Pieter Spaepen

Classification of Forefoot Plantar Pressure Distribution in Persons with Diabetes: A Novel Perspective for the Mechanical Management of Diabetic Foot?

Background The aim of this study was to identify groups of subjects with similar patterns of forefoot loading and verify if specific groups of patients with diabetes could be isolated from non-diabetics. Methodology/Principal Findings Ninety-seven patients with diabetes and 33 control participants between 45 and 70 years were prospectively recruited in two Belgian Diabetic Foot Clinics. Barefoot plantar pressure measurements were recorded and subsequently analysed using a semi-automatic total mapping technique. Kmeans cluster analysis was applied on relative regional impulses of six forefoot segments in order to pursue a classification for the control group separately, the diabetic group separately and both groups together. Cluster analysis led to identification of three distinct groups when considering only the control group. For the diabetic group, and the computation considering both groups together, four distinct groups were isolated. Compared to the cluster analysis of the control group an additional forefoot loading pattern was identified. This group comprised diabetic feet only. The relevance of the reported clusters was supported by ANOVA statistics indicating significant differences between different regions of interest and different clusters. Conclusion/s Significance There seems to emerge a new era in diabetic foot medicine which embraces the classification of diabetic patients according to their biomechanical profile. Classification of the plantar pressure distribution has the potential to provide a means to determine mechanical interventions for the prevention and/or treatment of the diabetic foot.

Repeatability of a 3D multi-segment foot model protocol in presence of foot deformities

Repeatability studies on 3D multi-segment foot models (3DMFMs) have mainly considered healthy participants which contrasts with the widespread application of these models to evaluate foot pathologies. The current study aimed at establishing the repeatability of the 3DMFM described by Leardini et al. in presence of foot deformities. Foot kinematics of eight adult participants were analyzed using a repeated-measures design including two therapists with different levels of experience. The inter-trial variability was higher compared to the kinematics of healthy subjects. Consideration of relative angles resulted in the lowest inter-session variability. The absolute 3D rotations between the Sha-Cal and Cal-Met seem to have the lowest variability in both therapists. A general trend towards higher σ(sess)/σ(trial) ratios was observed when the midfoot was involved. The current study indicates that not only relative 3D rotations and planar angles can be measured consistently in patients, also a number of absolute parameters can be consistently measured serving as basis for the decision making process.

Transmission of Whole-body Vibration and Its Effect on Muscle Activation

Abstract Tankisheva E, Jonkers I, Boonen S, Delecluse C, van Lenthe GH, Druyts HLJ, Spaepen P, and Verschueren SMP. Transmission of whole-body vibration and its effect on muscle activation. J Strength Cond Res 27(9): 2533–2541, 2013—The aim of current study was to measure the transmission of whole-body vibration through the entire body and to relate this to body posture and induced muscular activation. Eight clinically healthy subjects performed 3 static body postures—high squat (135°), deep squat (110°), and erect stance, whereas vibration transmission was assessed over a wide range of accelerations (from 0.33 to 7.98 g) and frequencies (from 30 to 50 Hz). To assess the vibration transmission, 9 triaxial accelerometers were attached from the ankle up to the head and the root mean square of acceleration signal of each site-specific body point was calculated. Additionally, muscle activity from 7 lower limb muscles was recorded. The results showed a significant attenuation of the platform accelerations transmitted from the feet to the head. Compared with erect stance, knee bent posture significantly diminished vibration transmission at the hip, spine, and the head (p < 0.05). Vibration transmission to the spine was significantly lower in deep vs. high squat (p < 0.05), suggesting that further knee bending may reduce the risk of overloading the spine. Vibration increased the muscle activity in most leg and hip muscles during both squat postures, although, on average, no clear dose–response relationship between the acceleration and/or frequency and muscle response was found. The muscular activation of vastus medialis and rectus femoris showed clear negative correlation to the vibration transmission at the sternum. The specific vibration parameters used in the present study can be considered as safe and suitable for a training program. Moreover, the present results contribute to optimize the most advantageous whole-body vibration protocol and to determine the beneficial effects on muscle and bone.

Experimental Validation of Input Torque Balancing Applied to Weaving Machinery

This paper considers a class of high-speed airjet weaving machines that is characterized by excessive harness frame vibration, resulting in premature failure. This problem is tackled through addition of an auxiliary, input torque balancing mechanism: A centrifugal pendulum, of which the pendulum motion is imposed by an internal cam. While earlier work by the same authors focused on the design, optimization, and robustness analysis of this mechanism, the current paper presents experimental results. The considered setup is an industrial weaving machine a blanc equipped with a centrifugal pendulum prototype. Below a critical speed, the prototype functions as predicted and significantly improves the machine dynamics: The drive speed fluctuation is reduced by a factor of 2.5 and the vibration level of the harness frames is halved. Above the critical speed, however, torsional resonance dominates the machine dynamics. This phenomenon is verified on simulation by extending the rigid-body setup model, on which the centrifugal pendulum design is based, with a torsional degree of freedom.

Trabecular Bone Adaptation to Low-Magnitude High-Frequency Loading in Microgravity

Exposure to microgravity causes loss of lower body bone mass in some astronauts. Low-magnitude high-frequency loading can stimulate bone formation on earth. Here we hypothesized that low-magnitude high-frequency loading will also stimulate bone formation under microgravity conditions. Two groups of six bovine cancellous bone explants were cultured at microgravity on a Russian Foton-M3 spacecraft and were either loaded dynamically using a sinusoidal curve or experienced only a static load. Comparable reference groups were investigated at normal gravity. Bone structure was assessed by histology, and mechanical competence was quantified using μCT and FE modelling; bone remodelling was assessed by fluorescent labelling and secreted bone turnover markers. Statistical analyses on morphometric parameters and apparent stiffness did not reveal significant differences between the treatment groups. The release of bone formation marker from the groups cultured at normal gravity increased significantly from the first to the second week of the experiment by 90.4% and 82.5% in response to static and dynamic loading, respectively. Bone resorption markers decreased significantly for the groups cultured at microgravity by 7.5% and 8.0% in response to static and dynamic loading, respectively. We found low strain magnitudes to drive bone turnover when applied at high frequency, and this to be valid at normal as well as at microgravity. In conclusion, we found the effect of mechanical loading on trabecular bone to be regulated mainly by an increase of bone formation at normal gravity and by a decrease in bone resorption at microgravity. Additional studies with extended experimental time and increased samples number appear necessary for a further understanding of the anabolic potential of dynamic loading on bone quality and mechanical competence.

TRABECULAR BONE ADAPTATION TO LOW-MAGNITUDE HIGH-FREQUENCY LOADING AT MICRO-GRAVITY

Exposure to microgravity causes loss of lower body bone mass in some astronauts. Low-magnitude high-frequency loading can stimulate bone formation on earth. Here we hypothesized that low-magnitude high-frequency loading will also stimulate bone formation under microgravity conditions. Two groups of six bovine cancellous bone explants were cultured at microgravity on a Russian Foton-M3 spacecraft and were either loaded dynamically using a sinusoidal curve or experienced only a static load. Comparable reference groups were investigated at normal gravity. Bone structure was assessed by histology, and mechanical competence was quantified using mCT and FE modelling; bone remodelling was assessed by fluorescent labelling and secreted bone turnover markers. Statistical analyses on morphometric parameters and apparent stiffness did not reveal significant differences between the treatment groups. The release of bone formation marker from the groups cultured at normal gravity increased significantly from the first to the second week of the experiment by 90.4% and 82.5% in response to static and dynamic loading, respectively. Bone resorption markers decreased significantly for the groups cultured at microgravity by 7.5% and 8.0% in response to static and dynamic loading, respectively. We found low strain magnitudes to drive bone turnover when applied at high frequency, and this to be valid at normal as well as at microgravity. In conclusion, we found the effect of mechanical loading on trabecular bone to be regulated mainly by an increase of bone formation at normal gravity and by a decrease in bone resorption at microgravity. Additional studies with extended experimental time and increased samples number appear necessary for a further understanding of the anabolic potential of dynamic loading on bone quality and mechanical competence. Citation: Torcasio A, Jahn K, Van Guyse M, Spaepen P, Tami AE, et al. (2014) Trabecular Bone Adaptation to Low-Magnitude High-Frequency Loading in Microgravity. PLoS ONE 9(5): e93527. doi:10.1371/journal.pone.0093527 Editor: Ali Al-Ahmad, University Hospital of the Albert-Ludwigs-University Freiburg, Germany Received May 22, 2013; Accepted March 7, 2014; Published May 2, 2014 Copyright: 2014 Torcasio et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was financially supported by grant C90346 (Belgium PRODEX-9 project) and the ESA MAP grant #AO99-122. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: harry.vanlenthe@mech.kuleuven.be

Effect of external loading on in vitro measured muscle induced calcanear and talar motion

Several foot deformities (e.g. pes planus, pes cavus) result from muscular force imbalance across the joints of the ankle and foot. The use of in vitro measurements is required to explore the causal relation between muscle forces, individual foot bone movement and resulting foot deformities. This study quantified the effect of muscle action of the pretibial muscle groups, Mm. peronei as well as the Gastro-soleus on the three dimensional rotation of calcaneus and talus using in vitro measurements with a gait simulator consisting of pneumatic actuators. Furthermore, we tested the effect of altered load bearing conditions of the foot on the observed relations.