, Volume 471, Issue 2, pp 519-526
Date: 07 Sep 2012

What Factors Affect Posterior Dislocation Distance in THA?

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Abstract

Background

Dislocation remains common after total hip arthroplasty. Efforts have been made to identify and minimize risk factors. One such factor, jump distance, or the distance the femoral head must travel before dislocating, has been poorly characterized with respect to three-dimensional kinematics.

Questions/purposes

We therefore determined: (1) the three-dimensional stability of four different component designs; (2) whether the degree of abduction and anteversion affects the stability; (3) whether pelvic inclination angles affected stability; and (4) which combination of these three factors had the greatest stability.

Methods

We created a positionable three-dimensional model of a THA. Acetabular components were modeled in various abduction and anteversion angles and in two different pelvic inclinations which simulate standing and chair-rising activities.

Results

The posterior horizontal dislocation distance increased as inclination angle and femoral head size increased. The 48-mm resurfacing typically had lower jump distances and was at risk of posterior edge loading at 30° inclination. The highest jump distance for all positions and activities occurred with the dual-mobility bearing.

Conclusion

These findings suggest that monoblock cups require extremely accurate positioning for low dislocation risk and that pelvic orientation may increase dislocation risks.

Clinical Relevance

As a result of the dual-mobility designs having the greatest resistance to dislocation, these cups may be appropriate for patients who are at risk for dislocation in difficult primary situations and in revision hip arthroplasty procedures in which proper component orientation may be less likely to be achieved.

Three of the authors (JN, CH, JM) certify that they are employees of Stryker Orthopaedics (Mahwah, NJ, USA). Two of the authors (MAM, DCM) certify that they have or may receive payments or benefits, in any one year, an amount in excess of $10,000 from Stryker Orthopaedics in connection with the submitted article. The remaining author (AJJ) certifies that he, or a member of his immediate family, has no commercial associations that might pose a conflict of interest in connection with the submitted article. No institutions received funding from any commercial entity in support of this work.
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 prior to clinical use.
This work was performed at either Stryker Orthopaedics, Mahwah, NJ, USA, or at Sinai Hospital of Baltimore, Baltimore, MD, USA