Abstract
Introduction: Revision surgery of loose hip joint is always an extensive intervention in the initial removal of the prosthesis with a complex solution of the anchorage ground of the new implant in the bone defect. In this study, we focused on the possibility of reducing the risk of oval holes failure due to insufficient primary fixation.
The aim was to test the hypothesis that the use of angular stable screws affects the bond strength of the implant with bone tissue. Method and material: The problem was solved by modelling the experimental cadaver beef basins.
For evaluation we used the pull-out test (tensile test). The assessment of the size dependence of tensile forces in the axis of the implant to stretch (pull) TC wells from bone bed. 4 tests were conducted with a fixed hole, 2 or 4 titanium screws (angularly stable, standard).
The measured values were processed on Instron 3382, Norwood, MA. We assumed that we shall prove better primary fixation of oval holes inspection by using angularly stable screws.
Results: The measured values show that for the fixation of holes by un-lockable standard screws with the increasing amount of tension it is likely to overload one screw which may then lead to its failure, or lifting. The remaining screws take over its function.
After the failure of the last screw, it will break off. The angularly stable screws show no bone fixation failure, but a plastic deformation.
Fixing holes revision by 4 screws ensures significantly higher stability of the implant when exposed to tensile force in the implant axis than fixation by 2 screws. Discussion: At our centre, in case of large acetabular defects, we implant oval holes inspection - type TC manufactured by the company Beznoska.
The literature dealing with the revision endoprothesis has not yet described the application of angularly stable screws, in case of spherical holes with pull-out tests a higher rigidity of fixation allowing implantation of wells in the field of destroyed or significantly porotic bone tissue was confirmed. Conclusion: Our studies have confirmed the hypothesis that the application of angularly stable screws into the holes in the proximal part of the revision oval hole in the TC pull-out test increases the primary stability.
Quality of primary implant stability is the most important factor for its reliable osteointegration which is significantly contributed by the osteoactive surface of the endoprosthesis.