H. Kovacı

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.

Influence of plasma nitriding treatment on the adhesion of DLC films deposited on AISI 4140 steel by PVD magnetron sputtering

Abstract Duplex surface treatments composed of diamond like carbon (DLC) coating followed by plasma nitriding have drawn attention for a while. In this study, AISI 4140 steel substrates were plasma nitrided at different treatment temperatures and times. Then, DLC films were deposited on both untreated and plasma nitrided samples using PVD magnetron sputtering. The effect of different plasma nitriding temperatures and times on the structural, mechanical and adhesion properties of DLC coatings was investigated by XRD, SEM, microhardness tester and scratch tester, respectively. It was found that surface hardness, intrinsic stresses, layer thickness values and phase distribution in modified layers and DLC coating were the main factors on adhesion properties of duplex coating system. The surface hardness and residual stress values of AISI 4140 steel substrates significantly increased with both DLC coating and duplex surface treatment (plasma nitriding + DLC coating). Increasing plasma nitriding temperature and time also increased the diffusion depth and the thickness of modified layers. Hard surface layers led to a significant improvement on load bearing capacity of the substrate material. However, it was also determined that the process parameters, which provided lower intrinsic stresses, improved the adhesion properties of the duplex coating system.

Numerical investigation of mechanical effects caused by various fixation positions on a new radius intramedullary nail

Fracture of the radius diaphysis is an unusual injury in adults. Open reduction and plate osteosynthesis has been recommended by most of the authors. However, this trend has started to change with the recent introduction of newly designed interlocking intramedullary (IM) nails. New generation of IM nails are developed in order to utilise the advantages of IM nails against plates. Because of its anatomical structure, the radius bone has a complex geometry. Therefore, the callus structure, which forms during the healing period, should not be affected from external effects, such as excessive loads or motion. In this study, effects of radial styloid process (RSP), dorsal side and ulnar notch edge fixations of a new design radius IM nail on the healing period were numerically investigated. A three-dimensional solid model of radius was obtained from computed tomography images of a volunteer and callus structure model, was placed accordingly and different fixations of implants were performed. The models were analysed under axial loads transferring from the wrist to the radius bone using finite element method. As a result of the analysis, fixation of IM nail from RSP was found to be beneficial on healing period in terms of both callus motion and emerging stresses.

A NOVEL METHOD FOR IMPROVING PLASMA NITRIDING EFFICIENCY: PRE-MAGNETIZATION BY DC MAGNETIC FIELD

In this study, a novel pre-magnetization process, which enables easy diffusion of nitrogen, was used to enhance plasma nitriding efficiency. Firstly, magnetic fields with intensities of 1500G and 2500G were applied to the untreated samples before nitriding. After the pre-magnetization, the untreated and pre-magnetized samples were plasma nitrided for 4h in a gas mixture of 50% N2–50% H2 at 500∘C and 600∘C. The structural, mechanical and morphological properties of samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester and surface tension meter. It was observed that pre-magnetization increased the surface energy of the samples. Therefore, both compound and diffusion layer thicknesses increased with pre-magnetization process before nitriding treatment. As modified layer thickness increased, higher surface hardness values were obtained.

Effect of Plasma Nitriding Parameters on the Wear Resistance of Alloy Inconel 718

The effect of the temperature and duration of plasma nitriding on the microstructure and friction and wear parameters of Inconel 718 nickel alloy is investigated. The process of plasma nitriding is conducted in a nitrogen-hydrogen gaseous mixture at a temperature of 400, 500 and 600°C for 1 and 4 h. The modulus of elasticity of the nitrided layer, the micro- and nanohardness, the surface roughness, the friction factor and the wear resistance of the alloy are determined prior to and after the nitriding. The optimum nitriding regime providing the best tribological characteristics is determined.

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

Abstract 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.

Dry Sliding Wear Characteristics of Plasma-Nitrocarburized Co – Cr – Mo Alloy

Forged low-carbon alloy Co – 27% Cr – 6% Mo – 0.06% C is studied after 2-h plasma nitrocarburizing in a gaseous mixture of 10% CO2 + 20% N2 + 70% H2 at 400, 500 and 600°C. The surface layer and the core are studied by diffractometric analysis and scanning electron microscopy. The microhardness and the tribological characteristics of the alloy are determined. The effect of the temperature of nitrocarburizing on the wear resistance, surface roughness and friction coefficient of the alloy is considered.