Effects of lumbar sagittal balance remodeling on natural absorption after lumbar disc herniation

Feng Wang, Guo-Gang Dai, Jiao Xia, Shi-Chuan Liao

Department of neck, shoulder, waist and leg pain, Sichuan orthopedic hospital, Chengdu, Sichuan, China

Keywords:

ABSTRACT

1. Introduction

Protrusion of lumbar intervertebral disc is a common spinal degenerative disease [1]. Ruptured lumbar disc herniation refers to the rupture of the fibrous annulus of the intervertebral disc, causing the nucleus pulposus to protrude and penetrate the posterior longitudinal ligament [2]. At present, the treatment of lumbar disc rupture is surgical treatment and conservative treatment. Conservative treatment mainly relieves patient-related symptoms through natural absorption after lumbar disc herniation. Related studies have shown that ruptured lumbar disc herniation is more easily absorbed naturally than non-ruptured lumbar disc herniation [3, 4]. Therefore, the natural absorption treatment of ruptured lumbar intervertebral disc process is receiving more and more attention.The spinal-pelvic sagittal curvature is the physiological curvature and shape of the sagittal plane of the human spine and pelvis during growth and development [5]. The spinal-pelvic sagittal curvature is evaluated by the pelvic incidence (PI), the sacral slope (SS), the pelvic tilting (PT), and the lumbar lordosis (LL) and so on. Since the sagittal curvature of each patient is different, its influence on the development of spinal disorders is also different. Related studies have shown that sagittal curvature parameters are closely related to lumbar degenerative diseases such as lumbar disc herniation [6]. In this study, we tried to explore the effect of sagittal balance remodeling on the natural absorption of patients with lumbar disc rupture and protrusion by comparing the differences in sagittal curvature parameters of patients with different prolapse of lumbar disc rupture and prognosis.

2. Materials and methods

2.1 General Information

From August 2016 to August 2017, 64 patients with ruptured lumbar disc herniation confirmed by MRI examination and treated with natural absorption were selected as the research subjects in our hospital. All patients were followed up for 2 years. Based on the size of the herniated discs after 2 years, the study subjects were divided into ruptured and protruded lumbar intervertebral disc reabsorption groups and non-reabsorption groups (group 0). The reabsorption group was divided into groups 1, groups 2, groups 3, and groups 4 according to the degree of absorption. There are 36 people in the reabsorption group, including 21 males and 15 females. Their average age is 41.8 ± 9.0 years, and their age range is 26 to 60 years. There were 28 persons in the non-reabsorption group, including 15 males and 13 females. Their average age is 40.2 ± 8.3 years, and their age range is 29 to 59 years. There was no significant difference in gender and age between the two groups (P＞ 0.05), which were comparable. This study was approved by the ethics committee of our hospital, and all patients signed the informed consent.

2.2 Inclusion and exclusion criteria

The inclusion criteria for the patients in this study were: (1) Patients who met the diagnosis of ruptured lumbar disc herniation according to the diagnostic criteria of "Surgery" [7]; (2) Age ranged from 18 to 60 years; (3) Consciousness, evaluation of MMSE scale indicates no dementia, no mental disorder, no serious heart, liver, kidney disease, hospitalized or outpatients who can cooperate with examination and treatment; (4) informed consent signed by the patient or by his immediate family; (5) Only one segment of the lumbar intervertebral disc has a ruptured protrusion, and the lesion segment is L4 / 5 or L5 / S1.

The exclusion criteria of this study are as follow: (1) multiple lumbar disc herniation, lumbar spondylolisthesis, lumbar degenerative scoliosis, developmental spinal stenosis, infection, fracture, osteoporosis, lumbar surgery history and obesity, claustrophobia; (2) Unclear consciousness, evaluation of MMSE scale indicates dementia, mental disorders and other diseases, patients who can not cooperate with the examination and treatment; (3) Patients with severe primary diseases such as cancer, heart, liver, kidney, and hematopoietic system; (4) Pregnant or lactating women; (5) those who can not complete the examination required by the research.

2.3 Instrument and equipment

The X-ray film adopts the Siemens DR system, and instructs the patient to stand naturally in the side position. The filming method uses small focus, small irradiation field, low kV and high millisecond projection. The imaging site includes the chest 12-hip joint.

MR scanning is conducted by Siemens 1.5T MR machine. Ask the patient to lie on his back with his legs extended. The spine coil is selected, and the L3 level is located at the center of the coil. The scan sequence includes: sagittal plane SE T1WI, TR535 ms, TE 15 ms; sagittal plane SE T2WI, TR 4500 ms, TE 128 ms; STIR TR 6300 ms, TE 15 ms, TI 160 ms. FOV 300 mm × 250 mm, layer thickness 3.5 mm, layer spacing 0.35 mm; axial position SE T2WI, TR 4500 ms, TE101 ms.

2.4 Observation indicators and observation nodes

Observation indicators: (1) Pelvic incidence angle (PI): The vertical line of the end plate is made through the middle point of S1 upper end plate, and the angle between the vertical line and the connection between the middle point of S1 upper end plate and the center of femoral head; If the two femoral heads do not overlap, take the midpoint of the central line of the two femoral heads as the center point. (2) Pelvic tilt (PT): the angle between the midpoint of the S1 end plate and the center of the femoral head and the vertical line. (3) Sacral angle (SS): the angle between the end plate and the horizontal line on S1. (4) Lumbar lordosis (LL): the angle between the end plate of S1 and the end plate of vertebral body of L1. The above indexes were detected by X-ray DR system at the time of patient enrollment and 2 years of follow-up, and results were calculated and compared.

The MR system was used to measure the size of the lumbar intervertebral disc tissue at the time of patient enrollment and after 2 years of follow-up. The measurement indicators included the sagittal diameter of the spinal canal and the sagittal plane. The inferior pedicle notch of the vertebral body is the second layer, and the notch from the lower boundary of the intervertebral disc to the next pedicle is the third layer. According to the changes of the protruded disc tissue in the area of the sagittal diameter of the spinal canal, the natural absorption of lumbar disc herniation was divided into 0 points, 1 point, 2 points, 3 points, and 4 points. In group 0, the sagittal diameter of the herniated disc tissue remained unchanged or increased, or the layer reached by the herniated disc increased by one or two levels; In group 1, the sagittal diameter of the herniated disc tissue decreased ＜ 25%, and the layer reached by the herniated disc tissue remained unchanged; In group 2, the sagittal diameter of the herniated disc tissue decreased between 25% and 50%; In group 3, the sagittal diameter of herniated disc decreased by more than 50%, or (and) the layer reached by herniated disc decreased by one or two levels; In group 4, the herniated disc disappeared, or only a few fibrous rings or cartilage nodules were left on the posterior edge of the vertebral body. Group 0 was classified as non-reabsorption group and group 1 to 4 as reabsorption group.

2.5 Statistical Analysis

In this study, spss22.0 statistical software was used for statistical analysis. The count data was evaluated by χ2test. The measurement data of the two groups, which was consistent with normal distribution, were compared using t test. Multiple groups of data were compared using analysis of variance for statistical analysis. Pairwise comparisons between multiple groups were performed using the LSD-t test. P ＜0.05 was used as the test standard with significant difference.

3. Results

3.1 Natural absorption of patients after lumbar disc rupture

Of the 64 patients in this study, 28 had no natural absorption (0 points) and 36 had natural absorption, including 9 cases with 1 point, 15 cases with 2 points, 7 cases with 3 points and 5 cases with 4 points. The reabsorption of the herniated lumbar disc is shown in Figure 1.

Figure 1 Reabsorption of ruptured lumbar disc

3.2 Comparison of PI changes between the two groups of patients

As shown in Table 1, there were no significant differences in the values of PI and PI during the entry and re-examination of different groups.

Table 1. Comparison of PI values in each score group between enrollment and reexamination.

3.3 Comparison of PT changes between the two groups of patients

As shown in Table 2, there was no significant difference in PT values between the two groups when they were enrolled; There was no significant difference in PT values between the two groups when they were re-examined, but the PT values in the reabsorption group showed a downward trend, and the PT changes in the reabsorption group were significantly lower than that in the non-reabsorption group.

Table 2. Comparison of PT values in each score group between enrollment and reexamination.

3.4 Comparison of SS changes between the two groups of patients

As shown in Table 3, there was no significant difference in the SS values between the two groups when they were enrolled and at the time of re-examination; At the time of re-examination, the SS values of the patients in the re-absorption group had an increasing trend, and the SS changes in the re-absorption group were significantly higher than those in the re-absorption group.

Table 3. Comparison of SS values in each score group between enrollment and reexamination.

3.5 Comparison of LL changes between the two groups of patients

As shown in Table 4, there was no significant difference in the LL values between the two groups when they were enrolled. At the time of re-examination, the LL value in the reabsorption group was significantly higher than that in the non-resorption group, and the LL change in the reabsorption group was significantly higher than that in the non-resorption group.

Table 4. Comparison of LL values in each score group between enrollment and reexamination.

3.6 Comparison of changes in PI, PT, SS and LL values of patients between the reabsorption group and the nonreabsorption group.

As shown in Figure 2, there was no significant difference in the value of PI in each group. As the scores increased, the values of PT, SS, and LL all gradually increased.

Figure 2 Comparison of changes in PI, PT, SS, and LL values in each group Note: P ＜0.05; a, compared with group 0; b, compared with group 1.

4. Discussion

It is generally believed that disc degenerative changes are mainly caused by increased disc pressure and genetic factors, as well as inflammatory reactions, and the causes of lumbar disc herniation are mainly physiological defects, injuries, and fatigue [8]. The intervertebral disc is squeezed, pulled or twisted from all directions, resulting in atrophy, weakened elasticity and corresponding clinical symptoms. At present, because some patients refuse to operate or have mild symptoms, most patients choose natural absorption treatment when treating lumbar disc herniation. And the related research confirmed that the ruptured lumbar disc herniation is easy to be naturally absorbed [3]. At present, doctors mostly take conservative treatment for the ruptured lumbar disc herniation.

During the growth and development of the human body, each person's sagittal curvature is different due to different physiological and external forces, and this difference easily causes changes in the spine-pelvic biomechanics [9]. PI refers to the angle between the midpoint of the center line of the bilateral femoral head and the midpoint of the metatarsal endplate and the perpendicular line of the metatarsal endplate [10]. At present, there are different opinions about the impact of PI on spondylolisthesis and other diseases. Some literatures believe that PI has an effect on the balance of thoracolumbar pelvic spine sagittal plane, and some studies believe that there is no effect [11, 12]. The results of this study showed that PI values of patients with ruptured lumbar disc herniation with different reabsorption levels were not significantly different before and after retreatment, suggesting that the value of PI did not affect the natural absorption of ruptured lumbar disc herniation.

PT and SS are two parameters that reflect the spatial orientation of the pelvis. PT and SS are posture parameters. When the human body changes its posture, PT and SS will have relative changes [13]. Related studies have shown that PT and SS and the ratio between them have an important effect on the spine-pelvic sagittal balance [14]. After adulthood, the human body needs to maintain the sagittal balance through changes in PT and SS equivalents [15]. In this study, the PT value of patients in the reabsorption group tended to decrease during the reexamination, and the change in PT value increased with the increase of the natural absorption score; The SS value of patients in the reabsorption group tended to increase during the re-examination, and the change in SS value also increased with the increase of the natural absorption score. This is similar to the findings of Hresk et al. [16], suggesting that the decrease in PT and the increase in the SS value of patients have an impact on the natural absorption of lumbar disc herniation.

LL refers to the curvature of the lumbar lordosis, which measures the angle between the S1 endplate and L1 endplate vertebral endplate line extending backward. Previous studies have shown that sagittal curvature indexes such as LL value had a predictive effect on lumbar degenerative spondylolisthesis. The LL value of patients with lumbar degenerative spondylolisthesis was significantly larger than that of the general population [17]. In this study, the LL value of patients in the reabsorption group increased significantly during the reexamination, while the LL value of the non-reabsorption group did not change significantly, and with the increase of the patient's score, the value of LL increased gradually. This suggested that the increase in LL value had an effect on the natural absorption of lumbar disc herniation. The more the LL value increased, the better the natural absorption of lumbar disc herniation was.

This study summarized the changes in PI, SS, PT, and LL values of each group. Except for the change in PI value, the changes in PT, SS, and LL value in each group showed a rising trend with the increase of the score. It showed that the changes of the above three indicators had an important impact on the natural absorption energy of patients with lumbar disc herniation. In summary, the PT, SS, and LL values of patients with natural absorption of lumbar disc herniation changed significantly before and after treatment. Changes in the sagittal balance index of the lumbar spine were important factors affecting the natural absorption of lumbar disc herniation.