Computed tomographic evaluation of lumbar spinal structures during ...

Physiotherapy Theory and Practice, 21(1):311, 2005 Copyright # Taylor & Francis Inc. ISSN: 0959-3985 print/1521-0510 online DOI: 10.1080/09593980590911507

Computed tomographic evaluation of lumbar spinal structures during traction ¨ lku¨ Akarırmak, MD,2 Ilhan Karacan, MD,1 Hidayet Sarı, MD,1 U and Haluk Akman, MD3 1

Department of Physical Medicine and Rehabilitation, Medical Faculty of Cerrahpasa, Istanbul University, Istanbul, Turkey 2 Department of Physical Medicine and Rehabilitation, Medical Faculty of Cerrahpasa, Istanbul University, Istanbul, Turkey. E-mail: [email protected] 3 Department of Radiodiagnostic, Medical Faculty of Cerrahpasa, Istanbul University, Istanbul, Turkey

In the previous studies, it is reported that traction diminishes the compressive load on intervertebral discs, reduces herniation, stretches lumbar spinal muscle and ligaments, decreases muscle spasm, and widens intervertebral foramina. The aim of this study was to evaluate the effects of horizontal motorized static traction on spinal anatomic structures (herniated area, spinal canal area, intervertebral disc heights, neural foraminal diameter, and m.psoas diameter) by quantitative measures in patients with lumbar disc herniation (LDH). At the same time the effect of traction in different localizations (median and posterolateral herniation) and at different levels (L4-L5 and L5-S1) was assessed. Thirty two patients with acute LDH participated in the study. A special traction system was used to apply horizontally-motorized static lumbar traction. Before and during traction a CT- scan was made to observe the changes in the area of spinal canal and herniated disc material, in the width of neural foramina, intervertebral disc heights, and in the thickness of psoas muscle. During traction, the area of protruded disc area, and the thickness of psoas muscle decreased 24.5% (p ¼ 0:0001), and 5.7% (p ¼ 0:0001), respectively. The area of the spinal canal and the width of the neural foramen increased 21.6% (p ¼ 0:0001) and 26.7% (p ¼ 0:0001), respectively. The anterior intervertebral disc height remained unchanged with traction however the posterior intervertebral disc height was significantly expanded. This study is the first to evaluated in detail and quantitatively the effect of motorized horizontal lumbar spinal traction on spinal structures and herniated area. According to detailed measures it was concluded that during traction of individuals with acute LDH there was a reduction of the size of the herniation, increased space within the spinal canal, widening of the neural foramina, and decreased thickness of the psoas muscle. dysfunction (Bogduk, 1991; Bohannon and Gajdosik, 1987; Garfin, Rydevik, and Brown, 1991; Kra¨mer, 1990; Takahashi, Yabuki, Aoki, and Kikuchi, 2003). Traction is one of the physical modalities widely used for the treatment of lumbar disc herniation (LDH; Kra¨mer, 1990; Geiringer, Kincaid, and Rechtien, 1993; Hinterbuchner,

Introduction In lumbar disc herniation by disruption of the intervertebral disc, mechanical nerve root compression or chemical irritation of nerve root due to leakage of disc content are the result. Mechanical compression or chemical irritation of the nerve root cause inflammation and nerve Accepted for Publication 25 June 2004.

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Sarı et al./Physiotherapy Theory and Practice 21 (2005) 311

1985). It is reported that traction diminishes the compressive load on intervertebral discs, apophyseal joints, causes a flattening of the lumbar lordosis, stretches lumbar spinal muscle and ligaments, decreases muscle spasm, widens intervertebral foramina and apophyseal joint spaces and relieves low back pain (Beurskens et al, 1995; Caillet, 1981; Gu¨venol, Tu¨zu¨n, Peker, and Go¨ktay, 2000; Lehmann and Brunner, 1958; Letchuman and Deusinger, 1993; Mathews, 1972; Neuwirth, Hilde, and Champbell, 1952; Revel, 2000). Protruded disc material pressures on the ligamentum longitudinale posterior, neural and vascular elements in patients with LDH. Static lumbar traction reduces the volume of the herniated disc material, as has been shown by discogram, myelogram and computed tomography (CT; Gupta and Ramarad, 1978; Mathews, 1972; Onel, Tuzlacı, Sarı, and Demir, 1989). The aim of this study was to evaluate the effects of horizontal motorized static traction on spinal anatomic structures (herniated area, spinal canal area, intervertebral disc heights, and neural foraminal diameter) by quantitative measures in patients with lumbar disc herniation (LDH). At the same time the effect of traction in different localizations (median and posterolateral herniation) and at different levels (L4-L5 and L5-S1) was assessed.

Method Thirty two consecutive patients with lumbar disc herniation were included into the study. They were required to fulfill the relevant inclusion and exclusion criteria in Table 1 and be willing to participate. The study was approved by Local Ethical Committee. Informed consent prior to the study was signed by all participants. In all patients’ superficial sensation (at L2, L3, L4, L5, S1, and S2 dermatomes) was evaluated. Muscle strength (hip flexors, knee extensors, ankle dorsiflexors and plantar flexors) was evaluated by manual muscle testing. Deep tendon reflexes (patella and Achilles) as well as the Babinsky reflex were assessed. A positive straight leg raise was recorded if the range was between 30 and 70 degrees of hip flexion. Horizontally-motorized static lumbar traction: A special traction system named C Experimental

Lumbar Traction ModelTM was designed by the authors. The system consisted of a traction machine (True trac TT 92 B, California, USA), a pelvic and chest belt, a traction board 250 cm long and 60 cm wide), a moving board (120 cm long and 60 cm wide) and five wood rolls of 2 cm diameter which had been placed between the two boards in order to decrease friction during traction. The traction boards were designed as narrow as possible, to fit the gantry of the CT-scan. All materials were wooden and translucent to x-rays. To optimize the treatment of the affected areas, all patients lay supine on the moving board with legs in semiflexion (hip joints in 45 degrees of flexion and knee joints in 45 degrees of flexion) and they were centralized in the gantry (Figure 1). A wooden padded foot stool was placed under the patient’s calf in order to relax paravertebral muscles, decrease the lumbar lordosis and increase effectiveness of traction. CT was performed on a CT 800-W (Hitachi, Japan) with a slice thickness of 3 millimeter. Resolution of this system was 0.17 mm=pixel. Axial CT scan were made aligned parallel to the vertebral end plate between the lower border of the upper pedicle to upper border of the lower pedicle at the level of herniated disc. Before traction lateral topogram and axial cross sections were taken while the patient was placed on the traction table with traction belts applied. Spinal measurements were performed with the help of a computer program. Horizontally-motorized static lumbar traction was applied, by using a distraction force of 45 kg, for twenty mifnutes. A second lateral topogram and axial slices were taken in the twentieth minute of traction. At the end of traction initial measurements were repeated. Reformatting with sagittal and coronal reconstruction was used in each case. Topogramic evaluation and reformatting proved that the sections before and during traction were taken from the same sections and angles (parallel to the end plates). The area of herniated disc material, spinal canal area, length of vertebral column, thickness of both the psoas muscle, width of intervertebral disc space, and anteroposterior width of neural foramina were measured from CT sectional images before and at the 20th minute of traction. All measurements were performed on the sectional area on which the


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Table 1. Inclusion and exclusion criteria.

Inclusion criteria

Exclusion criteria

Age: 1855 years Acute lumbar disc herniation (14 weeks) Median or posterolateral herniation

Chronic lumbar disc herniation and degeneration Spinal surgery Extruded, sequestred, and far lateral disc herniation Severe motor deficits (muscle strength 3=5) Cauda-equina syndrome Hypertension Diabetes mellitus Obesity Seronegative spondylo-arthropathies Hypermobility syndrome

spinal anatomic structures could best be seen. Measurements were collected on a single scan by a reviewer who was not blinded to the conditions. The contour of the measured structures was made more clearly visible by changing the contrast of the computer screen. Protrusion was defined as a clearly contoured herniated disc material with its base placed on

the posterior border of the intervertebral disc (Kra¨mer, 1990). Herniated area was accepted to be the area between the base of protrusion and the border of the herniated disc. Spinal canal area was measured between the posterior border of the intervertebral disc and the anterior border of both ligamentum flavum. Measurements were made by computer (Figure 2).

Figure 1. Positioning of the patient on the traction boards (Cerrahpasa Experimental Lumbar Traction Model) and gantry of the CT-scanner before and during traction administration. The pelvic belt is attached to traction device with flexion of the hips and knees to insure lumbar lordosis flattenning during traction.

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Figure 2. Spinal structures evaluated by CT.

Herniations were defined as median or posterolateral disc herniations. When the apex of the herniated mass was near to the central line of the spinal canal this type of herniation was called median herniation. When the apex of the herniated mass was near to the neural foramen, this type of herniation was called posterolateral disc herniation.

Data analysis Descriptive statistics (mean, standard deviation, frequency) of the data were computed. Measured values of the spinal structures before and during traction were compared with paired t and Wilcoxon test. The Mann-Whitney U test was used to analyze the statistical difference of

Figure 3. CT-scan before traction, showing the median disc herniation at L4-L5. It can be seen that the herniated nuclear material invades the spinal canal and left neural foramina and, compresses the dural sack and L5 nerve root. Spinal canal area and neural foramina are narrowed.


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Figure 4. CT-scan during traction using 45 kg of force. Regression of the nuclear material from the discal space and neural foramina can be seen. Neural foraminal diameter and spinal canal area are increased.

the area of herniated disc material between the patients with L4-L5 LDH and L5-S1 LDH. The level of significance was set a priori at an alpha level of 0.05 for all test. The intraobserver error was calculated by redrawing and remeasuring the intervertebral disc space heights a second time in ten patients. Intraobserver error was calculated as ðRðx1 x2 Þ2 =2nÞ1=2 , where x1 is the first measurement, x2 is the second measurement, n is the number

of differences (i.e., pairs of measurements). All analyses were completed with SPSS version 10.0 for Windows.

Results Eleven women (34.4%) and 21 men (65.6%) participated in the study, with a mean age of 36 8:6 years (range 1855), mean height of

Table 2. The effect of the traction on herniation area and according to the localization of the herniation (mm2).

Herniation area Median Posterolateral Total (32)

Before traction

After traction

Rate of reduction (%)

p value

95:8 53:8 115:1 56:6 103:3 58:2

72:6 45:6 82:6 55:2 77:9 49:7

26.9 18.6 24.5

0.0001 0.009 0.0001

Table 3. The effect of traction herniation area (mm2) for levels L4=5 and L5=S1.

Side L4-L5 L5-S1

Before traction

After traction

Rate of reduction (%)

p-value

98 48:5 115:9 86:0

70:6 31:5 100:74 86:8

29 13.1

0.0001 0.028

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Table 4. Expansion of anterior and posterior disc height before and after traction (mm).

Anterior intervertebral disc height

L1-L2 L2-L3 L3-L4 L4-L5 L5-S1

Posterior intervertebral disc height

Before traction

During traction

p value

Before traction

During traction

p value

9:0 1:8 10:4 1:7 10:9 2:3 11:9 3:0 12:7 2:8

9:2 1:7 10:1 1:5 10:8 2:3 11:9 2:7 13:0 3:1

> 0:05 > 0:05 > 0:05 > 0:05 > 0:05

6:0 1:6 6:7 2:0 7:7 2:3 7:9 2:1 6:3 1:8

6:7 1:8 7:6 1:8 8:8 2:0 9:2 1:8 8:0 2:1

0.008 0.001 0.001 0.001 0.001

171:1 7:0 cm (range 160178 cm) and mean weight of 73:5 10:7 kg (6085 kg). All herniations were protruded type. Twenty seven of 32 patients (84.4%) had a L4-L5 and 5 patients (15.6%) a L5-S1 disc herniation. Localizations were 23 median and 9 posterolateral herniation. At baseline the area of protruded disc material was 103:3 58:2 mm2. During traction it decreased to 77:9 49:7 mm2 (24.5%; paired t test, p ¼ 0:0001) (Figures 3 and 4). The reduction was more prominent in median than in posterolateral protrusions, but there was no significant difference between groups (Wilcoxon test, p > 0:05; Table 2). The reduction was more prominent at L4-L5 level than at L5-S1, but there was no significant difference between groups (Mann-Whitney U test, p > 0:05; Table 3). The anterior intervertebral disc height remained unchanged with traction however the posterior intervertebral disc height was significantly expanded (Table 4). During traction an average of 3:3 1:9 mm (1.9%) expansion of the lumbar column length was measured ( p ¼ 0:0001; Table 5). During traction the area of the spinal canal, and the width of the neural foramen increased 21.6%, and 26.7% respectively (Figures 3, 4, 5, and 6). Thickness of psoas muscle was reduced 5.7% (Table 5).

The intraobserver error was found to be 0:39 millimeter.

Discussion Traction has been used widely for the treatment of lumbar disc herniation (Kra¨mer, 1990; Geiringer, Kincaid, and Rechtien, 1993; Hinterbuchner, 1985). Traction has been reported to be effective in acute LDH patients (Krause, Refshauge, Dessen, and Boland, 2000). In this study, we were able to demonstrate a reduction in herniated disc area, widening of anteroposterior diameter of neural foramina, expansion of posterior intervertebral disc height and thinning of psoas muscles. We found a significant increase in the height of the posterior intervertebral disc while the anterior disc remained unchanged. This result could be explained by the patient position and traction angle. Patients were placed in supine position in order to decrease paravertebral muscle spasm and lumbar lordosis, with hips and knees in semiflexion. Traction forces were applied at a 20-degree angle from the traction board. It has been reported that traction forces are especially effective on posterior elements of

Table 5. Effect of traction on the other anatomic structures of the spine.

L1-S1 spinal length Spinal canal area Neural foramen diameter Psoas muscle thickness

Before traction

After traction

Rate of difference (%)

p value

174:6 12:8 mm 175:4 70:4 mm2 2:8 1:3 mm 39:7 7:4 mm

177:9 12:8 mm 213 79:5 mm2 3:6 1:5 mm 37:4 8:2 mm

1.9 21.6 26.7 5:7

0.0001 0.0001 0.0001 0.0001


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Figure 5. CT-scan taken before traction; demonstrating neural foraminal diameter narrowing. Right neural foraminal diameter (A-B) is 3.4 mm, left neural foraminal diameter (C-D) 3.7 mm.

Figure 6. CT scan during traction, demonstrating an increase in neural foramina diameter. Right neural foraminal diameter (A-B) is 5.0 mm. Left neural foraminal diameter (C-D) is 4.9 mm.

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the spinal vertebral column. Traction forces combined with axial distraction create a flexion moment (Lee and Evans, 2001), if the axis of rotation is through the vertebral body it will have a greater traction effect on the posterior than anterior vertebral elements. Widening of spinal canal area and neural foraminal diameter were results of this study, which can be explained by lumbar flexion. Some biomechanical investigations have determined that spinal canal and neural foraminal space is increased during flexion and reduced during extension (Cox, 1991). The results of our trial, showing posterior intervertebral disc space (expansion) while anterior disc space was unchanged also denotes a relative lumbar flexion. Radicular symptoms due to lumbar disc herniation are explained by compression of nerve root by herniated material and=or chemical irritation. As a result of mechanical compression on nerve root the circulation of vasa nervorum is disturbed. Therefore intravascular hydrostatic pressure is increased and perineural edema is formed (Bogduk, 1991; Bohannon and Gajdosik, 1987; Garfin, Rydevik, and Brown, 1991; Kra¨mer, 1990; Takahashi, Yabuki, Aoki, and Kikuchi, 2003). We demonstrated a reduction of herniated disc area by 25%, an increase by 22% of the spinal canal area and a widening by 27% of the neural foraminal sagittal diameter during traction in this study. As a result, direct compression of herniated disc material on the spinal nerve root diminished. Simultaneously, an increase in the spinal canal area and widening of the neural foramen contributed to relieve the spinal nerve root. The reduction of herniated disc material during traction can be explained by two different mechanisms: 1) Stretching of the posterior longitudinal ligament (PLL) and 2) A decrease in intradiscal pressure (Cyriax and Cyriax, 1985; DeSe´ze and Levernieux, 1950; Nachemson and Elfstrom, 1970). Measurement of these two factors were beyond the scope of this study, but it is possible that these two mechanisms are the result of intervertebral disc spaces widening. The increase of spinal column length and widening of the posterior intervertebral disc space demonstrated in our study infer that traction may be effective because of these mechanisms. PLL is known to be strongest and thickest at the mid-sagittal line. Laterally towards the neural foramina the PLL becomes thinner

(Arey, 1977; DePalma and Rothman, 1970). It can be argued if stretching of the PLL is one mechanism by which herniations are reduced then this would be most effective for median herniations. The results of this study provide evidence for this theory as horizontal traction was more effective in reducing median compared with posterolateral herniations, however, this failed to reach significance. There are a number of muscles attaching to the lumbar spinal column, with different effects on the function of the spine. The psoas muscle was chosen for measurement because the contour of this muscle could be clearly outlined on CT scans. It was found that the psoas muscle diameter decreased during the traction. During traction there is significant increase in lumbar column length. This finding infers that during traction, lumbar spinal muscles stretch and lengthen. This effect can help to relieve paravertebral muscle spasm. The muscle spasm might improve with appropriately applied traction of adequate force (Cyriax and Cyriax, 1985). Given the large recent interest in the erector spinae—particularly multifidus—and their role in low back pain, this would be valuable. It may be of interest in future research to quantitatively determine the effects of traction on muscle spasm through cross-sectional measurement of various erector spinae muscles along with measures of myoelectric activity before, during, and after traction. There were some limitations to this study: 1) This was a cross-sectional study design utilizing one 20-minute session of traction. In clinical practice it is common for 1020 sessions of traction to be used for the treatment of a lumbar disc herniation. A longitudinal study evaluating the correlation between differences in spinal structures during traction both over different treatment sessions and also with clinical improvement would provide valuable information on the effects of lumbar traction in a clinical setting. 2) Another limitation is the lack of post-traction measurements, which could be addressed in a future study.

Conclusion This study was the first to show the detailed and quantitative effect of motorized lumbar traction on spinal anatomic structures and herniated area.


It can be concluded that during traction a reduction of herniated disc mass, the widening of both the spinal canal and neural foramina, contribute to this effect. Therefore if a disc herniation caused spinal nerve root compression, a decrease in the herniated disc material by traction may relieve mechanical pressure and pain. Experimental studies in which the effect of traction can be evaluated by manometric measurement of the pressure on the nerve root will be able to provide better understanding.

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