Mesh-based vs. Image-based Statistical Appearance Model of the Human Femur: a Preliminary Comparison Study for the Creation of Finite Element Meshes

Statistical models have been recently introduced in computational orthopaedics to investigate the bone mechanical properties across several populations. A fundamental aspect for the construction of statistical models concerns the establishment of accurate anatomical correspondences among the objects of the training dataset. Various methods have been proposed to solve this problem such as mesh morphing or image registration algorithms. The objective of this study is to compare a mesh-based and an image-based statistical appearance model approaches for the creation of nite element(FE) meshes. A computer tomography (CT) dataset of 157 human left femurs was used for the comparison. For each approach, 30 finite element meshes were generated with the models. The quality of the obtained FE meshes was evaluated in terms of volume, size and shape of the elements. Results showed that the quality of the meshes obtained with the image-based approach was higher than the quality of the mesh-based approach. Future studies are required to evaluate the impact of this finding on the final mechanical simulations.

Femur Specific Polyaffine Model to Regularize the Log-Domain Demons Registration

Osteoarticular allograft transplantation is a popular treatment method in wide surgical resections with large defects. For this reason hospitals are building bone data banks. Performing the optimal allograft selection on bone banks is crucial to the surgical outcome and patient recovery. However, current approaches are very time consuming hindering an efficient selection. We present an automatic method based on registration of femur bones to overcome this limitation. We introduce a new regularization term for the log-domain demons algorithm. This term replaces the standard Gaussian smoothing with a femur specific polyaffine model. The polyaffine femur model is constructed with two affine (femoral head and condyles) and one rigid (shaft) transformation. Our main contribution in this paper is to show that the demons algorithm can be improved in specific cases with an appropriate model. We are not trying to find the most optimal polyaffine model of the femur, but the simplest model with a minimal number of parameters. There is no need to optimize for different number of regions, boundaries and choice of weights, since this fine tuning will be done automatically by a final demons relaxation step with Gaussian smoothing. The newly developed synthesis approach provides a clear anatomically motivated modeling contribution through the specific three component transformation model, and clearly shows a performance improvement (in terms of anatomical meaningful correspondences) on 146 CT images of femurs compared to a standard multiresolution demons. In addition, this simple model improves the robustness of the demons while preserving its accuracy. The ground truth are manual measurements performed by medical experts.

Personalized X-Ray Reconstruction of the Proximal Femur via Intensity-Based Non-rigid 2D-3D Registration

This paper presents a new approach for reconstructing a patient-specific shape model and internal relative intensity distribution of the proximal femur from a limited number (e.g., 2) of calibrated C-arm images or X-ray radiographs. Our approach uses independent shape and appearance models that are learned from a set of training data to encode the a priori information about the proximal femur. An intensity-based non-rigid 2D-3D registration algorithm is then proposed to deformably fit the learned models to the input images. The fitting is conducted iteratively by minimizing the dissimilarity between the input images and the associated digitally reconstructed radiographs of the learned models together with regularization terms encoding the strain energy of the forward deformation and the smoothness of the inverse deformation. Comprehensive experiments conducted on images of cadaveric femurs and on clinical datasets demonstrate the efficacy of the present approach.

Occurrence, types and severity of associated injuries of paediatric patients with fractures of the frontal skull base

To clarify the occurrence, sites, and types of associated injuries in paediatric patients with fractures of the anterior skull base.

Safety, effectiveness and predictors for early reoperation in therapeutic and prophylactic vertebroplasty: short-term results of a prospective case series of patients with osteoporotic vertebral fractures

Abstract Introduction Vertebroplasty (VP) is a cost-efficient alternative to kyphoplasty; however, regarding safety and vertebral body (VB) height restoration, it is considered inferior. We assessed the safety and efficacy of VP in alleviating pain, improving quality of life (QoL) and restoring alignment. Methods In a prospective monocenter case series from May 2007 until July 2008, there were 1,408 vertebroplasties performed during 319 interventions in 306 patients with traumatic, lytic and osteoporotic fractures. The 249 interventions in 233 patients performed because of osteoporotic vertebral fractures were analyzed regarding demographics, treatment and radiographic details, pain alleviation (VAS), QoL improvement (NASS and EQ-5D), complications and predictors for new fractures requiring a reoperation. Results The osteoporotic patient sample consisted of 76.7% (179) females with a median age of 80 years. A total of 54 males had a median age of 77 years. On average, there were 1.8 VBs fractured and 5 VBs treated. The preoperative pain was assessed by the visual analog scale (VAS) and decreased from 54.9 to 40.4 pts after 2 months and 31.2 pts after 6 months. Accordingly, the QoL on the EQ-5D measure (−0.6 to 1) improved from 0.35 pts before surgery to 0.56 pts after 2 and to 0.68 pts after 6 months. The preoperative Beck Index (anterior height/posterior height) improved from a mean of 0.64 preoperative to 0.76 postoperative, remained stable at 2 months and slightly deteriorated to 0.72 at 6 months postoperatively. There were cement leakages in 26% of the fractured VBs and in 1.4% of the prophylactically cemented VBs; there were symptoms in 4.3%, and most of them were temporary hypotension and one pulmonary cement embolism that remained asymptomatic. The univariate regression model revealed a tendency for a reduced risk for new or refractures on radiographs (OR = 2.61, 95% CI 0.92–7.38, p = 0.12) and reoperations (OR = 2.9, 95% CI 0.94–8.949, p = 0.1) when prophylactic augmentation was performed. The final multivariate regression model revealed male patients to have an about three times higher refracture risk (radiographic) (OR = 2.78, p = 0.02) at 6 months after surgery. Patients with a lumbar index fracture had an about three to five times higher refracture/reoperation risk than patients with a thoracic (OR = 0.33/0.35, p = 0.009/0.01) or thoracolumbar (OR = 0.32/0.22, p = 0.099/0.01) index fracture. Conclusion If routinely used, VP is a safe and efficacious treatment option for osteoporotic vertebral fractures with regard to pain relief and improvement of the QoL. Even segmental realignment can be partially achieved with proper patient positioning. Certain patient or fracture characteristics increase the risk for early radiographic refractures or new fractures, or a reoperation; a consequent prophylactic augmentation showed protective tendencies, but the study was underpowered for a final conclusion.

Occurrence and severity of concomitant injuries in other areas than the face in children with mandibular and midfacial fractures

To clarify the occurrence, causes, severity, and predictors of concomitant injuries in pediatric patients with facial fractures.

Correlation of fat embolism severity and subcutaneous fatty tissue crushing and bone fractures

Pulmonary fat embolism (PFE) is frequently encountered in blunt trauma. The clinical manifestation ranges from no impairment in light cases to death due to right-sided heart failure or hypoxaemia in severe cases. Occasionally, pulmonary fat embolism can give rise to a fat embolism syndrome (FES), which is marked by multiorgan failure, respiratory disorders, petechiae and often death. It is well known that fractures of long bones can lead to PFE. Several authors have argued that PFE can arise due to mere soft tissue injury in the absence of fractures, a claim other authors disagree upon. In this study, we retrospectively examined 50 victims of blunt trauma with regard to grade and extent of fractures and crushing of subcutaneous fatty tissue and presence and severity of PFE. Our results indicate that PFE can arise due to mere crushing of subcutaneous fat and that the fracture grade correlated well with PFE severity (p = 0.011). The correlation between PFE and the fracture severity (body regions affected by fractures and fracture grade) showed a lesser significant correlation (p = 0.170). The survival time (p = 0.567), the amount of body regions affected by fat crushing (p = 0.336) and the fat crush grade (p = 0.485) did not correlate with the PFE grade, nor did the amount of body regions affected by fractures. These results may have clinical implications for the assessment of a possible FES development, as, if the risk of a PFE is known, preventive steps can be taken.

Comparative trends in hospitalizations for osteoporotic fractures and other frequent diseases between 2000 and 2008

In Switzerland, the number, incidence, and cost of acute hospitalizations for major osteoporotic fractures (MOF) and major cardiovascular events (MCE) increased in both women and men between 2000 and 2008, although the mean length of stay (LOS) was significantly reduced. Similar trend patterns were observed for hip fractures and strokes (decrease) and nonhip fractures and acute myocardial infarctions (increase).

Treatment with denosumab reduces the incidence of new vertebral and hip fractures in postmenopausal women at high risk

The FREEDOM (Fracture REduction Evaluation of Denosumab in Osteoporosis every 6 Months) trial showed denosumab significantly reduced the risk of fractures in postmenopausal women with osteoporosis.

Cost-effective intervention thresholds against osteoporotic fractures based on FRAX® in Switzerland

FRAX-based cost-effective intervention thresholds in the Swiss setting were determined. Assuming a willingness to pay at 2× Gross Domestic Product per capita, an intervention aimed at reducing fracture risk in women and men with a 10-year probability for a major osteoporotic fracture at or above 15% is cost-effective.