Pullout strength of suture anchors: Effect of mechanical properties of trabecular bone

Abstract

This study investigated the relationships between trabecular microstructure and elastic modulus, compressive strength, and suture anchor pullout strength. Twelve fresh-frozen humeri underwent mechanical testing followed by micro-computed tomography (μCT). Either compression testing of cylindrical bone samples or pullout testing using an Arthrex 5 mm Corkscrew was performed in synthetic sawbone or at specific locations in the humerus such as the greater tuberosity, lesser tuberosity, and humeral head. Synthetic sawbone underwent identical mechanical testing and μCT analysis. Bone volume fraction (BVF), structural model index (SMI), trabecular thickness (TbTh), trabecular spacing (TbSp), trabecular number (TbN), and connectivity density were compared against modulus, compressive strength, and pullout strength in both materials. In cadaveric bone, modulus showed correlations to all of the microstructural properties, while compressive and pullout strength were only correlated to BVF, SMI, and TbSp. The microstructure of synthetic bone differed from cadaveric bone as SMI and TbTh showed little variation across the densities tested. Therefore, SMI and TbTh were the only microstructural properties that did not show correlations to the mechanical properties tested in synthetic bone. This study helps identify key microstructure-property relationships in cadaveric and synthetic bone as well as illustrate the similarities and differences between cadaveric and synthetic bone as biomechanical test materials.

Experimental and numerical characterisation of the elasto-plastic properties of bovine trabecular bone and a trabecular bone analogue

“…Solid PU and cellular PU are commonly used to synthesise trabecular bone for the biomechanical testing of implants (Agneskirchner et al, 2006;Poukalova et al, 2010;Cawley et al, 2011). An accurate representation of its elasto-plastic behaviour is essential in assessing its suitability as a test material substitute for trabecular bone for applications in which large deformation occurs (e.g.…”

“…Its material properties are dependent on many factors including density, age, sex, species, geometry and anatomic site (Goldstein, 1987;Keaveny et al, 1993b;Morgan et al, 2003). Both cellular rigid and solid rigid polyurethane foam (PU), commercially available trabecular bone analogue materials (Sawbones, Pacific Research Labs, Malmö, Sweden), have been widely used as trabecular bone substitutes in biomechanical testing (Agneskirchner et al, 2006;Poukalova et al, 2010;Cawley et al, 2011). A range of rigid closed cell PU foams (grades 5 -50, ρ = 0.08 -0.8 g/cm 3 ) have been identified in ASTM F1839-08 (ASTM, 2008).…”

Anterior cruciate ligament fixation: Is radial force a predictor of the pullout strength of soft-tissue interference devices?

“…Whereas large deviations in the pullout strengths have been reported when interference devices are tested in either cadaveric or porcine tibiae due to the specimen-to-specimen variability in density and mechanical properties of cancellous bone [14,29], synthetic bone offers a consistent test medium that has uniform density and material properties, effectively minimizing the deviation in data collected [13,14,29]. Strong correlations in pullout strength between synthetic and cadaver bone have also been previously reported with biomechanical testing of suture anchors used for rotator cuff repair [14,30]. An additional advantage is that the density of synthetic bone can be matched to the density of bone under investigation.…”

Button Fixation Technique for Achilles Tendon Reinsertion: A Biomechanical Study

“…First, the results we obtained with the anchors might have been better in cadaver specimens from younger subjects, because the median age of our cadaver samples was 72 and 76 years old (14). Potential osteoporosis could have affected the anchor assemblies more than the button assembly.…”