Adaptive Bone Remodeling With New Design of the ABG Stem. Densitometric Study

To establish the pattern of bone remodeling caused by a cementless, anatomic implant, we intend to evaluate the changes in bone mineral density observed after surgery in the Gruen zones. A controlled, prospective study was carried out, in which a group of 37 patients with primary coxarthrosis were densitrometrically analyzed over the 1 year period following the implant of an ANATO stem (Stryker). The patient's healthy hip was taken as the control. Any differences in the remodeling pattern were compared according to age, body mass index, and implant size. Decreases in bone mineral density were observed after 3 months in all of the zones studied. However, this bone mineral density loss was recovered in all zones by the end of the study, except in zone 7 where a decrease of 7.2% in bone mass was observed. In zones 2 and 6, where more loads are transmitted, bone mass preservation, in accordance with Wolff's law, can be seen. No differences were found in the remodeling pattern in relation to age and body mass index. There were also no differences related to stem size except in zones 1 and 7. The ANATO stem achieves an efficient transmission of loads between the stem and the proximal femur, providing enough mechanical loads for bone preservation. It is only in zone 7 where significant bone atrophy can be observed, attributable to the damage that this area suffers during the surgical process and the subsequent stress-shielding caused by the implant design.