International Foot and Ankle Biomechanics Community (i-FAB): past, present and beyond

The International Foot and Ankle Biomechanics Community (i-FAB) is an international collaborative activity which will have an important impact on the foot and ankle biomechanics community. It was launched on July 2nd 2007 at the foot and ankle session of the International Society of Biomechanics (ISB) meeting in Taipei, Taiwan. i-FAB is driven by the desire to improve our understanding of foot and ankle biomechanics as it applies to health, disease, and the design,development and evaluation of foot and ankle surgery, and interventions such as footwear, insoles and surfaces

Pedobarographic and kinematic analysis in the functional evaluation of two post-operative forefoot offloading shoes

Background: Forefoot offloading shoes are special orthopaedic footwear designed to protect and unload the injured part of the foot after surgery and for conservative treatments. The offloading action is often achieved by transferring plantar load to the rearfoot via rocker shoes with reduced contact area between shoe and ground. While these shoes are intended to be worn only for short periods, a compromise must be found between functionality and the risk of alterations in gait patterns at the lower limb joints. In this study, the pedobarographic, kinematic and kinetic effects of a traditional half-shoe and a double-rocker full-outsole shoe were compared to those of a comfortable shoe (control). Methods: Ten healthy female participants (28.2±10.0 years) were asked to walk in three different footwear conditions for the left/right foot: control/half-shoe, control/full-outsole, and control/control. Full gait analysis was obtained in three walking trials for each participant in each condition. Simultaneously a sensor insole system recorded plantar pressure in different foot regions. Normalized root-mean-square error, coefficient of determination, and frame-by-frame statistical analysis were used to assess differences in time-histories of kinematic and kinetic parameters between shoes. Results: The half -shoe group showed the slowest walking speed and the shortest stride length. Forefoot plantar load was significantly reduced in the half-shoe (maximum force as % of Body Weight: half-shoe=62.1; full-outsole=86.9; control=93.5; p<0.001). At the rearfoot, mean pressure was the highest in the full-outsole shoe. At the ankle, sagittal-plane kinematics in the full-outsole shoe had a pattern more similar to control. Conclusions: The half-shoe appears significantly more effective in reducing plantar load at the forefoot than a double-rocker full-outsole shoe, which is designed to reduce forefoot loading by using an insole with a thicker profile anteriorly as to maintain the foot in slight dorsiflexion. However, the half-shoe is also associated with altered gait spatio-temporal parameters, more kinematic modifications at the proximal lower limb joints and reduced propulsion in late stance

Functional Evaluation of a Shock Absorbing Insole During Military Training in a Group of Soldiers: A Pilot Study

Abstract Objective Soldiers' lower limbs and feet are frequently affected by overload- and overuse-related injuries. In order to prevent or limit the incidence of these injuries, the use of foot orthoses is often recommended. The aim of this study is to assess the effects of shock-absorbing insoles on in-shoe plantar pressure magnitude and distribution in a group of professional infantry soldiers wearing military boots during standard indoor military training. Methods Twenty male professional soldiers of the Italian Army (age 35.1 ± 6.1 years; BMI 25.2 ± 2.3 kg/m2) were recruited for this study. Each subject underwent clinical examination to assess possible overuse-related diseases of the lower limb and trunk. Subjects with altered foot morphology according to the Foot Posture Index (FPI) were excluded from this study. Twelve subjects were considered eligible and therefore underwent an indoor training routine comprised of marching, running, jumping inside parallel bars and jumping from different heights. Soldiers repeated the training session twice wearing standard military boots along with two types of insoles: the standard prefabricated insole within the boots (STI), and a special shock-absorbing insole (SAI) featuring an elastic medial arch support. A 99-capacitive sensor insole system was used to record plantar pressure distribution in both feet. Analysis of in-shoe pressure parameters at rearfoot, midfoot and forefoot and in the total foot was performed via a custom-software application developed in MATLAB. Perceived foot comfort (VAS 0–15) was also assessed. Results Pressure parameters recorded during walking and running were considered suitable for statistical analysis. In the whole foot region, pressure parameters were 18–22% lower in military boots fitted with the SAI during walking and 14–18% lower during running. SAI resulted in better comfort (+25%) with respect to the prefabricated boot orthotics (median comfort: SAI = 15/15; STI = 12/15; p = 0.0039) both during walking and running. Conclusions Shock-absorbing insoles can be an effective solution when fitted inside military boots. The present functional evaluation shows that wearing a prefabricated shock-absorbing insole can provide a significant amelioration of perceived foot comfort and plantar pressure parameters. Further studies are now needed with a larger population and more demanding exercises

In vivo kinematics of knee replacement during daily living activities: Condylar and post-cam contact assessment by three-dimensional fluoroscopy and finite element analyses

In total knee replacement, the investigation on the exact contact patterns at the post-cam in implanted patients from real in vivo data during daily living activities is fundamental for validating implant design concepts and assessing relevant performances. This study is aimed at verifying the restoration of natural tibio-femoral condylar kinematics by investigating the post-cam engagement at different motor tasks. An innovative validated technique, combining three-dimensional fluoroscopic and finite element analyses, was applied to measure joint kinematics during daily living activities in 15 patients implanted with guided motion posterior-stabilized total knee replacement. Motion results showed physiological antero-posterior translations of the tibio-femoral condyles for every motor task. However, high variability was observed in the position of the calculated pivot point among different patients and different motor tasks, as well as in the range of post-cam engagement. Physiological tibio-femoral joint rotations and contacts at the condyles were found restored in the present knee replacement. Articular contact patterns experienced at the post-cam were found compatible with this original prosthesis design. The present study reports replaced knee kinematics also in terms of articular surface contacts, both at the condyles and, for the first time, at the post-cam

Validation of the angular measurements of a new inertial-measurement-unit based rehabilitation system: comparison with state-of-the-art gait analysis

Background: Several rehabilitation systems based on inertial measurement units (IMU) are entering the market for the control of exercises and to measure performance progression, particularly for recovery after lower limb orthopaedic treatments. IMU are easy to wear also by the patient alone, but the extent to which IMU's malpositioning in routine use can affect the accuracy of the measurements is not known. A new such system (Riablo™, CoRehab, Trento, Italy), using audio-visual biofeedback based on videogames, was assessed against state-of-the-art gait analysis as the gold standard.Methods. The sensitivity of the system to errors in the IMU's position and orientation was measured in 5 healthy subjects performing two hip joint motion exercises. Root mean square deviation was used to assess differences in the system's kinematic output between the erroneous and correct IMU position and orientation.In order to estimate the system's accuracy, thorax and knee joint motion of 17 healthy subjects were tracked during the execution of standard rehabilitation tasks and compared with the corresponding measurements obtained with an established gait protocol using stereophotogrammetry.Results: A maximum mean error of 3.1 ± 1.8 deg and 1.9 ± 0.8 deg from the angle trajectory with correct IMU position was recorded respectively in the medio-lateral malposition and frontal-plane misalignment tests. Across the standard rehabilitation tasks, the mean distance between the IMU and gait analysis systems was on average smaller than 5°.Conclusions: These findings showed that the tested IMU based system has the necessary accuracy to be safely utilized in rehabilitation programs after orthopaedic treatments of the lower limb

Kinematic models of lower limb joints for musculo-skeletal modelling and optimization in gait analysis

Kinematic models of lower limb joints have several potential applications in musculoskeletal modelling of the locomotion apparatus, including the reproduction of the natural joint motion. These models have recently revealed their value also for in vivo motion analysis experiments, where the soft-tissue artefact is a critical known problem. This arises at the interface between the skin markers and the underlying bone, and can be reduced by defining multibody kinematic models of the lower limb and by running optimization processes aimed at obtaining estimates of position and orientation of relevant bones. With respect to standard methods based on the separate optimization of each single body segment, this technique makes it also possible to respect joint kinematic constraints. Whereas the hip joint is traditionally assumed as a 3 degrees of freedom ball and socket articulation, many previous studies have proposed a number of different kinematic models for the knee and ankle joints. Some of these are rigid, while others have compliant elements. Some models have clear anatomical correspondences and include real joint constraints; other models are more kinematically oriented, these being mainly aimed at reproducing joint kinematics. This paper provides a critical review of the kinematic models reported in literature for the major lower limb joints and used for the reduction of soft-tissue artefact. Advantages and disadvantages of these models are discussed, considering their anatomical significance, accuracy of predictions, computational costs, feasibility of personalization, and other features. Their use in the optimization process is also addressed, both in normal and pathological subjects

Location-Dependent Human Osteoarthritis Cartilage Response to Realistic Cyclic Loading: Ex-Vivo Analysis on Different Knee Compartments

Objective: Osteoarthritis (OA) is a multifactorial musculoskeletal disorder affecting mostly weight-bearing joints. Chondrocyte response to load is modulated by inflammatory mediators and factors involved in extracellular cartilage matrix (ECM) maintenance, but regulatory mechanisms are not fully clarified yet. By using a recently proposed experimental model combining biomechanical data with cartilage molecular information, basally and following ex-vivo load application, we aimed at improving the understanding of human cartilage response to cyclic mechanical compressive stimuli by including cartilage original anatomical position and OA degree as independent factors. Methods: 19 mono-compartmental Knee OA patients undergoing total knee replacement were recruited. Cartilage explants from four different femoral condyles zones and with different degeneration levels were collected. The response of cartilage samples, pooled according to OA score and anatomical position was tested ex-vivo in a bioreactor. Mechanical stimulation was obtained via a 3-MPa 1-Hz sinusoidal compressive load for 45-min to replicate average knee loading during normal walking. Samples were analysed for chondrocyte gene expression and ECM factor release. Results: Non parametric univariate and multivariate (generalized linear mixed model) analysis was performed to evaluate the effect of compression and IL-1β stimulation in relationship to the anatomical position, local disease severity and clinical parameters with a level of significance set at 0.05. We observed an anti-inflammatory effect of compression inducing a significant downmodulation of IL-6 and IL-8 levels correlated to the anatomical regions, but not to OA score. Moreover, ADAMTS5, PIICP, COMP and CS were upregulated by compression, whereas COL-2CAV was downmodulated, all in relationship to the anatomical position and to the OA degree. Conclusion: While unconfined compression testing may not be fully representative of the in-vivo biomechanical situation, this study demonstrates the importance to consider the original cartilage anatomical position for a reliable biomolecular analysis of knee OA metabolism following mechanical stimulation

Author Correction: 3D measurement techniques for the hindfoot alignment angle from weight-bearing CT in a clinical population

Cone-beam CT (CBCT) scans now enable accurate measurements on foot skeletal structures with the advantage of observing these in 3D and in weight-bearing. Among the most common skeletal deformities, the varus/valgus of the hindfoot is the most complex to be represented, and a number of measure proposals have been published. This study aims to analyze and to compare these measurements from CBCT scans in a real clinical population with large such deformity. Ten patients with severe acquired adult fatfoot and indication for surgery underwent CBCT scans (Carestream, USA) while standing on that leg, before and after surgical correction. Corresponding 3D shape of each bone of the distal shank and hindfoot were defned (Materialise, Belgium). Six diferent techniques from the literature were used to calculate the varus/valgus deformity, i.e. the inclination of the hindfoot in the frontal plane of the shank. Standard clinical measurements by goniometers were taken for comparison. According to these techniques, and starting from a careful 3D reconstruction of the relevant foot skeletal structures, a large spectrum of measurements was found to represent the same hindfoot alignment angle. Most of them were very diferent from the traditional clinical measures. The assessment of the pre-operative valgus deformity and of the corresponding post-operative correction varied considerably. CBCT fnally allows 3D assessment of foot deformities in weight-bearing. Measurements from the diferent available techniques do not compare well, as they are based on very diferent approaches. It is recommended to be aware of the anatomical and functional concepts behind these techniques before clinical and surgical conclusions