RESUMEN
PURPOSE: New repair techniques for fragility fractures such as those of the distal radius require biomechanical justification. This study was conducted to investigate a technique using an expanding polymer bone cement to provide strength to a fracture repair. METHODS: Distal and proximal ends were isolated from 6 pairs of human radii (mean age 65). Transverse osteotomies were made near the head of each specimen. Paired specimens were repaired using 2 materials of differing polymer chemistries: polyurethane versus polymethylmethacrylate. Repaired specimens were subjected to failure tests in a cantilever beam configuration (distal, n = 6 per treatment) or pure tension (proximal, n = 5 per treatment). Cement penetration tests were conducted using a uniform open-cell model of cancellous bone. Baseline mechanical properties of the polyurethane cement were determined according to ASTM standards. RESULTS: Distal radii repaired with polyurethane bone cement withstood average shear stress 2.9 times as high as polymethylmethacrylate (0.91 vs 0.31 MPa). Peak tensile bending stress was 2.5 times as high in polyurethane (2.57 vs 1.02 MPa). Under pure tension, polyurethane-repaired samples failed at 0.83 MPa versus 0.74 MPa for polymethylmethacrylate. The polyurethane cement expanded to penetrate 49% farther into the trabeculae. The polyurethane cement had mean compressive yield stress of 20.3 MPa, compressive modulus of 754 MPa, ultimate tensile stress of 18.5 MPa, and tensile elastic modulus of 723 MPa. CONCLUSIONS: The biomechanical strength data indicate the potential of an expanding bone cement as a candidate strategy for fracture repair. Further evaluation might provide evidence for such an alternative repair strategy for fragility fractures, including those of the distal radius.
Asunto(s)
Cementos para Huesos/química , Fijación Interna de Fracturas/métodos , Poliuretanos/química , Fracturas del Radio/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Cadáver , Femenino , Humanos , Masculino , Persona de Mediana Edad , Polimetil Metacrilato/química , Estrés MecánicoRESUMEN
BACKGROUND: Wire cerclage closure of sternotomy is the standard of care despite evidence of pathologic sternal displacement (> 2 mm) during physiologic distracting forces (coughing). Postoperative functional recovery, respiration, pain, sternal dehiscence, and infection are influenced by early bone stability. This translational research report provides proof-of-concept (part A) and first-in-man clinical data (part B) with use of a triglyceride-based porous adhesive to rapidly enhance the stability of conventional sternal closure. METHODS: In part A, fresh human cadaver blocks were subjected to midline sternotomy and either conventional wire closure or modified adhesive closure. After 24 hours at 37 degrees C, using a biomechanical test apparatus, a step-wise increase in lateral distracting force simulated physiologic stress. Sternal displacement was measured by microdisplacement sensors. In part B, a selected clinical case series was performed and sternal perfusion assessed by serial single photon emission computed tomography imaging. RESULTS: Wire closure resulted in measurable bony displacement with increasing load. Pathologic displacement (> or = 2 mm) was observed in all regional segments at loads 400 newton (N) or greater. In contrast, adhesive closure completely eliminated pathologic displacement at forces 600 N or less (p < 0.001). In patients, adhesive closure was not associated with adverse events such as adhesive migration, embolization, or infection. There was excellent qualitative correlation between cadaver and clinical computed tomographic images. Sternal perfusion was not compromised by adhesive closure. CONCLUSIONS: This first-in-man series provides proof-of-concept indicating that a novel biologic bone adhesive is capable of rapid sternal fixation and complete elimination of pathologic sternal displacement under physiologic loading conditions. A randomized clinical trial is warranted to further define the potential risks and benefits of this innovative technique.