44 Microsurgical Decompression of Acquired
(Degenerative) Central and Lateral Spinal Canal Stenosis
H.M. Mayer
44.1
Terminology
Microsurgical decompression of the spinal canal is de- fined as a mono- or multisegmental, uni- or bilateral internal enlargement of the central and/or lateral vol- ume of the spinal canal without performing a laminec- tomy. “Internal laminoplasty” is proposed as a synony- mous term.
44.2
Surgical Principle
The spinal canal is approached through a modified mi- crosurgical interlaminar route (see Chapter 32) usually from the (most) symptomatic side. In cases with asso- ciated degenerative lumbar scoliosis, the approach from the convex side is preferred.
The interlaminar window is opened ipsilaterally by resection of the hypertrophied yellow ligament.
The insertions of the yellow ligament are resected by osteoclastic undercutting of the cranial and caudal lamina.
Subarticular ipsilateral decompression is achieved by undercutting or partial resection of the medial parts of the superior facet of the infradjacent verte- bra.
Enlargement of the central parts of the spinal canal is achieved by dome-shaped undercutting of the laminae and resection of the ventral parts of the interspinous ligament.
Contralateral decompression is performed through an “over-the-top” approach.
44.3 History
Wide laminectomies still are considered to be the treat- ment of choice in degenerative spinal stenosis without instability [4 – 7, 13, 14, 15]. Due to the risk of destabili- zation of the motion segment, a limited approach was
proposed by Poletti in 1995 [12]. The microsurgical in- terlaminar approach for the treatment of lumbar disc herniations has been adopted and modified. An exten- sion of the ipsilateral approach to the contralateral side has been proposed in order to decompress the lateral recess bringing in the working instruments “over-the- top” of the thecal sac to the contralateral side. The ap- proach was refined by McCulloch and described first in detail in 1998 [10].
44.4 Advantages
The advantages include all advantages described in the chapters on microdiscectomy (Chapters 31, 32, 34).
There are other advantages which can be divided into technical and clinical categories. The typical technical advantages are:
Decreased trauma to paravertebral muscles on the ipsilateral side, no trauma to paravertebral muscles on contralateral side.
Bilateral decompression of the spinal canal through a unilateral approach.
Microsurgical internal enlargement of the spinal canal preserves completely the posterior tension banding system (supraspinous, interspinous liga- ments, spinous processes as well as paraspinal muscles on the contralateral side.
Complete preservation of the laminae as well as of the lateral two thirds of the facet joint on the ipsi- lateral side.
Preservation of the outer contour and more than 75 % of the facet joint of the contralateral side (see also Fig. 44.14).
Complete decompression of the thecal sac as well as of the spinal nerves on both sides from their du- ral sleeve exits to their entrance into the foramen.
The clinical advantages result from the technical advantages:
Decreased trauma to paravertebral muscles results
in early mobilization, negligible postoperative
wound pain, and an early start to rehabilitation.
Decreased blood loss even in multisegmental approaches.
Since the average age of the patients is > 70 years (see also Section 44.12) early mobilization is an important factor to decrease postoperative compli- cations such as deep venous thrombosis, urinary tract infection, or pneumonia due to prolonged immobilization.
The risk of increasing instability is very low even in those patients who already show signs of mild (grade I) degenerative spondylolisthesis (personal observations). This is the reason why this kind of decompressive procedure can be performed with- out stabilization even in these patients.
44.5
Disadvantages
There are several mainly technical disadvantages asso- ciated with this approach:
The time for monosegmental decompression is slightly longer as compared to open central lami- nectomy. However, multilevel decompression occa- sionally results in considerably longer operating times.
Decompression of the contralateral side is a techni- cally demanding procedure. Insufficient exposure can lead to enforced intraoperative manipulation of the thecal sac and cauda equina which can result in temporary and/or permanent neurological defi- cits.
Inadequate decompression especially of the contra- lateral side can lead to unfavorable clinical out- comes.
44.6 Indications
The procedure is indicated in all patients showing the clinical symptoms of acquired degenerative lumbar spinal stenosis without or with insignificant and mild vertebral body translations.
The following clinical signs and symptoms should be present:
Uni- or bilateral symptoms in the legs. In contrast to clear radicular symptoms, for example in disc herniations, the patients complain about weakness or heaviness in the lower extremities particularly when walking. Mild sensory deficits or paresthe- sias can be present as well. The symptoms usually get better when the patient stops walking, as well as in inclination. On physical examination, the
symptoms can rarely be verified unless there is a long history of complaints. However, there may be patients in whom mono- or oligoradicular symp- toms due to lateral canal stenosis dominate the clinical picture.
Diminished walking distance (“spinal claudication”).
Reduced standing time.
Low back pain.
Loss of segmental motion (stiffness of the low back).
Loss of lumbar lordosis.
Radiological investigations such as plain X-ray, MRI, (functional) myelography or myelo-CT should prove a narrowing of the central and/or lat- eral spinal canal in relation to the topography of the lumbar nerve roots (Fig. 44.1). Older classifica- tion systems which refer to measurement of the sagittal and/or transverse diameter of the spinal canal are not helpful for the indication for surgery since it is not the absolute width of the spinal canal
Fig. 44.1. MRI sagittal view. Multilevel spinal stenosis
which determines compromise of neural struc- tures. The relation between the size and topogra- phy of neural structures and the space available is the only reliable measure which determines the clinical symptoms.
Electrophysiological parameters such as electro- myograms (EMG), nerve conduction studies, or so- matosensory-evoked potentials (SSE) contribute mainly to rule out other diagnosis such as periph- eral neuropathies.
Decompression without stabilization is performed in all patients without radiological signs of verte- bral body translation, in patients without low back pain despite vertebral body translation or degener- ative scoliosis, in patients older than 75 years, and in patients with severe osteoporosis and multiseg- mental pathology.
Decompression with segmental stabilization (usu- ally posterior–anterior 270° fusion or TLIF) is per- formed in patients exhibiting grade I or higher- type spondylolisthesis on rest or functional X-rays with significant low back pain as well as in patients with unstable lumbar degenerative scoliosis.
44.7
Contraindications
There are no disease-specific contraindications for de- compression of the spinal canal. Modern anesthetic techniques and monitoring equipment make it possible to perform general anesthesia even on old patients with a low risk. However, there may be a few absolute contra- indications for general anesthesia such as:
Severe respiratory insufficiency Unstable angina pectoris Severe arterial hypertension
44.8
Patient’s Informed Consent
The patients should be informed about the risks which are immanent of microsurgical mono- or multilevel ap- proaches to the lumbar spinal canal:
Nerve root, cauda equina, and/or conus medullaris lesions with postoperative neurological deficits including bladder and bowel dysfunction Dural tears with menigocele and/or CSF fistulas Postoperative epidural hematoma
Meningitis
Spondylodiscitis with epidural abscess Epidural scarring with neurological deficits or permanent sciatica
Segmental instability chronic low back pain and radicular symptoms (“Failed Back Surgery” syn- drome) requiring stabilizing surgical procedures
44.9
Surgical Technique
The surgical technique can be divided into microsurgi- cal decompression without and with segmental stabili- zation. The indications are described above.
44.9.1
Microsurgical Decompression without Instrumented Fusion
44.9.1.1
Preoperative Planning
Technical preoperative planning is performed using the information given by plain X-rays of the lumbar spine, MRI, and/or CT scan/post-myelographic CT scan.
44.9.1.1.1 Plain X-rays
All patients require plain X-rays of the lumbar spine.
We routinely perform AP and lateral views. If instabili- ty with vertebral body translation is suspected, func- tional X-rays in flexion and extension are performed as well. The X-rays give the gross picture of the curvature of the lumbar spine. They reveal degenerative scoliosis and segmental rotational or translational instability.
For surgical planning, it is important to know the size and shape of the interlaminar window since this is the entrance into the spinal canal. In most of the cases, the interlaminar space is small, sometimes completely closed (Fig. 44.2). The width of the laminae cephalad and caudad to the interlaminar space represents the safety range for bony decompression without perform- ing a hemilaminectomy. The width of the isthmic area can be judged in order to preserve it intraoperatively.
44.9.1.1.2
Magnetic Resonance Imaging, CT Scan, and Post-myelographic CT Scan
These are the surgeon’s most important preoperative
sources of information. MRI is, in my opinion, the im-
aging technique of choice, as in most of the patients this
investigation gives sufficient information. The size and
contour of the facet joints are clearly visible. This facili-
tates intraoperative orientation. It is important to know
how much if the medial part of the inferior facet of the
cephalic vertebra can be removed without sacrificing
Fig. 44.2. AP X-ray of a lumbar spine showing extremely nar- row interlaminar spaces
more than one third of its size. The thickness of the yel- low ligament, its extension underneath the adjacent laminae as well as the thickness of the lamina itself can be evaluated. The extension of the yellow ligament as well as the thickness of the flavum determine the amount of undercutting which is necessary for suffi- cient decompression (Fig. 44.3). The size and topogra- phy of the neural structures at the level of compression as well as above and below should be evaluated careful- ly to avoid damage during decompression. The distri- bution of epidural fat tissue can lead to a modified sur- gical strategy which helps to protect the neural struc- tures: for example, in an extremely narrow canal it is more advisable to enter the spinal canal through a more medial posterior route where more epidural fat pro- tects the thecal sac (Fig. 44.4). Note the shape of the spi- nal canal (round, oval, trefoil; Fig. 44.5), and estimate whether it is mainly soft tissue (yellow ligament, joint capsule, intervertebral disc) or bone (superior facet, lamina, osteophytes) which leads to a compression of neural structures. If, as in the majority of acquired spi-
Fig. 44.3. MRI axial view. Hypertrophied yellow ligament con- tributing to central and lateral spinal stenosis
Fig. 44.4. MRI axial view L5/S1. Epidural fat is preserved in the dorsal parts of the spinal canal
nal stenoses, it is mainly soft tissue compression, try to preserve the bony structures as much as possible.
44.9.1.2
Anesthesiological Aspects
The operation is performed under general anesthesia.
Patients with spinal stenosis carry, due to their age and
other concomitant diseases, higher risks and require
reliable intraoperative monitoring. We recommend the
introduction of a central venous line, to perform arteri-
al blood pressure monitoring, as well as the introduc-
Fig. 44.5. Schematic drawing of the different shapes of the spinal canal
tion of a urinary catheter irrespective of the expected time for the operation. Blood transfusions are not rou- tinely necessary, and own blood donations are not re- quired. However, if more than a two-level decompres- sion is intended, we recommend intraoperative blood collection for retransfusion.
44.9.1.3 Positioning
The patient is placed in a prone “Mecca” position as de- scribed in Chapter 32 (Fig. 44.6). The principles of po- sitioning for lumbar microdiscectomy are valid. How- ever, there are some special aspects which have to be considered in patients with acquired spinal stenosis:
It is important to rule out hip joint contractures (not rare in this group of patients). Watch the hip joint and avoid luxation in patients with artificial hip joints!
Watch the knees of the patient! Patients often have gonarthrosis or total joint replacement in the knee as well. Since decompression sometimes lasts more
Fig. 44.6. Positioning of the patient
than 2 hours take care to pad the knees with a gel cushion to avoid pressure sores.
Pay attention to the cervical spine! Mobility of the cervical spine is decreased in these patients. Rota- tion of the head is restricted. Put a soft pad under the forehead of the patient in order to avoid head rotation.
Pay attention to the shoulders! Patients can have limited mobility of the shoulder joint. This requires modification of positioning of the upper extremi- ties.
Use as many gel cushions or pads as are needed to protect the neural and surface structures at risk (ulnar nerve, brachial plexus, peroneal nerve, knee, eyes, nose).
44.9.1.4 Localization
The level(s) which have to be approached for microsur-
gical decompression are localized according to the
principles described in Chapter 32. The skin incision is
centered exactly over the lumbar segment of interest. If
two or more levels have to be exposed for decompres- sion, the skin incision is enlarged. If two non-adjacent levels have to be approached (e.g., L2/3 and L4/5), two separate approaches with separate skin incisions are recommended.
Avoid movements of the patient (table) in the sagit- tal or transverse plane after localization is performed and the skin incision is marked as this may lead to the wrong level. As soon as the right level is approached, the table can be tilted.
44.9.1.5
Skin to Interlaminar Space
The operation is started with the microscope from the skin level. The interlaminar space is approached using the same technique as described in Chapters 31 and 32.
The fascia is opened in a semicircular manner leaving the medial parts attached to the supraspinous ligament and the lamina. The paravertebral muscles are retracted after subperiosteal elevation. Retraction does not ex- tend beyond the lateral border of the facet joint in order to avoid disruption of segmental innervation. The lami- nae of the adjacent vertebrae are exposed and the inter- laminar window is cleaned of soft tissue (Fig. 44.7).
Usually the window is very small and the yellow liga- ment is bulging. The speculum-retractor is then insert- ed. Make sure that the inferior (ventral) part of the in- terspinous ligament is exposed as well and that the vi- sual axis toward the midline is not obstructed by a hy- pertrophied or dysplastic spinous process.
44.9.1.6
Microsurgical Ipsilateral Decompression
Decompression is started with the removal of the infe- rior parts of the cephalic lamina. This is performed step by step using a high-speed burr. I recommend to start
Fig. 44.7. Interlaminar window exposed. y.l. Yellow ligament
this microsurgical “laminotomy” at the transition zone between the lateral aspects of the lamina and the spi- nous process. The reason is that even in severe spinal stenosis you always find remnants of epidural fat un- derneath the posterior yellow ligament. Resection of the inferior parts of the lamina is extended until the in- sertion of the yellow ligament “fades out” and the dura or epidural fat can be identified. Laminotomy is ex- tended laterally and caudally. Depending on the size of the inferior facet, its medial aspect is removed until the medial parts of the superior facet can be identified.
Note that the spinal canal is not yet opened except for its cranial and medial part.
Exposure of the yellow ligament is completed by re- section of the superior part of the caudad lamina. It is now that the yellow ligament can be easily removed with rongeurs including the ventral parts of the inter- spinous ligament. Thus the “back” of the thecal sac is exposed. Adhesions of the dura to the yellow ligament can now be gently dissected from medial to lateral. Af- ter removal of the yellow ligament and its insertion un- derneath the lamina in most of the cases the central portion of the spinal canal is already decompressed.
However, if there is still narrowing by a hypertrophied lamina, undercutting has to be continued in cranial and caudal directions.
The surgeon now looks onto the back of the thecal sac and the roof of the lateral recess which is formed by the medial aspects of the superior facet and the remains of the yellow ligament and joint capsule (Fig. 44.8).
“Subarticular” decompression can be the most difficult part of the operation. Usually there is no space between the lateral parts of the thecal sac, the nerve root, and the superior facet. With a blunt microdissector, the neural structures are gently mobilized from the yellow ligament. With a 1.5- or 2-mm Kerrison rongeur, the lateral recess is opened stepwise. I recommend to start in the middle portion and to proceed first in a caudal
Fig. 44.8. Part of the dura (d) is exposed. Narrow lateral recess ipsilateral
Fig. 44.9. Direction of Kerrison rongeur for decompression of the ipsilateral recess. d Dura, r rongeur, l lamina of supradja- cent vertebra
direction. This means that the “shoe” of the rongeur is always introduced parallel to the route of the nerve. It thus can slide over the nerve and the risk of dural lacer- ation or nerve injury is minimized (Fig. 44.9). Thus first the posterior aspect and then the lateral border of the nerve are exposed. At this stage, the caudal part of the lateral recess is already decompressed. However, there is still compression at the “shoulder” of the spinal nerve as well as at the entrance into the foramen.
First, decompression is extended along the nerve un- til the medial border of the pedicle can be visualized (Fig. 44.10). In rare cases, the medial border of the pedi- cle leads to a kinking or compression of the nerve root.
It is difficult to drill and smooth the medial parts of the pedicle since the high-speed burr has to be introduced into the narrow space between the nerve and the pedicle border. In these cases, the pedicle can be opened with the high-speed burr and the medial half is “eggshelled”
and then broken off with a rongeur (Fig. 44.11). Decom- pression of the “shoulder” of the nerve root is now com- pleted by removal of the yellow ligament in the superior
Fig. 44.10. Decompression in caudal direction down to the en- trance of the foramen. r Rongeur, d dura, inf. l. lamina of in- fradjacent vertebra
Fig. 44.11. Resection of the medial half of the pedicle
Fig. 44.12. Complete ipsilateral decompression (intraoperative view). n Nerve root
lateral corner of the surgical field. Decompression in this area must be performed until the inferior border of the exiting nerve root can be identified or palpated with the blunt nerve hook (Fig. 44.12). In cases with pronounced narrowing of the intervertebral space there is often impingement of the exiting nerve root by the tip of the superior facet. This tip can now be re- moved with a rongeur thus achieving a complete de- compression of the exiting nerve root in the foramen.
44.9.1.7
Microsurgical Contralateral Decompression
The table is now tilted away from the surgeon and the microscope is adjusted to give an oblique view into the spinal canal (Fig. 44.13a, b). The next step is the resec- tion of the ventral parts of the interspinous ligament and its transition zone into the fibers of the contralater- al yellow ligament. The rongeur can now be introduced underneath the yellow ligament of the contralateral side. The ligament is resected to create more space pos- terior as well as posterolateral on the contralateral side.
It is occasionally necessary to resect ventral parts of the
base of the spinous process. It is always necessary to
continue undercutting of the supra- and infradjacent
lamina to increase the spinal canal volume as well as to
have a free visual axis toward the contralateral recess
and foramen entrance. Decompression is facilitated if
the surgeon first follows the inner surface of the infrad-
jacent lamina to identify the medial border of the con-
a b
Fig. 44.13. a Oblique view into the contralateral spinal canal (schematic drawing). b Oblique view into contralateral com- partment of the spinal canal (intraoperative view). d Dura mater, di.
blunt dissector, i.l. inter- spinous ligament
a b
Fig. 44.14. a Decompres- sion contralateral (schematic drawing).
b Decompression of the contralateral compart- ment (intraoperative view). n Contralateral spinal nerve, t thecal sac, d blunt dissector in con- tralateral recess
tralateral inferior pedicle. This can be achieved with minimum retraction of the thecal sac. Then decom- pression by subarticular undercutting as well as by un- dercutting of the supradjacent lamina can be accom- plished (Fig. 44.14a, b). Although it will be occasionally necessary to use a blunt dissector or a nerve hook to temporarily retract the dura, it is possible to achieve this in most of the cases simply by using the metal suck- er probe.
44.9.1.8 Closure
At the end of the procedure there should be dural pul- sations and four free nerves (two traversing and two exiting nerves). The bone surface is sealed with small amounts of bone wax if significant oozing of blood is visible. Hemostatic agents such as FloSeal (Baxter Healthcare, Fremont, CA, USA) or Arista (Medafor, Bad Wiessee, Germany) can be used.
If possible, the insertion of a drain is avoided. We recommend not to place any foreign material (e.g., Gel- foam, Surgicel, etc.) into the spinal canal. If there is a significant amount of epidural fat tissue left, the spinal nerves can be covered after gentle mobilization of the fat. The surgical field is irrigated with saline solution, and the fascia and the skin are closed with resorbable sutures.
44.9.2
Microsurgical Decompression with Instrumented Fusion 44.9.2.1
Posterior Approach
The surgical technique of posterior–anterior instru- mented fusion in patients with spinal stenosis and ver- tebral body translation is described in detail elsewhere [9]. The anterior part of the operation is described in Chapters 45 and 46. We prefer, for biomechanical rea- sons, the combination of posterior instrumented fu- sion with a pedicle screw system in combination with anterior interbody fusion or a TLIF using a microsurgi- cal approach. Since the posterior approach is not a
“minimally invasive” approach, it will not be described in detail in this chapter.
44.9.2.2
Preoperative Planning
Preoperative planning includes the acquisition of CT scan data for intraoperative navigation. The pedicle screws are inserted with the help of a spinal navigation system (Stealth system; Sofamor Danek) [2, 3, 8, 11]
(Fig. 44.15). If no navigation system is used, measure-
ment of the pedicle diameter, as well as of the sagittal
length of the vertebral body is performed manually and
the size and length of the pedicle screws is determined.
Fig. 44.15. Stealth system
MRI as well as CT scans give an impression about the angles of the pedicles as well as the localization of the retroperitoneal vessels in relation to the bony struc- tures.
44.9.2.3
Anesthesiological Aspects
The operation is performed under general anesthesia.
Patients with spinal stenosis carry, due to their age and other concomitant diseases, higher risks and require reliable intraoperative monitoring. We recommend the introduction of a central venous line, to perform arteri- al blood pressure monitoring, as well as the introduc- tion of a urinary catheter irrespective of the expected time for the operation. Blood transfusion are not usual- ly necessary.
44.9.2.4 Positioning
The patient is placed in a prone, comfortable position on a soft foam frame on a radiolucent table. The gener- al principles of protection of neural structures and the skin are respected. The hips and knees are slightly (20 – 30°) flexed, and the anterior iliac crest is padded in order to avoid pressure on the lateral femoral cutane- ous nerve.
44.9.2.5 Localization
Localization of the level(s) to be approached follows the criteria described above. If the pedicle screws are inserted without the help of an intraoperative naviga- tion system, the level of the pedicle entrances are marked as they project onto the skin surface in AP fluo- roscopic control. Lateral fluoroscopy is added to gain an impression of the inclination in the sagittal plane of the vertebrae to be instrumented.
44.9.2.6
Skin to Interlaminar Space
The operation is started without the microscope. The interlaminar space, the facet joints of the segment to be decompressed and fused, as well as the facet joint above are exposed bilaterally using a conventional technique [1].
Even in cases which afford segmental instrumented fusion, we try to avoid retraction of the muscles beyond the lateral border of the facet joint. Since we do not per- form intertransverse fusion, the transverse process does not need to be exposed. However, it must be pal- pated as well as the transition zone between the trans- verse process and the superior facet.
The operation is continued with the following steps:
1. Insertion of pedicle screws (Click’X, Synthes).
2. Opening of the facet joint capsule and mobilization of the facet joint.
3. Insertion of the mono- (Click’X, Synthes) or multisegmental (USS II, Synthes) internal fixation system (Fig. 44.16).
4. Reduction and reconstruction of normal curva- ture.
5. Microsurgical decompression (see above). Removal of cartilage from the rest of the facet joints. Inter- facet bone grafting using the removed parts of the laminae.
44.9.2.7 Closure
In these patients, two wound drains are inserted under- neath the fascia without applying suction. The wound is then closed as described above.
44.9.3
Anterior Interbody Fusion
The anterior microsurgical approach for interbody fu-
sion is described in detail in Chapters 44 and 45. Usual-
ly the operation is performed in the same session, how-
ever, it can be also be performed in a second session af-
ter an interval of 7 – 14 days.
a b
Fig. 44.16. Pedicle screw sys- tems. a Click’x Pedicle screw system. b USS II Pedicle Screw System, Synthes Ober- dorf Switzerland
44.10
Postoperative Care
The patients are allowed to mobilize within 6 hours in cases without instrumented fusion. Otherwise, the patients get out of bed the day after the operation. In patients with more than two-level decompression, as well as in patients with instrumented fusion, a short Boston brace is recommended for 4 – 6 weeks postop- eratively.
44.11
Complications
Dural tears leading to a pseudomeningocele or even CSF fistulas are the most common complica- tions during decompressive procedures in spinal stenosis. They are described to be as high as 13 % [18]. In the group of patients described above, we had 2/57 (3.5 %) dural tears which had to be su- tured. There are several reasons for the high rates of dural injuries. The dura usually is very thin in this old patient population. If the patient is placed correctly (see Section 44.9), the spinal CSF pressure is low so that the dura does not behave like a taut, well-rounded structure. Introduction of the ron- geurs can lead to infolding of parts of the dura.
This increases the risk of dural laceration.
The cauda equina is at risk especially in patients with spinal stenosis. The nerve roots are compro- mised usually for years, and the arterial supply may be diminished by other concomitant diseases (e.g., diabetic microangiopathy, microangiopathy due to arterial hypertension). This makes the fibers of the cauda equina more vulnerable as compared to the young patient. Moreover, the surgical tech- nique includes the risk of temporary direct com- pression of the cauda equina roots during decom-
pression of the contralateral side (see Section 44.9).
We had one patient with a postoperative transient hemicauda syndrome (1/57 = 1.75 %).
Epidural hematoma.
Special attention has to be made to complications secondary to positioning. The risk for such compli- cations is higher as compared to microsurgical discectomy, since microsurgical decompression requires longer operating times and thus the pa- tient has to remain in the intraoperative position for a longer time which increases the risk of pres- sure injury to the structures mentioned above.
Care must be taken to avoid pressure on the eyes since this might lead to postoperative blindness or corneal lesions.
Delayed complications:
Segmental instability
Destabilization of the adjacent segment Arachnoiditis
Epidural scar formation
44.12 Results
Comparative analysis of the results of microsurgical segmental decompression with conventional laminec- tomy techniques is difficult because we could not find any prospective, comparative studies in the literature.
McCulloch has reported recently about a good and ex- cellent outcome in 90.9 % of 22 patients with acquired degenerative spinal stenosis. In these cases, microsur- gical decompression was combined with a minimally invasive modification of intertransverse fusion [10].
Pseudoarthrosis rate was 13.6 %, and complications
ranged from 4.5 % (urinary tract infection) to 9.1 %
(deep venous thrombosis, upper respiratory tract in-
fection, superficial wound infection).
Between March 1998 and April 2002 we have treated a total of 702 patients with the techniques described above. The consecutive series of the first 275 patients (men 52 %, women 48 %) is presented here. The average age was 69 years (range 34 – 89 years). The average his- tory of complaints was > 2 years. All patients had had several unsuccessful trials of conservative therapy. Two hundred patients (73 %) complained of sciatica with in- creasing pain during walking and standing as well as heaviness and/or sensory disturbances in the leg after different walking distances/standing times. In all cases, the leg symptoms were predominant. Only 75 patients (27.3 %) complained about sciatica alone. Neurogenic claudication was evident in 252 patients (91.6 %). A rel- atively high percentage of patients presented with neu- rological deficits (125/275 = 45.5 %). The average pre- operative walking distance was 250 m. Pain-free stand- ing time was 10 min on average.
In 99 % of cases, surgery was elective, however, due to neurological deficits in 52 % of the patients, it was performed usually within 1 – 2 weeks of first presenta- tion in our hospital.
In 1 % of the patients there was a chronic cauda equi- na syndrome with bladder and bowel dysfunction. A total of 568 segments (in 275 patients) were decompres- sed (2.1 segments/patient).
The mean operating time was 37 min/segment, blood loss averaged 57 cc/segment, and all patients were mobilized within 24 hours.
After a mean follow-up of 24 months, the average pain-free standing time was 82 min (as compared to 10 min preoperative). Pain-free walking distance was increased from 250 m preoperative to 5,017 m postop- erative. In 45 % of the patients there was also a signifi- cant decrease of low back pain.
Overall complication rate was 15.6 %, with 5 % intra- operative dural leaks. In 3.8 % of patients postoperative epidural hematomas needed early revision. Together with persistent symptoms (2 %) they presented the most frequent postoperative complications.
Microsurgical decompression with instrumented posterior–anterior fusion was performed in 18 pa- tients. The age range in this group was between 43 and 76 years, averaging 62 years. Indication for fusion was the association of spinal stenosis with degenerative spondylolisthesis grade I or more in all cases. In 86 % of the patients, surgery was elective. Only 14 % presented with progressive or severe neurological deficits. There were no emergency cases.
The mean operating time for decompression as 70 min/level for microsurgical bilateral decompression and 140 min/level for decompression and posterior in- strumentation with pedicle screws. The average blood loss for decompression was 240 ml and for decompres- sion and instrumentation 760 ml. We observed a total of 4/57 (7 %) complications. There were two patients
with dural tears (3.5 %), one patient with a hemi-cauda equina syndrome (1.7 %), and one patient with a super- ficial wound infection (1.7 %). The cauda equina symp- toms resolved within 2 weeks, and the wound infection healed without intervention.
Hospitalization was between 5 and 10 days in pa- tients with just microsurgical decompression and be- tween 12 and 14 days in patients with additional instru- mented fusion. Preliminary results with a follow up time of between 3 and 12 months showed a significant improvement in leg symptoms in 90 % of patients, and a significant improvement in low back pain in 80 % of the fused patients. The walking distance was signifi- cantly improved in 70 % of the patients. In one third of our patients, there was partial or complete regression of neurological deficits.
44.13
Critical Evaluation
The goal of surgery in degenerative spinal stenosis is the improvement of leg and low back symptoms, to in- crease the pain-free walking distance, and to improve the quality of life in a group of old-aged patients. No pa- tient will be completely free of complaints and no pa- tient will have a new lumbar spine after the operation.
Extensive surgery is associated with increased risks in old patients with various associated diseases. There- fore, in this population in particular, the principle of
“maximum effect with minimum trauma” should be applied. Our experience with microsurgical decom- pression, although limited, strongly supports our ef- forts to further miniaturize the surgical approaches to the spinal canal. Postoperative mobilization as well as rehabilitation is facilitated since peri- and postopera- tive morbidity is decreased. The patients virtually have no or only slight wound pain. They experience a very quick improvement of their leading symptoms, such as increase of walking distance. Low back pain is not a sig- nificant problem even in those cases in which instru- mented fusion is performed. Microsurgical anterior approaches even allow for “circumferential” fusion which is associated with low pseudarthrosis rates [9].
We believe, that in acquired degenerative spinal ste- nosis there is no need to perform wide laminectomies.
This may not be true for congenital central spinal ste-
nosis. This disease requires a more extensive decom-
pression which often ends with a conventional multi-
segmental laminectomy. The reason for this is that nar-
rowing of the spinal canal not only affects the interlam-
inar interval but also the sublaminar space in multiple
segments. Efficient decompression thus requires lami-
nectomy, a technique which is not microsurgical and
therefore not dealt with in this book.
References
1. Bauer R, Kerschbaumer F, Poisel S (eds) (1991) Orthopädi- sche Operationslehre: Wirbelsäule. Thieme, Stuttgart 2. Berlemann U, Langlotz F, Langlotz U, Nolte LP (1997) Com-
puterassistierte Orthopädische Chirurgie (CAOS). Ortho- päde 26:463 – 469
3. Berlemann U, Monin D, Arm E, Nolte LP, Ozdoba C (1997) Planning and insertion of pedicle screws with computer as- sistance. J Spinal Disord 10:117 – 124
4. Herkowitz HN, Garfin SR (1989) Decompressive surgery for spinal stenosis. Semin Spine Surg 1:63 – 167
5. Herkowitz HN, Kurz LT (1991) Degenerative lumbar spon- dylolisthesis with spinal stenosis. A prospective study com- paring decompression and intertransverse process arthrod- esis. J Bone Joint Surg Am 73:802 – 808
6. Herno A, Airaksinen O, Saari T (1993) Long-term results of surgical treatment of lumbar spinal stenosis. Spine 18:1471 – 1474
7. Herron ID, Mangelsdorf C (1991) Lumbar spinal stenosis:
results of surgical treatment. J Spinal Disord 4:26 – 33 8. Laine T, Schlenzka D, Mäkitalo K, Tallroth K, Nolte LP, Visa-
rius H (1997) Improved accuracy of pedicle screw insertion with computer-assisted surgery. Spine 22:1254 – 1258 9. Mayer HM (1998) Microsurgical anterior approaches for
anterior interbody fusion of the lumbar spine. In: McCul-
loch JA, Young PH (eds) Essentials of spinal microsurgery.
Lippincott-Raven, Philadelphia, pp 633 – 649
10. McCulloch JA (1998) Microsurgery for lumbar spinal canal stenosis. In: McCulloch JA, Young PH (eds) Essentials of spinal microsurgery. Lippincott-Raven, Philadelphia, pp 453 – 486
11. Nolte LP, Visarius H, Arm E, Langlotz F, Schwarzenbach O, Zamorano L (1995) Computer-aided fixation of spinal im- plants. J Image Guided Surg 1:88 – 93
12. Poletti CE (1995) Central lumbar stenosis caused by liga- mentum flavum: unilateral laminotomy for bilateral liga- mentectomy. Preliminary report of two cases. Neurosur- gery 37:343 – 347
13. Schatzker J, Pennal GEF (1968) Spinal stenosis, a cause of cauda equina compression. J Bone Joint Surg Br 50:606 – 618
14. Silvers HR, Lewis PJ, Asch HL (1993) Decompressive lum- bar laminectomy for spinal stenosis. J Neurosurg 78:695 – 701
15. Verbiest H (1975) Pathomorphologic aspects of develop- mental lumbar stenosis. Orthop Clin North Am 5:177 – 196 16. Wang JC, Bohlman HH, Riew KD (1998) Dural tears sec- ondary to operations on the lumbar spine. J Bone Joint Surg Am 80:1728 – 1732
