Backpack Carriage and Low Back Pain in Schoolchildren and Adolescents
- Physiology of schoolchildren and adolescent spine
- Low back pain & prevalence in younger population
- Anatomy of paediatric spine
- Backpack trends
- Biopsychosocial model
- Relationship between backpack carriage and back pain
- Explore into backpack load, load position and carriage style
- Relevance to physiotherapy
- Areas for further research
Paediatric and adult spine differences:
- Increase cartilage/ bone ratio.
- Presence of soft tissue elasticity, muscle weakness and incomplete ossification means greater ROM available.
- Vertebral bodies in paediatric spine are partly cartilaginous.
- Intervertebral disc spaces are larger, and are well hydrated.
- Vertebral apophyses develop at the inferior and superior surfaces of the vertebral bodies. These appear by 5 years of age and fuse by 18-20.
- Low back pain is not a disease but a collection of symptoms .
- Pain limited to the region between the lower margins of the 12th rib and the gluteal folds .
- LBP can be classified into two types; non-specific and specific.
- LBP can be further characterised into three subtypes: acute, subacute and chronic .
- Major health issues with a lifetime prevalence of 80% 
- Prevalence rate would increase with age (16% for children and 58% for adolescents) .
- Self-reported prevalence of back pain was 27%, 37% and 47% among children aged 11, 13 and 15 years, respectively 
- The estimated annual cost of chronic low back pain in adolescents aged 10-17 in the US was $19.5 billion .
- Most common way - 2 straps
- Carriage styles: 2 straps/ 1 strap/ wheeled 
- Variation regarding recommendations for children and adolescents carrying schoolbags.
- Safe loads are mostly within 10%–15% of body weight (BW) range but include values as low as 5%14 and as high as 20%.
The biopsychosocial model proposed by George Engel in 1977 highlights the significance of taking on a medical care path that not only considers the biological aspects of medicine, but also the psychological and social dimensions of a patient. This model implies that behaviours, feelings and thoughts may influence a physical state.
Common occurrence of non-specific back pain in schoolchildren and adolescents has led to research exploring into mechanical and physical factors that could possibly explain why such phenomenon occurs. Over the years, it has been thought that external mechanical load of a backpack is one of the major factors that contribute to back pain in children and adolescents. This page will explore into the relationship between backpack carriage and low back pain in schoolchildren and adolescents. Furthermore, the psychosocial factors will also be considered.
Back pack weight has traditionally been postulated to increase the risk factor for eliciting low back pain, despite no high quality evidence supporting this claim. The literature that have supported these claims have provided recommendations on backpack load ranging as low as 5%  body weight, rising up to 20% . One study has even suggested that 10% of body weight can be enough to cause changes to posture, kinematics and muscular strain .
A recent systematic review published in 2018 aimed to identify this relationship by searching for studies looking into backpack characteristics and it's association to back pain  . This review gathered 69 studies in total, 5 of which being prospective in design (4 longitudinal cohort, 1 randomised controlled trial), 63 being cross-sectional, and one retrospective case-control study. The general consensus found there to be very little evidence to suggest the relationship between backpack weight and back pain is positive. Of the studies supporting the claim, all were of moderate to low quality, including studies that focused on the perception of backpack weight. A huge limitation to this study is that not all P-values/ confidence intervals were included, also, the vast majority of studies were moderate to low in quality.
Backpack Load Position
In addition to the load of the backpack weight, literature have stated that the position of a backpack may also influence the efficiency of posterior load carriage . Efficient load carriage is associated with minimal energy expenditure and minimal anti-gravity stress on spinal tissues, and is believed to occur when an individual is in an unloaded state, where the anatomical body is aligned with the vertical reference closely . Application of external load to the body is commonly associated with deviation of the spine (posture affected at times), away from the gravitational axis, which is believed to be a cause of spinal pain .
Limited research has been conducted examining specifically on the relationship between low back pain and the effects of backpack load position, especially in schoolchildren and adolescents. A randomised crossover trial published in 2018, examined the effects of backpack load and position on body strains in male schoolchildren . It examined three different load positions, where the midline of the backpack was at either T7, T12 or L3 spinous process level. where From the results, the study had recommended to place centre of backpack at T12 level to reduce discomfort and to avoid a less fixed upper body. However, the limitations to this study is that it was conducted in a male-sex only population and had a a small sample size of 10 (unpowered) participants. Therefore, it is difficult to generalise these findings. Larger study groups are needed in future studies to increase external validity.
Backpack Carriage Style
Evidence suggests that when a backpack is carried on one shoulder, this may lead to a potential change in the spine as the spine may side flex in order to compensate for the load. For example, when the unilateral load of the backpack is put on the right side, an increase in the right side flexion may occur. Similarly, if the unilateral load of the backpack is on the left, an increase in left side flexion may occur. The increase in the side flexion may result in compensatory side flexion of the body in an opposite direction to the load to compensate it . However, there is limited contemporaneous, high-quality evidence investigating the impact of backpack carriage method on low back pain and no direct link between them has been established.
In general, spinal curvature or muscle spasm due to a minimal change in posture may result in the inflammation of supporting structures of the spine such as joints, muscles and ligaments . The carriage style, therefore, may contribute to the occurrence of back pain.
- A literature review summarised there was inconsistent evidence to show the relationship between backpack carriage method and back pain in children and adolescents. However, the nature of a literature review is of a low level of evidence .
- A recent systematic review stated that only 3 out of 29 cross-sectional studies found an association between the method of backpack carriage and backpack. However, it concluded that there was no clear association. The studies investigated on a combination of backpack characteristics, such as backpack weights and duration of backpack use. Hence, it was difficult to identify the impact in specific to the carriage position.
- No convincing evidence to show backpack use increase the risk of back pain
- No clear association between backpack characteristics (weight, style and strap length) and back pain.
- Good evidence to suggest psychosocial factors or distress may have an impact on back pain in children and adolescents 
Relevance to Physiotherapy
- Provide advice and education on backpack carriage and beliefs
- The bigger picture:
- Consider and explore into psychosocial factors in patients with back pain who are under 18 e.g. stress
- Consider lifestyle risk factors e.g. smoking, weight
Areas for Further Research
- Higher quality of evidence required
- High quality study design to increase generalisability
- Further research on the impact of psychosocial factors on back pain in schoolchildren and adolescents
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