unites quite readily but the blocks of ilium may remain ununited for years. Fibula alone as a grafting material (Fig 20). Fibula alone is an extremely good grafting material for the interbody area. It is very strong and the success rate is very high as regards fusion. The bodies must be spread apart severely. This can be done by elevating the kidney rest and hyperextending the patient while at the same time using a laminar spreader to spread the vertebral bodies. Segments of fibula are put in on end. I specify on end. There are several difficulties in using fibula. ( 1) Without proper instruments, getting the segments of fibula perfectly vertical is a technically difficult feat. They must not be placed lying down on their sides. If they tip over on their sides, they will not fuse. (2) One fibula will supply just about enough bone for one disk space. Fibula bone

Number November-December, 129 1977

Dirk Disease Surgery

41

FIG. 20. Fibula as grafting material for the interbody area. Note that at L-4 where the bone remained standing on end, fusion has taken place. At the L-5 level the fibular struts have tipped over and failure of arthrodesk has occurred. The extension view shows the L-5 space to have opened slightly. The incidence of solid fusion wing fibula alone has been extremely high when the grafts are properly placed.

should not be removed below the junction of the middle and distal thirds. (3) If one is trying to graft the L-5,S-1 levels and there is much lordosis, the fibular graft will be too horizontal and getting good compression is difficult. Without compression, fusion will fail. (4) Patients often complain of pain in the leg where the graft was removed. This may be due to detaching the muscle origins. Some weakness to dorsiflexion occasionally results. However none of these difficulties is insurmountable and it has been our experience that, if the fibular grafts can be well placed, the patient can be allowed up immediately and the fusion rate is extremely high. Rib grafts. Rib grafts work very well in some situations. These are cut at the approximate length and stood on end between the bodies. Rib is much weaker than fibula and for that reason in the adult is likely to crush in the lumbar area. It works very well in the occasional child who needs an interbody fusion as in cases of congenital kyphosis. The osteogenic potential of autogenous rib is extremely high. Horse-shoe shaped iliac grafts. Horseshoe shaped grafts2O (Fig. 21) cut from the

rim of the ilium as seen in this figure can be used in some circumstances. If there has been an attempt or 2 to get fusion posteriorly and some stability has been obtained, the fusion rate is reasonably high using this type of iliac graft. However, in the primary case, even if one gets the grafts wedged very tightly, they tend to crush and failure of fusion is the rule. Fusion takes place on one side of the iliac graft, usually the lower, but fails on the other. Dowel grafts. Dowel grafts have been used extensively by Harmon and by others. We have had some experience with these but have found that, unless considerable stability is already present from previous attempts at posterior fusion, pseudarthrosis is the rule. Surgical approaches for anterior interbody fusion. The direct transperitoneal approach used by Freebody probably gives the best access to the front of the vertebral bodies, but has the disadvantage of invading the peritoneum. The retroperitoneal approach of Harmon does not invade the peritoneum but some people have difficulty getting to the L-5 interspace. Wound separation and incisional herniae have also been a problem.

42

Clinical Orthopaedics and Related Research

Wiltse

FIG. 21. Horse-shoe shaped grafts of ilium can be tamped into the disk space. Rmove all cartilage from the end plates but leave strong bone on ends of vertebrae. Spread vertebrae. Wedge iliac blocks in as tightly as possible.

We have used an oblique incision which parallels the iliac crest and goes retroperitoneally. It has the advantage that wound dehiscence or incisional hernia seldom occur. Also iliac crest bone can be taken through the same incision but it can be difficult to get to the L-5 space through this approach. Lumbar interbody fusion by the posterior route.4 Cloward has described a method of interbody fusion through a posterior midline approach. In this operation the laminae are approached from posteriorly. The interspinous ligament and the margins of the adjacent spinous processes are removed to permit insertion of a special vertebral spreader. About half of the adjacent lamina1 edge is removed along with the articular facets. The cauda equina is retracted to one side. The posterior annulus is excised, along with the nucleus pulposus. The cortical surfaces of the adjacent vertebral bodies are removed to raw bleeding bone. Full thickness autogenous iliac grafts are

then driven into the space, 2 on each side, making a total of 4, completely filling the disk space. The wound is closed routinely and the patient is permitted out of bed when able. We have used this fusion on a number of occasions but have found that, when used alone, failure of fusion is the rule. We then added a posterior fusion to the procedure and found that with this combination solid fusion nearly always occurred. However, solid fusion usually occurs with one-level posterior fusions without the anterior component. We now use the Cloward interbody fusion in the very occasional case of L-4 isthmic spondylolisthesis in the adult in which the posterior element must be totally removed as part of the decompression procedure. The combination of the interbody and a one-level intertransverse process fusion will succeed in cases in which either alone will fail. Homogenous bone used in the interbody area is in our experience to be condemned. Ma and Paulson* have designed a special drill and graft inserter to perform this operation. We have had some experience with this technique. It would appear to have the same strengths and weaknesses as the Cloward technique but does make the graft insertion easier. A word of caution should be sounded. If interbody fusion through the posterior route is used above the area where the conus of the spinal cord ends, great care should be used in retracting the dura and its contents in getting the plugs in. Several cases of partial paralysis have been reported in cases where due to a low lying conus, the surgeon didn't realize he was retracting the terminal end of the spinal cord. Postoperative care. Except in the case of the Freebody operation, we permit ambulation a few days after operation. If the grafted *:Dupuy Mfg. Co.

Number 129 November-December, 1977

level is at L-4 or above, a corset does immobilize to some extent.33 The question whether the fusion is or is not solid is always troublesome. In cases of anterior interbody fusion, one must see trabeculae crossing the interspace in addition to solidity on bending films to be sure of fusion. As stated, unfortunately in the patient who has had multiple back operations and still has pain and pseudarthrosis, even a solid fusion often does not relieve the pain. The obvious answer is that there are other factors than instability or even pressure on nerves which produce back pain and sciatica. What then is the place of lumbar interbody fusion in the treatment of low back pain? We still use it occasionally in the patient who fulfills the following criteria: ( 1 ) Where instability seems to be the cause of pain. ( 2 ) When there is some reason that one cannot fuse posteriorly, i.e., old posterior infection. ( 3 ) Non-union at one level instead of 2. (4) Evidence that the levels above the area of contemplated fusion are reasonably normal. (5) Favorable psychometric studies. ( 6 ) Good general health in a patient under 55 years of age. No one should attempt an anterior interbody fusion of the lumbar spine without special retractors. There are several available. I personally use those designed by R a n e ~ . ~ ’ I would also warn that the surgeon who only occasionally does an anterior interbody fusion is likely to find that his non-union rate is unacceptably high. Anyone embarking on an anterior interbody fusion should be competent in handling the great vessels or should have a vascular surgeon make the approach for him. SUMMARY There is little doubt that surgical treatment

of lumbar spine pain is often unsatisfactory.

Disk Disease Surgery

43

It is likely that we are using a cannon when a peashooter properly aimed would do a

better job. Various injection techniques, especially injection of the disk itself would seem to be a rational approach. Scarring around the spinal nerves and dura is an unsolved problem. The search for an interposition membrane goes on. Fat grafts are being advocated, but it is too early to evaluate their efficacy. The problem of how to adequately decompress the nerves in spinal stenosis without jeopardizing spinal stability is still unsolved. Interbody fusion still carries a high failure rate as far as fusion is concerned, but what is worse, failure to relieve the pain for which it was done remains frequent. Spine pain programs concentrating upon training in exercises, training in the proper way to perform the activities of daily living and especially psychological counseling and operant conditioning probably represent the greatest single recent advance in the rehabilitation of the low back sufferer. Finally, there is an unfulfilled need for more accurate reporting of our subjective clinical results if advances are to be made in this area, where pain is the principal problem. REFERENCES 1. Ailsby, R. L., Wedge, J. H. and KirkaldyWillis, W. H.: Managing low back pain. C. M. E. News (Continuing Medical Education, University of Saskatchewan 2: 8 1, 197 1 ) 2. Brish, A., Lerner, M. B. and Braham, J . : Intermittent claudication from compression of cauda equina by a narrowed spinal canal, J. Neurosurg. 21 :207, 1964. 3. Clark, K.: Significance of small lumbar canal: Cauda equnia compression syndromes due to spondylosis. Part 2. Clinical and surgical significance, J. Neurosurg. 31:495, 1969. 4. Cloward, R. B.: The treatment of ruptured lumbar intervertebral discs by vertebral body fusion, indications, techniques and after care, J. Neurosurg, 10:154, 1952. 5. Coventry, M. B. and Stauffer, R. N.: The multiply operated back, Am. Acad. Ortho. Surg. symposium on The Spine, 1968, pp 132142.

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6. Crock, H. V.: Isolated lumbar disc resorption as a cause of nerve root canal stenosis, Clin. Orthop. 115:109, 1976. 7. De Palma, A. and Rothman, R.: The nature of pseudarthrosis, Clin. Orthop. 59: 113, 1968. 8. DiStefano, V. J., Klein, K. S., Nixon, J. E. and

Andrews, E. T.: Intraoperative analysis of the effects of position and body habitus on surgery of the low back, Clin. Orthop. 99:51, 1964. 9. Dombrowski, E. T. and Naftzger, E. (B. S . ) :

10. 11. 12.

13.

14.

15.

Cllnical Orthopaadicr and Rdatad Rasoarch

Wiltse

Progressive spinal stenosis-its differential diagnosis and treatment. Paper read at Western Orthopedic Assocation, Houston, November 1972. Domise, F. G.: Lumbosacral interbody spinal fusion, J. Bone Joint Surg. 41-B:87, 1959. Dubuc, F.: Knodt rod grafting, Orthop. Clin. North Am. 6: 1:283, 1975. Ehni, G.: Significance of the small lumbar spinal canal: Cauda equina compression syndromes due to spondylosis. Part 1. Introduction, J. Neurosurg. 3 1 :490, 1969. Epstein, J. A., Epstein, B. S. and Lavine, L.: Nerve root compression associated with narrowing of the lumbar spinal canal, J. Neurol. Neurosurg. Psychiat. 24: 165, 1962. Farfan,H. F.: Mechanical disorders of the low back, Philadelphia, Lea & Febiger 1973, p. 150. Feffer, H. L.: Therapeutic intradiscal hydrocortisone, a long term study, Clin. Orthop.

67:100, 1969. 16. Fitzgerald, J. and Newman, P.: Degenerative

spondylolisthesis, J. Bone Joint Surg. 58-B:

22. Harmon, P. H.: Anterior extra peritoneal

lumbar disc excision and vertebral body fusion, Clin. Orthop. 18: 169, 1960. 23. Hartman, J.T., Winnie, A., Ramaurthy, S., Mani, M. R. and Meyers, H. L., Jr.: Intra: dural and extradural corticosteroids for sciatic pain, Orthop. Rev. 111:12:21, 1974. 24. Hastkgs, D. E.: A simple frame for operations on the lumbar spine, Can. J. Surg. 12: 251, 1969. 25. Hirsch, C.:

Etiology and pathogenesis of back pain, Isr. J. Med. Sci. 2:362, 370, 1966. 26. Kirkaldy-Willis, W. H.: Lumbar spinal stenosis and nerve root entrapment syndromesdefinition and classification, Clin. Orthop. 115:4, 1976 27. Knodt, H. and Larrick, R. B.: Distraction fusion of the spine, Ohio State Med. J. 60: 12: 1140, 1964. 28. Langenskiold, A. and Kiviluoto, 0.:Fat

free transplants in the prevention of epidural scar formation after lumbar disk surgery, a preliminary report, Clin. Orthop. 115: 92, 1976. 29. Macnab,

I: Backache. Published by The Workmen’s Compensation Board, Ontario, 1973, p. 175. 30. McElroy, K. D.: Lumbosacral fusion by bilateral- lateral technique. Proc. Am. Acad. Orthop. Surg, J. Bone Joint Surg. 43-A:918, 1961. 31. Mooney, V. and Robertson, J.: The facet syndrome, Cinl. Orthop. 115: 149, 1946. 32. Moms, J. M., Lucas, D. B. and Bresler, B.:

2:184, 1976. 17. Flynn, J. C.; Anterior fusion of the lumbar

spine; long term follow-up end result study. Paper read at meeting of Am. Acad. Orthop. Surg., Las Vegas, Nevada, Feb. 6, 1977. 18. Freebody, D. : Treatment of spondylolisthesis by anterior fusion via the transperitoneal route, J. Bone Joint Surg. 47B:788, 1964. 19. French, J. D.: Clinical manifestation of lumbar spinal arachnoiditis: a report of 13 cases, Surgery, 20:718, 1946. 20. Goldner, L. H. and McCullom, D. E.: Anterior lumbar spinal arthrodesis and intervertebral disk removal for treatment of chronic low back pain with and without radiculitis. Paper read at the annual meeting of the Amer. Orthop. Assn, Hot Springs, Va., June, 1967. 21. Jones, R. A.

C. and Thompson, J. L. G.: The narrow lumbar canal, J. Bone Joint Surg. 50-B:595, 1968.

33. 34. 35. 36.

Role of the trunk in instability of the spine, J. Bone Joint Surg. 43-A:327, 1961. *. Biomechanics of the spine, Arch. Surg. 107:418, 1973. Nachemson, A.: The Lumbar spine, an orthopedic challenge, Spine 1 :1 :59, 1976. Nelson, M. A.: Lumbar spinal stenosis, J. Bone Joint Surg. 55-B:506, 1973. Pheasant, H. C.: Sources of failures in laminectomies, Orthop. Clin. North Am. 6:319,

1975. 37. Raney, F. and Adams, J.: Anterior lumbar

intervertebral disk excision and interbody fusion as a salvage procedure. Paper presented at the meeting of the Western Orthopedic Assn, San Francisco, Ca. Oct. 29, 1962. 38. Rosenberg, N. J.: Degenerative spondylolisthesis: predisposing factors, J. Bone Joint Surg. 57-A:467, 1975. 39. -Degenerative spondylolisthesis, surgical treatment, Clin. Orthop. 117:112, 1976.

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40. Roslund, J.: Indications for lumbar disk surgery. Monograph, Stockholm, 1974. 41. Sacks, S.: Symposium on the spine, Orthop. Clin. North Am. 6: 1:275, 1975. 42. Sarpyener, M. A.: Spina bifida aperta and

congenital stricture of the spinal canal, J. Bone Joint Surg. 29:817, 1947. 43. Smith, L.: Enzyme dissolution of nucleus puiposis in humans, JAMA, 197:137, 1964. 44. Tile, M.: Personal communication, May, 1975. 45. Wiltse, L. L. Bateman, J. G.. Hutchinson. R.

H., and Nelson. W.: The paraspinal sacrospinalis-splittine approach 10the luinbnr spine, J. Bone loint S r q . S O - A . 5:919. 1968. : Interbody fusion of the lumbar spine. 46. Jr. Western, Pac. Orthop. Assn., V1:I , 1969. : The paraspinal sacrospinalis-splitting 47. approach to the lumbar spine, Clin. Orthop. 91:48, 1973.

48.

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-: Laminectomy and spinal fusion, Part

1:Sound slide program presented at the meeting of the American Academy Orthopaedic Surgeons, Sunday, March 2, 1975, San Francisco, Ca. 49, , Widell, E. H. Jr., Yuan, H. A.: Chymopapain chemonucleolysis in lumbar disc disease, JAMA 231: 5:474, 1975. 50. , Rocchio, P.: Preoperative psychological tests as predictors of success of chemonucleolysis in the treatment of the low back syndrome, J. Bone Joint Surg. 57-A, 4:478,

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1975.

-, Kirkaldy-Willis

W. H. and Mclvor, G. W.,: Treatment of spinal stenosis, Clin. Orthop. 115:83, 1976. 52. : Spondylolisthesis, Etiology and Classification. Sound slide program presented at the meeting of the American Academy Orthopaedic Surgeons, Sunday Feb. 3, 1976, New Orleans La.

51.