Effects of bone morphogenetic protein on the osseointegration of porous-surfaced implants:An experimental study in rabbits

Objective： Research on enhancing early osseointegration of cementless implants to improve early fixation and reducing of risk of loosening. Methods ： Thirty New Zealand rabbits were divided into two groups at random. BMP combined with DBM 30 mg was inserted around the prosthesis in 15 rabbits as experimental group, the remaining rabbits were served as control group. After 4, 8, and 12 weeks, five rabbits were sacrificed in each group. The humerus with the implants were retrieved. Bone ingrowth was analyzed by none-decalcification bone ground section and biomechanical test. Results： At the end of 4 and 8 weeks the osseointegration rates of BMP group were higher than those of control （P 〈 0.05）. The ultimate shear strength between BMP treated implantation and the control was the same as the results in osseointegration rates at 4, 8 weeks （P 〈 0.05）. However, there was no difference between the treated and untreated group in the osseointegration rate and ultimate shear strength at 12 weeks （P 〉 0.05）. Conclusion： BMP combination can enhance bone growth into gaps around cementless implants, especially in the early postoperative period.

Loss of the posteromedial support:a risk factor for implant failure after fixation of AO 31-A2 intertrochanteric fractures

Background:The purpose of this study was to analyze cases of AO31-A2 intertrochanteric fractures(ITFs)and to identify the relationship between the loss of the posteromedial support and implant failure.Methods:Three hundred ninety-four patients who underwent operative treatment for ITF from January 2003 to December 2017 were enrolled.Focusing on posteromedial support,the A2 ITFs were divided into two groups,namely,those with(Group A,n=153)or without(Group B,n=241)posteromedial support post-operatively,and the failure rates were compared.Based on the final outcomes(failed or not),we allocated all of the patients into two groups:failed(Group C,n=66)and normal(Group D,n=328).We separately analyzed each dataset to identify the factors that exhibited statistically significant differences between the groups.In addition,a logistic regression was conducted to identify whether the loss of posteromedial support of A2 ITFs was an independent risk factor for fixation failure.The basic factors were age,sex,American Society of Anesthesiologists(ASA)score,side of affected limb,fixation method(intramedullary or extramedullary),time from injury to operation,blood loss,operative time and length of stay.Results:The failure rate of group B(58,24.07%)was significantly higher than that of group A(8,5.23%)(χ2=23.814,P<0.001).Regarding Groups C and D,the comparisons of the fixation method(P=0.005),operative time(P=0.001),blood loss(P=0.002)and length of stay(P=0.033)showed that the differences were significant.The logistic regression revealed that the loss of posteromedial support was an independent risk factor for implant failure(OR=5.986,95%CI:2.667-13.432)(P<0.001).Conclusions:For AO31-A2 ITFs,the loss of posteromedial support was an independent risk factor for fixation failure.Therefore,posteromedial wall reconstruction might be necessary for the effective treatment of A2 fractures that lose posteromedial support.

Hydroxyapatite/β-tricalcium Phosphate Composite for Guiding Bone Tissue Growth into a Titanium Tube in 8 mm Dog Tibia Cavity Defects

We developed a fixation method and evaluate bone regrowth in the cavities of a Ф4 mm× 8 mm titanium（Ti）tube through porous hydroxyapatite（HAP）/β-tricalcium phosphate（β-TCP）composite filling（group A）,chitosan/calcium phosphate composite filling（group B）,and HAP particle modification（group C）.After 2 and 5 months of implantation in dog tibia defects,new bone formation in the three groups was studied by histology and histomorphometry.Group A displayed the most bone regenerated area in both 2 and 5 months post-operation.The chitosan/calcium phosphate composite in group B mostly degraded 2 months after implantation,leading to fibrous tissue invasion after 5 months.By contrast,less bone formation was observed in group C.These results indicated that filling the cavities of metalprostheses with a porous HAP/β-TCP composite can be used for stable long-term fixation in clinicalsettings.

Comparison of the biomechanical performance of three spinal implants for treating the wedge-shaped burst fractures

Spinal fracture is a serious problem impairing life quality,associating with low back pain and many other chronic diseases.Among all the spinal fractures,the rate of thoracolumbar fractures is the highest and accounts for approximately 90%.Although surgical treatment is an effective approach,it is still unclear which treatment method performs the best.The aim of the present study was to investigate the biomechanical performance of three spinal implants for treating the thoracolumbar wedge-shaped burst fractures using the finite element(FE)method.FE model of the T12/L1/L2 spinal segment was created from CT images and the thoracolumbar wedge-shaped burst fractures were created by removing some elements in the anterior part of L1.The FE models of the traditional system,the universal spine system(USS)and the cortical bone trajectory(CBT)system were created and their biomechanical performances were evaluated.The results revealed that among the three fixation systems,the highest von-Mises stress occurred in the CBT system.Under all the loading scenarios except for the lateral bending,the maximal von-Mises stress was higher when the USS system rather than the traditional system was applied.The average displacement around the fracture site was the highest in the CBT system.Except for the lateral bending,the average displacement around the fracture site was higher when the USS system rather than the traditional system was applied.For all the fixation approaches,the highest von-Mises stress always occurred at the screw junctions.The present study provided important data for the treatment of thoracolumbar wedge-shaped burst fractures.For example,the traditional spinal system is preferentially selected for the thoracolumbar wedgeshaped burst fracture of L1.