Designing and in vitro testing of a novel patient-specific total knee prosthesis using the probabilistic approach.

In order to prevent failure as well as ensure comfort, patient-specific modelling for prostheses has been gaining interest. However, deterministic analyses have been widely used in the design process without considering any variation/uncertainties related to the design parameters of such prostheses. Therefore, this study aims to compare the performance of patient-specific anatomic Total Knee Arthroplasty (TKA) with off-the-shelf TKA. In the patient-specific model, the femoral condyle curves were considered in the femoral component's inner and outer surface design. The tibial component was designed to completely cover the tibia cutting surface. In vitro experiments were conducted to compare these two models in terms of loosening of the components. A probabilistic approach based on the finite element method was also used to compute the probability of failure of both models. According to the deterministic analysis results, 103.10 and 21.67 MPa von Mises stress values were obtained for the femoral component and cement in the anatomical model, while these values were 175.86 and 25.76 MPa, respectively, for the conventional model. In order to predict loosening damage due to local osteolysis or stress shield, it was determined that the deformation values in the examined cement structures were 15% lower in the anatomical model. According to probabilistic analysis results, it was observed that the probability of encountering an extreme value for the anatomical model is far less than that of the conventional model. This indicates that the anatomical model is safer than the conventional model, considering the failure scenarios in this study.

Biomechanical analysis of spinal implants with different rod diameters under static and fatigue loads: an experimental study.

Spinal implants are commonly used in the treatment of spinal disorders or injuries. However, the biomechanical analyses of them are rarely investigated in terms of both biomechanical and clinical perspectives. Therefore, the main purpose of this study is to investigate the effects of rod diameter on the biomechanical behavior of spinal implants and to make a comparison among them. For this purpose, three spinal implants composed of pedicle screws, setscrews and rods, which were manufactured from Ti6Al4V, with diameters of 5.5 mm, 6 mm and 6.35 mm were used and a bilateral vertebrectomy model was applied to spinal systems. Then, the obtained spinal systems were tested under static tension-compression and fatigue (dynamic compression) conditions. Also, failure analyses were performed to investigate the fatigue behavior of spinal implants. After static tension-compression and fatigue tests, it was found that the yield loads, stiffness values, load carrying capacities and fatigue performances of spinal implants enhanced with increasing spinal rod diameter. In comparison to spinal implants with 5.5 mm rods, the fatigue limits of implants showed 13% and 33% improvements in spinal implants having 6 mm and 6.35 mm rods, respectively. The highest static and fatigue test results were obtained from spinal implants having 6.35 mm rods among the tested implants. Also, it was observed that the increasing yield load and stiffness values caused an increase in the fatigue limits of spinal implants.

Treatment with α-lipoic acid enhances the bone healing after femoral fracture model of rats.

This study investigated the fracture-healing effects of α-lipoic acid (α-LA), which was applied orally once daily in preventive treatment mode during 1 month after fracture induction. Rats were randomly divided into sham-operated group (group 1), femoral fracture control (group 2), femoral fracture + 25 mg/kg α-LA (group 3), and femoral fracture + 50 mg/kg α-LA (group 4). Rats in the experimental groups were orally administered 25 or 50 mg/kg α-LA once daily for 30 days starting from postoperative day 1. Thirty days postoperatively, the rats underwent X-ray imaging and were then euthanized for blood and tissue collection. Histopathological, biochemical, molecular, computed tomography (CT), and mechanical strength tests were performed on samples. The serum levels of osteocalcin (OC), osteopontin (OP), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6) did not differ significantly between groups 2 and 3. Serum OC, OP, TNF-α, and IL-6 levels in group 4 were significantly lower than those in group 3. From X-ray images, staging for fracture healing was scored as <2 in group 2, >2 in group 3, and >3 in group 4. In group 2, the average score of less than 2 suggests insufficient fracture healing; those of both the α-LA groups were >2, indicating progression of healing. Transforming growth factor beta (TGF-ß) messenger RNA (mRNA) levels were significantly higher in the sham group than in the femoral fracture control. Both doses of α-LA increased TGF-ß mRNA expression compared to the fracture group. CT results and biomechanical testing at 4 week after fracture demonstrated that α-LA has fastened bone healing, which was confirmed by stereological analyses in which 50 mg/kg α-LA increased the number of osteoclasts. Our findings indicate that α-LA supplementation promotes healing of femoral fractures in rats.

New interlocking intramedullary radius and ulna nails for treating forearm diaphyseal fractures in adults: a retrospective study.

INTRODUCTION: The treatment goal for diaphyseal forearm fractures in adults is to restore axial and rotational stability. The treatment of these fractures with intrmaedullary locked nailing remains sparse. We therefore evaluated IM nails for treating forearm diaphyseal fractures in adults. METHODS: We retrospectively reviewed adult patients with isolated unilateral or bilateral fractures of the radius, ulna, or both, who were treated with closed or mini open reduction with a new IM nail between May 2008 and January 2012 and who were followed for a least 1 year. Patients with a Galeazzi fracture, a pathological fracture or patients with nonunion after previous surgeries were excluded. All patients were allowed full range of motion without any external support. Primary outcomes were Grace and Eversmann rating, Disabilities of the Arm, Shoulder and Hand (DASH) scores. RESULTS: The 43 enrolled patients (mean age, 37 years; 32 men) had 59 forearm fractures: 14 isolated radius fractures, 17 isolated ulna fractures (2 bilateral), and 28 fractures of both the radius and ulna. Mean time to fracture union was 13 weeks (range 10-14 weeks) for ulnar fractures and 12 weeks (range 10-13 weeks) for radial fractures. No patient had nonunion, deep infections, or radioulnar synostosis. Followup ranged from 12 to 44 months. Grace and Eversmann ratings were excellent in 38 patients and good in 5. Mean DASH score was 6.5 points (range 0-13.3). CONCLUSIONS: Intramedullary nailing of adult forearm diaphyseal fractures appears to be a good alternative to plate osteosynthesis. The advantages are short operative time, minimal invasive techniques, and sufficient stability in all planes that allows early motion without additional fracture support.