Causas de ingresos no deseados tras la realización de procedimientos quirúrgicos de cirugía ortopédica y traumatología en cirugía mayor ambulatoria / Causes of unplanned admission after orthopedic procedures in ambulatory surgery

OBJETIVO: Los procedimientos de cirugía ortopédica y traumatología realizados en unidades de cirugía mayor ambulatoria ofrecen importantes ventajas que desaparecen cuando la recuperación postoperatoria no es la esperada y los pacientes precisan ingresar. El objetivo de este estudio es analizar las causas de ingresos no deseados tras intervenciones quirúrgicas de cirugía ortopédica y traumatología en una unidad de cirugía mayor ambulatoria en relación con variables como edad, riesgo anestésico, tipo de anestesia, procedimiento o duración. MÉTODOS: Estudio de cohorte ambispectivo sobre 5.085 pacientes intervenidos desde 1995 a 2017. Se analizaron 39 variables proporcionadas por la base de datos de la unidad que se abre al ingreso en la misma y se cierra el día 30 postoperatorio. RESULTADOS: El 98,2% de los pacientes fueron dados de alta de la unidad. Precisaron ingresar 74 (1,5%). Este porcentaje demostró diferencias significativas en relación con el tipo de procedimiento, el tipo de anestesia y la duración, que condicionaron el ingreso inmediato por mal control del dolor agudo postoperatorio, náuseas o alteraciones de la herida. Diecisiete pacientes (0,3%) precisaron un ingreso diferido por complicaciones surgidas en el domicilio, siendo la más frecuente la infección de la herida. CONCLUSIONES: Los ingresos no deseados se relacionan con mayor frecuencia con el empleo de anestesia general, con operaciones de mayor duración y con procedimientos como la cirugía artroscópica, las correcciones de hallux valgus o las retiradas de material de osteosíntesis, siendo las causas de ingreso más importantes el mal control del dolor agudo postoperatorio en los inmediatos y la infección de la herida en los diferidos

OBJECTIVE: Orthopaedic procedures performed in Day Surgery Units provide important advantages which disappear when patients require admission when postoperative recovery is not as expected. The aim of this study was to analyse the reasons for unplanned hospital admissions after orthopaedic procedures in a Day Surgery Unit and their relationship between variables such as patient age, anaesthetic risk and technique, procedure or duration. METHODS: Ambispective cohort study of 5,085 patients who underwent surgical orthopaedic procedures between 1995 and 2017. Thirty-nine variables provided by the Unit's database were analysed. The database was opened on the day of admission and closed the 30th postoperative day. RESULTS: Of the patients, 98.2% were discharged from the Unit. Seventy-four (1.5%) required overnight admission. This percentage showed significant differences in relation to the type of procedure, type of anaesthesia and duration, which conditioned overnight admission due to inadequate postoperative pain management, nausea or wound complications. Seventeen patients (0.3%) required readmission after discharge due to complications that arose at home, such as wound infection, which was the most common. CONCLUSIONS: Unplanned admissions are more frequently related to general anaesthesia, lengthy surgeries and procedures such as arthroscopy, hallux valgus corrections or removal of osteosynthesis material. The major reasons for unplanned admissions were inadequate postoperative pain management for overnight admissions and wound infection for admissions after discharge

Causes of unplanned admission after orthopedic procedures in ambulatory surgery. / Causas de ingresos no deseados tras la realización de procedimientos quirúrgicos de cirugía ortopédica y traumatología en cirugía mayor ambulatoria.

OBJECTIVE: Orthopaedic procedures performed in Day Surgery Units provide important advantages which disappear when patients require admission when postoperative recovery is not as expected. The aim of this study was to analyse the reasons for unplanned hospital admissions after orthopaedic procedures in a Day Surgery Unit and their relationship between variables such as patient age, anaesthetic risk and technique, procedure or duration. METHODS: Ambispective cohort study of 5,085 patients who underwent surgical orthopaedic procedures between 1995 and 2017. Thirty-nine variables provided by the Unit's database were analysed. The database was opened on the day of admission and closed the 30th postoperative day. RESULTS: Of the patients, 98.2% were discharged from the Unit. Seventy-four (1.5%) required overnight admission. This percentage showed significant differences in relation to the type of procedure, type of anaesthesia and duration, which conditioned overnight admission due to inadequate postoperative pain management, nausea or wound complications. Seventeen patients (0.3%) required readmission after discharge due to complications that arose at home, such as wound infection, which was the most common. CONCLUSIONS: Unplanned admissions are more frequently related to general anaesthesia, lengthy surgeries and procedures such as arthroscopy, hallux valgus corrections or removal of osteosynthesis material. The major reasons for unplanned admissions were inadequate postoperative pain management for overnight admissions and wound infection for admissions after discharge.

Anillo de Burch-Schneider asociado a injerto óseo triturado, supervivencia y resultados clínicos en revisión acetabular / Burch-Schneider ring associated with morselized bone allografts, survival and clinical outcomes after acetabular revision surgery

Introducción y objetivos: La cirugía de revisión acetabular supone un reto por la aparición de defectos óseos que dificultan la fijación primaria de los implantes al extraer los componentes aflojados. Los anillos antiprotrusivos, como el de Burch-Schneider (BS) se han mostrado como aliados en defectos moderados o severos. El objetivo del estudio es evaluar resultados y supervivencia de este tipo de implantes en recambios acetabulares a medio plazo. Material y métodos: Estudio retrospectivo sobre una cohorte de 64 pacientes (67 recambios) con anillo de BS asociado a injerto triturado con un seguimiento mínimo de 2 años. Se recogen los datos relativos a resultados clínicos, incorporación de injertos, movilización de los implantes, supervivencia y complicaciones. Resultados: El seguimiento medio fue de 5,06 años (R=2,2-12). La escala de Merlé pasó de una mediana de 8 puntos a una mediana de 15 puntos al final del seguimiento (p<0,0001), con un 76,11% de resultados buenos o excelentes. La reproducción del centro de rotación anatómico se asoció con un mejor resultado (p<0,05). Se produjo incorporación total o subtotal de los injertos en el 97% de los pacientes, aunque esto no impidió una migración significativa del anillo según criterios de Gill en 6 casos. Se constató una supervivencia global del implante para cualquier causa del 93,4% a 5 años y del 84,6% a 10 años. Conclusiones: El anillo de BS presenta buenos resultados a medio y largo plazo permitiendo una reconstrucción anatómica en cirugía de revisión, además de permitir una reposición del stock óseo, estos resultados además son comparables y mejoran ampliamente a otros anillos

Introduction and objectives: Acetabular revision surgery is a challenge due to the appearance of bone defects that make primary fixation of implants difficult when extracting loosened components. Reinforcement rings, such as Burch-Schneider (BS), have been shown to be allies in moderate or severe bone defects. The objective of the study is to evaluate the results and survival of these types of implants in acetabular revision surgery in the medium follow-up. Material and methods: Retrospective study on a cohort of 64 patients (67 replacements) with BS rings associated with morselized bone allografts in a 2 years minimum follow-up. Data were collected regarding clinical outcomes, graft incorporation, implant mobilization, survival and complications. Results: The mean follow-up was 5.06 years (R=2.2-12). The Merle scale improved from 8 points to 15 points at the end of follow-up (P<.0001) with 76.11% of good or excellent results. Reproduction of the anatomical centre of rotation was associated with a better result (P<.05). There was total or subtotal incorporation of the bone allograft in 97% of the patients, although this did not prevent a significant migration of the ring according to Gill criteria in 6 cases. We observed an overall survival of the implant for any cause of 93.4% at 5 years, and 84.6% at 10 years. Conclusions: The BS reinforcement ring shows good results in the medium and long term enabling anatomical reconstruction in revision surgery as well as replacement of the bone stock. These results are also comparable and are a vast improvement on other rings

Burch-Schneider ring associated with morselized bone allografts, survival and clinical outcomes after acetabular revision surgery. / Anillo de Burch-Schneider asociado a injerto óseo triturado, supervivencia y resultados clínicos en revisión acetabular.

INTRODUCTION AND OBJECTIVES: Acetabular revision surgery is a challenge due to the appearance of bone defects that make primary fixation of implants difficult when extracting loosened components. Reinforcement rings, such as Burch-Schneider (BS), have been shown to be allies in moderate or severe bone defects. The objective of the study is to evaluate the results and survival of these types of implants in acetabular revision surgery in the medium follow-up. MATERIAL AND METHODS: Retrospective study on a cohort of 64 patients (67 replacements) with BS rings associated with morselized bone allografts in a 2 years minimum follow-up. Data were collected regarding clinical outcomes, graft incorporation, implant mobilization, survival and complications. RESULTS: The mean follow-up was 5.06 years (R=2.2-12). The Merle scale improved from 8 points to 15 points at the end of follow-up (P<.0001) with 76.11% of good or excellent results. Reproduction of the anatomical centre of rotation was associated with a better result (P<.05). There was total or subtotal incorporation of the bone allograft in 97% of the patients, although this did not prevent a significant migration of the ring according to Gill criteria in 6 cases. We observed an overall survival of the implant for any cause of 93.4% at 5 years, and 84.6% at 10 years. CONCLUSIONS: The BS reinforcement ring shows good results in the medium and long term enabling anatomical reconstruction in revision surgery as well as replacement of the bone stock. These results are also comparable and are a vast improvement on other rings.

La importancia de la restauración de la línea articular en la revisión de la artroplastía total de rodilla. Índices funcionales, calidad de vida y supervivencia / The importance of the restoration of the joint line in revision total knee arthroplasty. Clinical indexes, quality of life and survival

Resumen: Introducción: La reproducción de la correcta línea articular podría ser un buen índice para la obtención de resultados satisfactorios en la cirugía protésica de rodilla, aunque en la cirugía de revisión no se ha estudiado ampliamente. Es necesaria la búsqueda de un método sencillo y reproducible para evaluar esos resultados. Material y métodos: Se realizó un estudio retrospectivo entre Enero del 2000 y Diciembre del 2013. Se implantaron 97 artroplastías totales de revisión de rodilla. El grupo de estudio lo conformaron 67 pacientes. Para la realización de nuestro trabajo se evaluó la línea articular según el método descrito por Hofmann A. La evaluación de los resultados clínicos incluyó las siguientes variables primarias: flexión, extensión, rango de movimiento, WOMAC, SF-36, KSS (Knee Society Score) y KSS funcional. Se estudió la supervivencia de las artroplastías. Resultados: Las variables de flexión, extensión y rango de movimiento postoperatorio se correlacionaron estadísticamente con esta medición. El KSS se relacionó estadísticamente en su vertiente articular con la restauración de la línea articular. Para el resto de escalas, SF-36 y WOMAC, las puntuaciones fueron más altas pero no se correlacionó con la significación aceptada. Conclusión: Ante estos resultados podemos afirmar que la restauración de la correcta línea articular mejora los resultados clínicos de la cirugía de revisión de rodilla.

Abstract: Introduction: The reproduction of the anatomical joint line could be a good index to obtain good results in knee prosthesis surgery, although in revision surgery has not been enough studied. A search for a simple and reproducible method is needed to review these results. Material and methods: A retrospective study was conducted between January 2000 and December 2013. A total of 97 total revision knee arthroplasties were implanted. Finally, the study group consisted of 67 patients. To perform our study, the joint line was evaluated according to the method described by Hofmann A. The evaluation of the clinical results included the following main variables: Flexion, extension, range of motion, WOMAC, SF-36, KSS (Knee Society Score) and functional KSS. The survival of the arthroplasties was studied. (p = 0.05). Results: The variables of flexion, extension and range of postoperative movement are statistically correlated with this measure. The KSS was statistically related in its joint aspect with the restoration of the joint line. For the other scales, SF-36 and WOMAC, the figures were higher but did not correlate with the accepted p. Conclusion: In view of these results, we can say that the restoration of the anatomical joint line improves the clinical results of revision total knee arthroplasty.

[The importance of the restoration of the joint line in revision total knee arthroplasty. Clinical indexes, quality of life and survival]. / La importancia de la restauración de la línea articular en la revisión de la artroplastía total de rodilla. Índices funcionales, calidad de vida y supervivencia.

INTRODUCTION: The reproduction of the anatomical joint line could be a good index to obtain good results in knee prosthesis surgery, although in revision surgery has not been enough studied. A search for a simple and reproducible method is needed to review these results. MATERIAL AND METHODS: A retrospective study was conducted between January 2000 and December 2013. A total of 97 total revision knee arthroplasties were implanted. Finally, the study group consisted of 67 patients. To perform our study, the joint line was evaluated according to the method described by Hofmann A. The evaluation of the clinical results included the following main variables: Flexion, extension, range of motion, WOMAC, SF-36, KSS (Knee Society Score) and functional KSS. The survival of the arthroplasties was studied. (p = 0.05). RESULTS: The variables of flexion, extension and range of postoperative movement are statistically correlated with this measure. The KSS was statistically related in its joint aspect with the restoration of the joint line. For the other scales, SF-36 and WOMAC, the figures were higher but did not correlate with the accepted p. CONCLUSION: In view of these results, we can say that the restoration of the anatomical joint line improves the clinical results of revision total knee arthroplasty.

INTRODUCCIÓN: La reproducción de la correcta línea articular podría ser un buen índice para la obtención de resultados satisfactorios en la cirugía protésica de rodilla, aunque en la cirugía de revisión no se ha estudiado ampliamente. Es necesaria la búsqueda de un método sencillo y reproducible para evaluar esos resultados. MATERIAL Y MÉTODOS: Se realizó un estudio retrospectivo entre Enero del 2000 y Diciembre del 2013. Se implantaron 97 artroplastías totales de revisión de rodilla. El grupo de estudio lo conformaron 67 pacientes. Para la realización de nuestro trabajo se evaluó la línea articular según el método descrito por Hofmann A. La evaluación de los resultados clínicos incluyó las siguientes variables primarias: flexión, extensión, rango de movimiento, WOMAC, SF-36, KSS (Knee Society Score) y KSS funcional. Se estudió la supervivencia de las artroplastías. RESULTADOS: Las variables de flexión, extensión y rango de movimiento postoperatorio se correlacionaron estadísticamente con esta medición. El KSS se relacionó estadísticamente en su vertiente articular con la restauración de la línea articular. Para el resto de escalas, SF-36 y WOMAC, las puntuaciones fueron más altas pero no se correlacionó con la significación aceptada. CONCLUSIÓN: Ante estos resultados podemos afirmar que la restauración de la correcta línea articular mejora los resultados clínicos de la cirugía de revisión de rodilla.

Estudio biomecánico de la tibia en el recambio de una artroplastia de rodilla / Biomechanical study of the tibia in knee replacement revision

No hay consenso en el tratamiento de elección de los recambios protésicos de rodilla con defectos óseos severos. Las opciones son variadas, cada una con sus ventajas e inconvenientes. Los trabajos clínicos publicados tienen sus limitaciones en cuanto al número de pacientes y el poco seguimiento clínico. Se presenta un trabajo biomecánico con elementos finitos comparativo de 5 diseños de implantes tibiales: vástago recto, con offset con/sin suplemento y vainas con/sin vástago, para poder analizar el comportamiento tanto del hueso tibial como del material a lo largo del tiempo. Dentro de las limitaciones que presenta un modelo matemático hemos podido ver que los implantes con vástago recto producen el mayor valor de reabsorción ósea alrededor del vástago, mientras que la menor reabsorción ósea tiene lugar en el hueso de la diáfisis proximal. Las vainas metafisarias tibiales sin vástago producen una menor reabsorción ósea que el resto en el canal medular (AU)

The best management of severe bone defects following total knee replacement is still controversial. Metal augments, tantalum cones and porous tibial sleeves could help the surgeon to manage any type of bone loss, providing a stable and durable knee joint reconstruction. Five different types of prostheses have been analysed: one prosthesis with straight stem; two prostheses with offset stem, with and without supplement, and two prostheses with sleeves, with and without stem. The purpose of this study is to report a finite element study of revision knee tibial implants. The main objective was to analyse the tibial bone density changes and Von Misses tension changes following different tibial implant designs. In all cases, the bone density decreases in the proximal epiphysis and medullary channels, with a bone density increase also being predicted in the diaphysis and at the bone around the stems tips. The highest value of Von Misses stress has been obtained for the straight tibial stem, and the lowest for the stemless metaphyseal sleeves prosthesis (AU)

Inestabilidad de la artroplastia total de cadera: estudio clínico y computacional de sus factores de riesgo / Instability of total hip replacement: a clinical study and determination of its risk factors

Objetivos. Determinar los factores de riesgo asociados a la luxación protésica y simular un modelo mediante elementos finitos que determine los arcos de movimiento seguros en cada angulación y anteversión del cotilo. Material y métodos. Casos-control retrospectivo con 46 pacientes luxados desde 1994 hasta 2011. Grupo control: 83 pacientes elegidos de forma aleatoria. Se recogieron los factores de riesgo de luxación descritos en la literatura. Se simuló un modelo protésico mediante elementos finitos con cabezas de 28, 32, 36 mm y cotilo de 52 mm. Posición acetabular de 25°, 40° y 60° de inclinación y 0°, 15° y 25° de anteversión. Para cada combinación se estudió la flexión de 90° y la extensión de 0° aplicando rotación interna y externa midiendo el rango de movimiento y el momento resistente hasta el choque-luxación y la distribución de tensiones en la superficie del cotilo. Resultados. Mayor edad en luxados (p = 0,002). Mayor luxación en fracturas respecto artrosis (p < 0,001). Menor anteversión en luxados (p = 0,043). Mayor longitud de cuello femoral en luxados (p = 0,002). Simulación de finitos: menor luxación cuanto mayor inclinación, anteversión y diámetro de cabeza femoral. Discusión-conclusiones. La edad avanzada y la fractura son los principales factores favorecedores de la luxación. El área de seguridad libre de luxación comprende 40°-60° de inclinación y 15°-25° de anteversión. Tanto el defecto como el exceso de tensión de las partes blandas predisponen a la luxación. Las cabezas de mayor tamaño son más estables (AU)

Objectives. To determine the risk factors associated with prosthetic dislocation and simulate a finite element model to determine the safe range of movement of various inclination and anteversion cup positions. Material and methods. Retrospective Case Control study with 46 dislocated patients from 1994 to 2011. Control Group: 83 randomly selected patients. Dislocation risk factors described in the literature were collected. A prosthetic model was simulated using finite elements with 28, 32, 36 mm heads, and a 52 mm cup. Acetabular position was 25°, 40°, and 60° tilt and with 0°, 15° and 25° anteversion. In extension of 0° and flexion of 90°, internal and external rotation was applied to analyze the range of movement, maximum resisting moment, and stress distribution in the acetabulum to impingement and dislocation. Results. There was greater dislocation in older patients (p = 0 .002). Higher dislocation in fractures than in osteoarthritis (p = 0 .001). Less anteversion in dislocated patients (p = 0 .043). Longer femoral neck in dislocated patients (p = 0 .002). Finite element model: lower dislocation when there is more anteversion, tilt and bigger femoral heads. Discussion-conclusions. Advanced age and fractures are the major risk factors for dislocation. “Safe zone” of movement for dislocation avoidance is 40°-60° tilt and 15°-25° anteversion. Both the defect and excess of soft tissue tension predispose to dislocation. Bigger femoral heads are more stable (AU)

Biomechanical study of the tibia in knee replacement revision.

The best management of severe bone defects following total knee replacement is still controversial. Metal augments, tantalum cones and porous tibial sleeves could help the surgeon to manage any type of bone loss, providing a stable and durable knee joint reconstruction. Five different types of prostheses have been analysed: one prosthesis with straight stem; two prostheses with offset stem, with and without supplement, and two prostheses with sleeves, with and without stem. The purpose of this study is to report a finite element study of revision knee tibial implants. The main objective was to analyse the tibial bone density changes and Von Misses tension changes following different tibial implant designs. In all cases, the bone density decreases in the proximal epiphysis and medullary channels, with a bone density increase also being predicted in the diaphysis and at the bone around the stems tips. The highest value of Von Misses stress has been obtained for the straight tibial stem, and the lowest for the stemless metaphyseal sleeves prosthesis.

Instability of total hip replacement: A clinical study and determination of its risk factors.

OBJECTIVES: To determine the risk factors associated with prosthetic dislocation and simulate a finite element model to determine the safe range of movement of various inclination and anteversion cup positions. MATERIAL AND METHODS: Retrospective Case Control study with 46 dislocated patients from 1994 to 2011. CONTROL GROUP: 83 randomly selected patients. Dislocation risk factors described in the literature were collected. A prosthetic model was simulated using finite elements with 28, 32, 36 mm heads, and a 52 mm cup. Acetabular position was 25°, 40°, and 60° tilt and with 0°, 15° and 25° anteversion. In extension of 0° and flexion of 90°, internal and external rotation was applied to analyze the range of movement, maximum resisting moment, and stress distribution in the acetabulum to impingement and dislocation. RESULTS: There was greater dislocation in older patients (p=0.002). Higher dislocation in fractures than in osteoarthritis (p=0.001). Less anteversion in dislocated patients (p=0.043). Longer femoral neck in dislocated patients (p=0.002). Finite element model: lower dislocation when there is more anteversion, tilt and bigger femoral heads. DISCUSSION-CONCLUSIONS: Advanced age and fractures are the major risk factors for dislocation. "Safe zone" of movement for dislocation avoidance is 40°-60° tilt and 15°-25° anteversion. Both the defect and excess of soft tissue tension predispose to dislocation. Bigger femoral heads are more stable.

[Cost-effectiveness of a hallux valgus day-surgery program]. / Coste-efectividad del proceso hallux valgus en cirugía mayor ambulatoria.

INTRODUCTION: The development of one-day surgery units has shown to be a better use of health resources without reducing quality. The objective of this study was to evaluate the effectiveness and quality criteria of ambulatory surgery program in the Hallux valgus process. MATERIAL AND METHODS: A retrospective study was conducted on a sample of 753 patients who underwent a Hallux valgus process at our institution between 2002 and 2012 (292 in ambulatory surgery cohort and 461 in hospitalization group). The cost-process was evaluated using the Weighted Care Unitas a measuring unit. Secondary data were collected as regards discharge criteria and patient satisfaction. RESULTS: A significant difference was found between Weighted Care Unit spending on in-patient surgery and out-patient surgery. Both samples were comparable and no differences were found between diagnosis and intervention. The admission rate after ambulatory surgery was 2.39%, and the substitution index increased to 56.04%. The ambulatory surgery program was given a satisfaction rating of 84.6 out of 100. CONCLUSIONS: The results of our study indicate that it is possible to maximize the substitution index of the Hallux valgus process leading to a better use of resources and a high degree of patient satisfaction.

Coste-efectividad del proceso hallux valgus en cirugía mayor ambulatoria / Cost-effectiveness of a hallux valgus day-surgery program

Introducción. El desarrollo de las unidades de cirugía mayor ambulatoria ha puesto de manifiesto una mejor utilización de los recursos sanitarios sin mermar la calidad de los mismos. El objetivo del trabajo es valorar la eficacia del programa de cirugía mayor ambulatoria en el proceso Hallux valgus y sus criterios de calidad. Material y métodos. Se analizan retrospectivamente todos los pacientes intervenidos del proceso Hallux valgus en nuestro centro entre de 2002 y 2012 obteniendo una muestra de 753 pacientes (292 en el grupo de cirugía mayor ambulatoria y 461 en el grupo de hospitalización). Se recogen los datos relativos al paciente y los datos relativos al coste, proceso utilizando como unidad de medida la unidad ponderada asistencial. Secundariamente se recogieron los datos en cuanto a los criterios de alta y satisfacción de los pacientes. Resultados. Se encontró una diferencia muy significativa entre el gasto en la unidad ponderada asistencial de pacientes hospitalizados y los que se intervinieron en cirugía mayor ambulatoria. Ambas muestras eran comparables y no se encontraron diferencias demográficas ni de tipos de intervención. El índice de ingreso poscirugía mayor ambulatoria fue de 2,39% y el de sustitución creció hasta el 56,04%. Se obtuvo un índice de satisfacción de 84,6 puntos sobre 100 en el programa de cirugía ambulatoria. Conclusiones. Los resultados de nuestro estudio indican que es posible incrementar al máximo el índice de sustitución del proceso Hallux valgus consiguiendo una mejor utilización de los recursos y con un alto grado de satisfacción de los pacientes (AU)

Introduction. The development of one-day surgery units has shown to be a better use of health resources without reducing quality. The objective of this study was to evaluate the effectiveness and quality criteria of ambulatory surgery program in the Hallux valgus process. Material and methods. A retrospective study was conducted on a sample of 753 patients who underwent a Hallux valgus process at our institution between 2002 and 2012 (292 in ambulatory surgery cohort and 461 in hospitalization group). The cost-process was evaluated using the Weighted Care Unitas a measuring unit. Secondary data were collected as regards discharge criteria and patient satisfaction. Results. A significant difference was found between Weighted Care Unit spending on in-patient surgery and out-patient surgery. Both samples were comparable and no differences were found between diagnosis and intervention. The admission rate after ambulatory surgery was 2.39%, and the substitution index increased to 56.04%. The ambulatory surgery program was given a satisfaction rating of 84.6 out of 100. Conclusions. The results of our study indicate that it is possible to maximize the substitution index of the Hallux valgus process leading to a better use of resources and a high degree of patient satisfaction (AU)

A finite element analysis of the vibration behaviour of a cementless hip system.

An early diagnosis of aseptic loosening of a total hip replacement (THR) by plain radiography, scintigraphy or arthography has been shown to be less reliable than using a vibration technique. However, it has been suggested that it may be possible to distinguish between a secure and a loose prosthesis using a vibration technique. In fact, vibration analysis methods have been successfully used to assess dental implant stability, to monitor fracture healing and to measure bone mechanical properties. Several studies have combined the vibration technique with the finite element (FE) method in order to better understand the events involved in the experimental technique. In the present study, the main goal is to simulate the change in the resonance frequency during the osseointegration process of a cementless THR (Zweymüller). The FE method was used and a numerical modal analysis was conducted to obtain the natural frequencies and mode shapes under vibration. The effects were studied of different bone and stem material properties, and different contact conditions at the bone-implant interface. The results were in agreement with previous experimental and computational observations, and differences among the different cases studied were detected. As the osseointegration process at the bone-implant interface evolved, the resonance frequency values of the femur-prosthesis system also increased. In summary, vibration analysis combined with the FE method was able to detect different boundary conditions at the bone-implant interface in cases of both osseointegration and loosening.

Estudio del polietileno en artroplastia total de rodilla / No disponible

No disponible

Navigation in total knee arthroplasty. A multicenter study.

We carried out a multicentre study to compare the postoperative femorotibial radiographic axis in two total knee replacement groups; one using manual instrumentation and the other using navigation. In the latter group, three navigation systems were used: Stryker, Orthopilot and Navitrack. The prior circumstances of patients in terms of age, weight, aetiology, epicondylar perimeter, patellar tendon length and knee deformity was similar in both groups. The duration of the operation was longer in the group with navigation (16.7 min). A normal femorotibial axis was more frequently obtained in the group with a navigator compared to the manual group (48.1% and 30%, respectively). A varus axis was most common in the manual group (42.2 and 26.9%, respectively). When we analysed the final postoperative radiographic axis, taking 180 degrees to be a normal result, we noted that cases where manual instrumentation was used deviated by 1.19 degrees more than those carried out with navigation, with this difference being statistically significant (P<0.001). No significant differences were found in the final angle of the extremity with the different navigation systems. The navigation systems used in this study improve the frontal angle of the arthroplasty.

Modelo de interfaz cemento-vástago en artroplastias totales de cadera. Estudio de la superficie con elementos finitos / Cement-femoral stem interface model in total hip prosthesis: study of the surface with finite element

Introducción. La separación entre el cemento y el implante femoral se relaciona con los aflojamientos asépticos y con la supervivencia de los implantes. El objetivo del trabajo es el desarrollo de un modelo de daño que simule la degradación del cemento y el aflojamiento del implante, con dos acabados superficiales del vástago. Material y método. Aplicamos un modelo axisimétrico de elementos finitos de un vástago rodeado por una capa de cemento. La carga de compresión aplicada al vástago varía de 0 a 7 kN con frecuencia de 1 Hz durante 1,7 millones de ciclos. Una vez que se soltó la interfaz se incorporó rozamiento entre ambas superficies. Resultados. En los vástagos lisos el daño estimado en el cemento estaba más distribuido, siendo el daño global menor. En los rugosos hay mayor concentración del daño y mayor degradación del cemento en la zona distal, continuándose por la zona proximal. Conclusión. La simulación con elementos finitos permite predecir el comportamiento de los implantes relacionando macrogeometría y superficie. En nuestro modelo se demuestra la influencia del acabado superficial del vástago en la localización e intensidad del daño en el cemento y en la interfaz (AU)

Introduction. Debonding of the stem-cement interface is one of the most important causes aseptic loosening of the femoral stem, and it is related with the implant survival. The main goal of this study is the development of a damage model, in order to simulate the cement degradation and the debonding process of the stem-cement interface, respectively. We would consider two different surfaced finishing of the stem. Materials and methods. An axisymetric finite element model of a stem and the surrounding cement mantle was developed. The cement damage model was also implemented to simulate its degradation. The stem was gradually compressed in the cement by a dynamic, sinusoidal axial force, cycling between 0 and 7 kN for 1.7 million cycles at a frequency of 1 Hz. When the interface is completely debonded, contact friction is incorporated between both surfaces. Results. Subsidence is higher in the polished stems because the stem-cement interface is completely debonded. Cement damage in the polished stem is more distributed and quantitatively is lower than for the rough stems, where cement damage is more concentrated distally. Conclusion. Finite element models are able to predict the behaviour of implants relating the stem geometry with its surface finished. The influence of the surface finished on the cement damage and debonding process of the stem-cement interface have been demonstrated with the model proposed (AU)

Osteosíntesis de fracturas del fémur distal con placas LISS / Distal femoral fractures; treatment with less invasive stabilitation system (L. I. S. S.)

Las fracturas del fémur distal son complejas en su tratamiento y asocian múltiples complicaciones evolutivas com pseudoartrosis, callos viciosos, gonartrosis o infección secundaria a cirugía abierta agresiva, por lo que han surgido las osteosíntesis mínimamente invasivas dentro de las cuales se sitúa la placa LISS. Analizamos los resultados tras 10 meses de seguimiento de 14 pacientes con fractura del fémur distal tratados con placa LISS. Los tiempos de consolidación no fueron muy divergentes respecto a series mayores, la incidencia de retrasos de consolidación y callos viciosos, baja. No hubo pseudoartrosis, fracasos del material, aflojamientos, infecciones, tromboembolismos ni algodistrofias. Por ello, consideramos que los resultados obtenidos con este implante son satisfactorios

The treatment of the distal femoral fractures is difficult in order to the surgery and múltiple complications, like pseudoartrosis,c allus vicious, gonartrosis or infection because open surgery. So that it has arised the minimun invasive system of osteosynthesis like LISS plate. We have assessed outcomes in 14 patients with distal femoral fractures treated with that implant. The mean follow up was 10 months. The times of consolidation was similar than other bigger series of patients and low incidence of delayed consolidation and callus vicious. There has not been any case of pseudoartrosis, failure of implant, loosenin, infections, tromboembolism or algodystrophia, so that considered that we has obtained good results

Simulación en 3D con elementos finitos de un modelo de prótesis de rodilla / Three-dimensional finite-elements simulation of a model of knee prosthesis

El análisis mediante elementos finitos (AEF) viene aplicándose en la bibliografía al estudio biomecánico de las prótesis de rodilla. Material y método. En nuestro trabajo hemos realizado un modelo de articulación de rodilla y otro de artroplastia de rodilla mediante AEF, estudiando el efecto de las cargas sobre ambos modelos en la fase de soporte unilateral a 0º y 15º de flexión. Se han comparado los desplazamientos, las tensiones en dirección vertical para el tejido óseo y las tensiones de Von Mises para los implantes protésicos. Resultados. En extensión los desplazamientos obtenidos con la rodilla anatómica son mayores que con artroplastia. En la rodilla con artroplastia se produce una mayor concentración de tensiones a nivel de la cabeza femoral, mientras que en el modelo de rodilla anatómica la distribución es más uniforme. El componente tibial es el que más trabaja, sobre todo en la zona del vástago pero también en la bandeja metálica. Conclusiones. A pesar de las limitaciones del modelo, podemos afirmar que el AEF permite realizar un estudio biomecánico del comportamiento estructural de la articulación de la rodilla y la rodilla con artroplastia. (AU)