Trunnion Troubles in Modular Hip Implants.

Abstract

As outlined in our January 16, 2013 editorial, “The Case Report Redefined with JBJS Case Connector , ” one important role of JBJS Case Connector is to alert the orthopaedic community about a potentially problematic device or therapy. When two or more such cases with similar mechanisms appear, we will identify the procedure or implant as a “watchable” intervention. While this system is not statistically conclusive and may or may not be supported by other published case reports or registry data, the intention is to sharpen the focus of clinicians on the potential for similar problems and thereby enhance clinical outcomes and patient safety. The “Watch” designation may also encourage others to report related difficulties and enlist the orthopaedic community to either demonstrate that these are isolated, unrelated cases or sharpen the focus further on rigorously evaluating the intervention. Where appropriate, we may identify brand, model, or implant-lot specifics. Of the five Watch articles that have been published in JBJS Case Connector, three—including this one—have focused on total hip arthroplasty (THA). Our very first Watch in September 2013 discouraged surgeons who implant dual-mobility hips from using a “mix-and-match” strategy with components from different manufacturers. Our January 2014 Watch about THA cautioned hip surgeons to be wary about using long-necked and skirted-head modular hip designs. In both of those Watch articles, we emphasized how head-neck modularity has helped orthopaedists achieve important biomechanical objectives—such as adjusting version, limb length, and offset—to maximize implant function and longevity. Modularity also facilitates easier revisions and lowers inventory costs. But we also made the point that modularity increases the number of interfaces at which corrosion can occur, making prosthetic materials more vulnerable to compression, shear forces, and bending stresses. The arthroplasty community currently feels that the advantages gained from modularity outweigh the risks, but we …