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In-vivo Quantification of Dorsal Collapse during Fracture Healing of the Distal Radius
Registered, time-lapse in-vivo images of distal radius fractures provide the opportunity to investigate the link between the micromechanical environment and undesired patient outcomes (i.e. dorsal tilt, shortening of the radius, etc.) within the first year post-fracture.
Keywords: Fracture healing, in-vivo imaging, HRpQCT, micro-finite element analysis
Fractures of the distal radius account for more than 20% of all emergency room fracture cases [1]. Despite this high incidence, the course of treatment for these types of fractures remains under debate. In particular, the choice of reduction method in cases which do not require surgical intervention. In these cases, physicians will prescribe one of two methods for closed reduction of the displaced fractures, manual reduction (MR) or finger trap reduction (FTR). Typically, the distal radius has a volar tilt of 0 to 22 degrees. Crushing fractures of the distal radius, a common result of a fall onto an outstretched hand, introduces a significant dorsal tilt (Figure 1). As a dorsal tilt of greater than 11 degrees is associated with a loss of grip strength and wrist flexion [2], a reduction of the fracture site is performed in order try to re-establish a volar tilt. A recent systemic review of these methods concluded that further research was necessary to determine which method achieves the best outcome, particularly concerning the MR method as it is can be painful for the patients [3]. Moreover, recent work suggests that dorsal collapse of the radius occurs during the early stages of fracture healing despite the initial reduction and stabilization of the fracture.
Clinically, fracture healing is assessed through either sequential x-rays or computed tomography (CT) images. Of these, only CT data captures the 3D environment. While traditional CT does not provide the fidelity necessary to quantify microstructural changes, high resolution peripheral quantitative CT (HR-pQCT) offers a unique platform to evaluate bone health at peripheral joints, such as the human hand and wrist. Several studies have shown that HRpQCT-based micro-finite element (microFE) models can be used to assess the local mechanical environment of the distal radius in healthy, osteoporotic, and fracture healing patients. However, no studies have investigated the relationship between the local mechanical environment and distal radius fracture stability.
As a part of a multinational collaboration, we have acquired one of the most extensive patient data sets tracking in-vivo fracture healing of the distal radius. At six time points within the first year after fracture, we have collected HR-pQCT, dual energy x-ray absorptiometry (DXA), and x-ray images as well as blood samples. By evaluating changes in the local strains of the HRpQCT-based microFE models over time, we hope to identify regions susceptible to collapse. Combining this information with the dorsal tilt measurements taken clinically from the x-ray images may enable us to predict the long term effects of MR and FTR.
[1] Grewal R, et al., J Hand Surg [Am] 20, 764 (2005)
[2] Court-Brown C, et al., Wolters Kluwer Health (2014)
[3] Sosborg-Würtz, et al., EFFORT Open Rev 3(4), 114-120 (2018)
Fractures of the distal radius account for more than 20% of all emergency room fracture cases [1]. Despite this high incidence, the course of treatment for these types of fractures remains under debate. In particular, the choice of reduction method in cases which do not require surgical intervention. In these cases, physicians will prescribe one of two methods for closed reduction of the displaced fractures, manual reduction (MR) or finger trap reduction (FTR). Typically, the distal radius has a volar tilt of 0 to 22 degrees. Crushing fractures of the distal radius, a common result of a fall onto an outstretched hand, introduces a significant dorsal tilt (Figure 1). As a dorsal tilt of greater than 11 degrees is associated with a loss of grip strength and wrist flexion [2], a reduction of the fracture site is performed in order try to re-establish a volar tilt. A recent systemic review of these methods concluded that further research was necessary to determine which method achieves the best outcome, particularly concerning the MR method as it is can be painful for the patients [3]. Moreover, recent work suggests that dorsal collapse of the radius occurs during the early stages of fracture healing despite the initial reduction and stabilization of the fracture. Clinically, fracture healing is assessed through either sequential x-rays or computed tomography (CT) images. Of these, only CT data captures the 3D environment. While traditional CT does not provide the fidelity necessary to quantify microstructural changes, high resolution peripheral quantitative CT (HR-pQCT) offers a unique platform to evaluate bone health at peripheral joints, such as the human hand and wrist. Several studies have shown that HRpQCT-based micro-finite element (microFE) models can be used to assess the local mechanical environment of the distal radius in healthy, osteoporotic, and fracture healing patients. However, no studies have investigated the relationship between the local mechanical environment and distal radius fracture stability. As a part of a multinational collaboration, we have acquired one of the most extensive patient data sets tracking in-vivo fracture healing of the distal radius. At six time points within the first year after fracture, we have collected HR-pQCT, dual energy x-ray absorptiometry (DXA), and x-ray images as well as blood samples. By evaluating changes in the local strains of the HRpQCT-based microFE models over time, we hope to identify regions susceptible to collapse. Combining this information with the dorsal tilt measurements taken clinically from the x-ray images may enable us to predict the long term effects of MR and FTR.
[1] Grewal R, et al., J Hand Surg [Am] 20, 764 (2005) [2] Court-Brown C, et al., Wolters Kluwer Health (2014) [3] Sosborg-Würtz, et al., EFFORT Open Rev 3(4), 114-120 (2018)
To determine if in-vivo local strains can be used to predict dorsal tilt of the distal radius during fracture healing, following either MR or FTR. The student will establish and apply a segmentation protocol to isolate the dorsal region of the radius and evaluate the strain distributions over time from the results of time-lapsed, in-vivo micro-finite element analyses. Students with interest or experience in biomedical engineering and python programming are encouraged to apply.
To determine if in-vivo local strains can be used to predict dorsal tilt of the distal radius during fracture healing, following either MR or FTR. The student will establish and apply a segmentation protocol to isolate the dorsal region of the radius and evaluate the strain distributions over time from the results of time-lapsed, in-vivo micro-finite element analyses. Students with interest or experience in biomedical engineering and python programming are encouraged to apply.
Caitlyn Collins (caitlyn.collins@hest.ethz.ch), Institute for Biomechanics, ETH Zurich, Professorship Ralph Müller
Caitlyn Collins (caitlyn.collins@hest.ethz.ch), Institute for Biomechanics, ETH Zurich, Professorship Ralph Müller