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 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 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 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 evaluate the biomechanical properties of 4 methods for fusion of the centrodistal and tarsometatarsal joints in horses and compare them among each other and with control tarsi.
SAMPLE 24 sets of paired tarsi without substantial signs of osteoarthritis harvested from equine cadavers.
PROCEDURES Test constructs (n = 6/type) were prepared from 1 tarsus from each pair to represent surgical drilling; 2 medially to laterally placed kerf-cut cylinders (MLKCs); a single large, dorsally applied kerf-cut cylinder (DKC); and a dorsomedially applied locking compression plate (DMLCP). Constructs and their contralateral control tarsi were evaluated in 4-point bending in the dorsoplantar, lateromedial, and mediolateral directions; internal and external rotation; and axial compression. Bending, torsional, and axial stiffness values were calculated.
RESULTS Mean stiffness values were consistently lower for surgical drilling constructs than for contralateral control tarsi. Over all biomechanical testing, surgical drilling significantly reduced joint stability. The MLKC constructs had superior biomechanical properties to those of control tarsi for 4-point bending but inferior properties for external and internal rotation. The DMLCP and DKC constructs were superior to control tarsi in dorsoplantar, rotational, and axial compression directions only; DMLCP constructs had no superior stiffness in lateromedial or mediolateral directions. Only the DKC constructs had greater stiffness in the mediolateral direction than did control tarsi. Over all biomechanical testing, DMLCP and DKC constructs were superior to the other constructs.
CONCLUSIONS AND CLINICAL RELEVANCE These biomechanical results suggested that a surgical drilling approach to joint fusion may reduce tarsal stability in horses without clinical osteoarthritis, compared with stability with no intervention, whereas the DMLCP and DKC approaches may significantly enhance stability.
Objective—To evaluate the use of hydrothermal ablation
of articular cartilage for arthrodesis in horses
through investigation of the effects of joint lavage
with physiologic saline (0.9% NaCl) solution (80°C) for
various treatment times on chondrocyte viability in
the articular cartilage of the metacarpophalangeal and
metatarsophalangeal joints of cadaveric horse limbs.
Sample Population—7 pairs of metacarpophalangeal
and 8 pairs of metatarsophalangeal joints
from 8 Thoroughbreds.
Procedure—The horses were euthanatized for reasons
unrelated to musculoskeletal disease. On a random
basis, 1 joint of each pair underwent intra-articular
lavage for 5, 10, or 15 minutes with heated saline
solution (80°C); the other joint underwent sham treatment
of similar duration with saline solution at 22°C
(control). Cartilage samples from the distal articular
surface of metacarpus III (or metatarsus III), the proximal
surface of the proximal phalanx, and the lateral
and medial proximal sesamoid bones were assessed
for chondrocyte viability via confocal microscopy and
viability staining following enzymatic digestion.
Results—Compared with the control joints, findings
of both viability assays indicated that the percentage
of sites containing viable chondrocytes in heat-treated
joints was decreased. Treatment hazard ratios of 0.048
(confocal microscopy) and 0.2 (digestion assay) were
estimated. Histologically, periarticular soft tissues had
minimal detrimental effects after heat treatment.
Conclusions and Clinical Relevance—Ex vivo intraarticular
lavage with saline solution at 80°C resulted in
the death of almost all articular chondrocytes in the
joint. This technique may be a satisfactory method for
extensive cartilage ablation when performing
arthrodesis by minimally invasive techniques. (Am J Vet Res 2005;66:36–42)
Objective—To describe the cancellous bone architecture
of the head and neck of the femur in healthy
dogs by use of automated histomorphometry techniques
in conjunction with histologic grading of articular
Animals—30 mature male dogs with healthy coxofemoral
Procedure—Dogs were 1.5 to 4 years old and
weighed 27 to 37 kg. Computer images of fine-detail
radiographs of 100-µm-thick coronal and transverse
plane sections of the head and neck of the femur
(14 dogs) were analyzed by use of histomorphometry
software. Statistical comparisons among histomorphometric
indices of 4 regions were performed.
Histologic preparations of coronal and transverse
plane sections of femoral head articular cartilage
(16 dogs) were graded. Median grades for lateral,
medial, cranial, and caudal halves of the femoral head
articular cartilage were determined.
Results—Bone volume/total volume, trabecular thickness
and number, and bone surface/total volume were
significantly higher in the femoral head than in the
femoral neck. Anisotropy (trabecular alignment) and
trabecular separation were significantly higher in the
femoral neck than in the femoral head. Anisotropy was
significantly higher in the caudal half of the femoral
neck than in the cranial half. Cartilage had histologic
grades indicating health without significant differences
among lateral, medial, cranial, and caudal halves of
femoral head cartilage.
Conclusions and Clinical Relevance—A predictable
cancellous architecture in the head and neck of the
femur is associated with healthy cartilage. (Am J Vet