Changes in periprosthetic bone remodelling after redesigning an anatomic cementless stem

Abstract

The aim of this prospective cohort study was to determine the densitometric relevance of minor design modifications of a cementless stem designed to improve proximal load transfer. We used a prospective cohort study with densitometric analysis over a five-year period of two groups of patients with primary osteoarthritis. The first group, 56 hips, received the first version of the ABG stem (ABG-I); the second group, 54 hips, had the ABG-II stem. The results obtained with the ABG-I stem showed a decrease of bone density in proximal areas that ranged from 13% to 37%. However, the new design had a decrease of the same areas that ranged from 9% to 23%. These differences were noted at the end of the first post-operative year and remained stable, except in zone 7, where they were progressive. There is little evidence that the modified stem reduces femoral bone density loss.Résumé Nous avons revu de façon rétrospective 68 hanches chez 62 patients présentant une dysplasie acétabulaire et ayant bénéficié d'une ostéotomie péri-acétabulaire. Parmi ces 68 hanches, 33 avaient en préopératoire une rétroversion acétabulaire (groupe rétroversion) et 35 une antéversion (groupe contrôle). Toutes les hanches ont été évaluées selon le score de Harris. L'évaluation radiographique de la rétroversion acétabulaire et du mur postérieur déficient ont été basées sur le signe du croisement et le signe du mur extérieur. Les scores cliniques des deux groupes au suivi final était semblable. Dans le groupe rétroversion, 12 hanches avaient antéversé leur acétabulum en post-opéra-toire le signe du mur postérieur disparaissant, mais celui-ci restant présent dans 21 hanches avec un acétabulum en rétroversion post-opératoire. Parmi les 21 hanches avec acétabulum rétroversé une coxarthrose postérieure s'est développée à 5 ans post-opératoire. Lorsque l'on réalise une correction par ostéotomie pour une hanche dysplasique avec un acétabulum rétroversé, il est important de corriger cette rétroversion de façon à prévenir une coxarthrose secondaire due à la déficience du mur postérieur.

The Cementless Anatomic Benoist Girard (ABG) II Total Hip Arthroplasty

“…Bone remodelling with signs of proximal femoral stress shielding around the ABG I femoral component has been extensively reported in the literature [17,[24][25][26][27]. Recently, using both finite element analysis and DEXA, comparative studies have indicated that the ABG II femoral component was more effective than the first generation in terms of proximal femoral bone stock atrophy preservation [31,32]. No bone-implant radiolucency was observed in the areas coated with hydroxyapatite, whereas reactive lines related to distal elasticity and to medullary diaphyseal bone reaction closed to the polished tip were only observed in Gruen Zones 3, 4, and 5 in less than 6% of cases.…”

An in vitro study of the strain distribution in human femora with anatomical and customised femoral stems

“…39 DXA studies of the ABG stem showed a reduction of 16% and 17% in BMD three and five years, respectively, after hip replacement. 18,40 Some of the initial bone loss could be a result of intra-operative rasping and reaming. 38 The importance of the early resorption of bone within two years is not known, but according to the Norwegian arthroplasty register both the Unique and the ABG-I stems have a survival rate of more than 96% after ten years, using aseptic loosening as the endpoint.…”

Simulation by Finite Elements of Bone Remodeling After Implantation of Femoral Stems

“…In both studies the surgical technique, post-operative rehabilitation program, densitometry studies and statistical analysis were identical (Panisello et al, 2009b). The study confirmed less proximal atrophy, therefore one could ask if the new design has effectively improved the load transfer conditions in the proximal femur, producing less stress-shielding.…”

“…Prior to the development of our FE models several long-term studies of bone remodeling after the implantation of two different cementless stems, ABG I and ABG II, were performed Panisello et al, 2009a;Panisello et al, 2009b). These studies were performed using DXA, a technique that allows an accurate assessment of bone density losses in the different Gruen zones.…”