Design of an Implant for First Metatarsophalangeal Joint Hemiarthroplasty

Osteoarthritis (OA) is the most common form of arthritis and it affects 27 million US adults. OA disease involves all of the tissues of the diarthrodial joint and ultimately, may lead to softening, ulceration, loss of articular cartilage, sclerosis and polished appearance of the subchondral bone, osteophytes, and subchondral cysts. The first metatarsophalangeal joint (MTPJ1) is affected in up to 42 cases of OA. Besides osteoarthritis, other conditions such as rheumatoid arthritis and gout also affect the MTPJ1. Involvement of MTPJ1 with these conditions invariably leads to deformed toe such as hallux valgus and hallux rigidus. Over 150 surgical techniques exist for treatment of hallux deformity, which includes cheilectomy, arthrodesis, osteotomy, resection arthroplasty, and replacement of part or the entire articular surface with an implant. A hemi-implant, which partially replaces the 1st metatarsal head with minimal bone resection and without altering the sesamoid articulation has shown promising results and gives superior postoperative range of motion and pain reductions. But the geometry of such implants has not been explained in any literature and there are no details of the data used for designing such implants. An anatomically based approach to design the geometry of an MTPJ1 implant is needed in order to best fit the articulating surface of the adjacent phalanx. In the current study, a method was developed for designing a hemiarthroplasty implant for MTPJ1 based upon the morphology of metatarsal. Ninety-seven metatarsal osteological specimens were scanned using a laser scanner to obtain 3D surface data. After aligning the surface data, the articular surface of each metatarsal head (MTH1) superior to the inter-condylar ridge were characterized by a section of an ellipsoid using non-linear unconstrained optimization (NLUO) and the section of the ellipsoid forms the surface of the implant. The implants based upon osteological specimens had a very good fit to metatarsal articulating surface with root mean

Design of an Implant for First Metatarsophalangeal Joint Hemiarthroplasty

Osteoarthritis (OA) is the most common form of arthritis and it affects 27 million US adults. OA disease involves all of the tissues of the diarthrodial joint and ultimately, may lead to softening, ulceration, loss of articular cartilage, sclerosis and polished appearance of the subchondral bone, osteophytes, and subchondral cysts. The first metatarsophalangeal joint (MTPJ1) is affected in up to 42 cases of OA. Besides osteoarthritis, other conditions such as rheumatoid arthritis and gout also affect the MTPJ1. Involvement of MTPJ1 with these conditions invariably leads to deformed toe such as hallux valgus and hallux rigidus. Over 150 surgical techniques exist for treatment of hallux deformity, which includes cheilectomy, arthrodesis, osteotomy, resection arthroplasty, and replacement of part or the entire articular surface with an implant. A hemi-implant, which partially replaces the 1st metatarsal head with minimal bone resection and without altering the sesamoid articulation has shown promising results and gives superior postoperative range of motion and pain reductions. But the geometry of such implants has not been explained in any literature and there are no details of the data used for designing such implants. An anatomically based approach to design the geometry of an MTPJ1 implant is needed in order to best fit the articulating surface of the adjacent phalanx. In the current study, a method was developed for designing a hemiarthroplasty implant for MTPJ1 based upon the morphology of metatarsal. Ninety-seven metatarsal osteological specimens were scanned using a laser scanner to obtain 3D surface data. After aligning the surface data, the articular surface of each metatarsal head (MTH1) superior to the inter-condylar ridge were characterized by a section of an ellipsoid using non-linear unconstrained optimization (NLUO) and the section of the ellipsoid forms the surface of the implant. The implants based upon osteological specimens had a very good fit to metatarsal articulating surface with root mean

Examination of anticipated chemical shift and shape distortion effect on materials commonly used in prosthetic socket fabrication when measured using MRI: a validation study

The quality of lower-limb prosthetic socket fit is influenced by shape and volume consistency during the residual limb shape-capturing process (i.e., casting). Casting can be quantified with magnetic resonance imaging (MRI) technology. However, chemical shift artifact and image distortion may influence the accuracy of MRI when common socket/casting materials are used. We used a purpose-designed rig to examine seven different materials commonly used in socket fabrication during exposure to MRI. The rig incorporated glass marker tubes filled with water doped with 1 g/L copper sulfate (CS) and 9 plastic sample vials (film containers) to hold the specific material specimens. The specimens were scanned 9 times in different configurations. The absolute mean difference of the glass marker tube length was 1.39 mm (2.98%) (minimum = 0.13 mm [0.30%], maximum = 5.47 mm [14.03%], standard deviation = 0.89 mm). The absolute shift for all materials was <1.7 mm. This was less than the measurement tolerance of +/–2.18 mm based on voxel (three-dimensional pixel) dimensions. The results show that MRI is an accurate and repeatable method for dimensional measurement when using matter containing water. Additionally, silicone and plaster of paris plus 1 g/L CS do not show a significant shape distortion nor do they interfere with the MRI image of the residual limb

A novel approach of intra-operative shape acquisition of the tibio-femoral joints using 3D laser scanning for computer assisted orthopaedic surgery

Background: Image registration (IR) is an important process of developing a spatial relationship between pre - operative data and physical patient in the operation theatre. Current IR techniques for Computer Assisted Orthopaedic Surgery (CAOS) are time consuming and costly. There is a need to automate and accelerate this process. Methods: Bespoke quick, cost effective, contactless and automated 3D laser scanning techniques based on the DAVID Laserscanner method were designed. 10 cadaveric knee joints were intra - operatively laser scanned and were registered with the pre - operative MRI scans. The results are supported with a concurrent validity study. Results: The average absolute errors between scan models were systematically less than 1mm. Errors on femoral surfaces were higher than tibial surfaces. Additionally, scans acquired through the large exposure produced higher errors than the smaller exposure. Conclusion: This study has provided proof of concept for a novel automated shape acquisition and registration technique for CAOS

Modeling and Simulation in Engineering

This book provides an open platform to establish and share knowledge developed by scholars, scientists, and engineers from all over the world, about various applications of the modeling and simulation in the design process of products, in various engineering fields. The book consists of 12 chapters arranged in two sections (3D Modeling and Virtual Prototyping), reflecting the multidimensionality of applications related to modeling and simulation. Some of the most recent modeling and simulation techniques, as well as some of the most accurate and sophisticated software in treating complex systems, are applied. All the original contributions in this book are jointed by the basic principle of a successful modeling and simulation process: as complex as necessary, and as simple as possible. The idea is to manipulate the simplifying assumptions in a way that reduces the complexity of the model (in order to make a real-time simulation), but without altering the precision of the results

Reliability and comparison of 3-dimensional surface imaging of the face using a hand-held and whole body surface scanner

Objective: 3-Dimensional surface (3DSI) imaging has been shown to be a useful tool for plastic surgeons in the preoperative, intraoperative and postoperative setting. And to the knowledge of the authors no data about the reproducibility and accuracy of 3-Dimensional surface imaging of the face using a whole-body scanner is available. Thus, the objective of this investigation was to assess the reproducibility of facial scans acquired using a whole-body imaging device and to compare the precision of distance measurements in the face using a hand-held surface imaging device and a whole-body surface imaging device. Furthermore, the reproducibility of the whole body scanner was investigated. Material and Methods: This investigation enrolled a total of 22 healthy volunteers with a mean age of 29.36 years. Two consecutive 3-D images of the volunteers were obtained utilizing a whole-body imaging device(WB360) and a hand-hold imaging device(Vectra H2). For the whole-body imaging predefined distances in the face were performed in each scan and compared. Furthermore, surface deviation between two consecutively captured scans was assessed. Results: For the reliability of whole-body scan, the distance with the smallest statistical significance was found to be at the nose with p = 0.998, while the biggest statistical significance was found in the midface with p = 0.658. The area with the biggest surface deviation between the superimposed scans was the neck with a RMS of 1.62 ± 1.71 mm and the area with the smallest surface deviation was the forehead with a RMS of 0.17 ± 0.05 mm. For the comparison of the both scanners our results revealed that the measured difference between the length and the standard reference did not differ statistically significant between the two investigated devices in all investigated areas of the face (p > 0.266), however the measured difference of the width and the width of the standard reference differed statistically significant in all areas of the face across the investigated devices (p < 0.032). Conclusion: The whole – body-imaging device investigated in this study can be utilized to capture the face and provides enough accuracy to compare scans. Even though not directly investigated, it can be hypothesized that the error caused by repositioning the patient between a baseline and a follow – up scan will not be too big to consider measurements performed with the whole – body-imaging device as impractical. Both, measurements obtained from scans acquired using the hand held imaging device and the whole – body-imaging device differed significantly from the standard reference. Users should be aware of deviations when obtaining 3DSI using the presented imaging devices but should not refrain from using them, as the absolute differences might be too small to play a role in both, clinical and research, setting

ToScA North America (6 – 8 June 2017, The University of Texas, Austin, TX) Program

ToScA North America will address key areas of science, including Multi-modal Imaging, Geosciences, Forensics, Increasing Contrast, Educational Outreach, Data, Materials Science and Medical and Biological Science.University of Texas High-Resolution X-ray CT Facility (UTCT); Jackson School of Geosciences, The University of Texas at Austin; Natural History Museum (London); Royal Microscopical Society (Oxford, UK)Geological Science