Novel Biodegradable Composite of Calcium Phosphate Cement and the Collagen I Mimetic P-15 for Pedicle Screw Augmentation in Osteoporotic Bone

Osteoporotic vertebral fractures often necessitate fusion surgery, with high rates of implant failure. We present a novel bioactive composite of calcium phosphate cement (CPC) and the collagen I mimetic P-15 for pedicle screw augmentation in osteoporotic bone. Methods involved expression analysis of osteogenesis-related genes during osteoblastic differentiation by RT-PCR and immunostaining of osteopontin and Ca2+ deposits. Untreated and decalcified sheep vertebrae were utilized for linear pullout testing of pedicle screws. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DEXA). Expression of ALPI II (p < 0.0001), osteopontin (p < 0.0001), RUNX2 (p < 0.0001), and osteocalcin (p < 0.0001) was upregulated after co-culture of MSC with CPC-P-15. BMD was decreased by 28.75% ± 2.6%. Pullout loads in untreated vertebrae were 1405 ± 6 N (p < 0.001) without augmentation, 2010 ± 168 N (p < 0.0001) after augmentation with CPC-P-15, and 2112 ± 98 N (p < 0.0001) with PMMA. In decalcified vertebrae, pullout loads were 828 ± 66 N (p < 0.0001) without augmentation, 1324 ± 712 N (p = 0.04) with PMMA, and 1252 ± 131 N (p < 0.0078) with CPC-P-15. CPC-P-15 induces osteoblastic differentiation of human MES and improves pullout resistance of pedicle screws in osteoporotic and non-osteoporotic bone.

Properties of Sleeve Joints Made from Reduced Bamboo

Bamboo is a fast-growing species in the grass family, with excellent tensile and compressive strength characteristics, in the plant kingdom. The tapered hollow thin-walled cylindrical configuration of the bamboo species, namely, Gui bamboo (Phyllostachys makinoi Hayata) and Moso bamboo (Phyllostachys pubescens) culm, adversely influences its longitudinal shear and transversal tensile strength properties for effective use in engineered joints. The objective of this study is to use the thermo–hydro–mechanical (THM) process to reduce the irregular shape of bamboo ends without damaging the culms. Samples from the two abovementioned bamboo species were used for the experiments. Pullout loads and failure modes of the sleeve bamboo joints assembled by gluing were also evaluated. Eighty-nine out of 96 tested bamboo culms were successfully reduced by the THM treatment to uniform circular cross-sections under the maximum reduction ratio of 0.15. Sleeved-joint samples made from Gui bamboo with wood fittings had the highest pullout loads and strength values. Based on the findings in this work, it appears that THM-treated reduced bamboo ends, being a sustainable resource, could have the potential to be manufactured as steel-sleeve joints to be used for different engineering applications.

Behaviour of Granular Anchor Pile (Gap) and Group Piles in Different Type of Soils under Vertical Pullout Loads

In the present study, the load displacement behaviour of Granular Anchor Pile (GAP) and Group piles under vertical pullout loads in two different type of cohesionless soils have been investigated. The main objective of the study is to investigate the effect of embedment length, diameter and spacing varying (L/D and S/D ratio) on Pullout Capacity of Granular Anchor Pile system in different type of soils. GAP pile is innovative and effective in resisting the uplift pressure exerted on the foundation. Based on the laboratory study on single and group of 2 and 4 GAP systems, it is found that the ultimate Pullout Capacity of single GAP system increases with the increase in length (L) to diameter (D) ratio in both type of soils. The rate of increase of ultimate pullout capacity of single GAP systems having 50 mm diameter and 100 mm diameter was significant up to increase in L/D ratio of 39%. Thus, it was inferred that for single GAP system, there is maximum advantage upto L/D ratio 10.50 for 50 mm and 7.00 for 100 mm. In case of medium dense soil with higher relative density, the increase in pullout capacity is more as compared to loose soil with lower relative density. It was further confirmed that ultimate pullout capacity is a function of diameter of GAP and soil characteristics. The ultimate pullout capacity of group of 2 and 4 GAP systems with 100 mm diameter was found to increase with S/D ratio upto 3.00 and 2.75 respectively only in both the soils.

Vertical uplift resistance of horizontal plate anchors for eccentric and inclined loads

The vertical uplift resistance of horizontal plate anchors embedded in sand has been computed for inclined and eccentric pullout loads. The analysis has been performed by using the lower-bound theorem of the limit analysis in combination with finite element and second-order cone programming (SOCP). The methodology is based on the Mohr–Coulomb yield criterion and the associated flow rule. Several combinations of the eccentricity (e) and vertical inclinations (α) of the resultant pullout loads have been considered. The computations have revealed that the magnitude of the vertical uplift resistance decreases with an increase in the values of both e and α. The reduction of vertical pullout resistance with eccentricity and inclination becomes more prominent for smaller values of embedment ratio. The anchor–soil roughness angle (δ) hardly affects the uplift capacity factor as long as the value of α remains smaller than δ.