Estudio biomecánico comparativo de dos configuraciones de tornillos cementados en una fractura simulada de húmero proximal fijada con placa y tornillos bloqueados / Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate

Introducción: La utilización de tornillos cementados en la fijación interna de fracturas de húmero proximal con placas bloqueadas parece mejorar la estabilidad del implante y disminuir las complicaciones asociadas al fracaso de síntesis. Sin embargo, la combinación óptima de tornillos cementados se desconoce. El objetivo de este estudio fue analizar la estabilidad relativa de dos configuraciones de tornillos cementados sometidos a una fuerza de compresión axial en una fractura simulada de húmero proximal. Material y métodos: Se realizó una osteotomía del cuello quirúrgico en cinco pares de húmeros embalsamados con una edad media de 74 años (rango 46-93), fijados con una placa de acero inoxidable con tornillos bloqueados. En cada par de húmeros, en el húmero derecho se cementaron los tornillos A y E, y en el lado contralateral se cementaron los tornillos B y D. Cada espécimen fue testado inicialmente mediante una carga cíclica de compresión axial durante 6.000 ciclos para evaluar el movimiento interfragmentario (estudio dinámico). Al final de la prueba, los especímenes se sometieron a una carga de compresión axial progresiva para medir la rigidez de la construcción (estudio estático). Resultados: No se encontraron diferencias estadísticamente significativas en la movilidad interfragmentaria entre las dos configuraciones de tornillos cementados en el estudio dinámico (p=0,463). Cuando se sometieron a rotura, los especímenes con tornillos cementados en las hileras B y D presentaron una carga de rotura mayor (2218N vs. 2105, p=0,901) y una mayor rigidez (125N/mm vs. 106N/mm, p=0,672); sin embargo, ninguna de estas diferencias fue estadísticamente significativa. Conclusiones: La configuración de los tornillos cementados utilizadas en este estudio no influyen en la estabilidad del implante cuando se aplica una carga cíclica de baja energía. La cementación de los tornillos de las hileras B y D proporciona una resistencia similar a la cementación de los tornillos...(AU)

Introduction: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. Material and methods: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46–93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). Results: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. Conclusions: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.(AU)

[Translated article] Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate / Estudio biomecánico comparativo de 2 configuraciones de tornillos cementados en una fractura simulada de húmero proximal fijada con placa y tornillos bloqueados

Introducción: La utilización de tornillos cementados en la fijación interna de fracturas de húmero proximal con placas bloqueadas parece mejorar la estabilidad del implante y disminuir las complicaciones asociadas al fracaso de síntesis. Sin embargo, la combinación óptima de tornillos cementados se desconoce. El objetivo de este estudio fue analizar la estabilidad relativa de dos configuraciones de tornillos cementados sometidos a una fuerza de compresión axial en una fractura simulada de húmero proximal. Material y métodos: Se realizó una osteotomía del cuello quirúrgico en cinco pares de húmeros embalsamados con una edad media de 74 años (rango 46-93), fijados con una placa de acero inoxidable con tornillos bloqueados. En cada par de húmeros, en el húmero derecho se cementaron los tornillos A y E, y en el lado contralateral se cementaron los tornillos B y D. Cada espécimen fue testado inicialmente mediante una carga cíclica de compresión axial durante 6.000 ciclos para evaluar el movimiento interfragmentario (estudio dinámico). Al final de la prueba, los especímenes se sometieron a una carga de compresión axial progresiva para medir la rigidez de la construcción (estudio estático). Resultados: No se encontraron diferencias estadísticamente significativas en la movilidad interfragmentaria entre las dos configuraciones de tornillos cementados en el estudio dinámico (p=0,463). Cuando se sometieron a rotura, los especímenes con tornillos cementados en las hileras B y D presentaron una carga de rotura mayor (2218N vs. 2105, p=0,901) y una mayor rigidez (125N/mm vs. 106N/mm, p=0,672); sin embargo, ninguna de estas diferencias fue estadísticamente significativa. Conclusiones: La configuración de los tornillos cementados utilizadas en este estudio no influyen en la estabilidad del implante cuando se aplica una carga cíclica de baja energía. La cementación de los tornillos de las hileras B y D proporciona una resistencia similar a la cementación de los tornillos...(AU)

Introduction: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. Material and methods: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46–93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). Results: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. Conclusions: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.(AU)

Mejora significativa de la estabilidad a carga axial con el fijador externo pélvico pretensado: análisis biomecánico en un modelo con lesión Tile tipo C / Significant improvement in axial load stability with the pre-tensioned pelvic external fixator: A biomechanical analysis in a model with type C Tile lesion

Objetivo: Comprobar si la aplicación de fijación externa mediante barra curva conectada a clavos de Schanz supraacetabulares confiere mayor estabilidad al anillo pélvico con una lesión tipo Tile C1 cuando se realiza el montaje con la barra pretensada que con el montaje estándar (sin pretensar). Material y métodos: Pelvis sintéticas (N=5) con lesión verticalmente inestable estabilizada con ambos montajes, se sometieron a carga axial progresiva. Se midieron las fuerzas aplicadas y las variaciones en las posiciones de marcadores situados en la articulación sacroilíaca y la sínfisis se registraron con un sistema óptico. Se determinaron los desplazamientos relativos entre las superficies lesionadas, la rigidez, la resistencia y el modo de fallo de cada montaje. Resultados: Con el fijador pretensado, la rigidez del montaje en la articulación sacroilíaca resultó muy superior a la del montaje convencional (p=0,043) multiplicándola por 3,45, siendo 2,06 veces mayor en la sínfisis. La resistencia ante el fallo también fue superior, multiplicándola por 2 (p=0,043). Discusión: El aumento de estabilidad a carga axial con el fijador externo pretensado concuerda con su capacidad de producir compresión activa simultánea en los elementos posteriores y anteriores del anillo pélvico, demostrada previamente. Este resultado soporta los excelentes resultados clínicos preliminares obtenidos como tratamiento provisional. Conclusiones: El fijador externo pretensado aumenta la estabilidad axial de los elementos óseos posteriores del anillo pélvico con lesión tipo Tile C1 en modelo sintético, sin disminuir la capacidad de estabilización anterior propia de la fijación externa anterior.(AU)

Objective: The aim of our work is to check if the use of a pre-tensed bar connected to 2supra-acetabular Schanz pins is more stable in a pelvic with a tile C1 injury. Material and methods: We used synthetic pelvis (N=5) with a unstable vertical injury, stabilized with both the standard and the pre-tensed system. They both were submitted to axial loading. We measured applied forces and the position of markers that were positioned in the sacroiliac and symphysis joints. We determined the relative movements between injured surfaces, rigidity, resistance and when each system failed. Results: When using the pre-tensed fixator, the rigidity was much higher in the sacro-iliac joint (P=.043) being 3.45 times higher, being also 2.06 times higher in pubic symphysis (P=.043). The resistance against failure was 2 times higher too (P=.043). Discussion: The increased axial stability with the pre-tensed external fixator accords with its ability to make active compression in both posterior and anterior elements of the pelvic ring, which was previously demonstrated. This result supports the preliminary clinic outcomes that were obtained. Conclusions: The pre-tensed external fixator increases the axial stability of the pelvic ring's posterior elements in a synthethic pelvis with a Tile C1 injury, without decreasing it's capacity to achieve an anterior stability.(AU)

[Translated article] Significant improvement in axial load stability with the pre-tensioned pelvic external fixator: A biomechanical analysis in a model with type C Tile lesion / Mejora significativa de la estabilidad a carga axial con el fijador externo pélvico pretensado: análisis biomecánico en un modelo con lesión Tile tipo C

Objetivo: Comprobar si la aplicación de fijación externa mediante barra curva conectada a clavos de Schanz supraacetabulares confiere mayor estabilidad al anillo pélvico con una lesión tipo Tile C1 cuando se realiza el montaje con la barra pretensada que con el montaje estándar (sin pretensar). Material y métodos: Pelvis sintéticas (N=5) con lesión verticalmente inestable estabilizada con ambos montajes, se sometieron a carga axial progresiva. Se midieron las fuerzas aplicadas y las variaciones en las posiciones de marcadores situados en la articulación sacroilíaca y la sínfisis se registraron con un sistema óptico. Se determinaron los desplazamientos relativos entre las superficies lesionadas, la rigidez, la resistencia y el modo de fallo de cada montaje. Resultados: Con el fijador pretensado, la rigidez del montaje en la articulación sacroilíaca resultó muy superior a la del montaje convencional (p=0,043) multiplicándola por 3,45, siendo 2,06 veces mayor en la sínfisis. La resistencia ante el fallo también fue superior, multiplicándola por 2 (p=0,043). Discusión: El aumento de estabilidad a carga axial con el fijador externo pretensado concuerda con su capacidad de producir compresión activa simultánea en los elementos posteriores y anteriores del anillo pélvico, demostrada previamente. Este resultado soporta los excelentes resultados clínicos preliminares obtenidos como tratamiento provisional. Conclusiones: El fijador externo pretensado aumenta la estabilidad axial de los elementos óseos posteriores del anillo pélvico con lesión tipo Tile C1 en modelo sintético, sin disminuir la capacidad de estabilización anterior propia de la fijación externa anterior.(AU)

Objective: The aim of our work is to check if the use of a pre-tensed bar connected to 2supra-acetabular Schanz pins is more stable in a pelvic with a tile C1 injury. Material and methods: We used synthetic pelvis (N=5) with a unstable vertical injury, stabilized with both the standard and the pre-tensed system. They both were submitted to axial loading. We measured applied forces and the position of markers that were positioned in the sacroiliac and symphysis joints. We determined the relative movements between injured surfaces, rigidity, resistance and when each system failed. Results: When using the pre-tensed fixator, the rigidity was much higher in the sacro-iliac joint (P=.043) being 3.45 times higher, being also 2.06 times higher in pubic symphysis (P=.043). The resistance against failure was 2 times higher too (P=.043). Discussion: The increased axial stability with the pre-tensed external fixator accords with its ability to make active compression in both posterior and anterior elements of the pelvic ring, which was previously demonstrated. This result supports the preliminary clinic outcomes that were obtained. Conclusions: The pre-tensed external fixator increases the axial stability of the pelvic ring's posterior elements in a synthethic pelvis with a Tile C1 injury, without decreasing it's capacity to achieve an anterior stability.(AU)

[Translated article] Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate.

INTRODUCTION: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. MATERIAL AND METHODS: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46-93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). RESULTS: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. CONCLUSIONS: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.

Significant improvement in axial load stability with the pre-tensioned pelvic external fixator: A biomechanical analysis in a model with type C Tile lesion. / Mejora significativa de la estabilidad a carga axial con el fijador externo pélvico pretensado: análisis biomecánico en un modelo con lesión Tile tipo C.

OBJECTIVE: The aim of our work is to check if the use of a pre-tensed bar connected to 2supra-acetabular Schanz pins is more stable in a pelvic with a tile C1 injury. MATERIAL AND METHODS: We used synthetic pelvis (N=5) with a unstable vertical injury, stabilized with both the standard and the pre-tensed system. They both were submitted to axial loading. We measured applied forces and the position of markers that were positioned in the sacroiliac and symphysis joints. We determined the relative movements between injured surfaces, rigidity, resistance and when each system failed. RESULTS: When using the pre-tensed fixator, the rigidity was much higher in the sacro-iliac joint (P=.043) being 3.45 times higher, being also 2.06 times higher in pubic symphysis (P=.043). The resistance against failure was 2 times higher too (P=.043). DISCUSSION: The increased axial stability with the pre-tensed external fixator accords with its ability to make active compression in both posterior and anterior elements of the pelvic ring, which was previously demonstrated. This result supports the preliminary clinic outcomes that were obtained. CONCLUSIONS: The pre-tensed external fixator increases the axial stability of the pelvic ring's posterior elements in a synthethic pelvis with a Tile C1 injury, without decreasing it's capacity to achieve an anterior stability.

[Translated article] Significant improvement in axial load stability with the pre-tensioned pelvic external fixator: A biomechanical analysis in a model with type C Tile lesion.

OBJECTIVE: The aim of our work is to check if the use of a pre-tensed bar connected to 2 supra-acetabular Schanz pins is more stable in a pelvic with a tile C1 injury. MATERIAL AND METHODS: We used synthetic pelvis (N = 5) with a unstable vertical injury, stabilized with both the standard and the pre-tensed system. They both were submitted to axial loading. We measured applied forces and the position of markers that were positioned in the sacroiliac and symphysis joints. We determined the relative movements between injured surfaces, rigidity, resistance and when each system failed. RESULTS: When using the pre-tensed fixator, the rigidity was much higher in the sacro-iliac joint(P=.043) being 3.45 times higher, being also 2.06 times higher in pubic symphysis (P=.043). The resistance against failure was 2 times higher too (P=.043). DISCUSSION: The increased axial stability with the pre-tensed external fixator accords with its ability to make active compression in both posterior and anterior elements of the pelvic ring, which was previously demonstrated. This result supports the preliminary clinic outcomes that were obtained. CONCLUSIONS: The pre-tensed external fixator increases the axial stability of the pelvic ring's posterior elements in a synthethic pelvis with a Tile C1 injury, without decreasing it's capacity to achieve an anterior stability.

Comparative biomechanical study of two configurations of cemented screws in a simulated proximal humerus fracture fixed with locking plate. / Estudio biomecánico comparativo de dos configuraciones de tornillos cementados en una fractura simulada de húmero proximal fijada con placa y tornillos bloqueados.

INTRODUCTION: Screw tip augmentation with bone cement for fixation of osteoporotic proximal humerus fractures seems to improve stability and to decrease the rate of complications related to implant failure. However, the optimal augmentation combinations are unknown. The aim of this study was to assess the relative stability of two augmentations combinations under axial compression load in a simulated proximal humerus fractures fixed with locking plate. MATERIAL AND METHODS: A surgical neck osteotomy was created in five pairs of embalmed humeri with a mean age of 74 years (range 46-93 years), secured with a stainless-steel locking-compression plate. In each pair of humeri, on the right humerus were cemented the screws A and E, and in the contralateral side were cemented screws B and D of the locking plate. The specimens were first tested cyclically in axial compression for 6,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cycling test, the specimens were loaded in compression force simulating varus bending with increasing load magnitude until failure of the construct (static study). RESULTS: There were no significant differences in interfragmentary motion between the two configurations of cemented screws in the dynamic study (p=0.463). When tested to failure, the configuration of cemented screws in lines B and D demonstrated higher compression load to failure (2218N vs. 2105, p=0.901) and higher stiffness (125N/mm vs. 106N/mm, p=0.672). However, no statistically significant differences were reported in any of these variables. CONCLUSIONS: In simulated proximal humerus fractures, the configuration of the cemented screws does not influence the implant stability when a low-energy cyclical load is applied. Cementing the screws in rows B and D provides similar strength to the previously proposed cemented screws configuration and could avoid complications observed in clinical studies.

Stabilizing effects of a particulate demineralized bone matrix in the L4 interbody space with and without PEEK Cage: a literature review and preliminary results of a cadaveric biomechanical study / Estabilización de los efectos de una matriz osea desmineralizada Particulada en el espacio intersomático a nivel L4 con o sin cajetín PEEK: revisión de la literatura y resultados preliminares de un estudio biomecánico cadavérico

We reviewed the biological elements supporting the usefulness of a specifically designed particulate form of demineralized bone matrix (DBM) in spinal fusion, and report some limitations of its use described in the medical literature and in the interbody space using a cadaveric biomechanical model. A literature review and description of the techniques used to augment spinal fusion are presented, including a more thorough review of recent findings of cadaveric biomechanical flexibility studies using DBM alone at different percentage fills of the existing disc space and DBM with a polyetheretherketone (PEEK) interbody cage. The need for DBM was established by reviewing limitations of autografts and allografts in spinal fusion. Demineralized bone matrix used alone did not increase stability post discectomy at L4-L5, but was demonstrated to exhibit satisfactory stability when used with a PEEK interbody cage. There may be a future role for DBM that hardens and fills disc space more rigidly, overcoming this limitation to its use.

Examinamos los elementos biológicos que respaldan la utilidad de una forma particulada específicamente diseñada de matriz ósea desmineralizada (MOD) con fusión espinal. Asimismo reportamos algunas limitaciones de su uso en el espacio intersomático descritas en la literatura médica, mediante un modelo biomecánico cadavérico. Se presenta una revisión de la literatura, acompañada de una descripción de las técnicas utilizadas para aumentar la fusión espinal, incluyendo una revisión más exhaustiva de los hallazgos recientes de los estudios de flexibilidad biomecánico cadavérica, utilizando sólo MOD en diferentes rellenos de porcentajes del espacio discal existente, y MOD con cajetines intervertebrales de polieteretercetona (PEEK). La necesidad de MOD se estableció examinando las limitaciones de los autoinjertos y los aloinjertos en la fusión espinal. El uso de la matriz ósea desmineralizada sola, no aumentaba la estabilidad post-disectómica a nivel L4-L5, pero se demostró que presentaba una estabilidad satisfactoria cuando se utilizaba con un cajetín intervertebral PEEK. Puede haber un papel futuro para un MOD que se endurezca y rellene el espacio del disco más rígidamente, venciendo así esta limitación a su uso.