ABSTRACT
Objective Aiming at solving the problems of pain on the anteromedial tibia, tibial component loosening and osteoarthritis progression after unicompartmental knee arthroplasty (UKA), the influence of different geometric shapes of tibial component pegs on stress distributions in tibia was analyzed by finite element method. Methods The finite element models with UKA were established and validated. Geometric shapes of tibial component were designed. Under the same loading condition, the tibial components with double-peg, single-keel, double-keel and cross-star were studied for finite element analysis and compared with intact model, so as to evaluate the influence of tibial component with different shapes on stresses of cortical bone in anteromedial tibia, cancellous bone under tibial component and cartilage in contralateral tibia. Results Compared with the intact model, the peak stress of cortical bone in anteromedial tibia with double-peg, single-keel, double-keel and cross-star tibial components increased by 56.1%, 55.9%, 54.5% and 68-4%, respectively. The peak stress of cancellous bone under tibial component with single-keel and double-keels decreased by 8.1% and 15.6% respectively, while the peak stress of cancellous bone under tibial component with double-peg and cross-star increased by 67-9% and 121-5%, which were higher than the fatigue yield stress of cancellous bone. The peak stress of cartilage in contralateral tibia with double-peg, single-keel, double-keel and cross-star tibial components decreased by 42.1%, 26.6%, 24.2% and 28.5%, respectively. ConclusionsThe load distribution of the medial and lateral tibia changed after UKA operation, and a greater load was observed on the replacement side. Single-keel and double-keel tibial components were more effective in reducing stresses on cortical bone in anteromedial tibia and cancellous bone, while the stress distribution in tibia with single-keel tibial component was closer to that of the intact tibia. The research findings can provide theoretical references for designing single-keel tibial component of unicompartmental knee prosthesis which conforms to better mechanical properties of the knee joint.
ABSTRACT
Objective To study the epidemiology of mycoplasma pneumonia (MP) infection in children and its relationship to meteorological conditions in Guilin. Methods Total of 1 342 hospitalized children with respiratory tract infections from Janu-ary 2011 to December 2012 were recruited, and the serum levels of mycoplasma pneumoniae antibody Ig (MP-Ig) were measured. Meanwhile, monthly meteorological conditions were collected. The relationships between the MP-Ig detection rates and meteoro-logical conditions were analyzed by multiple linear regression analysis. Results The total detection rate of MP-Ig was 23.2%with positive rates as 5.51%, 28.99%, 37.31%and 44.97%for 0-1, 1-3, 3-6 and>6 year-old groups respectively (P<0.01). The positive rate of female was higher than that of male with signiifcant difference (30.08%vs 19.05%, P<0.01). The positive rate of spring, summer, autumn and winter were 18.89%, 17.39%, 23.83%and 33.05%individually (P<0.01). Negative correlation was found be-tween detection rate of MP-Ig and monthly mean air temperature (P=0.001). Conclusion MP is one of the commonest pathogens of respiratory tract infection in children and mostly seen in elder female children with a higher incidence in winter. The main me-teorological factor is the low temperature that affects MP prevalence.