Objective: To observe the biomechanical characteristics of bridge-link type combined internal fixation system (BCFS) with mixed-rod in the treatment of long segmental comminuted fracture of femoral shaft. Methods: A total of 16 models of long comminuted segment fracture of femoral shaft with mixed-rod and double-rod were made (8 each structure), and divided into the mixed-rod group and the double-rod group. The axial compression experiment and the radial torsion experiment were carried out on each of the mixed rod group and the double rod group. Four models were randomly selected from the two groups for axial compression experiment and radial torsion experiment, respectively. The changes of axial compression yield load and displacement, and also radial torsional yield load and angle were observed in two groups. At the same time, the maximum load was recorded when the curve had a break point or in a horizontal state, and then calculated the yield load. The data of normal distribution were compared with one-sample t test. Results: When the two groups were compressed axially at the same speed, as the axial compression yield load increased gradually, the longitudinal compression displacement of the mixed-rod group was obviously smaller than that in the double-rod group; and the maximum axial compression yield load of the mixed-rod group was greater than that in the double-rod group ((7 517±4)N vs (2 290±4) N, t=1 848.071, P=0.000). When the two groups were twisted radially at the same speed,as radial torsional yield load increased gradually, the radial torsion angle of the mixed-rod group was smaller than that in the double-rod group; and the maximum radial torsional yield load of the mixed-rod group was greater than that in the double-rod group ((61.3±2.0) Nm vs (24.4±2.2)Nm, t=25.201, P=0.000). Conclusions: For the long segment comminuted fracture of femoral shaft, the mixed-rod of BCFS can fix fracture more strongly than double-rod in longitudinal direction and maintain the stability of fracture end. The transverse torsion resistance is better than that of the double-rod, and the fatigue resistance is strong.
目的： 观察桥接组合式内固定系统（BCFS）混棒结构治疗股骨干长节段粉粹性骨折的生物力学特点。 方法： 制作相同人体股骨干长节段粉碎性骨折混棒结构及双棒结构模型各8根，共16根，并随机分为混棒组和双棒组。混棒组与双棒组各随机选取4根分别行轴向压缩实验及径向扭转实验。观察两组的轴向压缩屈服载荷与位移情况，以及径向扭转屈服载荷与角度变化；同时记录各组曲线开始出现折点，或趋于水平状态时的屈服载荷即最大屈服载荷。正态分布数据比较采用两独立样本设计t检验。 结果： 当两组以相同速度轴向压缩时，随着轴向压缩屈服载荷逐渐增大，混棒组纵向压缩位移明显小于双棒组，并且混棒组最大轴向压缩屈服载荷大于双棒组，差异有统计学意义[（7 517±4）N比（2 290±4）N，t=1 848.071，P=0.000]。当两组以相同速度径向扭转时，随着径向扭转屈服载荷逐渐增大，混棒组径向扭转角度小于双棒组，并且混棒组最大径向扭转屈服载荷大于双棒组，差异有统计学意义[（61.3±2.0）N·m比（24.4±2.2）N·m，t=25.201，P=0.000]。 结论： 对于股骨干长节段粉粹性骨折，桥接系统混棒结构主要在纵向上比双棒结构更能坚强固定骨折，维持骨折端的稳定性；而横向上抗扭转力也优于双棒结构，并且抗疲劳性能强。.

BACKGROUND: The standard treatment for Kummell disease with neurologic deficit remains controversial. Traditional posterior long-segment fixation (LSF) has been widely used, but the procedure results in significant trauma and carries the risk of multiple complications. Therefore, bone cement-augmented short-segment fixation (BCASSF) has been recommended for this condition.
METHODS: The study included 36 patients treated with LSF or BCASSF between January 2012 and June 2015. The visual analog scale (VAS), Oswestry Disability Index (ODI) score, anterior height of fractured vertebrae, kyphotic Cobb angle, and neurologic function by the Frankel classification were evaluated and compared, and duration of operation, blood loss, length of hospital stay, and complications were recorded.
RESULTS: Significant differences were observed in the VAS, ODI, anterior height of affected vertebrae, and kyphotic Cobb angle between preoperatively and 7 days postoperatively and between preoperatively and at the final follow-up, whereas no significant differences were observed between 7 days postoperatively and at final follow-up. No significant differences in the aforementioned parameters were observed between the groups at 7 days postoperatively and at the final follow-up. Neurologic function was improved in both groups; however, no significant differences were observed between the 2 groups either preoperatively or postoperatively. Blood loss and length of hospital stay were significantly lower in the BCASSF group compared with the LSF group, but no significant between-group differences were observed in operation time and complications.
CONCLUSIONS: Lower blood loss and shorter hospital stay were associated with BCASSF compared with LSF; the 2 techniques had similar clinical outcomes and radiographic findings. Therefore, we recommend BCASSF for treating patients with Kummell disease with neurologic deficits.