Do running and fatigued running relate to tibial stress fractures?

Tibial stress fractures are common in runners. However, it is unclear what factors are associated with tibial stress fractures. This study aimed to investigate 1) magnitudes of bone contact forces occurring while running 2) whether or not repeated application of running loads is sufficient to explain tibial stress fractures and 3) whether or not muscle fatigue alters the potential of tibial stress fractures. Tibial stress fractures were predicted through an estimation of the minimum number of cycles to failure (Nfail) using an integrated experimental and mathematical modeling approach. Short running trials within a speed range of 3.5-4 m/s of ten male runners were evaluated with a coupled force plate and 3 dimensional motion analysis system. The collected data were used to estimate joint reaction forces (JRF) and joint moments. Using these JRF and muscle forces predicted from optimization, 2-D bone contact forces at the distal end of the tibia were determined. Next, tibial stresses were estimated by applying these bone contact forces to a tibial model, which were then used to predict the Nfail. All procedures were repeated after plantarflexors fatigued from prolonged running. This study found that peaks of compressive and posterior shear forces occurred during mid stance, and these peaks equaled 8.91 ± 1.14 BW and -0.53 ± 0.16 BW, respectively. These bone contact forces led to a backward bending of the tibia during most of the stance phase and resulted in the maximum stresses of - 43.4 ± 10.3 MPa on the posterior face of the tibia. These maximum stresses predicted the group mean of Nfail as being 5.28*10⁶ cycles. However, 2.5% to 56% of population of runners have a chance of getting tibial stress fractures within 1 million cycles of a repeated foot impact. Within the context of muscle force and stress estimation procedures used in this study, Nfail appeared to increase after fatigue, not decrease as we hypothesized

FOOT STRIKE POSTURE AND LOWER-LIMB DYNAMICS DURING SIDESTEPPING AMONG ELITE FEMALE ATHLETES: IMPLICATIONS FOR ACL INJURY RISK

The purpose of this study was to compare the lower-limb dynamics between fore-foot (FF) and rear-foot (RF) strike patterns during unplanned sidestepping. Three-dimensional (3D) motion capture data were collected from 16 elite female hockey players. Ankle, knee, and hip: angle at initial foot contact (IC), range of motion (ROM), peak moment, and negative peak net joint power during weight acceptance phase were compared between athletes using natural RF and FF strike techniques. Results showed ankle and hip angle at IC, ankle ROM, peak ankle and knee extension moments, peak knee valgus moments, and ankle and knee negative peak net power between RF and FF strike patterns were significantly different (a < 0.05). These findings show foot strike technique during unplanned sidestepping can effect athlete lower-limb dynamics, where RF strike athletes may be at higher risk of ACL injury

Increased density and periosteal expansion of the tibia in young adult men following short-term arduous training

Purpose: Few human studies have reported early structural adaptations of bone to weight-bearing exercise, which provide a greater contribution to improved bone strength than increased density. This prospective study examined site- and regional-specific adaptations of the tibia during arduous training in a cohort of male military (infantry) recruits to better understand how bone responds in vivo to mechanical loading. Methods: Tibial bone density and geometry were measured in 90 British Army male recruits (ages 21 + 3 y, height 1.78 ± 0.06 m, body mass 73.9 + 9.8 kg) in weeks 1 (Baseline) and 10 of initial military training. Scans were performed at the 4%, 14%, 38% and 66% sites, measured from the distal end plate, using pQCT (XCT2000L, Stratec Pforzheim, Germany). Customised software (BAMPack, L-3 ATI) was used to examine whole bone cross-section and regional sectors. T-tests determined significant differences between time points (P<0.05). Results: Bone density of trabecular and cortical compartments increased significantly at all measured sites. Bone geometry (cortical area and thickness) and bone strength (i, MMi and BSI) at the diaphyseal sites (38 and 66%) were also significantly higher in week 10. Regional changes in density and geometry were largely observed in the anterior, medial-anterior and anterior-posterior sectors. Calf muscle density and area (66% site) increased significantly at week 10 (P<0.01). Conclusions: In vivo mechanical loading improves bone strength of the human tibia by increased density and periosteal expansion, which varies by site and region of the bone. These changes may occur in response to the nature and distribution of forces originating from bending, torsional and shear stresses of military training. These improvements are observed early in training when the osteogenic stimulus is sufficient, which may be close to the fracture threshold in some individuals

Heel effects on joint contact force components in the equine digit : a sensitivity analysis

Reasons for performing study: Whereas the effect of heel configuration on the tension of the suspensory apparatus is well documented in the literature, there are few reports of joint contact force components in the equine distal forelimb. Objectives: To improve understanding of the effect of heel configuration on equine digit joint loading, a sensitivity analysis was performed to compare the effect of a raised heel on joint contact force components in the coffin and fetlock joints during the stance phase of the trot. Materials and methods: FourWarmblood horses were used. An inverse dynamic analysis was carried out using kinematic and kinetic data. Taking into account the tendon wrapping forces (WF) around the sesamoid bones in the calculations, the joint contact forces (CF) were estimated for the coffin and fetlock joints during the trot stance phase (4 m/s). To test the sensitivity of the results to heel configuration changes, calculations were performed repeatedly for different heel configurations (raised by 0, 6 and 12°). A one-way ANOVA with repeated measures was used to test the effect of heel configuration (at the 3 levels) (a = 0.05; P<0.05; post hoc testing: Bonferroni). Results: For heel configurations raised from 0–12°: whereas the tension of the deep digital flexor tendon decreased and the tension of the superficial digital flexor tendon increased, for the coffin joint the peakWF(1.4 +- 0.25 bwt; 1.2 +- 0.2 bwt; 0.95 +- 0.1 bwt) and the peak CF (2.45 +- 0.25 bwt; 2.2 +- 0.2 bwt; 2 +- 0.1 bwt) decreased significantly (P<0.05). For the fetlock joint, the peak WF (3.8 +- 0.7 bwt; 4.1 +- 0.3 bwt; 4.4 0.25 bwt) and the peak CF (4.35 +- 0.7 bwt; 4.7 +- 0.35 bwt; 5 +- 0.3 bwt) increased, but not significantly. Conclusion: This analysis suggests that the coffin joint loading and fetlock joint loading are strongly connected. The heel configuration may influence both coffin joint and fetlock joint contact force components

A New 3D Mechanism for Modeling the Passive Motion of the Tibia–Fibula–Ankle Complex

A great number of kinematic, kinetostatic and dynamic models of human diarthrodial joints, such as the hip, the knee and the ankle, have been presented in the literature. On the contrary, comprehensive models of the lower limb are lacking and often oversimplify its anatomical structures by considering only 2D motion. This paper will focus on the 3D kinematic model of the articulation that involves four bones: the tibia, fibula, talus and calcaneus. In particular, a new spatial equivalent mechanism with one degree of freedom is proposed for the passive motion simulation of this anatomical complex. The geometry of the mechanism is based on the main anatomical structures, namely the talus, the tibia and the fibula bones at their interface, on the main ligaments of the ankle joint, and on the interosseus membrane of the leg. An iterative refinement process is presented, that provides the optimal geometry of the mechanism which allows the best fitting of simulation versus measurement data. Simulation results show the efficiency of the proposed mechanism that is believed to play an important role for future developments of models of the whole human lower limb