New β Ti alloy mini-prosthesis with low elastic modulus resurfacing articular surface defect in dogs

Objective To assess the effect of a new β Ti alloy mini-prosthesis with low elastic modulus on resurfacing the full-thickness Surface defect of the knee joint in dogs.Methods A full-thickness osteochondral defect of 7 mm in diameter was created at the medial femoral condyle of both hind limbs in 8 healthy adult dogs.The titanium alloy mini-prostheses with high-modulus of elasticity were implanted on the right side(control group)and those with low-modulus of elasticity on the left side(experiment group)to repair the cartilage defects.After 3 months,all the 8 dogs were sacrificed to harvest the specimens.Radiographic,histologic and micro-CT examinations were conducted to observe stability of the mini-prostheses and growth of the bone and cartilage surrounding the implants. Results Radiographic evaluation revealed no indications of device disassembly or subsidence.Bone trabeculae surrounding anchoring screws in the experiment group was visibly more and denser compared with the control group.Micro-CT data revealed that the bone volume fraction,trabecular thickness,trabecular number and tissue mineral density were 0.389%±0.025%,0.049±0.002 μm,8.9±0.4 mm-1 and 652.7 ±12.6 mg/mm3 respectively in the experiment group,compare with 0.253%±0.024%,0.038±0.002 μm,5.9±0.4 mm-1 and 595.2±7.6 mg/mm3 in the control group,with statistically significant differences between the 2 groups(P<0.05).Cartilage around the cap grew well and the surface remained smooth.Periphery of the resurfacing implant was covered by an extension of the superficial cartilage emanating from the defect margins. Conclusions The new β Ti alloy mini-prosthesis with low elastic modulus is favorable toward resurfacing the articular surface defect.The low-modulus of elasticity can improve new bone formation on the implant-bone interface.     

新型低弹性β钛合金关节表面微假体治疗犬膝关节软骨全层缺损的实验研究

目的 评价新犁低弹性β钛合金关节表面微假体治疗犬膝关节软骨面全层缺损的可行性与效果.方法 取8只成年家犬,制备舣侧股骨髁直径为7 mm的软骨面全层缺损,选用两种弹性模量钛合金材料制备关节表而微假体并植入软骨缺损区,左侧为低弹性模量组(弹性模量为42 GPa),右侧为高弹性模量组(弹性模量为110 GPa).3个月后取材,行X线片、显微CT扫描、骨计量学分析和组织学检测观察两组关节表面微假体的稳定性及周边骨与软骨的生长情况.结果 X线片示关节表面微假体钉帽周围软骨生长良好,完全填充钉帽周边软骨间隙,关节软骨面平整.显微CT三维重建及骨计量学分析显示低弹性模量组骨体积分数、骨小梁厚度、骨小梁数目及骨组织密度平均分别为0.389%±0.025%、(0.049±0.002)μm、(8.9±0.4)mm1、(652.7±12.6)mg/mm3,而高弹性模量组平均分别为0.253%±0.024%、(0.038 ±0.002)μm、(5.9±0.4)mm-1、(595.2±7.6)mg/mm3,以上指标两组间比较差异均有统计学意义(P<0.05).组织学观察显示低弹性模量组微关节表面假体固定钉周围有更多的新生骨小梁包绕,钉骨结合牢固,界面成骨量明显多于高弹性模量组.结论 新型低弹性β钛合金关节表面微假体治疗关节软骨面缺损是可行的,其低弹性模量的特点更有利干钉骨界面骨的形成.

Abstract：

Objective To assess the effect of a new β Ti alloy mini-prosthesis with low elastic modulus on resurfacing the full-thickness Surface defect of the knee joint in dogs.Methods A full-thickness osteochondral defect of 7 mm in diameter was created at the medial femoral condyle of both hind limbs in 8 healthy adult dogs.The titanium alloy mini-prostheses with high-modulus of elasticity were implanted on the right side(control group)and those with low-modulus of elasticity on the left side(experiment group)to repair the cartilage defects.After 3 months,all the 8 dogs were sacrificed to harvest the specimens.Radiographic,histologic and micro-CT examinations were conducted to observe stability of the mini-prostheses and growth of the bone and cartilage surrounding the implants. Results Radiographic evaluation revealed no indications of device disassembly or subsidence.Bone trabeculae surrounding anchoring screws in the experiment group was visibly more and denser compared with the control group.Micro-CT data revealed that the bone volume fraction,trabecular thickness,trabecular number and tissue mineral density were 0.389%±0.025%,0.049±0.002 μm,8.9±0.4 mm-1 and 652.7 ±12.6 mg/mm3 respectively in the experiment group,compare with 0.253%±0.024%,0.038±0.002 μm,5.9±0.4 mm-1 and 595.2±7.6 mg/mm3 in the control group,with statistically significant differences between the 2 groups(P<0.05).Cartilage around the cap grew well and the surface remained smooth.Periphery of the resurfacing implant was covered by an extension of the superficial cartilage emanating from the defect margins. Conclusions The new β Ti alloy mini-prosthesis with low elastic modulus is favorable toward resurfacing the articular surface defect.The low-modulus of elasticity can improve new bone formation on the implant-bone interface.