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Nerve Injuries From Heavy Backpacks in Soldiers

Backpack palsy is an increasing problem among military soldiers. The average load they carry is over 100 pounds. Backpacks can get as heavy as 175 pounds. The weight compresses or stretches the nerves to the arm. Soldiers report numbness, weakness, and paralysis. Pain is not a problem at first but can develop later.

In this retrospective study of 152,095 Finnish soldiers, researchers looked for risk factors for brachial plexopathy. Retrospective means they looked back over the medical records of the soldiers after the problem was diagnosed. Brachial plexopathy is another way to say nerve palsy involving the brachial plexus. The brachial plexus is the main group of nerves in the neck and arm.

Each soldier’s height, weight, and physical fitness was evaluated as a possible risk factor for backpack palsy. Results of electromyography (EMG) muscle test and nerve conduction tests were reviewed. Training and background for each recruit were also studied.

The results showed that backpack palsy affects about 54 soldiers out of every 100,000 soldiers. Different nerves in the brachial plexus were affected in the group. Brachial plexopathy occurred in soldiers carrying a backpack with and without a frame. Heavier loads carried for longer periods of time were more likely to cause a problem.

Height, weight, and fitness level were not linked with nerve palsy. A few soldiers had a hereditary condition. Overall, the incidence of nerve palsy from carrying heavy backpacks is low among Finnish soldiers.

Many people believe a backpack with a frame and waist belt prevents these types of nerve injuries. This study does not support that idea. This style of backpack pulls the shoulders back enough to compress the long thoracic nerve.

The authors offer some suggestions for ways to improve backpack design. Adjustable shoulder straps may help each soldier find the right amount of pull for his or her body build and posture. Horizontal sternum straps across the upper chest might help reduce the back and downward pull on the shoulders.
More studies are needed to find a better design for heavy backpacks carried by military personnel. Soldiers who are strong and in good condition should not be asked to carry heavier loads on long marches.

References: Jyrki P. Mäkelä, MD, PhD, et al. Brachial Plexus Lesions After Backpack Carriage in Young Adults. In Clinical Orthopaedics and Related Research. November 2006. No. 452. Pp. 205-209.

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