Dynamic Alterations in Microarchitecture, Mineralization and Mechanical Property of Subchondral Bone in Rat Medial Meniscal Tear Model of Osteoarthritis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The properties of subchondral bone influence the integrity of articular cartilage in the pathogenesis of osteoarthritis (OA). However, the characteristics of subchondral bone alterations remain unresolved. The present study aimed to observe the dynamic alterations in the microarchitecture, mineralization, and mechanical properties of subchondral bone during the progression of OA.</p><p><b>METHODS</b>A medial meniscal tear (MMT) operation was performed in 128 adult Sprague Dawley rats to induce OA. At 2, 4, 8, and 12 weeks following the MMT operation, cartilage degeneration was evaluated using toluidine blue O staining, whereas changes in the microarchitecture indices and tissue mineral density (TMD), mineral-to-collagen ratio, and intrinsic mechanical properties of subchondral bone plates (BPs) and trabecular bones (Tbs) were measured using micro-computed tomography scanning, confocal Raman microspectroscopy and nanoindentation testing, respectively.</p><p><b>RESULTS</b>Cartilage degeneration occurred and worsened progressively from 2 to 12 weeks after OA induction. Microarchitecture analysis revealed that the subchondral bone shifted from bone resorption early (reduced trabecular BV/TV, trabecular number, connectivity density and trabecular thickness [Tb.Th], and increased trabecular spacing (Tb.Sp) at 2 and 4 weeks) to bone accretion late (increased BV/TV, Tb.Th and thickness of subchondral bone plate, and reduced Tb.Sp at 8 and 12 weeks). The TMD of both the BP and Tb displayed no significant changes at 2 and 4 weeks but decreased at 8 and 12 weeks. The mineral-to-collagen ratio showed a significant decrease from 4 weeks for the Tb and from 8 weeks for the BP after OA induction. Both the elastic modulus and hardness of the Tb showed a significant decrease from 4 weeks after OA induction. The BP showed a significant decrease in its elastic modulus from 8 weeks and its hardness from 4 weeks.</p><p><b>CONCLUSION</b>The microarchitecture, mineralization and mechanical properties of subchondral bone changed in a time-dependent manner as OA progressed.</p>

Wear analysis and diagnostic reasoning on clinical failure of artificial hip joints / 医用生物力学

Objective To investigate the wear mechanism of artificial hip joints and the criteria for wear life definition, analyze the causes of abnormal wear and the clinical manifestations of wear failure, establish the reasoning route of failure incidents. Methods The wear process and early factors on abnormal wear in artificial hip joints were studied through elastohydrodynamic lubrication computation and finite element analysis; the service life of artificial hip joints was determined through establishing criteria for wear life definition; the clinical manifestations of wear failure were introduced and classified through wear-osteolysis morphological matrix; the reasoning logic of failure incidents was established through clinical investigation. Results The minimal synovium thickness and contact stress between the femoral head and the acetabular cup were calculated, and the effect of relevant parameters was studied as theoretical references for wear analysis; the criteria on wear life definition of artificial hip joints were proposed, namely the mechanistic failure due to geometric change in artificial hip joints and the biological failure due to osteolysis; nine kinds of clinical manifestation for wear failure were found; the reasoning route for failure incidents was presented. Conclusions Primary wear process in artificial hip joints includes boundary and mixed friction, adhesive, ploughing and third-body wear; surface quality, fit clearance between the acetabular cup and the femoral head, and roundness have great impact on early abnormal wear; normal mechanistic life of metal-UHMWPE artificial hip joint can reach 40 years, but its maximum biological life is no more than 10-15 years, which is the constraint of prosthesis life today; the diversity of clinical manifestations for wear failure is the morphological Results of mechanical wear and osteolysis, which is helpful for the reasoning route of failure incidents.

Mechanical analysis and reasoning on fractured stem failure after total hip arthroplasty / 医用生物力学

Objective To propose some detailed methods for diagnosis of fractured stem failure in clinic by studying the mechanical mechanism of fractured stem failure and the specific causes of fracture occurrence after the total hip arthroplasty (THA). Methods The correlations between fracture stem failure and production, clinical situation and patients were analyzed by 2D and 3D finite element analysis (FEA) method to study the biomechanical mechanism of fracture processes. Results The reasoning route for fractured stem failure analysis after THA was proposed, and mechanical analysis and validation on fractured stem failure were conducted by FEA methods successfully. Conclusions Fracture should not occur on the artificial stem, for those that gone through the strength design and experimental test; statistical analysis on fractured stem failure showed that the occurrence of such fractured stem is a kind of little probability random event, which could be induced by a variety of non-normal factors, such as fluctuations in product quality, technical errors in clinic, patient accidents and so on. Strict controls on these factors can reduce the fractured stem occurrence; the reasoning route for fractured stem failure can help to discover the reasons of failure occurrence; the mechanical mechanism of specific fracture stem occurrence can be detected by 2D and 3D FEA methods.

Effect of impaction on gene-modified cells seeded on granular bone allografts in vitro and in vivo / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>While attempting to restore bone stock, impaction bone grafting employed during revision joint surgery may result in slow and limited allograft incorporation into host bone. A new approach including gene-modified bone marrow stromal cells (BMSCs) in combination with impaction bone grafting may effectively restore bone stock and improve allograft incorporation. This study aimed to investigate the effect of impaction on gene-modified BMSCs seeded on granular bone allografts in vitro and in vivo.</p><p><b>METHODS</b>Deep-frozen, granular, cancellous bone allografts from canines were prepared to serve as cell delivery scaffolds and were seeded with green fluorescent protein (GFP) genetically-modified BMSCs to construct cell-allograft composites. The composites were impacted in a simulative, in vitro impaction model and cultured for further analysis under standard conditions. Four Beagle dogs, treated with bilateral, uncemented proximal tibial joint hemiarthroplasty with a prosthesis, were implanted with autologous GFP gene-modified cell-allograft composites to repair the bone cavity around each prosthesis.</p><p><b>RESULTS</b>A significant reduction in cell viability was observed after impaction by fluorescence microscopy in vitro. However, there remained a proportion of GFP-positive cells that were viable and functionally active, as evidenced by the secretion of GFP protein in vitro and in vivo.</p><p><b>CONCLUSIONS</b>Gene-modified BMSCs seeded on granular allografts were able to withstand the impaction forces and to maintain their normal functions in vitro and in vivo, in spite of a partial loss in cell viability.</p>

In vitro study of knee stability after two-band two-tunnel posterior cruciate ligament reconstruction / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To compare the ability of three different reconstruction procedures in restoring the posterior displacement of tibia and the posterior stability of the knee joint from 0 degree to 120 degrees flexion.</p><p><b>METHODS</b>Three posterior cruciate ligaments (PCL) reconstruction procedures were performed, namely two-band two-tunnel reconstruction, one-band anterior tunnel reconstruction and one-band posterior tunnel reconstruction. The posterior displacement of the tibia in relation to the femur was measured when a 200N posterior force was applied.</p><p><b>RESULTS</b>Within the flexion range of 0 degree to 30 degrees, the displacement in the one-band posterior tunnel reconstruction showed little difference from that of an intact knee (P>0.05). But when the flexion exceeded 30 degrees, especially when it exceeded 60 degrees, the displacement in one-band posterior tunnel reconstruction was much greater than that of an intact knee (P<0.01). In two-band two-tunnel reconstruction and one-band anterior tunnel reconstruction, the displacement was approximately the same as that of an intact knee ranging from 0 degree to 120 degrees (P>0.05), while a slight over-restriction might be found at some angles.</p><p><b>CONCLUSIONS</b>Two-band reconstruction could effectively restrict the posterior displacement of the tibia and restore anterior, posterior stability of the knee joint within its full range of flexion. One-band anterior tunnel reconstruction also could maintain the posterior stability of the knee, while the result of one-band posterior tunnel reconstruction is the most unsatisfactory.</p>

The effect of ultra high molecular weight polyethylene particles on macrophage / 中华外科杂志

<p><b>OBJECTIVE</b>To study the effect of ultra high molecular weight polyethylene (UHMWPE) particles on macrophages and evaluate the expression of NFAT2, a key transcriptional factor for osteoclast differentiation.</p><p><b>METHODS</b>From November 2004 to February 2005, macrophages were co-cultured with UHMWPE particles. When observed at different times, the proliferation activity of macrophages was analyzed by MTT and the expression of calcineurin (CaN) and NFAT2 by immunohistochemical and RT-PCR method respectively.</p><p><b>RESULTS</b>The macrophages phagocytosed UHMWPE particles in an early time, the expression of CaN and NFAT2 was increased, while the proliferation activity was not enhanced.</p><p><b>CONCLUSIONS</b>UHMWPE particles can stimulate macrophages to phagocytose significantly, and enhance the expression of the transcriptional factor NFAT2.</p>

Effect of Ti-6AL-4V particles on morphology and function of osteoclasts:an in vitro study / 中华创伤杂志

Objective To observe the effect of Ti-6AL-4V particles on morphological and func- tional changes of osteoclast in vitro.Methods Mature osteoclasts separated from New Zealand Rabbits were cultured on glass slices and cortical bone slices.The experimental group was stimulated by Ti-6AL- 4V particles at concentration of 0.1 mg/ml.The cells were stained with TRAP at different culture time to observe the morphological variety.The bone resorption pits on bone slices were stained by toluidine blue and the resorption areas analyzed by computer image analysis software.Results Osteoclasts phagocy- tosed the particles,with irregular shapes,deeper TRAP stain and earlier apoptosis.Stimulation by Ti- 6AL-4V particles brought about larger area of bone absorption lacuna.Conclusion Osteoclasts have the ability to phagocytose Ti-6AL-4V particles,which leads to morphological and functional changes and enhances bone resorption.