An Experimental Study on the Impact of Layer Height and Annealing Parameters on the Tensile Strength and Dimensional Accuracy of FDM 3D Printed Parts.

This study investigates the impact of annealing time, temperature, and layer height on the tensile strength and dimensional change of three 3D printing materials (PLA, PETG, and carbon fiber-reinforced PETG). Samples with varying layer heights (0.1 mm, 0.2 mm, and 0.3 mm) were annealed at temperatures ranging from 60-100 °C for 30, 60, and 90 min. Tensile tests were conducted, and regression models were developed to analyze the effects of these parameters on tensile strength. The models exhibited high accuracy, with a maximum deviation of only 5% from measured validation values. The models showed that layer height has a significantly bigger influence on tensile strength than annealing time and temperature. Optimal combinations of parameters were identified for each material, with PLA performing best at 0.1 mm/60 min/90 °C and PETG and PETGCF achieving optimal tensile strength at 0.1 mm/90 min/60 °C. PETGCF demonstrated smallest dimensional change after annealing and had the best modulus of elasticity of all the materials. The study employed experimental testing and regression models to assess the results across multiple materials under consistent conditions, contributing valuable insights to the ongoing discussion on the influence of annealing in 3D-printed parts.

Extra-Articular Distal Humerus Plate 3D Model Creation by Using the Method of Anatomical Features.

Proper fixation techniques are crucial in orthopedic surgery for the treatment of various medical conditions. Fractures of the distal humerus can occur due to either high-energy trauma with skin rupture or low-energy trauma in osteoporotic bone. The recommended surgical approach for treating these extra-articular distal humerus fractures involves performing an open reduction and internal fixation procedure using plate implants. This surgical intervention plays a crucial role in enhancing patient recovery and minimizing soft tissue complications. Dynamic Compression Plates (DCPs) and Locking Compression Plates (LCPs) are commonly used for bone fixation, with LCP extra-articular distal humerus plates being the preferred choice for extra-articular fractures. These fixation systems have anatomically shaped designs that provide angular stability to the bone. However, depending on the shape and position of the bone fracture, additional plate bending may be required during surgery. This can pose challenges such as increased surgery time and the risk of incorrect plate shaping. To enhance the accuracy of plate placement, the study introduces the Method of Anatomical Features (MAF) in conjunction with the Characteristic Product Features methodology (CPF). The utilization of the MAF enables the development of a parametric model for the contact surface between the plate and the humerus. This model is created using specialized Referential Geometrical Entities (RGEs), Constitutive Geometrical Entities (CGEs), and Regions of Interest (ROI) that are specific to the human humerus bone. By utilizing this anatomically tailored contact surface model, the standard plate model can be customized (bent) to precisely conform to the distinct shape of the patient's humerus bone during the pre-operative planning phase. Alternatively, the newly designed model can be fabricated using a specific manufacturing technology. This approach aims to improve geometrical accuracy of plate fixation, thus optimizing surgical outcomes and patient recovery.

[Dermatomyositis associated with metastatic rectal adenocarcinoma: case report].

INTRODUCTION: Dermatomyositis is an idiopathic inflammatory myopathy with characteristic cutaneous changes. The disease belongs to paraneoplastic dermatosis. Association of dermatomyositis with malignant conditions has been described in various studies. We present a patient with paraneoplastic dermatomyositis associated with metastatic rectal adenocarcinoma. CASE REPORT: A 66-year-old man was hospitalized in our Institute due to skin changes and myopathy in October 2006. According to the medical documents and history, he underwent surgery because of rectal adenocarcinoma in April 2006. Skin changes appeared 5 months before, while aggravation occurred 6 months after the surgery. The diagnosis of dermatomyositis was based on: characteristic clinical picture; the elevated serum level of following enzymes: creatinine kinase, lactate dehydrogenase; the presence of anti-Mi 2 antibodies in serum; electromyographic finding; and by histology of the muscle biopsy. Paraneoplastic nature of dermatomyositis was confirmed by computer tomography of the abdomen which revealed multiple deposits in the liver, by explorative laparotomy showing peritoneal dissemination and histopathological analysis that verified metastatic adenocarcinoma of the rectum. The oncological consulting team suggested chemotherapy which was not carried out because of the rapid lethal outcome. CONCLUSION: We report a case of paraneoplastic dermatomyositis associated with metastatic rectal adenocarcinoma and lethal outcome, and suggest a comprehensive evaluation of patients with dermatomyositis older than 50 years in order to exclude or verify the occult malignancy.

Interphalangeal joint cartilage: high-spatial-resolution in vivo MR T2 mapping--a feasibility study.

The purpose of this study was to evaluate feasibility of magnetic resonance (MR) T2 mapping of the proximal interphalangeal joint of the index finger. Cartilage T2 maps with an in-plane resolution of 39 microm were obtained from five asymptomatic subjects-four men and one woman, aged 24-45 years-by using a 3.0-T MR imager. Image acquisition time was 9.6 minutes. All cartilage T2 maps demonstrated spatial variation similar to that reported previously for knee cartilage, with T2 values increasing toward the articular surface. These results demonstrate the feasibility of acquiring cartilage T2 maps of small joints in the hand. Application of T2 mapping techniques to non-weight-bearing joints may provide a means for differentiation of local biomechanical and systemic factors that can affect cartilage T2 values.