Objective To explore the effect on the fracture union in Tibet mini-pigs of a novel micro-controlled dynamic intramedullary nail which was self-designed on the basis of anatomic parameters of the animal tibia.Methods We measured the length,arc and inner diameters of the starting,narrowest and ending points of the bilateral tibial medullary cavities on the X-ray films of 20 Tibet mini-pigs.We designed and manufactured a new micro-controlled intramedullary nail using UG software on the basis of the anatomic measurements and CT 3D reconstructions of the animal tibia.The new fixation nails were tested in the animal models of left tibial middle fracture in 10 Tibet mini-pigs which were randomized into 2 groups (n =5).The experiment group was treated with the novel micro-controlled dynamic intramedullary nail and the control group with the static interlocking intramedullary nail.The fracture union was evaluated and compared between the 2 groups by X-ray,gait analysis and micro CT.Results Of the medullary cavity,the triangle proximal end was expansive,the middle segment was narrow and the oval distal end was also expansive in the Tibet mini-pigs.The length of medullary cavity averaged 113.31 ± 9.56 mm and the cavity arc 25.66° ± 3.37°.The nail length was 90 to 130 mm,the nail diameter 6 to 9 mm,the arc 15° to 25°,and the diameter of both locked screw and bioresorbable material 4.0 mm.The micro CT showed that the experimental group had significantly higher volume bone density (555.47 ± 23.49 mg/mm3) and bone volume fraction (0.84 + 0.04) than the control group (494.45 ± 16.62 mg/mm3 and 0.78 ± 0.03 respectively) (P ＜ 0.05).Conclusion It may help fracture union to design a novel micro-controlled dynamic intramedullary nail based on the theory of micro-controlled motion in clinic research.%目的 通过CT三维重建测量西藏小型猪的胫骨解剖参数,设计一种新型可控微动胫骨髓内钉,并探讨其对骨折愈合的影响. 方法 选取20只成年西藏小型猪双后肢(40侧),通过X线片测量双侧胫骨髓腔长度、弧度、髓腔起点、最狭窄点及止点内径;以测得的解剖参数及CT三维重建数据为标准,通过UG软件设计出胫骨可控微动髓内钉.选取10只西藏小型猪为实验对象,均予以左侧胫骨中段骨折造模,随机分为2组(n=5):实验组(以新型可控微动胫骨髓内钉固定)和对照组(用静力型交锁钉固定).通过术后X线片、步态分析及显微CT结果全面评估两组小型猪的骨折愈合情况. 结果 小型猪胫骨髓腔近段膨大,呈三角形;中段狭窄,为过渡形态;远段膨大,呈椭圆形.髓腔全长平均为(113.31 ±9.56) mm,髓腔弧度平均为25.66°±3.37°.相应髓内钉参考规格:长度为90 ～ 130 mm、直径为6～9 mm、折弯角为15°～25°、锁钉直径与可吸收材料直径均为4 mm.显微CT显示实验组骨折愈合处体积骨密度[(555.47±23.49) mg/mm3]、骨体积分数(0.84+0.04)均高于对照组[(494.45±16.62)mg/mm3、0.78 ±0.03],差异均有统计学意义(P＜0.05). 结论 将可控微动的理念应用于胫骨髓内钉的设计中有利于骨折愈合.
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