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While it is known that excessive accumulation of fatigue damage from daily activities contributes to fracture, a model of bone failure under physiologically relevant multiaxial cyclic loading needs to be developed in order to develop effective management strategies for stress or fatigue fractures. The role of strain-induced damage from repetitive loading is a strong candidate for such a model, as cycles of mechanical loading leading to failure can be measured directly. However, this approach has been limited by the restrictions of uniaxial loading models, which often overestimates the fatigue life of bone and suggests that bone will only break well beyond the realistic limits of exercise. To address this gap and develop a physiologically relevant model, our study leverages the power of four commonly used engineering failure criteria as a model for multiaxial loading using a cohort of human tibiae from cadaveric donors (age range 21-85 years old). Four failure criteria (Von Mises, Tsai-Wu, Findley critical plane, and maximum shear strain) were found to be effective in vitro models of tibial fracture when age groups of donors were combined (r 2  > 0.84) and stratified (younger: 21-52-years-old versus older: 57-85-years-old) (r 2  > 0.83) (p < 0.001). Each failure criterion displayed distinctly lower fatigue curves for the older age group. The maximum shear strain model was used to determine the efficacy of this approach to predict fatigue fractures in humans using published in vivo data from human volunteers. Consistent with in vivo observations in general population, the model demonstrated failure at 5000 to 200,000 loading cycles depending on activities such as jumping, sprinting, and walking, with a 3-fold reduction of fatigue life in older donors. These findings dramatically improve estimates of fatigue life under repetitive loading and demonstrate how age-related changes in bone significantly increase its propensity for fatigue-induced fractures., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Introduction: Fragility fractures without significant trauma of the pelvic ring in older patients have an increasing incidence due to demographic change. Influencing factors other than osteoporotic bone quality that lead to an insufficiency fracture are not yet known. However, it is suspected that the pelvic tilt (PT) has an effect on the development of such an insufficiency fracture. This study explores the influence of the PTs in patients with insufficiency fractures of the posterior pelvic ring., Materials and Methods: A total of 49 geriatric patients with fragility fractures of the pelvic ring were treated at a university hospital level-1 trauma center during a period between February and December 2023, and their fractures were classified according to the FFP classification of Rommens and Hofmann. Complete sets of computer tomography (CT) and radiological images were available to determine the PT angle of the patients., Results: 34 FFP type 2 and 15 FFP type 3 classified patients were included in the study. Significant difference was seen in the pelvic tilt (PT) angle between the patient group with insufficiency fractures (n= 49; mean age: 78.02 ± 11.80) and the control group with lumbago patients (n= 53; mean age: 69.23 ± 11.23). The PT was significantly higher in the patients with insufficiency fractures (25.74° ± 4.76; p ⁎⁎⁎⁎ ≤ 0.0001)., Conclusions: The study demonstrates a significant extension of the PT angle of individuals with insufficiency fractures when compared to those with lumbago. The result suggests a potential association between pelvic tilt and fracture susceptibility., Trial Registration: A retrospective study about the influence of sagittal balance of the spine on insufficiency fractures of the posterior pelvic ring measured by the "pelvic tilt angle", DRKS00032120. Registered 20th June 2023 - Prospectively registered. Trial registration number DRKS00032120., Competing Interests: Declaration of competing interest The authors declare that they have no financial and non-financial conflict of interest., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Clinical Scenario: Stress fractures are one of the most common injuries in athletes. Unfortunately, they are hard to diagnose, require multiple radiology exams and follow-up which leads to more exposure to radiation and an increase in cost. Stress fractures that are mismanaged can lead to serious complications and poorer outcomes for the athlete. During the rehabilitation process, it would be beneficial to be able to monitor the healing of fractures to know when it is safe to gradually allow a patient to a return to sport because the return to activity is not usually objective and based on pain level., Clinical Question: Can infrared thermography (IRT) be a useful tool to measure the pathophysiological state of the fracture healing? The aim of this critically appraised topic is to analyze the current evidence of IRT for measuring the temperature change in fractures to provide recommendations for medical practitioners., Summary of Key Findings: For this critically appraised topic, we examined 3 articles that compared medical imaging and IRT over multiple time points during the follow-up. The 3 articles concluded that a 1 °C asymmetry in temperature followed by a return to normal (less than 0.3 °C) temperature during the healing process of fractures can be monitored using IRT., Clinical Bottom Line: Once the patient has been diagnosed with a fracture, IRT can safely be used to monitor the evolution of a fracture. When the thermogram progresses from a hot thermogram to a cold thermogram, the healing is considered good enough to return to sport., Strength of Recommendation: Grade 2 evidence exists to support IRT being used by clinicians to monitor fracture healing. Due to the limited research and novelty of the technology, the current recommendations are for following the treatment of the fracture once the initial diagnosis is made.

Purpose: To determine differences in health and physical activity history, bone density, microarchitecture, and strength among female athletes with a history of multiple BSI, athletes with ≤1 BSI, and nonathletes., Methods: We enrolled 101 women (age, 18-32 yr) for this cross-sectional study: nonathlete controls (n = 17) and athletes with a history of ≥3 BSIs (n = 21) or ≤1 BSI (n = 63). We collected subjects' health and training history and measured bone microarchitecture of the distal tibia via high-resolution peripheral quantitative computed tomography (HR-pQCT) and areal bone mineral density of the hip and spine by dual-energy X-ray absorptiometry., Results: Groups did not differ according to age, body mass index, age at menarche, areal bone mineral density, or tibial bone microarchitecture. Women with multiple BSI had a higher prevalence of primary and secondary amenorrhea (P < 0.01) compared with other groups. Total hours of physical activity in middle school were similar across groups; however, women with multiple BSI performed more total hours of physical activity in high school (P = 0.05), more hours of uniaxial loading in both middle school and high school (P = 0.004, P = 0.02), and a smaller proportion of multiaxial loading activity compared with other groups., Conclusions: These observations suggest that participation in sports with multiaxial loading and maintaining normal menstrual status during adolescence and young adulthood may reduce the risk of multiple bone stress injuries., (Copyright © 2021 by the American College of Sports Medicine.)

Bone stress injuries (BSIs) occur at inopportune times to invariably interrupt training. All BSIs in runners occur due to an "error" in workload wherein the interaction between the number and magnitude of bone tissue loading cycles exceeds the ability of the tissue to resist the repetitive loads. There is not a single optimal bone workload, rather a range which is influenced by the prevailing scenario. In prepubertal athletes, optimal bone workload consists of low-repetitions of fast, high-magnitude, multidirectional loads introduced a few times per day to induce bone adaptation. Premature sports specialization should be avoided so as to develop a robust skeleton that is structurally optimized to withstand multidirectional loading. In the mature skeleton, optimal workload enables gains in running performance but minimizes bone damage accumulation by sensibly progressing training, particularly training intensity. When indicated (e.g., following repeated BSIs), attempts to reduce bone loading magnitude should be considered, such as increasing running cadence. Determining the optimal bone workload for an individual athlete to prevent and manage BSIs requires consistent monitoring. In the future, it may be possible to clinically determine bone loads at the tissue level to facilitate workload progressions and prescriptions., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.)

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., (© 2021. Crown.)

There is mounting evidence suggesting that the commonly used analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), may inhibit new bone formation with physical training and increase risk of stress fractures in physically active populations. Stress fractures are thought to occur when bones are subjected to repetitive mechanical loading, which can lead to a cycle of tissue microdamage, repair, and continued mechanical loading until fracture. Adaptive bone formation, particularly on the periosteal surface of long bones, is a concurrent adaptive response of bone to heightened mechanical loading that can improve the fatigue resistance of the skeletal structure, and therefore may play a critical role in offsetting the risk of stress fracture. Reports from animal studies suggest that NSAID administration may suppress this important adaptive response to mechanical loading. These observations have implications for populations such as endurance athletes and military recruits who are at risk of stress fracture and whose use of NSAIDs is widespread. However, results from human trials evaluating exercise and bone adaptation with NSAID consumption have been less conclusive. In this review, we identify knowledge gaps that must be addressed to further support NSAID-related guidelines intended for at-risk populations and individuals.

Background: Tibial stress injuries are frequent injuries of the lower extremity and the most common causes of exercise-induced leg pain among athletes and military recruits. They sometimes occur in patients with pathological conditions of bone metabolism such as osteoporosis or rheumatoid arthritis, but there are previously no cases reported in juvenile dermatomyositis (JDM). Here we report 6 JDM patients who presented with shin pain, and the imaging appearance of tibial stress fractures or stress reactions., Case Presentation: All 6 patients with JDM presented with shin pain or tenderness in the anterior tibia without any evidence of excessive exercise or traumatic episode. They were diagnosed with tibial stress injuries based on a combination of radiographs, three-phase bone scans, and magnetic resonance imaging (MRI), and 5 out of 6 patients had been treated with prednisone and/or methotrexate at onset of tibial stress injuries. In one patient, we could not find any abnormalities in his radiograph, but the subsequent MRI showed tibial stress reaction. In all 6 patients, the tibial stress injuries improved with only rest and/or analgesics., Conclusion: We experienced 6 children with JDM who presented with shin pain, and who were diagnosed with tibial stress fractures or stress reactions. Their underlying disease and weakness, treatment with glucocorticoid and methotrexate, or inactivity may have resulted in these tibial injuries, and made these patients more predisposed than other children. In addition to preventing JDM patients from getting osteoporosis, we need to consider stress reactions when children with JDM complain of sudden shin pain.

Tibial stress fractures are a problematic injury among runners. Increased loading of the tibia has been observed following prolonged weight-bearing activity and is suggested to be the result of reduced activity of the plantar flexor muscles. The musculature that spans the tibia contributes to bending of the bone and influences the magnitude of stress on the tibia during running. Participant-specific models of the tibia can be used as a non-invasive estimate of tibial stress. This study aimed to quantify tibial stress during running using participant-specific bone geometry and to compare tibial stress before and after a protocol of repeated muscular contractions of the plantar flexor muscle group. Fourteen participants who run recreationally were included in the final analysis of the study. Synchronized force and kinematic data were collected during overground running before and after an exhaustive, weighted calf-raise protocol. Bending moments and stress at the distal third of the tibia were estimated using beam theory combined with inverse dynamics and musculoskeletal modeling. Bone geometry was obtained from magnetic resonance images. There was no difference in stress at the anterior, posterior, medial, or lateral peripheries of the tibia after the calf-raise protocol compared with before. These findings suggest that an exhaustive, repeated calf-raise protocol did not alter tibial stress during running., (© 2020 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

Sacral stress fractures are rare injuries among professional and amateur athletes and are considered to be an uncommon source of low back pain. These type of fractures are mainly seen in competitive, high-impact sports, most commonly in long-distance runners. Sacral stress fractures are usually overlooked in young patients presenting with low back pain without any trauma history. Diagnosis of sacral stress fractures is often delayed because the history and physical examination of these patients are not specific and conventional radiographic images are frequently inadequate. A high index of clinical suspicion and further radiologic imaging such as MRI utilization can provide the accurate diagnosis. The treatment mainly includes rest, pain control, nutritional support, and biomechanical optimization. Herein, we report the case of a woman amateur golf player with a sacral stress fracture who complained of aggravating low back pain. To the best of our knowledge, this appears to be the first report of a sacral stress fracture in a golf player and also the first case of this pathology in low-impact sports. Therefore, physicians should keep in mind that stress fractures can also be seen in low-impact sports. We recommend considering stress fractures in the differential diagnosis of non-traumatic, aggravating low back pain in golfers.

Context: Lower-extremity stress fractures (SFx) are a common occurrence during load-bearing activities of jumping and landing. To detect biomechanical changes during jumping postinjury, a fatigue model could be used., Objective: To evaluate muscle activation in the lower leg and tibial accelerations (TAs) prefatigue to postfatigue following a jumping task in those with and without a history of SFx., Design: Repeated-measures., Setting: Athletic Training Research Lab., Participants: A total of 30 active college-aged students with and without a history of lower-extremity (leg or foot) SFx (15 males and 15 females; 21.5 [5.04] y, height = 173.5 [12.7] cm, weight = 72.65 [16.4] kg)., Intervention: A maximal vertical jump on one leg 3 times with arms folded across the chest prefatigue to postfatigue was performed. Fatigue protocol was standing heel raises on a custom-built platform at a pace controlled by a metronome until task failure was reached. Legs were tested using a randomized testing order. Electromyographic (EMG) surface electrodes were placed on the medial gastrocnemius, soleus, and tibialis anterior following a standardized placement protocol. A triaxial accelerometer was attached to the proximal anteromedial surface of the tibia., Main Outcome Measures: Linear envelopes of the medial gastrocnemius, soleus, and tibialis anterior and peak accelerations (resultant acceleration takeoff and landing)., Results: Significant interaction for leg × test for tibialis anterior with a posttest difference between SFx and control (P = .05). There were decreases in EMG linear envelope following fatigue for medial gastrocnemius (P < .01) and tibialis anterior (P = .12) pretest to posttest. At takeoff, TA was greater in the SFx contralateral leg in comparison with the control leg (P = .04). At landing, TA was greater in posttest (P < .01) and in the SFx leg compared with SFx contralateral (P = .14)., Conclusion: A decrease in muscle activity and an increase in TA following fatigue were noted for all subjects but especially for those with a history of SFx.

Objective: To determine performance and repair kinetics of the ChonDux hydrogel scaffold for treating focal articular cartilage defects in the knee over 24 months., Design: This assessor-blinded trial evaluates ChonDux hydrogel scaffold implantation in combination with microfracture in 18 patients across 6 sites. Male and female patients 18 to 65 years of age with full-thickness femoral condyle defects 2 to 4 cm 2 in area were enrolled. Eligible patients received ChonDux treatment followed by rehabilitation. Defect volume fill was evaluated after 3, 6 (primary outcome), 12, 18, and 24 months by assessor blinded magnetic resonance imaging (MRI) analysis. Secondary outcomes were T2-weighted MRI relaxation time and patient surveys via visual analogue scale (VAS) pain and International Knee Documentation Committee (IKDC) knee function scoring., Results: ChonDux maintained durable tissue restoration over 24 months with final defect percent fill of 94.2% ± 16.3% and no significant loss of fill volume at any time points. Tissues treated with ChonDux maintained T2 relaxation times similar to uninjured cartilage between 12 and 24 months. VAS pain scoring decreased between 1 and 6 weeks, and IKDC knee function scores improved by approximately 30.1 with ChonDux over 24 months., Conclusion: ChonDux treatment is a safe adjunct to microfracture therapy and promotes stable restoration of full thickness articular cartilage defects for at least 24 months.

Soft tissue preservation in fossil birds provides a rare window into their anatomy, function, and development. Here, we present an exceptionally-preserved specimen of Confuciusornis which, through Laser-Stimulated Fluorescence imaging, is identified as preserving a disassociated rhamphotheca. Reconstruction of the in vivo position of the rhamphotheca validates the association of the rhamphotheca with two previous confuciusornithid specimens while calling that of a third specimen into question. The ease of dissociation is discussed and proposed with a fourth specimen alongside finite element analysis as evidence for preferential soft-food feeding. However, this proposition remains tentative until there is a better understanding of the functional role of beak attachment in living birds. Differences in post-rostral extent and possibly rhamphotheca curvature between confuciusornithids and modern birds hint at developmental differences between the two. Together, this information provides a wealth of new information regarding the nature of the beak outside crown Aves.

To comprehend the most detrimental characteristics behind bone fractures, it is key to understand the material and tissue level strain limits and their relation to failure sites. The aim of this study was to investigate the three-dimensional strain distribution and its evolution during loading at the sub-trabecular level in trabecular bone tissue. Human cadaver trabecular bone samples were compressed in situ until failure, while imaging with high-resolution synchrotron radiation X-ray tomography. Digital volume correlation was used to determine the strains inside the trabeculae. Regions without emerging damage were compared to those about to crack. Local strains in close vicinity of developing cracks were higher than previously reported for a whole trabecular structure and similar to those reported for single isolated trabeculae. Early literature on bone fracture strain thresholds at the tissue level seem to underestimate the maximum strain magnitudes in trabecular bone. Furthermore, we found lower strain levels and a reduced ability to capture detailed crack-paths with increased image voxel size. This highlights the dependence between the observed strain levels and the voxel size and that high-resolution is needed to investigate behavior of individual trabeculae. Furthermore, low trabecular thickness appears to be one predictor of developing cracks. In summary, this study investigated the local strains in whole trabecular structure at sub-trabecular resolution in human bone and confirmed the high strain magnitudes reported for single trabeculae under loading and, importantly extends its translation to the whole trabecular structure.

Background: Scapular fractures following reverse total shoulder arthroplasty (RSA) are devastating complications with substantial functional implications. The role of the coracoacromial ligament (CAL), which is often transected during surgical exposure for RSA, is not fully known. We hypothesized that the CAL contributes to the structural integrity of the "scapular ring" and that the transection of this ligament during RSA alters the scapular strain patterns., Methods: RSA was performed on 8 cadaveric specimens without evidence of a prior surgical procedure in the shoulder. Strain rosettes were fixed onto the acromial body (at the location of Levy type-II fractures) and the scapular spine (Levy type III). With use of a shoulder simulator, strains were recorded at 0°, 30°, and 60° glenohumeral abductions before and after CAL transection. The deltoid and glenohumeral joints were functionally loaded (middle deltoid = 150 N, posterior deltoid = 75 N, and joint compression = 300 N). Maximum principal strains were calculated from each rosette at each abduction angle. A repeated-measures analysis of variance with post hoc analysis was performed to compare the maximum principal strain at each abduction angle., Results: With the CAL intact, there was no significant difference between strain experienced by the acromion and scapular spine at 0°, 30°, and 60° of glenohumeral abduction. CAL transection generated significantly increased strain in the scapular spine at all abduction angles compared with an intact CAL. The maximum scapular spine strain observed was increased 19.7% at 0° of abduction following CAL transection (1,216 ± 300.0 microstrain; p = 0.011). Following CAL transection, acromial strains paradoxically decreased at all abduction angles (p < 0.05 for all). The smallest strains were observed at 60° of glenohumeral abduction at the acromion following CAL transection (296 ± 121.3 microstrain; p = 0.048)., Conclusions: The CAL is an important structure that completes the "scapular ring" and therefore serves to help distribute strain in a more normalized fashion. Transection of the CAL substantially alters strain patterns, resulting in increased strain at the scapular spine following RSA., Clinical Relevance: CAL preservation is a modifiable risk factor that may reduce the risk of bone microdamage and thus the occurrence of fatigue/stress fractures in the scapular spine following RSA.

Stress fractures are common among elite ballet dancers whereby musculoskeletal health may be affected by energy balance and overtraining., Purpose: This study aimed to characterize bone health in relation to stress fracture history, body composition, eating disorder risk, and blood biomarkers in professional male and female ballet dancers., Methods: A single cohort of 112 dancers (male: 55, 25 ± 6 yr; female: 57, 24 ± 6 yr) was recruited. All participants underwent bone and body composition measures using dual-energy x-ray absorptiometry. In a subset of our cohort (male: 30, 24 ± 6 yr; female, 29, 23 ± 5 yr), a blood panel, disordered eating screen, menstrual history, and stress fracture history were also collected. Age-matched Z scores and young-adult T scores were calculated for bone mineral density (BMD) and body composition. Independent-samples t-tests and Fisher's exact tests were used to compare BMD, Z-scores, T scores, and those with and without history of stress fractures. A 1 × 3 ANOVA was used to compare BMD for those scoring 0-1, 2-6, and 7+ using the EAT26 questionnaire for eating disorder risk. Regression was used to predict BMD from demographic and body composition measures., Results: Female dancers demonstrated reduced spinal (42nd percentile, 10%T < -1) and pelvic (16th percentile, 76%T < -1) BMD. Several anthropometric measures were predictive of BMD (P < 0.05, r = 0.65-0.81, standard error of estimate = 0.08-0.10 g·cm, percent error = 6.3-8.5). Those scoring >1 on EAT26 had lower BMD than did those with a score of 0-1 (P < 0.05)., Conclusions: Professional female ballet dancers exhibit reduced BMD, fat mass, and lean mass compared with the general population whereby low BMD and stress fractures tend to be more prevalent in those with a higher risk of disordered eating. Anthropometric and demographic measures are predictive of BMD in this population.

Background: Recruits undergoing military training experience a particularly high incidence of stress fractures. The role of combined calcium and vitamin D (25-OHD) deficiency and subsequent supplementation has been well described in the literature, but the role of 25-OHD deficiency alone is less well understood, particularly its influence on recovery once a stress fracture has been incurred., Methods: Retrospective data of recruits who had incurred stress fractures were collected (n=37). Independent-samples t-tests were conducted in Microsoft Excel to investigate the association between serum-25 OHD and the time taken to recover., Results: Significant differences (p<0.05) were found in the mean time taken to recover from stress fractures when participants were grouped according to serum 25-OHD level. Sufficient levels of serum 25-OHD (>50 nmol/L) at the time of injury resulted in shorter recovery times than all other groups., Conclusion: The study demonstrated an association between serum 25-OHD level and the time taken to recover from a stress fracture. The sample population of this study was too small to contribute to the discussion about whether a minimum serum 25-OHD status should be met before entering British Army training, but a larger prospective study should be able to provide the data required for a cost benefit analysis to be conducted and a decision made., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Female runners are at increased risk of stress fractures (SFs) compared with men. Literature is lacking with regard to best practice for preventing and treating SFs in women. The purpose of the study was to compare physiological measures and running-related factors between women of various ages and running abilities with and without a history of running-related SFs., Hypothesis: Women with and without SF histories will differ with regard to medical and menstrual history, bone health, body composition, nutrition, and running history., Study Design: Prospective cohort study., Level of Evidence: Level 2., Methods: A total of 20 female runners with SF histories were matched based on age and running distance with 20 women without SF histories. Data included medical, menstrual, running, injury, and nutritional histories; blood histology related to nutritional, hormonal, and bone-related risk factors; and bone density, fat, and lean tissue using dual energy x-ray absorptiometry. Paired t tests were used to examine differences between women with and without SF histories, and Spearmen correlations were conducted to examine relationships between physiological factors., Results: Women with SF histories had lower hip bone mineral density compared with women without SF histories ( P < 0.05). SF history was moderately correlated with menstrual changes during increased training times ( r = 0.580; P < 0.0001) but was not correlated with any other physiological factor. There was a moderate correlation within the SF group ( r = 0.65; P = 0.004) for bone markers for resorption and formation both increasing, indicating increased bone turnover., Conclusion: Female runners with low hip bone mineral density, menstrual changes during peak training, and elevated bone turnover markers may be at increased risk of SF., Clinical Relevance: Female runners need routine screening for risks associated with SF occurrence. As bone mineral density and bone turnover markers are not routinely assessed in this population, important risk factors may be missed.

Stress fractures of the first rib occur infrequently in adolescent athletes; therefore, there have been few case reports. Initial radiographs do not always lead to the diagnosis of first rib stress fractures. This study proposed a classification system and a possible mechanism for stress fractures of the first rib using three-dimensional computed tomography (3D-CT). The data of 10 stress fractures of the first rib in adolescent athletes obtained using 3D-CT between 2007 and 2018 were reviewed. Fractures of the first rib were classified according to the location and type of the fracture line. Stress fractures of the first rib were classified into three types: type 1, center-transverse fracture; type 2, center to posterior-oblique fracture; and type 3, posterior-transverse fracture. There were three type 1 fractures, five type 2 fractures, and two type 3 fractures. The fracture lines of types 1 and 2 were on the deep groove of the subclavian artery between the anterior and middle scalene muscle attachments, which is the thinnest and weakest portion of the first rib. However, the fracture line of type 3 was across the posterior part of the first rib and located slightly away from the deep groove of the subclavian artery. A 3D-CT classification of stress fractures of the first rib in adolescent athletes was proposed. Our results suggested that there are three types of the fracture and different mechanisms that cause this type of injury. This classification system helped to implement adequate conservative therapeutic plans based on the proposed mechanism.

Context: Military service members commonly sustain lower extremity stress fractures (SFx). How SFx risk factors influence bone metabolism is unknown. Understanding how SFx risk factors influence bone metabolism may help to optimize risk-mitigation strategies., Objective: To determine how SFx risk factors influence bone metabolism., Design: Cross-sectional study., Setting: Military service academy., Patients or Other Participants: Forty-five men (agepre = 18.56 ± 1.39 years, heightpre = 176.95 ± 7.29 cm, masspre = 77.20 ± 9.40 kg; body mass indexpre = 24.68 ± 2.87) who completed Cadet Basic Training (CBT). Individuals with neurologic or metabolic disorders were excluded., Intervention(s): We assessed SFx risk factors (independent variables) with (1) the Landing Error Scoring System (LESS), (2) self-reported injury and physical activity questionnaires, and (3) physical fitness tests. We assessed bone biomarkers (dependent variables; procollagen type I amino-terminal propeptide [PINP] and cross-linked collagen telopeptide [CTx-1]) via serum., Main Outcome Measure(s): A markerless motion-capture system was used to analyze trunk and lower extremity biomechanics via the LESS. Serum samples were collected post-CBT; enzyme-linked immunosorbent assays determined PINP and CTx-1 concentrations, and PINP : CTx-1 ratios were calculated. Linear regression models demonstrated associations between SFx risk factors and PINP and CTx-1 concentrations and PINP : CTx-1 ratio. Biomarker concentration mean differences with 95% confidence intervals were calculated. Significance was set a priori using α ≤ .10 for simple and α ≤ .05 for multiple regression analyses., Results: The multiple regression models incorporating LESS and SFx risk factor data predicted the PINP concentration (R2 = 0.47, P = .02) and PINP : CTx-1 ratio (R2 = 0.66, P = .01). The PINP concentration was increased by foot internal rotation, trunk flexion, CBT injury, sit-up score, and pre- to post-CBT mass changes. The CTx-1 concentration was increased by heel-to-toe landing and post-CBT mass. The PINP : CTx-1 ratio was increased by foot internal rotation, lower extremity sagittal-plane displacement (inversely), CBT injury, sit-up score, and pre- to post-CBT mass changes., Conclusions: Stress fracture risk factors accounted for 66% of the PINP : CTx-1 ratio variability, a potential surrogate for bone health. Our findings provide insight into how SFx risk factors influence bone health. This information can help guide SFx risk-mitigation strategies., (© by the National Athletic Trainers' Association, Inc.)

Background: Bizarre parosteal osteochondromatous proliferation (BPOP) is a relatively rare benign extraperiosteal osteochondroma-like proliferative lesion that shares similarities with malignant tumours in terms of morphology. The aetiology of BPOP has yet to be determined and there are no previous reports of BPOP associated with fracture., Case Presentation: A 57-year-old woman presented with a one-month history of pain and swelling in her right foot, which were worsened by activity and improved with rest. Physical examination revealed a hard, non-mobile mass measuring 1.5 cm × 1.5 cm on the dorsal aspect of the third metatarsal of the right foot. There was overlying erythema and tenderness on palpation. Computed tomography (CT) of the right foot demonstrated a fracture of the neck of the third metatarsal, osteolysis at the fracture site and soft tissue swelling. Bone scintigraphy revealed increased tracer uptake suggesting abnormal bone metabolism at the neck of the third metatarsal. Surgical excision of the lesion was performed. Histopathology and immunohistochemistry confirmed the diagnosis of BPOP., Conclusion: BPOP is a rare benign lesion that is commonly misdiagnosed. Differential diagnosis is mainly achieved through imaging and histopathological assessment.

Background: Military personnel are required to run while carrying heavy body-borne loads, which is suggested to increase their risk of tibial stress fracture. Research has retrospectively identified biomechanical variables associated with a history of tibial stress fracture in runners, however, the effect that load carriage has on these variables remains unknown., Research Question: What are the effects of load carriage on running biomechanical variables associated with a history of tibial stress fracture?, Methods: Twenty-one women ran at 3.0 m/s on an instrumented treadmill in four load carriage conditions: 0, 4.5, 11.3, and 22.7 kg. Motion capture and ground reaction force data were collected. Dependent variables included average loading rate, peak absolute free moment, peak hip adduction, peak rearfoot eversion, and stride frequency. Linear mixed models were used to asses the effect of load carriage and body mass on dependent variables., Results: A load x body mass interaction was observed for stride frequency only (p = 0.017). Stride frequency increased with load carriage of 22.7-kg, but lighter participants illustrated a greater change than heavier participants. Average loading rate (p < 0.001) and peak free moment (p = 0.015) were greater in the 22.7-kg condition, while peak rearfoot eversion (p ≤ 0.023) was greater in the 11.3- and 22.7-kg conditions, compared to the unloaded condition. Load carriage did not affect peak hip adduction (p = 0.67)., Significance: Participants adapted to heavy load carriage by increasing stride frequency. This was especially evident in lighter participants who increased stride frequency to a greater extent than heavier participants. Despite this adaptation, running with load carriage of ≥11.3-kg increased variables associated with a history of tibial stress fracture, which may be indicative of elevated stress fracture risk. However, the lack of concomitant change amongst variables as a function of load carriage may highlight the difficulty in assessing injury risk from a single measure of running biomechanics., Competing Interests: Declaration of Competing Interest The authors declare no competing interests. The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the United States Army, the U.S. Department of Defense, or The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. This paper has been approved for public release with unlimited distribution., (Copyright © 2020. Published by Elsevier B.V.)

Subject-specific features can contribute to the susceptibility of an individual to stress fracture. Here, we incorporated tibial morphology and material properties into a standard musculoskeletal finite-element (M/FE) model and investigated how load carriage influences joint kinetics and tibial mechanics in women. We obtained the morphology and material properties of the tibia from computed tomography images for women of three distinctly different heights, 1.51 m (short), 1.63 m (medium), and 1.75 m (tall), and developed individualized M/FE models for each. Then, we calculated joint and muscle forces, and subsequently, tibial stress/strain for each woman walking at 1.3 m/s under various load conditions (0, 11.3, or 22.7 kg). Among the subjects investigated, using individualized and standard M/FE models, the joint reaction forces (JRFs) differed by up to 4 (hip), 22 (knee), and 26% (ankle), and the 90th percentile von Mises stress by up to 30% (tall woman). Load carriage evoked distinct biomechanical responses, with a 22.7-kg load decreasing the peak hip JRF during late stance by ∼18% in the short woman, while increasing it by ∼39% in the other two women. It also increased peak knee and ankle JRFs by up to ∼48 (tall woman) and ∼36% (short woman). The same load increased the 90th percentile von Mises stress (and corresponding cumulative stress) by 31 (28), 22 (30), and 27% (32%) in the short, medium, and tall woman, respectively. Our findings highlight the critical role of individualized M/FE models to assess mechanical loading in different individuals performing the same physical activity.

Bone stress injuries (BSI) are common among distance runners and research investigations examining risk factors for BSI among men are limited. Therefore, investigations are needed to determine if men with a history of BSI have skeletal properties that may heighten BSI incidence., Objectives: To analyze differences in bone density, bone geometry, and estimates of bone strength in male runners with and without a BSI history., Design: Cross-sectional., Methods: We recruited 36 male distance runners ages 18-41 for this study. We used peripheral quantitative computed tomography (pQCT) to assess volumetric bone mineral density (vBMD, mg/mm 3 ), bone geometry (total and cortical bone area, mm 2 ), tibia robustness (total area/tibia length, mm) and estimates of bone strength (section modulus and polar strength-strain index, mm 3 ) at 5 tibial sites., Results: After adjusting for age, the BSI group had more slender tibias (9%), lower stress strain indices (-16%), lower section moduli (-17%) and smaller total cross-sectional (-11%) and cortical areas (-12%) at the 66% site of the tibia compared with controls (P < 0.05 for all). Similar differences were found at all other measurement sites. After adjusting for body size, differences in bone outcomes remained significant at the 66% site., Conclusions: These results indicate that men with a history of BSI have lower estimated bending strength compared to controls because of narrower tibias. However, differences are largely attenuated in the distal ½ of the tibia after adjusting for body size. Thus, smaller tibia size, particularly at the mid-diaphysis, may be an important indicator for BSI incidence., (Copyright © 2019 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Objective: Recurrent fifth metatarsal base stress fractures (MT5-BSF) in athletes present a challenging problem. The aim of this study was to evaluate the result of conservative treatment for the refracture of MT5-BSF after modified tension band wiring (MTBW)., Materials and Methods: The outcomes of 15 elite athletes undergoing conservative treatment for refracture of MT5-BSF after MTBW were retrospectively reviewed. They were instructed to avoid weight-bearing with short leg cast for 6 weeks. After that, they started partial weight with a postop shoe. Stepwise exercise followed bone union by radiographs., Results: Thirteen cases (86.6%) had a complete bone union after a mean of 18.9 ± 8.6 weeks. Twelve cases (80%) returned to their previous activity level and maintained for at least two consecutive seasons., Conclusion: Eighty percent of all athletic patients with the conservative treatment for refractures with healed MT5-BSF after MTBW on the plantar-lateral side could maintain and return to their previous sports activity for at least 2 years.

Background: Alterations in plantar loading patterns are risk factors for stress injuries of the lower limb, particularly of the foot and ankle. Epidemiological studies have revealed a higher incidence of soccer-related stress fractures of the fifth metatarsal (MT V) in younger athletes than in their adult counterparts., Objective: The aim of the present study was to assess the plantar pressure distributions of members of four high-level soccer teams of different age groups to identify age-related differences in loading patterns., Methods: A total of 65 elite soccer players were included in the study. Data were computed with sensor-loaded insoles (pedar® X system, novel Inc., Munich, Germany) while the players ran in soccer shoes. Plantar pressures for nine defined regions on the preferred and nonpreferred foot were analyzed., Results: The participants consisted of 17 elite male soccer professionals from the first national league (mean 23 years, height 184 cm, weight 81 kg), 14 players from the under-21 squad (U21, 20 years, 180 cm, 75 kg), 15 players from the U17 squad (16 years, 176 cm, 69 kg) and 19 players from the U16 squad (15 years, 179 cm, 70 kg). We detected statistically significantly elevated peak pressures on the lateral aspects of the nonpreferred foot compared with the preferred foot in the U16 and U17 players, corresponding to a relative increase by 29% (p= 0.044) in the lateral midfoot, a relative increase by 24% (p= 0.031) in MT heads 4-5 in the U16 players and a difference of 18% (p= 0.049) in the lateral midfoot in the U17 players. In contrast, the U21 and adult professional players displayed symmetric plantar pressure distributions in all foot regions., Conclusions: In contrast to adult elite soccer players, adolescents demonstrate asymmetric foot loading patterns with increased peak loads in the lateral aspects of the nonpreferred foot. Our results may provide some explanation for MT V stress fractures that occur in elite adolescents.

Case: This report describes the divergent course and management of bilateral patellar stress fractures in a 17-year-old skeletally immature male athlete. Beginning as bilateral incomplete tension-sided patellar fractures, the right patella healed uneventfully, whereas the left progressed to a complete, mildly displaced transverse fracture that eventually healed with nonoperative treatment measures to include temporary bracing, physical therapy, and vitamin D supplementation., Conclusions: Patellar stress fractures are exceptionally rare, particularly bilateral injuries in the pediatric population. Diligent workup is necessary for appropriate diagnosis, whereas knowledge of the salient features of these injuries is useful in treatment.

Introduction: Stress fractures of the tibia are a problematic injury among runners of all levels. Quantifying tibial stress using a modeling approach provides an alternative to invasive assessments that may be used to detect changes in tibial stress during running. This study aimed to assess the repeatability of a tibial stress model and to use this model to quantify changes in tibial stress that occur throughout the course of a 40-min prolonged treadmill run., Methods: Synchronized force and kinematic data were collected during prolonged treadmill running from 14 recreational male rearfoot runners on two separate occasions. During each session, participants ran at their preferred speed for two consecutive 20-min runs, separated by a 2-min pause. The tibia was modeled as a hollow ellipse and bending moments and stresses at the distal third of the tibia were estimated using beam theory combined with inverse dynamics and musculoskeletal modeling., Results: Intraclass correlation coefficients indicated good-to-excellent repeatability for peak stress values between sessions. Peak anterior and posterior stresses increased after 20 min of prolonged treadmill running and were 15% and 12% greater, respectively, after 40 min of running compared with the start of the run., Conclusion: The hollow elliptical tibial model presented is a repeatable tool that can be utilized to assess within-participant changes in peak tibial stress during running. The increased stresses observed during a prolonged treadmill run may have implications for the development of tibial stress fracture.

A 16-year-old female patient showed up at the orthopaedics unit complaining of intolerable pain on her left hip. While being questioned and her clinical history written down, she shared that as part of her daily exercise routine, she ran 10 miles (16 km) daily at a speed of 9.5-10.5 mph (15-17 km/hour). MRI was consequently ordered, confirming the presence of a stress fracture. Therefore, immediate suspension of physical activity was indicated, followed by the prescription of crutches as well as restricted weight bearing. Gradually, she recovered complete functionality and approximately a month after she had entirely healed. While on a skiing trip, again she abruptly developed an acute pain on her right hip. Another MRI was ordered; its result confirmed a new stress fracture. Her previous treatment has proved so successful, a conservative approach was once again prescribed for her, showing optimum results 6 months later., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Since stress fractures are common among adolescent athletes, it is important to identify bone assessment tools that accurately identify risk. We investigated the discriminative ability of two imaging technologies to classify at-risk athletes. Findings suggested that peripheral quantitative computed tomography (pQCT) has the ability to distinguish differences in bone structure in injured vs. uninjured limbs., Introduction: Given the high stress fracture (SFX) prevalence among adolescent girls, an understanding of the most informative assessment tools to identify SFX risks are required. We investigated the discriminative ability of pQCT vs. dual-energy X-ray absorptiometry (DXA) to classify athletes with or without SFX., Methods: Twelve adolescent athletes diagnosed with a lower-extremity SFX were compared with 12 matched controls. DXA measured areal bone mineral density (aBMD) and content of the total body, and lumbar spine. Bilateral tibiae were assessed with pQCT. At the metaphysis (3%), total density (ToD), trabecular density (TrD), trabecular area (TrA), and estimated bone strength in compression (BSIc), and at the diaphysis (38% and 66%), total bone area (ToA), cortical density (CoD), cortical area (CoA), estimated bone strength in torsion (SSIp), and peri- and endocortical and muscle area (MuA) were obtained. Cortical bone mass/density around the center of mass and marrow density (estimate of adiposity) were calculated using ImageJ software. General estimated equations adjusting for multiple comparisons (Holm-Bonferroni method) were used to compare means between (1) injured limb of the case athletes vs. uninjured limb of the control athletes and (2) uninjured limb of the case athletes vs. uninjured limbs of the controls and injured vs. uninjured limb of case athletes with a SFX., Results: aBMD and content showed no significant differences between cases and controls. When comparing the injured vs. uninjured leg in the case athletes by pQCT at the 3% tibia, unadjusted TrD, total density, and BSIc were significantly lower (p < 0.05) in the injured vs. uninjured leg. Marrow density at the 66% site was 1% (p < 0.05) lower in the injured vs. uninjured leg., Conclusions: These preliminary data in athletes with SFX suggest that pQCT has the ability to distinguish differences in bone structure in injured vs. uninjured limbs. No discriminative bone parameter classifications were identified between adolescent athletes with or without SFX.

Isolated bilateral pedicle stress fractures of the lumbar spine are rare events, and few cases are reported in the literature. Their occurrence is commonly related to post-operative complications of spine instrumentation but can also be associated with stress-related activities, degenerative spine conditions, trauma and other miscellaneous causes. The authors report a case of adjacent bi-level bilateral pedicle fracture that developed 5 years after an instrumented posterolateral lumbar fusion. We believe that this has never been described before, and we reviewed the current literature pertaining this subject.

Purpose: As running speed increases there are concomitant changes in loads associated with tibial stress fracture risk. Runners often include multiple speeds in their training, but the effect of speed distribution on load accumulation is unknown. We studied how running at different proportions of speed within a given running distance affects the cumulative loading of the vertical average loading rate, cumulative peak absolute tibial free moment, and cumulative peak axial tibial load. These loads were compared between two proportions of speed: running all distance at normal self-selected speed, and running the same distance at a combination of slow/fast speeds with the same average speed as normal. Also, the contributions of slow and fast running to the combined condition were compared., Methods: Forty-three recreational runners (age, 18-49 yr; 29 female, 14 male) ran around a 50-m indoor track for three laps each at self-selected slow, normal, and fast speeds. Per-step peak loads and cumulative loads per kilometer were calculated at each speed and for each speed distribution, respectively., Results: Only cumulative vertical average loading rate was lower at normal speed compared with the slow/fast speed combination. The contribution of fast speed running to cumulative tibial load was less than the contribution of slow speed running., Conclusions: Running at a combination of slow and fast speeds, rather than a single moderate speed, increased cumulative vertical average loading rate but not cumulative tibial load or free moment. Fast running can be included in a training program without necessarily increasing the cumulative load. Total distance and average speed may not be sufficient information to estimate cumulative load from running training.

A sacral pedicle stress fracture is an uncommon source of low back pain in adolescent athletes. Given the extensive differential diagnosis of low back pain coupled with the fact that nondirected specific imaging can be normal, diagnosis can be delayed. We report the case of a 15-year-old African American male, dual-sport athlete who experienced low back pain from a sacral pedicle stress fracture. This case highlights the importance of a thorough history and physical examination in tandem with appropriate testing to identify predisposing factors to ultimately arrive at a diagnosis. A comprehensive, conservative treatment approach is described., (© 2019 American Academy of Physical Medicine and Rehabilitation.)

Introduction: The Female Athlete Triad (Triad) is a syndrome describing three interrelated conditions: low energy availability (LEA), menstrual dysfunction, and low bone mineral density (BMD). Relative Energy Deficiency in Sport (RED-S) expands the Triad to include multiple physiologic consequences of LEA in both sexes. The purpose of this study is to determine the prevalence of factors associated with the Triad/RED-S in an elite para athlete population., Methods: Athletes were U.S. elite para athletes training to qualify for the 2016 or the 2018 Paralympic Games. Participants completed an online questionnaire characterizing nutrition, menstrual status (in females), bone health, and awareness of the Triad/RED-S., Results: The athletes were 260 elite para athletes (150 male, 110 female). While few reported prior eating disorder (3.1%), 32.4% had elevated Eating Disorder Examination Questionnaire (EDE-Q) pathologic behavior subscale scores. Most athletes (95 male, 65 female) were attempting to change their body composition or weight to improve performance. Forty-four percent of premenopausal females had oligomenorrhea/amenorrhea. Bone stress injury was reported in 9.2% of athletes; of these, 54.5% (n = 12) had low BMD. Less than 10% of athletes reported awareness of the Triad/RED-S., Conclusions: Factors associated with the Triad/RED-S are present in an elite para athlete population, regardless of sex or sport type. Awareness of the Triad/RED-S in para athletes is low. The consequences of LEA in para athlete populations are poorly understood. However, the high prevalence of factors observed suggests value in advancing screening tools and education efforts to optimize health in this population., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: A stress-riser fracture develops when stress in an object is higher than that in the surrounding material. The aim of this retrospective study was to evaluate all consecutive femoral stress-riser fractures during a period of >10 years and to verify high-risk factors by using mechanical analysis., Methods: Forty clinical fractures caused by local stress concentration in the femoral cortical bone were included. Risk factors were analyzed, and Sawbones models were used to verify their effect. One hundred thirty-six models were divided into 6 groups to simulate clinical cases of stress-riser fractures. A dynamic test instrument was used to simulate weight-bearing on the femoral head by continuous application of increasing axial force; the lever arm was applied at a constant speed of 0.1 mm/s until a fracture developed., Results: Female gender (57.5%), subtrochanteric area (40%), osteoporosis (40%), and technical or surgical errors (50%) were risk factors for stress-riser fractures in clinical analysis. Cortical perforation, tiny cracks, sharp corners, and changes in hardness were the main risk factors in biomechanical aspects. Mechanical analysis identified that these factors contributed to stress-riser fractures (P = 0.000), especially cortical perforations and sharp corners., Conclusion: A cortical perforation (screw hole), tiny crack (fracture line), sharp corner (bone cut), and change in hardness (tip of an implant or cement) can act as a stress riser. Screw holes are the most common and critical contributor to femoral stress-riser fractures., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Being overweight may increase the risk for developing stress fracture, as overweight adults and children were reported to have greater pressure peaks and rates under the heel during walking when compared with their normal-weight counterparts. Biofeedback gait retraining was shown to reduce ground impact magnitude in adults but not yet in children., Research Question: The study examined whether overweight children have greater tibia peak positive acceleration (PPA) at ground impact during fast walking and running compared to healthy weight children, and whether visual feedback gait retraining program can be used to reduce PPA in overweight children., Methods: Twenty five overweight and 12 healthy weight children participated in the study. Overweight children were randomly assigned into either feedback group or control no-feedback group of 8 sessions training program over 2-weeks. Tibia PPA at ground impact output from a wearable inertial sensor attached to the tibia was the feedback displayed on a monitor placed in front of the treadmill during walking and running., Results: Compared to healthy weight children, overweight participants showed significant greater PPA values in running (p < 0.05), but not in fast walking. Feedback group significantly reduced PPA by 16% (p < 0.01), and these changes persisted at the 1-month follow-up., Significance: Tibia PPA may be used in evaluating overweight children as a risk assessment to potential injuries due to high ground impact during running. Gait retraining using real-time feedback of tibia PPA may be useful in rehabilitation programs to reduce ground impact in overweight children., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: CARGEL (Smith & Nephew Inc.), a chitosan-based polymer scaffolding biomaterial, has been used since 2012 for treating articular cartilage lesions. Limited data are available on patient outcomes following CARGEL treatment. This study aimed to describe short-term clinical and radiographic outcomes in a cohort of patients treated with CARGEL and microfracture surgery for articular cartilage defects in the knee., Methods: A retrospective cohort study was conducted of consecutive patients with articular cartilage defects who had undergone microfracture surgery with CARGEL, or in patellar lesions microfracture and CARGEL plus Chondro-Gide (at SportsClinic Zurich). Study outcomes included reoperations, infections, allergic reactions, pain, swelling, range of motion, and tissue quality and quantity. Ethics approval was obtained from the local ethics committee on 05/09/2017 (Basec. Nr: 2017-01441)., Results: A total of 91 participants, with 93 treated lesions, consenting to chart review were included. No participants required reoperation due to complications on the index lesion. Fifteen participants had second-look surgery on the index knee for other reasons, allowing for visual confirmation of cartilage repair. No study participants experienced a post-surgical infection or suffered an allergic reaction. No significant changes in range of motion or T2 values were observed from pre-treatment to post-treatment follow-up. However, significant decreases were found in pain (P < 0.001) and swelling (P < 0.001), along with significant increases in MOCART II scores (P < 0.001). Similar results were found in a subgroup of patients with patellar lesions., Conclusions: Patients treated with CARGEL experienced few postoperative complications and reported promising reductions in pain and swelling after treatment., Level of Evidence: IV., (Copyright © 2018. Published by Elsevier B.V.)

Background: Postmenopausal osteoporosis develops due to a deficiency of estrogen that causes a decrease in bone mass and changes in the macro- and micro-architectural structure of the bone, leading to the loss of mechanical strength and an increased risk of fracture. Although the assessment of bone mineral density (BMD) has been widely used as a gold standard for diagnostic screening of bone fracture risks, it accounts for only a part of the variation in bone fragility; thus, it is necessary to consider other determinants of bone strength. Therefore, we aimed to comprehensively evaluate the architectural changes of the bone that influence bone fracture strength, together with the different sensitivities of cortical and trabecular bone in response to ovariectomy (OVX)., Methods: Bone morphology parameters were separately analyzed both in cortical and in trabecular bones, at distal-metaphysis, and mid-diaphysis of OVX rat femurs. Three-point bending test was performed at mid-diaphysis of the femurs. Correlation of OVX-induced changes of morphological parameters with breaking force was analyzed using Pearson's correlation coefficient., Results: OVX resulted in a decline in the bone volume of distal-metaphysis trabecular bone, but an increase in distal-metaphysis and mid-diaphysis cortical bone volume. Tissue mineral density (TMD) remained unchanged in both the trabecular and cortical bone of the distal metaphysis but decreased in cortical bone of the mid-diaphysis. The OVX significantly increased the breaking force at mid-diaphysis of the femurs., Conclusions: OVX decreased the trabecular bone volume of the distal-metaphysis and increased the cortical bone volume of the distal-metaphysis and mid-diaphysis. Despite the reduction in TMD and increased cortical porosity, bone fracture strength increased in the mid-diaphysis after OVX. These results indicate that analyzing a single factor, i.e., BMD, is not sufficient to predict the absolute fracture risk of the bone, as OVX-induced bone response vary, depending on the bone type and location. Our results strongly support the necessity of analyzing bone micro-architecture and site specificity to clarify the true etiology of osteoporosis in a clinical setting.

Background: Supra-acetabular insufficiency fractures (SAIFs) occur in the upper acetabulum and are rare compared with insufficiency sacral, femoral head, or ischial fractures. However, SAIFs are known to occur in low grade trauma, and the underlying mechanism is still remained unclear., Methods: We performed biomechanical analysis using finite element analysis to clarify the mechanisms underlying the development of SAIFs. Patient-specific models and bone mineral density (BMD) were derived from pelvic computed tomography data from two patients with SAIF (unaffected side) and two healthy young adults. The bone was assumed to be an isotropic, linearly elastic body. We assigned Young's modulus of each element to the pelvis based on the BMD, and reported the relationships for BMD-modulus. Clinically relevant loading conditions-walking and climbing stairs-were applied to the models. We compared the region of failure risk in each acetabulum using a maximum principal strain criterion., Results: The average supra-acetabular BMD was less than that of the hemi-pelvis and femoral head, but was higher than that of the femoral neck and greater trochanter. Greater minimum principal strain was concentrated in the supra-acetabular portion in both the SAIF and healthy models. In the SAIF models, the higher region of the failure risk matched the fracture site on the acetabulum., Conclusions: Relative fragility causes compressive strain to concentrate in the upper acetabulum when walking and climbing stairs. When presented with a patient complaining of hip pain without apparent trauma or abnormal X-ray findings, physicians should consider the possibility of SAIF and perform magnetic resonance imaging for the diagnosis of SAIF., (Copyright © 2018. Published by Elsevier B.V.)

Tibial stress fractures are a common and debilitating injury that occur in distance runners. Runners may be able to decrease tibial stress fracture risk by adopting a running pattern that reduces biomechanical parameters associated with a history of tibial stress fracture. The purpose of this study was to test the hypothesis that converting to a forefoot striking pattern or increasing cadence without focusing on changing foot strike type would reduce injury risk parameters in recreational runners. Running kinematics, ground reaction forces and tibial accelerations were recorded from seventeen healthy, habitual rearfoot striking runners while running in their natural running pattern and after two acute retraining conditions: (1) converting to forefoot striking without focusing on cadence and (2) increasing cadence without focusing on foot strike. We found that converting to forefoot striking decreased two risk factors for tibial stress fracture: average and peak loading rates. Increasing cadence decreased one risk factor: peak hip adduction angle. Our results demonstrate that acute adaptation to forefoot striking reduces different injury risk parameters than acute adaptation to increased cadence and suggest that both modifications may reduce the risk of tibial stress fractures., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A computational model was used to compare the local bone strengthening effectiveness of various isometric exercises that may reduce the likelihood of distal tibial stress fractures. The developed model predicts local endosteal and periosteal cortical accretion and resorption based on relative local and global measures of the tibial stress state and its surface variation. Using a multisegment 3-dimensional leg model, tibia shape adaptations due to 33 combinations of hip, knee, and ankle joint angles and the direction of a single or sequential series of generated isometric resultant forces were predicted. The maximum stress at a common fracture-prone region in each optimized geometry was compared under likely stress fracture-inducing midstance jogging conditions. No direct correlations were found between stress reductions over an initially uniform circular hollow cylindrical geometry under these critical design conditions and the exercise-based sets of active muscles, joint angles, or individual muscle force and local stress magnitudes. Additionally, typically favorable increases in cross-sectional geometric measures did not guarantee stress decreases at these locations. Instead, tibial stress distributions under the exercise conditions best predicted strengthening ability. Exercises producing larger anterior distal stresses created optimized tibia shapes that better resisted the high midstance jogging bending stresses. Bent leg configurations generating anteriorly directed or inferiorly directed resultant forces created favorable adaptations. None of the studied loads produced by a straight leg was significantly advantageous. These predictions and the insight gained can provide preliminary guidance in the screening and development of targeted bone strengthening techniques for those susceptible to distal tibial stress fractures., (Copyright © 2018 John Wiley & Sons, Ltd.)

Background: A stress fracture (SF) is a highly debilitating injury commonly experienced in United States Army Basic Combat Training (BCT). Body fat (BF) may be associated with this injury but previous investigations (in athletes) have largely used SF self-reports and lacked sufficient statistical power. This investigation developed an equation to estimate %BF and used that equation to examine the relationship between %BF and SF risk in BCT recruits., Methods: Data for the %BF predictive equation involved 349 recruits with BF obtained from dual-energy X-ray absorptiometry. %BF was estimated using body mass index (BMI, weight/height 2 ), age (yr), and sex in the entire population of BCT recruits over an 11-year period (n = 583,651). Medical information was obtained on these recruits to determine SF occurrence. Recruits were separated into deciles of estimated %BF and the risk of SFs determined in each decile., Results: The equation was %BF = - 7.53 + 1.43 ● BMI + 0.13 ● age - 14.73 ● sex, with sex either 1 for men or 0 for women (r = 0.88, standard error of estimate = 4.2%BF). Among the men, SF risk increased at the higher and lower %BF deciles: compared to men in the mean %BF decile, the risk of a SF for men in the first (lowest %BF) and tenth (highest %BF) decile were 1.27 (95%confidence interval (95%CI) = 1.17-1.40) and 1.15 (95%CI = 1.05-1.26) times higher, respectively. Among women, SF risk was only elevated in the first %BF decile with risk 1.20 (95%CI = 1.09-1.32) times higher compared to the mean %BF decile., Conclusions: Low %BF was associated with higher SF risk in BCT; higher %BF was associated with higher SF risk among men but not women.

Intravenous infusions of different iron formulations are recognized as a cause of hypophosphatemia. Chronic hypophosphatemia can alter bone metabolism and bone material structure. As a consequence, osteomalacia may develop and lead to bone fragility. Herein, we report a patient with Crohn's disease presenting with persistent hypophosphatemia and insufficiency fractures while receiving regular iron infusions due to chronic gastrointestinal bleeding. Previously, the patient regularly received vitamin D and also zoledronic acid. The patient underwent bone biopsy of the iliac crest that showed typical signs of osteomalacia with dramatically increased osteoid volume and decreased bone formation. Analysis of the bone mineralization density distribution (BMDD) revealed a more complex picture: On the one hand, there was a shift to higher matrix mineralization, presumably owing to low bone turnover; on the other hand, a broadening of the BMDD indicating more heterogeneous mineralization due to osteomalacia was also evident. This is the first report on changes of bone histomorphometry and bone matrix mineralization in iron-induced osteomalacia. © 2017 American Society for Bone and Mineral Research., (© 2017 American Society for Bone and Mineral Research.)

Repetitive fatigue loading can induce microdamage accumulation in bone matrix, which results in impaired mechanical properties and increased fracture susceptibility. However, the spatial distribution and time-variant process of microdamage accumulation in fatigue-loaded skeleton, especially for linear microcracks which are known to initiate bone remodeling, remain not fully understood. In this study, the time-varying process of the morphology and distribution of microcracks in rat ulnae subjected to uniaxial compressive fatigue loading was investigated. Right forelimbs of thirty four-month-old male Sprague-Dawley rats were subjected to one bout of cyclic ramp loading with 0.67 Hz at a normalized peak force of 0.055 N/g body weight for 6000 cycles, and the contralateral left ulnae were not loaded as the control samples. Ten rats were randomly euthanized on Days 3, 5, and 7 post fatigue loading. Our findings via two-dimensional histomorphometric measurements based on basic fuchsin staining and three-dimensional quantifications using contrast-enhanced micro-computed tomography (MicroCT) with precipitated BaSO 4 staining demonstrated that the accumulation of linear microcracks (increase in the amount of linear microcracks) on Day 5 was significantly higher than that on Day 3 and Day 7 post fatigue loading. Our histological and histomorphometric results revealed that linear microcrack density (Cr.Dn) in the tensile cortex at Days 3, 5 and 7 post fatigue loading was significantly higher than that in the compressive side, whereas linear microcrack length (Cr.Le) in the tensile cortex at Day 3 was significantly lower than that in the compressive cortex. Our findings revealed that microcrack accumulation exhibited a non-linear time-varying process at 3, 5 and 7 days post axial compressive fatigue loading (with observable peak Cr.Dn at Day 5). Our findings also revealed distinct distribution of microcrack density and morphology in rat ulnae with tensile and compressive strains, as characterized by more microcracks accumulated in tensile cortices, and longer cracks shown in compressive cortices., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Golfers may injure themselves as a result of repetitive asymmetrical loads exerted on the body by poor swing mechanics. If the repetitive sub-maximal loading is not removed, this repetitive loading will exceed the adaptive capacity of bone, eventually resulting in a stress fracture. Stress fracture of the scapula due to golfing is extremely rare. Only two cases of acromion fracture have been reported. A rare case of nontraumatic coracoid fracture in a 50-year-old female beginner golfer is reported here. The mechanism of injury is also discussed. Level of evidence Level IV.

Asymptomatic cartilage lesions of the shoulder are frequent. Symptomatic lesions are treated analogously to other hyaline cartilage bearing joints and can be treated arthroscopically in the vast majority of cases. The therapeutic options can be subdivided into resection, stimulation and transplantation of the defect cartilage. There are only a few reports about outcome after cartilage restoration surgery in the literature, and microfracturing is the surgical technique that has been most investigated.

Localized cartilage defects at the hip are mainly caused by pre-arthritic deformities, particularly by cam-type femoroacetabular impingement (FAI). Timely elimination of symptomatic deformities can prevent further progression such as cartilage defects. As the defects mostly occur in the anterolateral part of the acetabulum, they can be easily treated either by open surgery or by arthroscopy. To date the most effective methods of treatment are bone marrow stimulation, with or without a covering of biomaterials, and autologous chondrocyte transplantation. In selected cases, readaptation of the damaged cartilage can be attempted by biological procedures. In the present article, the findings reported in current studies on these procedures are summarized and discussed in detail. An outlook is given regarding possible future treatment concepts.

Background: Therapeutic strategies for cartilage repair of the talus are varied. With the use of biologic scaffolds and biologic agents new cell-based therapies have become the focus of attention., Objectives: Ankle cartilage repair techniques are presented and assessed by current data. In addition, technical notes for each technique are given., Material and Methods: Currently, the following established ankle cartilage repair procedures exist: microfracturing, AMIC (autologous matrix-induced chondrogenesis), OCT (osteochondral transplantation, mosaicplasty), allograft transplantation., Discussion: The success of each repair technique is dependent on the proper indication, addressing of co-morbidities like axis deviation or ligament instabilities, the experience of the surgeon and the appropriate rehabilitation. Mid- and long-term results are often good or excellent. Best results are seen in isolated cartilage defects without co-morbidities in patients younger than 40 years of age and non-smokers with normal BMI and early intervention. New cell-based therapies utilize scaffolds and biologic agents. They offer promising perspectives, although current data is inconsistent.

Background: The metatarsal bones of the foot are particularly susceptible to stress fracture owing to the high strains they experience during the stance phase of running. Shoe cushioning and stride length reduction represent two potential interventions to decrease metatarsal strain and thus stress fracture risk., Methods: Fourteen male recreational runners ran overground at a 5-km pace while motion capture and plantar pressure data were collected during four experimental conditions: traditional shoe at preferred and 90% preferred stride length, and minimalist shoe at preferred and 90% preferred stride length. Combined musculoskeletal - finite element modeling based on motion analysis and computed tomography data were used to quantify metatarsal strains and the probability of failure was determined using stress-life predictions., Findings: No significant interactions between footwear and stride length were observed. Running in minimalist shoes increased strains for all metatarsals by 28.7% (SD 6.4%; p<0.001) and probability of failure for metatarsals 2-4 by 17.3% (SD 14.3%; p≤0.005). Running at 90% preferred stride length decreased strains for metatarsal 4 by 4.2% (SD 2.0%; p≤0.007), and no differences in probability of failure were observed., Interpretations: Significant increases in metatarsal strains and the probability of failure were observed for recreational runners acutely transitioning to minimalist shoes. Running with a 10% reduction in stride length did not appear to be a beneficial technique for reducing the risk of metatarsal stress fracture, however the increased number of loading cycles for a given distance was not detrimental either., (Copyright © 2017 Elsevier Ltd. All rights reserved.)