Clinical features and imaging analysis of degenerative scoliosis Degenerative scoliosis (DS) is a new scoliosis that occurs after skeletal maturation accompanied by degenerative changes of the spine, with the exception of organic spinal lesions, such as trauma, tumors, infections, bone diseases, and progression of pre-existing scoliosis, etc. DS can lead to intractable low back pain and lower extremity radicular symptoms, and it is an important degenerative lumbar disease affecting the quality of life of the elderly. It is an important degenerative disease of the lumbar spine that affects the quality of life of the elderly. In recent years, there has been a gradual increase in the literature on DS both domestically and internationally, but the number of reported cases is relatively small. We analyzed and summarized the clinical characteristics of 139 cases of DS through retrospective study to explore the clinical characteristics of DS and the causes of nerve root compression. 1, Materials and methods 1.1 General information We retrospectively analyzed 139 cases of DS patients treated in our hospital since January 2003-May 2007, of which 46 cases were male and 93 cases were female, with a male-to-female sex ratio of 1:2.02; age 46-82 years old, average 64.5 years old, age composition:6.6% below 50 years old, 28.4% 51-60, and 65% above 60 years old. Inclusion criteria were: age >40 years, no previous history of scoliosis before skeletal maturity, no history of spinal fracture or spinal surgery; radiological evidence of coronal Cobb angle >10°, asymmetric disc stenosis, and MRI or CT suggestive of degenerative changes in the corresponding discs. Patients with previous history of idiopathic scoliosis (IS), lumbar spine surgery, lumbar spine fracture, metabolic bone disease, lower extremity inequality, and history of spinal infection and tumor were excluded. 1.2 Study methods Physical examination: all patients underwent a detailed neurological examination. Imaging examination: Coronal plane recordings were made by measuring the standing position orthopantomograms: Cobb angle; position of the apex of the lateral convexity; direction of the convexity; degree of rotation of the parietal vertebrae (Nash-Moe method); and lateral slippage of adjacent vertebrae (≥3mm). Sagittal recordings: Cobb angle of L1-L5, defined as “+” for anterior convexity and “-” for posterior convexity; vertebral sagittal slip. All cases in this group underwent myelography and CTM after admission to observe the compression of the nerve roots producing symptoms. 1.3 Statistical processing Statistical processing was performed using SPSS (ver13.0) statistical software. Comparison of the direction of convexity of DS of different genders was performed by Pearson Chi-Squaret test; correlation between lateral slip and vertebral rotation and Cobb angle was analyzed by Kendall’ nonparametric analysis; and comparison of the proportion of the causes of nerve compression between convex and concave sides was performed by χ2 test. 2.Results 2.1 Lumbar pain symptoms The main symptoms of DS were lumbar pain, radiating pain in the lower limbs and intermittent claudication, of which 127 cases (91.6%) had lumbar pain, 104 cases (75.0%) had lumbar pain combined with radiating pain in the lower limbs, and 85 cases (61.2%) had intermittent claudication. Low back pain was the most common first and main symptom, and the history of low back pain in this group ranged from 8 months to 40 years (mean 12.4 years). Most of the patients had pain relief after forward bending of the lumbar region, but 23 cases (16.5%) required bed rest for symptomatic relief. 101 cases (72.6%) of the patients with low back pain had progressive worsening of their symptoms, and 27 cases (19.4%) required hospitalization because of the severe low back pain, which interfered with normal life and rest. 2.2 Radiographic characteristics 2.2.1 Curvature The curvature in this group ranged from 11° to 50°, with an average of 16.7°. There were 106 cases (76.3%) with <20°, 21 cases (15.1%) with 20°-29°, and 12 cases (8.6%) with ≥30°. The apex was mostly in the intervertebral space, of which 45 cases had the apex in the L3-4 space and 40 cases in the L2-3 space, accounting for a total of 61% of the cases. The scoliosis consisted of 2-6 segments, with an average of 3.5 segments, and the average curvature of each segment was 4.7°, and there was a trend of increase in the incidence rate with the increase of curvature in the female patients: the sex ratio of men and women was 69:37 in the case of <20°, 7:14 in the case of 21°-29° degrees, and 2:10 in the case of ≥30° degrees. 2.2.2 Types of scoliosis and direction of scoliosis All DS cases in this group were lumbar and thoracolumbar scoliosis: lumbar scoliosis was the most frequent, 129 cases (92.8%), and thoracolumbar scoliosis was found in 10 cases (7.2%). In 81 cases (58.3%), the convexity was to the left and in 58 cases (41.7%) to the right. In male DS patients, the convexity of the left side of the primary curvature was roughly equal to that of the right side (21:25), and there was no significant difference in the distribution of the convex lateral direction (P=0.061); in female patients, there was significantly more convexity on the left side than on the right side (60:33), and there was a significant difference in the distribution of the convex lateral direction (P=0.033). 2.2.3 Vertebral rotation and lateral slip In this group, 104 cases (74.8%) had a rotation of <Ⅰdegree, 29 cases (20.9%) had a rotation ofⅠ-Ⅱdegree, and 6 cases (4.3%) had a rotation of more thanⅡdegree.Lateral slip was observed in 56 cases (40.3%), of which 13 cases (9.4%) had a multisegmental lateral slip. The lateral slip distance ranged from 3-11 mm. lateral slip was most common at L2-3 (16 cases) and L3-4 (25 cases) near the lower end vertebrae. in this group of patients, lateral slip was positively correlated with vertebral rotation (r=0.663, P=0.000), and lateral slip was also positively correlated with Cobb's angle (r=0.472, P=0.000). 2.2.4 Sagittal changes In this group, 119 cases (85.6%) had lumbar anterior convexity of less than 40°, with an average of 16.9° (-38° to +58°) in L1-L5, and 12 cases (8.6%) showed posterior convexity deformity; 62 cases (44.6%) combined with degenerative lumbar slippage of I-II degree. There were 10 cases of intervertebral spondylolisthesis at L2-3, 21 cases at L3-4, 24 cases at L4-5, and 17 cases at L5-S1, of which 12 cases were multisegmental spondylolisthesis. 2.3 Nerve root compression Both the convex and concave lower limbs of the lateral convexity could show lower limb nerve root symptoms (radiating pain, numbness and weakness of the lower limbs), except that radiating pain was more frequent on the convex side of the lower limbs than on the concave side (69:37). Myelography showed that both convex and concave side nerve roots could be compressed, with L4 and L5 nerve root compression being the most common. Of the 185 nerve roots compressed, 31 (17%) were L3 nerve roots, 72 (39%) were L4 nerve roots, 65 (35%) were L5 nerve roots, and 17 (9%) were S1 nerve roots. The causes of nerve compression varied, but displacement and distortion of the pedicle, vertebral rotation, and lateral slippage could cause pulling and compression of the nerve roots. 3.DISCUSSION 3.1 Symptom characterization of DS Low back pain and radiating pain in the lower limbs are the most common clinical manifestations of DS. The pain is multifactorial, such as muscle fatigue, joint protrusion hypertrophy, disc degeneration, and trunk imbalance. It is now generally accepted that it is not easy to determine the exact site of origin of pain and that scoliosis may be only one of the causes of pain. Fatigue and strain of the muscles on the convex side may be the initial cause of the pain, with symptoms worsening when the low back is stretched out and active. When the pain is on the concave side, the symptoms are mainly from degeneration of the discs and small joints. The pain is more pronounced in scoliosis combined with a smaller anterior lumbar convexity. This group of cases showed that the pain in the lower extremities could be relieved after forward lumbar flexion in most of the patients, but 16.5% of the patients needed to eliminate their symptoms by bed rest. This suggests that unlike IS, which presents as mechanical back pain, pain in DS can present as mechanical pain, spinal stenosis pain, or a mixture of both. 3.2 Analysis of imaging characteristics of DS The radiographs of our DS cases had the following characteristics: lumbar curvature was the most common, followed by thoracolumbar segmental curvature, and no patients with thoracic curvature were found; the curvature was small, with 10°-20° being the most common; the apex was mostly in the L3-4 interspace and the L2-3 interspace; the segments were short (an average of 3.5 segments), and the distribution of right and left lateral convexity was relatively close to each other, as well as the lumbar anterior convexity being reduced, which was similar to that of most reports in the literature. In addition, DS is often combined with rotation and slippage of the vertebral body, and similar results were found in our group. The lack of a complete history and previous imaging data made the diagnosis of DS difficult. Therefore, understanding the clinical and imaging features of DS can help to differentiate it from scoliosis progressed from IS and make a correct diagnosis. The distribution characteristics of DS and IS are clearly different: the prevalence of DS (7.5-10%) is higher than that of IS (1-3%); the vast majority of DS is lumbar curvature, and the chances of left/right lateral convexity are close to each other, whereas lumbar curvature is a rare type of scoliosis in IS, which accounts for 10-15% of the types of IS scoliosis, and most of the scoliosis is left lateral convexity (about 70%). Therefore, Perennou et al. noted that in older patients with scoliosis who have a close chance of left/right lateral convexity and less curvature, there is a small chance of scoliosis progressing from IS. Combined with the results of this study and related reports, each adult patient with lumbar curvature should also be identified according to the following characteristics: DS is a short-segment scoliosis (3.5 segments in this group) with a small curvature, inconsistent degree of disc degeneration leading to uneven curvature of all segments, apexes mostly in the intervertebral space (most common in the L3-4 and L2-3 spaces), and often combined with a reduced lumbar lordosis and vertebral rotation and slippage; whereas, adult-onset IS with a In adult-onset IS, the lumbar curvature segments are longer (an average of 5 segments), and the lateral convexity tends to be uniformly curved with a large curvature, with the apexes of L1 and L2 being the most common. MRI or CT suggesting disc degeneration in the corresponding segments also helps in the differentiation between the two; in addition, intractable pain is a characteristic of DS, with complex causes of pain, which can occur on both the convex and concave sides; whereas in adult-onset IS, the lumbar pain is mostly mechanical and occurs mainly on the convex side of the primary bend. It is generally recognized that the distribution of lateral convexity in DS is roughly equivalent, but it has not been clarified whether there is a difference in the distribution of lateral convexity direction between male and female genders. In the study by Perennou et al: the proportion of left lateral convexity was higher than right lateral convexity in female DS, but there was no significant difference. However, in our case, female patients had significantly more left lateral convexity than right lateral convexity (60:33), which was a significant difference (P=0.033). Due to the lack of more relevant research reports, the possibility of admission rate bias in this group of cases cannot be excluded yet, but whether there is a difference between men and women in the distribution of the direction of lateral convexity remains to be further studied. 3.3 Correlation analysis of imaging indexes of DS There are different opinions on whether there is a correlation between the imaging indexes of DS. Ploumis et al. found that intervertebral rotation was positively correlated with lateral slip, and Cobb angle was negatively correlated with lumbar kyphosis, but there are also some studies that found the opposite. In our case, lateral slip was positively correlated with vertebral rotation (r=0.663, P=0.000), as were lateral slip and Cobb angle. The authors concluded that despite the presence of deformities such as vertebral body slippage in both the coronal and sagittal planes, DS remains a three-dimensional deformity, and therefore its vertebral body deviation from the midline in the coronal plane, vertebral body rotation in the axial plane, and alterations in the sagittal plane are not isolated manifestations. Studies have shown that there may also be a correlation between imaging parameters and symptoms.Schwab et al. studied 95 cases of DS and found that there was a correlation between pain level and lumbar lordosis, thoracolumbar lordosis, and L3 and L4 endplate tilt angles, but not the size of the curvature.Glassman et al. analyzed the correlation between the position of the lordotic curve, lateral slippage, rotational subluxation, and sagittal balance of scoliosis in adults and the symptoms of the condition. Correlation analysis found that sagittal imbalance was associated with pain, while scoliosis Cobb's angle was not, and hypothesized that sagittal balance was the most important and plausible indicator of symptomatic correlation. Currently, most scholars have agreed that in the treatment of DS, "restoration of physiologic lumbar lordosis is more meaningful than correction of scoliosis". 3.4.Analysis of the causes of nerve root compression in DS Currently, the causes of nerve root damage associated with DS are not well understood. Previous studies have suggested that nerve root symptoms mainly occur on the concave side of the scoliosis, caused by crumpling of the hypertrophied ligamentum flavum and further narrowing of the foramen magnum after disc collapse, while on the convex side, the foramen magnum is enlarged and the ligamentum flavum is in a state of tension, which does not aggravate the narrowing of the spinal canal, and symptoms are less likely to occur. However, in recent years, there are more and more reports in the literature that the nerve roots on the convex and concave sides can be compressed, and the nerve root compression is not only related to the factors of articular synostosis, lateral saphenous fossa stenosis, and intervertebral disc herniation, but also the corresponding changes caused by the abnormalities of the negative gravity line, which is also an important reason for the compression of the nerve roots, but it still needs to be confirmed by a large sample of clinical studies. In this group of cases, we found that DS is often combined with nerve root damage, and the nerve root damage can appear on both convex and concave sides of the lateral convexity.The cause of nerve root damage in DS is more complicated than that in degenerative lumbar spinal stenosis. In most degenerative stenosis, nerve root compression is often secondary to hyperplasia and cohesion of the articular synovial joints and lateral and posterior herniation of the intervertebral discs, while in DS, the causes of nerve root compression are more complex. In addition to degenerative factors, displacement and distortion of the pedicle root, rotation of the vertebral body, and lateral slippage can cause pulling and compression of the nerve root. First, the causes of nerve root damage on the convex and concave sides are not the same. The CTM in this group showed that in the segments where disc collapse and lateral slip occurred on the concave side of the lateral convexity, the phenomenon of downward displacement of the superior vertebral body and inward displacement of the inferior vertebral body on the concave side appeared and led to nerve root compression on the concave side. In addition, other nerve root compression factors were not significantly different between the convex and concave sides, but the lower extremity radiating pain symptoms were significantly more frequent on the convex side than on the concave side, which was not consistent. It was hypothesized that the pulling effect might be an important cause of nerve root damage on the convex side, which included the pulling effect of the convex side of the lateral convexity on the nerve root, and the rotational subluxation of the vertebral body exacerbated the pulling effect on the nerve root on the convex side. Second, rotational subluxation of the vertebral body is associated with nerve root compression.Toyone et al. suggested that compression of the convex nerve root by the superior articular process of the inferior vertebral body, which had slipped laterally, and compression of the concave dural sac by the inferior articular process of the superior vertebral body, were responsible for the symptoms in the lower extremities. This group of cases showed that subluxation of the articular eminence could occur on both the convex and concave sides of the scoliosis. The authors concluded that nerve root compression in DS is multifactorial, and it is difficult to correctly reflect the cause of nerve root compression in DS on CT or MRI images at a single level due to rotation and slippage of the vertebral body. Because CT scanning cannot observe the overall morphology of the spinal canal, and MRI examination shows the "shift in and out phenomenon" on sagittal radiographs due to scoliosis and vertebral rotation, spinal myelography and CTM scanning were performed in all of the cases in this group. In our opinion, myelography can dynamically reflect the whole picture of the spinal canal, show the degree and location of stenosis, and clearly show the nerve root cuffs, and supplemented with CTM examination, it can clearly show the compression of the dural sac or the nerve roots in the case of DS combined with lumbar stenosis in all planes. For patients with complex conditions and difficult diagnosis, myelography and CTM are more meaningful than MRI. In conclusion, nerve root compression in DS is the result of a combination of factors, and the presence of scoliosis increases the complexity of spinal stenosis. Defining the characteristics of nerve root compression in DS not only helps to make a correct diagnosis, but also determines the scope of surgical decompression and avoids incomplete and blind decompression during surgery.