The stability of small pegs for cementless implant fixation
File(s)Geraldes_et_al-2017-Journal_of_Orthopaedic_Research.pdf (758.44 KB)
Published version
Author(s)
Geraldes, D
Hansen, U
Jeffers, J
Amis, A
Type
Journal Article
Abstract
Most glenoid implants rely on large centrally located fixation features to avoid perforation of the glenoid vault in its peripheral regions. Upon revision of such components there may not be enough bone left for the reinsertion of an anatomical prosthesis. Multiple press-fit small pegs would allow for less bone resection and strong anchoring in the stiffer and denser peripheral subchondral bone. This study assessed the fixation characteristics, measured as the push-in (Pin) and pull-out (Pout) forces, and spring-back, measured as the elastic displacement immediately after insertion, for five different small press-fitted peg configurations manufactured out of UHMWPE cylinders (5 mm diameter and length). A total of 16 specimens for each configuration were tested in two types of solid bone substitute: Hard (40 PCF, 0.64 g/cm3, worst-case scenario of Pin) and soft (15 PCF, 0.24 g/cm3, worst-case scenario of spring-back and Pout). Two different diametric interference-fits were studied. Geometries with lower stiffness fins (large length to width aspect ratio) were the best performing designs in terms of primary fixation stability. They required the lowest force to fully seat, meaning they are less damaging to the bone during implantation, while providing the highest Pout/Pin ratio, indicating that when implanted they provide the strongest anchoring for the glenoid component. It is highlighted that drilling of chamfered holes could minimize spring-back displacements. These findings are relevant for the design of implants press-fitted pegs because primary fixation has been shown to be an important factor in achieving osseointegration and longevity of secondary fixation.
Date Issued
2017-05-23
Date Acceptance
2017-04-03
Citation
Journal of Orthopaedic Research, 2017, 35 (12), pp.2765-2772
ISSN
1554-527X
Publisher
Wiley
Start Page
2765
End Page
2772
Journal / Book Title
Journal of Orthopaedic Research
Volume
35
Issue
12
Copyright Statement
© 2017 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Sponsor
Wellcome Trust
Grant Number
WT 098269/Z/12/Z
Subjects
cementless implant fixation
glenoid
interference fit
press-fit
shoulder
0903 Biomedical Engineering
1103 Clinical Sciences
1106 Human Movement And Sports Science
Orthopedics
Publication Status
Published