MALE FEMALE
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Figure12: A sagittal T2 weighted image showing reduced signal of the disc at L4/L5 level with posterior disc protrusion and indentation of the anterior theca.
Posterior disc protrusion
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Figure 13: An axial T2weighted MRI image of the lumbar spine of the same patient showing exit nerve root compression at L4/5 on the left side.
Exit nerve root compression
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Figure 14: A sagittal T2 weighted image of the lumbosacral spine of another patient showing reversal of the lumbosacral curvature, osteophyte (A),type 2 Modic changes of the vertebral bodies(B) and dehydrated disc cartilages(C).
C
B A
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Figure 15: An axial T2weighted MRI image of the same patient showing bilateral exit nerve root compression of the lumbosacral spine at L2/L3 level.
Exit nerve roots
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Discussion
Studies of low back pain in the African continent were few prior to the year 2000, however of recent of recent there has been increased interest in this area particularly with the advent of MRI.
Magnetic Resonance Imaging demonstrates good anatomy of the lumbosacral spine. The various sequencies highlight the different aspects of the spine such as the vertebral bodies, intervertebral discs, spinal canal and neural elements. This allows for detailed evaluation and accurate diagnosis.
The peak age incidence of the cohort was consistent with previous report in literature. Low back pain is more common in the fourth to sixth decade and this has been attributed to the wear and tear that occurs with advancement in age.
However this study did not include individuals below the age of eighteen.
Earlier work by Nzeh and Komolafe48 on the lumbar spinal radiographs of patients symptomatic for low back pain showed a rise in the incidence of degenerative spinal disease with a peak at seventh decade while this study shows a peak in the fifth decade which correlate with other more recent studies46,47. These observations may reflect a change in socio-demographic characteristic in this environment, over two decades. It may also reflect an earlier onset of symptomatic spinal degenerative disease due to lifestyle changes as predisposing factor29.
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Adeyinika47 and Omidiji’s47study on magnetic resonance imaging diagnoses in the lumbar spine of adults with low back pain showed a mean age of 53.27years, while that of Galukande1 et al showed a lower mean age of 43.83years, perhaps because most of Galukande’s patients were in the younger age group1. The mean age in this study was 50.1years; which is similar to those of Akano and Adeyinika et al 46,47. The sex incidence is somewhat controversial: although the majority of studies including this study showed a male preponderance, others found low back pain to be common in females. This male preponderance is in concordance with some earlier studies such as Akano’s46 study which showed a male to female ratio of 2:146, Adeyinka47 et al which also showed a male to female ratio of 1.36:147.
The male preponderance, however, may be attributed to the increased level of physical / vigorous activities in which the male gender are believed to undergo leading to an increase in ‘wear and tear’ in the musculoskeletal system and thus predisposing them to an increase in the incidence of low back pain.These observations are supported by studies done by Miller at al27 where they concluded that the male discs degenerated more than female discs at most ages. And that the higher mechanical stress may be responsible for the earlier degeneration of male discs1,29
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The male to female ratio in this study agreed with that of Akano46and Adeyinka47with the values of 1.22:1, 2:1 and 1.36:1 respectively.
This almost equivalent ratio of the sexes may indicate equality of male and female in the work place, ability to seek health care and level of education and enlightenment.
Most of the subjects (86.4%) in this study were married, which is the expected for the studied age group in this environment.
Majority of the patients (60%) were Christians, while 38.8% subjects were Muslims, the remaining 1.2% were those with indigenous beliefs.
Although in Abuja, majority (50%) of the population are Muslims, 40% are Christians and the remaining 10% are those with indigenous beliefs, 48 the slight Christian predominance in this study, may be attributed to the way of life of Muslims, in that the Muslim act of worship , involves frequent bowing down / prostrating during prayers known as sujud (sujud is an Arabic word meaning prostration to God in the direction of the Kaaba at Mecca which is usually done during the daily prayers. The position involves having the forehead, nose, both hands, knees and all toes touching the ground together),50hence a form of exercise, possibly reducing the incidence of low back pain in the Muslims populace.
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Intercultural differences in perceiving or reporting back pain can be hypothesized as the most likely explanation of the markedly different prevalence rates of the disorder in the United Kingdom and East and West Germany51.
In describing the pain, up to 52.5% of patients in this study were unable to identify any causative or related factor and described the pain as sudden in onset; compared to the 19.2% of patients that associated their LBP with trauma or fall.
Upto 55.7% of the subjects complained of pain that had lasted over one year compared to the 9.1% that have had the pain for a week. This could be because most patients with a shorter duration of pain maybe experiencing acute low back pain, which usually resolves spontaneously with a short term use of medications, therefore not many of such patients will follow up on an MRI investigation33. As a result, a large proportion of patients undergoing MRI have long duration persistent low back pain.
Most people who experience activity limiting low back pain go on to have recurrent episodes.A wide range of factors are linked to both the onset and persistence of low back pain52.
Civil servants/office workers (35.9%) accounted for most of the occupation of the patients that were evaluated, while retirees accounted for 15.6%, hospital workers which included mostly nurses, doctors and hospital assistants (14.1%).
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The reason for this could be attributed to the fact that, Abuja (FCT), where this study is being conducted, is the seat of government, and has a large government based work force, which are civil servants54 accounting for most of the participants in this study.Sustained sedentary occupation is a known risk factor for low back pain55.
Another factor could be that of affordability. Most of those that came for the MRI investigation were employed and could afford it. Conversely, the cost of the MRI investigation is seemingly high, in a developing country, where 2.46%54 are unemployed. Hence the unemployed with low back pain may not be able to afford the investigation and therefore will seek an alternative and cheaper way to be treated.
This present study showed a close relationship of physical loading occupations and low back pain that was statistically significant (with a p value of 0.0008). Most of the patients’ 65% in this occupational group were construction workers, who are involved in heavy lifting and probably developed low back pain due to wear and tear. This group of patients presented with a history of trauma prior to onset of pain.
There is frequent occurrence of loss of lumbar lordosisand was seen in 69.4% of cases. This however is a non specific finding and usually may be due to muscle spasm or probably poor posturing techniques.
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Disc cartilage signal changes were seen in 76.4% of cases. Isolated reduction in height of the disc cartilages was seen in 0.9% of cases.
Studies have shown that the isolated loss of height at any one disc level is usually indicative of early degeneration.56
Several factors have been reported to cause disc degeneration. The decrease in the number and activity of disc cells depends on the mechanical loading, nutrient transport, life style, genetic factors and growth factors57.
Disc degeneration begins in early childhood as vessels within the disc space slowly regress. With increasing age, the metabolic strain to the intervertebral disc increases because of decreasing blood supply and decreasing diffusion. These metabolic changes lead to alterations in overall change in the disc space, decreasing the net inward flow of fluid and decreasing water content from 90% to 70%; this change ultimately leads to loss of disc height and expandability. Once the degenerative cascade begins, spinal mechanics are altered, and abnormal loading on adjacent levels may result in ligamentous strain causing pain58.
This study is on adults only, and the above scenario could explain the high percentage of subjects with disc signal changes from degenerative changes due to age.
A genetic predisposition to disc degeneration has been proven by studies on twins59. Previously, heavy physical loading was the main suspected risk factor for
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disc degeneration. However, results of exposure-discordant monozygotic and classic twin studies suggest that physical loading specific to occupation and sport has a relatively minor role in disc degeneration, beyond that of upright postures and routine activities of daily living, showing that hereditary factors have a dominant role in disc degeneration59.
Osteophytic spurs were found in 46.3% of patients. Disc herniation was seen in 77.1% of cases. Posterior osteophytesand posterior disc herniation contribute to spinal and foraminal stenosis which all are known etiologies of low back pain60,61. Progressive narrowing of the spinal canal can occur alone or in combination with disc herniations.This often occurs from acquired lumbar degenerative changes61. In literature most cases of low back pain are due to various etiologies, such as degenerative changes, nerve root compression due to prolapsed disc, infective spinal pathologies such to tuberculosis and fractures.1
The major cause of low back pain in the subjects that participated in this study was degenerative process of ageing which is similar to findings in other similar studies1, 46, 47. Degenerative diseases of the spine [lumbar spondylosis] accounted for 84% of cases in this study showing the highest incidence of the diagnosed spinal abnormalities.
Other spinal abnormalities like metastasis and Potts disease showed very low incidence of 4.9% and 1.6% respectively.
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This low incidence is possibly due to the fact that most of the patients that may have had other spinal abnormalities/lesions, for example, metastases to the lumbar spine, were not included in this study, since an MRI is not routinely requested for low back pain on account of clinical suspicion of metastasis to the spine.
Another plausible reason may be that the combination of clinical features, laboratory and radiographic findings may aid in diagnosing spinal abnormalities like metastasis or Potts disease without need to recourse to MRI especially when the cost implications and recourse challenges are put into perspective.
Metastasis has been noted as the most common tumor to affect the vertebral marrow, particularly in those over 40 years of age62. MR imaging has been advocated as a useful method for the evaluation of bone marrow diseases, including bone metastases11. This study agrees with the above because the only tumour found was metastases.
Spine infections are easily recognized on MRI and were seen in 6.9% of the patients in this study.
The 0.2 Tesla (low field) MRI machine used in this study was able to detect the cause of low back pain in the study subjects and the findings are comparable or similar to those in other studies where higher tesla equipmenthave been used.
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It could therefore be concluded that the results obtained are accurate and that the equipment used is reliable and should be applied for future examinations.
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CONCLUSION
Spinal degenerative disease changes were the commonest finding in this cohort of patients studied for low back pain by MRI in Abuja.
Low back pain was more common in males than females and in the fifth decade of life. Low back pain affected mostly those in the working class population.
MRI was used as a preferred imaging diagnostic tool due to its versatility and accuracy in detecting spinal disorders.
The age of patients affected by low back pain is gradually decreasing if this trend continues there will likely be a significant decrease in the productivity of workforce. Therefore it is imperative that a sensitive means of detection be made available and affordable.
MRI has proven to be a sensitive diagnostic tool for the evaluation of low back pain irrespective of the field strength of the magnet used. It has been demonstrated in this study that the protocols, technique and 0.2 Tesla strength used for diagnosis were optimal and adequate.
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RECOMMENDATION
1. The high cost of MRI examination limits the lower earning populace from taking advantage of the versatility of MRI for diagnosis of low back pain.
Attempts to reduce cost of the investigation should be made for easy access to less privileged. Indeed, MRI investigationfor LBP should be accessible through the NHIS.
2. Availability: In as much as attempts are being made to get more MRI facilities available, they are still not easily available for those in the rural areas.
3. Service delivery: Maintenance of the machine requires regular power supply and trained personnel to ensure full working capacity; poor power supply is a national issue due to the poor power supply, which should be addressed to enable better service delivery to the populace. Exploration of the current solar supply should be considered.
4. Health education and awareness should be encouraged even among the literate to ensure appropriate investigation and diagnosis of low back pain.
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