Evaluation of pull‐off strength and seating displacement of sleeved ceramic revision heads in modular hip arthroplasty

Abstract

Corrosion in revision total hip arthroplasty can be mitigated using a ceramic head on a well‐fixed in situ stem, but concerns of their early failure because of any surface defects on in situ stem necessitates the use of a titanium sleeve, which furnishes a factory‐finish surface. These sleeves are manufactured in different sizes allowing neck‐length adjustment. The strength of the taper junction of non‐sleeved primary heads is well‐investigated, but the influence of an interposed titanium sleeve on achieving a secure taper lock is unclear. Therefore, this study aimed to investigate the pull‐off strength and seating displacement of revision ceramic heads and titanium taper sleeves. Two different head diameters and two different taper adapter sleeve offset lengths were mated with trunnions at two different impaction forces. The seating displacement and pull‐off force was recorded for each specimen. Profilometry of the grooved outer surfaces of the sleeve and trunnion was done before and after testing to analyze the change in surface roughness. The influence of head diameter, sleeve offset, and impaction force on seating displacement and pull‐off force was analyzed using analysis of covariance. Pull‐off forces for 6 kN assembly force were approximately three times those for 2 kN. The head diameter did not have a significant effect on the measured parameters. Compared with short offset length sleeves, extra‐long increased seating displacement by 31% and reduced pull‐off forces by 15%. While sleeves of different offset lengths permit control of neck length, surgeons must be careful of the impact of this choice on the stability of implant. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1523–1528, 2020

Influence of a Modified Procedure of Joining Ceramic Head and Adapter Sleeve on the Stem Taper in Revision: An Experimental Study

“…Furthermore, some studies describe a force of 4 kN as the optimum impaction force for head taper [10,28,29,31,32], although the ISO 7206-10 [25] recommends a force of 2 kN. Various conditions influence the forces applied to the joint connection, such as the stiffness of the impact tip of the instrument [29] or the implant component size [33], so further investigations and detailed dimensioning are required to define the optimum joining force. Compensation could be achieved by using different tips or an adjustable force range of the instrument.…”

Trunnions and Modularity in Total Hip Arthroplasty: A Historical Review With Current Clinical Implications

“…When coupling the ceramic head to the existing trunnion, a titanium adapter sleeve is recommended to optimize taper fit and decrease material transfer because the sleeve provides a factory-finish surface in case of any surface defects on the in situ stem. 31,32 The one exception to this guideline occurs when treating ALTR in CoCr stem/CoCr head couples. In such cases, the ceramic head should be directly impacted onto the trunnion without an adapter sleeve because the titanium sleeve would introduce a mixed-metal couple, which increases the risk of metallosis.…”