Department of Orthopaedic Surgery, Saint Louis University School of Medicine, St Louis, MO 63110, USA.
J Orthop Trauma. 2012 Jul;26(7):402-6. doi: 10.1097/BOT.0b013e31822c83bd.
Although locked plating has been shown to have advantages for diaphyseal and metaphyseal fracture fixation, its benefits for pubic symphyseal disruption have not been established. With traditional plate fixation of the disrupted pubic symphysis, normal physiological symphyseal pelvic motion eventually results in plate breakage, screw breakage, and loosening of screws. A concern exists that common modes of locked plate construct failure could result in abrupt and complete loss of symphyseal fixation. The purposes of this study were to determine, using an open-book pelvic injury model, whether locked plating of the pubic symphysis 1) offers any advantage over standard unlocked plating; and 2) results in a potential increased risk of abrupt fixation failure.
Twelve osteopenic cadaver pelvic specimens were acquired and dual-energy x-ray absorptiometry scans were obtained to ensure uniformity of the specimens' bone density. Sacrospinous, sacrotuberous, and anterior sacroiliac ligaments were released and the symphysis pubis was transected to simulate a partially stable open book (AO/Orthopaedic Trauma Association 61-B3.1) injury. Using a six-hole 3.5-mm plate specifically designed for the symphysis pubis with the capability of fixation in locked or unlocked mode, six pelvises were fixed with locked screws and six pelvises were fixed standard unlocked bicortical screws. There was no significant difference between these 2 groups with regard to bone density (P = 0.47). Two equally osteopenic pelvic specimens from each fixation group were selected for the purpose of obtaining failure data and determining an acceptable load for trialing. Both specimens failed at 1985 N. The remaining 10 pelvises were then mounted on a materials testing apparatus using the bilateral stance model as described by Tile. In accordance with the failure data, each pelvis was stressed at 440 N for a total of one million cycles (equivalent to 6.5 months of daily walking) or until fixation failure.
All pelvic specimens in both fixation groups completed one million cycles without plate or screw failure. However, diastasis of the initial pubic symphysis reduction was found in all pelvises (mean, 2.45 mm; range, 1.5-4.0 mm) regardless of fixation method. This loss of reduction was not significantly different between the 2 fixation groups (P = 0.914).
No abrupt failures occurred in either plating group. Consequently, any fear of catastrophic (ie, abrupt and complete) failure of locked symphyseal plates appears to be unfounded for open-book injuries treated in patients with low bone density. However, minor loss of the symphyseal reduction was evident in all pelvises regardless of the fixation method. Therefore, locked plating of the pubic symphysis does not appear to offer any advantage over the standard unlocked technique for an AO/Orthopaedic Trauma Association 61-B3.1 partially stable open-book pelvic injury pattern in osteopenic bone.
虽然锁定钢板已被证明在骨干和干骺端骨折固定方面具有优势，但在耻骨联合分离中的益处尚未确定。对于传统的耻骨联合切开复位钢板固定，正常的生理耻骨联合骨盆运动最终会导致钢板断裂、螺钉断裂和螺钉松动。人们担心常见的锁定钢板结构失效模式可能会导致耻骨联合固定突然完全丧失。本研究的目的是使用开放式骨盆损伤模型确定锁定钢板固定耻骨联合是否：1）优于标准非锁定钢板固定；2）增加突然固定失效的潜在风险。
获得 12 具骨质疏松性骨盆尸体标本，并进行双能 X 线吸收法扫描，以确保标本骨密度均匀。骶棘、骶结节和前骶髂韧带松解，耻骨联合切开，模拟部分不稳定开放式书（AO/矫形创伤协会 61-B3.1）损伤。使用专门设计用于耻骨联合的六孔 3.5mm 钢板，具有锁定或非锁定模式固定的能力，其中 6 具骨盆用锁定螺钉固定，6 具骨盆用标准非锁定双皮质螺钉固定。这两组之间的骨密度没有显著差异（P=0.47）。从每个固定组中各选择 2 个同样骨质疏松的骨盆标本，用于获取失效数据并确定试验的可接受载荷。两个标本均在 1985N 时失效。然后，将其余 10 个骨盆按照 Tile 描述的双侧站位模型安装在材料测试设备上。根据失效数据，每个骨盆在总共 100 万次循环（相当于每天行走 6.5 个月）或直至固定失效时，以 440N 的压力进行加载。
两组固定骨盆标本均完成了 100 万次循环，无钢板或螺钉失效。然而，无论固定方法如何，所有骨盆的耻骨联合初始复位间隙均有分离（平均 2.45mm；范围 1.5-4.0mm）。两组固定方法之间的这种复位丢失没有显著差异（P=0.914）。
两组钢板固定均未发生突然失效。因此，对于低骨密度患者的开放式书损伤，锁定耻骨联合钢板灾难性（即突然和完全）失效的任何担忧似乎都没有根据。然而，无论固定方法如何，所有骨盆的耻骨联合复位均有轻微丢失。因此，对于 AO/矫形创伤协会 61-B3.1 部分不稳定开放式书骨盆损伤模式的骨质疏松性骨，锁定耻骨联合钢板固定似乎并不优于标准非锁定技术。
