Biomechanics of subtrochanteric fracture fixation using short cephalomedullary nails: A finite element analysis

Abstract

A finite element analysis was performed to evaluate the stresses around nails and cortical bones in subtrochanteric (ST) fracture models fixed using short cephalomedullary nails (CMNs). A total 96 finite element models (FEMs) were simulated on a transverse ST fracture at eight levels with three different fracture gaps and two different distal locking screw configurations in both normal and osteoporotic bone. All FEMs were fixed using CMNs 200 mm in length. Two distal locking screws showed a wider safe range than 1 distal screw in both normal and osteoporotic bone at fracture gaps ≤ 3 mm. In normal bone FEMs fixed even with two distal locking screws, peak von Mises stresses (PVMSs) in cortical bone and nail constructs reached or exceeded 90% of the yield strength at fracture levels 50 mm and 0 and 50 mm, respectively, at all fracture gaps. In osteoporotic bone FEMs, PVMSs in cortical bone and nail constructs reached or exceeded 90% of the yield strength at fracture levels 50 mm and 0 and 50 mm, respectively, at a 1-mm fracture gap. However, at fracture gaps ≥ 2 mm, PVMSs in cortical bone reached or exceeded 90% of the yield strength at fracture levels ≥ 35 mm. PVMSs in nail showed the same results as 1-mm fracture gaps. PVMSs increased and safe range reduced, as the fracture gap increased. Short CMNs (200 mm in length) with two distal screws may be considered suitable for the fixation of ST transverse fractures at fracture levels 10 to 40 mm below the lesser trochanter in normal bone and 10 to 30 mm in osteoporotic bone, respectively, under the assumptions of anatomical reduction at fracture gap ≤ 3 mm. However, the fracture gap should be shortened to the minimum to reduce the risk of refracture and fixation failure, especially in osteoporotic fractures.

Long-term results comparison after anterior cervical discectomy with BGS-7 spacer (NOVOMAX®-C) and allograft spacer: A prospective observational study

“…The Young’s modulus and Poisson’s ratio were applied to each moiety using previously published data in the literature. ( Table 2 ) ( Kumaresan et al, 1999 ; Kim et al, 2020 ; Kwak et al, 2021 )…”

Strategies for Pertrochanteric Fracture Reduction and Intramedullary Nail Placement: Technical Tips and Tricks

“…Despite this, a recent randomized controlled trial and biomechanical studies have demonstrated that for fractures with less than 3 cm of subtrochanteric extension, short nails resulted in comparable outcomes with long nails. [16][17][18] Pertrochanteric fracture in the setting of a capacious proximal canal (type C proximal femoral canal as defined by Dorr et al 19 ) is another factor which has been raised as a possible indication for long-nail selection because of concern for lack of stability and nail toggle; however, this has not been borne out in the literature. 20 The authors prefer to use short nails when possible.…”

Biomechanical Behavior of Dynamic vs. Static Distal Locking Intramedullary Nails in Subtrochanteric Femur Fractures

“…Despite the advantages of these computational techniques, there are still limited publications relating to studies of the biomechanical behaviors of intramedullary nails in subtrochanteric fractures in the femur. Most of them focus on intramedullary nailing of femoral shaft fractures [14][15][16][17], and very few articles specifically address subtrochanteric fractures [18][19][20][21]. Kwak DK et al [18], Jang CY et al [19], and Lee WC et al [20] presented different works related to the study of the application of short cephalomedullary nails for the treatment of subtrochanteric and intertrochanteric fractures using finite element models.…”

“…Most of them focus on intramedullary nailing of femoral shaft fractures [14][15][16][17], and very few articles specifically address subtrochanteric fractures [18][19][20][21]. Kwak DK et al [18], Jang CY et al [19], and Lee WC et al [20] presented different works related to the study of the application of short cephalomedullary nails for the treatment of subtrochanteric and intertrochanteric fractures using finite element models. Kwak DK et al [18] and Jang CY et al [19] investigated the stresses around the nails and cortical bones to determine the most appropriate type of short cephalomedullary nail for different fracture levels.…”