ABSTRACT
BACKGROUND: Avascular necrosis (AVN) is a potentially serious multifactorial disease. In COVID-19 patients, AVN of many bones has been reported. Usually, the condition is linked to steroid therapy. In this case report, we describe our experience with bilateral AVN of femoral heads in an elderly patient months after being cured of COVID-19 infection without the use of steroids. CASE PRESENTATION: A 68-year-old male was referred to the outpatient clinic of the rheumatology and rehabilitation department for progressive bilateral hip pain starting on the left side 5 months ago. An extensive review of the patient's medical history identified documented COVID-19 infection that required hospitalization 9 months before presentation. Multiplanar MRI with fat suppression of both hips showed ill-defined areas of abnormal signal intensity affecting the left femoral head, neck and intertrochanteric regions with associated subchondral fissuring and mild joint effusion. A similar smaller area was also seen affecting the postero-superior aspect of the right femoral head. CONCLUSION: AVN in COVID-19 patients can be encountered even in the absence of steroid therapy.
ABSTRACT
Aluminum alloys are the most essential part of all shaped castings manufactured, mainly in the automotive, food industry, and structural applications. There is little consensus as to the precise relationship between grain size after grain refinement and corrosion resistance; conflicting conclusions have been published showing that reduced grain size can decrease or increase corrosion resistance. The effect of Al-5Ti-1B grain refiner (GR alloy) with different percentages on the mechanical properties and corrosion behavior of Aluminum-magnesium-silicon alloy (Al-Mg-Si) was studied. The average grain size is determined according to the E112ASTM standard. The compressive test specimens were made as per ASTM: E8/E8M-16 standard to get their compressive properties. The bulk hardness using Vickers hardness testing machine at a load of 50 g. Electrochemical corrosion tests were carried out in 3.5 % NaCl solution using Autolab Potentiostat/Galvanostat (PGSTAT 30).The grain size of the Al-Mg-Si alloy was reduced from 82 to 46 µm by the addition of GR alloy. The morphology of α-Al dendrites changes from coarse dendritic structure to fine equiaxed grains due to the addition of GR alloy and segregation of Ti, which controls the growth of primary α-Al. In addition, the mechanical properties of the Al-Mg-Si alloy were improved by GR alloy addition. GR alloy addition to Al-Mg-Si alloy produced fine-grained structure and better hardness and compressive strength. The addition of GR alloy did not reveal any marked improvements in the corrosion properties of Al-Mg-Si alloy.
