Brachial plexus lesions after backpack carriage in young adults

The effects of shoulder morphology on the distribution of shoulder pressure during load carriage

To enhance the prevention of shoulder pressure injuries in various load-bearing populations, the effects of shoulder morphology on pressure distribution were investigated. In this study, 69 participants underwent three-dimensional scanning, and based on shoulder morphological characteristic indicators, they were classified into four shoulder types. From these, 28 participants were selected to have the pressure within shoulder regions measured using a pressure-sensing vest while carrying a backpack load equivalent to 15% of their body weight. The results indicated that variations in shoulder morphology significantly impact pressure distribution. The greater bumpiness of the shoulder surface contributed to pressure concentration at specific points, resulting in uneven pressure distribution. The enhanced fullness of the shoulder surface promoted even pressure dispersal across the area. This study provided a theoretical basis for developing more effective shoulder injury prevention and management strategies tailored to load-bearing populations with different shoulder types.

Coupled effect of load weights and belt use on male shoulder pressure redistribution

Shoulder pressure redistribution is jointly affected by backpack loads and belt support. However, the combined effect of both factors has rarely been fully evaluated. Here, we studied the coupled effect of backpack loads and belt support on shoulder pressure redistribution. All twenty-eight healthy male subjects underwent eight loading conditions with both chest and hip belts fastened (CH) and unfastened (CON) in four conditions where the backpack weighed 7.5, 15, 22.5, and 30% of body weight (BW). Shoulder pressure distribution was quantified through a pressure-sensing vest mat. The results showed that using the hip belt and chest belt was effective in relieving the high pressure in the lateral clavicle and medial trapezius region and strengthening the load-bearing capacity of shoulder. However, the assistance in pressure relief of using belt was weakened when load increased to 30% BW. This study also showed that the belt use can be effective in improving pressure asymmetry on both sides.

Axillary and musculocutaneous neuropathies

This chapter covers axillary and musculocutaneous neuropathies, with a focus on clinically relevant anatomy, electrodiagnostic approaches, etiologic considerations, and management principles. Disorders of the lateral antebrachial cutaneous nerve, a derivative of the musculocutaneous nerve, are also reviewed. We emphasize the importance of objective findings, including the physical examination and electrodiagnostic evaluation in confirming the isolated involvement of each nerve which, along with the clinical history, informs etiologic considerations. Axillary and musculocutaneous neuropathies are both rare in isolation and most frequently occur in the setting of trauma. Less commonly encountered etiologies include external compression or entrapment, neoplastic involvement, or immune-mediated disorders including neuralgic amyotrophy, postsurgical inflammatory neuropathy, multifocal motor neuropathy, vasculitic neuropathy, and multifocal chronic inflammatory demyelinating polyradiculoneuropathy.

Evaluation of an ergonomically designed schoolbag: Heart rate variability and body discomfort rating

BACKGROUND: Unsuitable schoolbags may stress the spine and promote poor body posture, particularly for school students. Global recommendations have suggested that schoolbag weight must not exceed 10% of a healthy student’s body mass, which would need continuous monitoring and enforcement. OBJECTIVES: The present study presents a comparison between an ergonomically designed schoolbag, which helps reduce the potential effects of carrying a load, and a commercial one. METHODS: A total of 30 healthy male students were recruited for this experiment. Independent variables determined were schoolbag type (ergonomically designed and commercial schoolbags) and three load levels based on body mass percentage (i.e., 10%, 15%, and 20% of body mass). Heart rate variability (HRV) and body discomfort rating were then measured. RESULTS: Our results showed that the developed schoolbag promoted enhanced subjective measures and HRV response at 15% and 20% of body mass. Participants who wore the developed schoolbags experienced significantly lesser neck, shoulder, upper and lower trunk discomfort than those who wore the traditional ones. Changing the load percentage from 10% to 15% caused an increase in heart rate among participants carrying a commercial schoolbag but a decrease in heart rate among those carrying the developed schoolbag. CONCLUSIONS: The findings presented herein suggest introducing strategies for reducing the potential impact of load carrying through the combined effect of new educational inventions and policy changes.

Impact of Backpacks on Ergonomics: Biomechanical and Physiological Effects: A Narrative Review

(1) Background: the effects of load carriage packs on human gait biomechanics, physiology and metabolism depend on the weight carried, the design of the pack and its interaction with the user. (2) Methods: An extensive search in the PubMed database was performed to find all the relevant articles using the following keywords: backpack, rucksack, backpack ergonomy and sports backpack; 60 articles were included. (3) Results and significance: Double pack (DP) and T-pack (TP) designs are recommended solutions for school children, compared with backpacks (BP). For soldiers and hikers, a backpack remains the best compromise. A hip belt is recommended for BPs as well as for the back of DPs. Shorter and stiffer shoulder straps combined with a higher and tighter load placement on the back provide the best combination in terms of balance, muscle activation and energy expenditure. It is, therefore, possible to determine guidelines for designing the optimal load carriage system, depending on the application. (4) Conclusions: based on the available evidence, DP and TP are advantageous in terms of posture. DP is better than conventional BPs in terms of balance and muscle activation, but has the disadvantage of limited visibility, thermal sensation and obstructed ventilation. In general, it is desirable not to exceed 40% of body mass (BM).

Upper limb manual dexterity, strength and blood flow after walking with backpack load

This study aimed to characterize the effects of walking with backpack load on upper limb function. Fifteen males participated in 3 conditions: no load, 40% body weight loaded backpack (BP) and loaded backpack with simulated rifle (BRC). Pinch strength, grip strength, sensory threshold, blood flow volume, and a manual dexterity test were assessed before and after a 45-min walking trial. Pinch strength in the BP condition was significantly different than the control (p < 0.05). Grooved pegboard times were faster after a seated recovery (p = 0.026) than immediately after walking with load. Blood flow was significantly decreased to <53% of baseline (p ≤ 0.001) in BP and BRC immediately after donning the backpack. No significant changes in grip strength or sensory threshold were measured among conditions or time points. In conclusion, pinch strength, manual dexterity and blood flow were affected by backpack carriage, but other upper limb measures remained unaffected.

Isolated Mononeuropathy From Rucksack Palsy: A Case Series

Although there is increasing awareness of brachial plexopathy secondary to rucksack use, isolated mononeuropathies have been less well described. Three cases of mononeuropathy secondary to rucksack use in military personnel are presented, including injuries to the long thoracic and spinal accessory nerves. We also review several different factors in the proper construction, components, and fitting of the rucksack that should be considered in order to prevent rucksack palsy and provide a concise suggestion for rucksack use and education.

Soldier Load Carriage, Injuries, Rehabilitation and Physical Conditioning: An International Approach

Soldiers are often required to carry heavy loads that can exceed 45 kg. The physiological costs and biomechanical responses to these loads, whilst varying with the contexts in which they are carried, have led to soldier injuries. These injuries can range from musculoskeletal injuries (e.g., joint/ligamentous injuries and stress fractures) to neurological injuries (e.g., paresthesias), and impact on both the soldier and the army in which they serve. Following treatment to facilitate initial recovery from injuries, soldiers must be progressively reconditioned for load carriage. Optimal conditioning and reconditioning practices include load carriage sessions with a frequency of one session every 10-14 days in conjunction with a program of both resistance and aerobic training. Speed of march and grade and type of terrain covered are factors that can be adjusted to manipulate load carriage intensity, limiting the need to adjust load weight alone. Factors external to the load carriage program, such as other military duties, can also impart physical loading and must be considered as part of any load carriage conditioning/reconditioning program.

Development and Experimental Verification of an Ergonomic Backpack

Carrying a heavy school backpack has extensively been reported as a prime cause of children's body strain. It is suggested that the load should not exceed 10 percent of the child's body weight; however, ensuring this requires continuous monitoring. The study explores how ergonomically designed school backpack based on the user anthropometric data (n = 280) and ergonomic parameters help reduce force concentration on shoulders and back. It provides a validation process of the developed prototype by experimental verification. The developed design was assessed in a comparison experiment with a commercially available local school backpack. An experimental study was used which recruited thirty healthy college students (aged 19 to 23 years). Two independent variables evaluated were school backpack type (developed backpack versus commercial one) and load levels as a percentage of body weight. Three load levels were employed 10%, 15%, and 20%. These variables were measured on the responses: bag comfort scale and the percent of maximum voluntary contraction (%MVC) of six muscles (right and left of erector spine, right and left of external abdominal oblique muscle, and right and left of trapezius). The developed backpack provided astonishing performance at levels of 15% and 20% of body weight in terms of subjective measure and electromyography (EMG) responses. It also showed that increasing the carried weight more than 10% result in reducing activity on the erector spinal muscles, while it increases on abdominal oblique muscles. The developed backpack design confirmed the efficiency of its bases by distributing the carried weight among the trunk through side pockets, attached to the body through two upper and lower straps. It helped the body to distribute the carried weight and avoid concentrating pressure on specific areas.

Backpack palsy and other brachial plexus neuropathies in the military population

Brachial plexus neuropathy is often seen in the military population, especially due to pressure (backpack palsy, BPP) or idiopathic (neuralgic amyotrophy, NA). We aimed to gain insight in the disease characteristics of soldiers with brachial plexus neuropathies in the Dutch military population and to compare disease characteristics between patients with BPP and NA. In this retrospective chart review study we aimed to include all patients with brachial plexus neuropathy, who presented in the Joint Military Hospital between 1 January, 2011 and 31 December, 2016. We calculated the incidence of NA and BPP and Chi-square tests or Student t tests were performed for differences in patient characteristics between NA and BPP. We included 127 patients, 63 with BPP, 45 with NA, 10 with traumatic brachial plexus neuropathy, and 9 with other plexopathy. The incidence of brachial plexus neuropathy was 50/100 000 person years overall, 25/100 000 person years for BPP, and 18/100 000 person years for NA. Patients in the BPP group differed from the NA with regard to pain (BPP 41% vs NA 93%, P = .000), atrophy (13% BPP vs 29% NA, P = .049), and sensory symptoms (83% BPP vs 44% NA, P = .000). In the BPP group 90% had incomplete recovery and in the NA group 78%. Our study showed a high incidence of BPP and NA in the military population and suggests recovery is not so benevolent as previously thought. Future research is necessary to improve insight and outcome of military patients with brachial plexus neuropathies.

Comparison between the Physiological Responses and Subjective Ratings of a Group of Male Students to Three Backpack Designs

It is important for schoolchildren and their parents (or guardians) to know which backpacks exert the least strain on the cardiorespiratory system. In this study, we investigated the physiological responses of participants while they were walking on a treadmill and wearing one of three different backpacks (A, B, and C) under two different load-carrying conditions (equivalent to 10% and 15% of their body mass, respectively). The first condition was used as a control and involved walking without a backpack, while the second involved wearing a backpack and carrying a certain weight. Thirty-one male students from King Saud University walked on a treadmill at 0.861 m/s and at a 0% inclination angle, while having their heart rates (beatsmin⁻¹), oxygen uptakes (VO2, mLmin⁻¹), respiratory rates (breaths, VO2min⁻¹), perceived exertion rates (PER, Borg scale), and backpack preference rates (BPR) measured and recorded. The results of our within-subject experimental design revealed that the physiological results varied significantly depending on the type of backpack. Backpacks B and C were superior to Backpack A, resulting in lower physiological responses and higher subjective preferences. Students carrying more weight experienced higher physiological stress; moreover, the use of Backpack C led to the lowest physiological strains and higher subjective preferences.

Effects of an improved biomechanical backpack strap design on load transfer to the shoulder soft tissues

The aim of the present study was to characterize shoulder strap structure and mechanical properties that may alleviate strains and stresses in the soft tissues of the shoulder. Utilizing a finite element model of the shoulder constructed from a single subject, we have quantified skin stresses exerted by backpack straps and the strains at the subclavian artery (SCA). For this end, standard shape straps with stiffness of 0.5, 1.2, and 5 MPa, were compared to the effects of optimized straps; a double-layered (soft outer layer and reinforced internal supporting layer) and newly-designed anatomically-shaped strap. Compared to the standard 0.5 MPa strap, the 5 MPa strap resulted in 4-times lower SCA strains and 2-times lower Trapezius stresses. The double-layered strap resulted in 40% and 50% reduction in SCA strains and skin stresses, respectively, with respect to the softer strap. The newly-designed anatomical strap exerted 4-times lower SCA strains and 50% lower skin stresses compared to the standard strap. This demonstrates a substantial improvement to the load carriage ergonomics when using a composite anatomical strap.

Integrating a hip belt with body armour reduces the magnitude and changes the location of shoulder pressure and perceived discomfort in soldiers

Soldiers carry heavy loads that may cause general discomfort, shoulder pain and injury. This study assessed if new body armour designs that incorporated a hip belt reduced shoulder pressures and improved comfort. Twenty-one Australian soldiers completed treadmill walking trials wearing six different body armours with two different loads (15 and 30 kg). Contact pressures applied to the shoulders were measured using pressure pads, and qualitative assessment of comfort and usability were acquired from questionnaires administered after walking trials. Walking with hip belt compared to no hip belt armour resulted in decreased mean and maximum shoulder pressures (p < 0.005), and 30% fewer participants experiencing shoulder discomfort (p < 0.005) in best designs, although hip discomfort did increase. Laterally concentrated shoulder pressures were associated with 1.34-times greater likelihood of discomfort (p = 0.026). Results indicate body armour and backpack designs should integrate a hip belt and distribute load closer to shoulder midline to reduce load carriage discomfort and, potentially, injury risk. Practitioner Summary: Soldiers carry heavy loads that increase their risk of discomfort and injury. New body armour designs are thought to ease this burden by transferring the load to the hips. This study demonstrated that designs incorporating a hip belt reduced shoulder pressure and shoulder discomfort compared to the current armour design.

Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment

BACKGROUND

Prosthetic arm research predominantly focuses on "bionic" but not body-powered arms. However, any research orientation along user needs requires sufficiently precise workplace specifications and sufficiently hard testing. Forensic medicine is a demanding environment, also physically, also for non-disabled people, on several dimensions (e.g., distances, weights, size, temperature, time).

METHODS

As unilateral below elbow amputee user, the first author is in a unique position to provide direct comparison of a "bionic" myoelectric iLimb Revolution (Touch Bionics) and a customized body-powered arm which contains a number of new developments initiated or developed by the user: (1) quick lock steel wrist unit; (2) cable mount modification; (3) cast shape modeled shoulder anchor; (4) suspension with a soft double layer liner (Ohio Willowwood) and tube gauze (Molnlycke) combination. The iLimb is mounted on an epoxy socket; a lanyard fixed liner (Ohio Willowwood) contains magnetic electrodes (Liberating Technologies). An on the job usage of five years was supplemented with dedicated and focused intensive two-week use tests at work for both systems.

RESULTS

The side-by-side comparison showed that the customized body-powered arm provides reliable, comfortable, effective, powerful as well as subtle service with minimal maintenance; most notably, grip reliability, grip force regulation, grip performance, center of balance, component wear down, sweat/temperature independence and skin state are good whereas the iLimb system exhibited a number of relevant serious constraints.

CONCLUSIONS

Research and development of functional prostheses may want to focus on body-powered technology as it already performs on manually demanding and heavy jobs whereas eliminating myoelectric technology's constraints seems out of reach. Relevant testing could be developed to help expediting this. This is relevant as Swiss disability insurance specifically supports prostheses that enable actual work integration. Myoelectric and cosmetic arm improvement may benefit from a less forgiving focus on perfecting anthropomorphic appearance.

Muscle training-induced bilateral brachial plexopathy in an adolescent with sporadic hereditary neuropathy with liability to pressure palsies

There have been few studies regarding physical training-induced peripheral nerve dysfunction in patients with hereditary neuropathy with liability to pressure palsies (HNPP), with the exception of soldiers that trained intensively. Here, we report a 15-year-old boy without family history of HNPP who developed bilateral painless brachial plexopathy following short-term barbell and plank training during a school baseball club activity. Muscle training-induced painless brachial plexopathy could be an initial symptom and may be underdiagnosed in adolescents with sporadic HNPP.

Backpack palsy with Horner's syndrome

Traumatic injuries to the brachial plexus are typically high impact and can be debilitating, life-changing injuries. Backpack palsy is a rare but well-established cause of brachial plexus injury, arising as a result of heavy backpack use. We present an unusual case of backpack palsy with Horner's syndrome.

Backpack palsy: A rare complication of backpack use in children and young adults - A new case report

Backpack palsy is a well-recognised, albeit rare, complication of carrying backpacks. Although it has been mostly described in cadets during strenuous training, sporadic cases of brachial nerve impairment have been reported in children and young adults. Here we reported the case of a 15-year-old girl who presented with a left-side brachial palsy with axonal denervation of C5C7 motor roots following a school challenge for the Duke of Edinburgh Award. Her symptoms began soon after starting the challenge and included weakness of shoulder abduction and elevation, as well as forearm, wrist and fingers extension. After 6 months of physiotherapy her motor function was completely restored. Backpack palsy can sometimes present in children and young adults. This disorder should be taken in consideration when planning for daily, as well as more challenging, physical activities in these age groups.

Pediatric Stinger Syndrome: Acute Brachial Plexopathy After Minor Trauma

The "stinger" or "burner" is a form of transient brachial plexopathy termed for its characteristic knife-like pain extending from the neck to the fingertips. Muscle weakness and paresthesia are oftentimes associated symptoms and are similarly temporary. Commonly observed in athletes of contact sports, the stinger results from high force trauma causing either traction/direct compression to the brachial plexus or extension/compression of the cervical nerve roots. We describe a pediatric case of a stinger in a 14-year-old boy, which was caused by a relatively low force trauma accident. Our management strategy and recommendations are discussed.

Mechanical Predictors of Discomfort during Load Carriage

Discomfort during load carriage is a major issue for activities using backpacks (e.g. infantry maneuvers, children carrying school supplies, or outdoor sports). It is currently unclear which mechanical parameters are responsible for subjectively perceived discomfort. The aim of this study was to identify objectively measured mechanical predictors of discomfort during load carriage. We compared twelve different configurations of a typical load carriage system, a commercially available backpack with a hip belt. The pressure distribution under the hip belt and the shoulder strap, as well as the tensile force in the strap and the relative motion of the backpack were measured. Multiple linear regression analyses were conducted to investigate possible predictors of discomfort. The results demonstrate that static peak pressure, or alternatively, static strap force is a significant (p<0.001) predictor of discomfort during load carriage in the shoulder and hip region, accounting for 85% or more of the variation in discomfort. As an additional finding, we discovered that the regression coefficients of these predictors are significantly smaller for the hip than for the shoulder region. As static peak pressure is measured directly on the body, it is less dependent on the type of load carriage system than static strap force. Therefore, static peak pressure is well suited as a generally applicable, objective mechanical parameter for the optimization of load carriage system design. Alternatively, when limited to load carriage systems of the type backpack with hip belt, static strap force is the most valuable predictor of discomfort. The regionally differing regression coefficients of both predictors imply that the hip region is significantly more tolerant than the shoulder region. In order to minimize discomfort, users should be encouraged to shift load from the shoulders to the hip region wherever possible, at the same time likely decreasing the risk of low back pain or injury.

Deformations in the Shoulder Tissues During Load Carriage: A Computational Model

Shoulder soft tissue deformations seem to be one of the limiting factors of load carriage among soldiers and recreational backpackers that are required to carry heavy loads. Yet, there are no loading limits related to the forces borne by the shoulders, and the backpacks designs are not consistent with providing pressure relief from this sensitive anatomical region. The aim of this study was to develop a model that will enable to study the biomechanical loads that develop in the shoulder under heavy loads and to help in optimizing load carriage systems design. A 3-dimensional, anatomically accurate finite element model of a human shoulder was constructed based on MRI scans. The model was developed to calculate the effective stresses on the skin below the shoulder strap (superficial loads) and the effective strain in the brachial plexus region (inner tissue deformation) for loads of up to 35 kg. The model successfully predicted deformations in the soft tissue surrounding the brachial plexus when compared with deformations measured from load-bearing MRI scans. The model yielded a skin pressure mapping, which showed pressure hotspots in the clavicle region. Inner tissue deformations mapping, as assessed by brachial plexus envelop strains, were found to peak at 30% effective strain at the lateral aspect below the pectoralis muscle. The newly developed model successfully predicted soft tissue deformations in the shoulder related to backpacks. This model can be used to optimize load carriage systems for better distribution of pressure over the shoulders and lower inner tissue deformations.

Proximal arm weakness is the most common presentation in young Korean soldiers diagnosed as having hereditary neuropathy with liability to pressure palsy (HNPP)

OBJECTIVES

Because patients with hereditary neuropathy with liability to pressure palsy (HNPP) are diagnosed mostly in their 20s, they are likely to experience their first major neurological symptoms during military training. We aimed to analyse the clinical characteristics and electrodiagnostic study findings of patients diagnosed with HNPP during their military service.

METHODS

We identified patients diagnosed as having HNPP in 2011-2014 and investigated their initial symptom presentation, the location and severity of their weakness, the causative event, the results of electrodiagnostic studies and the results of the genetic analysis of the PMP-22 gene.

RESULTS

Among the 36 patients included in the study, 19 (52.8%) patients had upper extremity paraesthesia with proximal arm weakness caused by brachial plexus lesion. Distal upper extremity symptoms were found in 12 (33.3%) patients, and leg paraesthesia was present only in five (13.9%) patients. Among the 19 patients who had proximal arm weakness, the most common cause of weakness was the performance of push-ups as a punishment (36.8%), and strenuous push-up exercise was the second cause of this symptom (21.1%).

CONCLUSIONS

Brachial plexus lesion leading to proximal arm weakness and paraesthesia was the most common presentation in soldiers with HNPP, and strenuous push-up activity was the major leading causative event in this condition.

Suprascapular neuropathy after distal clavicle resection and coracoclavicular ligament reconstruction: a resident's case problem

STUDY DESIGN

Resident's case problem.

BACKGROUND

Acromioclavicular joint pathology is reported to be present in up to 30% of all patients complaining of shoulder dysfunction. The operative approach to treating acromioclavicular joint disease often includes a distal clavicle excision and, in circumstances of acromioclavicular joint instability, reconstruction of the coracoclavicular and/or the acromioclavicular ligament. Surgical complications for these procedures are rare, but potentially include suprascapular neuropathy secondary to the course of the suprascapular nerve posterior to the clavicle prior to entering the supraspinatus fossa.

DIAGNOSIS

A 28-year-old Caucasian woman reported directly to an outpatient physical therapy clinic with a complaint of right shoulder weakness. Three years prior, the patient underwent a distal clavicle excision and coracoclavicular ligament reconstruction. A detailed examination, including diagnostic imaging, identified infraspinatus atrophy and weakness, increasing the suspicion for suprascapular nerve injury. Electromyography was ordered to confirm the clinical and imaging diagnosis of suprascapular neuropathy and to rule out other nerve lesions, especially considering the selective atrophy of the infraspinatus muscle without mechanical explanation.

DISCUSSION

The clinical decision making and systematic use of diagnostic testing resulted in identifying a rare case of suprascapular neuropathy, selective to the infraspinatus, in a patient who previously underwent a distal clavicle excision and coracoclavicular ligament reconstruction. Without a spinoglenoid cyst or other suprascapular nerve lesion identified on advanced imaging, it is likely that the suprascapular neuropathy identified in this case was related to the surgical procedure.

LEVEL OF EVIDENCE

Differential diagnosis, level 4.

Incidence and risk factors for backpack palsy in young Korean soldiers

OBJECTIVES

Backpack palsy (BPP) is a common aetiology of brachial plexopathy in military hospitals. We aimed to determine the incidence and risk factors of BPP in young Korean soldiers.

METHODS

We identified enlisted patients who were diagnosed with BPP from a review of the medical records of all the Korean military hospitals in 2011 and 2012 and investigated their clinical findings and medical study results. To identify risk factors of BPP, we also surveyed, by questionnaire, healthy recruits of a company in a training centre who had just finished night marches. We divided them according to whether they had paresthaesia and/or weakness in their arm(s) during marching and compared their characteristics.

RESULTS

The incidence of BPP in Korean soldiers was 29.7 per 100,000 person-years (95% CI 17.2 to 24.3). Body mass index (BMI) was significantly lower in patients with BPP than it was in healthy recruits. Among healthy recruits, those who had experienced paresthaesia and/or weakness during marching had a significantly lower BMI than did those who had not.

CONCLUSIONS

We report the incidence of BPP in young Korean soldiers. A low BMI was a risk factor for BPP. These results may be helpful in establishing a strategy for the prevention of BPP in the setting of military training.

Spine buddy® supportive pad impact on single-leg static balance and a jogging gait of individuals wearing a military backpack

The Spine Buddy® supportive pad was developed to be inserted underneath military backpacks to help disperse the heavy load of the backpack. The purpose of this study was to determine the impact the additional supportive pad had on static balance and a running gait while wearing a military backpack. Forty healthy subjects (age= 27.5 + 5.6 yrs, body height= 1.78 + 0.06 m, body mass= 86.5 + 14.0 kg: mean + SD) participated in a static single-leg balance test on a force plate with each lower limb while wearing a 15.9 kg military backpack for 30 s. Following this, participants were randomized to one of two interventions: 1) Intervention, which wore the Spine Buddy® supportive pad underneath their backpack or 2) Control, with no additional supportive pad. Post-intervention measurements of static single-leg balance were then recorded. Afterwards, a similar pre vs post testing schedule and randomization scheme was used to test the impact of the supportive pad on a 5 mph jogging gait using Vicon® cameras. Within-group data were analyzed with a 2-way repeated measures ANOVA. Statistically significant differences were not seen between the control and experimental group for balance and gait variables. Preliminarily, this suggests that the Spine Buddy® supportive pad causes no deleterious effect on static balance and a jogging gait in 18-45 year-old asymptomatic individuals.

Characteristic features of hereditary neuropathy with liability to pressure palsy (HNPP) presenting with brachial plexopathy in soldiers

A brachial plexus lesion is not common in hereditary neuropathy with liability to pressure palsy (HNPP). We report the clinical and electrodiagnostic features of young soldiers with HNPP presenting with brachial plexopathy. By reviewing 2year medical records from Korean military hospitals, we identified soldiers with brachial plexus lesions. Among them, patients diagnosed with HNPP were determined and clinical and electrophysiological findings were compared between HNPP and non-HNPP patients with a brachial plexus lesion. Thirteen patients (6.8%) were diagnosed with HNPP among 189 patients with a brachial plexus lesion. Push-ups, as either a punishment or an exercise, was the most frequent preceding event in HNPP patients (76.9%), whereas it was rare in non-HNPP patients. The distal motor latency of the median nerve showed the highest sensitivity (90.9%) and specificity (100%) for HNPP in patients with a brachial plexus lesion. In conclusion, HNPP should be suspected in patients with brachial plexopathy if brachial plexopathy develops after push-ups or if the distal motor latency of median nerves is prolonged.

Upper extremity hemodynamics and sensation with backpack loads

Heavy backpacks are often used in extreme environments, for example by military during combat, therefore completion of tasks quickly and efficiently is of operational relevance. The purpose of this study was to quantify hemodynamic parameters (brachial artery Doppler and microvascular flow by photoplethysmography; tissue oxygenation by near-infrared spectroscopy; arterial oxygen saturation by pulse oximeter) and sensation in upper extremities and hands (Semmes-Weinstein monofilament test and 2-point discrimination test) while wearing a loaded backpack (12 kg) in healthy adults for 10 min. All values were compared to baseline before wearing a backpack. Moderate weight loaded backpack loads significantly decreased upper extremity sensation as well as all macrovascular and microvascular hemodynamic values. Decreased macrovascular and microvascular hemodynamics may produce neurological dysfunction and consequently, probably affect fine motor control of the hands.

Soldier occupational load carriage: a narrative review of associated injuries

This narrative review examines injuries sustained by soldiers undertaking occupational load carriage tasks. Military soldiers are required to carry increasingly heavier occupational loads. These loads have been found to increase the physiological cost to the soldier and alter their gait mechanics. Aggregated research findings suggest that the lower limbs are the most frequent anatomical site of injury associated with load carriage. While foot blisters are common, other prevalent lower limb injuries include stress fractures, knee and foot pain, and neuropathies, like digitalgia and meralgia. Shoulder neuropathies (brachial plexus palsy) and lower back injuries are not uncommon. Soldier occupational load carriage has the potential to cause injuries that impact on force generation and force sustainment. Through understanding the nature of these injuries targeted interventions, like improved physical conditioning and support to specialised organisations, can be employed.

Modeling mechanical strains and stresses in soft tissues of the shoulder during load carriage based on load-bearing open MRI

Shoulder strain is a major limiting factor associated with load carriage. Despite advances in backpack designs, there are still reports of shoulder discomfort, loss of sensorimotor functions, and brachial plexus syndrome. The current study is aimed at characterizing mechanical loading conditions (strains and stresses) that develop within the shoulder's soft tissues when carrying a backpack. Open MRI scans were used for reconstructing a three-dimensional geometrical model of an unloaded shoulder and for measuring the soft tissue deformations caused by a 25-kg backpack; subsequently, a subject-specific finite element (FE) model for nonlinear, large-deformation stress-strain analyses was developed. Skin pressure distributions under the backpack strap were used as reference data and for verifying the numerical solutions. The parameters of the model were adjusted to fit the calculated tissue deformations to those obtained by MRI. The MRI scans revealed significant compression of the soft tissues of the shoulder, with substantial deformations in the area of the subclavian muscle and the brachial plexus. The maximal pressure values exerted by a 25-kg load were substantial and reached ∼90 kPa. In the muscle surrounding the brachial plexus, the model predicted maximal compressive strain of 0.14 and maximal tensile strain of 0.13, which might be injurious for the underlying neural tissue. In conclusion, the FE model provided some insights regarding the potential mechanisms underlying brachial plexus injuries related to load carriage. The large tissue deformations and pressure hotspots that were observed are likely to result in tissue damage, which may hamper neural function if sustained for long time exposures.

Recovery of brachial plexus lesions resulting from heavy backpack use: a follow-up case series

Background

Brachial plexus lesions as a consequence of carrying a heavy backpack have been reported, but the typical clinical course and long-term consequences are not clear. Here we evaluated the clinical course and pattern of recovery of backpack palsy (BPP) in a large series of patients.

Methods

Thirty-eight consecutive patients with idiopathic BPP were identified from our population of 193,450 Finnish conscripts by means of computerised register. A physiotherapist provided instructions for proper hand use and rehabilitative exercises at disease onset. The patients were followed up for 2 to 8 years from the diagnosis. We also searched for genetic markers of hereditary neuropathy with pressure palsies. Mann-Whitney U-test was used to analyze continuous data. The Fischer's exact test was used to assess two-way tables.

Results

Eighty percent of the patients recovered totally within 9 months after the onset of weakness. Prolonged symptoms occurred in 15% of the patients, but daily activities were not affected. The weight of the carried load at the symptom onset significantly affected the severity of the muscle strength loss in the physiotherapeutic testing at the follow-up. The initial electromyography did not predict recovery. Genetic testing did not reveal de novo hereditary neuropathy with pressure palsies.

Conclusions

The prognosis of BPP is favorable in the vast majority of cases. Electromyography is useful for diagnosis. To prevent brachial plexus lesions, backpack loads greater than 40 kg should be avoided.

Brachial plexopathy and nonaccidental injury: role of the neurologist

Child neurologists must remain vigilant to the possibility of nonaccidental injury. Just as clinicians have become accustomed to considering potential abuse or neglect in children presenting with a head injury or skeletal trauma, physical abuse must also be considered when children present with lesions at other sites of the neuraxis, as illustrated by this child's brachial plexopathy. Key elements from the history can assist clinicians in differentiating accidental events from nonaccidental injuries secondary to abuse or neglect. We report a toddler who presented with a recurrent brachial plexopathy due to nonaccidental injury. Her parents initially denied the occurrence of any significant trauma. Furthermore, her diagnosis was complicated by the identification of concomitant, but unrelated lead toxicity. In this case, the vague and inconsistent parental history, plexopathy recurrence, and identification of a fracture all heightened suspicion of child abuse.

Long thoracic neuropathy caused by an apical pulmonary tumor

Long thoracic nerve palsy has been reported to have traumatic, iatrogenic, and idiopathic causes. The authors describe the case of a 62-year-old man who presented with progressively worsening right shoulder pain, winging of the scapula, and Horner syndrome. A chest CT scan revealed an apical pulmonary mass. To the authors' knowledge, this is the first report of a long thoracic nerve palsy caused by an apical pulmonary tumor.