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Purpose of review This review aims to provide concise updated bone stress injury management based on anatomical location and severity, while also discussing adjunct treatment options. Recent Findings Emergence of newer adjunct treatments includes orthobiologics, blood flow restriction, and extracorporeal shockwave therapy to aid bone healing. Summary Bone stress injuries of the lower extremities can lead to time away from sport and often represent a larger health concern. Patient presentations can often be vague, so a high clinical suspicion is necessary. While each treatment plan should be individualized, the overall management plan can be guided based on stress fracture severity and grading systems as well as the anatomic location. Rehabilitation and return to play protocols help minimize loss of strength and conditioning to help ensure a speedy safe recovery. In addition, adjunctive treatment options are being considered to aid recovery and minimize time away from sport.

For decades researchers reported that pre-menopausal women who engage in extensive endurance exercise and have menstrual dysfunction can develop low bone mineral density (BMD) or osteoporosis. More recently, low energy availability has been recognized as the initiating factor for low BMD in these women. Furthermore, the relationship between low energy availability and poor skeletal health is not exclusive to women engaging in endurance exercise. Rather, both males and females commonly experience endocrine dysfunction resulting from low energy availability and high exercise levels that degrades skeletal health. Consequences to skeletal health can range from short-term changes in bone metabolism and increased risk of bone stress injuries to long-term consequences of low BMD, such as osteoporosis and related fragility fractures. The degree to which low energy availability degrades skeletal health may be dependent on the length and extent of the energy deficit. However, the complex relationships between under-fueling, short- and long-term skeletal consequences and the factors that mediate these relationships are not well described. In this review, we discuss the consequences of low energy availability on sex hormones and skeletal health in two highly-active populations—athletes and military trainees—and provide a summary of existing knowledge gaps for future study.

Trabecular microarchitecture contributes to bone strength, but its role in bone stress injury (BSI) risk in young healthy adults is unclear. Tibial volumetric BMD (vBMD), geometry, and microarchitecture, whole-body areal BMD, lean and fat mass, biochemical markers of bone metabolism, aerobic fitness, and muscle strength and power were measured in 201 British Army male infantry recruits (age 20.7 [4.3] years, BMI 24.0 ± 2.7 kg·m2) in week one of basic training. Tibial scans were performed at the ultra-distal site, 22.5 mm from the distal endplate of the non-dominant leg using High Resolution Peripheral Quantitative Computed Tomography (XtremeCT, Scanco Medical AG, Switzerland). Binary logistic regression analysis was performed to identify associations with lower body BSI confirmed by MRI. 20 recruits (10.0%) were diagnosed with a lower body BSI. Pre-injured participants had lower cortical area, stiffness and estimated failure load (p = 0.029, 0.012 and 0.011 respectively) but tibial vBMD, geometry, and microarchitecture were not associated with BSI incidence when controlling for age, total body mass, lean body mass, height, total 25(OH)D, 2.4-km run time, peak power output and maximum dynamic lift strength. Infantry Regiment (OR 9.3 [95%CI, 2.6, 33.4]) Parachute versus Line Infantry, (p ≤ 0.001) and 2.4-km best effort run time (1.06 [95%CI, 1.02, 1.10], p < 0.033) were significant predictors. Intrinsic risk factors, including ultradistal tibial density, geometry, and microarchitecture, were not associated with lower body BSI during arduous infantry training. The ninefold increased risk of BSI in the Parachute Regiment compared with Line Infantry suggests that injury propensity is primarily a function of training load and risk factors are population-specific.

The aims were to (1) prospectively observe the incidence of bone marrow oedema in asymptomatic adult male domestic professional cricketers during a season and evaluate its relationship to the development of lumbar bone stress injury and (2) further understand the practicalities of implementing a Magnetic Resonance Imaging-based screening program to prevent lumbar bone stress injury in New Zealand cricket. Prospective observational cohort. Adult male pace bowlers received 6-weekly pre-planned Magnetic Resonance Imaging scans over a single season to determine the presence and intensity of bone marrow oedema in the posterior vertebral arches of the lumbar spine. The participants bowling volume and back pain levels were monitored prospectively. 22 participants (mean age 25.3 years (range 20–32 years)) completed all 4 scans. Ten participants had a prior history of lumbar bone stress injury. Ten participants (45 %, 95 % confidence interval 24-68 %) had bone marrow oedema evident on at least one scan, with 9 (41 %) participants recording a bone marrow oedema intensity ≥ 2 and 5 (23 %) participants demonstrated an intensity ≥ 3. During the study one participant was diagnosed with a lumbar bone stress reaction. No participants developed a lumbar bone stress fracture. Due to the lower incidence of lumbar bone stress injuries in adult bowlers coupled with uncertainty over appropriate threshold values for bone marrow oedema intensity, implementation of a resource intense screening program aimed at identifying adult domestic cricketers at risk of developing a lumbar bone stress injury is not currently supported.

Boundary conditions (BCs) are often simplified in experimental and numerical models simulating distal radius fractures and their treatments. The aim of this study was to investigate the effects of simplified BCs at the radiocarpal joint: (1) on the stress distribution in the intact distal radius, and (2) on the loading of a volar locking plate (VLP) used for distal radius fracture treatment. Finite element models of the distal radius with contact between carpals and cartilage were created as reference models for an intact bone and a fractured bone with VLP treatment. Four models with simplified BCs were compared to these reference models: One with embedding material instead of carpals, one with carpals tied to the radius; each loaded either uniaxially or with statically equivalent loading to the reference model. Differences in distal bone stress distributions and mechanical parameters of the VLP (fracture gap movement, plate peak stresses, distal screw loads) were generally largest for the uniaxially loaded, embedded model (up to 250 % in individual screw loads) and smallest for the model with tied carpals and statically equivalent loads (<25 % for all parameters). Differences were greatly reduced if statically equivalent loads were applied, but subchondral stress peaks were absent without carpals. In conclusion, implementing realistic resultant forces and moments is more important than the exact articular load distribution, but carpal bones should be included if subchondral bone stresses are analyzed. In this case, a tie constraint may replace articular contact modelling with acceptable accuracy if statically equivalent loading is applied.

Background Relative energy deficiency in sport (REDs) is associated with impaired performance and compromised bone health in elite athletes. While reduced bone mineral density (BMD) and increased risk for bone stress injuries are well documented, the underlying metabolic mechanisms remain poorly understood. This study investigates the bone metabolism in athletes with REDs and its impact on BMD and bone microstructure. Methods We retrospectively analysed data from 82 elite athletes (30.5% females, age 23.4 ± 7.6 years) who presented to our outpatient clinic. The diagnosis of REDs was made according to the International Olympic Committee REDs Clinical Assessment Tool Version 2 (IOC REDs CAT2), and athletes were categorised into strength‐based vs. endurance‐based sports. Laboratory assessment of calcium and bone metabolism included bone turnover markers such as osteocalcin, procollagen type 1 N‐terminal propeptide (P1NP) and urinary deoxypyridinoline (DPD). Areal BMD with corresponding Z‐score was measured by dual‐energy X‐ray absorptiometry (DXA) at the lumbar spine and hip. Volumetric BMD and bone microstructure were assessed by high‐resolution peripheral quantitative computed tomography (HR‐pQCT) at the distal radius and tibia. Results REDs was diagnosed in 24% of the athletes, and stress fractures were observed more frequently in athletes with REDs compared with those without REDs (70% vs. 25%, p < 0.001). Athletes with REDs showed significantly lower haemoglobin and haematocrit levels (p < 0.05). Osteocalcin and P1NP were reduced in REDs compared with athletes of strength‐based disciplines (p < 0.01), while urinary DPD/creatinine and calcium excretion were elevated (p < 0.05), indicating suppressed bone formation and increased bone resorption, respectively. Athletes with REDs exhibited significantly reduced Z‐scores at the lumbar spine and hip compared with strength and endurance athletes without REDs (p < 0.05). HR‐pQCT revealed significantly lower bone volume to tissue volume and trabecular BMD at the distal radius and tibia, with more pronounced effects at the load‐bearing tibia (p < 0.01). Similarly, trabecular number and cortical thickness were reduced in REDs, while no differences were observed in trabecular thickness. Conclusion Athletes with REDs are characterised by a catabolic bone metabolism, marked by reduced bone formation alongside increased bone resorption. The resulting metabolic imbalance compromises skeletal adaptations to mechanical loading and contributes to decreased BMD and deteriorated bone microstructure, particularly at weight‐bearing sites. These findings underscore the shared key features of REDs and cachexia and highlight the need for early identification and management of REDs to prevent bone stress injuries and preserve athletic performance. Monitoring bone metabolism may support targeted treatment and improve outcomes in affected athletes.

The etiology of subchondral bone cysts (SBCs) is not fully understood. Mechanical trauma and fluid pressure are two mechanisms believed to cause their formation and growth. The equine stifle joint provides a natural animal model for studying SBCs. Computed tomography images of an extended yearling cadaveric stifle joint were segmented using ScanIP to isolate bones and relevant soft tissues. Three model geometries were created to simulate cyst sizes of approximately 0.03 cm3 (C1), 0.5 cm3 (C2), and 1 cm3 (C3). A uniform pressure resulting in 3000 N force was applied at the proximal end of the femur. Two types of simulations, filled-cyst and empty-cysts with uniform pressure loads, were used to simulate fluid pressurization. Our models suggest that shear stresses are likely the cause of failure for the subchondral bone and not pressurized fluid from the joint. Bone stresses did not begin to increase until cyst pressures were greater than 3 MPa. For all cyst sizes, fluid pressure must rise above what is likely to occur in vivo in order to increase bone shear stress, shown to be most critical. Synovial fluid pressure acts upon a porous trabecular bone network, soft tissue, and marrow, so the continuum nature of our model likely overestimates the predicted effects of fluid pressures.

Introduction Proximal humerus fractures are usually treated with locking plates, which could present recurrence, screw penetration, joint varization. The push–pull principle was introduced to prevent these risks and showed promising results; a dedicated design was then developed and this feasibility study aims to compare the biomechanical performances of such dedicated push–pull plate with the traditional locking plate using finite elements. Materials and methods The humerus geometry was obtained from Sawbone CT-scans; the geometries of a traditional locking plate and of the dedicated push–pull one were used. A fracture was added below the humeral head and the plates were virtually implanted. The wire pulling mechanism was simulated connecting the plate to the humeral head apex, considering two levels of tension. Three testing set-ups (axial, torsion and compression bending) were simulated. Stress distributions on bone, plate and screws were measured. Results Stress distribution on the distal humerus was similar for both plates. Stress distribution on the proximal humerus was more homogeneous for the push–pull model, showing less unloaded sections (up to 78%). The different levels of tension applied to the wire returned slight differences in terms of stress values, but the comparison with the traditional approach gave similar outcomes. Conclusions More homogeneous stress distribution is found with the push–pull plate in all three testing set-ups, showing lower unloaded areas (and thus lower stress-shielding) compared to the traditional plate; the screws implemented returned to be all loaded in at least one of the set-ups, thus showing that they all contribute to plate stability.

This animal study compared the healing performance of a novel implant design characterized by a shift in thread geometry and core diameter with two different surfaces with that of an apically tapered implant. Test Bioactive (n = 9), Test Porous (n = 7) and Control (n = 8) implants were placed in the mandibles of minipigs. Following healing, bone samples were harvested for determining bone-to-implant contact (BIC) and marginal bone loss (MBL). Comparative statistics were based on Levene’s test, Shapiro–Wilk tests, the Kruskal–Wallis test and Wilcoxon tests with Holm correction (α = 0.05). The mean undersizing of the osteotomy was 0.15 mm for Control, while in the test groups 0.33 mm and 0.34 mm were calculated. Insertion torques ranged from 61.5 Ncm (Control) to 76.1 Ncm (Test Bioactive). Maximum BIC was seen in Test Porous with 55.83%, while Test Bioactive showed only 48.11%. MBL was 4.1 mm in Test Bioactive, while Test Porous and Control exhibited 2.8 mm. No significant differences between the implant groups were observed (p > 0.05). Despite greater undersizing, the novel implant type performed comparably to the established Control implants. The rougher surface of the bioactive implants increased the insertion torque and led to more MBL.

Background Screw loosening is a frequently reported complication following pedicle screw fixation, resulting in various adverse outcomes. The primary trigger for screw loosening is biomechanical deterioration. Iatrogenic injury to the pedicle is a commonly observed scenario. This alteration can lead to an increased risk of pedicle screw loosening. Bilateral pedicle screws distribute load during the patient's daily activities and can be regarded as an integrated structure from a biomechanical perspective. Consequently, biomechanical interactions are prevalent between the two sides of the pedicle screws. This study aimed to determine whether unilateral pedicle injury influences contralateral screw loosening by deteriorating the local biomechanical environment. Methods The numerical model of the L5 vertebral body, developed in our previous studies, was employed in this investigation. Bilateral pedicle screws were inserted following the standard trajectory. Simulations of both half and complete ventral and dorsal side pedicle injuries were performed on the right‐side pedicle. Stress and strain values of the screw trajectory, along with screw displacement values on the contralateral side, were recorded to assess the potential risk of screw loosening. Results Compared to the model without pedicle injury, models with pedicle injuries exhibited higher interfacial stress and strain, as well as greater screw displacement. This effect was particularly pronounced when the pedicle on the side of torque restriction (e.g., caudal side pedicle injury under the flexion loading condition) was considered. Furthermore, unilateral iatrogenic injury to the pedicle can trigger multi‐degree‐of‐freedom coupled motion under a single‐direction torque. Conclusions Single‐side iatrogenic pedicle injury can lead to multi‐degree‐of‐freedom coupled motion of the screw‐fixed vertebral body, and biomechanical deterioration of the contralateral screw trajectory, thereby increasing the risk of contralateral pedicle screw loosening.