Quantitative Analysis of the Intramedullary Arterial Supply of the Feline Tibia: is There a Causal Relationship to Delayed and Nonunion Fracture Healing?

Abstract

Clinical observations suggest that feline tibial fractures are prone to delayed union and nonunion healing complications. This study sought to quantitatively describe the intramedullary arterial supply of the adult feline tibia and determine if the arterial supply is different from that of adult small dogs, who seemingly do not exhibit the same rates of delayed and nonunion fracture healing. Our null hypothesis was that the intramedullary arterial density and diameter of the nutrient artery in the adult feline tibia was the same as the age and size matched dog. Using microvascular injection and modified Spalteholz techniques, cadaveric feline and canine pelvic limbs were prepared to characterize the intramedullary arterial supply of the tibia. Processed specimens were evaluated using the ImageJ morphometric program. Statistical comparisons were made between cats and dogs for the intramedullary arterial density and diameter of the nutrient artery. There was no significant difference in the intramedullary arterial density between dog and cat tibiae. The feline nutrient artery diameter (0.5497 ± 0.0552mm) was significantly different than the canine nutrient artery (0.2976 ± 0.0423mm) in the distal section of bone. Dogs subjectively exhibited more branching vessels in the distal and mid-diaphyseal bone sections. Delayed fracture healing in the feline tibia does not appear to be due to diminished intramedullary arterial supply. However, a lack of diffuse arborization of the arterial supply to the cortex of the mid-diaphyseal and distal feline tibia may explain, in part, why feline tibial delayed or nonunions may be more common than those in dogs.