Summary
Thirteen pairs of tibiae were excised from adult mongrel dogs following a mean recovery
period of 24.2 weeks after unilateral total hip arthroplasty (THA). Prior to euthanasia,
peak vertical dynamic load, as a percent of body weight, was determined for each limb
at a walking pace. Four contiguous proximal sections and one transverse cortical midshaft
section, 5mm thick, were harvested from each tibia. Contact Faxitron radiographs of
the sections were quantified, using video digitizing software, to compare mean apparent
density measures between the treated (THA) and intact limbs. There was a significant
difference in mean apparent density of cancellous bone with the treated limb having
a lower apparent density than the intact limb. The mean cortical area at the midshaft
was significantly lower and the medullary area significantly higher among tibiae from
the treated side, as compared to the contra-lateral tibiae. Resistance to bending
and tension at the midshaft of each bone were determined using the second moment of
area about cranio-caudal (Ix) and mediolateral (Iy) axes. The mean Iy values for the
treated limbs were significantly lower than for the intact limbs. Therefore, measurable
adaptive bone remodeling appears to be present in both cancellous and cortical bone
in the tibia due to decreased mechanical loading.
Key words
Osteopenia - Osteoporosis - Gait - Canine model
