Patient-specific Hip Fracture Strength Assessment with Microstructural MR Imaging–based Finite Element Modeling

Abstract

Purpose To describe a nonlinear finite element analysis method by using magnetic resonance (MR) images for the assessment of the mechanical competence of the hip and to demonstrate the reproducibility of the tool. Materials and Methods This prospective study received institutional review board approval and fully complied with HIPAA regulations for patient data. Written informed consent was obtained from all subjects. A nonlinear finite element analysis method was developed to estimate mechanical parameters that relate to hip fracture resistance by using MR images. Twenty-three women (mean age ± standard deviation, 61.7 years ± 13.8) were recruited from a single osteoporosis center. To thoroughly assess the reproducibility of the finite element method, three separate analyses were performed: a test-retest reproducibility analysis, where each of the first 13 subjects underwent MR imaging on three separate occasions to determine longitudinal variability, and an intra- and interoperator reproducibility analysis, where a single examination was performed in each of the next 10 subjects and four operators independently performed the analysis two times in each of the subjects. Reproducibility of parameters that reflect fracture resistance was assessed by using the intraclass correlation coefficient and the coefficient of variation. Results For test-retest reproducibility analysis and inter- and intraoperator analyses for proximal femur stiffness, yield strain, yield load, ultimate strain, ultimate load, resilience, and toughness in both stance and sideways-fall loading configurations each had an individual median coefficient of variation of less than 10%. Additionally, all measures had an intraclass correlation coefficient higher than 0.99. Conclusion This experiment demonstrates that the finite element analysis model can consistently and reliably provide fracture risk information on correctly segmented bone images. RSNA, 2016 Online supplemental material is available for this article.

Patient-Specific Bone Multiscale Modelling, Fracture Simulation and Risk Analysis—A Survey

“…CT is not the only medical imaging technique able to quantify vBMD. MRI-images, though not as suited to estimate bone density as CT-images [150,277], were used to accurately quantify in vivo vBMD of a patella by [278] and to estimate CLE-properties [48,131].…”

“…Terms such as nonlinear analysis may be misleading. For instance, [99,101,131] speak of non-linear analysis, but do not specify the type or source of non-linearity. There are mainly four types/sources of non-linearity in a solid continuum mechanics problem [302] (p. 85), [303] (p. 8): (1.)…”

MRI assessment of bone structure and microarchitecture

“…Finally, Rajapakse et al showed that it is now possible to assess MRI‐based strength measures at the level of the whole proximal femur with high reproducibility in vivo using nonlinear FEA . Median CVs/ICCs for the several parameters computed including yield strain, yield load, ultimate strain, ultimate load, resilience, and toughness were <8% with ICCs of 0.99.…”

Is there a practical role for a virtual bone biopsy using high‐resolution imaging of bone in patients with chronic kidney disease?

“…In addition to correlating bone strength with its microarchitecture, bone mechanical properties assessed by FEA may provide information about skeletal fragility and fracture risk, independent of BMD or architecture measurements, and add another potential method of assessing bone vulnerability . Recently Rajapakse et al described a reproducible FEA method by using MRI to estimate mechanical parameters that relate to hip fracture resistance. This method is an attractive future proposition, and particularly relevant to a population with advanced CKD and high rates of hip fractures…”