The Influence of Geometry of Implants for Direct Skeletal Attachment of Limb Prosthesis on Rehabilitation Program and Stress-Shielding Intensity

Abstract

The purpose of the research was to evaluate the influence of selected parameters of the implants for bone anchored prostheses on possibility of conducting static load bearing exercises and stress-shielding intensity. A press-fit implant, a threaded implant, and the proposed design were compared using the finite element method. For the analyses two features were examined: diameter (19.0 – 21.0 mm) and length (75.0 – 130.0 mm). To define the possibility of conducting rehabilitation exercises the micromotion of implants while axial loading with a force up to 1000 N was examined to evaluate the changes at implant-bone interface. The stress-shielding intensity was estimated by bone mass loss over 60 months. The results suggest that, in terms of micromotion generated during rehabilitation exercises, the threaded (max. micromotion of 16.00 μm) and the proposed (max. micromotion of 45.43 μm) implants ensure low and appropriate micromotion. In the case of the press-fit solution the load values should be selected with care, as there is a risk of losing primary stabilisation. The allowed forces (that do not stimulate the organism to generate fibrous tissue) were approx. 140 N in the case of the length of 75 mm, increasing up to 560 N, while using the length of 130 mm. Moreover, obtained stress-shielding intensities suggest that the proposed implant should provide appropriate secondary stability, similar to the threaded solution, due to the low bone mass loss during long-term use (improving at the same time more bone remodelling in distal Gruen zones, by providing lower bone mass loss by approx. 13% to 20% in dependency of the length and diameter used). On this basis it can be concluded that the proposed design can be an appropriate alternative to commercially used implants.

The effect of cortical thickness and thread profile dimensions on stress and strain in bone-anchored implants for amputation prostheses

“…The intention was to provide knowledge on how the careful selection of design features can minimize the risk of bone or implant fracture during use. This study contrasts earlier FEbased studies which have been either case studies with subject specific anatomy [25]- [32], studies focused exclusively on bone remodelling around the implant [31], [33], or FE-implementations with too low resolution to accurately capture the stress in the threaded region [25], [27]- [30], [32], [34]- [37].…”

The effect of cortical thickness and thread profile dimensions on stress and strain in bone-anchored implants for amputation prostheses

“…The intention was to provide knowledge on how the careful selection of design features can minimize the risk of bone or implant fracture during use. This study contrasts earlier FEbased studies which have been either case studies with subject specific anatomy [25]- [32], studies focused exclusively on bone remodelling around the implant [31], [33], or FE-implementations with too low resolution to accurately capture the stress in the threaded region [25], [27]- [30], [32], [34]- [37].…”

The Potential of a Nanostructured Titanium Oxide Layer with Self-Assembled Monolayers for Biomedical Applications: Surface Properties and Biomechanical Behaviors

“…The SAMs-coated surfaces exhibited a decrease in stiffness as a consequence of the formation of the bisphosphonate monolayer, which could disperse stress concentration, hence decreasing the stress shielding effect [40]. The formation of stress shielding can cause a loss of bone tissue around the implant and poor osseointegration [41][42][43]. Accordingly, the PUA-SAM/TiO sample is believed to prevent the stress shielding effect and possess better in vivo bone regeneration ability in comparison to the control sample and the other SAMs-coated samples.…”