Objective—To determine total stiffness and gap stiffness
of an external fixation system in a canine
mandibular fracture gap model incorporating a full
interdental pin as the only point of rostral fixation in a
bilateral type-I external fixator.
Sample Population—10 canine mandibles.
Procedure—Bilateral mandibular ostectomies were
performed between premolars 3 and 4. A type-I external
fixator incorporating a full interdental pin was
placed to stabilize a 0.5-cm fracture gap. Four pin configurations
(intact mandibular bodies with fixator;
ostectomized mandibular bodies and complete fixator;
ostectomized mandibular bodies with caudal pins
of rostral fragment cut; ostectomized mandibular bodies
with all pins of rostral fragment cut) were tested
in dorsoventral bending 5 times on each mandible.
The full interdental pin remained intact in all configurations.
Total stiffness and gap stiffness were determined
for each configuration on a materials testing
Results—Total stiffness of intact mandibles was significantly
greater than that of ostectomized mandibles,
regardless of external fixator configuration. However,
total stiffness and gap stiffness were not significantly
different among different external fixator configurations
applied to ostectomized mandibles.
Conclusion and Clinical Relevance—External fixator
configurations with only the full interdental pin engaging
the rostral fragment were as stiff as configurations
that had 2 or 4 additional pins in the rostral fragment
for the applied loads. External fixators for rostral
mandibular fractures may be rigidly secured with rostral
fragment implants applied extracortically, avoiding
iatrogenic trauma to teeth and tooth roots. (Am J Vet
Objective—To characterize ground reaction forces (GRFs) and determine whether there were correlations between forces and passive coxofemoral joint laxity in puppies.
Animals—Fifty-one 16-week-old hound-breed dogs.
Procedure—Force-plate gait evaluation and distraction radiographic imaging were performed. Ground reaction forces evaluated included x (mediolateral), y (craniocaudal breaking and propulsion), and z (vertical) peak force and impulse. Z-plane limb loading and unloading rates, loading interval, and weight distribution and y-plane stance time breaking and propulsion percentages were calculated. One-way ANOVA with the Duncan multiple range test was used to evaluate differences in gait variables among limbs. The relationships of left, right, highest, and mean distraction index (DI) with individual limb data of each dog were evaluated with the Spearman rank correlation. Left and right DIs were compared by means of linear regression analysis.
Results—Mean ± SEM DI was 0.67 ± 0.02. Left and right DIs were strongly correlated, but there were no significant relationships between DIs and gait variables. Most fore- and hind limb gait variables differed significantly, whereas paired fore- and hind limb gait variables did not. Asymmetry was most pronounced in the x- and y-planes.
Conclusions and Clinical Relevance—GRFs were consistent with those of clinically normal mature dogs, supporting an absence of association between GRF and DI in young dogs. The GRFs and elucidation of the relationship between GRFs and DI may be useful for future studies in immature dogs.
Objective—To quantify and compare the microscopic changes in articular cartilage (AC), zone of calcified cartilage (ZCC), and subchondral bone plate in femoral heads from clinically normal dogs and dogs with moderate or severe osteoarthritis.
Sample Population—Femoral heads from clinically normal dogs (n = 16) and dogs with moderate (24) or severe (14) osteoarthritis.
Procedures—Femoral heads were allocated to 3 categories (normal, moderate, or severe osteoarthritis) on the basis of radiographic findings, macroscopic findings, and histologic grade determined by use of a modified Mankin scale. Equally spaced 2-mm sections were cut in each femoral head in a coronal or transverse plane. Thickness of the AC, ZCC, and subchondral bone plate was recorded.
Results—Mean thickness of AC was significantly greater in samples with moderate and severe osteoarthritis than those considered normal. Mean thickness of the ZCC was significantly greater in samples with moderate and severe osteoarthritis than those considered normal. Mean thickness of the subchondral bone plate in samples with severe osteoarthritis was significantly greater than those with moderate osteoarthritis and those considered normal. A significant decrease in AC thickness was detected in the proximomedial area of femoral heads with severe osteoarthritis, compared with those considered normal.
Conclusions and Clinical Relevance—A cause and effect association between thickening of subchondral structures and thinning and loss of the overlying AC was not detected. Changes in AC were associated with changes in the subchondral bone plate, which is compatible with the theory of adaptation in response to altered load distribution.
Objective—To describe the histomorphometric properties
of epiphyseal and metaphyseal trabecular bone
of the proximal portion of the femur of dogs with
Sample Population—Proximal portions of a femour
from 24 dogs.
Procedure—The proximal portion of a femur was
obtained from each dog. Eleven and thirteen specimens
were sectioned in the transverse and coronal planes,
respectively. Three evenly spaced sections from each
specimen were chosen, surface stained, and digitized,
and the stained areas were preferentially selected.
Custom software was used for histomorphometric
analysis of each section. A mixed-model analysis was
used to evaluate the effect of slice location and region on
6 parameters, and a Fisher protected t test was used
when differences were detected.
Results—There was a significant difference between
the femoral head and femoral neck for all parameters
tested. In coronal sections, the femoral neck was significantly
more anisotropic than the femoral head. In
transverse sections, the craniolateral region of the
femoral neck was significantly more anisotropic than
the caudomedial and craniomedial regions.
Conclusions and Clinical Relevance—There is a
predictable cancellous microarchitecture in the proximal
portion of femurs from dogs with moderate
osteoarthritis. Trabeculae are more numerous, thicker,
and closer together but more randomly arranged in
the femoral head than in the femoral neck. Dogs with
moderate osteoarthritis had an increase in trabecular
anisotropy in the craniolateral region of the femoral
neck. However, there was no corresponding increase
in trabecular alignment of the proximomedial region
of the femoral head. Results support an association
between trabecular alignment and the progression of
osteoarthritis. ( Am J Vet Res 2005;66:150–155)
Objective—To evaluate correlations among measurements on radiographic and computed tomography (CT) images with articular cartilage microdamage in lax hip joints of dogs.
Animals—12 adult mixed-breed hounds.
Procedures—Pelvic CT and radiography were performed. Hip joints were harvested following euthanasia. Orthopedic Foundation for Animals (OFA) and PennHIP radiograph reports were obtained. Norberg angle (NA) and radiographic percentage femoral head coverage (RPC) were determined. Center-edge angle (CEA), horizontal toit externe angle (HTEA), ventral acetabular sector angle (VASA), dorsal acetabular sector angle (DASA), horizontal acetabular sector angle (HASA), acetabular index (AI), and CT percentage femoral head coverage (CPC) were measured on 2-dimensional CT images. Femoral head–acetabular shelf percentage was measured on sagittal 3-dimensional CT (SCT) and transverse 3-dimensional CT (TCT) images. Light microscopy was used to score joint cartilage. Relationships of OFA confirmation and PennHIP osteoarthritis scores with radiography, CT, and cartilage variables and relationships of cartilage scores with radiography and CT measurements were evaluated with Spearman rank correlations. Pearson correlation was used for relationships of distraction index (DI) with radiography, CT, and cartilage variables.
Results—Significant relationships included PennHIP osteoarthritis score with cartilage score, CEA, HTEA, DASA, AI, CPC, and TCT; OFA confirmation score with cartilage score, NA, RPC, CEA, HTEA, DASA, AI, CPC, and TCT; cartilage score with NA, RPC, CEA, HTEA, DASA, HASA, AI, and TCT; and DI with cartilage score, CEA, HTEA, DASA, HASA, AI, and CPC.
Conclusions and Clinical Relevance—CT appeared to be a valuable imaging modality for predicting cartilage microdamage in canine hip joints.
Objective—To determine fibroblast viability, assess
development of apoptosis, and evaluate tissue hypoxia
via histochemical, in-situ hybridization, or immunohistochemical
staining in ruptured and intact cranial
cruciate ligaments (CCLs) of dogs.
Animals—32 dogs with ruptured CCLs, and 8 aged
and 19 young dogs with intact CCLs.
Procedure—Markers of cell viability (lactate dehydrogenase
[LDH]), apoptosis (terminal deoxynucleatidyl
transferase-mediated deoxyuridine triphosphate-nick
end labeling [TUNEL] method), and hypoxia (hypoxiainducible
factor-1α [HIF-1α] monoclonal antibody)
were applied to CCL specimens; positive cells were
assessed objectively (LDH) and subjectively (TUNEL
and HIF-1α) in the main axial tissue component (core)
and synovial intima and subintima (epiligamentous tissue).
Results—Viable fibroblasts were seen in all intact and
ruptured CCLs. More nonviable cells were found in
the core regions of ruptured CCLs and intact CCLs of
young dogs than in the epiligamentous regions.
Number of nonviable cells in the core region of ruptured
CCLs was greater than that in intact CCLs of
young and aged dogs, whereas the number in the
epiligamentous region was similar in all specimens.
The TUNEL and HIF-1αstaining was only found in the
epiligamentous region of ruptured CCLs.
Conclusions and Clinical Relevance—Ruptured
CCLs contained a high number of nonviable cells but
not a great number of apoptotic cells. Repair processes
in the epiligamentous region of the CCL include a
metabolic response to hypoxia, suggesting that
necrosis of ligament fibroblasts and transformation of
surviving cells to a spheroid phenotype may be a
response to hypoxia cause by microinjury or inadequate
blood flow. (Am J Vet Res 2003;64:1010–1016)
Objective—To compare effects of synovectomy performed
by use of monopolar radiofrequency energy
(MRFE) versus mechanical debridement in rabbits
with induced inflammatory arthritis.
Animals—25 mature female New Zealand White rabbits.
Procedure—Inflammatory arthritis was induced in
both femoropatellar joints of each rabbit. Joints then
were treated by mechanical debridement or MRFE
treatment or served as sham-operated controls.
Rabbits were euthanatized 2 weeks or 3 months after
surgery. Biopsy specimens of synovium were analyzed
by use of light microscopy.
Results—At 2 weeks after surgery, samples from
MRFE-treated joints had fewer plasma cells and more
heterophils than the other 2 groups and more lymphocytes
than sham-operated controls, whereas
samples from mechanically debrided joints had
greater numbers of lymphocytes and heterophils than
sham-operated controls. At 3 months after surgery,
samples from MRFE-treated joints had fewer plasma
cells than sham-operated controls, more heterophils
than mechanically debrided and sham-operated controls,
and more macrophages than mechanically
debrided joints. There was no difference in synovial
ablation, synovial proliferation, or fibrosis among the 3
groups at 2 weeks or 3 months after surgery.
Conclusions and Clinical Relevance—Analysis of
results of this study documented a similar degree of
synovial ablation when comparing use of MRFE to
mechanical debridement. In rabbits with this method
of induced inflammatory arthritis, there were no
detectable benefits of MRFE or mechanical debridement
on the synovium, compared with results for
sham-operated control joints, at 2 weeks and 3
months after surgery for most of the synovial variables
evaluated. ( Am J Vet Res 2004;65:573–577)
Objective—To describe cancellous architecture of the
proximal portion of the femur in dogs with osteoarthritis.
Animals—30 dogs with coxofemoral osteoarthritis.
Procedure—All dogs had femoral head and neck excision
or total hip arthroplasty. Histomorphometry software
was used to analyze computer images of 100-
μm-thick coronal and transverse plane sections of the
head and neck of the femur. Histologic preparations
of coronal and transverse sections of articular cartilage
Results—Bone volume/total volume, trabecular thickness,
trabecular number, and bone surface/total volume
were significantly higher in the femoral head
than femoral neck. Trabecular alignment (anisotropy)
and separation were significantly higher in the
femoral neck than femoral head. Anisotropy was significantly
increased in the medial portion of the
femoral head in the coronal plane and in the cranial
portion of the femoral neck in the transverse plane,
compared with healthy dogs. The medial half of
femoral head cartilage that overlies the proximomedial
cancellous bone region had significantly more
degraded cartilage than the lateral half. Histologic
grades for cranial and caudal halves of femoral head
articular cartilage were similar.
Conclusions and Clinical Relevance—Most findings
were similar to those in healthy dogs. Greater trabecular
alignment in the proximomedial region of the
femoral head and craniolateral region of the femoral
neck in dogs with osteoarthritis suggests an altered
transfer of load through the coxofemoral joint. Greater
cartilage degradation on the medial half of the femoral
head supports an association between increased trabecular
alignment and cartilage degradation. (Am J
Vet Res 2000;61:1267–1272)