A posterior tibial slope angle over 12 degrees is critical to epiphyseal fracture of the proximal tibia: Three-dimensional finite element analysis

Introduction

The effects of the proximal tibial slope angle on the proximal tibial epiphysis remain unknown. To elucidate those effects, we investigated the strain distribution in proximal tibial epiphysis with different proximal tibial slope angles and proximal tibial epiphysis closure periods using finite element analysis.

Materials and methods

The finite element models of the proximal tibia were reconstructed from CT images and consisted of cancellous/cortical bone and epiphyseal plate. The variations in proximal tibial slope angle (range: 6-16°) and four closure variations in proximal tibial epiphysis (open, semi-open, semi-closed, and closed) were prepared. The loading force on the medial and lateral joint surface, and the tensile force by the patellar tendon were applied to the models, and the distal area of the tibia was fixed. The ratio of the equivalent strain in semi-open/semi-closed proximal tibial epiphysis to the strain in open proximal tibial epiphysis on different proximal tibial slope angles were calculated.

Results

The strain ratio between the semi-open/semi-closed and open proximal tibial epiphysis models indicated significant differences between 6 or 8° of proximal tibial slope angle and 12, 14, and 16° of proximal tibial slope angle models. In the increased proximal tibial slope angle model, a hoop-shaped strain in the closing proximal tibial epiphysis was found, and the maximum strain was found in the tibial tubercle.

Discussion

During epiphyseal closure, adolescents with an increased proximal tibial slope angle over 12° are significantly at risk for suffering from proximal tibial epiphyseal fractures compared with those under 10°.

Degradation of starch in pasta induced by extrusion below gelatinization temperature

The structural deformation of starch during pasta extrusion leads to varied effects on pasta quality. We investigated the impact of shearing force on the starch structure of pasta and pasta quality by varying the screw speed (100, 300, 500 and 600 rpm) with a temperature range of 25 to 50 ℃ in increments of 5 ℃, from the feeding zone to the die zone. The higher screw speeds were associated with more specific mechanical energy input (157, 319, 440, and 531 kJ/kg for pasta produced at 100, 300, 500 and 600 rpm, respectively), resulting in a lower pasting viscosity (1084, 813, 522 and 480 mPa·s for pasta produced at 100, 300, 500 and 600 rpm, respectively) in the pasta due to the loss of starch molecular order and crystallinity. Size-exclusion chromatography revealed that pasta produced at 600 rpm screw speed had a lower amylopectin size distribution which indicated molecular breakdown during extrusion. Pasta produced at 600 rpm had higher in vitro starch hydrolysis (both raw and cooked) than the pasta made at 100 rpm. The research provides relationship of how the screw speed can be manipulated to design pasta with varied texture and nutritional functionality.