title: Comparison of microCT and an inverse finite element approach for biomechanical analysis: results in a mesenchymal stem cell therapeutic system for fracture healing.
abstract: An important concern in the study of fracture healing is the ability to assess mechanical integrity in response to candidate therapeutics in small-animal systems. In recent reports, it has been proposed that microCT image-derived densitometric parameters could be used as a surrogate for mechanical property assessment. Recently, we have proposed an inverse methodology that iteratively reconstructs the modulus of elasticity of the lumped soft callus/hard callus region by integrating both intrinsic mechanical property (from biomechanical testing) and geometrical information (from microCT) within an inverse finite element analysis (FEA) to define a callus quality measure. In this paper, data from a therapeutic system involving mesenchymal stem cells is analyzed within the context of comparing traditional microCT densitometric and mechanical property metrics. In addition, a novel multi-parameter regression microCT parameter is analyzed as well as our inverse FEA metric. The results demonstrate that the inverse FEA approach was the only metric to successfully detect both longitudinal and therapeutic responses. While the most promising microCT-based metrics were adequate at early healing states, they failed to track late-stage mechanical integrity. In addition, our analysis added insight to the role of MSCs by demonstrating accelerated healing and was the only metric to demonstrate therapeutic benefits at late-stage healing. In conclusion, the work presented here indicates that microCT densitometric parameters are an incomplete surrogate for mechanical integrity. Additionally, our inverse FEA approach is shown to be very sensitive and may provide a first-step towards normalizing the often challenging process of assessing mechanical integrity of healing fractures.
authors: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, USA.
authors: Jared A
authors: JA
authors: Weis
authors: Froilán
authors: F
authors: Granero-Moltó
authors: Timothy J
authors: TJ
authors: Myers
authors: Lara
authors: L
authors: Longobardi
authors: Anna
authors: A
authors: Spagnoli
authors: Michael I
authors: MI
authors: Miga
mesh_terms: D000818:Animals; D015519:Bone Density; D002146:Bony Callus / Q000000981:diagnostic imaging / Q000378:metabolism; D055119:Elastic Modulus; D005260:Female; D020342:Finite Element Analysis; D017102:Fracture Healing; D050723:Fractures, Bone / Q000000981:diagnostic imaging; D045164:Mesenchymal Stem Cell Transplantation; D051379:Mice; D014184:Transplantation, Homologous; D055114:X-Ray Microtomography