Assembly force and taper angle difference influence the relative motion at the stem-neck interface of bi-modular hip prostheses

Bi-modular hip arthroplasty prostheses allow adaptation to the individual patient anatomy and the combination of different materials but introduce an additional interface, which was related lately to current clinical issues. Relative motion at the additional taper interface might increase the overall risk of fretting, corrosion, metallic debris and early failure. The aim of this study was to investigate whether the assembly force influences the relative motion and seating behaviour at the stem-neck interface of a bi-modular hip prosthesis (Metha(®); Aesculap AG, Tuttlingen, Germany) and whether this relation is influenced by the taper angle difference between male and female taper angles. Neck adapters made of titanium (Ti6Al4V) and CoCr (CoCr29Mo) were assembled with a titanium stem using varying assembly forces and mechanically loaded. A contactless eddy current measurement system was used to record the relative motion between prosthesis stem and neck adapter. Higher relative motion was observed for Ti neck adapters compared to the CoCr ones (p < 0.001). Higher assembly forces caused increased seating distances (p < 0.001) and led to significantly reduced relative motion (p = 0.019). Independent of neck material type, prostheses with larger taper angle difference between male and female taper angles exhibited decreased relative motion (p < 0.001). Surgeons should carefully use assembly forces above 4 kN to decrease the amount of relative motion within the taper interface. Maximum assembly forces, however, should be limited to prevent periprosthetic fractures. Manufacturers should optimize taper angle differences to increase the resistance against relative motion.

Subjects

modular prosthesis

assembly force

relative motion

stem–neck interface

taper angle difference

arthroplasty

biomechanical phenomena

humans

materials testing

motion

prosthesis design

prosthesis failure

mechanical stress

titanium

vitallium

hip prosthesis

hip replacement

DDC Class

610: Medizin

Lizenz

http://rightsstatements.org/vocab/InC/1.0/

Name

0954411916648717.pdf

Size

3.08 MB

Format

Adobe PDF

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Assembly force and taper angle difference influence the relative motion at the stem-neck interface of bi-modular hip prostheses