Sternal Closure Using Rigid Plate Fixation: Design Improvements For Enhanced Patient Recovery
Keith B. Allen1, Marc Gerdisch2, Val Jeevandam3, Isaac George4, Nadir Sarkis1.
1St. Luke's Hospital, The Mid America Heart Institute, Kansas City, MO, USA, 2Franciscan Health, Indianapolis, IN, USA, 3University of Chicago, Chicago, IL, USA, 4New York Presbyterian Hospital, Columbia University Medical Center, New York, NY, USA.
BACKGROUND:In a multicenter randomized trial, sternotomy closure using rigid plate fixation (RPF) demonstrated improved bone healing, reduced sternal complications, improved postoperative quality of life and decreased pain scores while being cost neutral through 6-months follow-up compared to wire cerclage. Continued innovation is required to improve implant speed and increase the strength of the current legacy RPF construct. This bench top study evaluated the biomechanical properties of a next generation RPF system
METHODS: Biomechanical bench testing in a simulated sternotomy model compared the threshold for failure of a next generation RPF system that incorporates an integrated amorphous cable (SternaLock XP, Zimmer Biomet, Jacksonville, FL) to the legacy plating system without cable integration (SternaLock Blu, Zimmer Biomet, Jacksonville, FL). The amorphous band looks and drives like a wire, however, when tightened it flattens into a broader cerclage band to increase surface area and resist pull through. Lateral stiffness/fatigue tests were performed by applying cyclic load in a uniaxial direction for 200K cycles. Failure of the test constructs was defined as lateral distraction exceeding 2mm sternal displacement. In addition, design improvements that improve ease of use and facilitate faster screw delivery and better screw engagement were evaluated (SternaLock EZ, Zimmer Biomet, Jacksonville, FL).
RESULTS: SternaLock XP with an integrated amorphous cable cerclage performed significantly better and was 50% stronger compared to the legacy RPF system alone (Fig 1). SternaLock EZ’s compared to the legacy RPF system was 15% stronger and should be easier to use with faster implants and better screw engagement through its enhanced implant instruments and features (Fig 1). 
CONCLUSIONS: Design enhancements over a current legacy RPF system may make RPF easier and faster while incorporation of an integrated amorphous cable with the plate provides a significantly stronger construct making it suitable for patients who require a very robust construct (morbidly obesity/dense bone).
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