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

Variations in bone mineral density after joint replacement: A systematic review examining different anatomical regions, fixation techniques and implant design

Purpose

This study aims to evaluate postoperative periprosthetic bone mineral density (BMD) at various time points following joint replacement with different implant designs and fixation techniques.

Methods

Database search was conducted on MEDLINE, Scopus, Cochrane Central Register of Controlled Trials, Web of Science, and CINAHL for studies analyzing bone remodelling after joint replacement (March 2002-January 2024). Inclusion criteria: English-language articles; total joint replacement; at least two BMD evaluations; observational studies, cross-sectional, prospective, retrospective, randomised controlled trials, and clinical trials. Exclusion criteria: no BMD measurement within one month after surgery; BMD data only expressed as percentage changes or graphs without numerical values; no Gruen zone evaluation for hip replacement; no periprosthetic bone evaluation for knee replacement; pharmacological treatment or comorbidities affecting BMD; revision joint replacements; irrelevant articles; no full text or no original data.

Results

Sixty-eight articles matched the selection criteria. Fifty-five focused on the hip joint, 12 on the knee, and one on the shoulder. After total hip arthroplasty, the greatest bone resorption occurred in the proximal femur, peaking at 6 months. Cemented implants and tapered stems showed greater bone resorption than cementless implants and anatomical stems. BMD around the acetabular component decreased during the first 6 months but increased in regions subjected to higher loads. In total knee arthroplasty, bone loss occurred in the anterior distal femur and medial tibial plateau, with cemented and posterior-stabilised implants showing greater bone loss than cementless and cruciate-retaining designs.

Conclusions

The periprosthetic BMD decreases progressively after joint replacement. The fixation technique and implant design influence the extent and pattern of this decline. These factors must be considered during the surgical planning, as they can have long-term implications for bone health and implant longevity. Further research is needed to optimise implant design and surgical techniques to mitigate BMD loss and improve patient outcomes.

Level of Evidence

Level IV.

Bone Remodeling of Two Anatomic Stems: Densitometric Study of the Redesign of the ABG-II Stem

Background

Periprosthetic bone remodeling, which is a phenomenon observed in all femoral stems, has a multifactorial origin as it depends on factors related to the patient, the surgical technique, and the design of the implant. To determine the pattern of remodeling produced by 2 models of anatomic cementless implants, we quantified the changes in bone mineral density (BMD) in the 7 areas of Gruen observed at different moments after surgery during the first postoperative year.

Methods

A prospective, comparative, controlled, 1-year follow-up densitometric study was carried out in 2 groups of patients suffering from primary unilateral hip osteoarthritis. In the first group, with 68 patients, an ABG-II stem was implanted. In the second, with 66 patients, the ANATO stem was used. The contralateral, healthy hip was taken as a control.

Results

Both groups showed a decrease in BMD at 3 months in all the areas, which recovered at the end of the study, except in zone 7: there was a 17.7% decrease in the ABG-II group and a 5.9% decrease in the ANATO group. In zones 2 and 6, where more loads are transmitted, conservation of BMD is observed in response to Wolff's law. The differences in the pattern of remodeling between groups were maintained despite the age, gender, and BMI of the patients or the size of the implants.

Conclusion

The ANATO stem achieved a more efficient transmission of loads at the metaphyseal level, which promotes bone preservation at the proximal femur, than the ABG-II stem.