Biomechanical comparison of standard-of-care endoprosthesis limb-sparing technique to a gap group with stainless steel plates and no endoprostheses in the distal radial site of dogs.

Objective: To compare the biomechanical properties of standard-of-care limb salvage stainless steel plates with metal endoprosthesis constructs to constructs without endoprosthesis.

Methods: This was a cadaveric biomechanical study including 5 pairs of normal canine thoracic limbs randomly allocated into 2 groups: limbs with a second-generation, 11.5-mm Veterinary Orthopedic Implants stainless steel plate and a 122-mm stainless steel with endoprosthesis (SS-E) and limbs without endoprostheses or stainless steel with a gap (SS-G). Standard limb-spare surgery was performed and reconstructed with or without endoprostheses (ie, gap). Limbs were tested in axial loading until failure, and load-deformation curves were used to determine the biomechanical properties of the constructs, compared using a Wilcoxon matched-pairs signed-rank test. Failure modes were compared descriptively.

Results: Yield load (644 ± 523 N and 288 ± 153 N), yield energy absorbed (1,126 ± 1,695 N/mm and 239 ± 251 N/mm), and ultimate energy absorbed (39,732 ± 11,679 N/mm and 5,175 ± 878 N/mm) were significantly different between the SS-E and SS-G groups, respectively. Stiffness (360 ± 64 N/mm and 180 ± 50 N/mm) and ultimate load (3,385 ± 512 N and 747 ± 98 N) were not. The mode of failure varied between groups, with 2 SS-E constructs failing by humeral fracture and 3 by plate bending at the most distal radial or radiocarpal screw holes, whereas all SS-G constructs failed by plate bending midgap.

Conclusions: Limbs incorporating endoprosthesis were biomechanically superior to limbs reconstructed with a gap.

Clinical relevance: Limbs reconstructed with locking 11.5-mm Veterinary Orthopedic Implants plates without endoprosthesis may fail at physiological forces during trot or run.