|Year : 2023 | Volume
| Issue : 1 | Page : 106-110
Predictability of degenerative disc disease by lumbar sagittal alignment on conventional radiograph in comparison with cross-sectional magnetic resonance imaging
P Madhuchandra, KM Pawankumar, G Sunil Santhosh, KP Raju
Department of Orthopaedics, BGS Global Institute of Medical Sciences, Bengaluru, Karnataka, India
|Date of Submission||08-Sep-2022|
|Date of Decision||02-Oct-2022|
|Date of Acceptance||02-Oct-2022|
|Date of Web Publication||27-Dec-2022|
No. 757, 5th Main Road, ISRO Layout, Bengaluru - 560 078, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Degenerative disc disease (DDD) affects approximately 80% of the population. Changes in the magnitude of lumbar lordosis significantly change the weight-bearing patterns in lumbar facet joints and intervertebral discs. It is essential to understand the contribution of hypo and hyperlordosis toward the development of disc degeneration disease. Materials and Methods: A retrospective study of X-ray and magnetic resonance imaging (MRI) of the lumbosacral spine of 200 patients with chronic low back ache. The lumbar lordotic angle was measured in a standing lateral radiograph using Cobb's method (between the lines drawn along the inferior end plate of D12 and the superior end plate of S1 vertebrae). DDD was assessed on MRI based on the Pfirrmann grading system. The correlation between the lordosis measured on the radiograph and DDD on MRI was assessed. Results: We analyzed the lumbar sagittal alignment effect on the degree of disc degenerative disease. Out of 200 patients, 70 had no disc degenerative disease (Grade I, II) whose Cobb's angle was 45°–75°. The remaining 130 patients showed disc changes (Grades III-V) on MRI and had Cobb's angle <45° or >75°. There was a statistically significant difference between Cobb's angle in normal and DDD patients with P = 0.009 (P < 0.05). Conclusion: DDD correlated with deviation from an optimal lumbar lordotic angle (Cobb's angle) of 45° to 75°. Deviation from optimal values would compromise the optimal weight-bearing conditions on the lumbar spine resulting in DDD. These results may well have implications for the diagnosis, prevention, treatment, and rehabilitation of DDD.
Keywords: Cobb's angle, disc degenerative disease, lumbar lordosis, Pfirrmann grading
|How to cite this article:|
Madhuchandra P, Pawankumar K M, Santhosh G S, Raju K P. Predictability of degenerative disc disease by lumbar sagittal alignment on conventional radiograph in comparison with cross-sectional magnetic resonance imaging. J Orthop Dis Traumatol 2023;6:106-10
|How to cite this URL:|
Madhuchandra P, Pawankumar K M, Santhosh G S, Raju K P. Predictability of degenerative disc disease by lumbar sagittal alignment on conventional radiograph in comparison with cross-sectional magnetic resonance imaging. J Orthop Dis Traumatol [serial online] 2023 [cited 2023 Jan 30];6:106-10. Available from: https://jodt.org/text.asp?2023/6/1/106/365294
| Introduction|| |
Degenerative disc disease (DDD) affects approximately 80% of the population. It is one of the common causes of chronic low back ache. Hence, amounts to a significant health burden.
The etiology of DDD is multifactorial. It is influenced by genetics, systemic diseases, occupation, obesity, and excessive or abnormal joint loading. Of all these, mechanical loading has been identified as a major extrinsic component in the onset and progression of DDD. The normal orientation of the lumbo-sacro-pelvic structure plays an important role in the determination of shear and compressive forces applied on the anterior (vertebral bodies and intervertebral discs) and posterior elements (facet joints) of the lumbar intervertebral column. The primary postural curves of the spine including the lumbar lordosis provide optimal weight-bearing by spinal joints. Changes in the magnitude of lumbar lordosis significantly change the weight-bearing patterns in lumbar facet joints and intervertebral discs., Significant changes from the optimal degree of lumbar lordosis could overload spinal joints and lead to the development of DDD. It is essential to understand the contribution of hypo and hyperlordosis toward the development of disc degeneration disease and determine the degree of this degeneration. Most studies in the literature are on the effect of lordosis on chronic low back ache or spondylolisthesis; studies on the development of a varying degree of DDD are very scanty. Hence, the present study was conducted to predict the degenerative disc disease by lumbar sagittal alignment.
| Materials and Methods|| |
A cross-sectional retrospective study was conducted in the department of orthopedics and radiology of a tertiary care center hospital, for 1 year, between June 2019 and May 2020. Patients who had visited the outpatient and those who were admitted as inpatients with low back ache, for whom magnetic resonance imaging (MRI) and X-rays were done were included in the study. Magnetic resonance images and corresponding X-rays of all the patients were obtained from the picture archiving and communication system to correlate the outcome. A total of 200 patients, both males and females were included as a part of the study. The patients presenting with low back ache for more than 3 months to the orthopedics department between the age group of 25 and 60 years and undergone X-ray and magnetic resonance images were included in the study. Patients who had low back ache due to trauma, congenital anomalies, infective pathologies, spondylolysis and spondylolisthesis, neoplastic pathologies, previous spinal surgeries, and also pregnant women were excluded from the study.
All standing anteroposterior and lateral radiographs were taken using the standard positioning methods. The lateral radiographs were done with the patient standing with arms crossed over the chest. This position is suitable for the measurement of lumbar lordosis. MRI was performed with a 1.5 Tesla machine using a standard protocol for all patients in a supine position with extended lower limbs. Sagittal T1 and T2 and axial T2-weighted sequences were used in imaging protocol and were used to assess and grade the disc degenerative pathologies.
Lumbar lordosis was measured using the commonly used gold standard Cobb's angle. Cobb's angle was measured by the angle subtended by the intersection of lines drawn along the inferior end plate of the D12 and superior end plate of the S1 vertebrae [Figure 1]. The presence and the degree of intervertebral disc degenerative disease were assessed on T2-weighted images of sagittal and axial cuts in the intervertebral discs. The Pfirrmann grading system was used to assess the lumbar disc degeneration, according to which DDD is graded into five grades. Grades I and II are normal. Grades III to V suggests a varying degree of disc degenerative changes [Table 1]. These grades were sometimes associated with a disc bulge, protrusion, and extrusion.
|Figure 1: Measurement of Cobb's angle in the lateral standing radiograph|
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Mean and standard deviations were calculated for each variable. An Independent t-test was used to calculate the differences between normal individuals and patients with disc pathologies. The level of significance was decided by P < 0.05. Statistical analyses were performed using SPSS- version 23.0.
| Results|| |
A total of 200 patients who met the inclusion criteria were included in the study. Out of 200 individuals, 120 were females and 80 were males. The age group of the study population ranged from 25 to 60 years [Figure 2]. The mean age of the study population is 43 ± 5 years. The mean age among females in the study population is 40.3 ± 3 years. The mean age among males in the study population is 46.7 ± 3 years.
Out of 200 patients, 70 are noted to have Grades I and II degenerative changes in the intervertebral disc according to the Pfirrmann grading which is considered normal. Among them, 45 were females and 25 were males. One hundred and thirty patients have Grades III, IV, and V degenerative changes, out of which 75 were females and 55 were males [Figure 3]. The distribution of patients according to the Pfirrmann grading was Grade I-38, Grade II-32, Grade III-40, Grade IV-55, and Grade V-35 [Figure 4].
|Figure 3: Distribution of study population based on sex and presence of degenerative disc disease|
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Among 70 individuals who had Grades I and II disc changes which are considered normal, Cobb's angle was found to range between 45° and 75°. The mean Cobb's angle in males is 50.1 ± 2.2 and in females is 61.3 ± 2.8. There was no statistically significant difference between Cobb's angle measurements among both sexes, in the normal Pfirrmann grade group (P > 0.05). Among 130 individuals who had Grades III, IV, and V disc changes, i.e., DDD, Cobb's angle was found to range between 20°–44° (hypolordosis) and 76°–95° (hyperlordosis). Sixty-three patients had hypolordosis and 67 patients had hyperlordosis. Mean Cobb's angle in males is 32.2 ± 2 (hypolordosis) and 81.2 ± 2.5 (hyperlordosis) and in females is 30 ± 2.5 (hypolordosis) and 83 ± 2.3 (hyperlordosis). There was no statistically significant difference between Cobb's angle measurements among both sexes, in the DDD group (P > 0.05).
Correlation between Cobb's angle measured in radiograph and Grades III, IV, and V Pfirrmann (DDD group) assessed on MRI was done by independent t-test. P <0.05 was considered to be statistically significant. The mean Cobb's angle in the normal group (N = 70) was 55.7° ± 2.1°. Mean Cobb's angle in the DDD group – hypolordosis (N = 63) was 31.2° ± 2.2°. Mean Cobb's angle in DDD group – hyperlordosis (N = 67) was 82.1° ± 2.2°. There was a statistically significant difference between Cobb's angle in normal and DDD patients with P = 0.009 (< 0.05) [Table 2]. The distribution of Cobb's angle and Pfirrmann grades are mentioned in [Table 3].
|Table 2: Comparison of Cobb's angle measurement in normal and degenerative disc disease groups|
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| Discussion|| |
DDD is one of the most common causes of chronic low back ache. It is the most common cause of disability in the middle age group. The association between changes in the lumbar sagittal alignment and degeneration of the lumbar spine has been described in the literature. However, not many studies have been done to assess the correlation between lumbar sagittal alignment changes and disc degenerative disease.
It is a proven fact that decreased lordosis increases the load on intervertebral discs and increased lordosis increases the load on facet joints., Thus, it is important to determine the ideal or optimal range of lumbar sagittal alignment to prevent or manage disc pathologies. In the current study, we analyzed the lumbar sagittal alignment for potential associations with intervertebral disc pathologies.
Lumbar sagittal alignment (Cobb's angle) was measured on standing radiographs to obtain the lumbar lordosis angle. MRI allows superior assessment of disc degenerative diseases. Hence, in our study, we assessed both to predict DDD, on a radiograph. No such studies have been done in the past to the best of our knowledge.
The most reliable normal range for lumbar lordosis has been reported as 48° to 78°. Patients with the normal disc of the Pfirrmann Grades I and II fell in this range in our study [Figure 5]. This wide range of normal values could be due to variations in the methods to measure lordosis and variations in the positioning of the pelvis. In our study, the Pfirrmann' s Grade I and Grade II (normal disc) had lordotic angles ranging between 45° and 75° which is consistent with the other studies [Figure 6] and [Figure 7].
|Figure 5: Distribution of DDD on either side of the optimal lordotic angle. DDD: Degenerative disc disease|
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|Figure 6: Grade 1 Pfirrmann classification with corresponding X-ray and Cobb's angle|
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|Figure 7: Grade 2 Pfirrmann classification with corresponding X-ray and Cobb's angle|
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It is significant to note that the mean lordotic angle in males and females was 50.1° and 61.3°, respectively, the higher values in females could be due to the position of the pelvis and also because they are morphologically suited to have increased lordosis. In our study, we noted progression in the disc degeneration as the lordotic angle became < 44° or when it became more than 76°. We also noted higher Pfirrmann-graded DDD as the lordosis increased or decreased. The difference in Cobb's angle between the patients with DDD and the normal population was statistically significant (P < 0.05).
Hypolordosis was seen in younger females, patients with canal stenosis, postural problems, and patients with chronic low back ache. Hyperlordosis was seen in females (may be due to morphology), obese individuals, and those with a genetic predisposition.
In our study, the optimal lordotic angle was found to be 45° to 75° which was seen in 70 individuals having Pfirrmann Grades I and II disc changes. Any deviation from this optimal value resulted in the development of DDD with 130 patients falling on either side of the optimal values [Figure 8], [Figure 9], [Figure 10]. There was no statistically significant difference between males and females among the normal population and DDD regarding lordotic angle. Our results are consistent with the notion that the lumbar spine under optimal weight-bearing conditions shows the optimal lordotic angle and also available literature supports that hypo and hyperlordosis resulted in DDD.,
|Figure 8: Grade 3 Pfirrmann classification with corresponding X-ray and Cobb's angle|
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|Figure 9: Grade 4 Pfirrmann classification with corresponding X-ray and Cobb's angle|
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|Figure 10: Grade 5 Pfirrmann classification with disc extrusion and corresponding X-ray and Cobb's angle|
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It is a retrospective study, a prospective study would have given more reliable results. It is difficult to analyze if DDD led to changes in lordotic angle or vice versa. The sample size in our study is small for a retrospective study; hence, it is difficult to extrapolate the study outcome to the general population. One more negative point of the study is that it is not correlated with clinical data.
| Conclusion|| |
DDD correlated with deviation from the optimal lumbar lordotic angle (Cobb's angle) of 45° to 75°. Deviation from optimal values would compromise the optimal weight-bearing conditions on the lumbar spine resulting in DDD. These results may well have implications for the diagnosis, prevention, treatment, and rehabilitation of DDD. However, the dilemma of which comes first, sagittal imbalance or DDD needs to be answered.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2], [Table 3]