• Matteo Formica, Andrea Zanirato, Edoardo Bori, Tullio Andrea Revetria, Juljana Ditting, and Bernardo Innocenti.
• Dipartimento di Scienze Chirurgiche e Diagnostiche Integrate (DISC), Università Degli Studi di Genova, Viale Benedetto XV N°6, 16132, Genoa, Italy.
• Arch Orthop Trauma Surg. 2024 Feb 1; 144 (2): 917926917-926.

BackgroundThe influence of THA stem design on periprosthetic femoral fractures (PFFs) risk is subject of debate. This study aims to compare the effects of different cementless stem designs on stress-strain distributions in both physiological and osteoporotic femur under various loading conditions.MaterialsA biomechanical study using finite-element analysis was conducted. Four models were developed: three with implanted femurs and a native one chosen as control. Each model was analyzed for both healthy and osteoporotic bone. The following stem designs were examined: short anatomical stem with femoral neck preservation, double-wedge stem, and anatomical standard stem. Three loading conditions were assessed: gait, sideways falling, and four-point bending.ResultsDuring gait in physiological bone, the anatomical stem and the short anatomical stem with femoral neck preservation showed stress distribution similar to the native model. The double-wedge stem reduced stress in the proximal area but concentrated it in the meta-diaphysis. In osteoporotic bone, the double-wedge stem design increased average stress by up to 10%. During sideways falling, the double-wedge stem exhibited higher stresses in osteoporotic bone. No significant differences in average stress were found in any of the studied models during four-point bending.ConclusionIn physiological bone, anatomical stems demonstrated stress distribution comparable to the native model. The double-wedge stem showed uneven stress distribution, which may contribute to long-term stress shielding. In the case of osteoporotic bone, the double-wedge stem design resulted in a significant increase in average stress during both gait and sideways falling, potentially indicating a higher theoretical risk of PFF.© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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