Spinal canal stenosis

P. KOROVESIS, G. KOUREAS, G. PETSINIS
Department of Orthopedics "Saint Andrew" Patra General Hospital

 

INTRODUCTION
The term "spinal stenosis" means stenosis of the spinal canal, in which noble neural elements (spinal cord & roots) are included. However, it is known that spinal canal stenosis with or without compression on spinal roots is found in asymptomatic persons as well4. Thus, spinal stenosis itself cannot explain all clinical symptoms and signs which are observed with patients who suffer from spinal stenosis clinical syndrome.
Spinal degeneration process, because of aging, leads to pathologic and pathophysiologic changes, which occasionally are related to clinical symptoms and objective findings. It seems that it is not only the stenosis of spinal canal itself which takes place, but it has been proved that abnormal motion of spine contributes as well and can increase the degree of compression on neural elements which are included in the spinal canal. Gradual degeneration of spinal diarthroses and intervertebral disks and the following compression on neural elements could lead to symptomatic spinal stenosis, although the seriousness of clinical symptoms is not necessarily related to the degree of radiographic stenosis & compression on noble neural elements.

CLASSIFICATION
Spinal stenosis can be acquired or be congenital. The congenital one is common with patients who suffer from achondroplasia or any other syndrome which causes nanism. Congenital stenosis has also to do with persons with normal height, with small vertebral arches and normal intervertebral disks in multiple levels. In congenital spinal stenosis symptoms frequently appear between the third and fourth decade of life.
On the other hand, acquired or degenerative stenosis becomes symptomatic with women aged around 70 and men of somehow younger[60]. Degenerative spondylolisthesis, which is more common in women, is a common cause of spinal stenosis[47].
Despite the fact that many causes lead to spinal stenosis, this review will focus on spine degeneration process. Degenerative changes and consequently stenosis, could appear either medially in the spinal canal or at lateral diverticula (leading to compression of nerve roots from a hypertrophic articular process), or at the vertebral foramen, or finally outside the vertebral foramen from osteophytes, intervertebral disk, transverse processes or from lumbosacral joints (5th lumbar root).

ANATOMY
Spinal canal is related anteriorly to the intervertebral disks, the posterior longitudinal ligament and the vertebral bodies. Its lateral limits are related to the lateral expansion of ligamentum flavum and the vertebral arches. Posterior elements are ligamentun flavum, vertebral arch, and posterior articular processes. Vertebrae foramens are related anteriorly to the intervertebral disks and the vertebral bodies, posteriorly to the articular processes and finally superiorly to inferiorly to the vertebral arches.
The average anteroposterior diameter of spinal canal is 12 mm[20,21,73], while the minimum area of spinal canal’s transverse surface is 77±13mm2 so as the neural elements which are included in it not be compressed[20,73,84].
Inside spinal canal neural elements are organized in a predetermined way. The most posterior neural elements inside the canal are those of Ι5 root whose course is anteriorly from the 4th up to 1st sacral vertebra, between the 5th lumbar and first sacral disk. The most anterior element between the 5th lumbar and 1st sacral disk is Ι root. Between the fourth and the fifth lumbar vertebra, O5-root heads anterolateral displacing Ι1 root posteriorly. This arrangement moves symmetrically with every root to be added superiorly at every disk’s level[14,99,100]. Motor neural fibers are placed anterolaterally while sensory fibers posterolaterally. Special sensory and motor neural fibers are in the vicinity and they have an oblique orientation. Inside the vertebral foramen there is the dorsal ganglion, whose anterior part consists its motor unit and the posterior part its sensory unit which is the largest. The dorsal ganglion is almost always entrapped in the vertebral foramen and commonly it is in the intervertebral disk’s respective area at vertebrae arches’ level[13].

PATHOLOGY: DEGENERATIVE PROCESS
The main three biochemical components of the intervertebral disk are water, collagen and proteoglycans. These components constitute 90-95% of a normal intervertebral disk volume[24,31,67]. Collagen is arranged in concentric arches allowing disk’s straining while, in parallel, connects the aside vertebral bodies. Proteoglycans lend hydrodynamic and electrostatic properties and control texture of the disk via regulation of fluids’ exchange inside disk.
Water which is included inside intervertebral disk is transformed according to the applied mechanical loads but it usually consists the biggest part of the disk’s weight. With aging the amount of water which is included in the disk reduces[24,31,67]. While the nucleus pulposus dehydrates, its ability to distribute loads declines leading to tears and fissures inside annulus[17,68].
Collagen gives to the disk strength to traction. Nucleus consists exclusively of collagen fibers type ΙΙ[23,38], which help in maintaining high levels of hydration by conserving water and allowing disk to resist to distortion and compression forces. Annulus consists of almost the same percentage of collagen fibers type Ι and ΙΙ. Percentage of collagen fibers type Ι increases in disks of middle age and older persons[2,8].
Proteglycans’ number inside intervertebral disk is lower than that in articular cartilage, they have smaller nucleus and consist of different percentages of sulfur keratins and sulfur chondroitins chains[89,90]. Resistibility of a disk against compression has to do with proteoglycans which are found in higher percentage in nucleus pulposus compared to annulus[2,93]. With aging and disk’s degeneration, the total percentage of proteoglycans reduces[68,9]5. The rate of proteoglycans synthesis declines with aging as well.
Studies in electron microscope prove that biochemical components of disks have an architectural arrangement which reflects their biochemical properties. Annulus is composed by collagen fibers arranged in laminae which are crossed on 40-70Æ angle. These fibers give strength against traction forces. Densely arranged fibers of annulus fibrosus become less dense and organized in transmission from nucleus to annulus and consist a loose network inside nucleus pulposus.

DEGENERATION OF INTERVERTEBRAL DISK
Degeneration of intervertebral disks is the first stage of the spinal articular processes degeneration[52-54]. Despite this, arthritis in articular processes is possible to precede any disk degeneration[97].
During childhood and adolescent the annulus fibrosus is of gelatinous consistency. As time goes by the annulus fibrosus is subject to fibrocartilagenous metaplasia and chondrocytes are shown inside it. Gradually, the exact limits between nucleus pulposus and annulus fibrosus become hard to discern. Dehydration, formation of cavities and fibroelastic tissue take place resulting in replacing of annulus pulposus by fibrocartilaginous tissue[15,36,76].
The highest frequency of disk degeneration is observed with persons aged between 25 and 35. At the age of 50 most people have some kind of disk degeneration. Disks between O5-Ι1, as well as between O4-O5 are those that degenerate more often[65].
Biomechanical and biochemical changes lead to a reduction of disks’ height. It can be observed rupture of the annulus, intervertebral disk herniation and premature appearance of osteophytes. Because of these changes, increased loads are shifted posteriorly at facet joints, resulting in changes to these joints and instability follows. As disk degenerates and spinal canal is narrowing medial as well in lateral notches, nerve roots can be entrapped.
Degeneration of spinal facet joints is similar to other joints. With ageing, osteoporosis increases with simultaneous loss of articular cartilage and reduction of articular cavity. Osteosclerosis which can be observed in facet joints commonly is reduced as time goes by, while differentiation’s in load distribution take place. As degeneration process goes on changes of facet joints include: hypertrophy, pachynsis of upper articular capsule and osteophytes formation.
In addition to the articular and osseous changes, facet joints of the vertebrae are sedimentated and eroded[30,106]. In the early stages where disk degeneration rate overcomes that of facet joints changes, it could happen a small degree of posterior spondylolisthesis of the upper vertebral body over the lower one. However, if facet joints degeneration degree, including osseous and cartilaginous erosion as well as loosening of articular capsules, overcomes the degenerative changes of the disk, an anterior subluxation could happen. This is especially true when facet joints are located at saggital level[34].
With many persons a gradual alteration of the spinal saggital profile is observed (kyphosis- lordosis). This, combined with the widening of ligamentum flavum posteriorly and protrusion of the disk anteriorly, it causes spinal canal narrowing leading to a further compression on neural elements[7].

SECTIONAL INSTABILITY
Three-dimensional arrangement of the spine with normal disks, facet joints and ligaments allows a normal and symmetrical version and angulation of its levels, without important changes to the spinal canal and its foramina dimensions. As spinal degeneration process progresses, spinal canal and foramina are affected more and more by rotational motions and inclinations, because of changes in disks and facet joints. As degeneration is accompanied by disruption of motion as well, irritation of cauda equina neural elements is provoked leading to manifestation of pain[25,29,69].The common manifestation of degenerative spondylolisthesis at O4-O5 level of lumbar spine, is the result of restraint forces that exert on the body and its transverse processes of O5 vertebra from iliolumbar ligaments, which immobilize the fifth lumbar vertebra and allow increased motion of the upper vertebra leading to subluxation[58].
The unusual biomechanical loads over vertebra with the greatest motion can be noticeable radiologically either from the narrowing of the intervertebral space or from the osteosclerosis to endplates of vertebral bodies. Radiologically, benign idiopathic sclerosis can resemble inflammation. However, in this case sclerosis is restricted in the region near intervertebral disk. Instability presence occurs because of great osteophyte presence.
Degeneration leads to chemical, mechanical and anatomic alterations which in turn cause nerve root compression in all middle-aged or older persons. Degenerative processes are visible in all persons over 6065. However, most persons who have evidence of mechanical nerve root compression don’t feel pain. In reality neurological deterioration is rare even with patients who express pain of such intensity that leads them to elective spinal operation. Sometimes symptoms subside as time goes by, even if decompression has not taken place. Other patients don’t show alterations in their initial clinical symptomatology regardless that degenerative process advances, while finally other patients show a gradual deterioration of symptoms[45,47,66]. Symptoms and signs of neurogenous paresis are exclusively related to the degenerative changes.

PATHOPHYSIOLOGY
Nerve compression
Pathophysiology of pain which is related to the nerve root or cauda equina compression is not absolutely clarified. Studies have shown that compression is related to symptoms and signs connected with neurogenous paresis. However, compression by itself does not cause pain[4,28,79,103]. For pain to be, irritation and inflammation of nerve root has to coexist resulting in symptoms from lower extremities[87]. Compression of a normal nerve leads to paresthesias, hypesthesia, paresis and disturbance of reflexes but usually without the presence of pain. However, if an irritated nerve is compressed then pain is present simultaneously with the other objective findings[61,81,92].
Damage to a spinal root can be detected in vitro during mechanical check with Video Dimension Analysis use before evidence of nerve disturbance found[55]. Theoretically, this internal damage could also happen in vivo as well if the nerve is under stress in asymetrical way. This cross-section combined with increased intraneural stress could lead to irritation and inflammation toward the course of the nerve. Irritation and inflammation could also occur during spinal or lower extremities motions. Then the nerve is forced to elongation and deviation from rest position[7].In a spinal canal which has no stenoses and generally there is no serious degeneration, the nerve moves up to 5mm inside the vertebral foramen during hip flexion with lower extremities stretched[86]. If the free motion of the nerve is restricted, its internal stress increases and in addition small ruptures of the nerve happen, leading to inflammation reactions.
Although imaging studies provide static pictures of the spine at a particular time, the effect of spine micro- or macro- motions on the nerve roots could be gradual and dynamic. These alternating forces over the nerve roots could lead to irritation and inflammation. This can be attributed to subluxation or to intermittent compression caused by ligamentous damage, disk protrusion, osteophytes or by vascular and nerve entrapment.

COMPRESSION
Compression can cause electrophysiologic alterations along nerve root. This can cause irritation of nerve fibers responsible for pain, resulting to expression of pain. Results of the compression gradual increase on cauda equina were studied experimentally with guinea pigs[59,70-72,82]. A two-hour compression was applied and after that removal of compression followed for one hour and a half. Electrophysiologic changes were observed either to afferent or to efferent nerve fibers. Two-hour compression with lower pressure than diastolic, causes non-reversible changes to afferent and efferent nerve fibers. Compression pressure between 75 and 100mmHg leads to a gradual reduction of conductance both to afferent and efferent nerve fibers as well. The effect on afferent nerve fibers is faster, but on the efferent fibers (motor fibers) restoration is faster and more reliable. Compression of 200mmHg which is higher than average pressure, causes a fast reduction in conductance with almost no restoration of afferent conductance after removal of compression and only by 30-40% restoration of efferent conductance[59,71,72,82].
Duration of compression is also important. Increase in compression duration from 2 to 4 hours have an effect on the nerve ability to return to its initial condition[78]. Although the initial alteration is the same, restoration of nerve function is prolonged remarkably, especially at pressure of 100mmHg when pressure duration is doubled. These alterations are greater in afferent fibers compared to efferent fibers.
Edema and deficiency in nutrient ingredients are related to the degree of pressure and the rate of its establishment. The higher the pressure and the faster the establishment is, the greater the edema and deficiency of nutrient ingredients are[71].
Reduction in the rate of blood flow is another parameter which can be related to spinal stenosis symptoms. After pressure application to guinea pig nerve, a gradual compression of venulae was observed, following by capillaries and at last at arteriolae[80,81]. At the same guinea pig hypotension led to a decline in electrophysiologic conductance, as oppose to hypertension which protected the nerve by reducing electrophysiologic alterations because of the increased blood supply[80,81].

CLINICAL ENTITY
Because spinal stenosis is a slow degenerative process, early symptoms are commonly indistinct. General pains at the loin with difficulty in flexion are usual the first complaints. These complaints are usually getting worse with the increase of activity and subside with rest. Pain at loin and buttocks may remain for a long time. Few patients accept these complaints as an unavoidable outcome of aging process restricting their activities.
The usual symptoms of the spinal stenosis or neurogenous paresis are displayed at lower extremities and include pain, numbness and tingling at posterior or posterolateral part of extremity. Although pain usually starts from the loin and reflects downwards, it can be regions where pain starts from periphery and reflects more central. Symptoms could be asymetrical and unstable. It is possible to be modified from day to day or to be expressed sometimes on the right and other times on the left. Other symptoms are cramps, feeling of unbalance and diffuse paresthesia[35,88,105].
Sudden start of pain at lower extremities or sudden deterioration of already existed symptoms is rare enough and is related to intervertebral disk herniation or to disturbance of neural elements blood supply.
The usual clinical findings in a patient with spinal canal stenosis are the intensification of complaints at lower extremities when these are extended and the subsidence when these are flexed. This possibly is due to the reduction of spinal canal capacity when extremities are extended[22]. Pain usually subsides quickly with changing of posture or activities. However, because of the coexistent spondylolisthesis, it is not rare for complaints to be expressed at loin flexion. This is due to the fact that the vertebral bodies subluxation is intensified, resulting in pressure increase on nerve roots. Although the usual symptoms are located at lower extremities, it should not be overlooked the fact that symptoms can be manifested at loin or buttocks.
Urinary disturbances are unusual in patients with spinal canal stenosis[46]. However, there are patients who report a feeling of urgent need for urination, frequent urination or urine loss. A factor which often causes confusion is the age because these symptoms are common with old persons who do not suffer from spinal stenosis.
Differential diagnosis includes paresis which is caused by blood supply disturbances, peripheral neuropathy and lumbar spondylitis[19,37]. In patients with angiopathy, complaints are located mainly at tibia and subside with rest. In contrast to the pain which is caused by neurogenous paresis, pain of angiopathy does not subside with changing of body posture but only with limitation of activities.
Peripheral neuropathy is commonly characterized from pain at both lower extremities having a distribution of a sock instead of a typical nerve root distribution9. It can be observed bilateral symmetrical loss of reflexes and sensory neuropathy before motility is reduced. In addition, vibration perception is declined. Alternatively, it can be observed muscular weakness without sensory disturbances. A patient has to be checked for diabetes mellitus, drugs’ use and alcoholism. Malignant tumors and renal failure could also have symptomatology which resembles that of peripheral neuropathy. Electromyography and conductance tests of nerves are useful[43].

PHYSICAL EXAMINATION
Frequently, no abnormal findings are shown with neurologic check. Although many patients report weakness of lower extremities, during clinical examination no muscular weakness is found.
However, with quite a few patients, neurologic abnormalities are located. So asymmetry at quadriceps reflexes or Achilles is compatible with spinal canal diagnosis. If reflexes are absent symmetrically especially the Achilles, this is attributed more frequent to the age instead of the spinal canal stenosis. At last abnormal Babinski reflexes or clonus presence are not related to the spinal canal stenosis at lumbar spine level. If the above mentioned signs exist the examiner should check for cervical or thoracic stenosis or for the presence of other spinal cord neurologic diseases.
Motion check is usual more accurate as far damage location is concerned. Weakness of muscles which are innervated from the 5th lumbar root is the commonest finding. Special attention should be paid during checking the hallucis longus muscle extensor and the medius and minimus gluteus muscles (with Trendelemburg test). Weakness of iliopsoas is compatible with 2nd lumbar root compression. Inability of knee extension (quadriceps) indicates damage to the 3rd and 4th lumbar root. The anterior tibial muscle (dorsal flexion of ankle joint) is innervated from 4th and 5th lumbar root. Inability of plantar flexion of ankle joint or inability to walk on toes indicates damage at 1st sacral root.
The clinical check after neurological fatigue test takes place after asking the patient to walk fast till symptoms appear. Duration and walking rate are not predetermined. Patient walks till complaints that he is referring to become noticeable. Lasegue sign may not appear even in patients with radicular pain.
In differential diagnosis malignancy, inflammation, osteoporotic spine fractures and circulatory disturbances should be included. Assessment of the first three is takes place clinically with palpation in the middle line of spine, so it can be identified widening of space between spinous processes, and with percussion so pain is elicited. Hip motility also should be checked especially if pain is located in that region, as well as possibility of femur trochanteritis should be excluded. Osteoarthritis appears at the same ages as the spinal stenosis. Vascular check should include palpation of peripheral arteries and if it is necessary of abdomen too, so aneurysm existence probability to be excluded.

IMAGING STUDIES
Simple radiological check should not be overlooked in patients with spinal stenosis symptomatology. Anteroposterior and lateral radiographs with spine in flexed and extended position provide useful information in connection with stability and deformation of spine. These radiographs should be studied when there is suspicion of degenerative spondylolisthesis or great instability during flexion and extension of spine. In addition, check for spine deformity (e.g scoliosis) or for the presence of vertebrae distortions (e.g osteoporotic fractures, or tumors), which could be the cause symptom, should take place.
Magnetic tomography became quickly the test of choice for spinal stenosis check and for planning of surgical management. However, generally speaking, diagnosis may be made with history taking combined with physical examination and simple radiographies. Magnetic tomography should be carried out when operation planning is going to take place, when multiple stenosis levels should be evaluated as well as tumors and inflammation are to be excluded. Medial as well lateral stenoses of the spinal canal could be evaluated accurately with magnetic tomography. Abnormalities of vertebral body articular processes, osteophytes, intervertebral disks’ hernias, and damage of ligaments are also visible with magnetic tomography[66].
Computed tomography without contrast use in spinal canal is not specific for investigation of patients with possible spinal stenosis because more than one level is usually implicated, so many sections are required for the whole lumbar spine to be examined. In addition, with computed tomography neural tissues are not imaged satisfactorily resulting in a possible tumor of spinal cord to be undiagnosed. Computed tomography with contrast administration in spinal canal is particular useful, especially in patients with scoliosis and in these with instrumented spinal fusion. Myelography sets the boundaries of neural elements and can help with the investigation of medial stenosis. At last computed tomography which takes place after myelography provides useful information about lateral notches, hypertrophy of facet joints and osteophytes.

TREATMENT
Indications of treatment
There are a few papers about the course of the spinal stenosis and these are based on a small number of patients[45].
As far as we know, it is known that no serious neurologic deterioration occurs with patients who were managed conservatively for spinal stenosis. It is also known, that full restoration of all abnormal findings is rare. At the same time, a percentage of patients, similar to these patients whose symptoms subside with conservative management, presents deterioration of symptoms. From the above mentioned, we conclude that surgical management of patients with spinal stenosis frequently can be postponed. Decision for surgical treatment should be based on deterioration of a patient’s quality of life and symptoms, instead of abnormal neurologic findings and positive findings, for spinal stenosis, at magnetic tomography. It should be understandable, that surgical treatment is not expected to be always successful as far as concerns the reversibility of abnormal neurologic findings.

CONSERVATIVE TREATMENT
Patients who complain about lumbar pain and pain at lower extremities, which is related to spinal stenosis, usually require some kind of treatment. Generally, conservative methods could be beneficial for many patients. The first measures are patients’ information, assurance that it is about a disease which can be managed, administration of analgesics, non-steroidal analgesics[44,96,98] even narcotics if it is necessary. Exercise is of great importance[32,42] because it improves cardiopulmonary function with aerobic exercises, static bicycle with the patient to exercise in a semi-seated position with a slight anterior trunk inclination. Physiotherapies are helpful[63,64], even though their usefulness is not easy to be proved scientifically. Various lumbar belts[104] provide, though limited, support of the trunk and relief. However, they should not be used for a long time as muscle wasting is to be avoided.
Another alternative therapy for reducing painful complaints of lower extremities is the infusion in epidural space with steroids. We are not acknowledged of any randomized study about such infusions in patients exclusively with spinal stenosis. However, it has been observed that such infusions help significantly for the relief of these complaints. Epidural infusion of steroids is relatively safe and well tolerated with most of the patients[10,18,77]. They have minimal adverse effects, though accurate infusion in epidural space of a patient with degenerative spondylarthritis could have technical difficulties. It is not rare, because of the underlying deformation and stenosis, infusion of substance inside dura mater to cause headaches, nausea and vomits when patient stands up. These complaints usually subside with short-term bedding.
Special attention should be paid to the recommended treatment in old persons. Acetaminophen may affect both hepatic and renal function as well. Non steroidal anti-inflammatory drugs may lead to gastric and duodenum ulcers. They can also affect hepatic and renal function and also cause Na+ retention provoking hypertension. Exercises and physiotherapies have some disadvantages like pain deterioration. However, exercise improves the general status of the body and prepares the body to tolerate the surgical operation stress even if it does not reduce pain.

SURGICAL TREATMENT
Surgical treatment is indicated when a patient’s quality of life has such a deterioration that it is not tolerated by the patient. With such patients, pain, numbness and weakness in one or both extremities restrict their every day activities to a significant grade. If findings from physical examination are persistent and magnetic tomography shows spinal stenosis, then surgical treatment constitutes treatment of choice.
Laminectomy with decompression of nerve roots is the usual procedure which is chosen for the relief of complaints from the lower extremities and are related with spinal canal stenosis[40]. It has to be emphasised that surgical treatment takes place for a patient’s relief of lower extremities complaints and not for reducing lumbar pain, even though there is frequently a reduction of lumbar pain postoperatively. In addition, with spinal canal decompression, laminectomy should decompress the nerve roots in all involved levels.
Another alternative surgical treatment is the limited laminectomy with foraminectomy. This is achieved with the removal of the spinous processes, interspinous ligaments and of a large part of lamina. Laminectomy takes place at articular processes level removing 1/4 - ó of articular surface in parallel with the excision of the ligamentum flavum lateral part.
Because spinal stenosis very commonly includes multiple levels, decompression should include all involved levels which have been pointed out by the imaging control, even though clinical examination indicates fewer or only one level of compression.
If there is any deformation, especially degenerative spondylolisthesis or flexible scoliosis, then arthrodesis with or without spinal fusion instrumentation[33,40] can take place. Of course arthrodesis makes the operation more complicated, prolongs it, increases blood loss, complications and finally prolongs rehabilitation time[12,94].
A controversial topic which is frequently under discussion is the kind of surgical treatment which is chosen for spinal stenosis management. That means if laminectomy is sufficient or if arthrodesis should take place as well. Factors which should be taken into consideration are the spinal preoperative structural changes as well as perioperative structural alterations.

PREOPERATIVE STRUCTURAL CHANGES
Degenerative spondylolisthesis
Many articles have been published related to whether arthrodesis should take place in parallel with decompression and laminectomy[11,16,26,40]. However, the importance of arthrodesis in patients with spondylolisthesis has been proved. Herkowitz and Kurz presented a prospective study that they compare decompression and laminectomy with decompression and laminectomy which is followed by arthrodesis between transverse processes, in fifty patients who had spinal stenosis at only one level simultaneously with degenerative spondylolisthesis[40]. 24 out of 25 patients who had been submitted to arthrodesis had excellent results. The writers recommended arthrodesis in all patients with degenerative spondylolisthesis who were submitted to decompression and laminectomy. Quite a few reports claim the importance of arthrodesis, when at the level of stenosis degenerative spondylolisthesis coexists[11,26,50,83].
Caputy and Luessenhop studied 96 patients who were submitted to decompression spinal stenosis treatment[11]. Five years after operation, treatment was considered unsuccessful in 26 patients. From these 26 patients, 16 had constant complaints at lower extremities and 5 out of these 16 patients had already degenerative spondylolisthesis with symptoms at lower extremities which were related to the level of spinal stenosis. The writers concluded that simultaneously with laminectomy, arthrodesis should take place when degenerative spondylolisthesis coexists in patients.
Postacchini et.al studied regeneration of lamina in patients who were submitted to laminectomy because of spinal stenosis[75]. Out of 40 patients, who were followed up for 8,6 years on average, 16 patients had degenerative spondylolisthesis preoperatively. 6 out of 16 patients were submitted just to laminectomy and the other 10 were submitted to arthrodesis as well. Patients who were not submitted to arthrodesis had more osseous production and poorer clinical results compared to those who were submitted to arthrodesis.
Thus, the existing evidence concerning spondylolisthesis related to spinal stenosis, leads to the conclusion that arthrodesis should take place during laminectomy.

COLIOSIS AND KYPHOSIS
Surgical treatment of patients who suffer from spinal stenosis in combination with preexisted idiopathic or degenerative lumbar scoliosis is not so clear as is in patients whose stenosis is combined with degenerative spondylolisthesis[85,107].
It is not necessary for all patients who are managed with decompression because of spinal stenosis on the verge of a spinal scoliotic or kyphotic region, to be submitted in arthrodesis. Decision for arthrodesis should be based on some parameters. First parameter which should be considered is the flexibility of curvature. If the curvature is corrected, even partially in radiography of spinal lateral flexion (bending test), then decompression with laminectomy will possibly increase the risk of curvature deterioration. Second parameter is the documented from the history deterioration of curvature which consists indication for arthrodesis. Third parameter is the presence of scoliosis with coexisted radiculitis which is located at the concave of the scoliotic spinal part. In this case, laminectomy with partial removal of facet joints may not be enough for removing pressure from the compressed root. Fourth parameter is the lateral spondylolisthesis. The lateral spondylolisthesis which is located at one level and which is proved radiologically with lateral bending test indicates hyperkinesis which deteriorates with decompression and laminectomy. Fifth parameter which should be considered is the loss of lumbar lordosis to such an extent that the patient has not balance at the saggital level. This can be estimated with lateral x-ray which includes the whole spine from the base of the skull up to sacral bone. In this x-ray the plumb-line should pass through half posterior of the fifth lumbar vertebra of the normal spine. Laminectomy may deteriorate kyphosis increasing lumbar pain.

RELAPSE OF SPINAL STENOSIS AT THE SAME LEVEL
Patients who are submitted to a second laminectomy for decompression at the same level, are candidates for arthrodesis[41]. Additional removal of facet joints is usually necessary for the medial decompression. Removal of more than 50% of articular surface leads to instability at the particular level, especially if these articular surfaces are oriented at saggital axis[1,5,56]. Segmental instability can be studied with radiological check of the spine in anterior and posterior inclination. Excessive motion of the examined level is defined its displacement more than 4mm or its angulation more than 101 in correlation with the upper and lower level of spine.
Patients whose have relapse of spinal stenosis because of iatrogenic spondylolisthesis benefit from arthrodesis due to the fact that instability is deteriorated after a second decompression[50].
With the increase of spinal fusions in the last 15 years, spinal stenosis appearance at the spinal levels which abut with the parts that have been submitted to arthrodesis is common enough[57]. Alternative methods of surgical treatment which are applied in these cases are either simple decompression or decompression followed by instrumented or non-instrumented spinal fusion. Detailed prospective studies with large number of patients are missing form medical literature and for this reason recommendations are difficult to be put forward[102]. However, it is logical to recommend simple decompression for patients whose stenosis is cephalic in relation to arthrodesis site if perioperatively instability is not possible to be controlled and there is an excessive motion of articular surfaces.

PERIOPERATIVE STRUCTURAL CHANGES
Removal of facet joints
Abumi et al proved the importance of facet joints for structural stability of lumbar spine movable parts in cadavers1. After cadavers were subjected to cyclic loading with mechanical arrangement, the writers concluded that more than 50% of facet joints removal leads to instability of moveable parts.
Similar results were reported by Boden et al. once again with examination of cadavers5. These writers concluded that stability of moveable parts was not weakened after lumbar spine laminectomy if the inner half of every facet joint was conserved. When removal is extensive, that means more than 50% then posterolateral arthrodesis should be considered seriously if postoperative instability is to be avoided.

Discectomy
Intervertebral disk herniation, although rare, is possible to be related to the spinal stenosis[40]. Usually, intervertebral disk herniations in patients with spinal stenosis consist of disks' free parts bulging respectively with vertebral foramina. In these cases, removal of disks' free parts during laminectomy is necessary if complaints are to be reduced. The so called radical excision of intervertebral disk may lead to iatrogenic spondylolisthesis because of anterior column disturbance given that posterior column weakened because of laminectomy[16]. Thus, radical removal of disk is not recommended.
Spinal fusion instruments
The target of internal fixation is to repair the deformation, to stabilize the spine, protect neural elements, improve porosis rate, reduce the number of levels which are about to be included in spinal fusion and to reduce patient's rehabilitation time.
Osteosynthesis which is extended up to the lower loin and sacrum presents problems especially in elderly persons. It s not possible hooks to be placed in patients who have been submitted to laminectomy. In addition, the usual posterior hooks, with which straining takes place often lead to the loss of lumber lordosis. Conservation of lumbar lordosis is an important factor for long term success of arthrodesis. Failure of lumbar lordosis conservation could lead to deformation (flat back) and pain at dorsum.
Placement of instruments on vertebrae' pedicles solves a few problems which are related to the traditional systems of spinal fusion when the use of spinal fusion instruments is considered necessary because of lumbar spine decompression and laminectomy. Stabilisation with use of materials at vertebraeΥ pedicles, succeeds in the placement of materials at the most powerful parts of osteopenic vertebrae and allows the segmental stabilisation which improves rotational stability and lumbar lordosis conservation. Also, segmental stabilisation reduces the number of moveable parts which should be included in arthrodesis, allowing this way some kind of loin motion. Stabilization of sacrum is better with the system of transpedicle screws compared to the hooks and plates systems. In addition, spinal deformation is reduced more effectively with the use of segmental transpedicle screws.
However, the use of transpedicle screws has some disadvantages[101,108]. Failure in the correct placement of screws may lead to neurologic disturbances and failure of arthrodesis. In addition, longevity of transpedicle screws is unknown[6].
The surgeon who intends to do a spinal arthrodesis should evaluate the benefits and risks from such an operation. In most of cases materials' placement takes place to establish a stable arthrodesis and to correct deformations. Fischgrund et al. compared the results of laminectomy which took place in combination with posterolateral arthrodesis in 68 patients who had spinal stenosis and degenerative spondylolisthesis with another group of patients who was submitted to the same operation with additional use of spinal fusion instruments[27]. These writers found that in the patients to whom materials had been placed the porosis formation rate was higher. However, clinical results in both groups were similar.
The incidence of pseudarthrosis after lateral arthrodesis without the use of materials increases with the increase of spinal fusion levels. Also, it increases if there is instability. Use of spinal fusion instruments reduces the incidence of pseudarthrosis[108].
Indications for the use of spinal fusion materials in patients in which laminectomy and arthrodesis have taken place because of spinal stenosis are: 1) correction or stabilization of scoliosis or kyphosis, 2) arthrodesis with simultaneous laminectomy at two or more levels, 3) relapse of spinal stenosis with coexisted iatrogenic spondylolisthesis and 4) horizontal displacement of vertebral bodies more than 4 mm and angulation more than 100 when spine is checked in anterior and posterior inclination. The use of materials for arthrodesis of one level in patients who have been submitted to laminectomy because of degenerative spondylolisthesis increases the rate of porosis compared to those patients where no material have been placed. However, it doesn't seem to have any effect on long-term clinical results[27].
There are many things that have to be clarified in relation to arthrodesis and materialsΥ use in degenerative diseases of lumbar spine.

COMPLICATIONS OF SURGICAL TREATMENT
Surgical treatment has as a target to stop radiculitis or neurogenous paresis at lower extremities. Patients who present with localized pain at loin without deformations usually are managed successfully with non-surgical methods. The results of surgical treatment are frequently affected by several diseases like cardiopulmonary diseases, diabetes, renal diseases and at last nutrition. In patients with these problems rehabilitation period is frequently prolonged. Old age of a patient is not necessarily a contraindication for surgical management, especially in our days where life expectancy has been improved.
Generally, surgical treatment has led to a high percentage of clinical improvement of spinal stenosis symptoms, especially with alleviation of pain at lower extremities. The targets of surgical treatment is to relieve from pain and improve patientsΥ quality of life[33,40,62]. The results are more successful as the patients' health problems are fewer[12,49,51].
Because spinal stenosis is presented mainly at older ages, the incidence of complications which are related to surgical treatment is higher compared to spinal operations with younger persons.
ComplicationsΥ analysis of surgical treatment requires a wide population pool if safe reference data are to be reported. The most widely used reference data though they are not absolutely accurate or ideal, are coming from the National Hospital Discharge Survey. Data from these sources are not as accurate as those of a trial which has a wide control group, however, they provide a relatively accurate estimation of complicationsΥ incidence from a great number of patients. Ciol et al analyzed the data out of 30.000 patients who were submitted to posterior spinal fusion because of spinal stenosis during 1985 - 1989[12]. Complications were classified in 4 groups. 1) Inflammations, 2) Vascular disturbances, 3) Cardiopulmonary disturbances, 4) Death. Mortality was related to the age and accompanied health problems. Patients younger than 75 years-old were presenting mortality lower than 1% while patients older than 80 years-old were presenting mortality higher than 2.3%. Complications were two times more frequent in patients older than 80 years-old compared to patients younger than 70 years-old. ComplicationsΥ incidence was doubled when three or more accompanied health problems coexisted or when during arthrodesis decompression took place simultaneously.
In the study which was conducted by Katz et al re-operation took place in 15 out of 88 patients[48]. The need for revision of operation after surgical treatment of spinal stenosis is related to several parameters[39,48]. Firstly, spinal stenosis can be presented at other levels because it is associated with the degenerative process frame. Secondly, the criteria for the operation may not be accurate. Operation might not have as a result the full decompression of spinal canal and the advisable surgical technique not to be followed as it should. Thirdly, surgical management might have failed because of instability, resulting in inadequate porosis and with possible failure of spinal fusion instrumentation. Fourthly, spinal stenosis may reappear because of vertebraΥs lamina regeneration[74].

RESULTS
Like all surgical operations, successful results depend to a large extend on patientsΥ choice and the application of the appropriate surgical technique91. Katz et al. published the results of 194 patients who were submitted to decompression because of spinal stenosis and who were followed up for 6 months[49]. Forty patients were not satisfied with the result of the treatment[49]. Patients' dissatisfaction was related to their bad functional condition preoperatively, the presence of many accompanied health problems and persistence of pain at loin compared to complaints at lower extremities[49]. In conclusion, long postoperative follow up of these patients showed that a very high percentage was satisfied from surgical treatment[39,48,50].
Although, patients continue to have loin pain, most of them are satisfied with the result of surgical treatment and would accept to be submitted again to such an operation under the same conditions. Surgical treatment seems as a better choice than continuous conservative treatment when there are clinical and radiological evidence which is in favor of such a therapeutic approach[45].

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