A mechanical and computational investigation on the effects of conduit orientation on the strength of massive bone allografts Brandon G. Santoni a,b, ⁎ , Wesley J. Womack b , Donna L. Wheeler c , Christian M. Puttlitz b a Department of Clinical Sciences, Animal Cancer Center, Colorado State University, Fort Collins, CO 80523, USA b Department of Mechanical Engineering, Orthopaedic Bioengineering Research Laboratory, Colorado State University, Fort Collins, CO 80523, USA c BioSolutions Consulting, 385 Coastal View Drive, Webster, NY 14580, USA Received 9 March 2007; revised 8 June 2007; accepted 7 July 2007 Available online 24 July 2007 Abstract Structural bone allografts are used to reconstruct large skeletal defects resulting from trauma, tumor resection, or revision arthroplasty. Though used for over a century, bone allografts suffer from a high rate of mechanical failure due to limited graft revitalization even after extended periods in vivo. The current study evaluated the mechanical properties of longitudinally perforated cortical bone allografts (LAP) that have been shown to promote accelerated graft incorporation in a large animal model. The compressive and tensile properties of longitudinally perforated allograft specimens, as determined through uniaxial compression and diametral compression tests, respectively, were not significantly affected by the presence of the conduit. However, transversely perforated grafts (TAP) demonstrated a marked decrease in tensile capacity (p = 0.04). Finite element analysis demonstrated moderate increases in the maximum principal stresses in LAP specimens while TAP models indicated an 83.4% increase in maximum principle stress near the conduit on the endosteal surface of the graft. This research and the previous in vivo study suggest that LAP adequately serves as an internal template within the cortical bone allograft for osseous apposition and revitalization without adversely affecting the structural or mechanical integrity of the graft. © 2007 Elsevier Inc. All rights reserved. Keywords: Bone allograft; Perforation; Biomechanics; Diametral compression; Finite element analysis Introduction Massive allograft bone is the primary source of bone graft material for use in limb salvage procedures after tumor resection. However, allograft bone has been found to incorpo- rate slowly into the host even after 10 years in vivo. The lack of graft revitalization, reported to be as little as 20% of the graft 5 years post-transplantation [8,9], has lead to a complication rate approaching 50% at 10 years [1,20,21,25,27,36], with the largest constituent being mechanical in nature. Non-union at the host–graft interface [14], allograft fracture at fixation points [1,36], and fatigue failure of the allograft due to microfracture accumulation [41] illustrate that accelerating allograft incorpo- ration will reduce the frequency and severity of allograft- associated complications and improve the long-term clinical outcome of patients requiring structural allografts. Prior in vivo research has investigated increasing the cortical porosity of structural bone allografts as a means to increase access to surrounding vascularity and accelerate healing [7,11,17,18,24]. These studies have demonstrated that perforating the graft cortex perpendicular to its long axis alone or in combination with cortical demineralization may improve revitalization and the clinical course of graft incorporation. Though reports of improved revitalization in animal models employing only transverse allograft perforations are mixed in the literature [7,19,24,38], studies combining transverse perforation with additional cortical demineralization have consistently enhanced graft integration. Despite histologic reports of accelerated revitalization of these grafts by Lewandrowski et al. [17,18] and O'Donnel et al. [24], more recent reports have indicated a significant deleterious effect Bone 41 (2007) 769 – 774 www.elsevier.com/locate/bone ⁎ Corresponding author. Musculoskeletal Oncology Research Fellow, Animal Cancer Center, James L. Voss Veterinary Medical Center, Colorado State University, Fort Collins, CO 80523-1620, USA. Fax: +1 970 297 1254. E-mail address: bgsant@engr.colostate.edu (B.G. Santoni). 8756-3282/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.bone.2007.07.011