Biomechanical evaluation of three different fixation methods in tibial tuberosity transposition in cats

Objectives
This study aimed to compare three different fixation techniques for tibial tuberosity transposition (TTT) in cats in a non-cyclic load-to-failure model. The objective was to determine whether there was a significant difference between the maximum load at failure (MLF) and stiffness between a two-pin tension band wire construct (2PTBW), a two-pin construct with a maintained distal cortical attachment (2PDA) and a two-pin construct (2P), and to report the modes of failure of each group.

Methods
Tibiae from cat cadavers (n = 40) were allocated to one of four groups: 2PTBW, 2PDA, 2P and control (no surgery). The respective technique was performed on each tibia with a vertical alignment of the pins. Biomechanical testing was performed in a non-cyclic load-to-failure model; MLF, stiffness and mode of failure were recorded. Statistical analyses included one-way ANOVA and pairwise comparisons.

Results
The 2P group had a significantly lower MLF than the 2PTBW, 2PDA and control groups (P <0.05) and a significantly lower stiffness than the 2PDA and control groups (P <0.05). There was no significant difference between 2PTBW and 2PDA. The most common mode of failure in the 2PTBW group was vertical tearing of the tibial tuberosity, while in the 2PDA group, the distal cortical attachment fractured and the pins subsequently pulled out. The 2P group most commonly failed because of pin pull-out.

Conclusions and relevance
The 2PDA technique demonstrated similar strength to the 2PTBW technique in a load-to-failure model. The 2P technique was the weakest of the three. This study provides a foundation for further clinical research.