X-Ray parameters of lumbar spine

3_xs_2_eKnowledge of anatomic spinal structures, especially its relation- ship to the functions performed, is necessary to form a correct diagnosis. The anatomical structure of the vertebrae varies de- pending on the level of the spinal segment. Normal anatomical parameters, derived from bone structures of the spine, are roughly determined by X-ray method.

This paper presents the results of the survey radiography of the lumbar spine in a straight line and lateral projections in 30 individ- uals without pathology spine, aged 21-60 years with frequently observed lumbar spinal stenosis stenosis. Applying X-ray method there were studied shape, height, and the contours of the vertebral bodies and intervertebral disc in the front (interpedicular) and sagittal planes; there were measured dimensions of the lumbar canal and foramen holes in the same planes. Using X-ray method can fully identify the bone parameters of vertebral column. How- ever, the informativity of the method depends on knowledge of radiologist about topographic anatomical features of spine.

Keywords: Radiology, X-ray, CT and MRI, intracanal ligament device, lumbar spinal stenosis

Introduction

Understanding the anatomy of the lumbar spine, especially in connection with its func- tion, is necessary to form a correct diagnosis, choose the best and most efficient way of treatment (Gelli, Speight, and Simon, 2003; Tager and Mazo, 1983; Truumees, 2005).

Each spinal segment is composed of the vertebral body, the arc with two wide legs, flat plates, spinous process, and the intervertebral disc. They all together make up the ring, and form the spinal canal with all the soft tissue content, which for various reasons may be subject to compression. The normal anatomic parameters of bone structures of the spine can be determined by X-ray. Survey radiography of direct and lateral projections, due to the high information content remains an important diagnostic method of vertebrology, widely available and relatively inexpensive, having high spatial resolution (Zubarev, 2003; Reiser, Baur-Melnyk, and Glacerie, 2011; Lohman, Tallroth, Kettunen, and Lindgren, 2006; Modic and Ross, 2007).

Purpose of study was to determine the significance of the X-ray method to establish the anatomical dimensions of the lumbar bone structures of the spine.

Material and methods

Radiographic examination was performed for the lumbar spine in direct and lateral projec- tions in 30 individuals without spine pathology in the age of 21-60 years, who often had lumbar spinal stenosis. With X-ray method we determined the shape, height and body contours of spine and the intervertebral disc (IVD) in the frontal and sagittal planes. In addition, we measured the size of the spinal canal and foramens in the same planes.

Through the survey radiography of the lumbar spine in a frontal and lateral projections, as noted in Table 1, we measured: the vertical size of the vertebral bodies and left and right contours of the intervertebral disc in frontal projection; the vertical size of the vertebral body and the IVD on the ventral and dorsal projections; frontal and sagittal size of the vertebral bodies on the top and bottom contours; interpedicular (frontal) distance in the spinal canal (corresponding to the largest frontal size of spinal canal); mid-sagittal diameter of the spinal canal by Hinck (the shortest distance between the rear surface of the ver- tebral bodies and the inner surface of the arc at the base of the spinous process); and the size of foraminal openings by Epstein (its front wall — the rear surface of the body overly- ing vertebra, the posterior wall — the head of superior articular process underlying verte- bra).

table3

In addition we identified the vertebral-disc ratio (according to the literature the rate of 4:1 or 5:1, depending on the level of the spinal column), channel-corporal Johnson- Thompson index (the ratio of the size of the sagittal spinal canal to the sagittal size of the vertebral bodies at the same level), which retained its importance until recent years for the diagnosis of spinal stenosis (synonym: cervical index, Pavlova and Tchaikovsky’s index). The index is individual for each vertebral segment, and used for the cervical spine.

Results and discussion

Taking advantage of X-ray survey of forward and lateral projections can be sufficient to fully appreciate the bone-component parameters of the lumbar spine. As noted in Table 1, the vertical sizes of the vertebral body in a straight projection on the left and right con- tours and in the lateral projection of ventral and dorsal contours of L1 to L5 have little difference (P <0.8 or P> 0.8). This trend is observed when measuring the vertical size of the IVD on the right and left contours. However, the vertical sizes of the IVD of ventral and dorsal contours have quite a large difference (P<0.05), i.e. IVD in the ventral part has a significantly greater thickness than in the dorsal part, because of the physiological lordosis.

The horizontal dimensions of the vertebral bodies on the upper and lower contours of the line and the lateral projection (P<0.8) as well as vertical dimensions of the vertebral bodies (P<0.2) differ slightly from each another. Typically, the lower contour of each lumbar ver- tebra is wider than the top, but with a slight difference (P<0.8).

Interpedicular (frontal) distance and mid-sagittal diameter of the spinal canal expand in the craniocaudal direction and change their shape. Instead of a dome-shape in the upper lum- bar part, the vertebral canal takes at the L5 the shape of a trefoil. In this, interpedicular distance is wider by 35% than the diameter of mid-sagittal at L1. This difference reaches 52% at L5 level, 39% — at L2, 42% — at L3, and 47% — at L4. Expansion of the channel in the caudal direction is highly significant (P<0.001). However, the measured values of the size of foraminal holes from L1 to L5 remain stable (Table 1).

Normal vertebral-disc ratio and channel-corporal index of lumbar vertebral segment in our observations differ notably than the ones in studies of European authors (Ulrih and Mushkin, 2004; Suri, Rainville, Kalichman, and Katz, 2010). In contrast to European data (4:1 or 5:1) vertebral-disc ratio for the lumbar vertebrae in the caudal direction is in range from 3.35:1 to 2.76:1 (Table 2). This low ratio can be explained by the low growth in our patients which is in average 168±6 cm. Channel-corporal index, according to the literature (Ulrih and Mushkin, 2004; Mutch and Hadlow, 2002), is defined only for the cervical ver- tebrae, normally it is above 1.0. This index in range from 0.8 to 1.0 corresponds to sub compensation stenosis, with the less than 0.8 value — to decompensation spinal stenosis in the cervical region.

According to our data, the so-called Johnson-Thompson index (ratio of the size of the sagittal spinal canal to the sagittal vertebral body size) from the first through fifth lumbar vertebral segment is in the range from 1:1.88 to 1:1.74 to the level of lumbar vertebra; i.e. above 1.0. In addition, we determined the frontal index size: the ratio of frontal spinal canal size to the frontal size of vertebral body at L1-L5. This ratio is in the range from 1:1.82 to 1:1.7, i.e. above 1.0 as well. The left and right contours of the vertebral bodies from L1 to L5 vertically are extended up to 16%, and ventral and dorsal contours of the vertebral bodies are lengthened to only 5%. On the left and right contours the IVD from L1 to L5 is vertically extended up to 32%, and in ventral and dorsal contours it extended up to 37%. Horizontal size (wheel size) of the vertebral bodies on the top and bottom contour line projections are extended up to 16%, and this size (sagittal dimension) in the lateral projection is extended only to 3%. Interpedicular (frontal) distance is extended to 25%, and the sagittal diameter of the medium is increased to 11%. Dimensions of foraminal openings from L1 to L5 are not expanded.

Thus, the vertical size of the vertebral body contour in craniocaudal direction is slightly lengthened (P<0.8) in contrast to the IVD, which ventero-dorsal difference is reliable due to physiologic lordosis (P<0.05). The bottom contour of each successive lumbar vertebra is wider than the overlying one, though with a slight difference (P<0.8). Medullar canal of the lumbar in the cranio-caudal direction significantly (P<0.01) expands with increasing distance; in this the interpediсular distance expands more (up to 24%) than the mid- sagittal diameter (up to 11%).

table4

Dimensions of foraminal openings from L1 to L5 are almost not changed. Because of the relatively low height (168±6 cm) of our patients, the spinal-disc ratio was low (3.35:1- 2.76:1) than in the European data (4:1 or 5:1). Channel-corporal index for the lumbar spine is above 1.0 (from 1:1.88 to 1:1.74), i.e. value of the index is at the level of European data. Relation to the body of the channel is similar to the lumbar vertebrae of the cervical, i.e. channel-corporal index throughout spine has equal value.

Survey radiography, due to fairly high information, remains as an important and widely available diagnostic method in vertebrology. Normal X-ray parameters of bone structures will be the spine-border orientations to identify lumbar spinal stenosis.

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OTABEK ABLYAZOV

Faculty of Medical Radiology Tashkent University of

Postgraduate Medical Education, Uzbekistan