Department of Orthopedic, Baoding No.1 Central Hospital, Baoding, 071000, Hebei Province, China.
Baoding Digital Orthopaedic Key Laboratory, Baoding, 071000, Hebei Province, China.
BMC Musculoskelet Disord. 2022 Dec 1;23(1):1045. doi: 10.1186/s12891-022-06016-y.
The spatial position of internal fixation play a role in determining the stability of internal fixations, both in clinical practice and research. Researchers have examined the stability of FNS (Femoral neck system) in the presence of coronal plane changes. In our knowledge, due to the biomechanical limitations of the specimens, there are no mechanical studies on the sagittal variation of FNS. This study aimed to investigate the biomechanical behavior of sagittal variations on Pauwels type III femoral neck fractures treated with FNS through finite element analysis.
Finite element models including Pauwels type III femoral neck fracture and FNS were reconstructed. Five fracture models(superior, central, inferior, anterior, posterior) were created in accordance with the bolt location in the sagittal plane within the femoral head. Equivalent stress, shear stress, and total deformation of each model under the same physiological load were recorded.
According to the results, the central model exhibited the slightest stress and displacement, with the exception of the superior model. The internal fixation stress of the superior model was smaller than that of the central model. However, the maximum interfragmentary stress, total deformation and shear resistance area of the superior model was larger than that of the central model.
Central position of FNS in the sagittal plane allowed axial compression while reducing shear stress of internal fixation and interfragmentary equivalent stress. Off-axis fixation of the femoral neck increased the strain area and total displacement of the bone, raising the risk of fixation failure. Therefore, the central placement of FNS may be a better surgical target in the treatment of femoral neck fractures.
内固定的空间位置在临床实践和研究中都对内固定的稳定性起着重要作用。研究人员已经研究了冠状面改变时 FNS（股骨颈系统）的稳定性。据我们所知，由于标本的生物力学限制，目前还没有关于 FNS 矢状变化的力学研究。本研究旨在通过有限元分析研究 Pauwels Ⅲ型股骨颈骨折采用 FNS 治疗时矢状变化的生物力学行为。
重建了包括 Pauwels Ⅲ型股骨颈骨折和 FNS 的有限元模型。根据股骨头内螺钉在矢状面上的位置，创建了 5 种骨折模型（上、中、下、前、后）。记录了每个模型在相同生理负荷下的等效应力、剪切应力和总变形。
根据结果，除了上模型之外，中央模型表现出最小的应力和位移。上模型的内固定应力小于中央模型。然而，上模型的最大骨折间等效应力、总变形和抗剪切面积大于中央模型。
FNS 在矢状面的中央位置允许轴向压缩，同时减少内固定和骨折间等效应力的剪切应力。股骨颈的偏心固定增加了骨的应变区域和总位移，增加了固定失败的风险。因此，FNS 的中央放置可能是股骨颈骨折治疗的更好的手术目标。
