Relationship between synovial fluid levels of glycosaminoglycans, hydroxyproline and general MMP activity and the presence and severity of articular cartilage change on the proximal articular surface of P1

REASONS FOR PERFORMING STUDY: Osteoarthritis (OA) is one of the most prevalent and disabling chronic conditions affecting horses and leads to degeneration of articular cartilage. Diagnosis is based on clinical signs in combination with radiography, which is relatively insensitive and provides only an indication of accumulated damage. Alternative methods, such as molecular markers, are therefore needed that can quantitatively, reliably and sensitively detect osteoarthritic changes in the joints at an early stage of the disease. If such markers are to be used reliably, it is important to know the relationship between marker concentration and cartilage composition. OBJECTIVES: To study the relationship between cartilage composition, synovial fluid levels of glycosaminoglycans (GAGs), hydroxyproline (Hyp) and general matrix metalloproteinase (MMP) activity, and the presence and severity of articular cartilage damage on the articular surface of P1. METHODS: Synovial fluid (SF) was collected from the metacarpophalangeal joints of 60 mature horses, and levels of GAGs, Hyp and general MMP activity were determined. Further, GAG and denatured collagen content of the articular cartilage were determined at the dorsal articular margin of P1 (site 1) and central cavity (site 2). The presence and severity of cartilage change was quantified using the cartilage degeneration index (CDI), measured at the same 2 sites. Correlations between SF parameters, cartilage composition and degree of cartilage degeneration were sought using correlation analysis. RESULTS: There was no correlation between GAG or Hyp content of SF and the amount of GAGs or denatured collagen, respectively, in cartilage. In joints with moderate to severe cartilage damage, the GAG content of site 1 was significantly lower than in joints with no to minimal cartilage change (P = 0.005) and there was a negative correlation between the amount of denatured collagen and GAG content at site 1 in all joints (r = -039, P = 0.002). Further, in joints with moderate to severe cartilage damage, there was a significant positive correlation between MMP activity in SF and Hyp levels in SF (r = 0.72, P < 0.001) and CDI at sites 1 (r = 0.46, P = 0.03) and 2 (r = 0.43, P = 0.04). CONCLUSIONS: General MMP activity in joints with moderate to severe cartilage damage is related to the severity of those cartilage changes and to Hyp levels in SF. Glycosaminoglycan levels in SF are not directly related to MMP activity, GAG content of articular cartilage or severity of cartilage change. POTENTIAL RELEVANCE: Glycosaminoglycan levels in SF are not helpful for the early detection of cartilage lesions. In damaged joints, Hyp levels may give an indication of the severity of cartilage change as they are strongly related to MMP activity, but do not qualify as markers for the presence or absence of cartilage lesions.     

Functional consequences of cartilage degeneration in the equine metacarpophalangeal joint: quantitative assessment of cartilage stiffness

REASONS FOR PERFORMING STUDY: No quantitative data currently exist on the relationship of the occurrence of cartilage degeneration and changes in site-specific biomechanical properties in the metacarpophalangeal (MCP) joint in the horse. OBJECTIVES: To gain insight into the biomechanical consequences of cartilage deterioration at 2 differently loaded sites on the proximal articular surface of the proximal phalanx (P1). HYPOTHESIS: Static and dynamic stiffness of articular cartilage decreases significantly in degenerated cartilage. METHODS: Cartilage degeneration index (CDI) values were measured at the lateral dorsal margin (Site 1), lateral central fovea (Site 2) and entire joint surface of P1 (CDIP1) in 30 horses. Group 1 contained joints without (CDIP1 values <25 %, n = 22) and Group 2 joints with (CDIP1 values >25 %, n = 8) signs of cartilage degeneration. Cartilage thickness at Sites 1 and 2 was measured using ultrasonic and needle-probe techniques. Osteochondral plugs were drilled out from Sites 1 and 2 and subsequently tested biomechanically in indentation geometry. Young's modulus at equilibrium and dynamic modulus were determined. RESULTS: Cartilage thickness values were not significantly different between the 2 groups and sites. Young's modulus at Site 1 was significantly higher in Group 1 than in Group 2; at Site 2, the difference was not significant. Dynamic modulus values were significantly higher in Group 1 than in Group 2 at both sites. CONCLUSIONS: Degenerative cartilage changes are clearly related to loss of stiffness of the tissue. Absolute changes in cartilage integrity in terms of CDI are greatest at the joint margin, but concomitant changes are also present at the centre, with a comparable decrease of the biomechanical moduli at the 2 sites. Therefore, significant cartilage degradation at the joint margin not only reflects local deterioration of biomechanical properties, but is also indicative of the functional quality in the centre. POTENTIAL RELEVANCE: These findings may be important for improving prognostication and developing preventative measures.     

The Intercarpal Ligaments of the Equine Midcarpal Joint, Part 3: Clinical Observations in 32 Racing Horses With Midcarpal Joint Disease

Objective— To characterize the clinical features of intercarpal ligament pathology and to determine the relationship among palmar intercarpal ligament tearing, dorsomedial intercarpal ligament (DMICL) hypertrophy, and other intraarticular lesions.
Study Design— Prospective clinical observations.
Animals or Sample Population— Twenty-eight thoroughbred and four standardbred race horses.
Methods— Clinical, radiographic, and arthroscopic examination of 53 midcarpal joints of 32 horses.
Results— Palmar intercarpal ligament tearing was observed in 30 joints of 22 horses. Some tearing of the medial palmar intercarpal ligament (MPICL) was present in 27 joints of 20 horses, and tearing of the lateral palmar intercarpal ligament in 9 joints of 7 horses. There was no correlation between the severity of clinical signs recorded and the degree of MPICL tearing. Joints with grade 2–4 MPICL tearing had significantly less cartilage and bone damage than joints with grade 1 or no ligament damage ( P <.05). There was a significant inverse relationship between the number and size of intra-articular fractures, as assessed radiographically, and ligament damage ( R = -.31). The DMICL was identified in all joints, and in 18 joints the ligament was enlarged. There was a significant correlation between MPICL damage and hypertrophy of the DMICL ( R =.35). There was no correlation between DMICL hypertrophy and articular cartilage damage or subchondral bone damage.
Conclusions— Severe subchondral bone and MPICL damage rarely occur in the same joint and DMICL hypertrophy may be associated with, rather than a cause of, joint disease.
Clinical Relevance— There are no clinical or radiographic findings that will differentiate intercarpal ligament injury from other carpal injuries. Diagnosis is only possible by arthroscopic examination of the midcarpal joint.     

Measurement of articular cartilage stiffness of the femoropatellar, tarsocrural, and metatarsophalangeal joints in horses and comparison with biochemical data

OBJECTIVE: To determine normal cartilage stiffness values in different weight-bearing and non-weight-bearing areas of 3 different equine joints, and to evaluate the relationship between cartilage stiffness and glycosaminoglycan (GAG) and collagen content. STUDY DESIGN: Compressive stiffness of the articular cartilage was measured in 8 horse cadaver femoropatellar (FP), tarsocrural (TC), and metatarsophalangeal (MT) joints. Gross evaluation, collagen content, GAG content, and histologic appearance were assessed for each measurement location. ANIMALS: Eight equine cadavers (4 intact females, 4 castrated males; 7 Quarter Horse or Quarter Horse type, 1 Arabian; aged 4-12 years, weighing 400-550 kg). METHODS: The articular surfaces of 8 equine cadaver FP, TC, and MT joints were grossly evaluated for signs of articular cartilage pathology. Stiffness at preselected sites (FP joint-6 sites; TC joint-3 sites; MT joint-4 sites) was determined using an arthroscopic indentation instrument. Biochemical composition (collagen, GAG content) and histologic evaluation (modified Mankin score) were assessed for each measurement site. RESULTS: All cartilage from all sites evaluated was determined to be normal based on macroscopic and histologic assessments. No significant correlation between Mankin scores and cartilage stiffness values was observed. Site differences in cartilage stiffness were measured in all 3 joints (P<.001). GAG or collagen content had a significant positive correlation with stiffness values in 6 of 13 sites (P<.05, r>0.622, r2>0.387). CONCLUSION: Relative cartilage stiffness values measured in healthy equine joints are site dependent and can be measured using an indentation device intended for arthroscopic application. CLINICAL RELEVANCE: An indentation instrument provided an objective means of determining relative compressive stiffness of articular cartilage. Further research needs to be performed to confirm the site and joint differences observed in this study in clinically normal horses and to determine if the tester can be used clinically to predict articular cartilage pathology.     

The incidence and severity of intercarpal ligament damage in the equine carpus

SUMMARY The arthroscopic findings in 104 intercarpal joints in 76 horses were reviewed to determine the incidence and severity of changes in the medial intercarpal ligament. Damage to the intercarpal ligament was observed in 43 joints in 35 horses, ranging from mild fraying of the edges of the ligament to complete disruption of all fibres. This represented an incidence of 41% of joints being affected. In 9 joints examined arthroscopically primarily as a further diagnostic procedure, ligament damage was evident in all cases. In horses undergoing arthroscopic surgery primarily for the treatment of osteochondral chip or slab fractures, there was some correlation between the severity of articular cartilage damage and the presence of ligament damage.     

Evaluation of a Collagenase Generated Osteoarthritis Biomarker in the Synovial Fluid from Elbow Joints of Dogs with Medial Coronoid Disease and Unaffected Dogs

Objective— To evaluate whether synovial fluid concentrations of an osteoarthritis biomarker in dysplastic canine elbows with medial coronoid disease (MCD) are elevated compared with unaffected elbows and to determine if these concentrations correlate to the degree of articular cartilage damage.
Study Design— Cross sectional clinical study.
Animals— Dogs (n=19; 35 elbows) with MCD and dogs (8; 16 elbows) with unaffected elbows.
Methods— Concentrations of a collagenase-generated cleavage neoepitope of type II collagen (Col2-3/4C_{long mono}, or C2C) in joint fluid from elbows were analyzed and compared between dogs with MCD and unaffected dogs. Correlation of C2C concentration with subjective grading of articular cartilage surface damage was also evaluated.
Results— Mean (±SD) C2C concentration from MCD dogs was significantly higher (112.3±24.8 ng/mL) than in unaffected dogs (76.1±16.9 ng/mL; P <.05). There was a moderate correlation between cartilage damage grade and increasing C2C concentrations ( P <.05, r=0.62)
Conclusion— C2C concentrations are elevated in the synovial fluid of dogs with MCD compared with unaffected elbows, and a moderate, significant correlation was identified between these concentrations and subjective grading of articular cartilage damage.
Clinical Relevance— This preliminary data suggest that C2C concentrations in synovial fluid may have potential as a biomarker for diagnosis of articular cartilage damage associated with MCD and as a means of objectively determining the degree of articular cartilage damage.     

Comparison of arthroscopic and radiographic abnormalities in the hip joints of juvenile dogs with hip dysplasia

OBJECTIVE: To compare radiographic and arthroscopic abnormalities in juvenile dogs with clinically apparent hip dysplasia. DESIGN: Case series. ANIMALS: 52 dogs (70 hip joints) with clinical signs of hip dysplasia scheduled to undergo triple pelvic osteotomy. PROCEDURE: A ventrodorsal radiographic projection of the pelvis was evaluated by a radiologist unaware of clinical and arthroscopic findings, and radiographic osteoarthritic abnormalities were judged and scored as absent (0), mild (1), moderate (2), or severe (3). Arthroscopy was performed by a surgeon unaware of clinical and radiographic findings, and arthroscopic abnormalities were graded from 0 (normal) to 5 (exposed, eburnated subchondral bone). RESULTS: In 30 of the 70 (43%) hip joints, no radiographic osteoarthritic abnormalities were seen. Severe, full-thickness articular cartilage lesions (grade 4) of the femoral head or acetabulum were seen arthroscopically in 14 (20%) joints. Lesions > or = grade 2 were seen in 60 (86%) joints. Partial tearing of the ligament of the femoral head was present in 57 (81%) joints, and complete rupture was seen in 5 (7%). Radiographic abnormalities were seen in 13 of the 14 (93%; 95% confidence interval, 66% to 99.8%) joints with grade 4 arthroscopic abnormalities but in only 23 of the 46 (50%; 95% confidence interval, 35% to 65%) joints with grade 2 or 3 arthroscopic abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that radiography is not a sensitive method for identifying moderate cartilage lesions in juvenile dogs with hip dysplasia. If moderate cartilage lesions are an important prognostic indicator for the success of triple pelvic osteotomy, then methods other than radiography should be used to detect these lesions.     

Differences in the topographical distribution of articular cartilage degeneration between equine metacarpo- and metatarsophalangeal joints

REASONS FOR PERFORMING STUDY: The equine metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints, although having virtually the same geometrical appearance, differ in the prevalence of joint pathologies, such as osteochondral fragmentation, and in biomechanical behaviour. The recently developed cartilage degeneration index (CDI) technique offers a possibility to assess quantitatively differences in cartilage degeneration between these joints and to compare these with known differences in biomechanics and clinical observations. OBJECTIVES: To compare the topographical distribution of articular cartilage degeneration across the proximal articular surface of the proximal phalanx (P1) in the equine fore- and hindlimb. METHODS: In 24 distal hindlimbs from 24 horses, articular cartilage degeneration of the proximal articular surface of P1 was quantified using the CDI. Overall CDI value (CDI(P1)) and CDI values of 6 areas of interest were determined: the medial dorsal surface (mds), lateral dorsal surface (lds), medial central fovea (mcf), lateral central fovea (lcf), medial plantar surface (mps) and lateral plantar surface (lps). The joints were divided into 4 equally sized groups of increasing CDI(P1) values. From an existing CDI database of MCP joints, 24 joints were selected with matching CDI(P1) values to the MTP joints and CDI values for the same areas of interest were determined. RESULTS: In both the MCP and MTP joints, highest CDI values were determined at the dorsal articular surfaces. Values were not significantly different between fore- and hindlimbs. In contrast to the MCP joint, CDI values at the plantar joint margin were significantly higher compared to CDI values in the central sites in the MTP joint. CDI values for the plantar surfaces of P1 were significantly higher than those for the palmar surfaces in the forelimb in joints with advanced stages of OA; and values for the central regions of P1 were significantly lower in the hindlimb compared with the forelimb in joints with severe OA. CONCLUSIONS: In both fore- and hindlimbs, initial cartilage degeneration started at the dorsal articular margin of P1. There was a major difference in the spread of cartilage degeneration; in the forelimb both the central and palmar parts are about equally involved, whereas in the hindlimb the plantar parts were significantly more and the central parts significantly less involved. These differences can be linked to differences in biomechanical loading reported elsewhere. POTENTIAL RELEVANCE: This study supports the hypothesis that differences in biokinematics between fore- and hindlimbs are associated with differences in the development of cartilage degeneration and other joint pathologies such as osteochondral fragmentation in the MCP and MTP joints. This information is indispensable for a better understanding of the dynamic nature and progression of these joint disorders and may be of help when monitoring the effects of therapeutic interventions and preventative measures.     

COMPARISON OF THE ULTRASONOGRAPHIC APPEARANCE OF OSTEOCHONDROSIS LESIONS IN THE CANINE SHOULDER WITH RADIOGRAPHY, ARTHROGRAPHY, AND ARTHROSCOPY

Osteochondrosis lesions in 29 shoulder joints (from 20 dogs) were evaluated with ultrasound (US) and the results were compared with survey radiography, arthrography, and arthroscopy. US was performed with a 7-12 MHz linear matrix transducer which was placed in cranio-caudal direction just distally to the acromion while the joint was adducted and maximally endorotated to visualize the caudal aspect of the humeral head. With US, the subchondral defect was completely visible in 21 joints and partially visible in 8 joints. The length of the subchondral defect measured on US was comparable with the length measured on survey radiographs. In two joints, the cartilage flap was mineralized and thus already visible on survey radiographs. The mineralized flap was visible on US as a straight hyperechoic line above the subchondral defect. In the other joints, survey radiographs could not assess the status of the articular cartilage. In 17 joints, the presence of a cartilage flap or cartilage fissuring was suspected based on the presence of a second hyperechoic line at the base of the subchondral defect, and this suspicion was confirmed by arthroscopic examination in 16 joints and also by arthrographic examination in 15 joints. One joint that was suspected of having a cartilage flap on US was normal on arthroscopy and arthrography. When US revealed only focal thickening of the anechoic cartilage layer (5 joints), the joints appeared normal on arthroscopic and arthrographic examination. Of the four joints where the subchondral defect was irregular and covered by heteroechogeneous material on US, arthroseopy revealed the presence of a lesion resembling chondromalacia in two joints, the presence of a small cartilage flap in one joint and the presence of scar tissue underneath the flap at the level of the subchondral defect in one joint. In conclusion, US is a helpful imaging modality in the identification of osteochondritic lesions in the canine shoulder joint. US also appears to be a satisfactory imaging tool for identifying lesions such as joint mice, joint effusion, and distinct new bone formation.     

Arthroscopic Surgery for the Treatment of Osteochondritis Dissecans in the Equine Femoropatellar Joint

Forty limbs with femoropatellar osteochondritis dissecans in 24 horses were treated with arthroscopic surgery. Lesions were bilateral in 16 horses and unilateral in eight horses. Diagnostic examination and surgical treatment were performed through a single arthroscopic portal; five different instrument portal locations and six instrument approaches were used. Lesions were localized to the lateral trochlear ridge of the femur in 31 affected joints, medial trochlear ridge in two joints, lateral and medial trochlear ridges together in two joints, lateral trochlear ridge plus patella in four joints, and patella alone in one joint. The lesions consisted of subchondral defects containing chondral or osteochondral flaps or fragments, or were seen as dimpling, cracking, fibrillation, or erosion of articular cartilage, or intact cartilage over a subchondral defect. Loose bodies were found in three joints. There was a poor correlation between radiologic and arthroscopic findings. Surgical manipulations included removal of flaps, fragments, and undermined articular cartilage, and debridement of the subchondral defect. Three horses were euthanized: one electively to assess the joint grossly, one because of complications following surgery and salmonellosis, and one because of unrelated forelimb abnormalities. Immediate clinical improvement after surgery was seen in the 22 horses permitted to survive. Long-term follow-up on seven of 10 racehorses revealed that two have raced successfully, two are "ready to race," three are training sound, two are sound at pasture (still in convalescence), and one has been reoperated. Of six horses used for show or pleasure, three are being shown sound, one is sound for pleasure, and two are training sound. The remaining horses are convalescing.     

Quantification and age-related distribution of articular cartilage degeneration in the equine fetlock joint

REASONS FOR PERFORMING STUDY: The equine fetlock joint has the largest number of traumatic and degenerative lesions of all joints of the appendicular skeleton. OBJECTIVE: To gain insight into the distribution of cartilage degeneration across the articular surface in relation to age in order better to understand the dynamic nature and progression of osteoarthritis (OA). HYPOTHESIS: That there would be a specific age-related distribution pattern of cartilage degeneration in the equine metacarpophalangeal joint. METHODS: The proximal articular cartilage surfaces of the first phalanges (P1) of 73 slaughter horses (age range 0.4-23 years) with different stages of osteoarthritis were scored semiquantitatively on a 0 to 5 scale and also assessed quantitatively using the cartilage degeneration index (CDI(P1)), which ranges from 0 to 100%. Furthermore, CDI values were determined for special areas of interest; medial dorsal surface (CDI(mds)), lateral dorsal surface (CDI(lds)), medial central fovea (CDI(mcf)) and lateral central fovea (CDI(lcf)). Correlations were calculated for CDI(P1) values and CDI values at the specific areas of interest with macroscopic scores and with age. RESULTS: There was a high correlation between the semiquantitative macroscopic score and the quantitative CDI(P1) values (r = 0.92; P < 0.001). A macroscopic score of 0 (i.e. no obvious cartilage degeneration) corresponded with a CDI(P1) mean +/- s.e. value of 25 +/- 2.8% and a macroscopic score of 5 (i.e. severe cartilage degeneration in localised areas) with a mean +/- s.e. value of 38.1 +/- 7.9%. There was a moderate but highly significant correlation between the CDI(P1) value and the age of the horses (r = 0.41; P < 0.001). Highest CDI values were calculated for the medial dorsal surface (from 10.6 +/- 2.8% at macroscopic Grade 0 to 63.1 +/- 8.4% at Grade 5). At the lateral dorsal surface, these values were 5.9 +/- 1.4% and 47.2 +/- 10.4%, respectively. The CDI(mcf) and CDI(lcf) were significantly lower (P < 0.05) than the CDI(mds) and CDI(lds) at all grades. The CDI(mcf) ranged from 1.0 +/- 2.9% at Grade 0 to 43.7 +/- 9.1% at Grade 5; laterally, these values were 1.5 +/- 2.6% and 15.2 +/- 6.2%, respectively. CONCLUSIONS: CDI grading increased from lateral to medial and from central to dorsal. This specific distribution pattern confirms the heterogeneous nature of the OA process and strongly supports an important role for biomechanical loading, superimposed on age-related changes, in the spread of the disorder over the joint. POTENTIAL RELEVANCE: Knowledge of the development of OA across the articular surface is essential for understanding the dynamic nature and progression of the disease and can form a basis for improvements in diagnostic and therapeutic approaches to degenerative joint disease.     

Arthroscopic Approach and Intra-articular Anatomy of the Palmaroproximal or Plantaroproximal Aspect of Distal Interphalangeal Joints

An arthroscopic approach to the palmaroproximal or plantaroproximal pouch of the distal interphalangeal joint was developed in six cadaver limbs and seven limbs of three clinically normal horses. The dorsal aspect of the proximal border and the proximal articular margin of the distal sesamoid (navicular) bone, the palmar aspect of the distal articular margin of the middle phalanx, the collateral sesamoidean ligaments of the distal sesamoid bone, and the joint capsule attachments were readily accessible. Distending the joints with fluid gave access to portions of the articular surface between the distal sesamoid bone and the middle phalanx in all joints, and to a small portion of the distal phalanx in two hind distal interphalangeal joints. Two horses allowed to recover from anesthesia were not lame on days 30 and 37, respectively. Problems encountered initially were difficulty entering the joint, hemarthrosis, and minimal iatrogenic cartilage damage.     

Evaluation of intra-articularly administered sodium monoiodoacetate-induced chemical injury to articular cartilage of horses.

Three doses of sodium monoiodoacetate (MIA) were used to induce degenerative changes in articular cartilage in middle carpal joints of horses. Twelve young (2- to 5-year-old) horses, free of lameness, were randomly allotted to 3 groups. One middle carpal joint of each horse was injected with 0.9% NaCl solution (control joint). The contralateral middle carpal joint was injected with 0.09 mg of MIA/kg of body weight (group 1); 0.12 mg/kg (group 2); or 0.16 mg/kg (group 3). After MIA administration, horses were allowed ad libitum exercise in a 2-acre paddock for 12 weeks. At the end of the study, gross and microscopic tissue changes were evaluated and biochemical analyses of articular cartilage were done. Grossly, diffuse partial-thickness articular cartilage lesions were observed in group-2 (n = 2) and group-3 (n = 4) horses, but not in group-1 horses. Articular cartilage uronic acid content was significantly (P less than 0.03) decreased in all MIA-injected joints, compared with controls. Articular cartilage matrix staining with safranin-O was decreased in 3 of 4 MIA-injected joints of group-1 horses and in all MIA-injected joints of group-2 and group-3 horses, compared with controls (P less than 0.06). Microscopic degenerative changes in articular cartilage were not significantly different between MIA-injected and control joints in group-1 horses, but were increased (P less than 0.06) in all MIA-injected joints of group-2 and group-3 horses, compared with controls. Qualitatively, decreased matrix staining and degenerative changes were more severe in group-3 horses. On the basis of articular cartilage gross and microscopic changes, as well as biochemical changes, 0.12 mg of MIA/kg injected intra-articularly was determined to induce moderate degrees of articular cartilage degeneration. This model of chemically induced articular cartilage injury could be useful for evaluating treatment effects of anti-arthritic drugs in horses.     

Fate and effect of autogenous osteochondral fragments implanted in the middle carpal joint of horses.

Four autogenous osteochondral fragments removed from the lateral trochlear ridge of the talus were arthroscopically placed as loose bodies in a randomly selected middle carpal joint in each of 10 horses. The contralateral middle carpal joint, subjected to a sham procedure, served as control. Postoperative treatment was consistent with that for clinical arthroscopic patients. Lameness evaluation, radiographic examination, carpal circumference measurement, and synovial fluid analysis were performed before and at scheduled intervals after surgery. After a 2-month confinement, horses were subjected to an increasing level of exercise. Horses were euthanatized at intervals through 6 months. Gross and microscopic evaluations were performed on remaining fragments, articular cartilage, and synovial membrane of each middle carpal joint. Increased joint circumference, effusion, lameness, and degenerative joint disease distinguished implanted from control joints over the 6-month period. Implanted joints were characterized by grooved, excoriated cartilage surfaces, and synovium that was thick, erythematous, and irregular. At 4 weeks, implants were found to have adhered to synovium at their subchondral bone surface. The bone within fragments was undergoing necrosis, while cartilage was preserved. At 8 weeks, fragments were radiographically inapparent, grossly evident as pale plaques on the synovial surface, and composed of dense fibrous connective tissue. Synovial membrane specimens from implanted joints had inflammatory change characterized by mononuclear cell infiltration 2 months after implantation. Physical damage was apparent within articular cartilage of implanted joints at 2 months, and was significant (P less than 0.05) at 6 months after surgery. Chondrocyte degenerative change was significant (P less than 0.05) at 6 months after surgery. Focal reduction in safranin-O uptake was observed in cartilage layers adjacent to physical defects. Osteochondral loose bodies of the size implanted in the middle carpal joint of horses in this study were resorbed by the synovium within 2 months. Synovitis and significant articular cartilage damage were associated with the implanted fragments. Regardless of origin, free osteochondral fragments within the middle carpal joint should be removed, and methods to prevent residual postoperative debris should be implemented to reduce potential for articular pathologic change.     

Accuracy of Arthroscopic Identification of Equine Carpal Lesions

The equine carpal joint was used to evaluate arthroscopic diagnosis of lesions created in joints obtained from horses euthanized for reasons other than lameness. Full-thickness articular defects were made in 13 sites within the antebrachiocarpal joint and middle carpal joint approximating those found in diseased carpal joints. Arthroscopic evaluation of the lesions included location, depth, and size of the defects. The joints were subsequently examined grossly. Results showed that, when compared to gross evaluation, arthroscopy is capable of accurately identifying subtle changes in articular cartilage and bone. A statistically significant increase in error rate was found for lesions at the medial aspect of the proximal radial carpal bone. Other sites with limited arthroscopic access were the proximal ulnar carpal bone, the proximal fourth carpal bone, and the distal intermediate carpal bone. The accuracy of arthroscopic identification of lesions improved significantly during the study as experience with the technique was gained.     

Changes in Third Carpal Bone Articular Cartilage After Synovectomy in Normal and Inflamed Joints

Objective —To determine if arthroscopic synovectomy in normal and inflamed joints had temporal or site-related effects on articular cartilage.
Study Design —Alterations in equine third carpal bone articular cartilage were studied at two time periods: groups 1 and 2 (6 weeks) and groups 3 and 4 (2 weeks) after synovectomy in normal (groups 2 and 4) and inflamed carpi (groups 1 and 3).
Animal Population —16 carpi from eight horses.
Methods —Biochemical and biomechanical properties of dorsal and palmar articular cartilage were determined by radiolabeling, proteoglycan (PG) extraction, chromatography, electrophoresis, and indentation testing.
Results —Synovectomy in inflamed joints produced the greatest concentration of newly synthesized PG in articular cartilage by 2 weeks. Synovectomy in normal joints produced significantly greater newly synthesized PG in articular cartilage by 6 weeks. Endogenous PG was only significantly greater in inflamed joints after 6 weeks. Dorsal sites had greater newly synthesized and endogenous PG in some groups. Chromatographic profiles of newly synthesized PG demonstrated early and late PG peaks. Electrophoresis of late PG peak showed a toluidine blue-positive band that comigrated with human A1D1 PG monomer in the two groups with the most newly synthesized PG. This band was reactive with monoclonal antibody 1C6 specific for the hyaluronic acid-binding region of aggrecan. For the material properties evaluated, only Poisson's ratio was significantly decreased between groups as a function of time (6 weeks < 2 weeks), and this was most pronounced in the thicker dorsal sites.
Conclusions —Synovectomy in inflamed joints produced site-specific, significantly greater responses in articular cartilage as compared with synovectomy in normal joints.
Clinical Relevance —Synovectomy may not be beneficial to the articular cartilage in inflamed joints.     

Meniscal Release in Cruciate Ligament Intact Stifles Causes Lameness and Medial Compartment Cartilage Pathology in Dogs 12 Weeks Postoperatively

Objective— To evaluate after 12 weeks the effects of caudal medial meniscal release (MR) in the cranial cruciate ligament-intact canine stifle.
Study Design— Blinded, prospective in vivo study.
Animals— Purpose-bred hound dogs (n=10).
Methods— Either MR (n=5) or a sham (SH) surgery (n=5) was performed via arthroscopy. Orthopedic examination and subjective lameness evaluation were performed in each dog preoperatively and at 4, 8, and 12 weeks after surgery. Twelve weeks postoperatively, ultrasonographic, radiographic, and arthroscopic examinations were performed on the operated stifles. Gross pathology of the articular cartilage, cruciate ligaments, and menisci was assessed. India ink staining of the femoral and tibial articular surfaces was performed to determine the percent area of articular cartilage damage.
Results— At 8 and 12 weeks after surgery, MR dogs were lamer than SH dogs. At 12 weeks, the degree of radiographic OA was significantly higher in MR stifles than in SH stifles. Gross and sonographic meniscal pathology was more severe in MR stifles compared with SH stifles. MR stifles had significantly more severe articular cartilage pathology compared with SH stifles 12 weeks after surgery; pathology was most severe in the medial compartment.
Conclusions— MR alone is associated with articular cartilage loss, further meniscal pathology, degenerative joint disease, and lameness.
Clinical Relevance— Subsequent osteoarthritis and dysfunction of the stifle joint should be considered when making clinical decisions regarding MR in dogs.     

Influence of site and age on biochemical characteristics of the collagen network of equine articular cartilage

OBJECTIVE: To determine variations in biochemical characteristics of equine articular cartilage in relation to age and the degree of predisposition for osteochondral disease at a specific site. SAMPLE POPULATION: Articular cartilage specimens from 53 horses 4 to 30 years old. PROCEDURE: Healthy specimens were obtained from 2 locations on the proximal articular surface of the first phalanx that had different disease prevalences (site 1 at the mediodorsal margin and site 2 at the center of the medial cavity). Water, total collagen, and hydroxylysine contents and enzymatic (hydroxylysylpyridinoline [HP]) and nonenzymatic (pentosidine) crosslinking were determined at both sites. Differences between sites were analyzed by ANOVA (factors, site, and age), and age correlation was tested by Pearson's product-moment correlation analysis. Significance was set at P< 0.01. RESULTS: Correlation with age was not found for water, collagen, hydroxylysine contents, and enzymatic cross-linking. Nonenzymatic crosslinking was higher in older horses and was linearly related to age (r = 0.94). Water and collagen contents and HP and pentosidine crosslinks were significantly higher at site 1. Hydroxylysine content was significantly lower at site 1. CONCLUSIONS: Except for nonenzymatic glycation, the composition of articular cartilage collagen does not change significantly in adult horses. A significant topographic variation exists in biochemical characteristics of the articular cartilage collagen network in equine metacarpophalangeal joints. These differences may influence local biomechanical properties and, hence, susceptibility to osteochondral disease, as will greater pentosidine crosslinks in older horses that are likely to cause stiffer and more brittle cartilage.     

Pulsed Carbon Dioxide Laser for Cartilage Vaporization and Subchondral Bone Perforation in Horses Part I: Technique and Clinical Results

A carbon dioxide laser, used in a rapidly pulsed mode, was evaluated for intra-articular use in horses. Under arthroscopic guidance, a lensed 5 mm laser probe attached directly to a hand-held carbon dioxide laser was inserted into one intercarpal joint of eight horses. In four horses, a cartilage crater 1 cm in diameter was created to the level of the subchondral bone of the articular surface of the third carpal bone. In four horses, the laser was directed perpendicular to the articular surface of the third carpal bone and activated to penetrate the cartilage and subchondral bone. The intercarpal joint of the opposite carpus in each horse was subjected to arthroscopic examination and insertion of the laser probe for an equivalent time. The laser was not activated and these joints served as sham operated controls. The horses were evaluated clinically for 8 weeks, then euthanatized, and the joints were examined radiographically, grossly, and histologically. Pulsed carbon dioxide laser vaporized cartilage readily but penetrated bone poorly. Cartilage vaporization resulted in no greater swelling, heat, pain on flexion, lameness, or synovial fluid reaction than the sham procedure. Laser drilling resulted in a shallow, charred hole with a tenacious carbon residue, and in combination with the thermal damage to deeper bone, resulted in increased swelling, mild lameness and a low-grade, but persistent synovitis. The carbon dioxide laser is a useful intra-articular instrument for removal of cartilage and has potential application in inaccessible regions of diarthrodial joints. It does not penetrate bone sufficiently to have application in subchondral drilling.     

COMPARISON OF RADIOGRAPHIC SUBCHONDRAL BONE CHANGES WITH ARTHROSCOPIC FINDINGS IN THE EQUINE FEMOROPATELLAR AND FEMOROTIBIAL JOINTS: A RETROSPECTIVE STUDY OF 72 JOINTS (50 HORSES)

Radiographs of 72 femoropatellar and femorotibial joints from 50 horses were evaluated. Ninety four arthroscopically evaluated areas were graded according to a predetermined system. The radiographic grade was then compared to arthroscopic findings in the same location. Statistical analysis was performed to determine the association between the radiographic subchondral bone changes and arthroscopic findings. Radiographically normal areas in the femoropatellar joint were arthroscopically positive for cartilaginous changes in 40% of the femoropatellar joints. Areas of mild subchondral bone flattening (grade I) in the lateral trochlear ridge were arthroscopically positive for cartilage changes 78% of the time. Ninety six percent of moderate to severe subchondral bone changes (grades II-V) were arthroscopically positive for cartilage damage. This research demonstrates that (1) a significant number of radiographically normal joints will have cartilage changes, (2) areas of mild subchondral bone flattening have cartilage changes present in the majority of cases and (3) areas of moderate to severe subchondral bone changes have arthroscopically detectable cartilage changes present.