Periprosthetic osteolysis and aseptic loosening after total hip arthroplasty are the common causes for revision surgery,which are initiated by wear particles released from the articular surfaces of prosthetic components.These components include ultra-high molecular weight polyethylene,titanium alloy,Al2O3,ZrO2 and polymethylmethacrylate.Wear particles activate macrophage via phagocytosis or pattern recognition receptor,resulting in release of inflammatory mediators such as macrophage colony-stimulating factor (M-CSF),macrophage chemotactic protein-1 (MCP-1),macrophage inhibitory protein-1 (MIP-1),IL-1β,IL-6 and TNF-α.Furthermore,wear particles stimulate M0 macrophage to polarize to M1 macrophage,promoting the release of inflammatory mediators.The periprosthetic osteolysis process is a cell/cytokine-mediated biological cascade induced by macrophage activation,involving the monocyte/macrophage cell line,such as macrophages,osteoclasts,and dendritic cells.The mesenchymal cells,including osteoblasts,osteocytes,fibroblasts and lymphocytes,lead to a deviation in the balance of osteoblast-osteoclast interactions within the basic multicellular unit,resulting in periprosthetic osteolysis.Fibrobalst,dendritic,and lymphocyte cells can enhance the recruitment and activation of macrophages by secreting MCP-1,MIP-1,and IL-8.Furthermore,the upregulated expression of RANKL,TNF-α,and IL-1 β facilitates the osteoclast differentiation from osteoclast precursor.TNF-α,IL-1 β together with wear particles can upregulate the expression of IL-6,MCP-1 and M-CSF of osteoblast and promote the recruitment and activation of macrophages.Nuclear transcriptional factor NF-κB plays a vital role in mediating periprosthetic inflammatory response and gene expression of bone metabolism.Different inflammatory factors can induce different expression of its downstream gene,ultimately,promoting or hindering the osteolysis process.The individual difference of periprosthetic osteolysis may also relate to single nucleotide polymorphism of IL-1RA,IL-6 and MMP-1 gene.

Objective To assess the bone tunnel area at different times and sites of the tunnel after the anterior cruciate ligament(ACL) reconstruction in rabbits using Micro-CT.Methods Fifteen rabbits were performed ACL reconstruction using semitendinosus tendon autograft and randomly allocated into 3 groups and killed at 3,6,and 12 weeks after the operation.All samples undertook the micro-CT scanning(using SkyScan 1176,Bruker,U.S.A.) and were analyzed the areas of bone tunnels of femur and tibia after the 3-demension image rebuilding.For each tunnel,the area of the entrance,middle and exit of the tunnel were measured 3 times respectively and compared.Results The average area of the femoral tunnel did not change significantly with time,being 4.84 mm2,4.57 mm2 and 4.46 mm2 at 3,6 and 12 weeks after the operation(P=0.99).At the very beginning,the femoral tunnel area at the entrance was the biggest,while that of the middle was the smallest.Six weeks after the operation,significant differences were observed between the femoral tunnel area at the entrance and middle,as well as that between the exit and middle(P=0.0011,P=0.0106);However,12 weeks after the operation,significant differences were observed only between that at the entrance and middle(P=0.0227).The average tibial tunnel area increased significantly at 6 weeks(6.577 mm2) and decreased at 12 weeks(3.103 mm2) after the operation(P=0.0005).Moreover,no significant differences were observed in the average tibial tunnel area at different time points and sites(P＜0.05).At different sites,the average tibial tunnel area expanded at 6 weeks,and then declined at 12 weeks after the operation.Conclusion The bone tunnel area changes with time after the ACL reconstruction,first increasing followed by decreasing in the average tibial tunnel area.The femur and tibial tunnel have significant differences in the tunnel area at different sites,which change differently with time.The bone tunnel expansion after the anterior cruciate ligament reconstruction can be comprehensively measured repeatedly at different sites.

Ojective To explore the effect of the hydroxyapatite(HAp)and gelatin(Gel)coating on the healing of the polyethylene terephthalate(PET)artificial ligament.Methods The artificial ligaments were divided into a PET group with a pure PET surface and a PET/HAp/Gel group coated with HAp and Gel.Both coatings were observed using the scanning electron microscope(SEM).Forty-eight male New Zealand rabbits were randomly divided into two groups and underwent anterior cruciate ligament reconstruction,before two kinds of artificial ligaments were implanted respectively.Four weeks and 8 weeks after the operation,the rabbits were sacrificed,and histological hematoxylin and eosin (HE)staining as well as the biomechanical examination were performed.Results HAp/Gel coating was found depositing on the surface of PET artificial ligaments.Histological HE staining showed a thick fibrous connective tissue forming at the graft-host bone interface 4 weeks postoperatively,and the interface width of both groups were narrowed,with significantly more shrinking in the PET/HAp/Gel coating group.And new bone tissues were found in the interface of PET/HAp/Gel group 8 weeks after the operation.The biomechanical examination found significant differences in the failure load between the PET(46.16 ± 2.88 N) and PET/HAp/Gel group(71.32 ± 3.92 N)8 weeks after the surgery(P=0.0021).And 4 weeks and 8 weeks after the surgery,significant differences were found in the stiffness between the PET group and the PET/HAp/Gel group(11.06 ± 1.14 N/mm vs 16.20 ± 1.17 N/mm,P=0.0199;14.37 ± 0.88 N/mm vs 24.35 ± 1.35 N/mm,P=0.0008).Conclusion HAp/Gel coating can enhance the osteogenesis of PET artificial ligaments,promoting the new bone formation at the graft-host bone interface and herein strengthening the graft-host bone healing.