Prospective study of biomechanical risk factors for second and third metatarsal stress fractures in military recruits

Pedobarographic evaluations in physical medicine and rehabilitation practice

The feet are complex structures that transmit loads transferred by other parts of the body to the ground and are involved in many static and dynamic activities, such as standing and walking. The contact area and pressure changes between the feet and the ground surface can be measured using pedobarographic devices. With pedobarographic examinations, it is possible to obtain a wide range of information needed to support clinical evaluation and diagnostic tests in physical medicine and rehabilitation practice. Foot structure and function, postural stability, lower extremity biomechanics, and gait analysis are among the areas that can be further investigated using pedobarography.

[Stress fractures in the military context]

BACKGROUND

Soldiers, especially as recruits, are exposed to significantly elevated stress patterns of the foot due to occupation-related marching and excessive running. This can lead to military-specific stress fractures of the metatarsals, i.e., marching fractures. The treatment and prevention of stress fractures are of particular importance in the military context due to the impact on operational capability and treatment costs. A uniform classification of these fractures does not yet exist.

OBJECTIVE

Review of stress fractures in the military setting with presentation of the incidence, risk factors, classification, treatment and prevention possibilities.

MATERIAL AND METHODS

A PubMed®-based review of the current literature on stress fractures in the military context was conducted and the results were discussed with a focus on specific military medical treatment options.

RESULTS

There are several possibilities to classify stress fractures, the most well-known being a 4-level magnetic resonance imaging (MRI)-based classification. Prevention and treatment possibilities are multifaceted but so far insufficiently validated.

CONCLUSION

Military-specific stress fractures should be grouped according to a 4-level and MRI-based classification. The treatment options include both conservative and surgical measures and should be implemented taking the patient's individual requirements into account. Preventive measures play a key role in the military context. They include the adaptation of screening tools, training and equipment and require continuous evaluation and development.

Association Between Landing Error Scoring System (LESS) Items and the Incidence Rate of Lower Extremity Stress Fracture

Background:

Lower extremity stress fracture injuries are a major cause of morbidity in physically active populations. The ability to screen for modifiable risk factors associated with injury is critical in developing injury-prevention programs.

Purpose:

To determine if baseline Landing Error Scoring System (LESS) scores are associated with the incidence rate of lower extremity stress fracture.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 1772 participants with no history of lower extremity stress fracture were included. At preinjury baseline, the authors conducted a lower extremity movement assessment during a jump-landing task using the LESS. Incident lower extremity stress fractures were identified during a 4-year follow-up period. Potential incident cases were reviewed by 2 sports medicine fellowship–trained orthopaedic surgeons blinded to baseline LESS data. Univariate and multivariable Poisson regression models were used to estimate the association between baseline total LESS scores, individual LESS items, and the incidence rate ratio (IRR) of lower extremity stress fracture.

Results:

A total of 94 incident lower extremity stress fractures were documented, for a 5.3% (95% CI, 4.3%-6.5%) cumulative incidence. The overall LESS score was associated with the incidence rate of lower extremity stress fracture. For every additional movement error documented at baseline, there was a 15% increase in the incidence rate of lower extremity stress fracture (IRR, 1.15 [95% CI, 1.02-1.31]; P = .025). In univariate analyses, ankle flexion, stance width, asymmetrical landing, and trunk flexion at initial contact, in addition to overall impression, were associated with the incidence rate of stress fracture. After controlling for sex and year of entry into the study cohort, participants who consistently landed flat-footed or heel-to-toe were 2.33 times (95% CI, 1.36-3.97; P = .002) more likely to sustain a lower extremity stress fracture. Similarly, participants who consistently demonstrated asymmetric landing at initial contact were 2.53 times (95% CI, 1.34-4.74; P = .004) more likely to sustain a stress fracture.

Conclusion:

Components of the LESS may be associated with increased lower extremity stress fracture risk and may be helpful in efficiently assessing high-risk lower extremity biomechanics in large groups.

Non-Modifiable Risk Factors for Stress Fractures in Military Personnel Undergoing Training: A Systematic Review

A fracture, being an acquired rupture or break of the bone, is a significant and debilitating injury commonly seen among athletes and military personnel. Stress fractures, which have a repetitive stress aetiology, are highly prevalent among military populations, especially those undergoing training. The primary aim of this review is to identify non-modifiable risk factors for stress fractures in military personnel undergoing training. A systematic search was conducted of three major databases to identify studies that explored risk factors for stress fractures in military trainees. Critical appraisal, data extraction, and a narrative synthesis were conducted. Sixteen articles met the eligibility criteria for the study. Key non-modifiable risk factors identified were prior stress fracture and menstrual dysfunction, while advancing age and race other than black race may be a risk factor. To reduce the incidence of stress fractures in military trainees, mitigating modifiable risk factors among individuals with non-modifiable risk factors (e.g., optimising conditioning for older trainees) or better accommodating non-modifiable factors (for example, extending training periods and reducing intensity to facilitate recovery and adaptation) are suggested, with focus on groups at increased risk identified in this review.

Risk factors for musculoskeletal injuries in the military: a qualitative systematic review of the literature from the past two decades and a new prioritizing injury model

BACKGROUND

Musculoskeletal injuries (MSkIs) are a leading cause of health care utilization, as well as limited duty and disability in the US military and other armed forces. MSkIs affect members of the military during initial training, operational training, and deployment and have a direct negative impact on overall troop readiness. Currently, a systematic overview of all risk factors for MSkIs in the military is not available.

METHODS

A systematic literature search was carried out using the PubMed, Ovid/Medline, and Web of Science databases from January 1, 2000 to September 10, 2019. Additionally, a reference list scan was performed (using the "snowball method"). Thereafter, an international, multidisciplinary expert panel scored the level of evidence per risk factor, and a classification of modifiable/non-modifiable was made.

RESULTS

In total, 176 original papers and 3 meta-analyses were included in the review. A list of 57 reported potential risk factors was formed. For 21 risk factors, the level of evidence was considered moderate or strong. Based on this literature review and an in-depth analysis, the expert panel developed a model to display the most relevant risk factors identified, introducing the idea of the "order of importance" and including concepts that are modifiable/non-modifiable, as well as extrinsic/intrinsic risk factors.

CONCLUSIONS

This is the qualitative systematic review of studies on risk factors for MSkIs in the military that has attempted to be all-inclusive. A total of 57 different potential risk factors were identified, and a new, prioritizing injury model was developed. This model may help us to understand risk factors that can be addressed, and in which order they should be prioritized when planning intervention strategies within military groups.

Biomechanical Basis of Predicting and Preventing Lower Limb Stress Fractures During Arduous Training

PURPOSE OF REVIEW

Stress fractures at weight-bearing sites, particularly the tibia, are common in military recruits and athletes. This review presents recent findings from human imaging and biomechanics studies aimed at predicting and preventing stress fractures.

RECENT FINDINGS

Peripheral quantitative computed tomography (pQCT) provides evidence that cortical bone geometry (tibial width and area) is associated with tibial stress fracture risk during weight-bearing exercise. The contribution of bone trabecular microarchitecture, cortical porosity, and bone material properties in the pathophysiology of stress fractures is less clear, but high-resolution pQCT and new techniques such as impact microindentation may improve our understanding of the role of microarchitecture and material properties in stress fracture prediction. Military studies demonstrate osteogenic outcomes from high impact, repetitive tibial loading during training. Kinetic and kinematic characteristics may influence stress fracture risk, but there is no evidence that interventions to modify biomechanics can reduce the incidence of stress fracture. Strategies to promote adaptive bone formation, in combination with improved techniques to assess bone strength, present exciting opportunities for future research to prevent stress fractures.

Training Load Capacity, Cumulative Risk, and Bone Stress Injuries: A Narrative Review of a Holistic Approach

Bone stress injuries (BSIs) are a common orthopedic injury with short-term, and potentially long-term, effects. Training load capacity, influenced by risk factors, plays a critical role in the occurrence of BSIs. Many factors determine how one's body responds to repetitive loads that have the potential to increase the risk of a BSI. As a scientific community, we have identified numerous isolated BSI risk factors. However, we have not adequately analyzed the integrative, holistic, and cumulative nature of the risk factors, which is essential to determine an individual's specific capacity. In this narrative review, we advocate for a personalized approach to monitor training load so that individuals can optimize their health and performance. We define “cumulative risk profile” as a subjective clinical determination of the number of risk factors with thoughtful consideration of their interaction and propose that athletes have their own cumulative risk profile that influences their capacity to withstand specific training loads. In our narrative review, we outline BSI risk factors, discuss the relationship between BSIs and training load, highlight the importance of individualizing training load, and emphasize the use of a holistic assessment as a training load guide.

Worldwide epidemiology of foot and ankle injuries during military training: a systematic review

INTRODUCTION

Musculoskeletal foot and ankle injuries are commonly experienced by soldiers during military training. We performed a systematic review to assess epidemiological patterns of foot and ankle injuries occurring during military training.

METHODS

A review of the literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The search, done on 14 February 2019, resulted in 1603 reports on PubMed, 565 on Embase and 3 on the Cochrane Library. After reading the remaining full-text articles, we included 91 studies.

RESULTS

Among a population of 8 092 281 soldiers from 15 countries, 788 469 (9.74%) foot and ankle injuries were recorded. Among the 49 studies that reported on length of training, there were 36 770/295 040 (18.17%) injuries recorded among women and 248 660/1 501 672 (16.56%) injuries recorded among men over a pooled mean (±SD) training period of 4.51±2.34 months. Ankle injuries were roughly 7 times more common than foot injuries, and acute injuries were roughly 24 times more common than non-acute injuries. Our findings indicated that, during a 3-month training period, soldiers have a 3.14% chance of sustaining a foot and ankle injury. The incidence of foot or ankle injury during military parachutist training was 3.1 injuries per thousand jumps.

CONCLUSIONS

Our findings provide an overview of epidemiological patterns of foot and ankle injuries during military training. These data can be used to compare incidence rates of foot and ankle injuries due to acute or non-acute mechanisms during training. Cost-effective methods of preventing acute ankle injuries and non-acute foot injuries are needed to address this problem.

A Narrative Review of Metatarsal Bone Stress Injury in Athletic Populations: Etiology, Biomechanics, and Management

Metatarsal bone stress injuries (BSIs) are common in athletic populations. BSIs are overuse injuries that result from an accumulation of microdamage that exceeds bone remodeling. Risk for metatarsal BSI is multifactorial and includes factors related to anatomy, biology, and biomechanics. In this article, anatomic factors including foot type, metatarsal length, bone density, bone geometry, and intrinsic muscle strength, which each influence how the foot responds to load, are discussed. Biologic factors such as low energy availability and impaired bone metabolism influence the quality of the bone. Finally, the influence of biomechanical loads to bone such as peak forces, load rates, and loading cycles are reviewed. General management of metatarsal BSI is discussed, including acute care, rehabilitation, treatment of refractory metatarsal BSI, and evaluation of healing/return to sport. Finally, we identify future research priorities and emerging treatments for metatarsal BSI.

Parâmetros da pressão plantar, tipo e sensibilidade do pé em recrutas: um estudo prospectivo

RESUMO Este estudo teve como objetivo avaliar as características da pressão plantar, tipo e sensibilidade do pé em recrutas durante o período do serviço militar obrigatório. Sessenta indivíduos que prestaram o serviço militar obrigatório foram avaliados para pressão plantar (baropodômetro EPS LoranEngineering, Bolonha, Itália) e sensibilidade plantar ao toque superficial (estesiômetro de Semmes-Weinsten) em três momentos distintos: março (linha de base), junho (após 16 semanas de treinamento) e setembro (após 36 semanas de treinamento militar). Foram avaliadas a descarga de peso ântero-posterior e latero-lateral, pressão média, pressão máxima, área de contato do pé, tipologia de pé e sensibilidade plantar. Os dados foram analisados pelo teste do Qui-quadrado, anova de medidas repetidas e pelo teste de Friedman com pos hoc de Bonferroni (p<0,05). Houve aumento na área de contato (p=0,001) e na pressão média de ambos os pés (p<0,001). Quanto a tipologia, aproximadamente 60% dos indivíduos possuíam o pé direito do tipo normal, enquanto o pé esquerdo era do tipo cavo (50,3%); ou seja, mesmos sujeitos apresentaram diferentes tipologias do pé. Em relação a sensibilidade plantar, houve diferença na região do médio pé ao longo do treinamento (p=0,001 no pé dominante e p=0,009 no pé não dominante). Esses resultados demonstram que houve aumento da pressão média e área total de contato do pé, bem como alterações na sensibilidade plantar da região do médio pé ao longo do serviço militar obrigatório.