Page 91 - Journal of Special Operations Medicine - Winter 2016

through 2015. However, the number of these cases that Figure 1 The brachial plexus showing the cervical and
were related to load carriage cannot be determined be- thoracic roots, trunks, and division in the descending
cause the activities associated with the injury are not pathways. In rucksack palsy, the heavily loaded shoulder
included in the database. straps of the rucksack cause a traction or compression injury,
stretching or irritating the nerves of the brachial plexus.
Besides paresthesia, symptoms of brachial plexus palsy
can include paralysis, cramping with pain, and muscle
weakness. Pain is experienced in the shoulder girdle and
may also extend to the neck, arm, and hand. The pares-
thesia and pain usually progress in intensity with longer
load carriage time, but after the load is removed, the
pain is reduced or absent, although sensory deficits and
muscular weakness remain. 3,4,9,17,18,22 The sensorimotor
deficits are usually temporary, but because symptoms
can occur during a load-carriage task, 7,17 this injury has
tactical implications. The upper-limb paresthesia and
weakness can impact the ability of a Soldier to use their
personal weapons. Operationally, the lengthy recovery
3
time for the injury can remove Soldiers from training Source: http://bookbing.org/multiple-root-avulsions-from-the
programs and operational duties; the disorder can also -brachial-plexus/.
result in chronic conditions. In one case series of 38
Finnish recruits with diagnosed brachial plexus palsy, Figure 2 Scapular winging in a Soldier, as sometimes seen in
79% reported they were asymptomatic within a median association with rucksack palsy. Note that on the right side,
3 months of symptom onset (range, 0–9 months). At the medial border of the scapula is more posterior due to
9
4.5 years of follow-up, 21% had prolonged symptoms. weakness of the right serratus anterior muscle, which would
normally hold the medial border of the scapula against the
Of the total sample of 38 recruits, the disorder led to a chest wall. The muscle is weakened by nerve injury associated
change in Soldiers’ service qualification in seven cases with rucksack palsy.
(18%), affected the Soldier’s profession after the Army
in five cases (13%), and led to decreased physical activ-
ity after the Army in five cases (13%). 9

Brachial plexus palsy associated with load carriage ap-
pears to be primarily caused by rucksack shoulder straps.
Heavy loads on the shoulder cause a traction or com-
pression injury of the nerve trunks of the upper brachial
plexus (Figure 1). In some cases, compression results in
entrapment of the long thoracic nerve, which originates
from the nerve roots before the brachial plexus trunks
forms (Figure 1). Long-thoracic-nerve injuries usually
present with “scapular winging” (Figure 2), where the
medial border of the scapula protrudes posteriorly, lift-
ing away from the rib cage. Scapular winging is caused
by weakness in the serratus anterior muscle, which is Source: http://www.bhamknee-shoulder.co.uk/mobile/patient
3,7
-information/shoulder/other-problems.
innervated by the long thoracic nerve and can negatively
impact on shoulder mobility and control. 23 may also contribute, with this tension sometimes related
to posture and to nerve mobility being impeded at the
One study of recruits found that those with lower body nerve interface with surrounding neck and soft-tissue
mass index (BMI) were more likely to be diagnosed with structures. 25,26 It could also be caused by a neurologic
backpack palsy or experience postmarch shoulder pares- “thoracic outlet syndrome,” which sometimes is caused
thesia than recruits with higher BMI. Age and physical by an additional cervical rib. The latter is rare, with
18
26
fitness do not appear to be associated with the injury. 9,17 <1% of individuals having the extra rib and only about
Other hypothetical risk factors for rucksack palsy in- 10% of these developing symptoms. Nonetheless, both
26
clude load weight and longer carriage distances. 3,4,15,24 preexisting tension and the possibility of an additional
Muscle-strength losses arising from a rucksack palsy cervical rib should be considered as early as possible.
appear to be greater in those carrying heavier loads. 9,22 Note that actual rucksack palsy will generally involve
Preexisting tension in the brachial plexus nerve tissue the upper brachial plexus, whereas a thoracic outlet

Load-Carriage Paresthesias: Part 1 75