Biplanar radiography was used to study normal growth of the left and right radius in 5 Beagles and growth of the left radius alone in 15 additional Beagles. We explored the applicability of this radiographic method in veterinary medicine by measuring the contribution to total radius length from each growth plate. Spherical tantalum markers (0.5 mm) were embedded in the proximal epiphysis, diaphysis, and distal epiphysis of each dog's radius at 10 weeks of age. Simultaneous biplanar radiographic views were obtained every 4 weeks until skeletal maturity was documented. A three-dimensional coordinate system was constructed allowing for measurement of growth (in millimeters). Resolution of the measuring system was 0.074 mm. Mean +/- SEM length of the skeletally mature Beagle's radius, as measured from proximal epiphyseal bead to distal epiphyseal bead, was 95.33 +/- 1.07 mm. The percentage of contribution to the total radius length from the proximal and distal growth plates was 36.76 and 64.73%, respectively, with 95% confidence interval of 2.29%. The percentage of contribution to radius length from the distal radial growth plate increased for each consecutive time segment, with the distal radial physis contributing 61.75% from 10 to 14 weeks of age and increasing to 70.22% from 22 to 26 weeks of age. Significant growth was not observed after 26 weeks of age. The period of most rapid growth was between 10 and 14 weeks of age. Biplanar radiography was accurate and precise in quantifying the relative contribution of the proximal and distal growth plate to radius length in Beagles. The method is applicable in veterinary research or clinical medicine for monitoring of axial and angular growth: physiologic, iatrogenic, or pathologic.

Strain gauge rosettes were bonded to the dorsal, lateral, medial, and plantar aspects of the third metatarsal bone in the hind limbs of 6 ponies. The maximal compressive principal strain was approximately -600 X 10(-6) m/m, and exceeded the amplitudes of the tensile strains at all aspects of the bone. After transformation, the shear strain and the principal strains parallel and perpendicular to the bone were obtained. The first peak in the bending strain was higher in the dorsal and lateral aspects, and the second peak was higher in the medial and plantar aspects. Young modulus of elasticity was determined in a 4-point bending test at the dorsal and plantar sides; it averaged 19.5 GPa in tension and compression. Applying linear bending theory, the eccentricity of an axial force parallel or a bending force perpendicular to the bone were calculated. The position where the total force penetrated the tarsometatarsal joint surface was largely within the joint surface, indicating that the joint is merely loaded in (eccentric) compression.

Arthrotomies of middle carpal joints were done on 13 horses, and a 1-cm partial thickness, round defect was made on the radial facet of both third carpal bones. In one joint, 1-mm diameter 1-cm deep holes were drilled within the defect, and one joint was used as a control. Horses were assigned to 2 groups--group 1 (n = 6 horses), 5 drill holes; group 2 (n = 7 horses), 11 drill holes. At 1 and 3 weeks after surgery, differences between joints in synovial fluid total protein values, WBC counts, or results of mucin precipitate tests were not significant (P = 0.005). Physically and radiographically, horses were the same during the 12 initial weeks they were housed in stalls and the 9 weeks they were kept in paddocks. Twenty-one weeks after surgery, horses were euthanatized. Joints with drill holes had a significantly greater area (P less than 0.05) of healthy fibrocartilage new tissue: group 1--33 to 68% new tissue, compared with 0 to 23% new tissue in controls; and group 2--22 to 64% new tissue, compared with 0 to 37% new tissue in controls. Differences between healing of defects with drill holes in groups 1 and 2 were not significant. Thickness of new tissue over drill holes was 33 to 61% of thickness of cartilage adjacent to the defect, and thickness of tissue between drill holes was 11 to 43% (group 1) and 8 to 79% (group 2) of the thickness of cartilage adjacent to the defect. In all defects with drill holes, new tissue in the form of fibrocartilage was detected deep in drill holes, whereas fibrous tissue was observed superficially and adjacent to drill holes.

We evaluated the single-cycle structural properties for axial compression, torsion, and 4-point bending with a central load applied to the caudal or lateral surface of a diaphyseal segment from the normal adult equine humerus, radius, third metacarpal bone, femur, tibia, and third metatarsal bone. Stiffness values were determined from load-deformation curves for each bone and test mode. Compressive stiffness ranged from a low of 2,690 N/mm for the humerus to a high of 5,670 N/mm for the femur. Torsional stiffness ranged from 558 N.m/rad for the third metacarpal bone to 2,080 N.m/rad for the femur. Nondestructive 4-point bending stiffness ranged from 3,540 N.m/rad for the radius to 11,500 N.m/rad for the third metatarsal bone. For the humerus, radius, and tibia, there was no significant difference in stiffness between having the central load applied to the caudal or lateral surface. For the third metacarpal and metatarsal bones, stiffness was significantly (P < 0.05) greater with the central load applied to the lateral surface than the palmar or plantar surface. For the femur, bones were significantly (P < 0.05) stiffer with the central load applied to the caudal surface than the lateral surface. Four-point bending to failure load-deformation curves had a bilinear pattern in some instances, consisting of a linear region at lower bending moments that corresponded to stiffness values from the nondestructive tests and a second linear region at higher bending moments that had greater stiffness values. Stiffness values from the second linear region ranged from 4,420 N.m/rad for the humerus to 13,000 N.m/rad for the third metatarsal bone. Differences in stiffness between nondestructive tests and the second linear region of destructive tests were significant (P < 0.05) for the radius, third metacarpal bone, and third metatarsal bone. Difference between stiffness values of paired left and right bones was not detected for any test.

Keratan sulfate (KS) is a glycosaminoglycan, distribution of which is confined mostly to hyaline cartilage. As such, it is a putative marker of hyaline cartilage catabolism. In experiment 1, a focal osteochondral defect was made arthroscopically in 1 radial carpal bone of 2 ponies, and in 2 other ponies, chymopapain was injected into the radiocarpal joint to induce cartilage catabolism. Sequential and concurrent plasma and synovial fluid concentrations of KS were measured, up to 13 months after induction of cartilage injury, to determine whether changes in KS concentrations reflected cartilage catabolism. In experiment 2, a large, bilateral osteochondral defect was made in the radial carpal bones of 18 ponies, which were subsequently given postoperative exercise and/or injected intra-articularly with 250 mg of polysulfated glycosaminoglycan (PSGAG). Medication was given at surgery, then weekly for 4 weeks. Blood samples were collected and synovial fluid was aspirated before surgery, when medication was given, and at postmortem examination (postoperative week 17). The KS concentration was measured in these fluids to determine whether changes in KS concentration indicated an effect of joint treatment. In experiment 1, the concentration of KS in synovial fluid was highest 1 day after joint injury, and the concentration in plasma peaked 2 days after joint injury. For ponies receiving chymopapain intra-articularly (generalized cartilage catabolism), a fivefold increase over baseline was observed in the concentration of KS in plasma (peak mean, 1.2 microgram/ml), and a tenfold increase over baseline in synovial fluid (peak mean, 2.0 mg/ml) was observed. On average, these maxima were threefold higher than values in fluids of ponies with osteochondral defects (focal cartilage disease). In experiment 2, nonexercised ponies had lower KS concentration (as a percentage of the preoperative concentration) in synovial fluid than did exercised ponies at all postoperative times, and.

Sonographic observations were made of the image mean gray scale (MGS) of the flexor tendons and ligaments in the left and right metacarpal regions of each of 10 clinically normal horses. In images made in the dorsal and sagittal planes, the MGS was measured at multiple sites in the superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), accessory ligament (AL), and suspensory ligament (SL), and at single sites in the medial and lateral limbs of the SL, and the palmar ligament. Relative sonographic brightness of each tendon and ligament was calculated by dividing the value of its MGS by the mean value for the MGS of images of 3 soft tissue equivalent phantoms. When a multivariate repeated-measures of ANOVA of the relative brightness values was statistically significant (P < 0.05), Tukey's method of multiple comparisons was used to determine which values were significantly different from each other. In the dorsal plane, the SL was significantly brighter than the DDFT, SDFT, and AL; relative brightnesses of the DDFT and SDFT were similar, as were those of the SDFT and AL. In the sagittal plane, the SL again was the significantly brightest structure, followed by the Al, and similar brightnesses of the DDFT and SDFT. In dorsal images made 25 cm distal to the accessory carpal bone, relative brightnesses of the SDFT, DDFT, and the medial and lateral limbs of the SL were similar. In images made 30 cm distal to the accessory carpal bone, relative brightness of the palmar ligament was significantly (P < 0.05) less than that of the SDFT and DDFT in the dorsal plane, but not in the sagittal plane, where it was significantly greater. Relative brightness values represented a unique sonographic characteristic of each structure and, in the future, may provide further insights into tendon and ligament structure and function.

Cortical bone screws were implanted into the proximal portion of the right and left radius and ulna of 6 newborn Quarter Horse foals as radiographic markers for measurement of growth. Distance between markers on a lateral radiographic view was measured. Radiographs were taken at 2-week intervals until the horses were 8 weeks old, at 4-week intervals until they were 48 weeks old, and at 12-week intervals until they were 72 weeks old. The proximal radius and ulna grew at similar rates during the 72-week period of evaluation, and growth continued throughout 72 weeks. The proximal radius grew 3.5 cm, and the ulna grew 3.4 cm. Although the rates of growth were similar, growth from the ulnar physis contributed only to the length of the olecranon; growth was not transmitted to the ulnar diaphysis distal to the cubital joint. The proximal radius slid distally in relation to the ulna as growth occurred at the proximal radial physis. These findings suggest that transfixing the ulna to the radius while growth is occurring at the proximal radial physis impedes the natural shifting process, and subluxation of the elbow can result. Severity of subluxation would be inversely related to the age of the horse at the time of transfixation.