We developed a three-dimensional finite element model of the shoulder glenohumeral joint after shoulder arthroplasty including humerus shaft, scapular, scapular cartilage and eight muscles, while each of the muscles was simulated with 50 spring elements. To reduce the element number and improve the analytical precision, we used mixed tetrahedral and hexahedral elements in the model. We then used the model to calculate the biomechanics of the shoulder glenohumeral joint after hemiarthroplasty during humeral external rotation. Results showed that the maximum joint reaction force was 374.72 N and the maximum contact stress was 6.573 MPa together with the contact areas at 40° external rotation. These might be one of the reasons for prosthetic disarticulation, and would provide theoretical bases to prosthetic design.
We developed a three-dimensional finite element model of development dysplasia of hip (DDH) of a patient. And then we performed virtual Bernese periacetabular osteotomy (PAO) by rotating the acetabular bone with different angle so as to increase femoral head coverage and distribute the contact pressure over the cartilage surface. Using finite element analysis method, we analyzed contact area, contact pressure, and von Mises stress in the acetabular cartilage to determine the effect of various rotation angle. We also built a normal hip joint model. Compared to the normal hip joint model, the DDH models showed stress concentration in the acetabular edge, and higher stress values. Compared to the DDH models, the post-PAO models showed decreases in the maximum values of von Mises stress and contact pressure while we increased the contact area. An optimal position could be achieved for the acetabulum that maximizes the contact area while minimizing the contact pressure and von Mises stress in the acetabular cartilage. These would provide theoretical bases to pre-operative planning.
Objective To investigate the initial drug resistance of Mycobacterium tuberculosis ( M.tuberculosis) in patients with culture positive pulmonary tuberculosis. Methods 1184 patients who hospitalized in Shandong Provincial Chest Hospital with culture positive pulmonary tuberculosis were enrolled. The absolute density method was used to assess the drug resistance of M. tuberculosis. Results M.tuberculosis were sensitive to all anti-tuberculosis drugs in 834 cases( 70. 44% ) , and resistant in 350 cases( 29. 56% ) , in which initial resistance and secondary resistance accounted for 44. 86% ( 157/350) and 55. 14% ( 193 /350) respectively. In 157 cases with initial resistance, 53 cases ( 33. 8% ) were mono-drug resistant tuberculosis( MonoDR-TB) , of which 38 cases were resistance to Streptomycin( 24. 2% ) ; 72 cases( 45. 9% ) were polydrug-resistant tuberculosis ( PDR-TB) ; 20 cases ( 12. 7% ) were multidrug-resistant tuberculosis ( MDR-TB) ; 12 cases ( 7. 6% ) were extensively drug resistant tuberculosis ( XDR-TB) . There was no totally drug-resistant tuberculosis ( TDR-TB) . Conclusions The initial drug resistance of M.tuberculosis in patients with pulmonary tuberculosis is still serious. Unified management of TB control programs and full supervision of chemotherapy are very imperative.