顺行髓内针内固定术治疗掌骨骨折的生物力学研究

目的 研究单根顺行髓内针内固定术治疗掌骨骨折的生物力学性能.方法 2008年3月至5月取25侧成人前臂标本的第2～5掌骨共100根,分为第2、3掌骨(n=50)及第4、5掌骨(n=50)并横行截骨,分别随机使用钢板螺钉、顺行髓内针、交叉克氏针行骨折内固定,之后对第4、5掌骨行三点折弯试验,对第2、3掌骨行扭转应力试验.结果 三点折弯试验中,顺行髓内针的最大折弯力矩(1.49 N·m)及抗弯刚度(0.047 N·m~2)均与钢板螺钉的(分别为1.47 N·m与0.056 N·m~2)无明显差异,并且均显著大于交叉克氏针(分别为0.44 N·m与0.025 N·m~2).在扭转应力试验中,顺行髓内针的最大扭矩(0.36 N·m)明显小于钢板螺钉的(0.89 N·m),而与交叉克氏针(0.55 N·m)无显著差异;顺行髓内针的扭转刚度(0.035 N·m~2/rad)明显小于钢板螺钉(0.087 N·m~2/rad)及交叉克氏针(0.065 N·m~2/rad)的扭转刚度.结论 单根顺行髓内针内固定有较好的抗弯性能,抗旋转性能相对较差,临床应用时要注意保护.

Biomechanical research of antegrade intramedullary fixation for the metacarpal fractures

Objective To study the biomechanieal characteristics of antegrade intramedullary fixation for metacarpal fractures.Methods From March to May 2008,both the 4th and 5th metacarpals from 25 formalin embalmed cadaver hands had three-point bending test after transverse osteotomy followed by randomly fixation with one of the following three methods:plate and screw,antegrade intramedullary K-wire,crossed K-wire.While,both the 2nd and 3rd metacarpals had torsional loading test after the same management as the 4th and 5th metacarpal had undergone.Results In the three-point bending test,both the maximum bending moment(M_(max))and bending rigidity(EI)of the antegrade intramedullary K-wire were comparable with those of the plate and screw,and were significantly larger than those of the crossed K-wire.In the torsional loading test,the antegrade intramedullary K-wire had a statistically smaller maximum torque (T_(max))than the plate and screw,and had a comparable Tmax with the crossed K-wire;while,the torsional rigidity(GJ)of the intramedullary K-wire was statistically weaker than that of both the plate and screw and the crossed wire.Conclusions One single antegrade intramedullary K-wire can provide a satisfactory M_(max) and EI for metacarpal fixation and shows relatively weak in the torsional loading test.The injured finger should be well protected to avoid torsional deformity in clinical practice.