Periosteal autograft were used for repair of large osteochondral defects in 10 horses aged 2 to 3 years old. In each horse, osteochondral defects measuring 1.0 X 1.0 cm2 were induced bilaterally on the distal articular surface of each radial carpal bone. Control and experimental defects were drilled. Periosteum was harvested from the proximal portion of the tibia and was glued into the principal defects, using a fibrin adhesive. Control defects were glued, but were not grafted. Sixteen weeks after the grafting procedure, the quality of the repair tissue of control and grafted defects was assessed biochemically. Total collagen content and the proportion of type-II collagen were determined. Galactosamine and glucosamine contents also were determined. From these measurements, contents of chondroitin and keratan sulfate and total glycosaminoglycan, and galactosamine-to-glucosamine ratio were calculated. All biochemical variables were compared with those of normal equine articular cartilage taken from the same site in another group of clinically normal horses. Total collagen content was determined on the basis of 4-hydroxyproline content, using a colorimetric method. The proportions of collagen types I and II in the repair tissue were assessed by electrophoresis of their cyanogen bromide-cleaved peptides on sodium dodecyl sulfate slab gels. Peptide ratios were computed and compared with those of standard mixtures of type-I and type-II collagens. Galactosamine and glucosamine contents were determined by use of ion chromatography. In general, the biochemical composition of repair tissue of grafted and nongrafted defects was similar, but clearly differed from that of normal articular cartilage. Total glycosaminoglycan content, galactosamine and glucosamine contents, and galactosamine-to-glucosamine ratio of grafted and nongrafted defects were all significantly (P < 0.05) less than corresponding values in normal equine articular cartilage. By contrast, total collagen content of neocartilaginous tissues of grafted and nongrafted defects was greater than that of normal articular cartilage, although the difference was not significant. The proportion of type-I and type-II collagens in repair tissue in grafted and nongrafted defects was 70 and 30%, respectively. The fibrous nature of the repair tissue reported in a companion morphologic and histochemical study was substantiated by the biochemical results. We concluded that use of periosteal autograft did not improve the healing of osteochondral defects.

The third carpal bone (C3) was collected from both forelimbs of 27 Thoroughbreds. On the basis of age, training, and history, specimens were assigned to 1 of 5 groups: yearling, untrained horses (group 1, n = 4); 2- to 3-year-old, untrained horses (group 2, n = 7); trained 2-year-old horses (group 3, n = 6); trained 3-year-old horses (group 4, n = 6); and 3-year-old, trained horses with carpal pathologic features (group 5, n = 4). A transverse section of subchondral bone 5-mm thick was cut in a precise fashion 10 mm below the proximal articular surface of all specimens. After high-detail radiography was done, indentation testing was performed on the proximal surface of the section at points 5 mm apart. The stiffness of the subchondral cancellous bone was determined from the slope of the load vs displacement curve. Topographic plots of stiffness measurements were compared with radiographs of each specimen. Point determinations were averaged to derive measures for the radial and intermediate facets, and for regions 5, 10, 15, and 20 mm from the dorsal margin of C3. Area fraction (1-p; p = porosity) was measured for the radial and intermediate facets, using an automated image analysis system. Significant (P < 0.05) increases in stiffness and area fraction were found in the C3 from trained horses (groups 3 to 5), compared with untrained horses (groups 1 to 2). Stiffness and area fraction of the radial facet of pathologic C3 were significantly higher than the same variables measured in C. from any other group. A typical profile of regional subchondral stiffness was identified in C3 from normal horses, with maximal stiffness measured 10 mm from the dorsal articular margin. A different pattern was found in pathologic C3, with significantly greater stiffness 15 and 20 mm from the dorsal articular margin when compared with normal horses. A highly significant (P < 0.0001) direct linear correlation between stiffness and area fraction at the radial facet was found. Topographic and radiographic analysis demonstrated good correlation between stiffness and radiographic density of the bone sections. The observed patterns of normal and pathologic C3 were contrasted. In particular, a large gradient in sub-chondral stiffness was identified in pathologic C3 at the dorsomedial aspect of the bone.

The use of periosteal autografts to resurface osteochondral defects was investigated in 10 horses (2 to 3 years old), and the repair tissue was characterized morphologically. Middle carpal joint arthrotomies were made, and osteochondral defects were induced bilaterally on the distal articular surface of each radial carpal bone. Each defect measured approximatively 1 cm2 and extended 3 mm into the subchondral bone plate. Residual subchondral bone plate of control and principal defects was perforated by drilling. A sterile fibrin adhesive was made by mixing a fibrinogen component and a thrombin component. A periosteal autograft was harvested from the proximal portion of the tibia and was glued onto the recipient osseous surface, with its cambium facing the joint cavity. Control defects were glued, but not grafted. Horses were walked 1 hour daily on a walker, starting at postoperative week 7 and continuing for 9 weeks. Sixteen weeks after the grafting procedure was done, carpal radiography was performed, after which horses were euthanatized. Quality of repair tissue of control and grafted defects was evaluated and compared grossly, histologically, and histochemically. Using a reticule, the proportions of various repair tissue types filling each defect were quantitated. Seven weeks after the grafting procedure was done, bilateral arthroscopy revealed synovial adhesions and marginal pannus formation in control and grafted defects. None of the autograft was found floating unattached within the respective middle carpal joints. At 16 weeks, the gross appearance of most grafted and nongrafted defects was similar, and repair was dominated by a fibrous pannus. In 4 grafted defects, bone had formed either concentrically within the defect or eccentrically in the fibrous adhesions between the defect and the joint margin. Histologically, all grafted and nongrafted defects were repaired similarly by infiltration of a mixture of fibrous tissue, fibrocartilage, and bone. Fibrous tissue was the predominant tissue in most defects and its mean proportion was 56 and 59% in the grafted and nongrafted defects, respectively. Fibrocartilaginous tissue in the deeper layers approximated 20%, and woven bone at the base of the defect was 20% in all defects. Histochemically, difference in staining for proteoglycans was not observed between grafted and nongrafted defects. Little remaining original periosteal graft tissue was evident at the defect sites. The only distinguishing feature of grafted defects was the presence of islands of bone formation either at the defect site (n = 2 horses), or in somewhat dorsally displaced tissue that was incorporated in fibrous adhesions (n = 2 horses). It was concluded that use of periosteal autograft did not improve the healing of osteochondral defects of the distal portion of the radial carpal bone. The repair tissue produced in grafted and nongrafted defects was similar and was principally fibrous in nature.

The effects of intra-articular administration of dimethylsulfoxide (DMSO) on chemically induced synovitis in the middle carpal joint of 6 weanling horses were evaluated. Following aseptic collection of synovial fluid, the middle carpal joint of each forelimb was injected with 50 mg of Na-monoiodoacetate to induce synovitis. Eight days after injection, synovial fluid was obtained and the right middle carpal joints were injected with 2 ml of 40% DMSO in lactated Ringer solution. The corresponding joints of the left limb (control) were injected with 2 ml of lactated Ringer solution. Sampling and treatments were repeated on post-injection days 11 and 14, for a total of 3 treatments. Horses were visually evaluated daily for lameness and joint effusion. Synovial fluid was evaluated for color and clarity, differential and total WBC count, total protein content, and hyaluronic acid concentration. The Kaegi gait analysis system provided an objective assessment of lameness prior to inducing synovitis, again on day 7, and on day 17. At necropsy (day 17), synovial fluid, synovial membrane, and articular cartilage specimens were collected. Joint effusion was evident 12 hours after injection ofNa-monoiodoacetate in all joints. Mild lameness was evident at 24 hours; however, the lameness resolved by 72 hours. Objective assessment of lameness did not reveal significant differences between treatment or control limbs. Hyaluronic acid concentrations increased significantly (P = 0.023) above baseline values in most joints over the study period. Synovial fluid WBC counts increased significantly (P = 0.002) following Na-monoiodoacetate injection and remained significantly (P = 0.002) above baseline values throughout the study. There was a significantly greater decrease (P = 0.04) in total WBC counts between the pretreatment and final sampling period in the DMSO-treated joints, compared with the controls. Histologic evaluation of synovial membrane samples revealed a significantly less inflammatory response in 4 of 6 DMSO-treated joints, compared with that in the controls. Histochemical staining of articular cartilage did not reveal any observable difference between treated or control specimens.

The effect of pulsed radio frequency therapy (PRFT) was evaluated on seven ponies with no arthritis and in 28 ponies in which arthritis was created using intra-articular amphotericin B to induce synovitis in the right middle carpal joint. The ponies were divided into five treatment and two control groups. Two levels of arthritis were created and two dosage levels of PRFT were evaluated. The effect of PRFT on arthritic and nonarthritic joints was measured by comparing synovial fluid parameters, the degree and duration of lameness, the range of carpal motion, and carpus circumference, for treated and untreated groups. Lesions seen radiographically at gross pathology, and by histopathology were also compared between the treated and control groups. In the ponies with a mild form of induced arthritis, PRFT significantly (p < 0.05) reduced the severity and duration of lameness, swelling of the carpus, and the severity of gross pathological and radiographic changes. In these ponies the synovial acid phosphatase levels were lower, the mucin clot quality was superior, and the synovial protein levels were lower for the ponies receiving PRFT as compared to the arthritic ponies receiving no treatment. A dose response effect was evident. In ponies with a slightly more severe form of arthritis, PRFT was evaluated at one dosage level. The treated ponies were significantly improved over the untreated ponies with respect to carpal range of motion, degree of lameness, carpus swelling, and radiographic lesions. No deleterious effects were noted when normal, PRFT treated, middle carpal joints were compared to contralateral untreated, normal joints. It was concluded that significant beneficial effects resulted when affected ponies were treated with PRFT.