Triangular support intramedullary nail: A new internal fixation innovation for treating intertrochanteric fracture...

Proximal femoral nail anti-rotation (PFNA) and Gamma nail were recommended for intertrochanteric fracture, however, with high rate of post-operation complications. The triangular support intramedullary nail (TSIN) was designed to reduce the risk of postoperative complications related to Gamma nail and PFNA, and the aim is to compare the biomechanical characters of Gamma nail, PFNA and TSIN for fixation of intertrochanteric fracture and prove the rationality of the concept of triangle fixation in the treatment of intertrochanteric fractures.

The finite element model of proximal femur was constructed according to the CT data of femur. Intertrochanteric fracture models with Evans type Ⅰ and Ⅳ were established and fixed with Gamma nail, PFNA and TSIN by UG-NX 12.0. The finite element analysis software was used to compare the stress distribution and displacement of three implants fixation models.

Under axial loading of 600 N, the peak stress and maximum displacement of intact proximal femur was 13.78 MPa and 1.33 mm, respectively. The maximum stress of TSIN for fixation of Evans type Ⅰ and Ⅳ intertrochanteric fractures was 86.23 MPa and 160.63 MPa which was significantly lower than that of Gamma nail and PFNA. The maximum relative displacement of fracture section in Gamma nail and PFNA fixation models was 0.18 mm and 0.19 mm which has 135% and 148% higher than in TSIN fixation models for fixing Evans type Ⅰ intertrochanteric fracture, and 0.47 mm and 0.59 mm which has 91% and 140% higher than in TSIN fixation models for stabilization of Evans type Ⅳ intertrochanteric fracture.

Compared with Gamma nail and PFNA fixation, TSIN has superior advantages in stress distribution and construct stability. We believe that triangle fixation concept help to reduce the risk of post-operative complications associated with PFNA and Gamma nail and improve the clinical effect of intertrochanteric fracture.