From microstructural design to surface engineering: A tailored approach for improving fatigue life of additively manufactured meta-biomaterials.

Recently, lattice titanium manufactured by additive manufacturing (AM) techniques has been utilized in various applications, including biomedical. The effects of topological design and processing parameters on the fatigue behaviour of such meta-biomaterials have been studied before. Most studies show that the fatigue life of additively manufactured lattice structures is limited. Post-processing techniques could play a major role in improving the fatigue of these promising biomaterials. This study aims to provide an in-depth investigation into the effects of heat treatments, hot isostatic pressing (HIP), sand blasting, and chemical etching on the microstructure, surface morphology, strength and fatigue resistance of selective laser melted titanium meta-biomaterials. It was found that the combination of microstructural design and surface engineering, induced by HIP and sand blasting respectively, allows to increase the endurance limit of these lattice meta-biomaterials by a factor of two. HIP treatment substantially decreased the internal porosity and transformed the microstructure to a more ductile mixture of α +â€¯ß phases. Sand blasting allowed to eliminate surface imperfections and induced favourable compressive stress in the surface layer of the struts. STATEMENT OF SIGNIFICANCE: Additively manufactured metallic meta-biomaterials are progressively being used as bone replacement orthopedic implants. While there is a great amount of research related to topological designs and their effect on mechanical (e.g. stiffness), physical (e.g. mass transport), and biological (e.g. osseointegration) properties, fatigue lifetime of such structures remains limited. This study provides fundamental investigation into the combined effect of microstructural design and surface engineering of titanium meta-biomaterial, enabled through various post treatment methods ranging from heat treatments to physical and chemical surface modifications. The findings show that fatigue life is significantly improved by applying developed herein novel method, which effortlessly can be used on other bone-mimicking metallic meta-biomaterials.

Effect of time zone and game time changes on team performance: National Football League.

To determine the effect of time zone and game time changes on NFL team performance, win-loss records from 1978-1987 were analyzed. Twenty-seven NFL teams were grouped by time zone and possible anti-jet lag adjustments. Among all intra-time zone rivals, home teams won 56.6%, away teams won 43.8%, for a home vs away winning percentage change of -12.8% (P < 0.001). West teams (N = 5) displayed fluctuations in home vs away team performance in association with trans-meridian travel. The change in winning percentage was found to be 0.0% vs West teams, -14.1% vs Central teams (N = 8) (P < 0.05), -16.3% vs East (N = 14) (P < 0.05) for West teams (N = 4) flying about 42 h pregame and +2.3% vs East for the one West team advancing practices 3-4 h to match East coast game time in addition to 48 h pregame flights. For night games within the same time zone, home vs away team winning percentage changed -23.8% (P < 0.01). West teams displayed uniformly high home winning percentages (75.0% and 68.4%) when playing Central and East teams, respectively, with little or no fall in away winning percentages (67.7% and 68.8%). For day games, a 3-h phase advance may decrease West coast team performance. In one small subset, anti-jet lag adjustments appeared to eliminate the expected decrement in performance. For night games, West coast teams, whether home or away, appear to be at a distinct advantage over East and Central teams.

Proximal humeral fractures: a correlation of residual deformity with long-term function.

Twenty-six patients with 27 fractures of the proximal humerus were evaluated by radiographic and clinical examination (Neer rating scale) 13 months to 12 years after injury. Proximal humeral fractures that had healed with less than 55° of angulation and less than 1.5 cm of displacement of the major fracture segments had good or excellent functional results. These fractures were successfully treated with a sling or cuff and collar immobilization. Two- and three-part fractures with greater than 55° of angulation or greater than 1.5 cm of displacement had fair or poor functional results. These fractures should be reduced by closed or open methods if good or excellent results are required. Minimal (0 to 2 mm) displacement of greater tuberosity fractures was often associated with rotator cuff tears. Neither good nor excellent results were obtained in four-part, Group IV fractures treated nonsurgically.