Fien Burg

Alterated Talar and Navicular Bone Morphology Is Associated with Pes Planus Deformity: A CT-Scan Study

We compared bone and articular morphology of the talus and navicular in clinically diagnosed flatfeet and evaluated their potential contribution to talo‐navicular joint instability. We used CT images to develop 3D models of talus and navicular bones of 10 clinically diagnosed flatfeet and 15 non‐flatfeet. We quantified their global bone dimensions, inclination and dimensions of the articular surfaces and their curvatures. Additionally, ratios of six talar and navicular dimensions were calculated. The values for these parameters were then compared between both groups. In flatfeet, the talar head faced more proximal and its width was larger compared to non‐flatfeet. Also the navicular cup faced more proximal and its depth was significantly increased. Furthermore, we observed a more protruding talar head compared to the navicular cup in the control group with the articular surface depth being relatively larger for the navicular cups when compared to the talus in flatfeet. The ratio of the talar and navicular articular surface height was decreased in flatfeet, suggesting increased height of navicular cups relative to the articulating talar heads. Our results show that flatfoot deformity is associated with morphological changes of talar and navicular articular surfaces that can favor medial arch collapse and forefoot abduction.

Specimen-specific tibial kinematics model for in vitro gait simulations

Until now, the methods used to set up in vitro gait simulations were not specimen specific, inflicting several problems when dealing with specimens of considerably different dimensions and requiring arbitrary parameter tuning of the control variables. We constructed a model that accounts for the geometric dimensions of the specimen and is able to predict the tibial kinematics during the stance phase. The model predicts tibial kinematics of in vivo subjects with very good accuracy. Furthermore, if used in in vitro gait simulation studies, it is able to recreate physiological vertical ground reaction forces. By using this methodology, in vitro studies can be performed by taking the specimen variability into account, avoiding pitfalls with specimens of different dimensions.

Three-dimensional quantitative analysis of healthy foot shape: a proof of concept study

BackgroundFoot morphology has received increasing attention from both biomechanics researches and footwear manufacturers. Usually, the morphology of the foot is quantified by 2D footprints. However, footprint quantification ignores the foot’s vertical dimension and hence, does not allow accurate quantification of complex 3D foot shape.MethodsThe shape variation of healthy 3D feet in a population of 31 adult women and 31 adult men who live in Belgium was studied using geometric morphometric methods. The effect of different factors such as sex, age, shoe size, frequency of sport activity, Body Mass Index (BMI), foot asymmetry, and foot loading on foot shape was investigated. Correlation between these factors and foot shape was examined using multivariate linear regression.ResultsThe complex nature of a foot’s 3D shape leads to high variability in healthy populations. After normalizing for scale, the major axes of variation in foot morphology are (in order of decreasing variance): arch height, combined ball width and inter-toe distance, global foot width, hallux bone orientation (valgus-varus), foot type (e.g. Egyptian, Greek), and midfoot width. These first six modes of variation capture 92.59% of the total shape variation. Higher BMI results in increased ankle width, Achilles tendon width, heel width and a thicker forefoot along the dorsoplantar axis. Age was found to be associated with heel width, Achilles tendon width, toe height and hallux orientation. A bigger shoe size was found to be associated with a narrow Achilles tendon, a hallux varus, a narrow heel, heel expansion along the posterior direction, and a lower arch compared to smaller shoe size. Sex was found to be associated with differences in ankle width, Achilles tendon width, and heel width. Frequency of sport activity was associated with Achilles tendon width and toe height.ConclusionA detailed analysis of the 3D foot shape, allowed by geometric morphometrics, provides insights in foot variations in three dimensions that can not be obtained from 2D footprints. These insights could be applied in various scientific disciplines, including orthotics and shoe design.

Foot abnormality mapping using statistical shape modelling

About 20% of the population suffer from disabling foot or ankle pain that require the use of foot orthotics. Traditionally, those foot orthotics are designed manually, but digital procedures are desired to provide a faster, more objective, and more reliable workflow. In this study, we introduce a method for detecting shape abnormalities in feet for the purposes of pathology diagnosis and orthotic design. The proposed method consists of two phases. In the training phase, a statistical 3D foot model (based on 42 healthy subjects) is built. In the test phase, the landmarks of a new 3D foot scan are compared to the trained model. A landmark is detected as an outlier if it is in the extreme ranges. This testing process is repeated at all landmarks to identify all abnormal foot regions. Preliminary results show that, when testing a foot of a known pathology (hallux valgus, heel spur, foot pronation), we are able to detect abnormal regions accurately. We also examined the effect of using rigid or similarity-based alignment during 3D model building and abnormality detection. We show that our proposed method is a faster and a more objective approach than traditional approaches for abnormality detection of the foot. As such, this method may prove useful in the medical diagnosis of foot pathologies and in automated orthotic design.

Inertial control: a novel technique for in-vitro analysis of foot function

Background In-vitro gait simulations have great potential, allowing a systematic analysis of the foot function. However, it is important that the loading conditions are realistic i.e. physiologic ground reaction forces (GRF). In most experiments, in-vivo measured GRF can be imposed [1,2]. However in experimental designs that evaluate the effect of altered muscle forces on foot motion this is more complex; the effect of the altered muscle activity on the loading and kinematics cannot be taken into consideration. Therefore, we investigated the use of a new technique to simulate such cases with realistic loading conditions.