Altered disc compression in children with idiopathic low back pain: an upright magnetic resonance imaging backpack study

Neglected problem: Influence of school bag on lumbar segment in children

BACKGROUND AND OBJECTIVES

School bag (SB) load causes significant changes in the height and symmetry of the intervertebral discs at each level of the spine from T12-L1 to L5-S1. This study aims to determine the change in the size of the lumbar segment angle at a particularly critical point L3-L4 of the spine in relation to the load of the average weight of SB in healthy male children (students) at standing and after 2-minute gait.

METHODS

47 boys, aged 12.2 ± 0.92 years, underwent photogrammetric measurements in the sagittal plane in statics and dynamics, walking on a laboratory treadmill. Measurements were repeated with the weight of SB with a constant load of 6,251 kg, which represents 13.78% of the average body weight of our sample. The lumbar angle (LA) connecting the point of the big toe, the lumbar point L3-L4 and the processus spinosus C7 was measured. In gait, LA was measured in the phases of the middle support and the initial contact of the heel.

RESULTS

T-test of paired samples was used to estimate the change in LA at standing from 4.953° and walking phases from 6.295° to 7.332° in relation to the unloaded state, and the value of the effect size (ES) indicates that the impact of SB load is significant.

CONCLUSIONS

Cumulatively, microtraumas caused by SB load significantly affect the increase in intervertebral pressure at the L3-L4 point, which is susceptible to degenerative processes and which can be the cause of lumbar syndrome (LS). Preventive measures are needed in order to lighten SB in this population and introduce up to 10% of students' body weight into the safe zone.

A novel rat tail disc degeneration model induced by static bending and compression

Background

A new rat tail intervertebral disc degeneration model was established to observe the morphologic and biologic changes of static bending and compression applied to the discs.

Methods

In total, 20 Sprague-Dawley rats with similar weight were randomly divided into 4 groups. Group 1 served as a control group for a baseline assessment of normal discs. Group 2 underwent a sham surgery, using an external device to bend the vertebrae of coccygeal 8-10. Groups 3 and 4 were the loaded groups, and external devices were instrumented to bend the spine with a compression level of 1.8 N and 4.5 N, respectively. Magnetic resonance imaging (MRI), histological, and quantitative real-time PCR (qRT-PCR) analysis were performed on all animals on day 14 of the experiment.

Results

Magnetic resonance imaging and histological results showed that the changes of intervertebral disc degeneration increased with the size of compression load. Some architecture disorganizations in nucleus pulposus and annulus fibrosus were found on both of the convex and concave side in the groups of 1.8 N and 4.5 N. An upregulation of MM-3, MM-13, and collagen 1-α1 mRNA expression and a downregulation of collagen 2-α1 and aggrecan mRNA expression were observed in the sham and loading groups. Significant changes were found between the loading groups, whereas the sham group showed similar results to the control group.

Conclusions

Static bending and compression could induce progressive disc degeneration, which could be used for biologic study on disc degeneration promoted by static complex loading.

Effects of School Backpacks on Spine Biomechanics During Daily Activities: A Narrative Review of Literature

OBJECTIVE

The purpose of this narrative review is to summarize the effects of carrying school backpacks on spine and low-back biomechanics as a risk factor for low back pain in young individuals.

BACKGROUND

Backpacks constitute a considerable daily load for schoolchildren. Consistently, a large number of children attribute their low back pain experience to backpack use.

METHOD

A literature search was conducted using a combination of keywords related to the impact of carrying backpacks on lower back biomechanics. The references of each identified study were further investigated to identify additional studies.

RESULTS

Twenty-two studies met inclusion criteria. A total of 1,159 people aged 7 to 27 years were included in the studies. The added load of a backpack and the changes in spinal posture when carrying a backpack impose considerable demand on internal tissues and likely result in considerable spinal loads. The findings included results related to the effects of backpack weight and position on trunk kinematics and spine posture as well as trunk muscle activity during upright standing, walking, and ascending and descending stairs.

CONCLUSION

Backpack-induced changes in trunk kinematics for a given activity reflect alterations in mechanical demand of the activity on the lower back that should be balanced internally by the active and passive responses of lower back tissues. Although the reported alterations in trunk muscle activities and lumbar posture are indications of changes in the active and passive response of the lower back tissues, the resultant effects on spinal load, that is, an important causal factor for low back pain, remains to be investigated in the future. A knowledge of backpack-induced changes in spinal loads can inform design of interventions aimed at reduction of spinal load via improved backpack design or limitation on carrying duration.

APPLICATION

This narrative review is intended to serve as an educational article for students and trainees in ergonomics and occupational biomechanics.

Perinatal factors associate with vertebral size and shape but not lumbar lordosis in 10-year-old children

The intrauterine environment is known to influence foetal development and future health. Low birthweight has been linked to smaller vertebral canals in children and decreased adulthood spine bone mineral content. Perinatal factors affecting lumbar spine curvature have not yet been considered but could be important for adult spinal health, as lumbar movement during lifting, a risk factor for backpain, is associated with lordosis. To investigate this, lumbar spine magnetic resonance images at age 10 years and perinatal and maternal data (birthweight, placental weight, gestation length, crown-heel length, maternal age, height, weight and smoking status) from 161 children born in Aberdeen in 1988-1989 were acquired. Statistical shape modelling, using principal component analysis, quantified variations in lumbar spine shape and resulting modes of variation were assessed in combination with perinatal data using correlations and analyses of covariance, adjusted for potential confounders. Spine modes 1-3 (SM1-SM3) captured 75% of the variation in lumbar spine shape. The first and third modes described the total amount (SM1) and evenness of curvature distribution (SM3). SM2 accounted for variations in antero-posterior vertebral diameter relative to vertebral height, increasing positive scores representing a larger relative diameter. Adjusting for gestation length and sex, SM2 positively correlated with birthweight (r = 0.25, P < 0.01), placental weight (r = 0.20, P = 0.04), crown-heel length (r = 0.36, P < 0.001) and maternal weight (r = 0.19, P = 0.04), and negatively with maternal age (r = -0.22, P = 0.02). SM2 scores were lower in girls (P < 0.001) and in the low birthweight group (P = 0.02). There were no significant differences in SM1 and SM3 scores between birthweight groups, boys and girls or children of smokers (31%) and non-smokers (69%). In conclusion, some perinatal factors were associated with vertebral body morphology but had little effect on lumbar curvature.

Lumbar spine angles and intervertebral disc characteristics with end-range positions in three planes of motion in healthy people using upright MRI

Understanding changes in lumbar spine (LS) angles and intervertebral disc (IVD) behavior in end-range positions in healthy subjects can provide a basis for developing more specific LS models and comparing people with spine pathology. The purposes of this study are to quantify 3D LS angles and changes in IVD characteristics with end-range positions in 3 planes of motion using upright MRI in healthy people, and to determine which intervertebral segments contribute most in each plane of movement. Thirteen people (average age = 24.4 years, range 18-51 years; 9 females; BMI = 22.4 ± 1.8 kg/m²) with no history of low back pain were scanned in an upright MRI in standing, sitting flexion, sitting axial rotation (left, right), prone on elbows, prone extension, and standing lateral bending (left, right). Global and local intervertebral LS angles were measured. Anterior-posterior length of the IVD and location of the nucleus pulposus was measured. For the sagittal plane, lower LS segments contribute most to change in position, and the location of the nucleus pulposus migrated from a more posterior position in sitting flexion to a more anterior position in end-range extension. For lateral bending, the upper LS contributes most to end-range positions. Small degrees of intervertebral rotation (1-2°) across all levels were observed for axial plane positions. There were no systematic changes in IVD characteristics for axial or coronal plane positions.

The effects of backpack type on lumbo-pelvic coordination during trunk bending and return tasks

Backpacks with ergonomic features are recommended to mitigate the risk of developing low back pain due to carrying a heavy school backpack. A repeated measure study was conducted on 40 college-age students to investigate the immediate changes in magnitude and timing aspects of lumbo-pelvic coordination when carrying an ergonomically modified vs. a normal backpack relative to no backpack condition during trunk forward bending and backward return tasks. We found a smaller reduction in the thoracic range of rotation, an increase vs. a decrease in pelvic range of rotation and a larger reduction in lumbar flexion for a modified vs. a normal backpack. Furthermore, during the forward bending, a less in-phase motion for the modified backpack was observed. Our results suggest that participants have likely experienced larger spinal loads with the modified backpack; a conclusion that should be investigated in future to determine whether ergonomic backpacks can reduce the risk of low back pain in children. Practitioner summary: Research participants performed trunk bending and return closer to their habitual way under modified versus normal school backpack. From an equilibrium point of view, therefore, individuals are likely experiencing larger spinal loads during activities of daily living with a modified backpack. However, such a conclusion may change when considering stability requirements.

A model-based approach for estimation of changes in lumbar segmental kinematics associated with alterations in trunk muscle forces

The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental kinematics of lumbar spine was estimated for a single static trunk flexed posture involving, respectively, 40° and 10° of thoracic and pelvic rotations. Minimum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 0° to 0.7° and 0 mm to 0.04 mm, respectively. Maximum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 2.4° to 7.6° and 0.11 mm to 0.39 mm, respectively. The differences in kinematics of lumbar segments between each combination of two sets of TMFs in 97% of cases for angular deformation and 55% of cases for translational deformation were within the reported accuracy of current imaging techniques. Therefore, it might be possible to use image-based kinematics of lumbar segments along with computational modeling for personalized assessment of TMFs.

Ergonomics evaluation of school bags in Tehran female primary school children

BACKGROUND

More than 90% of the elementary school students in the world and most of the Iranian students use backpacks. Heavy school bags, failure to apply ergonomics standards in student's backpacks, and also mismatch between anthropometrics dimensions and schoolbag size are important issues for children's health.

OBJECTIVE

The purpose of this study was to gather baseline information on the average weight carried by female primary students. It also aimed to evaluate ergonomics standards for student backpacks.

METHODS

A cross-sectional study was conducted on 212 Iranian girl students aged 6- 11 years. Body weight and bag weight were measured with electronic scales and body mass index calculated with WHO software 2007. A questionnaire was constructed to gather information about the backpacks. Body dimensions were measured with VICON motion Analyze system (460). Ergonomics factors were recorded using a checklist.

RESULTS

80.8% of the students used a backpack at a higher weight than recommended by the standards of 10% of body weight. The most common type of schoolbag used was double strap packs (92.5%). The majority of the students carried packs on their backs; however, most of them did not make any adjustments (79.8%). The results have shown a mismatch between the anthropometric measures and the student's backpack dimensions.

CONCLUSIONS

Parents, students and school staff should be informed about these critical issues as well as suitable controls should be implemented in buying and using the bags.

The fabrication of cryogel scaffolds incorporated with poloxamer 407 for potential use in the regeneration of the nucleus pulposus

Degeneration of the nucleus pulposus (NP) is the primary cause of back pain in almost 80% of the world population. The current gold standard treatment for a degenerated NP is a spinal fusion surgery which is costly, temporary, and extremely invasive. Research has been moving towards minimally invasive methods to lessen the collateral damage created during surgery. The use of a tissue-engineered scaffold has the potential to promote a healthy and hydrated environment to regenerate the NP. Cryogels are unique polymeric scaffolds composed of a highly connected, macroporous structure, and are capable of maintaining stability under high deformations. For this study, cryogels have been developed using gelatin and poloxamer 407 (P407) at varying ratios to determine the ideal combination of stability, water retention, and pore size. For the application of NP regeneration, a gelatin-P407 cryogel should be both stable and a well hydrated carrier. The cryogels created varied from a 1:1 gelatin to P407 ratio to a 10:1 ratio. The inclusion of P407 in the cryogels resulted in a significant increase in hydrophilicity, ideal pore size for cell infiltration, mechanical stability over 28 days, and cell infiltration after just 21 days. This novel gelatin-P407 composite cryogel has the potential to be a practical alternative to the spinal fusion procedure, saving patients hundreds of thousands of dollars and, ideally, leading to improved patient outcome.

Effect of Backpack Strap Patterns on Gait Parameters in Young Adults at Self-Selected Normal and Fast Walking Speeds

BACKGROUND

The effects of backpack load on young adults' gait parameters have received little attention. We previously reported that with a backpack load within 15% body weight (BW), young adults maintain their gait parameters at the expense of increased exertion during a 6-minute walk at self-selected normal walking speed. However, the effect of backpack strap pattern on gait parameters during faster walking or longer stride length has not been evaluated.

OBJECTIVE

To determine the effect of different backpack strap patterns on gait parameters during a 12-minute walk test in young adults at self-selected normal and fast walking speeds.

DESIGN

A crossover, self-controlled experimental study with repeated measures.

SETTING

Department of Medical Rehabilitation, University of Nigeria.

PARTICIPANTS

A convenience sample of 24 healthy young adults (21.29 ± 1.20 years) who voluntarily signed an informed consent form, were able to wear a backpack on 1 and on both shoulders, were able to walk independently, and passed the physical activity readiness screening participated in this study.

METHODS

Using a validated method of an observational gait analysis, each participant carried out a 12-minute walk test at self-determined normal and fast walking speeds, respectively. The effect of the following test conditions on the selected gait parameters was evaluated: normal and fast walking without load, and normal and fast walking with 10% and 20% BW backpack carried each on 1 and both shoulders.

MAIN OUTCOME MEASUREMENT

Stride length, stride time, velocity, cadence, and base of support were assessed by the equation definitions method of the velocity field diagram.

RESULTS

At self-selected fast walking speed with 10% BW backpack load, stride time (P = .004) and cadence (P = .006) were significantly decreased when participants wore a double-strap backpack. At self-selected normal walking speed with 20% BW backpack load, cadence was significantly decreased with double-strap backpack carriage (P = .008). Cadence (P < .001), velocity (P < .001), and stride time (P < .001)were also significantly decreased at both conditions of single and double-strap backpack carriage of 20% BW respectively at fast walking speed.

CONCLUSION

Backpack strap patterns do not affect the gait parameters of young adults in a 12-minute bout of normal walking speed, provided that the load is less than 20% BW. However, a load up to 10% BW carried on a double strap causes a decrease in stride time and cadence when these individuals walk fast.

LEVEL OF EVIDENCE

Not applicable.

Upright magnetic resonance imaging of the lumbar spine: Back pain and radiculopathy

BACKGROUND

Lumbar back pain and radiculopathy are common diagnoses. Unfortunately, conventional magnetic resonance imaging (MRI) findings and clinical symptoms do not necessarily correlate in the lumbar spine. With upright imaging, disc pathologies or foraminal stenosis may become more salient, leading to improvements in diagnosis.

MATERIALS AND METHODS

Seventeen adults (10 asymptomatic and 7 symptomatic volunteers) provided their informed consent and participated in the study. A 0.6T upright MRI scan was performed on each adult in the seated position. Parameters were obtained from the L2/3 level to the L5/S1 level including those pertaining to the foramen [cross-sectional area (CSA), height, mid-disc width, width, thickness of ligamentum flavum], disc (bulge, height, width), vertebral body (height and width), and alignment (lordosis angle, wedge angle, lumbosacral angle). Each parameter was compared based on the spinal level and volunteer group using two-factor analysis of variance (ANOVA). Bonferroni post hoc analysis was used to assess the differences between individual spinal levels.

RESULTS

Mid-disc width accounted for 56% of maximum foramen width in symptomatic volunteers and over 63% in asymptomatic volunteers. Disc bulge was 48% greater in symptomatic volunteers compared to asymptomatic volunteers. CSA was generally smaller in symptomatic volunteers compared to asymptomatic volunteers, particularly at the L4-L5 and L5-S1 spinal levels. Thickness of ligamentum flavum (TLF) generally increased from the cranial to caudal spinal levels where the L4-L5 and L5-S1 spinal levels were significantly thicker than the L1-L2 spinal level.

CONCLUSIONS

The data implied that upright MRI could be a useful diagnostic option, as it can delineate pertinent differences between symptomatic volunteers and asymptomatic volunteers, especially with respect to foraminal geometry.

Correlations between Muscle Activities and Strap Length and Types of School Bag during Walking

[Purpose] The purpose of this study was to examine correlations between muscle activities and strap length and type of the school bag during walking. [Subjects and Methods] The subjects of this study were 20 healthy students. An 8-channel electromyograph (8-EMG) (Pocket EMG, BTS, Italy) was used to measure the muscle activities of the right upper trapezius, left upper trapezius, right erector spinae and left erector spinae during walking with the bag. The collected data were analyzed using Kendall’s coefficient of concordance. [Results] The muscle activities of the right upper trapezius, left upper trapezius, right erector spinae and left erector spinae were significantly higher when walking with a shoulder bag than when walking with a backpack. No significant correlations were found between muscle activities and strap lengths of the bag. [Conclusion] While carrying a bag, the activities of the trunk muscles were influenced more by the type of the bag than by the strap length. These results indicate that a backpack is a better method of carrying a load than a shoulder bag.