Objective—To conduct an in vitro investigation of the
biomechanical characteristics of the canine lumbar
spinal column in flexion and extension and measure
the destabilizing effects of multiple consecutive unilateral
and bilateral hemilaminectomies.
Sample Population—30 isolated multisegmental
spinal units (L1-L4) from nonhypochondroplastic dogs
weighing 15 to 30 kg.
Procedure—Physically normal and surgically altered
spinal specimens were subjected to 4-point bending
in flexion and extension to determine effects of multiple
consecutive hemilaminectomies on the basis of
analysis of test system load-displacement data. Six
groups with 5 spinal columns in each were defined on
the basis of the following procedures: hemilaminectomy
at L2-L3, 2 adjacent hemilaminectomies at L1-
L3, 3 adjacent hemilaminectomies at L1-L4, bilateral
hemilaminectomies at L2-L3, 2 bilateral hemilaminectomies
at L1-L3, and no hemilaminectomy (intact).
Spinal stability before and after surgery was determined
in all groups. Each group served as its own
control for nondestructive testing. Spinal strength
was evaluated through destructive testing to determine
deformation at failure, strength to failure, and
mode of catastrophic failure. The intact group served
as the control for destructive testing.
Results—Stability in extreme flexion and extreme
extension did not change significantly following any
hemilaminectomy procedure. Postoperative stability
within the neutral zone was significantly decreased in
all groups. Range of motion within the neutral zone
was not significantly different from the intact condition
in any group.
Conclusions and Clinical Relevance—Multiple
hemilaminectomies did not decrease stiffness of the
lumbar spinal column during flexion and extension.
These results support clinical recommendations
regarding multiple consecutive hemilaminectomies in
dogs. (Am J Vet Res 2003;64:1139–1145)
Objective—To determine the plasma pharmacokinetics
and synovial fluid concentrations after oral administration
of single and multiple doses of celecoxib in
Animals—7 adult Greyhounds.
Procedure—Dogs received celecoxib (median
dose, 11.8 mg/kg [range, 11.5 to 13.6 mg/kg], PO,
q 24 h) for 10 days. Blood samples were collected
prior to administration of celecoxib and serially for
24 hours after the 1st and 10th doses were administered.
A synovial joint catheter was placed into a
stifle joint in each dog for collection of synovial fluid
samples. Concentrations of celecoxib in plasma and
synovial fluid were quantified by use of a validated
liquid chromatography/mass spectrometry method.
Identification of hydroxy- and carboxyl-celecoxib in
plasma and synovial fluid was also performed.
Pharmacokinetic parameters were determined by
use of noncompartmental analysis.
Results—Administration of multiple doses of celecoxib
resulted in a significant decrease (40%) in median
area under the curve (AUC) values and a corresponding
decrease in median maximum concentrations
(Cmax; 2,620 to 2,032 ng/mL) between the 1st
and 10th doses. Synovial fluid concentrations were
less than the corresponding plasma concentrations at
all times except 24 hours after administration of the
10th dose of celecoxib.
Conclusions and Clinical Relevance—Celecoxib distributes
into the synovial fluid of Greyhounds.
Although the exact mechanism for the decreases in
AUC and Cmax is not known, results suggested that
the plasma pharmacokinetics of celecoxib are different
after administration of multiple doses in
Greyhounds. These findings warrant further investigation
on the absorption, distribution, metabolism, and
elimination of celecoxib in Greyhounds and other
breeds of dogs. (Am J Vet Res 2005;66:1441–1445)