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)

[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.

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.