Quantitative Assessment of Hallux Valgus Metatarsal Pronation with the Use of Inertial Axes

Hallux Valgus affects the feet of people of all ages, predominantly elderly women. While the current standard of care involves x-rays, bunions are a three-dimensional deformity which includes rotation of the longitudinal axis of the first metatarsal. While this rotation has been proven to exist there currently is no standard means to quantify this angle. Recent studies have evaluated this angle using solid models of the foot which analyzed this rotation using points picked on boney landmarks. While this is a valid way of identifying the rotation, complications arise with replicability between raters. The current research seeks to show that the inertial (principal) axes from these anatomical models not only properly measures this angle but also alleviates the issues revolving around reproducibility

Design of an Implant for First Metatarsophalangeal Joint Hemiarthroplasty

Osteoarthritis (OA) is the most common form of arthritis and it affects 27 million US adults. OA disease involves all of the tissues of the diarthrodial joint and ultimately, may lead to softening, ulceration, loss of articular cartilage, sclerosis and polished appearance of the subchondral bone, osteophytes, and subchondral cysts. The first metatarsophalangeal joint (MTPJ1) is affected in up to 42 cases of OA. Besides osteoarthritis, other conditions such as rheumatoid arthritis and gout also affect the MTPJ1. Involvement of MTPJ1 with these conditions invariably leads to deformed toe such as hallux valgus and hallux rigidus. Over 150 surgical techniques exist for treatment of hallux deformity, which includes cheilectomy, arthrodesis, osteotomy, resection arthroplasty, and replacement of part or the entire articular surface with an implant. A hemi-implant, which partially replaces the 1st metatarsal head with minimal bone resection and without altering the sesamoid articulation has shown promising results and gives superior postoperative range of motion and pain reductions. But the geometry of such implants has not been explained in any literature and there are no details of the data used for designing such implants. An anatomically based approach to design the geometry of an MTPJ1 implant is needed in order to best fit the articulating surface of the adjacent phalanx. In the current study, a method was developed for designing a hemiarthroplasty implant for MTPJ1 based upon the morphology of metatarsal. Ninety-seven metatarsal osteological specimens were scanned using a laser scanner to obtain 3D surface data. After aligning the surface data, the articular surface of each metatarsal head (MTH1) superior to the inter-condylar ridge were characterized by a section of an ellipsoid using non-linear unconstrained optimization (NLUO) and the section of the ellipsoid forms the surface of the implant. The implants based upon osteological specimens had a very good fit to metatarsal articulating surface with root mean

Design of an Implant for First Metatarsophalangeal Joint Hemiarthroplasty

Osteoarthritis (OA) is the most common form of arthritis and it affects 27 million US adults. OA disease involves all of the tissues of the diarthrodial joint and ultimately, may lead to softening, ulceration, loss of articular cartilage, sclerosis and polished appearance of the subchondral bone, osteophytes, and subchondral cysts. The first metatarsophalangeal joint (MTPJ1) is affected in up to 42 cases of OA. Besides osteoarthritis, other conditions such as rheumatoid arthritis and gout also affect the MTPJ1. Involvement of MTPJ1 with these conditions invariably leads to deformed toe such as hallux valgus and hallux rigidus. Over 150 surgical techniques exist for treatment of hallux deformity, which includes cheilectomy, arthrodesis, osteotomy, resection arthroplasty, and replacement of part or the entire articular surface with an implant. A hemi-implant, which partially replaces the 1st metatarsal head with minimal bone resection and without altering the sesamoid articulation has shown promising results and gives superior postoperative range of motion and pain reductions. But the geometry of such implants has not been explained in any literature and there are no details of the data used for designing such implants. An anatomically based approach to design the geometry of an MTPJ1 implant is needed in order to best fit the articulating surface of the adjacent phalanx. In the current study, a method was developed for designing a hemiarthroplasty implant for MTPJ1 based upon the morphology of metatarsal. Ninety-seven metatarsal osteological specimens were scanned using a laser scanner to obtain 3D surface data. After aligning the surface data, the articular surface of each metatarsal head (MTH1) superior to the inter-condylar ridge were characterized by a section of an ellipsoid using non-linear unconstrained optimization (NLUO) and the section of the ellipsoid forms the surface of the implant. The implants based upon osteological specimens had a very good fit to metatarsal articulating surface with root mean

Crista Volume Measured from 3D Reconstruction of Weightbearing CT Scans Shows a Relationship to Sesamoid Station

The hallux valgus (HV) deformity results in progressive subluxation of the sesamoids from their position (station) under the plantar surface of the first metatarsal head. This subluxation may result in erosion of the crista that separates the sesamoid grooves due to contact with the tibial sesamoid during weightbearing. While previous work using weightbearing CT (WBCT) scans has suggested that tibial sesamoid position is associated with degenerative change of the sesamoid metatarsal joint (Katsui FAI), no studies have quantified the relationship between sesamoid metatarsal degenerative changes and sesamoid subluxation. The purpose of the current investigation is to examine the relationship of the volume of the crista to first metatarsal pronation and sesamoid station, using three-dimensional models of patients’ deformities created from WBCT scans. Thirty-nine HV patients and nine normal subjects underwent weightbearing or simulated weightbearing CT (WBCT) imaging. Crista volume was determined using a line drawn to connect the nadir of each sulcus on either side of the intersesamoidal crista for the length of the crista. WBCT scans were used to establish sesamoid position using a four-stage scale (Kim FAI 2015) and quantify first metatarsal pronation using 3D reconstructions as previously described (Campbell FAI 2018). Our study found that HV patients have significantly lower mean crista volumes compared to normal patients. Crista volume was strongly correlated with sesamoid subluxation/station, which suggests that tibial sesamoid subluxation results in erosion of the crista. In contrast, the pronation deformity was not associated with crista volume demonstrating that the degenerative changes of the sesamoid metatarsal are not related to the rotational deformity of the first metatarsal. This supports the hypothesis that tibial sesamoid subluxation may result in osteoarthritis of the sesamoid metatarsal joint and may be an overlooked source of pain in HV. These results are the first to demonstrate that medial sesamoid subluxation as determined by sesamoid station results in erosion of the crista

An Assessment of Hallux Valgus

The foot is an essential component for human gait and begins the propagation of forces in the lower extremity of the body. One of the most common conditions that produce forefoot pain is hallux valgus (HV). HV alters or restricts normal body kinematics, influences physical mobility and increases the risk of falling. The root cause of HV has not been fully determined. While the principal kinematics are known and understood, the etiology still remains unclear. Clinically standard planar radiographs are employed but cannot accurately capture first metatarsal pronation, which is known to occur in the onset of hallux valgus. Previous research has also shown changes occur in bone density near the midfoot of cadavers with hallux valgus. Plantar pressure models have shown patients with hallux valgus have increased loading at the big toe and metatarsal head. In this study, we analyzed the forefoot of normal and HV patients groups to measure in vivo density and bone orientation. We also developed patient specific three-dimensional finite element models of the first and second rays of the foot to develop predictions of stress on the metatarsal in the progression of the HV. We found changes in the density profile in patients with hallux valgus. We quantified pronation in the first metatarsal and found differences in the patients with hallux valgus. The pronation reported here is the first true three-dimensional measurement of metatarsal rotation due to the hallux valgus deformity. We found differences in contact forces at the metatarsal head and metatarsal base due to hallux valgus. This study is the first to report an estimate of pressure at the metatarsal sesamoid interface. We found increased pressure due to the altered kinematics as a result of HV, which can lead to pain and erosion at the metatarsal head

Computational foot modeling for clinical assessment

Esta Tesis desarrolla un modelo de elementos finitos del pie humano completo y detallado en tres dimensiones para avanzar hacia una simulación computacional más precisa que proporcione información realista y relevante para la práctica clínica. Desde el punto de vista ingenieril, el pie humano es una compleja estructura de pequeños huesos, soportados por fuertes ligamentos y controlada por una red de músculos y tendones con una capacidad de respuesta mecánica excepcional. La barrera actual en la simulación computacional del pie es la inclusión de estas estructuras musculotendinosas en los modelos. Para avanzar en esta dirección, se crea un modelo de elementos finitos del pie completo y detallado con geometría real de la estructura interna diferenciando hueso cortical y esponjoso, tendón, músculo, cartílago y grasa. Se realizan ensayos experimentales de los tendones del pie y la suela plantar para determinar sus propiedades materiales y estructurales y caracterizar computacionalmente su comportamiento mecánico no lineal. Estos avances están orientados hacia la mejora de la representación geométrica y caracterización del tejido de los componentes internos del pie. El modelo desarrollado en esta Tesis puede usarse en el campo de la biomecánica en áreas de ortopedia, lesiones, tratamiento, cirugía y deporte. La investigación está estructurada por capítulos en los cuales se desarrollan pequeños avances hacia el objetivo principal de la Tesis al mismo tiempo que se aplica el potencial de estos avances a casos particulares. Estas contribuciones parciales en el área de los ensayos experimentales son: la determinación de un completo conjunto de datos de las propiedades mecánicas de los tendones del pie, la definición de un criterio para cuantificar las regiones de la curva de tensión-deformación del tendón y el análisis de la respuesta a compresión de la suela plantar en función de la posición. Y, en el área de la biomecánica clínica las contribuciones son: la investigación de un parámetro del esqueleto como factor etiológico del hallux valgus, el estudio de sensibilidad de la fuerza de los cinco mayores tendones estabilizadores, el análisis cuasi-estático de la fase de apoyo de la marcha y el estudio del mecanismo de absorción de la fuerza de impacto del pie durante la carrera descalzo a diferentes ángulos de impacto.In this Thesis, a complete detailed three-dimensional finite element model of the human foot is described to advance towards a more refined computational simulation which provides realistic and meaningful information for clinical practice. From an engineering perspective, the human foot is a complex structure of small bones supported by strong ligaments and controlled by a network of tendons and muscles that achieves a superb mechanical responsiveness. The current barrier in foot computational simulation is the inclusion of these musculotendinous structures in the models. To advance in this direction, a complete detailed three-dimensional foot finite element model with actual geometry of the inner structure is created differentiating cortical and trabecular bone, tendon, muscle, cartilage and fat tissues. Experimental tests of foot tendons and plantar soles are performed to determine their structural and material properties and to characterize computationally their non-linear mechanical behavior. Those advances are oriented to refine the geometry and the tissue characterization of the internal foot components. The model developed in this Thesis can be used in the field of biomechanics, in the areas of orthopedics, injury, treatment, surgery and sports biomechanics. The research is structured by chapters where small steps towards the main objective are developed and the potential of these advances are applied to particular cases. These partial contributions in the area of the experimental testing are: the determination of a complete dataset of the mechanical properties of the balance foot tendons, the definition of a criteria to quantify the regions of the tendon stress-strain curve and the analysis of the compressive response of plantar soft tissue as function of the location. And, in the area of clinical biomechanics the contributions are: the investigation of a skeletal parameter as etiology factor of the hallux valgus, the tendon force sensitivity study of the five major stabilizer tendons, the quasi-static analysis of the midstance phase of walking and the study of the impact absorption mechanism of the foot during barefoot running at different strike patterns

Development of a fixing and adjusting device for Chevron osteotomy

O Hallux Valgus é uma deformação que ocorre no primeiro metatarso do pé, podendo em alguns casos atingir também a falange. O tratamento desta deformação obriga, na maioria das situações, a um procedimento cirúrgico. A Osteotomia de Chevron é o tipo de cirurgia habitualmente implementada, sendo os cortes e perfuração do osso normalmente realizados pelo cirurgião sem o recurso a dispositivos específicos de apoio e guiamento. A possibilidade de desenvolver um dispositivo de apoio que permita aumentar a precisão na realização desta cirurgia foi o foco deste trabalho de Mestrado. Este trabalho apresenta um novo dispositivo para apoio na execução da Osteotomia de Chevron, desenvolvido em estreita colaboração com uma equipa de Ortopedistas. Inicialmente foi feita uma identificação da técnica e dos procedimentos associados à cirurgia de Chevron. Depois foi desenvolvido um modelo 3D de um metatarso, que serviu de base ao desenvolvimento do conceito do dispositivo. O dispositivo desenvolvido incorpora diferentes configurações, tendo como base uma estrutura puramente mecânica. O Protótipo do dispositivo foi produzido com tecnologias de fabrico aditivo e com recurso a materiais e componentes compatíveis com a sua utilização em contexto real. A evolução na conceção do dispositivo mostrou a identificação de características que permitiram o seu teste experimental com a aquisição de dados associados à precisão de corte. Os resultados evidenciaram adequada robustez do dispositivo, que pode desempenhar uma missão de relevo no apoio ao processo cirúrgico da osteotomia de Chevron

Biomechanical study of foot with hallux valgus deformity

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University LondonBackground: Hallux valgus (HV) is one of the most common foot deformities. Considering the fact that 23% of adults develop such condition during their lifetime, understanding HV is badly needed. Plantar pressure technologies are used widely for determination of biomechanical changes in foot during walking. There are already published claims relating to the pressure distribution of HV condition. Association of HV to sole pressure widely presented as a means of identifying such condition. Methods: plantar pressure patterns can be linked to the deformity progression or existence, extracting some patterns out of force measurements can be beneficial in recognizing the patients with and without deformity. The dynamic changes of the forces that applied to the fore-foot in volunteers with and without HV when they walked at self-selected and fast speeds were examined. Furthermore, Markovian chain transfer matrices were used to obtain the transfer coefficient of the force among five metatarsals. Another method was to measure the lateral flexibility of the 1st metatarsal joint as an indication of HV deformity by Motion Capture cameras. Finally, two 3D feet models of HV and non-HV volunteers were made in Mimics software and then in FEA (finite element analysis) the stress distribution under the foot was validated with the experiments. Results: The higher forces were observed under the 2nd, 3rd and 1st metatarsal heads in both speeds but the results obtained were significantly different among groups and in fast speed and under 3rd and 1st metatarsals in self-selected speed. In this study the use of Markovian transfer matrices as a means of characterising the gait pattern is new and novel. It was intended that highest coefficients of the matrix would indicate the existence of HV, however studies showed that the biggest difference between HV and non HV patients was the scatter of the coefficients which shown to give very strong indication of the existence of HV. It was shown by kinematic studies and also it was found that the 1st metatarsal joint was significantly more flexible in HV patients compared to non–HV individuals. Finally FEA studies has shown that in the 3D feet models of both volunteers (with and without HV), the highest stress was under the heal area and then transfers towards fore-foot area. In patient with HV the higher force were seen under the 1st to 3rd metatarsal heads compare to non-HV individual and each model was validated its related experiments. Conclusion: it was observed that there was a significant variability of pressure distribution of the same individual from one trial to another indicating that getting consistent pressure pattern is an important hurdle to overcome in our studies, raised loading is observed on Metatarsal 2, 3 and 1 in HV patients and it was possible to give statistical significance to these findings. In this thesis, it was intended to obtain early diagnostics of HV condition and much work was put in this, however outcome was not conclusive. However it was possible to distinguish HV form non-HV volunteers from the scatter characteristics of the transfer pattern. Investigation of the 1st metatarsal joint laxity of non-HV and HV patients revealed that HV individuals were significantly higher compared to non–HV volunteers and this can be used as an indication of HV existence. Finally, the 3D models show that FEA is a reliable tool as the FEA study showed good correlation with the experimental results

Anatomical Variation and Clinical Diagnosis

In the anatomical sciences, it has long been recognized that the human body displays a range of morphological patterns and arrangements, often termed “anatomical variation”. Variations are relatively common throughout the body and may cause or contribute to significant medical conditions. An understanding of normal anatomical variation is vital for performing a broad range of surgical and other medical procedures and treatment modalities. However, despite their importance to effective diagnosis and treatment, such variations are often overlooked in medical school curricula and clinical practice. Recent advances in imaging techniques and a renewed interest in variation in dissection-based gross anatomy laboratories have facilitated the identification of many such variants. The aim of this Special Issue of Diagnostics is to highlight previously under-recognized anatomical variations and to discuss them in a clinical context. In particular, this Special Issue focuses on variants that have specific implications for diagnosis and treatment and explores their potential consequences. The scope of this Special Issue includes studies on gross anatomy, radiology, surgical anatomy, histology, and neuroanatomy