Leitch B J, Worth A J
a Massey University Veterinary Teaching Hospital, Institute of Veterinary, Animal and Biomedical Sciences, Massey University , Private Bag 11 222, Palmerston North 4442, New Zealand.
b Current address: Veterinary Surgical Referrals Ltd , 49b Coopers Road, Gate Pa, Tauranga 3112, New Zealand.
N Z Vet J. 2018 May;66(3):144-153. doi: 10.1080/00480169.2018.1443406. Epub 2018 Mar 8.
To provide veterinarians with confidence when using a commercially available epoxy resin in external skeletal fixators (ESF), testing was conducted to determine exothermia during curing of the epoxy resin compared to polymethylmethacrylate (PMMA), the hardness of the epoxy resin as a bar over 16 weeks, and the strength of the epoxy resin bar compared with metal clamps in similarly constructed Type 1a ESF constructs simulating the repair of feline long bone fractures.
Exothermia of the epoxy resin during curing was tested against PMMA with surface temperatures recorded over the first 15 minutes of curing, using four samples of each product. The hardness of 90 identical epoxy resin bars was tested by subjecting them to cyclic loads (1,000 cycles of 20.5 N, every 7 days) over a 16-week period and impact testing 10 bars every 2 weeks. Ten bars that were not subjected to cyclic loads were impact tested at 0 weeks and another 10 at 16 weeks. Strength of the epoxy resin product, as a bar and clamp composite, was tested against metal SK and Kirschner-Ehmer (KE) clamps and bars in Type 1a, tied-in intramedullary pin, ESF constructs with either 90° or 75° pin placement, subjected to compressive and bending loads to 75 N.
The maximum temperature during curing of the epoxy resin (min 39.8, max 43.0)°C was less than the PMMA (min 85.2, max 98.5)°C (p<0.001). There was no change in hardness of the epoxy resin bars over the 16 weeks of cyclic loading (p=0.58). There were no differences between the median strength of the epoxy resin, SK or KE ESF constructs in compression or bending when tested to 75 N (p>0.05). Stiffness of constructs with 75° pin placement was greater for SK than epoxy resin constructs in compression (p=0.046), and was greater for KE than epoxy resin constructs in bending (p=0.033).
The epoxy resin tested was found to be less exothermic than PMMA; bars made from the epoxy resin showed durability over an expected fracture healing timeframe and had mechanical strength characteristics comparable to metal bar and clamp ESF constructs.
The epoxy resin ESF construct tested in this study can be considered a suitable replacement for SK or KE ESF constructs in the treatment of feline long-bone fractures, in terms of mechanical strength.
为兽医在使用市售环氧树脂进行外骨骼固定器（ESF）操作时提供信心，进行了相关测试，以确定环氧树脂固化过程中的放热情况，并与聚甲基丙烯酸甲酯（PMMA）进行比较，研究环氧树脂棒在16周内的硬度，以及在模拟猫长骨骨折修复的1a型ESF结构中，将环氧树脂棒与金属夹的强度进行比较。
通过记录每种产品四个样品在固化的前15分钟内的表面温度，测试环氧树脂固化过程中的放热情况，并与PMMA进行对比。对90根相同的环氧树脂棒进行硬度测试，在16周内对其施加循环载荷（每7天20.5 N的1000次循环），并每2周对10根棒进行冲击测试。对10根未施加循环载荷的棒在0周时进行冲击测试，另外10根在16周时进行冲击测试。将环氧树脂产品作为棒和夹的复合材料，与金属SK和克氏针-埃默尔（KE）夹以及棒在1a型、髓内针固定、ESF结构中进行强度测试，针的放置角度为90°或75°，施加75 N的压缩和弯曲载荷。
环氧树脂固化过程中的最高温度（最低39.8，最高43.0）°C低于PMMA（最低85.2，最高98.5）°C（p<0.001）。在16周的循环加载过程中，环氧树脂棒的硬度没有变化（p=0.58）。当测试到75 N时，环氧树脂、SK或KE ESF结构在压缩或弯曲方面的中位强度没有差异（p>0.05）。在压缩时，75°针放置的SK结构的刚度比环氧树脂结构更大（p=0.046），在弯曲时，KE结构的刚度比环氧树脂结构更大（p=0.033）。
测试发现环氧树脂的放热比PMMA少；由环氧树脂制成的棒在预期的骨折愈合时间范围内显示出耐久性，并且具有与金属棒和夹ESF结构相当的机械强度特性。
就机械强度而言，本研究中测试的环氧树脂ESF结构可被视为治疗猫长骨骨折时SK或KE ESF结构的合适替代品。
