Chen Jiawen, Wang Zhonghe, Li Changda, He Peiyu, Chen Zhongxuan, Sun Lijun, Cao Xiaoyan, Tian Na, Dong Xiang, Tang Peifu, Chen Hua
Chinese PLA Medical School, Beijing, China.
The Department of Orthopaedic Surgery, Fourth Medical Center for Chinese PLA General Hospital, Beijing, China.
Orthop Surg. 2025 Feb;17(2):551-562. doi: 10.1111/os.14297. Epub 2024 Nov 27.
Intramedullary nailing is preferred for treating elderly proximal humeral fractures, but secondary reductions are common, particularly in elderly and osteoporotic patients. This occurs due to the intramedullary nail fixation's insufficient anti-varus and anti-rotational capacities and high stress at the bone-implant interface. We aim to enhance the anti-varus and anti-rotational stability of the fixation structure while reducing the stresses on the bone and internal fixation through structural design.
We developed a novel endosteal anatomical support nail (EASN) that integrates an endosteal torus construct into the proximal portion of the angle-stable proximal humerus nail. The endosteal torus construct includes endosteal anatomical support (EAS) with a flat plane that allows direct fixation of the humeral head fragments and is shaped to conform to the medial side of the medullary cavity of the proximal humerus. We conducted finite element analysis to assess the biomechanical stability of four constructs: EAS with a calcar screw (CS), EAS without CS, non-EAS with CS, and non-EAS without CS. This analysis determined the contribution of the EAS to the mechanical stability of the proximal humerus in two-part PHF with medial column disruption. Specimens were subjected to loads simulating partial-weight-bearing (as in rising from a chair or using crutches) and full-weight-bearing (as in rising from bed). We evaluated the stiffness of the construct, displacement at the fracture site, von Mises stress, and stress distribution.
Under compressive or rotational loads, the EAS construct, with or without CS, was significantly stiffer than the non-EAS construct. Displacement at the fracture site was significantly less with the EAS fixation than with the non-EAS fixation. However, the stiffness and displacement at the fracture site of the EAS fixation without CS were comparable to those of the non-EAS construct with CS. The EAS construct reduced the load on the nail and decreased the risk of implant failure. Both von Mises stress and stress distribution were significantly lower following fixation with the EAS constructs.
This study introduces a novel EAS concept to enhance the anti-varus and anti-rotational capabilities of the humeral head and distribute stress at the bone-implant interface in treating elderly PHFs. This strategy shows promise based on our limited analysis.
髓内钉固定术是治疗老年肱骨近端骨折的首选方法，但二次复位很常见，尤其是在老年和骨质疏松患者中。这是由于髓内钉固定的抗内翻和抗旋转能力不足以及骨-植入物界面处的高应力所致。我们旨在通过结构设计提高固定结构的抗内翻和抗旋转稳定性，同时减少骨骼和内固定物上的应力。
我们开发了一种新型的骨内膜解剖支撑钉（EASN），它将骨内膜环形结构整合到角稳定型肱骨近端髓内钉的近端部分。骨内膜环形结构包括骨内膜解剖支撑（EAS），其具有一个平面，可直接固定肱骨头碎片，并且其形状与肱骨近端髓腔的内侧相契合。我们进行了有限元分析，以评估四种结构的生物力学稳定性：带距螺钉（CS）的EAS、不带CS的EAS、带CS的非EAS和不带CS的非EAS。该分析确定了EAS对伴有内侧柱破坏的二部分型肱骨近端骨折（PHF）中肱骨近端机械稳定性的贡献。对标本施加模拟部分负重（如从椅子上起身或使用拐杖时）和完全负重（如从床上起身时）的负荷。我们评估了结构的刚度、骨折部位的位移、von Mises应力和应力分布。
在压缩或旋转负荷下，带或不带CS的EAS结构比非EAS结构明显更硬。EAS固定时骨折部位的位移明显小于非EAS固定时。然而，不带CS的EAS固定在骨折部位的刚度和位移与带CS的非EAS结构相当。EAS结构减轻了钉子上的负荷，降低了植入物失败的风险。用EAS结构固定后，von Mises应力和应力分布均显著降低。
本研究引入了一种新型的EAS概念，以增强肱骨头的抗内翻和抗旋转能力，并在治疗老年PHF时在骨-植入物界面处分散应力。基于我们有限的分析，这一策略显示出前景。
