Physical and mechanical characterization of PLLA interference screws produced by two stage injection molding method

Abstract

The purpose of this study was to produce and evaluate different mechanical, physical and in vitro cell culture characteristics of poly(L-lactic) acid (PLLA) interference screws. This work will focus on evaluating the effect of two important parameters on operation of these screws, first the tunnel diameter which is one of the most important parameters during the operation and second the thermal behavior, the main effective characteristic in production process. In this work, PLLA screws were produced by a two-stage injection molding machine. For mechanical assessment of the produced screws, Polyurethane rigid foam was used as cancellous bone and polypropylene rope as synthetic graft to simulate bone and ligament in real situation. Different tunnel diameters including 7–10 mm were evaluated for fixation strength. When the tunnel diameter was changed from 10 to 9 mm, the pull-out force has increased to about 12 %, which is probably due to the aforementioned frictional forces, however, by reducing the tunnel diameter to 8 and 7 mm, the pull-out force reduced to 16 and 50 % for 8 and 7 mm tunnel diameter, respectively. The minimum and maximum pull-out force was obtained 160.57 and 506.86 N for 7 and 9 mm tunnel diameters, respectively. For physicochemical assay, Fourier transform infrared spectroscopy (FTIR), degradation test and differential scanning calorimetry (DSC) were carried out. The crystallinity (Xc) of samples were decreased considerably from 64.3 % before injection to 32.95 % after injection with two different crystallographic forms α′ and α. probably due to the fast cooling rate at room temperature. In addition, MTT and cell attachment assays were utilized by MG63 osteoblast cell line, to evaluate the cytotoxicity of the produced screws. The results revealed no cytotoxicity effect.

Design, development, in-vitro and in-vivo evaluation of polylactic acid-based multifunctional nanofibrous patches for efficient healing of diabetic wounds

“…Moreover, asymmetric and symmetric C–H stretchings were detected through two moderate peaks appearing at 2990 cm −1 and 2994 cm −1 , respectively. All the obtained IR peaks of PLLA NFs are in agreement with that have been reported in the literature 48 , 57 – 59 .…”

Kinetics of slow release of nitrogen fertiliser from multi-layered nanofibrous structures

“…Characteristic peaks of PLLA form at 1090–1190 cm −1 (ester bond), a middle peak at 1362 cm −1 (–CH3 symmetric bending vibration), and two peaks at 2997 and 2947 cm −1 (methyl groups) 23 . A characteristic strong peak of PLLA at about 1750 cm −1 is related to the stretching vibration of the carbonyl group (C=O) shifted slightly from 1755 cm −1 24 . In the FTIR spectra of urea, the peak in the region of 1629–1680 cm −1 is due to the C=O stretching bond of urea and the presence of absorption peaks at 3344, 3447 and 1157 cm −1 can be associated to the stretching vibration of N–H bonds 25 .…”

Development of bone screw using novel biodegradable composite orthopedic biomaterial: from material design to in vitro biomechanical and in vivo biocompatibility evaluation

“…The test protocol to assess the pull-out performance of bioabsorbable bone screw with SAWBONES synthetic bone blocks (Pacific Research Laboratories, Inc., WA, USA) was selected for biomechanical testing according to ASTM specification F1839-08 [22]. Total 10 bone blocks (10 pcf, 160 kg m −3 density) were utilized as a cancellous bone substitute [23], 5 for each test group (PCL and composite bone screws). Pull-out testing jigs were fixed to tensile testing machine (Instron 3345) (figure S2).…”