McLachlin Stewart, Kreder Hans, Ng Matthew, Jenkinson Richard, Whyne Cari, Larouche Jeremie
Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, Toronto, ON, Canada.
Division of Orthopaedic Surgery, University of Toronto, Toronto, ON, Canada.
J Orthop Trauma. 2017 Dec;31(12):e418-e424. doi: 10.1097/BOT.0000000000000956.
Assess the effect of proximal screw configuration on the strain in lateral plating of a simulated comminuted supracondylar femur fracture.
Fractures were simulated in 12 synthetic femurs by removing a 200-mm section of bone, located 60 mm from the intercondylar fossa and repaired using a 16-hole locked lateral plate instrumented with 8 uniaxial strain gauges. Three proximal screw type configurations were evaluated: (1) 4 nonlocking screws, (2) 4 locking screws, and (3) a hybrid configuration of 2 nonlocking screws flanked by a locking screw at each end of the proximal fragment. Each screw type was compared for 2 working lengths (∼90 and 160 mm). The longer working length was created by removing the proximal screw closest to the fracture gap. Testing consisted of a vertical load (500 N) applied to the head of femur. Configurations were compared using plate strain, construct stiffness, and fracture gap displacement as outcome measures.
Plate strain immediately above the fracture gap was reduced with nonlocking screws compared with the other screw types. Plate strains were reduced around the fracture gap with the longer working length but increased for the nonlocking construct at the location of the removed screw. Construct stiffness was not altered by screw type or working length. An increase in fracture gap displacement was only evident in shear translation with the longer working length.
Plate strain in lateral plating of supracondylar femur fractures is decreased using nonlocking screws proximal to the fracture. Increasing the working length reduces plate strains over the working length yet should be cautioned because of increased interfragmentary shear motion.
评估近端螺钉配置对模拟股骨髁上粉碎性骨折外侧钢板应变的影响。
通过去除距髁间窝60mm处的200mm骨段，在12根合成股骨上模拟骨折，并用一个装有8个单轴应变片的16孔锁定外侧钢板进行修复。评估了三种近端螺钉类型配置：（1）4枚非锁定螺钉，（2）4枚锁定螺钉，以及（3）近端骨折块两端各有一枚锁定螺钉、中间夹2枚非锁定螺钉的混合配置。每种螺钉类型在2种工作长度（约90mm和160mm）下进行比较。较长的工作长度是通过移除最靠近骨折间隙的近端螺钉来实现的。测试包括向股骨头施加垂直载荷（500N）。以钢板应变、结构刚度和骨折间隙位移作为结果指标对各种配置进行比较。
与其他螺钉类型相比，非锁定螺钉可降低骨折间隙正上方的钢板应变。较长工作长度时，骨折间隙周围的钢板应变降低，但在移除螺钉位置的非锁定结构中钢板应变增加。螺钉类型或工作长度未改变结构刚度。仅在较长工作长度的剪切平移中，骨折间隙位移增加明显。
在股骨髁上骨折的外侧钢板固定中，骨折近端使用非锁定螺钉可降低钢板应变。增加工作长度可降低工作长度上的钢板应变，但由于骨折块间剪切运动增加，应谨慎使用。
