BACKGROUND:Unicompartmental knee arthroplasty can effectively treat severe unilateral knee osteoarthritis.It has been found that posterior tibial cortical fracture is prone to occur after unicompartmental knee arthroplasty.The fracture begins at the keel groove of tibial osteotomy.The tibial prosthesis riser length affects the biomechanical results of the knee joint after unicompartmental knee arthroplasty. OBJECTIVE:To investigate the effect of tibial prosthesis riser length on knee biomechanics in unicompartmental knee arthroplasty,and to find out the relationship between prosthesis riser length and anterior and posterior tibial diameters of patients. METHODS:Computed tomography image data and commonly used unicompartmental prostheses were selected from a 37-year-old healthy female with no history of knee disease.A natural knee joint model was established and a unicompartmental prosthesis model was built.Eight different lengths of tibial prosthesis risers were established,with a minimum length of 31 mm and a maximum length of 34.5 mm in 0.5 mm increments,for comparison with the commonly used hospital prosthesis riser length of 33.2 mm.The material of the femoral component and tibial disc was cobalt-chromium-molybdenum alloy,and the tibial spacer was ultra-high molecular weight polyethylene.The biomechanical changes of the knee joint were observed using finite element analysis software loaded with 1000 N over the femur. RESULTS AND CONCLUSION:(1)The tibial stress was minimal at a tibial prosthesis riser length of 33 mm;the anterior cruciate ligament stress was minimal;the lateral meniscus stress was minimal,and the femoral prosthesis stress was minimal.The remaining components were less stressful.(2)The subject's medial tibial plateau anterior-posterior diameter length was 53 mm,and by calculating the ratio,the optimal ratio of tibial prosthesis riser length to anterior-posterior tibial diameter should be about 62%.If it is lower than this value,aseptic loosening of the prosthesis may occur,and if it is higher than this value,fracture of the bone cortex at the anterior-posterior end of the tibia may occur.

In unicompartmental replacement surgery, there are a wide variety of commercially available unicompartmental prostheses, and the consistency of the contact surface between the common liner and the femoral prosthesis could impact the stress distribution in the knee after replacement in different ways. Medial tibial plateau fracture and liner dislocation are two common forms of failure after unicompartmental replacement. One of the reasons is the mismatch in the mounting position of the unicompartmental prosthesis in the knee joint, which may lead to failure. Therefore, this paper focuses on the influence of the shape of the contact surface between the liner and the femoral prosthesis and the mounting position of the unicompartmental prosthesis on the stress distribution in the knee joint after replacement. Firstly, a finite element model of the normal human knee joint was established, and the validity of the model was verified by both stress and displacement. Secondly, two different shapes of padded knee prosthesis models (type A and type B) were developed to simulate and analyze the stress distribution in the knee joint under single-leg stance with five internal or external rotation mounting positions of the two pads. The results showed that under a 1 kN axial load, the peak contact pressure of the liner, the peak ACL equivalent force, and the peak contact pressure of the lateral meniscus were smaller for type A than for type B. The liner displacement, peak contact pressure of the liner, peak tibial equivalent force, and peak ACL equivalent force were the smallest for type A at 3° of internal rotation in all five internal or external rotation mounting positions. For unicompartmental replacement, it is recommended that the choice of type A or type B liner for prosthetic internal rotation up to 6° should be combined with other factors of the patient for comprehensive analysis. In conclusion, the results of this paper may reduce the risk of liner dislocation and medial tibial plateau fracture after unicompartmental replacement, providing a biomechanical reference for unicompartmental prosthesis design.
Arthroplasty, Replacement, Knee/methods* ; Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Knee Joint/surgery* ; Knee Prosthesis ; Tibia/surgery*

OBJECTIVE: To realize the risk factors, clinical features, and treatments of Staphylococcal scalded skin syndrome (SSSS).
 METHODS: The clinical features, laboratory findings, and treatment were retrospectively analyzed in 290 patients from Hunan Children's Hospital.
 RESULTS: Of the 290 patients, less than 3 years old children were 76.6%. One hundred and nine patients had induced factors, and 177 patients had elevated white blood cell count. There were 168 patients with SSSS accompanied with fever, 34 patients accompanied with diarrhea, and 58 patients associated with septicemia. Eighty-five patients performed the bacterial cultures of the skin secretions, 21 did the throat swab, and 13 did both of the skin secretions and throat swab. Bacterial culture results showed that 119 samples were positive for Staphylococci. All patients were cured after antimicrobial therapy. The skin lesions were improved in 3.26 d. The mean hospital stay was 6.55 d. Recovery time of the body temperature was 3.48 d in average.
 CONCLUSION SSSS predominates in infants and children under 3 years old, and has tendency to combine with multi-organ symptoms. The early diagnosis and active antimicrobial treatment are the keys of successful treatments.
Anti-Bacterial Agents ; therapeutic use ; Child, Preschool ; China ; Humans ; Infant ; Length of Stay ; Retrospective Studies ; Risk Factors ; Sepsis ; Skin ; microbiology ; Staphylococcal Scalded Skin Syndrome ; diagnosis ; drug therapy ; pathology