Experimental and probabilistic analysis of distal femoral periprosthetic fracture: a comparison of locking plate and intramedullary nail fixation. Part A: experimental investigation

Abstract

The following is a two-part study. Part A evaluates biomechanically intramedullary (IM) nails vs. locking plates for fixation of femoral fractures in osteoporotic bone. Part B of this study introduces a deterministic finite element model of each construct type and investigates the probability of periprosthetic fracture of the locking plate compared with the retrograde IM nail using Monte Carlo simulation. For Part A, an extra-articular, metaphyseal wedge fracture pattern was created in 11 osteoporotic fourth-generation composite femurs. Fixation was performed with a locking plate or a retrograde IM nail. Axial, torsion and bending cyclic loading to simulate post-operative damage accumulation were performed followed by ramped load to failure. Locking plates proved to be more stable (using stiffness as the determining factor) in osteoporotic bone as observed under low load cycle conditions. However, some of these advantages were offset by a greater incidence of sudden periprosthetic fracture observed under ramped loading conditions. Cadaveric, osteoporotic femurs included as a case study also exhibited periprosthetic fracture, but failure was accompanied by catastrophic comminution of the cortex. Periprosthetic failure at the implant end including bone comminution is difficult to salvage with revision fixation. The weakened trabecular matrix and thinned cortex of osteoporotic bone may increase the incidence of periprosthetic fracture. It is, therefore, essential for the surgeon to consider all possible loading scenarios when recommending an ideal implant for the osteoporotic patient.

Screw-Bone Interface Modelling in Locking Plate Fe Models

“…It is widely accepted that muscle contributions are key to biomechanical modelling of the femur (Phillips, 2009, Sverdlova and Witzel, 2010, Konstantinidis et al, 2012, Shih et al, 2008. Nevertheless, the vast majority of predictions of implant performance are made using in vitro models (or in vitro style models using FE) which neglect them (Granata et al, 2012, Talaia et al, 2007, Ebrahimi et al, 2012, Salas et al, 2011a, Completo et al, 2007, Heiney et al, 2012, Firoozabadi et al, 2012, Schmidt et al, 2013, Zlowodzki et al, 2004, Arnone et al, 2013, Tomaszewski et al, 2010, Wieding et al, 2012, Demos et al, 2012. While some studies have included the effect of key muscle groups for the proximal femur (Konstantinidis et al, 2012), in both computational and experimental models additional restraint is imposed which does not exist in vivo; these will influence the results (Phillips, 2009).…”

“…(a) The distal femur is clamped; the hip is restrained in the coronal and stagittal planes (A-P and M-L) (Granata et al, 2012, Liang et al, 2012, Salas et al, 2011a).…”

Influence of gap size, screw configuration, and nail materials in the stability of anterograde reamed intramedullary nail in femoral transverse fractures

“…In [24] a combination of experimental and numerical methods is used to evaluate the stress distribution in an anterograde intramedullary nail. In [25,26] a comparison between nails and locking plates in a metaphyseal wedge fracture in synthetic osteoporotic bone is executed. Static versus dynamic fixation techniques are compared in [27].…”

Fixation of Periprosthetic Supracondylar Femur Fractures Above Total Knee Arthroplasty – The Indirect Reduction Technique with the Condylar Blade Plate and the Minimally Invasive Technique with the LISS

“…It avoids the need for precise reduction and exposure of the bone, thus reducing surgical trauma (Thielemann et al, 1988;Gerber et al, 1990;Ganz et al, 1991;Rozbruch et al, 1998;Perren, 2002). The locked plates provided significantly greater fixation stability than the standard plate, blade plate, condylar buttress plate, dynamic condylar screws, or the retrograde nail in biomechanical studies involving axial loading with mild to moderate osteoporotic femurs (Egol et al, 2004;Ganz et al, 1991;Koval et al, 1997;Marti et al, 2001;Salas et al, 2011;Zlowodzki et al, 2004). The probability of periprosthetic fracture of the locking plate compared to the retrograde IM nail (in a deterministic finite element model of each construct type) was higher under the applied loading conditions (locking plate 21.8% versus IM nail 0.019%) (Salas et al, 2011).…”

“…The locked plates provided significantly greater fixation stability than the standard plate, blade plate, condylar buttress plate, dynamic condylar screws, or the retrograde nail in biomechanical studies involving axial loading with mild to moderate osteoporotic femurs (Egol et al, 2004;Ganz et al, 1991;Koval et al, 1997;Marti et al, 2001;Salas et al, 2011;Zlowodzki et al, 2004). The probability of periprosthetic fracture of the locking plate compared to the retrograde IM nail (in a deterministic finite element model of each construct type) was higher under the applied loading conditions (locking plate 21.8% versus IM nail 0.019%) (Salas et al, 2011). By using an internal fixator with locked screw heads, the screw loading is primarily bending and not pullout (Gautier & Sommer, 2003;Wagner & Frigg, 2006).…”