Heavy school bags damaging children’s spines – new study

Packing children’s school bags with heavy stuff is likely to injure their spines, a new study, “Backpack Forces on the Spine” conducted by a team of American researchers led by Dr Kenneth K Hansraj, has revealed.
Dr Hansraj is a spinal and orthopaedic surgeon at the Vassar Brothers Medical Centre, Hudson Valley, New York, US. He specialises in, among other things, cervical, thoracic and lumbar procedures.

Dr Gonza Waiswa, an orthopaedic surgeon at Mulago National Referral Hospital, on Thursday said it was possible to injure one’s spine by carrying heavy loads, but hastened to add that he had not treated any such cases among children.
“I have not yet got any cases of children’s spines being injured as a result of carrying a heavy school bag or heavy loads, but I know that it is a possibility,” he said.

Outcomes of previous research had revealed that use of backpacks or school bags was responsible for alteration of the way in which people walk and influencing their body postures.
It has also been known to cause back and neck pains, disc compression and plantar foot pressure.
It also indicated that the number of straps on a school bag did not have any influence on the child’s gait, but adds that lack of symmetry leads to measurable postural changes and diminishing function of the lungs.

That research was, however, focused on the impact of the forces exerted by backpacks on load distribution, back pain and gait and suggested that it was safe for children and adolescents to carry backpacks of up to 10 per cent of their body weight.
It was also considered alright for young adults to carry loads of up to 13 per cent of their body weights and college aged adults between 15 and 20 per cent of their body weights.
Dr Hansraj’s research was carried out to assess the effects of incremental backpack loads on the spine and entailed conducting an analysis on model human spines loaded with backpacks of different sets of weights.

In one scenario, the model spine was placed in a regular posture while the spine was tilted forward by 20 degrees in the second scenario before weights were incrementally placed on the spines. Backpack weights ranging from 0.45kgs to 45.36kgs were used.
The findings revealed that the axial compression pressure on the spine that had been put in a natural postures was 7.2times the weight of the backpack. This means every 10kg backpack exerted about axial compression pressure amounting to 72kgs.

Axial compression
The findings established that axial compression pressure on the spine that had been put in forward leaning position was 11.6 times more than the size of the backpack. Which means that an axial compression pressure amounting to 116kg was placed on that spine.
Axial compression is a type of force or pressure exerted on a body causing it to experience shear stress and bending.
Going by the above calculations, a 12-year-old boy who carries a school bag packed with books and break time goodies amounting to 5kg could be exerting pressure amounting to anywhere between 36kgs and 58kgs on his little back.

A vertebral bone can withstand an average stress of from 100 to 250 Megapascal (MPa) before fracture. Megapascal is a metric pressure unit and equals to a million force of neutrons per square metre.
Dr Hansraj’s research reviewed that a 22.6kg backpack exerted about 1.21Mpa on the spine in a neutral position and about 32.2Mpa on the spine in a forward leaning position, while a 45kg backpack exerts pressure of twice the previous figure.

Britain. In October last year, Spalding Grammar School banned the use of school bags for health and safety reasons. Sixth formers (students in the last year of high school) were ordered to stop carrying bags between classes on grounds that it was causing them injury.

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