Most Common MRI findings in Lumbosacral Degenerative changes in Nepal Police

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one of the leading causes of LBP. Moreover, Nepalese police are in a more rigorous workout than other individuals and degenerative changes can be more obvious. It includes conditions such as disc bulge, disc Herniation, osteophyte formation, spinal canal stenosis, lateral recess stenosis, foraminal stenosis, spondylolisthesis, radiculopathy, and vertebral body endplate changes. It can lead to a reduction in the quality of life. 2 For diagnosing the cause of LBP, various modalities such as myelography, plain x-ray, and CT scan are used. However, magnetic resonance imaging (MRI) with excellent tissue contrast is a better modality for assessing. With MRI because of better resolution and contrast, anatomical evaluation of spinal cord, spinal discs, ligaments, vertebral bodies, vascular structures, muscle tissues, and facet joints are more accurate. 3 Unfortunately, due to very few MRI machines in the country and the very high cost of MRI imaging, patients are reluctant to go for it. Therefore, only few researches have been carried out in our region regarding MRI findings in lumbosacral degenerative changes. However, as this study is confined to Nepal police personnel, and no previous study in Nepal police personnel has been carried out. Therefore, this is the first study of its type and will demonstrate the common findings overall, gender-wise and agewise in lumbosacral degenerative changes, and sort out the most common findings and the common location of each finding using MRI in Nepal police.

METHODS
We conducted the cross-sectional observational prospective study from Dec 2020 to Feb 2021 in the Department of Radiodiagnosis and Imaging, Nepal Police Hospital, Kathmandu, Nepal and included the LS-MRI report of 54 Nepal police personnel (in-service and retired) in our study after the following exclusion and inclusion criteria. The patient with a history of trauma, spinal infection, surgical history in the lumbosacral region, active malignancy, pregnancy, and metabolic condition were excluded. The patient with LS-spine MRI report with degenerative changes but do not fulfill exclusion criteria were included in our study. MRI images were taken in a 1.5T Hitachi machine with the acquisition of the T1WI, T2WI, STIR images in sagittal, axial, and coronal planes. The MRI findings evaluated were decrease disc height, disc desiccation changes, diffuse disc bulge, asymmetrical disc bulge, disc protrusion, disc extrusion, annular tear, central spinal canal stenosis, foraminal stenosis, spinal nerve compromise, lumbar lordosis preserved or not, osteophyte and modic changes. These findings were analyzed according to the recommendation of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology. 4 Two radiologists reported the MRI images with mutual consensus in disputed issues.The ethical clearance was obtained from Nepal Health Research council after Nepal Police Hospital approved the study.

RESULTS
54 Nepal police patients with Lumbosacral MRI reports were considered for the study, where 35 were male and 19 were female and the mean age was 41.8 years ± 13.5 years (range 20 -88years) (Table 1). Age was further classified into five age groups.Age 20-29 group contained 9 patients report, age 30-39 contained 16, age 40-49 contained 13, age 50-59 contained 10 and age >60 contained 6 (figure 1). We studied 378 discs in 54 patients (D11-D12 to L5-S1). We have included D11, D12 as well in this study as these discs are normally studied in Lumbosacral MRI in a routine examination.However, we have not mentioned its finding in this section as the study is confined to the lumbosacral spine. We found 140 discs involved in degenerative changes. Most commonly, L4-L5 and L5-S1 were involved. Each was involved in 44(31.42%) cases. These discs were followed by L3-L4, L2-L3, and L1-L2 respectively. The least involved lumbosacral disc wasL1-L2, which was found in six cases (4.2%) ( Table 2). Overall, the most common finding was disc desiccation changes (DDC), which was observed in 47 cases (87.7%) with L5-S1 (38 discs, 36.53 %) the most commonly involved disc level (Table 2 / Figure 2a). Then was diffuse disc bulge, which was observed in 46 cases (85.15%) with the maximum at L4-L5 level (32 discs, 45%) (Table 2/ Figure 2b).
Most Common MRI findings in Lumbosacral Degenerative changes in Nepal Police.     We have divided cases into 5 groups according to the age, 20-29, 30-39, 40-49, 50-59, and >=60 ( 59 and >= 60 group DDC and DDB were obvious common findings than LRS and FS and to other degenerative findings. The least commonly found degenerative finding in the 20-29 group was DDH, ADB, DP, DE, AT each with 11.1% cases. However, we found an increment in the percentage of these degenerative findings with age. DDH was consecutively 11.11%, 56.25%, 69.23 %, 80% and 50% cases in increasing age group. Asymmetrical bulge was consecutively 11.11%, 25%, 30.7 %, 50% and 33.33%. Disc protrusion was consecutively 11.11%, 31.25%, 23%, 30% and 33.33% and disc extrusion was consecutively 11.11%, 12.5%, 15.3%, 10 % and 16.6 % (Table5).         In gender-wise comparison, the most common finding in each gender (male or female) was again DDC and DDB (Table6). Both were 85.7 % of cases in males while consecutively 89.4 % and 84.2 % in females. The occurrence of disc protrusion, disc extrusion, and annular tear was comparatively more in males than females. They were respectively 31.4 %, 17.14 % and 20 % i9n male while 15.7 %, 0.5 % and 0.5 % in female. However, the occurrence of asymmetrical disc bulge was more in females than in males. It was 42.1 % cases in females and 25.7% cases in males.

DISCUSSION
In this study, we attempted to observe the most common degenerative changes overall, age-wise and gender-wise in Nepal police. Furthermore, we also analyzed the most common vertebral level for each degenerative finding. Our study showed; Disc desiccation changes and diffuse disc bulge are the most common finding for any age group and gender. Lower lumbar vertebrae especially L4-L5 and L5-S1 levels are mostly involved in degenerative changes.
Most commonly affected vertebral levels i.e., L4-L5 and L5-S1 bear a high magnitude of compressive forces at the lumbosacral junction. In addition, the anterior shear forces increase proportionally with the rising lumbosacral angle at the L4-L5 and L5-S1 motion segments (6). Disc desiccation changes and diffuse disc bulge are the most common findings in all aspects i.e., overall, age-wise as well as gender-wise, which is consistent with the finding of Kuswaha et.al. 7 and Karki et al. 8 Agewise, both findings were the most common finding for the group. With increasing age, we found it to be increasing from 20-29 group and almost consistent between 30-40, 40-50, 50-60 and ≥ 60 (80%-100%) ( Table 5). Genetic susceptibility may explain the prevalence of disc degeneration in young people. However, other factors, such as repeated trauma and a history of physical loading can cause disc degeneration. 9 Between male and female, both finding was between 85%-90% ( Table 6). The findings are consistent with previous studies. 10,11 DDC results from the replacement of glycosaminoglycan in the nucleus pulposus with fibrocartilage, which results in reduced disk height due to decreased volume of nucleus pulposus. 12 A diffuse disc bulge is the diffuse bulging of the annulus beyond the disc space. However, the annulus remains intact. 4 In the spine, an intervertebral disc is located between the vertebral bodies, which supports the spine by acting as a shock absorber. Intervertebral disc herniation in the spine is a condition in which the area of the disc is displaced posteriorly beyond the level of the adjacent vertebral body. 13 The annulus fibrosis may or may not cover a herniated disc. The herniation may be either focal or bulging. If the herniation is less than 180 degree of disc diameter it is called focal disc herniation and when it is 180degree to 360degree above the edges of the ring apophysis it is called disc bulge. 14 Focal bulging can be disc protrusion or disc extrusion. A protrusion occurs when the maximum distance between the edges of the disc material outside the disc space is less than the distance between the edges of the base of the disc space. The base is defined as the width of the disc material at the outer edge of the original disc space, where the disc material beyond the displacement of the disc space is continuous with the disc material in the disc space ( Figure  4a). An extrusion occurs when the herniated disc exceeds the distance between the edges of the disc material in at least one plane ( Figure 4b). 4 An annular tear was considered to represent the presence of any hyper intense signal within the peripheral annulus. 15 In our work, disc protrusion 14(25.9%) was a more common finding than disc extrusion 7(12.9%) in a herniated disc. The most commonly involved disc in protrusion was L4-L5, 8(47%) and L5-S1, 7(41.17%). However, for extrusion L5-S1, 4(57.14%) was obvious higher finding to L4-L5, 1 (14.2%) or L3-L4, 2 (20%). Disc herniation, both protrusion, and extrusion showed an increasing trend with age. Between males and females, Herniation was more common in males, both protrusion (31.4% vs 15.7%) and extrusion (17.4% vs 0.5%). Previous studies support the sex difference, which has established that males are more prone to degenerative changes compared to females likely to be associated with increased mechanical stress and injury. 10 As a consequence of disc degeneration, central spinal canal stenosis, lateral recess stenosis and foraminal stenosis with nerve root compression and compromise are common. 8 In midsagittal T2 image, spinal canal diameter less than 12mm indicates a narrowing of the spinal canal. A lateral recess is the space that is bounded anteriorly by the vertebral body's posterior surface, posteriorly by the superior articular facet, and laterally by the pedicle. It is measured as the distance between the posterior aspect of the vertebral body and the superior articular facet at the pedicle level in the axial section. If less than 4 mm is deemed stenosed. Compression of neural foramina is observed in sagittal T2WI. 14 In our study, we found, lateral recess stenosis 36(66.6%) and foraminal stenosis 36 (66.6%) were the most common among four followed by central spinal canal stenosis 29(53.7%) and nerve root compromise 29(53.7%). Each of them were common in L5-S1 and L4-L5. These findings are consistent with Thapa et al for the Nepalese population. 16 Prevalence of central canal stenosis and foraminal stenosis was seen increased from 20-29 group to 30-39 group, however, from 30-39 to ≥60 there was not much difference and ranged between (65% to 80%). We found lateral recess stenosis to be more in females (68%) than males (60%) while foraminal stenosis was more in males (68.5%) than females (52.6%).
Modic changes are manifested by alteration in MR signals adjacent to the endplates of the degenerated intervertebral disc. There are 3 types. Type I shows T1 hypointensity and T2 hyperintensity and depicts edema. Type II shows both hyperintensity and depicts fatty degeneration and Type III shows both hypointensity and depicts sclerosis. 17 We found modic II the most common among the 3 of them. It is consistent with Rai GS et. al. 18 Our study was conducted in a short period. Therefore, we were limited to only 54 cases. Furthermore, there can be variations in interpretation by the different radiologists. Direct correlation of MRI findings with patient symptoms was not performed as well.

CONCLUSIONS
This work shows, L4-L5 and L5-S1 is the most common intervertebral disc involved in degeneration in Nepal police personnel. Disc desiccation change and diffuse disc bulge are the most frequent finding irrespective of age and gender. Degenerative changes have an increasing trend with increasing age. Disc herniation is more common in male police personnel than females.