Analysis of the main passive soft tissues associated with adult acquired flatfoot deformity development: A computational modeling approach

Adult acquired flatfoot deformity (AAFD) is a pathology with a wide range of treatment options. Physicians decide the best treatment based on their experience, so the process is entirely subjective. A better understanding of soft tissue stress and its contribution in supporting the plantar arch could help to guide the clinical decision. Traditional experimental trials cannot consistently evaluate the contribution of each tissue. Therefore, in this research a 3-Dimensional FE foot model was reconstructed from a normal patient in order to measure the stress of the passive stabilizers of the arch, and its variation in different scenarios related with intermediate stages of AAFD development. All bones, the plantar fascia (PF), cartilages, plantar ligaments and the spring ligament (SL) were included, respecting their anatomical distribution and biomechanical characteristics. An AAFD evaluation scenario was simulated. The relative contribution of each tissue was obtained comparing each result with a normal case. The results show that PF is the main tissue that prevents the arch elongation, while SL mainly reduces the foot pronation. Long and short plantar ligaments play a secondary role in this process. The stress increment on both PF and SL when one of two fails suggests that these tissues complement each other. These findings support the theory that regards the tibialis posterior tendon as a secondary actor in the arch maintenance, compared with the PF and the SL, because this tendon is overstretched by the hindfoot pronation around the talonavicular joint. This approach could help to improve the understanding of AAFD

Effectiveness of the Lapidus plate system in foot surgery: A PRISMA compliant systematic review

Lapidus arthrodesis is an established standard procedure to correct various foot surgery problems and hallux limitus, hypermobility of the first ray, hallux abductus valgus, and symptomatic lesser metatarsal. After decades, many fixation methods in the orthopaedic surgery industry have been developed for decreasing complications and improving this technique. The aim of this PRISMA compliant systematic review is to analyse the effectiveness of several lapidus plate systems in foot surgery. We have carried out the first systematic review of the relevant published literature so as to systematically evaluate the scientific knowledge available now on this association, assigning predefined eligibility criteria. Fourteen studies were selected which had an overall of 738 cases. The first tarsal metatarsal joint and hallux valgus were treated by the application of different types of Lapidus plate system. The optimal level of the fixation in these procedures is related with the type and system insertion place of the plate with or without screw in each specific foot disease. There is an insufficient number of studies about the effectiveness of the different types of Lapidus plate system in foot surgery, and there is a need to increase outcomes knowledge on the level of the fixation, sort of the system, and insert place in foot surgery

Experimental validation of finite elements model in hip fracture and its clinical applicability

[ES] La fractura de la extremidad proximal de fémur es objeto de interés en inves-tigación. La complejidad del entramado óseo y la ineficiencia estructural asociada alenvejecimiento hacen que existan muchas variables todavía por comprender desde el puntode vista experimental, pero no existe un modelo de investigación estructural y biomecánico dela fractura de cadera claramente definido.La hipótesis de este trabajo es que es posible desarrollar un modelo de experimentacióncomputacional que caracterice el hueso de la extremidad proximal del fémur como un materialheterogéneo a partir de la traslación directa de los parámetros mecánicos obtenidos de piezasanatómicas de experimentación.Material y método:Trabajo experimental que compara la experimentación real en cadáver yun modelo numérico basado en análisis de elementos finitos (AEF). Las variables que se hanempleado son: punto de inicio de la fractura, su propagación, carga progresiva y la carga máximahasta fractura.Al modelo computacional se trasladaron los parámetros mecánicos reales obtenidos de laspiezas anatómicas basándose en la relación entre las unidades Hounsfield de la TA C de altaresolución y la densidad mineral ósea de cada elemento virtual, mientras que la propagaciónde la fractura se modeló mediante desarrollo computacional propio del equipo investigador,con disminución de las propiedades mecánicas de los elementos da ¿nados conforme avanza lalínea fractuaria.Resultados: El modelo computacional fue capaz de determinar el punto de inicio de la fractura,con una discreta tendencia a la medialización anatómica de dicho punto respecto a lo ocurridode manera experimental. El grado de correlación fue muy alto al comparar el valor real dedeformación progresiva de las muestras frente al obtenido por el modelo computacional. Sobre32 puntos analizados, se obtuvo una pendiente de 1,03 en regresión lineal, con un error relativoentre las deformaciones del 6% y un coeficiente de Pearson de R2=0,99. El modelo computacionalinfraestimó discretamente la carga máxima de fractura, con un error relativo aproximado al10%.Conclusión: El modelo computacional de AEF desarrollado por este equipo investigador mul-tidisciplinar se puede considerar, en conjunto, un modelo completo de AEF de la extremidadproximal del fémur con aplicabilidad clínica futura al ser capaz de simular e imitar el compor-tamiento biomecánico de fémures humanos contrastado con un modelo experimental clásicorealizado en piezas anatómicas. Sobre esta base podrán evaluarse interacciones cualitativasy cuantitativas que lo consoliden como un potente banco de ensayos de experimentacióncomputacional sobre el fémur proximal humano[EN] Fracture of the proximal extremity of the femur is the subject of research interest. The complexity of the bone framework and the structural inefficiency associated with ageing leave many variables yet to be understood from an experimental perspective. However, there is no clearly defined structural and biomechanical research model for hip fracture. The hypothesis of this paper is that it is possible to create a computational experimentation model that characterises the bone of the proximal extremity of the femur as a heterogeneous material from directly translating the mechanical parameters obtained from anatomical experimentation specimens. Material and method An experimental paper comparing real experimentation on cadavers and a numerical model based on finite element analysis (FEA). The variables uses were: the start point of the fracture, propagation of the fracture, progressive load and maximum load until fracture. The real mechanical parameters obtained from the anatomical specimens were translated to the computational model based on the relationship between the Hounsfield units of the high resolution CAT scan and the bone mineral density of each virtual element, whereas the propagation of the fracture was modelled by the research team's own computational design, reducing the mechanical properties of the damaged elements as the fracture line advanced. Results The computational model was able to determine the start point of the fracture, with a slight tendency towards anatomical medialisation of this point compared to what happened experimentally. The degree of correlation was very high on comparing the real value of progressive deformation of the samples compared to that obtained by the computational model. Over 32 points analysed, a slope of 1.03 in lineal regression was obtained, with a relative error between the deformations of 16% and a Pearson's coefficient of R2=.99. The computational model slightly underestimated the maximum fracture load, with a relative error of approximately 10%. Conclusion The FEA computational model developed by this multi-disciplinary research team could be considered, as a whole, a complete FEA model of the proximal extremity of the femur with future clinical applicability since it was able to simulate and imitate the biomechanical behaviour of human femurs contrasted with a traditional experimental model made from anatomical specimens. On this basis, qualitative and quantitative interactions can be assessed which consolidate it as a powerful computational experimentation test bench for the human proximal femur.Larrainzar-Garijo, R.; Caeiro, J.; Marco, M.; Giner Maravilla, E.; Miguélez, M. (2019). Validación experimental de un modelo de análisis de elementos finitos en fractura de cadera y su aplicabilidad clínica. Revista Española de Cirugía Ortopédica y Traumatología. 63(2):146-154. https://doi.org/10.1016/j.recot.2018.05.006146154632Cristofolini, L., Juszczyk, M., Martelli, S., Taddei, F., & Viceconti, M. (2007). In vitro replication of spontaneous fractures of the proximal human femur. Journal of Biomechanics, 40(13), 2837-2845. doi:10.1016/j.jbiomech.2007.03.015Santoni, B. G., Nayak, A. N., Cooper, S. A., Smithson, I. R., Cox, J. L., Marberry, S. T., & Sanders, R. W. (2016). Comparison of Femoral Head Rotation and Varus Collapse Between a Single Lag Screw and Integrated Dual Screw Intertrochanteric Hip Fracture Fixation Device Using a Cadaveric Hemi-Pelvis Biomechanical Model. Journal of Orthopaedic Trauma, 30(4), 164-169. doi:10.1097/bot.0000000000000552Haynes, R. C., Pöll, R. G., Miles, A. W., & Weston, R. B. (1997). Failure of femoral head fixation: a cadaveric analysis of lag screw cut-out with the gamma locking nail and AO dynamic hip screw. Injury, 28(5-6), 337-341. doi:10.1016/s0020-1383(97)00035-1Krischak, G. D., Augat, P., Beck, A., Arand, M., Baier, B., Blakytny, R., … Claes, L. (2007). Biomechanical comparison of two side plate fixation techniques in an unstable intertrochanteric osteotomy model: Sliding Hip Screw and Percutaneous Compression Plate. Clinical Biomechanics, 22(10), 1112-1118. doi:10.1016/j.clinbiomech.2007.07.016Basso, T., Klaksvik, J., Syversen, U., & Foss, O. A. (2014). A biomechanical comparison of composite femurs and cadaver femurs used in experiments on operated hip fractures. Journal of Biomechanics, 47(16), 3898-3902. doi:10.1016/j.jbiomech.2014.10.025Loh, B. W., Stokes, C. M., Miller, B. G., & Page, R. S. (2015). Femoroacetabular impingement osteoplasty. The Bone & Joint Journal, 97-B(9), 1214-1219. doi:10.1302/0301-620x.97b9.35263Tsai, A. G., Reich, M. S., Bensusan, J., Ashworth, T., Marcus, R. E., & Akkus, O. (2013). A fatigue loading model for investigation of iatrogenic subtrochanteric fractures of the femur. Clinical Biomechanics, 28(9-10), 981-987. doi:10.1016/j.clinbiomech.2013.09.009Knobe, M., Altgassen, S., Maier, K.-J., Gradl-Dietsch, G., Kaczmarek, C., Nebelung, S., … Buecking, B. (2017). Screw-blade fixation systems in Pauwels three femoral neck fractures: a biomechanical evaluation. International Orthopaedics, 42(2), 409-418. doi:10.1007/s00264-017-3587-yGarcía-Aznar, J. M., Bayod, J., Rosas, A., Larrainzar, R., García-Bógalo, R., Doblaré, M., & Llanos, L. F. (2008). Load Transfer Mechanism for Different Metatarsal Geometries: A Finite Element Study. Journal of Biomechanical Engineering, 131(2). doi:10.1115/1.3005174Cilla, M., Checa, S., Preininger, B., Winkler, T., Perka, C., Duda, G. N., & Pumberger, M. (2017). Femoral head necrosis: A finite element analysis of common and novel surgical techniques. Clinical Biomechanics, 48, 49-56. doi:10.1016/j.clinbiomech.2017.07.005Schileo, E., Taddei, F., Cristofolini, L., & Viceconti, M. (2008). Subject-specific finite element models implementing a maximum principal strain criterion are able to estimate failure risk and fracture location on human femurs tested in vitro. Journal of Biomechanics, 41(2), 356-367. doi:10.1016/j.jbiomech.2007.09.009Giner, E., Arango, C., Vercher, A., & Javier Fuenmayor, F. (2014). Numerical modelling of the mechanical behaviour of an osteon with microcracks. Journal of the Mechanical Behavior of Biomedical Materials, 37, 109-124. doi:10.1016/j.jmbbm.2014.05.006Morgan, E. F., & Keaveny, T. M. (2001). Dependence of yield strain of human trabecular bone on anatomic site. Journal of Biomechanics, 34(5), 569-577. doi:10.1016/s0021-9290(01)00011-2Go´mez-Benito, M. J., Garcı´a-Aznar, J. M., & Doblare´, M. (2005). Finite Element Prediction of Proximal Femoral Fracture Patterns Under Different Loads. Journal of Biomechanical Engineering, 127(1), 9-14. doi:10.1115/1.1835347Dragomir-Daescu, D., Salas, C., Uthamaraj, S., & Rossman, T. (2015). Quantitative computed tomography-based finite element analysis predictions of femoral strength and stiffness depend on computed tomography settings. Journal of Biomechanics, 48(1), 153-161. doi:10.1016/j.jbiomech.2014.09.016Rezaei, A., Giambini, H., Rossman, T., Carlson, K. D., Yaszemski, M. J., Lu, L., & Dragomir-Daescu, D. (2017). Are DXA/aBMD and QCT/FEA Stiffness and Strength Estimates Sensitive to Sex and Age? Annals of Biomedical Engineering, 45(12), 2847-2856. doi:10.1007/s10439-017-1914-5Khoo, B. C. C., Brown, K., Cann, C., Zhu, K., Henzell, S., Low, V., … Prince, R. L. (2008). Comparison of QCT-derived and DXA-derived areal bone mineral density and T scores. Osteoporosis International, 20(9), 1539-1545. doi:10.1007/s00198-008-0820-yKhoo, B. C. C., Brown, K., Zhu, K., Pollock, M., Wilson, K. E., Price, R. I., & Prince, R. L. (2011). Differences in structural geometrical outcomes at the neck of the proximal femur using two-dimensional DXA-derived projection (APEX) and three-dimensional QCT-derived (BIT QCT) techniques. Osteoporosis International, 23(4), 1393-1398. doi:10.1007/s00198-011-1727-6Dall’Ara, E., Eastell, R., Viceconti, M., Pahr, D., & Yang, L. (2016). Experimental validation of DXA-based finite element models for prediction of femoral strength. Journal of the Mechanical Behavior of Biomedical Materials, 63, 17-25. doi:10.1016/j.jmbbm.2016.06.004LOUBONNICK, S. (2007). HSA: Beyond BMD with DXA. Bone, 41(1), S9-S12. doi:10.1016/j.bone.2007.03.007Marco, M., Larraínzar, R., Giner, E., Caeiro, J. R., & Miguélez, H. (2016). Análisis de la variación del comportamiento mecánico de la extremidad proximal del fémur mediante el método XFEM (eXtended Finite Element Method). Revista de Osteoporosis y Metabolismo Mineral, 8(2), 61-69. doi:10.4321/s1889-836x2016000200003Lenich, A., Bachmeier, S., Prantl, L., Nerlich, M., Hammer, J., Mayr, E., … Füchtmeier, B. (2011). Is the rotation of the femural head a potential initiation for cutting out? A theoretical and experimental approach. BMC Musculoskeletal Disorders, 12(1). doi:10.1186/1471-2474-12-79Kurz, S., Pieroh, P., Lenk, M., Josten, C., & Böhme, J. (2017). Three-dimensional reduction and finite element analysis improves the treatment of pelvic malunion reconstructive surgery. Medicine, 96(42), e8136. doi:10.1097/md.0000000000008136Vercher, A., Giner, E., Arango, C., Tarancón, J. E., & Fuenmayor, F. J. (2013). Homogenized stiffness matrices for mineralized collagen fibrils and lamellar bone using unit cell finite element models. Biomechanics and Modeling in Mechanobiology, 13(2), 437-449. doi:10.1007/s10237-013-0507-

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

The cut-out phenomenon in intertrochanteric femur fracture: analysis using a finite element model

Trabajo premiado con una beca FEIOMM de Investigación Básica 2018.Objetive: This work aimed to analyze the cut‐out phenomenon, which involves oblique displacements and/or rotations of the femoral head around the cephalic component of the intramedullary nail. The analysis was carried out using finite element numerical models. This technique seeks to understand the failure of this type of fixation and establish what po‐sitioning of the system favors or prevents failure due to cut‐out. Material and methods: The study was carried out on a numerical model of the proximal limb of an artificial femur and an intramedullary nail type PFNA (proximal femoral nail anti‐rotation). In the numerical model, the position of the in‐tramedullary nail was varied in the anterior/posterior and superior/inferior directions to analyze the influence of the position on the cut‐out phenomenon. Stresses in critical areas and torque on the nail under normal position loading were analyzed. Results: The most critical position was the one in which the intramedullary nail is placed in the superior position, due to the high compressions that appear in the trabecular bone of the femoral head. The centered position of the nail de‐creased the risk of bone damage and the torque that the intramedullary nail has to support. Conclusions: This type of model allows us to simulate the influence of the nail position and obtain variables that are otherwise difficult to analyze. Although it is a simple model with static load, it confirms that a centered position of the intramedullary nail reduces the risk of cut‐out .Objetivo: El objetivo del trabajo fue analizar el fenómeno de cut-out, fenómeno que supone desplazamientos oblicuos y/o rotaciones de la cabeza femoral alrededor del componente cefálico del clavo intramedular. El análisis se llevó a cabo mediante modelos numéricos de elementos finitos. Con esta técnica se busca entender el fallo de este tipo de fijaciones y establecer qué posicionamiento del sistema favorece o evita el fallo por cut-out. Material y métodos: El estudio se realizó sobre un modelo numérico de la extremidad proximal de un fémur artificial y un clavo intramedular tipo PFNA (femoral proximal de antirrotación). En el modelo numérico se varió la posición del clavo intramedular en dirección anterior/posterior y superior/inferior para analizar la influencia de la posición en el fenómeno de cut-out. Se analizaron las tensiones en zonas críticas y par torsor sobre el clavo bajo una carga en posición normal. Resultados: La posición más crítica fue aquella en la que el clavo intramedular está colocado en la posición superior, debido a las altas compresiones que aparecen en el hueso trabecular de la cabeza femoral. La posición centrada del clavo disminuyó el riesgo de daño óseo y el par torsor que tiene que soportar el clavo intramedular. Conclusión: Este tipo de modelos permite simular la influencia de la posición del clavo y obtener variables que de otra manera son difíciles de analizar. Aunque se trata de un modelo sencillo con carga estática, confirma que una posición centrada del clavo intramedular disminuye el riesgo de cut-out.Los autores agradecen la financiación recibida a través de la Sociedad Española de Investigación Ósea y del Metabolismo Mineral con la Beca de Investigación 2018. También agradecen la financiación recibida a través del Ministerio de Ciencia e Innovación y el Programa FEDER a través de los proyectos DPI2017-89197-C2-1-R y DPI2017-89197-C2-2-R

Numerical modelling of cancellous bone damage using an orthotropic failure criterion and tissue elastic properties as a function of the mineral content and microporosity.

[EN] Background and objective : Elastic and strength properties of lamellar tissue are essential to analyze the mechanical behaviour of bone at the meso- or macro-scale. Although many effort s have been made to model the architecture of cancellous bone, in general, isotropic elastic constants are assumed for tissue modelling, neglecting its non-isotropic behaviour. Therefore, isotropic damage laws are often used to esti- mate the bone failure. The main goals of this work are: (1) to present a new model for the estimation of the elastic properties of lamellar tissue which includes the bone mineral density (BMD) and the micro- porosity, (2) to address the numerical modelling of cancellous bone damage using an orthotropic failure criterion and a discrete damage mechanics analysis, including the novel approach for the tissue elastic properties aforementioned. Methods : Numerical homogenization has been used to estimate the elastic properties of lamellar bone considering BMD and microporosity. Microcomputed Tomography ( ¿-CT) scans have been performed to obtain the micro-finite element ( ¿-FE) model of cancellous bone from a vertebra of swine. In this model, lamellar tissue is orientated by considering a unidirectional layer pattern being the mineralized colla- gen fibrils aligned with the most representative geometrical feature of the trabeculae network. We have considered the Hashin¿s failure criterion and the Material Property Degradation (MPDG) method for sim- ulating the onset and evolution of bone damage. Results: The terms of the stiffness matrix for lamellar tissue are derived as functions of the BMD and mi- croporosity at tissue scale. Results obtained for the apparent yield strain values agree with experimental values found in the literature. The influence of the damage parameters on the bone mechanics behaviour is also presented. Conclusions : Stiffness matrix of lamellar tissue depends on both BMD and microporosity. The new ap- proach presented in this work enables to analyze the influence of the BMD and porosity on the mechan- ical response of bone. Lamellar tissue orientation has to be considered in the mechanical analysis of the cancellous bone. An orthotropic failure criterion can be used to analyze the bone failure onset instead of isotropic criteria. The elastic property degradation method is an efficient procedure to analyze the failure propagation in a 3D numerical model.The authors acknowledge the Ministerio de Ciencia e Innovacion and the European Regional Development Fund (FEDER) for the financial support received through the projects PID2020-118920RB-I00 and PID2020-118480RB-C21, the Generalitat Valenciana for Plan FDGENT 2018 and Programme PROMETEO 2021/046.Megías-Díaz, R.; Vercher Martínez, A.; Belda, R.; Peris Serra, JL.; Larrainzar-Garijo, R.; Giner Maravilla, E.; Fuenmayor Fernández, F. (2022). Numerical modelling of cancellous bone damage using an orthotropic failure criterion and tissue elastic properties as a function of the mineral content and microporosity. Computer Methods and Programs in Biomedicine. 219:1-17. https://doi.org/10.1016/j.cmpb.2022.10676411721

Spanish National Hip Fracture Registry (RNFC): analysis of its first annual report and international comparison with other established registries

Summary Hip fracture registries have helped improve quality of care and reduce variability, and several audits exist worldwide. The results of the Spanish National Hip Fracture Registry are presented and compared with 13 other national registries, highlighting similarities and differences to define areas of improvement, particularly surgical delay and early mobilization. Introduction Hip fracture audits have been useful for monitoring current practice and defining areas in need of improvement. Most established registries are from Northern Europe. We present the results from the first annual report of the Spanish Hip Fracture Registry (RNFC) and compare them with other publically available audit reports. Method Comparison of the results from Spain with the most recent reports from another ten established hip fracture registries highlights the differences in audit characteristics, casemix, management, and outcomes. Results Of the patients treated in 54 hospitals, 7.208 were included in the registry between January and October 2017. Compared with other registries, the RNFC included patients ≥ 75 years old; in general, they were older, more likely to be female, had a worse prefracture ambulation status, and were more likely to have extracapsular fractures. A larger proportion was treated with intramedullary nails than in other countries, and spinal anesthesia was most commonly used. With a mean of 75.7 h, Spain had by far the longest surgical delay, and the lowest proportion of patients mobilized on the first postoperative day (58.5%). Consequently, development of pressure ulcers was high, but length of stay, mortality, and discharge to home remained in the range of other audits. Conclusions National hip fracture registries have proved effective in changing clinical practice and our understanding of patients with this condition. Such registries tend to be based on an internationally recognized common dataset which would make comparisons between national registries possible, but variations such as age inclusion criteria and follow-up are becoming evident across the world. This variation should be avoided if we are to maximize the comparability of registry results and help different countries learn from each other’s practice. The results reported in the Spanish RNFC, compared with those of other countries, highlight the differences between countries and detect areas of improvement, particularly surgical delay and early mobilization

Spanish National Hip Fracture Registry (RNFC): analysis of its first annual report and international comparison with other established registries

Summary Hip fracture registries have helped improve quality of care and reduce variability, and several audits exist worldwide. The results of the Spanish National Hip Fracture Registry are presented and compared with 13 other national registries, highlighting similarities and differences to define areas of improvement, particularly surgical delay and early mobilization. Introduction Hip fracture audits have been useful for monitoring current practice and defining areas in need of improvement. Most established registries are from Northern Europe. We present the results from the first annual report of the Spanish Hip Fracture Registry (RNFC) and compare them with other publically available audit reports. Method Comparison of the results from Spain with the most recent reports from another ten established hip fracture registries highlights the differences in audit characteristics, casemix, management, and outcomes. Results Of the patients treated in 54 hospitals, 7.208 were included in the registry between January and October 2017. Compared with other registries, the RNFC included patients ≥ 75 years old; in general, they were older, more likely to be female, had a worse prefracture ambulation status, and were more likely to have extracapsular fractures. A larger proportion was treated with intramedullary nails than in other countries, and spinal anesthesia was most commonly used. With a mean of 75.7 h, Spain had by far the longest surgical delay, and the lowest proportion of patients mobilized on the first postoperative day (58.5%). Consequently, development of pressure ulcers was high, but length of stay, mortality, and discharge to home remained in the range of other audits. Conclusions National hip fracture registries have proved effective in changing clinical practice and our understanding of patients with this condition. Such registries tend to be based on an internationally recognized common dataset which would make comparisons between national registries possible, but variations such as age inclusion criteria and follow-up are becoming evident across the world. This variation should be avoided if we are to maximize the comparability of registry results and help different countries learn from each other’s practice. The results reported in the Spanish RNFC, compared with those of other countries, highlight the differences between countries and detect areas of improvement, particularly surgical delay and early mobilization