Stiffness and Strength Predictions From Finite Element Models of the Knee are Associated with Lower-Limb Fractures After
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Annals of Biomedical Engineering ( 2020) https://doi.org/10.1007/s10439-020-02606-w
Original Article
Stiffness and Strength Predictions From Finite Element Models of the Knee are Associated with Lower-Limb Fractures After Spinal Cord Injury IFAZ T. HAIDER,1,2 NARINA SIMONIAN,3,4 THOMAS J. SCHNITZER,3 and W. BRENT EDWARDS1,2 1 Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada; 2McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Canada; 3Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, USA; and 4Northwestern University Clinical and Translational Sciences Institute, Northwestern University Feinberg School of Medicine, Chicago, USA
(Received 1 June 2020; accepted 2 September 2020) Associate Editor Eiji Tanaka oversaw the review of this article.
Abstract—Spinal cord injury (SCI) is associated with bone fragility and fractures around the knee. The purpose of this investigation was to validate a computed tomography (CT) based finite element (FE) model of the proximal tibia and distal femur under biaxial loading, and to retrospectively quantify the relationship between model predictions and fracture incidence. Twenty-six cadaveric tibiae and femora (n = 13 each) were loaded to 300 N of compression, then internally rotated until failure. FE predictions of torsional stiffness (K) and strength (Tult) explained 74% (n = 26) and 93% (n = 7) of the variation in experimental measurements, respectively. Univariate analysis and logistic regression were subsequently used to determine if FE predictions and radiographic measurements from CT and dual energy Xray absorptiometry (DXA) were associated with prevalent lower-limb fracture in 50 individuals with SCI (n = 14 fractures). FE and CT measures, but not DXA, were lower in individuals with fracture. FE predictions of Tult at the tibia demonstrated the highest odds ratio (4.98; p = 0.006) and receiver operating characteristic (0.84; p = 0.008) but did not significantly outperform other metrics. In conclusion, CT-based FE model predictions were associated with prevalent fracture risk after SCI; this technique could be a powerful tool in future clinical research. Keywords—Biomechanics, Fracture risk, Computed tomography, Disuse osteoporosis.
Address correspondence to Ifaz T. Haider, Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada. Electronic mail: [email protected]
INTRODUCTION Sublesional bone loss is a recognized consequence of spinal cord injury (SCI). Losses are most severe around regions of the knee, with reductions in bone mineral up to 50% within the first 5 years after SCI.3,13,16 Reductions in bone mineral are associated with increased skeletal fragility, resulting in fractures of the proximal tibia and distal femur during routine activities, such as wheelchair transfers and rolling over in bed.27,44 These fractures are associated with a high rate of complication and concomitant increase in mo
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