Considering the Bottom Edge Cutting Effect of the Carbon Fiber Reinforced Polymer Milling Force Prediction Model and Optimization of Machining Parameters.

The milling force plays a pivotal role in CFRP milling. Modeling of the milling force is helpful to explore the changing law, optimize the processing parameters, and then reduce the appearance of defects. However, most of the existing models ignore the effect of the bottom edge.

Novel technique for repairing posterior medial meniscus root tears using porcine knees and biomechanical study.

Transtibial pullout suture (TPS) repair of posterior medial meniscus root (PMMR) tears was shown to achieve good clinical outcomes. The purpose of this study was to compare biomechanically, a novel technique designed to repair PMMR tears using tendon graft (TG) and conventional TPS repair. Twelve porcine tibiae (n = 6 each) TG group: flexor digitorum profundus tendon was passed through an incision in the root area, created 5 mm postero-medially along the edge of the attachment area.

Effect of different inner core diameters on structural strength of cannulated pedicle screws under various lumbar spine movements.

Background: Currently, cannulated pedicle screws have been widely used in minimal invasive or navigation techniques. However, the stress distribution and the strength of different core diameters of cannulated screw are not clear. This study aimed to investigate the mechanical strength of cannulated screws with different inner core diameter under various lumbar spine movements using finite element analysis.

Biomechanical evaluation of a novel pedicle screw-based interspinous spacer: A finite element analysis.

Interspinous spacers have been designed to provide a minimally invasive surgical technique for patients with lumbar spinal stenosis or foraminal stenosis. A novel pedicle screw-based interspinous spacer has been developed in this study, and the aim of this finite element experiment was to investigate the biomechanical differences between the pedicle screw-based interspinous spacer (M-rod system) and the typical interspinous spacer (Coflex-F™). A validated finite element model of an intact lumbar spine was used to analyze the insertions of the Coflex-F™, titanium alloy M-rod (M-Ti), and polyetheretherketone M-rod (M-PEEK), independently.

Measurement of Tip Apex Distance and Migration of Lag Screws and Novel Blade Screw Used for the Fixation of Intertrochanteric Fractures.

Fixation with a dynamic hip screw (DHS) is one of the most common methods for stabilizing intertrochanteric fractures, except for unstable and reverse oblique fracture types. However, failure is often observed in osteoporotic patients whereby the lag screw effectively 'cuts out' through the weak bone. Novel anti-migration blades have been developed to be used in combination with a lag screw ('Blade Screw') to improve the fixation strength in osteoporotic intertrochanteric fractures.

Translational research of one dynamic hip screw system-from the SCI to the FDA.

Background/objective: When researchers or developers wish to apply their findings to clinical usages, it must be approved by public authorities such as the US Food and Drug Administration (FDA). In addition to the development records and risk control documents, all of the materials and testing must be completed by laboratories or manufacturers with good quality controls in accordance with related regulations or standards. The Orthopaedic Device Research Center dynamic hip screw system (ODRC-DHS system), which was developed by the ODRC, National Yang-Ming University, Taipei, Taiwan, obtained FDA 510(k) clearance in 2011.

Effect of different radial hole designs on pullout and structural strength of cannulated pedicle screws.

Cannulated pedicle screws are designed for bone cement injection to enhance fixation strength in severely osteoporotic spines. However, the screws commonly fracture during insertion. This study aims to evaluate how different positions/designs of radial holes may affect the pullout and structural strength of cannulated pedicle screws using finite element analysis.

The effect of graft strength on knee laxity and graft in-situ forces after posterior cruciate ligament reconstruction.

Surgical reconstruction is generally recommended for posterior cruciate ligament (PCL) injuries; however, the use of grafts is still a controversial problem. In this study, a three-dimensional finite element model of the human tibiofemoral joint with articular cartilage layers, menisci, and four main ligaments was constructed to investigate the effects of graft strengths on knee kinematics and in-situ forces of PCL grafts. Nine different graft strengths with stiffness ranging from 0% (PCL rupture) to 200%, in increments of 25%, of an intact PCL's strength were used to simulate the PCL reconstruction.

Is the posterior cruciate ligament necessary for medial pivot knee prostheses with regard to postoperative kinematics?

Purpose: Excellent clinical and kinematical performance is commonly reported after medial pivot knee arthroplasty. However, there is conflicting evidence as to whether the posterior cruciate ligament should be retained. This study simulated how the posterior cruciate ligament, post-cam mechanism and medial tibial insert morphology may affect postoperative kinematics.

Biomechanical study of expandable pedicle screw fixation in severe osteoporotic bone comparing with conventional and cement-augmented pedicle screws.

Pedicle screws are widely utilized to treat the unstable thoracolumbar spine. The superior biomechanical strength of pedicle screws could increase fusion rates and provide accurate corrections of complex deformities. However, osteoporosis and revision cases of pedicle screw substantially reduce screw holding strength and cause loosening.

Biomechanical considerations in the design of high-flexion total knee replacements.

Typically, joint arthroplasty is performed to relieve pain and improve functionality in a diseased or damaged joint. Total knee arthroplasty (TKA) involves replacing the entire knee joint, both femoral and tibial surfaces, with anatomically shaped artificial components in the hope of regaining normal joint function and permitting a full range of knee flexion. In spite of the design of the prosthesis itself, the degree of flexion attainable following TKA depends on a variety of factors, such as the joint's preoperative condition/flexion, muscle strength, and surgical technique.

The effect of different humeral prosthesis fin designs on shoulder stability: a computational model.

Humeral prostheses commonly use a fin structure as an attachment point for the supraspinatus muscle in total shoulder arthroplasty (TSA), but these fins may cause injury to the muscle during implantation, inadvertently influencing stability. In order to prevent supraspinatus injury, the effect of different humeral prostheses on shoulder joint stability needs to be investigated. A commercially available prosthesis and two modified humeral prostheses that substituted the fin structure for 2 (2H) or 3 holes (3H) were evaluated using computational models.

Biomechanical comparisons between a new avascular necrosis of femaral head stem based on Chinese patients with avascular necrosis and two other designs.

Background: There is a relatively high failure rate of the femoral component in patients with avascular necrosis at the intermediate-term follow-up. Improving the geometrical fit of the femoral stem against the medullary canal may help to provide long-term survivorship of the hip replacement for patients with avascular necrosis.

Methods: We designed a specific stem, based on morphometric studies of proximal femoral canals in Chinese avascular necrosis patients and evaluated the stem by finite element analyses, comparing the novel stem with two commercially available and commonly used stems.

Biomechanical analysis of different types of pedicle screw augmentation: a cadaveric and synthetic bone sample study of instrumented vertebral specimens.

This study aims to determine the pull-out strength, stiffness and failure pull-out energy of cement-augmented, cannulated-fenestrated pedicle screws in an osteoporotic cadaveric thoracolumbar model, and to determine, using synthetic bone samples, the extraction torques of screws pre-filled with cement and those with cement injected through perforations. Radiographs and bone mineral density measurements from 32 fresh thoracolumbar vertebrae were used to define specimen quality. Axial pull-out strength of screws was determined through mechanical testing.

Morphometrical measurement of resected surface of medial and lateral proximal tibia for Chinese population.

Purpose: The objective of this study was to analyze the morphology of the medial tibial plateau and lateral tibial plateau in Chinese knees and compared these measurements and features with those of commercial unicondylar tibial baseplates.

Methods: Three-dimensional knee models were reconstructed from computed tomography slices of 81 subjects. Among the series, 27 knees were from male subjects and 54 knees from female subjects.

Concave polyethylene component improves biomechanical performance in lumbar total disc replacement--modified compressive-shearing test by finite element analysis.

Failure of ultra-high molecular weight polyethylene components after total disc replacements in the lumbar spine has been reported in several retrieval studies, but immediate biomechanical evidence for those mechanical failures remained unclear. Current study aimed to investigate the failure mechanisms of commercial lumbar disc prostheses and to enhance the biomechanical performances of polyethylene components by modifying the articulating surface into a convex geometry. Modified compressive-shearing tests were utilized in finite element analyses for comparing the contact, tensile, and shearing stresses on two commercial disc prostheses and on a concave polyethylene design.

Biomechanical evaluation of proximal tibial behavior following unicondylar knee arthroplasty: modified resected surface with corresponding surgical technique.

Persistent pain and periprosthetic fracture of the proximal tibia are troublesome complications in modern unicondylar knee arthroplasty (UKA). Surgical errors and acute corners on the resected surface can place excessive strains on the bone, leading to bone degeneration. This study attempted to lower strains by altering the orthogonal geometry and avoiding extended vertical saw cuts.

Influence of post-cam design of posterior stabilized knee prosthesis on tibiofemoral motion during high knee flexion.

Backgrounds: The post-cam design of contemporary posterior stabilized knee prosthesis can be categorized into flat-on-flat or curve-on-curve contact surfaces. The curve-on-curve design has been demonstrated its advantage of reducing stress concentration when the knee sustained an anteroposterior force with tibial rotation. How the post-cam design affects knee kinematics is still unknown, particularly, to compare the difference between the two design features.

Anatomic-like polyethylene insert could improve knee kinematics after total knee arthroplasty--a computational assessment.

Backgrounds: Deficiencies in contemporary posterior crucitate retaining knee included inadequate femoral rollback and insufficient tibial rotation. Current study attempted to restore normal femoral rollback and tibial rotation to facilitate in knee flexion/extension and to achieve appropriate posture at deep knee bending after total knee arthroplasy by mimicking the morphology of convexly lateral tibial plateau of intact knee.

Methods: Computational simulation was utilized to analyze motion of three-dimensional knee models, including intact, traditionally symmetrical posterior crucitate retaining and newly anatomic-like posterior crucitate retaining knees.

Incidence of hip replacement among national health insurance enrollees in Taiwan.

Background: There is no national joint replacement registry in the country of Asia and reports of national outcomes of joint replacement in Asia as yet. Therefore, this study was then to report a national data of the number of hip replacements, incidence rate, demographic characteristics of hip replacement patients, and short-time survival rate after hip replacement of Han Chinese in Taiwan.

Methods: We analyzed 105,688 cases of hip replacements (including primary partial hip replacement, primary total hip replacement and revision of hip replacement) from National Health Insurance research database between 1996 and 2004.