Chinese Journal of Tissue Engineering Research ›› 2021, Vol. 25 ›› Issue (6): 831-836.doi: 10.3969/j.issn.2095-4344.2383

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Relationship between tip-apex distance and stability of intertrochanteric femoral fractures with proximal femoral anti-rotation nail: a finite element analysis

Cai Qunbin1, Zou Xia2, Hu Jiantao2, Chen Xinmin3, Zheng Liqin3, Huang Peizhen1, Lin Ziling1, Jiang Ziwei1   

  1. 1First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, Guangdong Province, China; 2Fengcheng Hospital of Traditional Chinese Medicine, Fengcheng 331100, Jiangxi Province, China; 3First Clinical Medical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, Guangdong Province, China
  • Received:2020-03-12 Revised:2020-03-18 Accepted:2020-04-15 Online:2021-02-28 Published:2020-12-02
  • Contact: Jiang Ziwei, MD, Associate chief TCM physician, Master’s supervisor, First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, Guangdong Province, China
  • About author:Cai Qunbin, Master, Attending physician, First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, Guangdong Province, China
  • Supported by:
    the National Natural Science Foundation of China, No. 81673996; the Special Clinical Research Project Named “Innovation and Strengthening Hospital” of the First Affiliated Hospital of Guangzhou University of Chinese Medicine, No. 2019IIT11

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Abstract: BACKGROUND: The proximal femur anti-rotation intramedullary nail is an ideal internal fixation method for the treatment of intertrochanteric fractures, but there is still a 6% to 21% failure rate of internal fixation. Tip-apex distance is considered as an important cause of postoperative proximal femur anti-rotation intramedullary nail failure. Tip-apex distance is the sum of the distance from the tip of lag screw to the vertex of femoral head measured on anteroposterior and lateral X-ray films. Most scholars now believe that the tip-apex distance of head pulp nail ≤ 25 mm has a good prognosis, but there is still a lot of controversy.

OBJECTIVE: To investigate the biomechanical differences of the treatment of intertrochanteric femoral fractures by proximal femoral anti-rotation intramedullary nail with different tip-apex distances and provide a new idea and experimental basis for the clinical treatment of intertrochanteric fractures. 

METHODS: CT data of one volunteer were imported into Mimics 19.0 and Geomagic studio 2017 software to extract and optimize the three-dimensional model of the right femur. SolidWorks 2017 software was used to draw the internal fixation model and assemble it with the AO2.1 type fracture femur model in different tip-apex distance according to the standard operation technology. Totally four models with tip-apex distance of 15, 20, 25, and 30 mm were obtained and imported into HyperMesh 14.0 software to mesh. The four models were imported into Abaqus 2016 software in inp format to set up with material property parameters, boundary conditions and applied loads. Finally, operation results were viewed in the visualization module.  

RESULTS AND CONCLUSION: (1) When tip-apex distance was too large (30 mm) or too small (15 mm), the stress at the proximal femur was reduced, but the displacement of the femur head and neck fragment and the lesser trochanter fragment was larger and the inversion was more serious. When tip-apex distance was in the middle (20, 25 mm), the displacement and varus of femoral head and neck fragment were small, and the lesser trochanteric fragment was basically unshifted. (2) In the treatment of intertrochanteric femur fractures, tip-apex distance should be adjusted to 20-25 mm to reduce displacement and obtain a better biomechanical effect.

Key words: bone, fracture, tip-apex distance, femur, intertrochanteric fracture, proximal femoral nail anti-rotation, finite element analysis, biomechanics

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