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Introduction The loss of bone mass, as a consequence of bone remodelling, in the proximal third of the femur, is a factor that contributes to the failure of hip prostheses in the medium to long term. This periprosthetic remodelling occurs mainly during the first 12 months after the operation. The aim is to evaluate the behaviour at one year of a new anatomical stem, the ANATO® stem (2015-Stryker®), which is a redesign of its predecessor (ABG-II®—Stryker stem) by means of bone densitometry. Method Prospective, controlled study in which the changes in bone mineral density (BMD) observed around the 7 areas of Gruen in a group of 61 patients affected by primary coxarthrosis, in whom an ANATO® stem was implanted, are analysed densitometrically. The healthy hip was taken as the control group. The existence of differences in the remodelling pattern according to sex, age and body mass index (BMI) was compared. The follow-up was during the first year after the intervention. Results After one year of follow-up, decreases of bone mineral density in zone 7 of −5.9% were observed, being this decrease statistically significant. No differences were found in the remodeling pattern according to age, sex and body mass index. Conclusion The ANATO® stem allows an efficient transmission of loads from the stem to the proximal femur. Only in zone 7 significant bone atrophy is observed. Differences in age, BMI and sex do not seem to influence the bone remodelling around this new stem.

Resumen: Introducción: La pérdida de masa ósea, como consecuencia del remodelado óseo, en el tercio proximal del fémur, es un factor que contribuye al fracaso de las prótesis de cadera a medio-largo plazo. Este remodelado periprotésico se desarrolla sobre todo durante los 12 primeros meses tras la intervención.Se pretende evaluar el comportamiento a un año de un nuevo vástago anatómico, el vástago ANATO® (2015-Stryker®), el cual es un rediseño de su predecesor (vástago ABG-ii®--Stryker) mediante densitometría ósea. Material y método: Estudio prospectivo, controlado, en el que se analizan densitométricamente los cambios en la densidad mineral ósea (DMO), observados en torno a las siete áreas de Gruen, en un grupo de 61 pacientes, afectos de coxartrosis primaria, en quienes se implantó un vástago ANATO®. La cadera sana fue tomada como grupo control. Se comparó la existencia de diferencias en el patrón de remodelado según sexo, edad e índice de masa corporal (IMC). El seguimiento fue durante el primer año tras la intervención. Resultados: Al año de seguimiento se aprecian descensos de la densidad mineral ósea en la zona siete, de -5,9%, siendo este descenso estadísticamente significativo. No se encontraron diferencias en el patrón de remodelado según edad, sexo e índice de masa corporal. Conclusión: El vástago ANATO®, permite una transmisión eficiente de cargas desde el vástago al fémur próximal. Únicamente en la zona siete se aprecia atrofia ósea significativa. Las diferencias de edad, IMC y sexo parecen no influir en la remodelación ósea en torno a este nuevo vástago. Abstract: Introduction: The loss of bone mass, as a consequence of bone remodelling, in the proximal third of the femur, is a factor that contributes to the failure of hip prostheses in the medium to long term. This periprosthetic remodelling occurs mainly during the first 12 months after the operation.The aim is to evaluate the behaviour at one year of a new anatomical stem, the ANATO® stem (2015-Stryker®), which is a redesign of its predecessor (ABG-ii®-Stryker stem) by means of bone densitometry. Method: Prospective, controlled study in which the changes in bone mineral density (BMD) observed around the seven areas of Gruen in a group of 61 patients affected by primary coxarthrosis, in whom an ANATO® stem was implanted, are analysed densitometrically. The healthy hip was taken as the control group. The existence of differences in the remodelling pattern according to sex, age and body mass index (BMI) was compared. The follow-up was during the first year after the intervention. Results: After one year of follow-up, decreases of bone mineral density in zone seven of -5.9% were observed, being this decrease statistically significant. No differences were found in the remodelling pattern according to age, sex and body mass index. Conclusion: The ANATO® stem allows an efficient transmission of loads from the stem to the proximal femur. Only in zone seven significant bone atrophy is observed. Differences in age, BMI and sex do not seem to influence the bone remodelling around this new stem.