Jarrell Shelby E, Owen John R, Wayne Jennifer S, Adelaar Robert S
Virginia Commonwealth University, Richmond, VA 23298, USA.
Foot Ankle Int. 2009 Feb;30(2):150-6. doi: 10.3113/FAI-2009-0150.
Talonavicular fusion is performed for a variety of indications. This study examined the effects of fixation techniques on plantar pressures, construct stiffness, and strength.
Eight matched pairs of cadaveric lower extremities were axially loaded intact and after talonavicular fixation with a 3.5 reconstruction plate, reconstruction plate plus cancellous screw (plate/screw), or three screws (screws). Recorded plantar pressures were divided into three forefoot, two midfoot, and two hindfoot regions. Cantilevered bending of excised constructs provided stiffness data for plantar and lateral directions, and failure characteristics in plantar bending.
Relative to the intact state, all fixations decreased peak pressure in the medial forefoot, while generally increasing it in the lateral forefoot and midfoot. Average pressure shifted laterally for all fixation methods in the forefoot, generally in the hindfoot and the lateral midfoot. Generally, contact areas decreased in the medial forefoot, midfoot, and hindfoot while increasing laterally in the midfoot and hindfoot. The only difference among fixation methods was a decreased medial midfoot contact area for screws. No differences were found between screws and plate/screw in bending stiffness or failure (p < 0.5 and p < 0.2 respectively). Plantar and lateral bending stiffness for the plate/screw method averaged approximately 363 N/mm while stiffness of the screw only construct averaged approximately 380 N/mm. The load to failure averaged 946 N for the plate/screw construct and 1099 N for the screw construct.
This study showed lateralization of plantar pressures following talonavicular fixation. Minimal differences were found between plate/screw and screws. Fixation across the joint may be key to achieving stability sufficient to resist shear and rotational stresses.
Plate/screw or screws would likely be similarly effective in fusing the talonavicular joint. However, the fusion induced lateralization of plantar pressures may unintentionally result in adjacent joint arthritis and foot pain.
距舟融合术适用于多种适应症。本研究探讨了固定技术对足底压力、结构刚度和强度的影响。
八对匹配的尸体下肢在完整状态下以及在距舟关节用3.5重建钢板、重建钢板加松质骨螺钉（钢板/螺钉）或三枚螺钉（螺钉）固定后进行轴向加载。记录的足底压力分为三个前足区域、两个中足区域和两个后足区域。切除结构的悬臂弯曲提供了足底和外侧方向的刚度数据以及足底弯曲的失效特征。
相对于完整状态，所有固定方式均降低了前足内侧的峰值压力，而前足外侧和中足的峰值压力通常增加。所有固定方法在前足的平均压力均向外侧偏移，后足和中足外侧通常也是如此。一般来说，前足内侧、中足和后足的接触面积减小，而中足和后足的外侧接触面积增加。固定方法之间的唯一差异是螺钉固定时中足内侧接触面积减小。螺钉和钢板/螺钉在弯曲刚度或失效方面无差异（分别为p<0.5和p<0.2）。钢板/螺钉方法的足底和外侧弯曲刚度平均约为363N/mm，而仅用螺钉固定的结构刚度平均约为380N/mm。钢板/螺钉结构的破坏载荷平均为946N，螺钉结构为1099N。
本研究表明距舟关节固定后足底压力向外侧偏移。钢板/螺钉和螺钉之间差异极小。跨关节固定可能是实现足以抵抗剪切和旋转应力的稳定性的关键。
钢板/螺钉或螺钉在距舟关节融合中可能同样有效。然而，融合引起的足底压力向外侧偏移可能无意中导致相邻关节关节炎和足部疼痛。
