Background There are concerns regarding initial stability and cutout effect in proximal femoral nail antirotation (PFNA) treating intertrochanteric fractures. No study have used finite element analysis (FEA) to investigate the biomechanics. This study aimed to compare the cutout effect, stress and displacement between stable (AO31-A1.3) and unstable (AO31-A2.2) intertrochanteric fractures treated by cement augmented PFNA. Methods Four femoral finite element models (FEMs) were constructed and tested under the maximum loading during walking. Non-augmented and augmented PFNA in two different intertrochanteric fractures were respectively simulated, assuming Tip Apex Distance (TAD) < 25 mm within each FEM. The cutout effect, stress and displacement between femur and PFNA were compared in each condition. Results Cutout effect was observed in both non-augmented femoral head and was more apparently in unstable intertrochanteric fracture model. After reinforced by bone cement, no cutout effect occurred in two models. Stress concentration were observed on medial part of intertrochanteric region and the proximal part of helical blade before augmented while were observed on femoral shaft and the conjunction between blade and nail after augmented in both FEMs. Displacement mainly appeared on femoral head and the helical blade tip before augmented while distributed moderately on intertrochanteric region and the upper part of nail after augmented in both FEMs. The maximum stress and displacement value of femur decreased both in stable and unstable model after augmented but was more significantly in the unstable one. The maximum stress and displacement value of PFNA increased both in stable and unstable model after augmented but was more significantly in the unstable one. Conclusion Our FEA study indicated that the cement augmentation of the PFNA biomechanically enhances the cutout resistance in intertrochanteric fracture, this procedure is especially efficient for the unstable intertrochanteric fracture.

Background Medial compartment knee osteoarthritis (KOA) accounts for most KOA cases, and increased trabecular bone volume fraction (BV/TV) is one of the pathological changes in the tibial plateau of KOA. How BV/TV changes before and after the menopause and its effects on medial compartment KOA are yet to be clarified. Methods Twenty femurs from twenty 12-week-old rats were included. The operated group underwent ovariectomy (to represent the osteoporosis condition), called the O group, and the non-operated group was the normal control, called the N group. Micro-CT scans of the femoral condyles were acquired 12 weeks after the surgery, and the volume of interest (VOI) of medial-, inter-, and lateral-condyle trabeculae were three-dimensional (3D) printed for uniaxial compression mechanical test and simulated by the finite element (FE) method. Results The results demonstrated that the O group indicated poorer trabecular architecture than the N group in three parts of the femoral condyle, especially in the intercondyle. Within the group, the BV/TV, trabecular thickness (Tb.Th), and trabecular number (Tb.N) ratios between the medial and lateral condyles were greater than 1 in both N and O groups. The medial condyle trabeculae's mechanical properties were higher than those of the lateral condyle, and this superiority appears to be broadened under osteoporotic conditions. FE modelling well reproduced these mechanical differentiations. Conclusions According to Wolff's law, the higher BV/TV and mechanical properties of the medial femoral condyle may be due to inherent imbalanced loading on the knee component. Alterations in BV/TV and their corresponding mechanical properties may accompany KOA.

Background Unroofed coronary sinus syndrome (UCSS) is a rare cardiovascular malformation with nonspecific clinical manifestations that easily causes misdiagnosis and missed diagnosis. The aim of this study is to present the different features of UCSS by various CCT (cardiac CT) postprocessing techniques and evaluate the diagnostic advantages of CCT. Methods 9 UCSS patients who were diagnosed by imaging and undergone both CCT and transthoracic echocardiography (TTE) were included in this study, and their CCT images were reviewed. The UCSS images were classified by multiplanar reformations, maximum intensity projection, volume rendering and cinematic rendering. The size of CS roof defect was also measured. Results Only 4 of 9 CCT confirmed UCSS patients were detected by TTE (4/9, 44.4%), the sensitivity of TTE was lower compared to CCT by Fisher’s exact test (P < 0.05). UCSS was classified according to the Kirklin and Barratt Boyes’s method, including 1 case was classified as type I, 4 cases as type II, 1 case as type III, 2 cases as type IV, 1 case as type V (variant type), and TTE was undiagnosed in all type III-V patients. Additionally, CCT showed 12 extra malformations in these patients, only 5 of them were found by TTE (5/12, 41.7%), and TTE missed all extracardiac malformations. The mean size of CS roof defect was 3.04 ± 1.57 cm. Conclusions CCT with various postprocessing technologies has excellent value in diagnosing and differentiating subtypes of UCSS, measuring size of coronary sinus defect, describing accompanying cardiovascular abnormalities.

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