Design Improvements and Validation of a Novel Fully 3D Printed Analogue Lumbar Spine Motion Segment

Spine biomechanical testing methods in the past few decades have not evolved beyond employing either cadaveric studies or finite element modeling techniques.However,both these approaches may have inherent cost and time limitations.Cadaveric studies are the present gold standard for spinal implant design and regulatory approval,but they introduce significant variability in measurements across patients,often requiring large sample sizes.Finite element modeling demands considerable expertise and can be computationally expensive when complex geometry and material nonlinearity are introduced.Validated analogue spine models could complement these traditional methods as a low-cost and high-fidelity alternative.A fully 3D printable L-S1 analogue spine model with ligaments is developed and validated in this research.Rotational stiffness of the model under pure bending loading in flexion-extension,Lateral Bending(LB)and Axial Rotation(AR)is evaluated and compared against historical ex vivo and in silico models.Additionally,the effect of interspinous,intertransverse ligaments and the Thoracolumbar Fascia(TLF)on spinal stiffness is evaluated by systematic construction of the model.In flexion,model Range of Motion(ROM)was 12.92±0.11°(ex vivo:16.58°,in silico:12.96°)at 7.5Nm.In LB,average ROM was 13.67±0.12°at 7.5 Nm(ex vivo:15.21±1.89°,in silico:15.49±0.23°).Similarly,in AR,average ROM was 17.69±2.12°at 7.5Nm(ex vivo:14.12±0.31°,in silico:15.91±0.28°).The addition of interspinous and intertransverse ligaments increased both flexion and LB stiffnesses by approximately 5%.Addition of TLF showed increase in flexion and AR stiffnesses by 29%and 24%,respectively.This novel model can reproduce physiological ROMs with high repeatability and could be a useful open-source tool in spine biomechanics.

Histone demethylase Kdm5c regulates osteogenesis and bone formation via PI3K/Akt/HIF1α and Wnt/β-catenin signaling pathways

Fractures have an extraordinarily negative impact on individuals'quality of life and functional status.Nonunion or disability of fracture is a major health issue with important clinical,social,and economic implications.1 Mesenchymal stem cells(MSCs)play an indispensable role in the initiation of the fracture repair process including the formation of a callus which is replaced by new bone.The use of MSCs in the treatment of fractures is very attractive as they can reduce the time of healing and occurrence of nonunion.

Biosynthesis of Bioadaptive Materials:A Review on Developing Materials Available for Tissue Adaptation

Biomaterials are increasingly being evolved to actively adapt to the desired microenvironments so as to introduce tissue integration, reconstruct stability, promote regeneration, and avoid immune rejection. The complexity of its mechanisms poses great challenge to current biomimetic synthetic materials. Although still at initial stage, harnessing cells, tissues, or even entire body to synthesize bioadaptive materials is introducing a promising future.

Biocompatibility and degradation comparisons of four biodegradable copolymeric osteosynthesis systems used in maxillofacial surgery: A goat model with four years follow-up

pplying biodegradable osteosyntheses avoids the disadvantages of titanium osteosyntheses. However, foreign-body reactions remain a major concern and evidence of complete resorption is lacking. This study compared the physico-chemical properties, histological response and radiographs of four copolymeric biodegradable osteo-synthesis systems in a goat model with 48-months follow-up. The systems were implanted subperiosteally in both tibia and radius of 12 Dutch White goats. The BioSorb FX [poly(70LLA-co-30DLLA)], Inion CPS [poly([70–78.5] LLA-co-[16–24]DLLA-co-4TMC)], SonicWeld Rx [poly(DLLA)], LactoSorb [poly(82LLA-co-18GA)] systems and a negative control were randomly implanted in each extremity. Samples were assessed at 6-, 12-, 18-, 24-, 36-, and 48-month follow-up. Surface topography was performed using scanning electron microscopy (SEM). Differential scanning calorimetry and gel permeation chromatography were performed on initial and explanted samples. Histological sections were systematically assessed by two blinded researchers using (polarized) light microscopy, SEM and energy-dispersive X-ray analysis. The SonicWeld Rx system was amorphous while the others were semi-crystalline. Foreign-body reactions were not observed during the complete follow-up. The SonicWeld Rx and LactoSorb systems reached bone percentages of negative controls after 18 months while the BioSorb Fx and Inion CPS systems reached these levels after 36 months. The SonicWeld Rx system showed the most predictable degradation profile. All the biodegradable systems were safe to use and well-tolerated (i.e., complete implant replacement by bone, no clinical or histological foreign body reactions, no [sterile] abscess formation, no re-interventions needed), but nanoscale residual polymeric fragments were observed at every system’s assessment.