Objective—To evaluate a modified digital imaging
technique for quantitative assessment of the grade of
osteoarthritis across the proximal articular surface of
the first phalanx in horses.
Sample Population—6 metacarpophalangeal (fetlock)
joint specimens from 6 horses with various
stages of osteoarthritis.
Procedure—First phalanx specimens, together with 4
gray scale reference calibration targets, were positioned
in a bath with the proximal articular cartilage surface
submerged in saline (0.9% NaCl) solution. Digital
images were obtained from the articular surface before
and after staining with Indian ink. Computer-controlled
gray level analysis of the nonstained and Indian ink-stained
cartilage surfaces and gray scale reference calibration
targets was performed by use of the mean
pixel value (based on 255-gray scale). An increase in
the mean pixel value after staining was used to calculate
the cartilage degeneration index (CDI).
Results—The CDI of the proximal articular cartilage
surface of the first phalanx specimens ranged from
9.2 ± 5.7 (early stage osteoarthritis) to 41.5 ± 3.6%
(late stage osteoarthritis). The effect of repeating the
measurement 6 times in nonstained (including repositioning)
and stained specimens (including repositioning
and restaining) was not significant. Up to 10
measurements of nonstained specimens could be
made without refreshing the bath solution. In stained
specimens, mean gray level increased significantly
after the sixth measurement.
Conclusion and Clinical Relevance—The modified
digital imaging technique allowed quantitative assessment
of cartilage degeneration across the articular
cartilage surface. The CDI is the first quantitative measure
for osteoarthritis-induced cartilage degeneration
over an entire joint surface in horses. (Am J Vet Res
Objective—To assess whether reported alterations in metabolism of cartilage matrix in young (0 to 24 months old) horses with osteochondritis dissecans (OCD) may also be found in older (24 to 48 months old) horses with clinical signs of OCD and to investigate the role of eicosanoids in initiating these clinical signs.
Sample Population—Synovial fluid was collected from 38 tarsocrural joints of 24 warmblood horses with (22 joints of 16 horses) or without (16 joints of 8 horses) clinical signs and a radiographic diagnosis of OCD of the distal intermediate ridge of the tibia.
Procedures—Turnover of type II collagen was investigated by use of specific immunoassays for synthesis (carboxypropeptide of type II collagen [CPII]) and degradation (collagenase-cleaved fragments of type II collagen [C2C]) products. Furthermore, glycosaminoglycan (GAG), leukotriene (LT) B4, cysteinyl LTs, and prostaglandin (PG) E2 concentrations were determined, and concentrations in joints with OCD were compared with those in joints without OCD.
Results—Concentrations of CPII, C2C, and GAG did not differ significantly between affected and nonaffected joints. Fluid from joints with OCD had significantly higher LTB4 and PGE2 concentrations than did fluids from nonaffected joints.
Conclusions and Clinical Relevance—Altered collagen or proteoglycan turnover was not detected in 24- to 48-month-old horses at the time they developed clinical signs of OCD of the distal intermediate ridge of the tibia. However, increased concentrations of LTB4 and PGE2 in fluid of joints with OCD implicate these mediators in the initiation of clinical signs of OCD.
To improve fracture treatment, in vitro experiments were performed to study the influence of a full limb cast and a walking cast on the loading regimen of bones in the distal portion of the equine forelimb.
6 forelimbs of 6 Shetland ponies.
Loading of the third metacarpal bone was considered a representative measure for distal limb loading. Electrical resistance rosette strain gauges were attached to the dorsal, palmar, medial, and lateral surfaces of the midshaft of this bone in 6 forelimbs of 6 Shetland ponies. The limbs were tested in a pneumatic loading device to a maximal load of 1,500 N.
Both casts decreased the amount of compressive forces acting on the metacarpal bone. Application of a full limb cast resulted in a variable and eccentric decrease, remaining strains ranging from 84 to 7% of the baseline value. A walking cast was superior in that it gave a centric and more uniform reduction of compressive loading to <11 % of the baseline value. Moreover, a walking cast neutralized the bending and torsion components of the loading.
This study confirmed the clinical experience that a walking cast creates more reliable and favorable conditions for healing of fractures than does a full limb cast. (Am J Vet Res 1996;57:1386-1389)
Objective—To determine the speed of sound (SOS)
in equine articular cartilage and investigate the influence
of age, site in the joint, and cartilage degeneration
on the SOS.
Sample Population—Cartilage samples from 38
metacarpophalangeal joints of 38 horses (age range,
5 months to 22 years).
Procedure—Osteochondral plugs were collected
from 2 articular sites of the proximal phalanx after the
degenerative state was characterized by use of the
cartilage degeneration index (CDI) technique. The
SOS was calculated (ratio of needle-probe cartilage
thickness to time of flight of the ultrasound pulse),
and relationships between SOS value and age, site,
and cartilage degeneration were evaluated. An analytical
model of cartilage indentation was used to evaluate
the effect of variation in true SOS on the determination
of cartilage thickness and dynamic modulus
with the ultrasound indentation technique.
Results—The mean SOS for all samples was 1,696
± 126 m/s. Age, site, and cartilage degeneration had
no significant influence on the SOS in cartilage. The
analytical model revealed that use of the mean SOS
of 1,696 m/s was associated with maximum errors of
17.5% on cartilage thickness and 7.0% on dynamic
modulus in an SOS range that covered 95% of the
Conclusions and Clinical Relevance—In equine
articular cartilage, use of mean SOS of 1,696 m/s in
ultrasound indentation measurements introduces
some inaccuracy on cartilage thickness determinations,
but the dynamic modulus of cartilage can be
estimated with acceptable accuracy in horses regardless
of age, site in the joint, or stage of cartilage
degeneration. (Am J Vet Res 2005;66:1175–1180)