Simulating activities of daily living with finite element analysis improves fracture prediction for patients with metastatic femoral lesions

Abstract

Predicting fracture risk for patients with metastatic femoral lesions remains an important clinical problem. Mirels' criterion remains the most formalized radiographic scoring system with good sensitivity (correctly identifying clinical fractures) but relatively poor specificity (correctly identify cases that d8o not fracture). A series of patients with metastatic femoral lesions had Computed Tomography (CT) scans, were followed prospectively for 4 months, and categorized into fracture (n ¼ 5), nonfracture (n ¼ 28), or stabilized (n ¼ 11) groups. CT based-Finite Element (FE) modeling was used to predict fracture for these cases using axial compression (AC), level walking (LW), and aggressive stair ascent (ASA) loading conditions. The FE predicted fracture force was greater for the non-fracture compared to the fracture group for all loading cases. The ability of the FE models to predict fracture cases (sensitivity) was similar for the groups (Mirels, AC, LW: 80%, ASA: 100%). The ability of the models to correctly predict the nonfracture cases (specificity) was improved for AC (71%) and LW (86%) loading conditions, when compared to Mirels specificity (43%), but poorer for the ASA (21%) conditions. The results suggest that FE models that assess fracture risk using LW conditions can improve fracture prediction over Mirels scoring in a clinical population. Keywords: fracture prediction; metastatic; femur; finite element; Mirels score Prophylactic stabilization is sometimes needed for patients with metastatic femoral lesions, but correctly identifying cases that are at risk of fracture remains a clinical challenge. This determination is based on the clinician's assessment of radiographs and prior experience. Mirels' criterion remains the most formalized radiographic scoring system. [1][2][3][4] It has good sensitivity (correctly identifying patients that do go on to fracture) but poor specificity (predicts that patients will fracture, when in fact they don't). Clearly, improved efforts are needed to avoid unnecessary fracture in those at high risk and unnecessary surgery in those at low risk.Computed Tomography (CT)-based finite element (FE) modeling has been used to assess fracture risk of the femur for fragility fractures 5-7 and shows improvement in fracture prediction over standard bone density measures.8 FE modeling has also been used to estimate fracture risk for femoral metastatic lesions, but these comparisons have been made using cadavers with laboratory created defects.9,10 CT-based finite element modeling has the potential to improve fracture risk assessment, but this has not been performed on a patient population with metastatic disease.In this study, we performed non-linear FE analysis for a series of clinical cases with disseminated tumors to the femur and known clinical outcomes (fracture, no fracture, or prophylactic stabilization). We asked three research questions: (1) Does a CT-based FE modeling approach discriminate bone strength between the fracture and no fracture patient groups? (2) Do...

Can patient-specific finite element models better predict fractures in metastatic bone disease than experienced clinicians?

“…Nevertheless, the results from institute 1 show that FE models were able to comprehend many factors that contribute to the in vivo load capacity of metastatic femurs, such as the bone quality and the bone geometry, or compromise it, such as the location and the size of the lesion. Goodheart et al 10 recently found that FE models can be used to distinguish between metastatic femurs that would and would not fracture. Positive findings were also shown in the field of osteoporosis (e.g.…”

“… 5 A potential tool to improve clinical fracture risk assessments is finite element (FE) modelling, which has been shown to predict human femoral bone strength fairly accurately. 6 - 10 Our group have shown that the FE model accurately calculated failure load and fairly predicted fracture locations in cadaver femurs with and without artificial lesions compared with mechanical experiments. 11 - 13 Moreover, we demonstrated that ranking on FE failure load better resembled the experimentally measured failure loads than rankings by experienced clinicians.…”

Considerations for Exercise Prescription in Patients With Bone Metastases: A Comprehensive Narrative Review

“…A number of recent studies have investigated the value of CT based‐Finite Element 3‐dimensional modeling and CT‐based structural rigidity analysis in predicting fractures. Both methods may considerably advance the accuracy of pathologic femur fracture prediction [56,57]; however, in clinical practice, where this level of radiologic analysis is not available, Mirels' classification can provide an extremely meaningful and cost‐effective measure of fracture risk.…”

Effect of different CT scanners and settings on femoral failure loads calculated by finite element models

“…The subject‐specific geometry and BMD are used as input for the FE models. Recently, studies using FE models showed promising results in discriminating patients with a low fracture risk from patients with a high fracture risk …”