Tibial Tuberosity Transposition Fixation with a Locking Plate during Medial Patellar Luxation Surgery: An Ex Vivo Mechanical Study

Vet Comp Orthop Traumatol. 2022 Mar;35(2):96-104. doi: 10.1055/s-0041-1736217. Epub 2021 Oct 11.

Abstract

Objectives: The purpose of this study was to compare the load at failure, stiffness and mode of failure between three types of tibial tuberosity transposition fixation techniques: (a) pin and figure-8 tension band wire (Pin-TBW), (b) locking plate with pin and a tension band wire (Plate-Pin-TBW) and (c) locking plate with a pin (Plate-Pin).

Methods: Six pairs of raccoon dog cadaveric tibiae were tested in Phase I Pin-TBW versus Plate-Pin-TBW and seven pairs in Phase II Plate-Pin-TBW versus Plate-Pin. One limb of each pair was randomly assigned to one of two groups for each phase. A tensile force was applied to the patellar ligament until construct failure.

Results: Pin-TBW (342N ± 54.7N) failed at a lower load than Plate-Pin-TBW (469N ± 77.3N), p = 0.00748, with all Pin-TBW failing by fracture and the majority of Plate-Pin-TBW failing by rupture of patellar ligament. Pin-TBW group Phase I, normalized with Plate-Pin-TBW Phase I, failed at a lower load than Plate-Pin group Phase II, normalized with Plate-Pin-TBW Phase II, p = 0.00467. There was no significant difference in mean load at failure, stiffness or mode at failure between the groups in the Phase II study.

Clinical significance: Although ex vivo mechanical testing does not replicate the postoperative live dog or cat, these results demonstrate lower construct strength of the Pin-TBW construct compared with the Plate-Pin construct in the raccoon dog cadaver model.

MeSH terms

  • Animals
  • Biomechanical Phenomena
  • Bone Plates* / veterinary
  • Cadaver
  • Fracture Fixation, Internal / methods
  • Fracture Fixation, Internal / veterinary
  • Patellar Dislocation* / veterinary
  • Tibia / surgery