Clinically relevant differences in stress shielding between two short-stemmed femoral prostheses

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Bone physiology

Background:

• Short-stemmed endoprostheses aim to improve proximal load transmission and mitigate stress-shielding in the femur.
• Existing literature debates stress shielding, clinical outcomes, and long-term stability of various prosthesis systems.

Purpose of the Study:

• To compare the stress-shielding effects and bone mineral density (BMD) changes between Nanos™ and Optimys™ short-stem prostheses.
• To evaluate the clinical outcomes and radiographic parameters of these two implant types in patients with coxarthrosis.

Main Methods:

• A prospective randomized study involving 52 patients with coxarthrosis.
• Assessment of BMD and stress shielding using DEXA scans at baseline and one year.
• Clinical outcomes measured by Harris Hip Score (HHS); radiographic parameters included offset, CCD angle, leg length, stem migration, and inclination.

Main Results:

• Optimys™ demonstrated superior BMD preservation, with less significant bone loss in Gruen zones compared to Nanos™.
• While both stems showed excellent HHS scores, Nanos™ exhibited greater BMD reduction in key proximal femur zones.
• Radiographic changes like stem migration and inclination were clinically acceptable in both groups, with no significant inter-group differences.

Conclusions:

• The Optimys stem offers reduced stress shielding and enhanced proximal load transmission, leading to better BMD preservation.
• Both short-stem prostheses yield excellent clinical hip function, but Optimys™ shows an advantage in maintaining proximal femur bone density.