Efecto de la osteotomía medializante de calcáneo sobre tejidos blandos de soporte del arco plantar: un estudio computacional / Effect of the calcaneal medializing osteotomy on soft tissues supporting the plantar arch: a computational study

La osteotomía medializante de calcáneo forma parte del elenco de opciones de tratamiento en el pie plano adquirido en adultos. La corrección estructural que se consigue es ampliamente conocida. Sin embargo, el efecto de este procedimiento sobre los tejidos blandos que soportan el arco plantar ha sido poco estudiado, pues experimentalmente no es posible cuantificar las variaciones de tensión y deformación generadas. Por lo tanto, el objetivo de este estudio fue evaluar el efecto que tiene la osteotomía medializante de calcáneo sobre el tejido blando que soporta el arco plantar, usando un modelo computacional de pie humano diseñado con un enfoque clínico. El modelo por elementos finitos propuesto fue reconstruido a partir de imágenes de tomografías computarizadas de un paciente sano. Se incluyeron todos los huesos del pie, la fascia plantar, cartílagos, ligamentos plantares y el ligamento calcáneo-navicular, respetando su distribución anatómica y propiedades biomecánicas. Las simulaciones fueron realizadas emulando la fase de apoyo monopodal de la marcha humana de un adulto. El efecto sobre cada tejido fue evaluado siguiendo criterios clínicos y biomecánicos. Los resultados muestran que la osteotomía de calcáneo reduce la tensión generada normalmente sobre los tejidos evaluados, siendo el efecto sobre el ligamento calcáneo-navicular y la fascia plantar los más notables. Los resultados de deformación obtenidos son consistentes con ensayos experimentales y el conocimiento clínico. La versatilidad de este modelo permite la valoración objetiva de diferentes condiciones y apoya la toma de decisión para el tratamiento del pie plano adquirido en adultos en estadios medio y avanzado

Medializing calcaneal osteotomy forms part of the treatment options for adult acquired flat foot. The structural correction that is achieved is widely known. However, the effect of this procedure on the soft tissues that support the plantar arch has been little studied, since it is not possible to quantify experimentally the tension and deformation variations generated. Therefore, the objective of this study was to evaluate the effect of medializing calcaneal osteotomy on the soft tissue that supports the plantar arch, using a computational model of the human foot designed with a clinical approach. The proposed finite element model was reconstructed from computerized tomography images of a healthy patient. All the bones of the foot, the plantar fascia, cartilages, plantar ligaments and the calcaneus-navicular ligament were included, respecting their anatomical distribution and biomechanical properties. Simulations were performed emulating the monopodal support phase of the human walk of an adult. The effect on each tissue was evaluated according to clinical and biomechanical criteria. The results show that calcaneal osteotomy reduces the tension normally generated on the evaluated tissues, with the effect on the calcaneus-navicular ligament and the plantar fascia being the most notable. The deformation results obtained are consistent with experimental tests and clinical knowledge. The versatility of this model allows the objective assessment of different conditions and supports decision making for the treatment of adult acquired flat foot in middle and advanced stages

Effect of the calcaneal medializing osteotomy on soft tissues supporting the plantar arch: A computational study. / Efecto de la osteotomía medializante de calcáneo sobre tejidos blandos de soporte del arco plantar: un estudio computacional.

Medializing calcaneal osteotomy forms part of the treatment options for adult acquired flat foot. The structural correction that is achieved is widely known. However, the effect of this procedure on the soft tissues that support the plantar arch has been little studied, since it is not possible to quantify experimentally the tension and deformation variations generated. Therefore, the objective of this study was to evaluate the effect of medializing calcaneal osteotomy on the soft tissue that supports the plantar arch, using a computational model of the human foot designed with a clinical approach. The proposed finite element model was reconstructed from computerized tomography images of a healthy patient. All the bones of the foot, the plantar fascia, cartilages, plantar ligaments and the calcaneus-navicular ligament were included, respecting their anatomical distribution and biomechanical properties. Simulations were performed emulating the monopodal support phase of the human walk of an adult. The effect on each tissue was evaluated according to clinical and biomechanical criteria. The results show that calcaneal osteotomy reduces the tension normally generated on the evaluated tissues, with the effect on the calcaneus-navicular ligament and the plantar fascia being the most notable. The deformation results obtained are consistent with experimental tests and clinical knowledge. The versatility of this model allows the objective assessment of different conditions and supports decision making for the treatment of adult acquired flat foot in middle and advanced stages.

Mechanical stress redistribution in the calcaneus after autologous bone harvesting.

The calcaneus is a desirable site for harvesting autologous bone for use in foot surgery. However, fracture of the calcaneus is a serious complication associated with bone harvesting from this site. Currently it is unknown how much bone may be safely harvested from the calcaneus without inducing a fracture. The purpose of this study was to investigate the effect of progressive bone removal from the calcaneus onto the mechanical stress redistribution of the foot, and therefore on the increase in fracture risk. Different loads were applied on the talus to evaluate the calcaneus stress distribution at different situations. Because of the potential increase in mechanical stress in the calcaneus, secondary to contraction of the Achilles tendon, we also evaluated the mechanical behavior properties of the foot with increasing traction force in the Achilles tendon. A three-dimensional (3D) finite element (FE) model developed from CT images obtained from a healthy individual was used to compute displacement, tension and compression stresses in six situations, including intact foot, and five depth of the bone block removed, with a maximum depth of 7.5 mm. The results from these simulations indicated that when the maximum load was applied at the Achilles tendon, the tension stress increased from 42.16 MPa in the intact foot to 86.28 MPa with maximum bone harvesting. Furthermore, as the volume of bone extracted from the calcaneus increases, there is a redistribution of stresses that differs significantly from the intact foot. In fact, although the maximum stress was not significantly affected by increasing the volume of bone harvested-except when increasing the Achilles tendon force-, stresses did increase in areas of the calcaneus is vulnerable to injury, leading to an increase in fracture risk.

Load transfer mechanism for different metatarsal geometries: a finite element study.

The load transfer mechanism across the skeleton of the human foot is very important to understand its biomechanical function. In this work, we develop several computational models to compare the biomechanical response of different metatarsal geometries. Finite element 3D simulations of feet reconstructed from computer tomography (CT) scans were used to evaluate the stress/strain distributions during the stance posture. The numerical predictions for pathological and healthy foot geometries present different load transfer mechanisms that can provide a biomechanical explanation of why some metatarsal geometrical configurations cause different foot skeletal stresses. The most significant result in all cases was a reduction between 20% and 30% of the peak load supported by the first metatarsal. Therefore, we conclude that a clearly unloaded first metatarsal, overloading the rest, is a risk factor to induce metatarsalgia.