Biomechanical Comparison of Three Stabilization Methods for Tibial Tuberosity Fractures in Dogs: A Cadaveric Study

Abstract

Objective The aim of this study was to compare the biomechanical properties of a hybrid external skeletal fixator (HESF) construct to the placement of paired interfragmentary Kirschner wires alone, and pin and tension band wire (PTBW) fixation for the stabilization of simulated tibial tuberosity fractures in dogs. Study Design Tibias were harvested from 12 skeletally mature dog cadavers weighing 20 to 30 kg. An osteotomy was made through the base of the tibial tuberosity, which was subsequently repaired with either paired Kirschner wires, PTBW fixation or a HESF. A tensile load was applied to the tibial tuberosity until failure occurred. Mode of failure was described and biomechanical parameters obtained were compared between fixation groups. Results The PTBW fixation and HESF construct afforded greater stiffness and load at 3 mm of axial displacement compared with fixation with Kirschner wires alone. There was no significant difference in stiffness and load at 3 mm displacement between PTBW and HESF fixation. Failure occurred by bending and pullout of the Kirschner wires for all fixation groups, preceded by untwisting of the knot in PTBW specimens. Conclusion The HESF may provide a favourable alternative to PTBW fixation for tibial tuberosity avulsion fracture stabilization in dogs with substantial remaining growth potential.

Influence of Kirschner-Wire Insertion Angle on Construct Biomechanics following Tibial Tuberosity Osteotomy Fixation in Dogs

“…9 Our results are in agreement with prior studies where the mode of construct failure was tibial tuberosity avulsion with pull-out of Kirschner wires, regardless of orientation. 8,9,16 Clinically, a partial tibial tuberosity osteotomy is often preferred by surgeons, thus preserving distal bone stock or periosteal attachments to act as a hinge to avoid the need for a tension band wire. We performed a complete osteotomy; however, preservation of these distal attachments may have altered the biomechanical properties or mode of failure of repaired constructs.…”

“…14 The addition of a hybrid external fixation system to a double Kirschner wire construct has also been described for stabilization of tibial tuberosity avulsion fractures and may provide an alternative method of tibial tuberosity osteotomy fixation, especially in immature dogs where concern exists for premature closure of the tibial apophysis or where substantial growth potential remains. 16 Postulated reasons for concurrent pull-through of the Kirschner wires in our study may include younger dogs with more compliant cortical bone, area moment of inertia of the Kirschner wires used, or biomechanical methods of destructive testing used.…”

“…The findings of our study are in agreement with a prior biomechanical study evaluating Kirschner wire fixation methods in dogs. 8,16 In an ex-vivo study by Zide and colleagues, failure forces were 555.5 AE 113.8 N for vertically oriented Kirschner wires. 8 Although this study differed with respect to the biomechanical variables analyzed, tibial tuberosity fixation in this study was performed utilizing Kirschner wires oriented in parallel fashion and proximal and distal to one another in a sagittal plane with similar failure forces.…”

Biomechanical comparison of one pin versus two pin fixation in a canine tibial tuberosity avulsion fracture model

“…A material‐testing machine (Instron Model 5969, Instron Corporation, Canton, Massachusetts) was used to test each specimen. The specimen/resin filled cups were mechanically secured in a custom‐made jig with the tibia positioned at a normal canine standing angle of 60° from the horizontal axis, and a carbon‐fiberglass ring fixator was used to clamp the patellar ligament distal to the patella and quadriceps muscles as previously described 3 . The ring was then attached to the cross head of the load frame via cable wire (Figure 2).…”

“…Clinical failure was defined as 3 mm separation of the cranial aspect of the transverse osteotomy (artificial fracture) 3,14,15 . Descriptive observations for ultimate failure patterns following clinical failure were noted.…”