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

Authors: 
Marturello DM, von Pfeil DJF, Déjardin LM
Vet Surg. 2019 Dec 11. doi: 10.1111/vsu.13364

OBJECTIVE: To 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 DESIGN: Experimental.

SAMPLE POPULATION: Fracture gap constructs and intact explanted bone surrogates.

METHODS: Fracture 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).

RESULTS: The 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).

CONCLUSION: We 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 SIGNIFICANCE: Our results provide evidence to conclude that the small I-Loc nails may be valid alternatives to other osteosynthesis options for feline fracture repair.