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The aim of this research is to simulate and analyze a combined power cycle (Steam turbine and gas turbine cycles) by studying the effect of changing the natural gas flow rate on the developed power. Therefore, reducing the amount of used natural gas in the combustion chamber of the gas turbine cycle from 9.2 to 4 kg/s showed a significant drop in the power produced by the gas turbine, i.e., from 123.7 to 57.7 MW. Additionally, this change in the combusted natural gas amount affected the heat recovered in both heat recovery steam generators (HRSGs), i.e., from 219.79 to 100.35 MW, respectively. Consequently, the amount of generated steam in the high pressure HRSGs and the power developed in the steam turbine changed from 60.88 to 27.79 kg/s and from 56.39 to 27.13 MW, respectively. A heat exchanger (HFHX) utilizing a heating fluid was used as an external source of energy to compensate the reduction in the generated heat and to increase the amount of generated steam up to 157.32 kg/s, which keeps the power plant capacity at 180 MW. Existing combined local plant data were used in this study and were simulated in Aspen Plus software V11. A sensitivity analysis was made to optimize the cycle operating conditions that use less natural gas and produce the same amount of power.

Purpose: To report the functional and radiologic outcomes of meniscal repair healing in a cohort of patients with a high demand for loaded extreme flexion angles after undergoing meniscal repair. Methods: We performed a retrospective clinical and radiologic evaluation of patients who perform extreme knee flexion activities on a daily basis at a minimum follow-up of 2 years after meniscal repair. International Knee Documentation Committee, Lysholm, and Tegner scores were obtained, and clinical examinations and radiologic (magnetic resonance imaging and radiography) evaluations were performed. Results: Of 47 eligible patients, 39 patients (40 knees) were available for review with an average follow-up time of 5 years (range, 2-9 years). The average age was 26.7 years (range, 19-39 years); 38 patients were men. The average time from injury to surgery was 20.9 months (range, 3 days to 120 months). Associated anterior cruciate ligament injury was present in 31 knees, but only 20 underwent simultaneous anterior cruciate ligament surgery. The mean International Knee Documentation Committee score was 88.9 (range, 53-99). The mean Lysholm score was 90.9 (range, 48-100). The mean Tegner activity level dropped from 6.18 before injury to 5.51 at the time of evaluation. According to the Barrett criteria for clinical outcomes, complete healing was observed in 29 of 40 knees (72.5%). There was a statistically significant correlation between the functional outcomes and the clinical outcomes (P = .008). On magnetic resonance imaging, 22 of 38 knees (57.9%) showed completely healed menisci. Conclusions: The results of this study suggest that loaded deep knee flexion may be safe after a period of restricted rehabilitation, and clinical and radiologic tissue healing is independent of the overall functional outcome. Level of Evidence: Level IV, case series with subgroup analysis.

Introduction: The novel coronavirus has spread rapidly around the world with particularly high mortality in the elderly. Care and nursing homes have become the sites of greatest concentration of cases. We intended to review 30-day mortality of COVID-19 patients with hip fractures. This is relevant given the disease impact in this age group. Methods: Medline and Embase databases were searched for relevant studies linked to mortality and morbidity in COVID-19 patients who have undergone non-elective hip surgeries using the keywords “COVID-19”OR “SARS-cov-2”OR “Coronavirus Infections”; AND “Surgery”OR “Hip”OR “Fracture”OR “Orthopedics.” We included all patients with hip fractures, but excluded pathological fractures and other non-traumatic hip pathologies. Four-hundred and eighty-one articles were identified for screening, in addition to an unpublished case-series of 67 patients that have 3 cases turned positive for COVID 19, yielding a total of 50patients for the final review. Results: The study included 4 articles published until May 9th 2020 and a case-series: 26(52%) patients were females; the median age was 86years; hypertension(53.6%), diabetes mellitus type II(28.6%), and coronary artery heart disease(25%) were the most common comorbidities; 34(68%) patients had intertrochanteric hip fracture and 16(32%) patients had femoral neck fractures; 22(59.5%) patients underwent cephalomedullary nail fixation, 12(32.4%) patients had hemiarthroplasty, and for 3(8.1%) patients, the type of surgery was not documented; 20(40%) patients died(12patients died before the surgery and 8died after surgery at a median time of 3days), 29(76.3%) patients had an unremarkable course throughout hospitalization and were discharged including 1(2.6%) patient managed non-operatively, and 1(2.6%) patient was admitted to the ICU after the surgery but eventually discharged. Conclusion: COVID-19 infected elderly patients have a higher 30-days mortality rate compared to non-COVID-19 infected cases. Further studies are warranted to look at the morbidity and mortality rates in COVID-19 positive patients with hip fractures and to investigate how these outcomes can be improved. Level of evidence: Level IV

Introduction: The purpose of this study is to retrospectively evaluate the immediate effect of retrograde intramedullary femoral nail (RIMFN) fixation technique on patient's hemodynamic status as documented by vital signs (blood pressure and pulse) intraoperatively in all patients with femoral shaft fractures with multiple injuries and hemodynamic instability who were treated with RIMFN at our institution on emergency basis as part of damage control orthopaedics. Patients and methods: A retrospective review of intra operative vital signs obtained from patient records was completed at a Level 1 trauma center in a university hospital.In all, 11 multiply injured patients with (14) femur fractures with hemodynamic instability were identified. Of those, 3 had bilateral femur fractures. Closed reduction and retrograde femoral nailing without proximal locking was performed to achieve immediate skeletal and haemodynamic stability. Pulse rate and BP measurements were noted for all patients starting from the time patient would enter the operating room till the patient was shifted back to the recovery ward. Results: The average cohort age was 28 years (20–36 years). The average Injury Severity Score was 28 (16–50). Statistically significant improvement in pulse rate and blood pressure was noted following femoral fracture fixation with intramedullary nail. No cases of infection or symptomatic fat or pulmonary embolism were encountered. One patient required exchange nailing for non-union and one femur underwent later lengthening. Conclusions: Retrograde Intramedullary femoral nail can be an effective alternative to external fixator as damage control device and is associated with immediate improvement in vital signs (pulse and blood pressure) intra operatively.

Periprosthetic joint infection (PJI) due to Brucella is uncommon despite relatively high endemicity of human brucellosis and its osteoarticular predilection. We report a case of a 57-year-old woman with bacteraemic brucellosis complicated by Brucella periprosthetic infection of both knee joints occurring a decade after bilateral knee arthroplasty and associated with a negative synovial fluid alpha-defensin test. The patient was successfully treated with anti-Brucella therapy alone and without surgical revision, resulting in clinical and microbiological cure. We propose that Brucella should be considered as a possible cause of prosthetic joint infection in the appropriate clinical and epidemiological settings. A negative synovial fluid alpha-defensin (Synovasure AD test) should not be used as a rule-out test for Brucella PJI. Brucella PJI without radiological loosening may be treated conservatively and solely with antimicrobial therapy.