Mechanical comparison of two small interlocking nails in torsion using a feline bone surrogate

Abstract

ObjectiveTo compare the torsional behavior of two small angle‐stable interlocking nails (I‐Loc and Targon) with that of locking compression plates (LCP). To evaluate the effect of implant removal on the torsional strength of feline bone surrogates.Study designExperimental.Sample populationFracture gap constructs and intact explanted bone surrogates.MethodsFracture gap constructs were stabilized with one of six implants (I‐Loc 3 and 4, Targon 2.5 and 3.0, LCP 2.0 and 2.4) and then cyclically tested in torsion (n = 4/group). To simulate implant removal, intact surrogates with implant‐specific pilot holes were then twisted to failure (n = 4/group). Torsional compliance (TC; °/Nm), angular deformation (AD; °), and failure torque (FT; Nm) were statistically compared (P < .05).ResultsThe I‐Loc 4 had the smallest TC and AD of all constructs (P < .05). The largest TC (P < .05) was seen with the LCP 2.0. The Targon 2.5 had the largest AD (P < .05) secondary to locking interface slippage. Targon surrogates FT were the lowest of all groups (P < .05). Conversely, there was no difference between the FT of the I‐Loc, LCP, and intact surrogates (P > .05).ConclusionWe showed that I‐Loc nails provided greater torsional stability than size‐matched Targon nails and LCPs. Conversely, Targon 2.5 locking interface slippage may jeopardize that construct's stability. Furthermore, the significantly reduced bone surrogate torsional strength provided evidence that the large Targon bolt holes increased the risk of postexplantation iatrogenic fracture.Clinical significanceOur results provide evidence to conclude that the small I‐Loc nails may be valid alternatives to other osteosynthesis options for feline fracture repair.

In vitro comparison on a gap fracture model of a novel angle-stable interlocking nail to locking plate fixation in torsion, compression and bending

“…Because of their intramedullary position, thereby closer to the axis of the bone, and their larger area of moment, interlocking nails allow a more stable fracture fixation than plates. Thus, they have significant biomechanical advantages over plates promoting a better distribution of stresses (Marturello et al 2020). Moreover, angle-stable locking design as described in this study shows a reduced slack that will allow a more stable fixation of the facture (D ejardin et al 2014).…”

Evaluation of a Feline Bone Surrogate and In Vitro Mechanical Comparison of Small Interlocking Nail Systems in Mediolateral Bending

“…Sample sizes for all parts were selected based on previous studies from our laboratory. 3,7,20,22 In Part 1: Following approval by the Institutional Animal Care and Use Committee, 10 feline femurs were harvested from cats humanely euthanatized for reasons unrelated to this study. The bending structural properties of native feline femurs were compared with those of the previously designed FBS.…”

“…18 The I-Loc 3 and 4 mm share design features with the larger models, 7 including locking threaded bolts that engage threaded cannulations at each extremity of the nail. While a previous study demonstrated greater torsional stability of the small I-Loc compared with size-matched Targon nails (Targon; B. Braun Aesculap, Tuttlingen, Germany) and LCP, 20 this system has yet to be evaluated in bending.…”

“…Compliance rather than stiffness was computed since testing was conducted under load control. 3,7,20,28 Outcome measures consisted of the following: Part 1 BC (degrees/Nm), AD (degrees), F M (Nm) and failure mode; Part 2 BC and AD; Part 3 F M and failure mode.…”

“…bending strength) was defined as the maximum moment prior to either a 10% drop in moment magnitude or visible structural failure of the native bone or FBS. 20 Failure modes were recorded and reported as descriptive statistics.…”