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Vitamin D Levels in Patients with Low-energy Hip Fractures
Jaehwi Han,조영호,Seungmin Jee,Seongwoo Jo 대한고관절학회 2020 Hip and Pelvis Vol.32 No.4
Purpose: To evaluate serum 25(OH) vitamin D levels in patients with low-energy hip fractures. Materials and Methods: Among 983 patients who underwent hip fracture surgery between August 2013 and March 2019, 732 patients were evaluated. The remaining patients were excluded due to the presence of one or more of the following: metastatic bone tumor, metabolic bone disease other than osteoporosis, fracture due to high-energy injury, atypical femoral fracture, and no blood test. We collected patient’s data about age, sex male female, date of injury, a place of residence, fracture type, preinjury ambulation ability according to their Koval score, and their serum level of 25(OH) vitamin D. The mean age was 79.3 years (60-104 years). The sample was comprised of 530 female and 202 male, of which 342 had femoral neck fractures and 390 had trochanteric fractures. Results: Of the total 732 patients, 346 patients (47.3%) had a 25(OH) vitamin D level of less than 10 ng/mL, 264 patients (36.1%) had scores of 10-19.9 ng/mL, 87 patients (11.9%) had scores of 20-29.9 ng/mL, and 35 patients (4.8%) had a level higher than 30 ng/mL. Vitamin D deficiency (less than 20 ng/mL) was present in 610 patients (83.3%), insufficiency (20-29.9 ng/mL) was found in 87 patients (11.9%), and 35 patients (4.8%) had normal vitamin D levels. The differences in vitamin D concentration based on season and fracture type were statistically significant. Conclusion: Vitamin D deficiency and inadequacy were high in patients with low-energy hip fractures, with only 4.9% of patients had normal vitamin D levels. These findings suggest that efforts should be made to maintain proper vitamin D concentration.
Effect of Channel-Estimation Error on BER Performance in Cooperative Transmission
Seungyoup Han,Seongwoo Ahn,Eunsung Oh,Daesik Hong IEEE 2009 IEEE Transactions on Vehicular Technology VT Vol.58 No.4
<P>In this paper, a framework for evaluating the bit-error-rate (BER) performance of amplify-and-forward (AF) relay-assisted cooperative transmission is provided in the presence of imperfect channel estimation. First, the AF relaying is classified into two cases - a variable gain and a fixed gain. For each case, the closed-form average BER is derived by using the moment-generating function (MGF) of the effective output SNR, which quantifies the SNR penalty due to the noisy channel estimate. Moreover, the asymptotic BER bound is also provided at a high SNR regime for the insight of our approach. In particular, the effect of the feedforward delay on informing the source-relay channel estimate as to the destination is presented in the variable-gain relay. Numerical investigation shows that the analytic result makes an exact match with the simulation, and the comparative superiority between the fixed- and variable-gain relay is discussed.</P>