Kusunose K
Nihon Seikeigeka Gakkai Zasshi. 1982 May;56(5):399-414.
It is a well known fact that rigid and prolonged internal fixation of a fracture with a stiff plate yields osteoporosis. In order to solve this problem, so called "less rigid" plates made of various plastic materials have been tested by some workers experimentally, but they are not widely accepted yet for clinical use, for the plastic material used lacked sufficient strength to secure stable osteosynthesis. This paper presents a series of experimental studies using polyacetal (polyoxymethylene--POM) materials which have relatively larger strength, for the fixation of canine fractures.
Experiment I--Alteration of material strength in vivo: Dumb-bell shaped test pieces were made of three different POM plastics; 1, acetal copolymer alone (M90), 2, acetal copolymer reinforced with 20% carbon fiber (CR20) and 3. acetal copolymer with 20% fluorine (YF20). Tensile strength was measured after imbedding the test piece between the vastus lateralis and the biceps femoris of dogs for eight months. The results were compared with those before imbedding. Experiment II--Fracture healing study: After applying a POM plate or a stainless-steel plate (AO one-third tubular plate) on an adult canine femur with four stainless-stell screws, the femur was osteotomized at the center with a Gigli saw to produce a transverse fracture. Postoperative roentgenograms were taken periodically. After sufficient bone union on roentgenogram, the animal was sacrificed to excise the femur for three point bending test applying up to 30 kg load posteriorly to the femur to measure ultimate strength, deflexion at the center and strains at the anterior portion of the bone.
Experiment I: A certain decrease in tensile strength was noted in the three tested materials. Experiment II: 1) With M90 plates, there was considerable tendency toward delayed union, which would have been due to insufficient strength of the plate. 2) No significant difference in the period required for bone union was noted between the CR20 and the AO plate groups, while the former tended to produce larger callus. 3) The ultimate strength of the united bone following CR20 of AO plate fixation ranged from 50 to 55% of that of the contralateral non-osteotomized femur. There was no significant difference between the two plate groups. 4) The deflexion at the center was significantly less in the CR20 group under low load, irrespective to the difference in the amount of the ultimate strength. 5) The strain at the fracture site was extremely large in the AOI group compared to those at the other sites, which would indicate uneven strength distribution, while the strains were relatively even in the CR20 group as in the non-osteotomized femur. The results of the experiments suggest possibilities of using reinforced polyacetal plates for better fracture fixation.
众所周知，使用坚固钢板对骨折进行刚性且长时间的内固定会导致骨质疏松。为了解决这个问题，一些研究人员对由各种塑料材料制成的所谓“低刚性”钢板进行了实验测试，但它们尚未被广泛应用于临床，因为所使用的塑料材料缺乏足够的强度来确保稳定的骨接合。本文介绍了一系列使用具有相对较大强度的聚缩醛（聚甲醛——POM）材料固定犬类骨折的实验研究。
实验一——体内材料强度的变化：哑铃形试件由三种不同的POM塑料制成；1，仅乙缩醛共聚物（M90）；2，用20%碳纤维增强的乙缩醛共聚物（CR20）；3，含20%氟的乙缩醛共聚物（YF20）。将试件埋入狗的股外侧肌和股二头肌之间八个月后测量拉伸强度。结果与埋入前进行比较。实验二——骨折愈合研究：在成年犬股骨上用四颗不锈钢螺钉固定一块POM板或一块不锈钢板（AO三分之一管状板）后，用线锯在股骨中心进行截骨以造成横行骨折。定期拍摄术后X线片。X线片显示骨充分愈合后，处死动物以取出股骨进行三点弯曲试验，向后对股骨施加高达30千克的载荷以测量极限强度、中心挠度和骨前部的应变。
实验一：在三种测试材料中均观察到拉伸强度有一定程度的降低。实验二：1）使用M90板时，有明显的延迟愈合倾向，这可能是由于板的强度不足。2）CR20组和AO板组在骨愈合所需时间上无显著差异，而前者往往产生更大的骨痂。3）CR20或AO板固定后愈合骨的极限强度为对侧未截骨股骨的50%至55%。两组之间无显著差异。4）在低载荷下，CR20组的中心挠度明显较小，与极限强度的差异无关。5）与其他部位相比，AOI组骨折部位的应变极大，这表明强度分布不均匀，而CR20组的应变与未截骨股骨一样相对均匀。实验结果表明使用增强聚缩醛板进行更好的骨折固定具有可能性。
