Stress Fracture Injury Research Articles

Lower Extremity Stress Fractures in the National Basketball Association, 2013-2014 Through 2018-2019.

Background:Players in the National Basketball Association (NBA) are at risk for lower extremity stress fractures, partly because of the sport’s high-intensity demand on the lower body.Purpose:To provide insight on the identification and management of potential risk factors associated with lower extremity stress fractures in NBA athletes.Study Design:Case series; Level of evidence, 4.Methods:A retrospective study was conducted using the NBA electronic medical record database for all players who were on an NBA roster for ≥1 game from the 2013-2014 through 2018-2019 seasons. Player characteristics, games missed, and treatment methodology were independently analyzed. Results were presented as incidence per 1000 player-games.Results:There were 22 stress fractures identified in 20 NBA players over the course of 6 years, with an average of 3.67 stress fractures per year and an incidence of 0.12 stress fractures per 1000 player-games. Most stress fractures occurred in the foot (17/22), and 45% (10/22) of stress fractures were treated surgically, with the most common site of operation being the navicular. On average, approximately 37 games and 243 days were missed per stress fracture injury. There was no significant difference in time to return to play between high-risk stress fractures treated operatively versus nonoperatively (269.2 vs 243.8 days; P = .82).Conclusion:The overall incidence of stress fractures in NBA players was 0.12 per 1000 player-games, and a high percentage of players returned to NBA activity after the injury. There was a relatively even distribution between high-risk stress fractures treated operatively and nonoperatively. When comparing high-risk stress fractures treated operatively to ones treated nonoperatively, no significant difference in average time to return to play in the NBA was found.

Reproductive health and stress fracture risk: a wearables solution

Introduction: Insulin-like growth factor 1 (IGF-I) is a mitogenic and metabolic growth factor that can act both systemically and locally, being produced predominantly in the liver but also by other tissues including the brain, kidneys, muscle, and bone1,2. IGF-I is well-established as an important mediator of bone formation, remodelling, and repair and can be easily measured in serum. IGF-I stimulates osteoblast proliferation, bone matrix protein synthesis, alkaline phosphatase activity and differentiation. Loss of IGF-I results in decreased long bone size, reduced growth plates, and delayed formation of secondary ossification centers in mice. Conversely, transgenic mice with osteoblast-targeted overexpression of IGF-I demonstrate an accelerated bone formation rate with increased bone mineral density (BMD) and trabecular and cortical bone volume. The essential nature of IGF-I in bone development is recapitulated in humans. Individuals with disruptions in the IGF-I gene causing reduced serum IGF-I concentrations have a severe reduction in peak BMD compared to normal age-matched individuals. Methods: This presentation will provide an overview of the relationship between the IGF-I system and bone health and remodelling, with a particular emphasis toward military relevance and utility of measuring IGF-I during military training2,3. Because the IGF-I system is involved in bone formation, remodelling, and repair, female recruits sustaining stress fractures during military training would be of special interest with regard to differential circulating concentrations of IGF-I system components compared to their uninjured female counterparts. Moreover, serum measurements of the IGF-I system could possibly provide further insight into stress fracture injury risk. Conclusions: Preliminary data3 suggest that circulating IGF-I system components are differentially expressed in females sustaining stress fractures during military BT. Additionally, data suggest that the bioavailable IGF-I response to strenuous exercise may differ in female recruits susceptible to stress fracture injury when compared to non-injured recruits. This suggests the possibility that increased susceptibility to stress fracture injury may be attributed to differences in the IGF-I system response to physical training (i.e., increased susceptibility to stress fracture may be due to a blunted bioavailable IGF-I response to training or increased basal levels of certain IGFBPs). However, the underlying mechanism for the differences in IGF-I system component concentrations between recruits sustaining stress fractures and uninjured counterparts is still unclear and warrants further investigation. References 1Nindl BC, Pierce JR. Insulin-like growth factors I as a biomarker of health, fitness, and training status. Med Sci Sports Exerc 2010; 42(1):39-49. https://doi.org/10.1249/mss.0b013e3181b07c4d 2Nindl BC, McClung JP, Miller JK, et al. Bioavailable IGF-I is associated with fat-free mass gains after physical training in women. Med Sci Sports Exerc 2011; 43(5):793-799. https://doi.org/10.1249/MSS.0b013e31820065.ea 3Strohbach CA, Scofield DE, Nindl BC, et al. Female recruits sustaining stress fractures during military basic training demonstrate differential concentrations of circulating IGF-I system components: a preliminary study. Growth Horm IGF Res 2012; 22(5):151-157. https://doi.org/10.1016/j.ghir.2012.04.007

An investigation into the association of bone characteristics and body composition with stress fracture in athletes.

The aim of the study was to establish the bone and body composition characteristics of high-level athletes with and without a history of stress fracture injury. Overall, 279 high-level athletes (212 men, 67 women) (age 28.0±9.2 years; body mass 75.0±17.4 kg; height 1.78±0.10 m) and 112 non-athletic controls (60 women, 52 men) 36.2±15.0 years; 70.9±12.9 kg; 1.71±0.10 m) were assessed by DXA to establish their bone mineral density and content, body fat and lean mass. Athletes completed a questionnaire detailing their stress fracture history. There were no differences in whole-body bone mineral density (men 1.41±0.12 g/cm2, women 1.19±0.09 g/cm2), bone mineral content (men 3709±626 g, women 2263±290 g), body fat (men 16.3±5.0%,women 23.0±4.6%) and lean mass (men 65.4±9.9 kg, women 38.7±3.6 kg) between athletes with a history of stress fracture (34 men, 16 women) and those without (176 men, 40 women). DXA derived bone and body composition characteristics were not independent risk factors for stress fracture injury in high-level athletes. This study in a large cohort of high-level athletes provides normative bone and body composition values that can be used as a benchmark for researchers and applied practitioners.

Interleukin-6 (IL-6) deficiency enhances intramembranous osteogenesis following stress fracture in mice.

Interleukin-6 (IL-6) is highly upregulated in response to skeletal injury, suggesting it plays a role in the inflammatory phase of fracture repair. However, the impact of IL-6 on successful repair remains incompletely defined. Therefore, we investigated the role of IL-6 in two models of fracture repair (full fracture and stress fracture) using 12-week old IL-6 global knockout mice (IL-6 KO) and wild type (WT) littermate controls. Callus morphology and mineral density 14days after full femur fracture did not differ between IL-6 knockout mice and controls. In contrast, IL-6 KO mice had an enhanced bone response 7days after ulnar stress fracture compared to WT, with increased total callus volume (p=0.020) and callus bone volume (p=0.045). IL-6 KO did not alter the recruitment of immune cells (Gr-1 or F4/80 positive) to the stress fracture callus. IL-6 KO also did not alter the number of osteoclasts in the stress fracture callus. Using RNA-seq, we identified differentially expressed genes in stress fracture vs. contralateral control ulnae, and observed that IL-6 KO resulted in only modest alterations to the gene expression response to stress fracture (SFx). Wnt1 was more highly upregulated in IL-6 KO SFx callus at both day 1 (fold change 12.5 in KO vs. 5.7 in WT) and day 3 (fold change 4.7 in KO vs. 1.9 in WT). Finally, using tibial compression to induce bone formation without bone injury, we found that IL-6 KO directly impacted osteoblast function, increasing the propensity for woven bone formation. In summary, we report that IL-6 knockout enhanced formation of callus and bone following stress fracture injury, likely through direct action on the osteoblast's ability to produce woven bone. This suggests a novel role of IL-6 as a suppressor of intramembranous bone formation.

Lumbar bone mineral asymmetry in elite cricket fast bowlers.

Bone responds to mechanical loading by increasing bone mineral density (BMD) and/or bone area to enhance bone strength at the site of the greatest strain. Such localised adaptation has not been demonstrated at the spine. The aim of this study is to determine if BMD and/or bone mineral content (BMC) differs between dominant (ipsilateral to bowling/throwing arm) and non-dominant sides of the vertebrae in cricket fast bowlers, and whether this asymmetry differs according to stress fracture or disc injury history. A further aim was to determine if regional BMD and BMC in the lumbar spine differ between fast bowlers, other cricketers, rugby players and non-active controls, to highlight the site-specific response of lumbar vertebra to unilateral activity. 23 fast bowlers, 14 other cricketers, 22 rugby players and 20 controls underwent an antero-posterior (AP) and lateral DXA scans of their lumbar spine to assess BMD, BMC and area. A custom analysis measured BMD and BMC of the dominant and non-dominant sides (lateral 33%) of the AP lumbar spine. BMD and BMC were compared between groups, injury status, vertebrae and sides using ANOVA. Analysis of medical records showed that 6 fast bowlers had a history of lumbar stress fracture. Significantly greater BMD and BMC was found in the L4 non-dominant vertebra compared with the dominant vertebra in fast bowlers. BMD and BMC differed significantly according to vertebra, side and group, with fast bowlers having significantly greater BMD and BMC at the L3 and L4 non-dominant vertebra compared with other groups (L3: 13.3%-45.3%, L4: 15.7%-44.0%) compared with other groups. Fast bowlers who never suffered lumbar stress fracture had 3.6% and 1.7% greater BMD in the dominant and non-dominant sides of lumbar vertebrae respectively compared with those who did suffer lumbar stress fracture, but evidence of this was weaker (P = 0.08). The lumbar spine responds to a unique unilateral high loading activity through site-specific increased bone mass at the site of most strain. Fast bowlers had increased lumbar BMD, particularly on the non-dominant side of L4, although this adaptation was less marked in those with history of lumbar stress fracture. Site-specific low bone mineral density within the lumbar side may be implicated in the aetiology of lumbar stress fracture.

3D Tibia Reconstruction Using 2D Computed Tomography Images.

Skeletal stress fracture of the lower limbs remains a significant problem for the military. The objective of this study was to develop a subject-specific 3D reconstruction of the tibia using only a few CT images for the prediction of peak stresses and locations. Full bilateral tibial CT scans were recorded for 63 healthy college male participants. A 3D finite element (FE) model of the tibia for each subject was generated from standard CT cross-section data (i.e., 4%, 14%, 38%, and 66% of the tibial length) via a transformation matrix. The final reconstructed FE models were used to calculate peak stress and location on the tibia due to a simulated walking load (3,700 N), and compared to the raw models. The density-weighted, spatially-normalized errors between the raw and reconstructed CT models were small. The mean percent difference between the raw and reconstructed models for peak stress (0.62%) and location (-0.88%) was negligible. Subject-specific tibia models can provide even great insights into the mechanisms of stress fracture injury, which are common in military and athletic settings. Rapid development of 3D tibia models allows for the future work of determining peak stress-related injury correlates to stress fracture outcomes.

SUPPLEMENTAL VITAMIN D FOR PREVENTION OF BONE STRESS INJURIES IN COLLEGIATE ATHLETES

Purpose: Vitamin D functions to regulate serum calcium concentrations via several cellular pathways. It has also been demonstrated to affect bone mineralization and turnover, thus making it essential for skeletal strength and adaptation to mechanical stress. Stress fractures are common athletic injuries formed by cyclic, repetitive skeletal loading that causes physical breakdown of the bone’s microstructure. Excessive running or jumping, coinciding with additional factors such as malnutrition or decreased sun exposure, may elevate an athlete’s risk for sustaining this overuse injury. Serum 25(OH)D is used as a clinical marker for vitamin D status. Previous research suggests adequate vitamin D status is important for prevention of skeletal injuries. Our hypothesis states that supplemental vitamin D will normalize athletes’ vitamin D status and will reduce stress fracture injury incidence rates for elite division 1 athletes. Methods: Prospective 245 subjects were recruited from 17 sports teams at the university. All subjects were over 18 years of age. No subjects were excluded. Subject 25(OH)D status was determined twice; once in August 2016, and again in February 2017. Following each testing cycle, subjects with 25(OH)D levels below 70 ng/ml were supplemented with cholecalciferol (50,000 IU) once a week for 8 weeks. Subjects were then monitored throughout their respective sporting seasons for stress fractures or other overuse skeletal injuries. Subjects initially completed an anthropometric questionnaire, and two compliance questionnaires were to be completed following each 8-week supplementation period. Retrospective: Athlete injury reports from each of the 17 teams will be used as a control to determine the incidence of stress fractures during the 2011-2015 seasons among non-supplemented athletes. Results: 245 subjects had 25(OH)D levels tested in August (40.4?14.3 ng/ml) with 18% being insufficient or deficient (<30 ng/ml). 191 subjects were tested in February (27.7?8.85 ng/ml) with 65% being insufficient or deficient, a significant decrease. All but three teams had significantly lower 25(OH)D levels in February compared to August. There was no significant difference between male and female athletes, however both groups saw significant declines in February. There was no significant difference between indoor and outdoor sports in August and February. 2 stress injuries were diagnosed in 118 enrolled subjects in our previous arm (1.65%). 2 additional stress injuries were diagnosed in 191 remaining subjects in our current arm (1.0%). 36 stress fractures were diagnosed in 571 subjects retrospectively (6.3%). Conclusion: Several factors have been shown to influence vitamin D status, including nutrition and sun exposure. Serum 25(OH)D status is expected to decline naturally in winter months due to lack of sun exposure. Results indicate a substantial decline in serum 25(OH)D from August to February in our cohort. This supports the notion that continued supplementation may be necessary to maintain appropriate vitamin D levels. The incidence of stress fractures per year as well as the proportion of stress fractures per academic year have consistently declined as more attention is paid toward vitamin D supplementation.

P2X7, a critical regulator and potential target for bone and joint diseases.

Abundant evidence indicted that P2X7 receptor show a essential role in human health and some human diseases including hypertension, atherosclerosis, pulmonary inflammation, tuberculosis infection, psychiatric disorders, and cancer. P2X7 receptor also has an important role in some central nervous system diseases such as neurodegenerative disorders. Recently, more research suggested that P2X7 receptor also plays a crucial role in bone and joint diseases. But the effect of P2X7 receptor on skeletal and joint diseases has not been systematically reviewed. In this article, the role of P2X7 receptor in skeletal and joint diseases is elaborated. The activation of P2X7 receptor can ameliorate osteoporosis by inducing a fine balance between osteoclastic resorption and osteoblastic bone formation. The activation of P2X7 receptor can relieve the stress fracture injury by increasing the response to mechanical loading and inducing osteogenesis. But the activation of P2X7 receptor mediates the cell growth and cell proliferation in bone cancer. In addition, the activation of P2X7 receptor can aggravate the process of some joint diseases such as osteoarthritis, rheumatoid arthritis, and acute gouty arthritis. The inhibition of P2X7 receptor can alleviate the pathological process of joint disease to some extent. In conclusion, P2X7 receptor may be a critical regulator and therapeutic target for bone and joint diseases.

Ultrasound evaluation of stress injuries and physiological adaptations in the fingers of adolescent competitive rock climbers

The impact of high-intensity, repetitive training on the fingers of adolescent climbers is relatively unknown. To evaluate this effect by ultrasound (US) and to confirm some findings by magnetic resonance imaging (MRI). The US study was performed in 20 adolescent rock climbers (ages 10-17years) and 6 non-climbing controls (ages 11-15years). US was used to examine the third digit of the right hand for differences in thickness of soft tissue, flexor and extensor tendon, volar plate and bony and growth plate adaptations. In four climbers with finger deformity or pain, 3-T MR images were compared with US findings. Number of hours/week and years of climbing were used to group climbers in three levels (3=most intense training). Mann-Whitney test was used for statistical analysis. Compared with non-climbing controls, climbers demonstrated significantly thicker flexor tendons, volar plates and soft tissues. Joint effusions were found in 13/19 (68%) climbers. Significant phalangeal malalignment was seen in 10/19 (53%) climbers. Growth plate deformities were identified in three level 3 climbers. US findings correlated with MRI for effusions, phalangeal growth plate injury, malalignment and adaptive changes. MRI additional showed capsule rupture (n=1), stress fracture (n=1) and phalangeal physeal stress injury (n=1). Competitive rock climbing results in physiological adaptations in the fingers, an example being significant soft-tissue hypertrophy of the flexor. US demonstrated several non-physiological changes in response to repetitive stress in half of the climbers. MRI showed additional stress injuries to the growth plate, joints and bone.

The association of novel polymorphisms with stress fracture injury in Elite Athletes: Further insights from the SFEA cohort

ObjectivesTo determine, in conjunction with a wider investigation, whether 11 genetic variants in the vicinity of vitamin D, collagen and Wnt signalling pathways were associated with stress fracture injury in the Stress Fracture Elite Athlete (SFEA) cohort. DesignGenotype-phenotype association study. MethodsSelf-reported stress fracture history and demographic data were recorded in 518 elite athletes, 449 male and 69 female (mean age 24.2±5.5 years) from the SFEA cohort. Elite athletes were assigned to two groups based on history of stress fracture injury. Data were analysed for the whole cohort and sub-stratified in to male only and multiple stress fracture cases. Genotype was determined using a proprietary fluorescence-based competitive allele-specific polymerase chain reaction assay. ResultsSOST SNP rs1877632 and VDR SNPs rs10735810 and rs731236 were associated with stress fracture (p<0.05). In the whole cohort, rs1877632 heterozygotes and homozygotes of the rare allele combined made up 59% of stress fracture sufferers in comparison to 46% in the non-stress fracture group (p=0.05). In the multiple stress fracture cohort, homozygotes of the rare allele of rs10735810 and rs731236 showed an association with stress fracture when compared to those homozygotes for the common allele combined with heterozygotes (p=0.03; p=0.01). No significant associations were shown in the other SNPs analysed (p>0.05). ConclusionsThese data suggest an important role for SOST SNP rs1877632 and VDR SNPs rs10735810 and rs731236 in the pathophysiology of stress fracture. This might be due to the role of the SNPs in the regulation of bone remodelling and adaptation to mechanical loading, with potential implications for the prevention and treatment of stress fracture injuries.

Tibial Density and Trabecular Microarchitecture in Army Recruit Stress Fracture Cases and Matched Uninjured Controls

Stress fractures are common overuse injuries experienced by military recruits during initial training. Lower cross sectional area of the tibia in stress fracture cases compared with uninjured controls supports an important role of bone structure in injury predisposition. With the advent of high resolution techniques, other determinants of bone strength can now be evaluated in the development of stress fracture injury. PURPOSE: To investigate differences in bone density and trabecular (Tb) microarchitecture at the distal tibia using in vivo high-resolution peripheral quantitative computed tomography (HR-pQCT) between stress fractured and uninjured British Army infantry recruits. METHODS: 324 British Army infantry recruits were followed through 26 weeks of infantry training. Twenty-one recruits were diagnosed with a stress fracture injury of the lower limb (22 ± 3 years, 73.3 ± 8.3 kg, 1.78 ± 0.06 m, 593 ± 68 s 1.5 km run time), and matched to 21 non-injured controls (22 ± 3 years, 74.2 ± 10.0 kg, 1.77 ± 0.06 kg, 588 ± 58s 1.5 km run time) in the same training platoon. Groups were matched for age, height, body mass and aerobic fitness (1.5 km run time). Scans at the distal tibia of the dominant leg were performed on all volunteers using HR-pQCT (Xtreme CT, Scanco Medical, Switzerland) in week one of training. RESULTS: No significant differences were observed in bone density or Tb microarchitecture between stress fracture cases and uninjured controls (P > 0.05). A subgroup of seven cases suffering stress fractures to the tibia had higher Tb bone density (245 ± 32 vs 209 ± 28 mg HA/cm3, P = 0.042), higher sub-endocortical Tb density (320 ± 21 vs 282 ± 32 mg HA/cm3, P = 0.047) and higher Tb volume to tissue volume ratio (0.204 ± 0.027 vs 0.174 ± 0.023, P = 0.042) than uninjured controls. CONCLUSION: Young healthy men suffering stress fracture in training do not differ in their bone structure or Tb microarchitecture at the distal tibia from uninjured matched counterparts. Our understanding of bone microarchitecture in the development of stress fractures is limited by the utility of high resolution techniques to distal sites. Future studies should explore phenotypic characteristics in stress fracture cases at specific sites of injury, which typically develop at the distal third of the tibia in military recruits. Supported by UK MoD (Army).

Excess Stress Fractures, Musculoskeletal Injuries, and Health Care Utilization Among Unfit and Overweight Female Army Trainees

Background: Musculoskeletal injuries are prevalent among military trainees and certain occupations. Fitness and body mass index (BMI) have been associated with musculoskeletal conditions, including stress fractures. Hypothesis: The incidence of, and excess health care utilization for, stress fracture and non–stress fracture overuse musculoskeletal injuries during the first 6 months of service is higher among unfit female recruits. Those who exceeded body fat limits are at a greater risk of incident stress fractures, injuries, or health care utilization compared with weight-qualified recruits. Study Design: Cohort study; Level of evidence, 3. Methods: All applicants to the United States Army were required to take a preaccession fitness test during the study period (February 2005–September 2006). The test included a 5-minute step test scored as pass or fail. BMI was recorded at application. There were 2 distinct comparisons made in this study: (1) between weight-qualified physically fit and unfit women and (2) between weight-qualified physically fit women and those who exceeded body fat limits. We compared the incidence of, and excess health care utilization for, musculoskeletal injuries, including stress fractures and physical therapy visits, during the first 183 days of military service. Results: Among the weight-qualified women, unfit participants had a higher non–stress fracture injury incidence and related excess health care utilization rate compared with fit women, with rate ratios of 1.32 (95% CI, 1.14-1.53) and 1.18 (95% CI, 1.10-1.27), respectively. Among fit women, compared with the weight-qualified participants, those exceeding body fat limits had higher rate ratios for non–stress fracture injury incidence and related excess health care utilization of 1.27 (95% CI, 1.07-1.50) and 1.20 (95% CI, 1.11-1.31), respectively. Weight-qualified women who were unfit had a higher incidence of stress fractures and related excess health care utilization compared with fit women, with rate ratios of 1.62 (95% CI, 1.19-2.21) and 1.22 (95% CI, 1.10-1.36), respectively. Among fit women exceeding body fat limits, the stress fracture incidence and related excess health care utilization rate ratios were 0.79 (95% CI, 0.49-1.28) and 1.44 (95% CI, 1.20-1.72), respectively, compared with those who were weight qualified. Conclusion: The results indicate a significantly increased risk of musculoskeletal injuries, including stress fractures, among unfit recruits and an increased risk of non–stress fracture musculoskeletal injuries among recruits who exceeded body fat limits. Once injured, female recruits who were weight qualified but unfit and those who were fit but exceeded body fat limits had increased health care utilization. These findings may have implications for military accession and training policies as downsizing of military services will make it more important than ever to optimize the health and performance of individual service members.

An Integrated Musculoskeletal-Finite-Element Model to Evaluate Effects of Load Carriage on the Tibia During Walking.

Prior studies have assessed the effects of load carriage on the tibia. Here, we expand on these studies and investigate the effects of load carriage on joint reaction forces (JRFs) and the resulting spatiotemporal stress/strain distributions in the tibia. Using full-body motion and ground reaction forces from a female subject, we computed joint and muscle forces during walking for four load carriage conditions. We applied these forces as physiological loading conditions in a finite-element (FE) analysis to compute strain and stress. We derived material properties from computed tomography (CT) images of a sex-, age-, and body mass index-matched subject using a mesh morphing and mapping algorithm, and used them within the FE model. Compared to walking with no load, the knee JRFs were the most sensitive to load carriage, increasing by as much as 26.2% when carrying a 30% of body weight (BW) load (ankle: 16.4% and hip: 19.0%). Moreover, our model revealed disproportionate increases in internal JRFs with increases in load carriage, suggesting a coordinated adjustment in the musculature functions in the lower extremity. FE results reflected the complex effects of spatially varying material properties distribution and muscular engagement on tibial biomechanics during walking. We observed high stresses on the anterior crest and the medial surface of the tibia at pushoff, whereas high cumulative stress during one walking cycle was more prominent in the medioposterior aspect of the tibia. Our findings reinforce the need to include: (1) physiologically accurate loading conditions when modeling healthy subjects undergoing short-term exercise training and (2) the duration of stress exposure when evaluating stress-fracture injury risk. As a fundamental step toward understanding the instantaneous effect of external loading, our study presents a means to assess the relationship between load carriage and bone biomechanics.

Pathogenesis of Fifth Metatarsal Stress Fractures in College Soccer Players

Category: Sports Introduction/Purpose: The pathogenesis of fifth metatarsal stress fractures remains uncertain. We hypothesized that physical characteristics and environmental factors, which have received limited attention in the literature thus far, might be involved in the development of such fractures. To test our hypothesis, we performed a medical checkup and a survey of the living environment of athletes in college soccer teams, and subsequently, we investigated the existence of fifth metatarsal stress fractures, and examined the differences between the injury group and the non-injury group. Methods: The survey and measurements were conducted in 273 male athletes from the same college soccer team between 2005 and 2013. A medical checkup, comprising assessment of stature, body weight, body mass index, arch height ratio, toe-grip strength, quadriceps angle, leg-heel angle, functional reach test, one-leg standing time with eyes closed, straight leg raise test, finger-floor distance, heel-to-buttock distance, ankle joint range of motion, and general joint laxity test, and a questionnaire survey were performed once a year. A survey was conducted at the time of injury that resulted in fifth metatarsal stress fractures. The study participants were separated into an injury group and a non-injury group, depending on whether they had a fifth metatarsal stress fracture. The measurement items and survey items were compared, and the association between the presence or absence of injury and the measurement items was analyzed. Results: Toe-grip strength was significantly weaker in the injury group, compared with the non-injury group, suggesting that a weak toe-grip is associated with fifth metatarsal stress fracture (p &lt; 0.05). In addition, injury on the non-dominant leg was more frequent in the fifth metatarsal stress fracture injury group (p &lt; 0.05). Between-group comparisons of the other items showed no statistically significant differences. Conclusion: The association between weak toe-grip strength and fifth metatarsal fracture suggests that a weak toe-grip may lead to an increase in the load applied onto the lateral side of the foot; this may cause mechanical stress on the bone. In addition, the effect of the non-dominant leg on the fifth metatarsal bone may need to be studied further.

Functional polymorphisms in the P2X7 receptor gene are associated with stress fracture injury.

Military recruits and elite athletes are susceptible to stress fracture injuries. Genetic predisposition has been postulated to have a role in their development. The P2X7 receptor (P2X7R) gene, a key regulator of bone remodelling, is a genetic candidate that may contribute to stress fracture predisposition. The aim of this study is to evaluate the putative contribution of P2X7R to stress fracture injury in two separate cohorts, military personnel and elite athletes. In 210 Israeli Defense Forces (IDF) military conscripts, stress fracture injury was diagnosed (n = 43) based on symptoms and a positive bone scan. In a separate cohort of 518 elite athletes, self-reported medical imaging scan-certified stress fracture injuries were recorded (n = 125). Non-stress fracture controls were identified from these cohorts who had a normal bone scan or no history or symptoms of stress fracture injury. Study participants were genotyped for functional SNPs within the P2X7R gene using proprietary fluorescence-based competitive allele-specific PCR assay. Pearson's chi-squared (χ (2)) tests, corrected for multiple comparisons, were used to assess associations in genotype frequencies. The variant allele of P2X7R SNP rs3751143 (Glu496Ala-loss of function) was associated with stress fracture injury, whilst the variant allele of rs1718119 (Ala348Thr-gain of function) was associated with a reduced occurrence of stress fracture injury in military conscripts (P < 0.05). The association of the variant allele of rs3751143 with stress fractures was replicated in elite athletes (P < 0.05), whereas the variant allele of rs1718119 was also associated with reduced multiple stress fracture cases in elite athletes (P < 0.05). The association between independent P2X7R polymorphisms with stress fracture prevalence supports the role of a genetic predisposition in the development of stress fracture injury.

Pathogenesis of Fifth Metatarsal Fractures in College Soccer Players

Background:The pathogenesis of fifth metatarsal stress fractures remains uncertain.Hypothesis:Physical characteristics and environmental factors, which have received limited attention in the literature thus far, might be involved in the development of fifth metatarsal stress fractures.Study Design:Case-control study; Level of evidence, 3.Methods:To test the study hypothesis, a medical examination and survey of the living environment of collegiate soccer players was conducted and correlated with the existence of fifth metatarsal stress fractures. The survey and measurements were conducted in 273 male athletes from the same college soccer team between 2005 and 2013. A medical examination comprising assessment of stature, body weight, body mass index, foot–arch height ratio, toe-grip strength, quadriceps angle, leg-heel angle, functional reach test, single-leg standing time with eyes closed, straight-leg raise angle, finger-floor distance, heel-buttock distance, ankle joint range of motion, and a general joint laxity test were performed once a year, along with a questionnaire survey. The survey was also repeated when a fifth metatarsal stress fracture was diagnosed. The study participants were separated into a fifth metatarsal stress fracture injury group and a noninjury group. The measurement items and survey items were compared, and the association between the factors and the presence or absence of injuries was analyzed.Results:Toe-grip strength was significantly weaker in the injury group compared with the noninjury group, suggesting that weak toe-grip is associated with fifth metatarsal stress fracture (P < .05). In addition, fifth metatarsal stress fractures were more common in the nondominant leg (P < .05). Between-group comparisons of the other items showed no statistically significant differences.Conclusion:The association between weak toe-grip strength and fifth metatarsal fracture suggests that weak toe-grip may lead to an increase in the load applied onto the lateral side of the foot, resulting in stress fracture. The finding of stress fracture being more common in the nondominant leg needs further study.

Stress fracture injury in female endurance athletes in the United Kingdom: A 12-month prospective study.

Studies of stress fracture (SF) incidence are limited in number and geographical location; this study determined the incidence of SF injury in female endurance athletes based in the United Kingdom. A total of 70 athletes aged between 18 and 45 years were recruited and prospectively monitored for 12 months. Questionnaires at baseline and 12 months assessed SF, menstrual and training history, eating psychopathology, and compulsive exercise. Peak lower leg muscle strength was assessed in both legs using an isometric muscle rig. Bone mineral density (BMD) of total body, spine, hip, and radius was assessed using dual X-ray absorptiometry. Among the 61 athletes who completed the 12-month monitoring, two sustained a SF diagnosed by magnetic resonance imaging, giving an incidence rate (95% confidence intervals) of 3.3 (0.8, 13.1) % of the study population sustaining a SF over 12 months. The SF cases were 800 m runners aged 19 and 22 years, training on average 14.2 h a week, eumenorrheic with no history of menstrual dysfunction. Case 1 had a higher than average energy intake and low eating psychopathology and compulsive exercise scores, while the reverse was true in case 2. BMD in both cases was similar to mean values in the non-SF group. The incidence of SF in our female endurance athlete population based in the United Kingdom was 3.3%, which is lower than previously reported. Further work is needed to confirm the current incidence of SF and evaluate the associated risk factors.

Epidemiology of Stress Fracture Injuries Among US High School Athletes, 2005-2006 Through 2012-2013

Background: High school athletes in the United States sustain millions of injuries annually, approximately 10% of which are fractures. However, there is no clear estimate of the number of stress fractures sustained by high school athletes annually despite reports that stress fractures account for 0.7% to 20% of injuries seen in sports medicine clinics. This suggests a high utilization of resources for a potentially preventable injury. In addition, stress fractures have been associated with low energy availability and disordered eating in young athletes, highlighting the importance of early recognition and intervention. Purpose: To investigate stress fracture rates and patterns in a large national sample of US high school athletes. Study Design: Descriptive epidemiologic study. Methods: Data from High School RIO (Reporting Information Online), a national sports injury surveillance study, were analyzed to describe rates and patterns of stress fracture injury sustained from 2005-2006 through 2012-2013, across sports and by sex. Results: From 2005-2006 through 2012-2013, a total of 51,773 injuries were sustained during 25,268,873 athlete-exposures, of which 389 (0.8%) were stress fractures, resulting in an overall stress fracture rate of 1.54 per 100,000 athlete-exposures. Rates per 100,000 athlete-exposures were highest in girls’ cross country (10.62), girls’ gymnastics (7.43), and boys’ cross country (5.42). In sex-comparable sports, girls sustained more stress fractures (63.3%) than did boys (36.7%) and had higher rates of stress fracture (2.22 vs 1.27; rate ratio, 1.75; 95% CI, 1.38-2.23). The most commonly injured sites were the lower leg (40.3% of all stress fractures), foot (34.9%), and lower back/lumbar spine/pelvis (15.2%). Management was nonsurgical in 98.7% of the cases, and 65.3% of injuries resulted in ≥3 weeks of time loss, medical disqualification, or an end to the season before athletes could return to play. Conclusion: Although a rare injury, stress fractures cause considerable morbidity for high school athletes of both sexes. Future research should evaluate risks of stress fractures to drive development of targeted prevention efforts.

RANK/RANKL/OPG pathway: Genetic associations with stress fracture period prevalence in elite athletes

ContextThe RANK/RANKL/OPG signalling pathway is important in the regulation of bone turnover, with single nucleotide polymorphisms (SNPs) in genes within this pathway associated with bone phenotypic adaptations. ObjectiveTo determine whether four SNPs associated with genes in the RANK/RANKL/OPG signalling pathway were associated with stress fracture injury in elite athletes. Design, participants, and methodsRadiologically confirmed stress fracture history was reported in 518 elite athletes, forming the Stress Fracture Elite Athlete (SFEA) cohort. Data were analysed for the whole group and were sub-stratified into male and cases of multiple stress fracture groups. Genotypes were determined using proprietary fluorescence-based competitive allele-specific PCR assays. ResultsSNPs rs3018362 (RANK) and rs1021188 (RANKL) were associated with stress fracture injury (P<0.05). 8.1% of the stress fracture group and 2.8% of the non-stress fracture group were homozygote for the rare allele of rs1021188. Allele frequency, heterozygotes and homozygotes for the rare allele of rs3018362 were associated with stress fracture period prevalence (P<0.05). Analysis of the male only group showed 8.2% of rs1021188 rare allele homozygotes had suffered a stress fracture whilst 2.5% of the non-stress fracture group were homozygous. In cases of multiple stress fractures, homozygotes for the rare allele of rs1021188 and individuals possessing at least one copy of the rare allele of rs4355801 (OPG) were shown to be associated with stress fracture injury (P<0.05). ConclusionsThe data support an association between SNPs in the RANK/RANKL/OPG signalling pathway and the development of stress fracture injury. The association of rs3018362 (RANK) and rs1021188 (RANKL) with stress fracture injury susceptibility supports their role in the maintenance of bone health and offers potential targets for therapeutic interventions.

Biomechanical Risk Factors for Lower Extremity Stress Fracture

Objectives:Stress fracture injuries disproportionately affect athletes and military service members and little is known about the modifiable biomechanical risk factors associated with these injuries. The purpose of this study was to prospectively examine the association between neuromuscular and biomechanical factors upon entry to military service and the subsequent incidence of lower-extremity stress fracture injury during four years of follow-up.Methods:We analyzed data from the JUMP-ACL cohort, an existing prospective cohort study of military cadets. JUMP-ACL conducted detailed motion analysis during a jump landing task at the initiation of each subject’s military career. We limited our analyses to the class years 2009-2013 (i.e., subjects who completed baseline testing in 2005-2008). There were 1895 subjects available for analysis. Fifty-two subjects reported a history of stress fracture at baseline and were excluded from further analysis leaving 1843 subjects. Incident lower extremity-stress fracture cases were identified through the Defense Medical Surveillance System and the Cadet Injury and Illness Tracking System during the follow-up period. The electronic medical records of each potential incident case were reviewed and each case was confirmed by an adjudication committee consisting of two sports medicine fellowship trained orthopaedic surgeons. The primary outcome of interest was the incidence rate of lower-extremity stress fracture during the follow-up period. The association between incident stress fracture and sagittal, frontal, and transverse plane hip and knee kinematics during the jump-landing task were examined at initial contact (IC), 15%(T15), 50%(T50), 85%(T85) and 100%(T100) of stance phase. Descriptive plots of all biomechanical variables along with 95% confidence intervals (CI) were generated during the stance phase of the jump landing task. Univariate and multivariable Poisson regression models were used to estimate the association between baseline biomechanical factors and the incidence rate of lower-extremity stress fracture during follow-up.Results:Overall, 94 (5.1%, 95%CI: 4.14, 6.21) subjects sustained an incident stress fracture during the follow-up period. The incidence rate for stress fracture injuries among females was nearly three times greater when compared to males (IRR=2.86, 95%CI: 1.88, 4.34, p<0.001). Compared to those with greater than 5° of knee valgus, subjects with neutral or varus knee alignment experienced incidence rates for stress fracture that were 43%-53% lower at IC (IRR=0.57, 95%CI: 0.29, 1.11, p=0.10), T50 (IRR=0.47, 95%CI=0.23, 1.00, p=0.05), and T85 (IRR=0.53, 95%CI: 0.29, 0.98, p=0.04). Subjects with greater than 5° of internal knee rotation exhibited rates for stress fracture that were 2-4 times higher at T15 (IRR=2.31, 95%CI: 1.01, 5.27, p=0.05), T50 (IRR=3.98, 95%CI: 0.99, 16.00, p=0.05), and T85 (IRR=2.31, 95%CI: 0.86, 6.23, p=0.10), when compared to those with neutral or external knee rotation alignment.Conclusion:Several potentially modifiable biomechanical factors at the time of entry into military service appear to be associated with the subsequent rate of stress fracture. It is possible that injury prevention programs targeted to address these biomechanical movement patterns may reduce the risk of stress fracture injury in athletes and military service members.