Aust. Radiol. (1979),23,61

Lumbar Spinal Canal StenosiS PETER DEWEY, F.R.C.S. Orthopedic Surgeon, Wagga Wagga Base Hospital. PHILIP SOUTHWELL, DD.R.(Syd.), M.R.A.C.R.,* Director of Radiology, Wagga Wagga Base Hospital, N.S.W. 2650. Spinal canal stenosis has been defmed (Arnoldi et a1 1976) as “any type of narrowing of the vedebral canal, nerve tunnel or intervertebral foramina”, and the purpose of this paper is to submit that spinal canal stenosis is a potent cause of claudicant-type symptoms in the lower limbs. These effects led Blau and Logue (1961) to coin the name of intermittent claudication of the cauda equina. Verbiest (1954) described the symptoms of lumbar stenosis as radicular pains with impairment of sensibility and motor power in the legs on standing and waking, relieved by rest and flexion of the spine. This clinical syndrome has led to confusion with claudication of the legs from vascular causes. Lumbar spinal canal stenosis has a variety of causes (Table 1) from the congenital type seen in achondroplasia through degenerative spinal disease to frank malignancy. Degenerative disease of the lumbar spine is the commonest cause and this paper stresses that aspect of the problem.

CLINICAL FEATURES The classical history is of a male patient usually over the age of 50 yeas with a history of back ache presenting with worsening pain and radiation of the pain to one or both lower limbs. Lower limb pain at rest is uncommon but with exercise or prolonged standing, pain radiates into the buttocks and upper thighs. With further exercise, the pain worsens and paraesthesiae occur in the

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TABLE 1 Aetiology of Spinal Canal Stenosis I. Congenital and developmental: (i) achondroplasia. (ii) idiopathic. 11. Acquired (i) degenerative (spondylosis with or without disc prolapse). (io spondylolisthesis (degenerative or spondylolytic). (5)iatrogenic - postoperative. (iv) miscellaneous: a) infective b) neoplastic c) Post-traumatic d) Paget’sdLsease

*Present appointment: Director of Radiology, Ryde Hospital, Eastwood, N.S.W. 2122.

Australasinn Radiology, Vol. XXIII, NO. 1, March, 19 79

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D

FIGURE 1.- Cross-sectionsof the Vertebral arnal A. Normal B. Osteoarthrosis of the apophyseal joints C. Narrow vertebral anal (mall antero-posterior diameter) D. Intervertebral disc protrusion.

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P. DEWEY AND P. SOUTHWELL lower limbs with a feeling of heaviness, numbness and weakness. At this stage the patient will often complain of a limp and even of falling. Standing still will not relieve the pain and the patient must sit, lie or flex the spine by supporting the body weight with hands on thighs to obtain relief. Loss of sphincter control and sexual dysfunction are associated with the syndrome at its extreme. This clinical history differs from that of claudication of vascular origin where the pain usually occurs in the calves while walking, and not in the upper thighs or back. Paraesthesiae are uncommon and the patient rarely falls. No motor disturbances develop and as soon as the patient stands still, the pain is relieved; it is quite characteristic that he does not have to flex his spine or sit for relief. Prolonged standing usually does not provoke pain of vascular origin but often causes the symptoms of lumbar spinal canal stenosis to develop. Physical examination in spinal canal stenosis often reveals a stiffish back due to degenerative disease and there is often little or no limitation of straight leg raising. However, neurological signs may be present in one or both lower limbs sugges-

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FIGURE 2.- Lateral projectionsof lowerlumbarvertebrae showing narrowing of the intervertebral foramen: A. Normal B. Subluxation secondary to disc degeneration C. Osteoarthrosis of the apophyseal joints D. Intervertebral disc protrusion.

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FIGURE 3A FIGURE 3. -Degenerative spondylosis with disc prolapse. The gross narrowing of the subarachnoid space opposite the intervertebral discs is clearly shown in both. A. Postero-anterior, and B. Lateral views. History of back and left thigh pain, worse on working. Left thigh paraesthesiae. Male 63 Years.

tive of root compression. Vascular changes are not seen. If the patient is exercised by the examiner and taken to the point of pain, weakness can always be demonstrated in the more affected leg, and this weakness disappears very rapidly when the patient is allowed to rest. In the clinical examination of the patient with vascular disease there is usually evidence of trophic signs in the lower limb coupled with an abnormal vascular tree. Problems may occur in diagnosis when spinal canal stenosis coexists with vascular disease and Australasian Radiology. Vol. XXIII, No. 1, March, 1979

LUMBAR SPINAL CANAL STENOSIS

FIGURE 3 8

Dyck (1977) describes a patient needing both to the formation of a lateral recess or sulcus in aortic and spinal surgery for relief of combined which the roots are compressed. The diameter of the intervertebral foramen is lessened either by symptoms. Verbiest (1976) has discussed the origins and encroachment posteriorly by degenerative change semantics of the word “stenosis” and has distin- in the posterior joint or by subluxation of that guished in the surgical sense the difference between joint due to disc narrowing. The foramen may be transport and compressive stenosis. Spinal stenosis lessened in size anteriorly either by a disc prolapse is truly compressive and disturbances of circula- or osteophytes in relation to the intervertebral tion of blood and cerebro-spinal fluid are secondary disc (Figure 2). The pain of spinal canal stenosis effects. The compression may affect the nerve is regarded as a compressive effect on the small roots of the cauda equina within the vertebral vessels in and around the nerve roots and this canal or the nerve roots in the neural foramina. compression is worsened during exercise, or by The normal lumbar vertebral canal is triangular further narrowing of the spinal canal in the erect in cross-section and in stenotic conditions both the and, therefore, extended position of the spine. midpagittd and the interpedicular diameters may It has been suggested (Blau and Logue) that be lessened by true bony narrowing, encroachment exercise mcreases the vascular supply of the nerve by the degenerative effects of the disc or of the roots, but the exact causation of this is not underposterior joints (Figure 1). In extension of the stood. Although the diagnosis and decision to lumbar spine there is a slight decrease in the volume operate on patients with spinal canal stenosis is of the spinal canal mainly due to a shortening of often made on clinical grounds, radiological the canal and slight disc protrusion at all levels examination can give valuable corroborative (Nelson 1973). This volume change is of signifi- evidence of the presence of the stenosis, and in cance in explaining the onset of symptoms when particular define its extent. The following investistanding and in myelographic interpretation (vide gations are of value. infra)

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The sagittal narrowing of the spinal canal is often greatest laterally, beneath the facets, leading Australasian Radiology, VoI. XXlI19No. 1. March. 1979

1. Plain radiography of the lumbar spine

This will show degenerative changes including

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P.DEWEY AND P. SOUTHWELL

FIGURE 4 B FIGURE 4 A FIGURE 4.- Degenerative disc disease (male, 64 years) with extradural block at L3-4 level Compressed nerve roots are clearly seen in: A. Postero-anterior view B. Lateral view. History of pain in right lower limb, sudden onset after walking 200 yards, relieved by sitting. Dragged right foot on walking.

narrowing of the intervertebral foramina and perhaps facet subluxation. Lumbar spinal stenosis is typically associated with sagittal narrowing of the vertebral canal, short pedicles, large apophyseal joints, thickened ligamenta flava, protruding discs, marginal osteophytes and sometimes a decreased interpedicular distance. Measurement of the vertebral canal can be performed from radiographs, but the posterior limit of the can4 is not easily identified as a rule even if tomography is employed. Jones and Thomson (1968) compared the product of the 64

antero-posterior and lateral measurements of the canal with the product of the antero-posterior and lateral measurements of the vertebral body, expressing the result as a ratio. The ratio of 1 : 2.5 indicates a large canal, while 1 : 6 indicates a narrow canal in relation to the size of the body. The normal range is 1 : 2 to 1 : 4.5. Verbiest (1976) states that true interpedicular distances of 17mm or less and true mid-sagittal distances of 12mm or less are too short and demonstrate the presence of stenosis. Eisenstein (1977) measured 2166 vertebrae from 433 spines. He concluded that minimal radiographic measurements of the vertebral canal are mid-sagittal 1Smm and interpedicular 20mm. His method of measuring the mid-sagittal diameter of the canal is useful and can be applied from L1 to L4. Briefly it comprises drawing a line joining the tips of the superior and inferior articular processes of a particular vertebra and measuring Australasian Radiology, Vol. XXIII, No. 1 , March, 19 79

LUMBAR SPINAL CANAL STENOSIS the distance between that line and the posterior surface of the body.

2. Lumbar rnyelography The narrowing of the subarachnoid space can be demonstrated by myelography (Figures 3 , 4 , 5). An extradural block (Figure 4) is often found, associated with thickened nerve roots (Blau and Logue). Blockage may be present in spinal extension, relieved by spinal flexion (Newman 1973). The impressions of enlarged articular facets and prolapsed intervertebral discs may be seen. Technical difficulties may be encountered because of the shallowness of the subarachnoid space and cisternal puncture may be needed for the injection of the contrast. The cerebro-spinal fluid should be submitted for laboratory examination and in 50% of cases the protein level will be markedly raised (Dyck et a1 1977). 3. Cornputerised axial tomography It is now possible to show the spine in crosssection giving a more direct means ofdemonstrating vertebral canal stenosis (Hammerschlag et al 1976). TREATMENT The recognised treatment of stenotic lesions of the lumbar spine is adequate decompression of the affected area, including, if necessary, wide opening of of the poste,.ior joints the intervertebral foramen in its entire extent. Results of these operations are usually gratifying and give relief of the symptoms and in particular greatly increase the patient’s exercise tolerance.

DISCUSSION Not one symptom is diagnostic in spinal canal stenosis. The two main presentations are cauda equina claudication and unremitting back pain and sciatica (Schatzker and Pennal 1968). The claudication is frequently bilateral while the sciatica is usually worse on one side. A wide range of stenotic syndromes exists (Mutton et a1 1975): 1 . Activity claudicatisn. 2. Postural pain and paraesthesia. 3. Continuous pain and paraesthesia. 4. Progressive paraparesis. Over a period of time the clinical features vary and change from one syndrome to another. Spontaneous remission of severe symptoms is also possible, probably attributable to resolution of inflammatory processes in the peri-articular Australasian Radiology, Vol. XXIII,

No. I , March. 1979

FIGURE S . - M A ~42 years - marked narrowing of the subarachnoid space at the level of the spondylotisthesis. History of low back pain on working with recent onset of bilateral leg pain on walking.

tissues or the apophyseal joints. Because of the diversity of symptoms and signs and uncertainty about the exact pathogenesis, various names have been given to the condition, for example spondylotic caudal radiculopathy, cauda equina claudication and neurogenic intermittent claudication. The term “spinal canal stenosis” is popular in the orthopaedic literature. The degree of narrowing of the vertebral canal can be difficult to assess for two main reasons. The posterior landmarks for the sagittal measurement are not easily identified and there is lack of universal agreement about how the measurement of the canal should be made and which results indicate significant stenosis. Eisenstein regards direct measurement on radiographs as more reliable than the ratio of Jones and Thomson (1968). In his series of 2166 vertebrae, Eisenstein found that using the spinal ratio, 1 1 % were stenotic - an unduly high percentage in an unselected

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P. DEWEY AND P. SOUTHWELL group of spines. He, therefore, doubts the validity of the ratio. Despite this, the ratio has a popular application in identifying patients likely to suffer from spinal stenotic syndromes once degenerative processes develop. In 100 patients undergoing myelography (Williams1975) and in 100 patients with intervertebral disc prolapse requiring surgery (Ramani 1976), a large proportion of each series had narrow vertebral canals according to the ratio of Jones and Thomson. As the number of elderly individuals in the community increases, spinal stenotic syndromes (and arterial insufficiency)become more common.

StTMMARY Lumbar spinal stenosis is an important condition which has not been fully appreciated in the past. The diagnosis is largely clinical but radiology can materially assist its assessment. The condition often requires wide surgical decompression which produces a high rate of symptomatic relief. Intermittent claudication is a relatively common symptom in spinal canal stenosis and a careful clinical appraisal is required to distinguish it from daudication of arterial insufficiency. ACKNOWLEDGEMENT

We are grateful for the assistance of the Department of Medical Illustration of Royal North Shore Hospital, Sydney. REFERENCES Amoldi, C. C. and twenty coauthors (1976): “Lumbar Spinal Stenads and Nerve Root Entrapment Syn-

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dromes Defdion and Classification.” Clin. Orthow e d . and ReL Re& 1 15 :4-5. Blau, J. N. and Logue, V. (1961): “Intermittent Claudication of the Cauda Equin;t” Lancet, 1 : 1081-1086. Dyck, P., Pheasant, H. C., Doyle, 1. B. and R i d er , J. J. (1977): “Intermittent Cauda E q h Compression Syndrome.” Spine, 2 (1) :75-8 1. Eisenstein, S . (1977): “The Morphology and Pathological Anatomy of the Lumbar Spine in South African Negroes and Caucasoids with Specific Reference to Spinal Stenosir” J. Bone Joint Surg. 59 (B) : 173-180. Hammerschlag, S. B., Wolpert, S . M. and Carter, B. L. (1976): “Computer Tomography of the Spinal Canal.” Radiology, 121 : 361-367. Jones, R. A. C. and Thomson, J. L. (1968): “The Narrow Lumbar Canal.“ J. Bone Joint Surg. 50 (B) :595405. Mutton, G. R. V., Taylor, T. K. F. and Nade, S. M. L. (1975): “Stenotic Syndromes of the Lower Lumbar Spine.”J. Bone Joint Sue. 57 (B) : 251. Nelson, M. A. (1973): “Lumbar Spinal Stenosis.”J. Bone Joint SWg. 55 (B) :506-512. Newman, P. H. (1973): “Surgical Treatment for Derangement of the Lumbar Spine.” J. Bone Joinr Surg. 55 (B) : 7-19. Ramani, P. S. (1976): “Variation in Size of the Bony Lumbar Canal in Patients with Prolapse of Lumbar Intervertebral Discs.” Clin. Radiol. 27 : 301-307. Schatzker, J. and Pennal, G. F. (1968): “Spinal Stenosis, a Cause of Cauda mu i n a Compression.” J. Bone Joint Surg. 50 (B) :606418. Verbiest, H. (1954): “A Radicular Syndrome from Developmental Narrowing of the Lumbar Vertebral Canal.” J. Bone Joint Surg. 36 (B) : 230-237. Verbiest, H. (1976): “Fallacies in the Present Definition, Nomenclature and Classifcation of the Stenoses of the Lumbar Vertebral Canal.” Spine, 1 (4) : 217-225. Williams,R. (1975): ‘The Narrow Lumbar Spinal Canal.” Aust. Rodwl. I 9 : 356-360.

Australasian Radiology, Vol. XXIII, No. I , March, 1979

Lumbar spinal canal stenosis.

Aust. Radiol. (1979),23,61 Lumbar Spinal Canal StenosiS PETER DEWEY, F.R.C.S. Orthopedic Surgeon, Wagga Wagga Base Hospital. PHILIP SOUTHWELL, DD.R.(...
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