Shetty V, Freymiller E, McBrearty D, Caputo A A
UCLA School of Dentistry 90094-1668, USA.
J Oral Maxillofac Surg. 1996 Nov;54(11):1317-24; discussion 1324-6. doi: 10.1016/s0278-2391(96)90490-5.
This study determined the relative functional stabilities of various miniplate systems and configurations used to stabilize sagittal split ramus osteotomies (SSROs) and compared them with conventional internal screw fixation.
The biomechanical model was a reproducible prototype of a mandible sagittal osteotomy with consistent material and geometric properties. After advancing the distal segment by 7 mm, each set of mandible analogs (1 set = 3 analogs) was fixed bilaterally by one of three miniplate systems applied in various configurations, and tested with and without a supplemental 2.4-mm bicortical screw applied in the retromolar region. Reduced analogs were placed in a straining frame, and simulated masticatory loads were applied alternatively to the mandibular first molars. Ensuing osteotomy site displacements were measured by transducers attached to a computer-based data acquisition program. A coordinate transformation procedure was used to convert the component displacements captured by the individual transducers into a common "instability factor" to reflect fixation stability for each construct and loading condition. Instability factors for the individual constructs were compared with each other and with those obtained from analogs reduced exclusively with 2.4-mm position screws.
Osteotomies stabilized with a combination of miniplates and position screws were more stable than those stabilized exclusively with miniplates (P < .0001). Post-hoc comparisons of mean instability factors (Dunnet's method) showed the miniplate-position screw combinations to be more stable than the 2.4-mm position screw system used as standard (P < .05). Miniplate systems alone were the least stable of the test constructs, with differential rates of failure between the individual miniplate systems.
Exclusive use of miniplate fixation may not provide the consistent stability necessary for early functional restoration after SSROs. The addition of a position screw in the retromolar region substantially enhances the fixation stability of miniplate systems. The use of miniplates with retromolar position screws offers both technical and stability advantages over conventional miniplate or internal screw fixation. The fixation stability of the miniplate-position screw combination is independent of the type of miniplate system used.
本研究确定了用于稳定下颌支矢状劈开截骨术（SSROs）的各种微型钢板系统及其构型的相对功能稳定性，并将其与传统的内固定螺钉固定进行比较。
生物力学模型是具有一致材料和几何特性的下颌矢状截骨术的可重复原型。将远心骨段前移7mm后，每组下颌骨模拟物（1组 = 3个模拟物）通过三种微型钢板系统之一以各种构型进行双侧固定，并在磨牙后区应用或不应用补充的2.4mm双皮质螺钉的情况下进行测试。将缩小的模拟物置于应变框架中，并交替向下颌第一磨牙施加模拟咀嚼负荷。通过连接到基于计算机的数据采集程序的传感器测量随后的截骨部位位移。使用坐标变换程序将各个传感器捕获的分量位移转换为共同的“不稳定因子”，以反映每种结构和加载条件下的固定稳定性。将各个结构的不稳定因子相互比较，并与仅用2.4mm定位螺钉复位的模拟物所获得的不稳定因子进行比较。
用微型钢板和定位螺钉联合固定的截骨术比仅用微型钢板固定的截骨术更稳定（P < .0001）。平均不稳定因子的事后比较（Dunnet法）显示，微型钢板 - 定位螺钉组合比用作标准的2.4mm定位螺钉系统更稳定（P < .05）。单独的微型钢板系统是测试结构中最不稳定的，各个微型钢板系统之间的失败率存在差异。
单纯使用微型钢板固定可能无法为SSROs术后早期功能恢复提供所需的一致稳定性。在磨牙后区添加定位螺钉可显著提高微型钢板系统的固定稳定性。与传统的微型钢板或内固定螺钉固定相比，使用带有磨牙后定位螺钉的微型钢板具有技术和稳定性优势。微型钢板 - 定位螺钉组合的固定稳定性与所使用的微型钢板系统类型无关。
