, Volume 471, Issue 2, pp 403-409
Date: 05 Sep 2012

Acetabular Cup Design Influences Deformational Response in Total Hip Arthroplasty

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access

Abstract

Background

Press-fit acetabular components are susceptible to deformation in an underreamed socket, with excessive deformation of metal-on-metal (MOM) components potentially leading to increased torsional friction and micromotion. Specifically, however, it remains unclear how cup diameter, design, and time from implantation affect shell deformation.

Questions/purposes

We asked whether (1) changes in component geometry and material altered maximum shell deformation and (2) time-dependent deformational relaxation processes occurred.

Methods

Diametral deformation was quantified after press-fit implantation of metal shells into a previously validated polyurethane model. Experimental groups (n = 6–8) consisted of 48-, 54-, 60-, and 66-mm MOM cups of 6-mm wall thickness, 58-mm cups of 10-mm wall thickness, and CoCrMo and Ti6Al4V 58-mm modular cups.

Results

Greater cup diameter, thinner wall construction, and Ti6Al4V modular designs generated conditions for maximum shell deformation ranging from 0.047 to 0.267 mm. Relaxation (18%–32%) was observed 120 hours postimplantation in thin-walled and modular designs.

Conclusions

Our findings demonstrate a reduction of shell deformation over time and suggest, under physiologic loading, early component deformation varies with design.

Clinical Relevance

Component deformation should be a design consideration regardless of bearing surface. Designs neglecting to adequately address deformational changes in vivo could be susceptible to diminished cup survival, increased wear, and premature revision.

The institution of one or more of the authors (JBM, SRS, MEB, MAR) has received funding, during the study period, from St Francis Hospital (Mooresville, IN, USA), ERMI, Inc (Atlanta, GA, USA), DePuy Orthopedics, Inc (Warsaw, IN, USA), and Stryker Orthopaedics (Mahwah, NJ, USA). A partnering institution (Rose-Hulman) received funding from the National Science Foundation for the research instrumentation utilized in this study through Major Research Instrumentation Awards 0923135 and 1039716. One of the authors (JBM) certifies that he, or a member of his immediate family, has received or may receive payments or benefits, during the study period, an amount in excess of $100,000, from Biomet, Inc (Warsaw, IN, USA); one of the authors (MEB) certifies that he, or a member of his immediate family, has received or may receive payments or benefits, during the study period, an amount in excess of $100,000, from Biomet, Inc, and OrthAlign, Inc (Aliso Viejo, CA, USA).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA approval status, of any drug or device before clinical use.
Specimen preparation and data collection were conducted at Rose-Hulman Institute of Technology (Terre Haute, IN, USA). Statistical analysis was performed at Joint Replacement Surgeons of Indiana Foundation, Inc (Mooresville, IN, USA).