Cartilage thickness measurement in foals

The talus and proximal and distal epiphysis of the humerus, radius, femur, tibia and distal metacarpus of 20 foals aged 0 to 150 days were obtained at necropsy and sawn sagittally into slabs 4 to 8 mm thick. The thickness of the cartilage (articular cartilage and unossified epiphyseal cartilage) was measured in three to five places in each slab, using a sliding calliper. In most epiphyses, the site, or sites, of thickest cartilage was constant in all foals examined. The difference between thickest and thinnest cartilage within one epiphysis was greatest in distal femora and least in distal metacarpi. The sites of most common occurrence of osteochondrosis dissecans in tali and proximal humeri concurred with the site of thickest cartilage in these bones. The most common site of equine osteochondrosis, the middle and distal thirds of the lateral trochlear ridge of femora, is not the location of thickest cartilage in this epiphysis. Haematological epiphyseal osteomyelitis in foals occurs most frequently in the areas where cartilage thickness is greatest in the medial femoral condyle, talus and distal radius.     

ULTRASOUND APPROACH TO THE CANINE DISTAL TIBIA AND TROCHLEAR RIDGES OF THE TALUS

The aim of the present study was to evaluate to what extent the distal tibia and the trochlear ridges of the talus can be examined with ultrasound (US) in the dog and to establish a protocol for an optimal US examination of these ridges. Six hind limbs of deceased adult mixed-breed dogs were used. In two limbs, needles were placed using US guidance on the trochlea of the talus, just dorsal to and plantar to the distal tibia: one with the tarsal joint in extension and one with the joint in flexion. Then mediolateral (ML) radiographs of both joints were made with the needle in place to determine the percentage of the trochlear ridge of the talus that can be seen using US imaging. An US examination of the tarsal joint was performed on the four other limbs using microconvex (8 MHz) and linear (12 MHz) transducers (Logiq 7) and compound imaging. A three-step protocol was performed including a dorsal approach with the limb extended and the linear transducer (step I), a plantar approach with the limb flexed and the linear transducer (step II), and a plantar approach with the limb flexed and the microconvex transducer (step III). After the US examination, the four limbs were frozen and sectioned, two in a transverse and two in a sagittal plane. Bony structures on the US images were matched with the corresponding anatomic sections. The distal tibia and both trochlear ridges of the talus were easily recognized on the US images using the proposed protocol. When combining the dorsal and plantar approaches, it was possible to visualize up to 75% of the trochlear ridges of the talus in the dog.     

Use of a flexed dorsoplantar radiographic view of the talocrural joint to evaluate lameness in two dogs.

A flexed dorsoplantar radiographic view of the talocrural joint was a useful additional view to diagnose abnormalities of the lateral trochlear ridge of the talus of 2 dogs. This view outlined the subchondral bone of both trochlear ridges of the talus and the apposing cochlea tibiae of the distal portion of the tibia. The tarsus was flexed at the level of the talocrural joint, and an x-ray beam was centered on the joint. With this additional view, fractures of the lateral trochlear ridge were readily diagnosed. This view would help to demonstrate osteochondral lesions of the lateral trochlear ridge.     

Comparison of radiography and ultrasonography to detect osteochondrosis lesions in the tarsocrural joint: A prospective study

Reasons for performing study: Lesions located on the medial malleolus of the tarsocrural joint can be difficult to image radiographically. Ultrasonography allows evaluation of articular cartilage and subchondral bone. Objectives: To compare dorso30° lateral‐plantaromedial‐oblique (DL‐PlMO) and dorso45° views to detect lesions on the medial malleolus, to validate the use of ultrasonography to show lesions in the tarsocrural joint and to compare its sensitivity to radiography. Methods: Tarsocrural joints (n = 111) with osteochondrosis were evaluated ultrasonographically and radiographically prior to arthroscopic lesion debridement. A complete radiographic examination was made and the best view to detect each lesion recorded. Longitudinal and transverse ultrasonography of the dorsal aspect of the joint was performed and the best scan plane to image each lesion recorded. Results: There were 94 joints with lesions on the distal intermediate ridge of tibia, 24 with lesions on the medial malleolus, and 4 with lesions on the lateral trochlear ridge. The sensitivity of radiography to detect lesions on the medial malleolus and distal intermediate ridge of tibia was 71 and 96%, respectively. Eighty‐two percent of lesions on the medial malleolus were better imaged on dorso30° view. The sensitivity of ultrasonography to detect lesions on the medial malleolus and distal intermediate ridge of tibia was 83 and 98%, respectively. Ultrasonography was significantly more sensitive than radiography to detect lesions on the medial malleolus and distal intermediate ridge of tibia. Conclusion: Dorso30° lateral‐plantaromedial‐oblique view was the best to image lesions on the medial malleolus. Ultrasonography was a valuable diagnostic tool to diagnose lesions in the tarsocrural joint and was more sensitive than radiography for lesions located on the medial malleolus and distal intermediate ridge of tibia. Clinical relevance: Radiographic examination should include a dorso30° view for detection of lesions on the medial malleolus and ultrasonography should be considered to diagnose osteochondrosis in the tarsocrural joints.     

On the occurrence of blood vessels in the superficial layers of articular cartilage in bovine fetuses

The occurrence of vascular networks in the superficial layers of articular cartilage of 51 bovine fetuses (10-93 cm CRL) and 3 calves was studied grossly and histologically. The networks were found regularly on the incisura trochlearis of the ulna, on the trochlea of the radius and talus, on the plantar articular surface of the head of the talus, on the proximal articular surface of the fused central and 4th tarsal bones, and less regularly on the articular surfaces of the distal phalanx and distal sesamoid (navicular) bone and on the cochlea of the tibia. The vessels coursed in the superficial stratum of the articular cartilage and were encountered in those places where synovial fossae or villi are found later. The vessels were not present in the calves.     

Osteochondritis dissecans of the tarsocrural joint: results of treatment with arthroscopic surgery

The technique and results of arthroscopic surgery for the treatment of osteochondritis dissecans in 318 tarsocrural joints in 225 horses are reported. Of the 225 horses, 154 were racehorses or intended for racing. Arthroscopic surgery was an effective technique for treating osteochondritis dissecans of the tarsocrural joint. The overall functional ability and cosmetic appearance of the limbs were excellent. Post surgical follow-up information was obtained for 183 horses, of which 140 (76.5 per cent) raced successfully or performed their intended use following surgery. Of the remaining 43, 11 were considered to still have a tarsocrural joint problem, 19 developed other problems precluding successful performance, eight were considered poor racehorses without any lameness problems identified, three were killed because of septic arthritis and two died from other causes. There was no significant effect of age, sex or limb involvement on the outcome. The size of the intermediate ridge lesions had no effect on prognosis but the presence of degenerative or erosive changes in the articular cartilage significantly decreased the prognosis. The synovial effusion resolved in 117/131 racehorse joints (89.3 per cent) and 64 of 86 non-racehorse joints (74.4 per cent) with follow-up. The outcome for synovial fluid resolution was significantly inferior for lesions of the lateral trochlear ridge of the talus or medial malleolus of the tibia compared to distal intermediate ridge lesions. There was no significant relationship between resolution of effusion and successful performance outcome.     

Arthroscopic Anatomy of the Equine Femoropatellar Joint and Approaches for Treatment of Osteochondritis Dissecans

Arthroscopic approaches to the femoropatellar joint were developed to determine their usefulness for evaluation and surgical treatment of osteochondritis dissecans. It was found that the articular cartilage of the lateral trochlear ridge, medial trochlear ridge, intertrochlear groove, patella, and the lateral and medial reflections of the joint capsule could be examined from an infrapatellar arthroscopic portal. The suprapatellar pouch could be examined partially. Lateral and medial instrument portals were evaluated to determine the accessibility of the lateral and medial trochlear ridges of the femur in the areas where osteochondritis dissecans lesions frequently occur. Sliding the arthroscope sleeve beneath the patella when entering the joint was associated with iatrogenic cartilage lesions. A new technique that directed the arthroscope lateral to the lateral trochlear ridge eliminated iatrogenic cartilage damage.     

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.     

Heterotopic Transfer of Fresh and Cryopreserved Autogenous Articular Cartilage in the Horse

Two 10 mm thick osteochondral grafts were harvested from the lateral aspect of the lateral trochlear ridge of the left talus in each of 10 anesthetized horses. The grafts were frozen in a 7.5% DMSO solution and stored in liquid nitrogen. The horses were anesthetized again on day 14 and the thawed grafts were press-fitted into drill holes in the trochlear ridges of the right stifle. A fresh graft was transferred from the right hock to the left stifle. To control for the effects of surgery, another fresh graft was transferred from the right stifle to the left stifle. The result was two grafts in each femoropatellar joint. Fresh and frozen osteoarticular autografts appeared to maintain a durable weight-bearing surface for 3 months; however, the fresh grafts were clearly superior. Frozen grafts had fewer living chondrocytes, decreased safranin-O staining, and decreased SO435 uptake. Graft stability and articular surface congruency were determining factors in the outcome of all grafts. Since the availability of osteochondral autografts is limited, further work on the use of preserved allogeneic osteochondral tissue is warranted.     

Functional, radiographic, and histologic assessment of healing of autogenous osteochondral grafts and full-thickness cartilage defects in the talus of dogs.

A circular (5.5 mm diameter) full-thickness cartilage defect was created on the medial ridge of the talus in 12 skeletally mature dogs. In 6 dogs, the articular surface of the lesion was repaired, using an osteochondral graft obtained from the ipsilateral manus. The graft (digit I, first phalanx, distal articular surface and diaphysis) was contoured to obtain a press fit in the drilled talar recipient site. In 6 dogs, the lesion was not treated and healed by fibrous tissue replacement. Functional assessment (lameness, hock range of motion, joint stability, joint crepitus, and mid-femoral muscle circumference) was completed before surgery and at postoperative weeks 2 through 20. Radiographic assessment (periarticular soft tissue width, joint space width, osteophyte formation, and graft incorporation) was completed before surgery and at postoperative weeks 0, 6, 12, and 20. To facilitate histologic assessment, tissues were stained with toluidine blue and H&E. Histologic assessment of the articular surface on the surgically treated talus, ipsilateral tibia, and contralateral talus was completed, using a modification of the Mankin grading system. Subchondral bone was examined to assess graft viability and incorporation. Analysis of the ordinal data was completed, using a Mann-Whitney rank sum test. All dogs were fully weight bearing by postoperative week 7. Dogs without grafts had significantly (P = 0.036) better clinical function at postoperative week 6. Significant difference in functional assessment was not evident at postoperative week 20. Immediate postoperative radiographic assessment revealed significant (P = 0.005) difference between nongrafted and grafted groups. Significant difference was not observed at postoperative week 6, 12, or 20. All grafts appeared radiographically incorporated by postoperative week 12. All grafts restored joint surface congruity, whereas 3 of 6 nongrafted lesions had poor articular congruity. Of 6 grafts, 4 partially retained normal hyaline cartilage, resulting in significantly (P = 0.014) lower Mankin grades. Significant histologic differences between groups were not apparent when the apposing tibia and control talus were examined. Talar reconstruction by use of a phalangeal osteochondral graft is a viable surgical procedure. These data indicate that normal articular and subchondral architecture are more closely approximated by osteochondral reconstruction than by fibrous tissue repair.     

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.     

Incorporation of Fresh and Cryopreserved Bone in Osteochondral Autografts in the Horse

The structural integrity of subchondral bone in fresh and frozen osteochondral autografts was investigated at month 3 in 10 horses. Two osteochondral autografts were harvested from the lateral aspect of the lateral trochlear ridge of the left talus in each of 10 anesthetized horses. Grafts were frozen in 7.5% DMSO. After 14 days, the thawed grafts were press-fitted into drill holes in the trochlear ridges of the right stifles. A fresh graft from the right hock was implanted in each left stifle. To control for the effects of surgery, a fresh graft was transferred from the right stifle to the left stifle. The end result was two grafts in each femoropatellar joint. Fresh and frozen bone grafts maintained a structurally intact support for the cartilage surface. Graft stability and surface congruency were determining factors in the outcome of the grafts. Incorporation of both types of graft was complete at month 3, but remodeling of the fresh grafts was more active.     

Arthroscopic Approach and Intra-Articular Anatomy of the Plantar Pouch of the Equine Tarsocrural Joint

Arthroscopic examination of structures within the plantar pouch of the tarsocrural joint was accomplished via portals in both the plantaromedial and plantarolateral aspects of the joint. Flexion and extension of the tarsus while examining the joint through either portal allowed observation of the proximal and plantar aspects of the lateral and medial trochlear ridges, the trochlear groove, the caudal aspect of the distal tibia, and the deep digital flexor tendon (DDFT) in its sheath. From a plantarolateral portal, the plantar talocalcaneal ligament and the plantar aspect of the lateral malleolus could be observed. The caudal aspect of the medial malleolus could not be observed with flexion or extension of the joint from a plantaromedial portal, but in some horses, the caudal aspect of the lateral malleolus could be observed. The dorsolateral and dorsomedial aspects of the plantar pouch were best examined from a portal on the ipsilateral side of the joint. An instrument portal opposite either arthroscope portal allowed access to most regions of the joint except the abaxial surface of the trochlear ridge opposite the instrument.     

134 Horses with osteochondritis dissecans of the tarso-crural joint: Clinical considerations and results following arthroscopic surgery

A retrospective study was performed on a sample of 134 horses diagnosed with osteochondritis dissecans (OCD) of the tarso-crural joints that underwent surgery for the removal of osteochondral fragments. Breed, age, site of the lesion, amount of synovial effusion and its resolution following surgery were evaluated.In more than 70 percent of cases the lesion involved the distal intermediate ridge of the tibia. The lateral trochlea ridge of the talus was involved in 6 percent of cases studied. OCD of the lateral trochlea ridge of the talus was frequently associated with OCD in other anatomical sites. Eighty-four percent of surgically treated cases that had post-op following returned to training exercise or racing activity.     

A Lateral Surgical Approach to the Equine Femoropatellar Joint

A surgical approach to the lateral trochlear ridge of the distal femur of the horse was developed to facilitate evaluation and curettage of osteochondral defects of the lateral trochlear ridge. Surgical exploration of the lateral trochlear ridge was achieved in 11 patients with osteochondral defects of the lateral trochlear ridge using a craniolateral arthrotomy between the middle and lateral patellar ligaments. The technique described allowed adequate exposure for evaluation, removal of loose osteochondral fragments, and curettage of cartilage abnormalities on the lateral trochlear ridge.     

Changes on radiographs at Thoroughbred yearling sales: Prevalence and significance

Examination of Thoroughbred yearlings at public auction is a special form of prepurchase examination since the clinician cannot be as thorough as in clinical situations. Yearlings are purchased based on visual and limited physical examinations and evaluation of presale radiographs and upper respiratory tract endoscopic examination. The prevalence and clinical relevance of radiographic changes has been the subject of our recent publications and a summary of our results is presented here. Radiographic changes were most common in the fetlock joints and 1127 forelimb and 1102 hindlimb fetlock radiographic series were examined. Flattened areas of the distal palmar aspect of the distal articular surface of the third metacarpal bone (McIII) were found in 41% of yearlings and had neither an effect on performance nor caused the subsequent development of clinical problems. Flattening (10%) or radiolucency (17%) of the dorsal aspect of the distal sagittal ridge of McIII was common and had no effect of these 2 parameters. Thirty of 1130 yearlings that had complete carpal radiographic examinations had signs of dorsal medial middle carpal disease. The presence of dorsal medial middle carpal joint lesions affected the horse’s ability to start a race and increased the incidence of clinical problems. The most common finding on carpal radiographs was circular radiolucencies in the ulnar carpal bone but the presence of this finding neither affected the ability to start nor was associated with clinical problems. Forty-eight of 1101 yearlings with complete tarsal radiographic examinations had concavity or fragmentation of the cranial intermediate ridge of the distal tibia, but there was no effect on racing performance. The changes most commonly observed in the distal tarsal joints were the presence of osteophytes or enthesophytes involving the distal intertarsal or tarsometatarsal joints. The presence of osteophytes or enthesophytes involving the distal intertarsal or tarsometatarsal joints were the only changes significantly associated with starting a race, but the effect was small. There were 600 yearlings with stifle radiographs, but in only 170 of them could the medial femoral condyle and proximal tibia be evaluated. Thirty-four yearlings had defects with or without fragments on the lateral trochlear ridge of the femur and there were no significant associations with any outcome except that they were more likely to have surgical treatment.     

Proteoglycan synthesis and content in articular cartilage and cartilage repair tissue in horses

Hexosamine concentration, DNA concentration, and [35S]sulfate incorporation for articular cartilage obtained from various sites in the metacarpophalangeal and carpal joints of horses were measured. The same measurements were made on the repair tissue filling full-thickness articular defects in the intermediate carpal bone and on cartilage surrounding partial-thickness defects 6 weeks after the defects were created arthroscopically. Cellularity (measured as DNA concentration), proteoglycan content (measured as hexosamine concentration), and proteoglycan synthesis (measured as [35S]sulfate incorporation) varied according to the site sampled. Cartilage from the transverse ridge of the head of the third metacarpal bone and the radial facet of the third carpal bone had the lowest hexosamine concentration, whereas rate of proteoglycan synthesis was lowest in cartilage from the transverse ridge of the head of the third metacarpal bone and the distal articular surface of the radial carpal bone. Repair tissue filling a full-thickness cartilage defect at 6 weeks was highly cellular. It was low in proteoglycan content, but was actively synthesizing these macromolecules. In contrast, the cartilage surrounding a partial-thickness defect was unchanged 6 weeks after the original defect was made.     

Unusual osteochondral lesions of the talus in a horse

A 2-year-old Thoroughbred gelding was evaluated for a grade 3 out of 5 unilateral hind limb lameness. Flexion of the right hock and stifle joints (spavin test) exacerbated the lameness. Response to intra-articular and perineural anaesthesia isolated the source of lameness to the tarsocrural area, despite an absence of tarsocrural joint effusion. Routine radiographic examination of the hock did not reveal any significant abnormalities. Skeletal nuclear scintigraphic evaluation revealed a focal region of increased bone activity in the proximal medial trochlear ridge of the talus. Flexed lateromedial radiographic views identified three discrete semicircular lytic lesions at the proximal articular margin of the medial trochlear ridge of the talus. Conservative management of the lesions was associated with a successful return to racing. The location and appearance of the osteochondral lesions of this report have not been previously reported and may be a manifestation of developmental orthopaedic disease and abnormal endochondral ossification. Nuclear scintigraphy and flexed lateromedial radiographic views facilitated identification of the lesions. This radiographic view is recommended when lameness is isolated to the tarsocrural joint and standard radio-graphic projections fail to identify a cause.     

CORRELATION OF ARTICULAR CARTILAGE THICKNESS MEASUREMENTS MADE WITH MAGNETIC RESONANCE IMAGING,MAGNETIC RESONANCE ARTHROGRAPHY,AND COMPUTED TOMOGRAPHIC ARTHROGRAPHY WITH GROSS ARTICULAR CARTILAGE THICKNESS IN THE EQUINE METACARPOPHALANGEAL JOINT

Osteoarthritis of the metacarpophalangeal joint is common cause of lameness in equine athletes, and is hallmarked by articular cartilage damage. An accurate, noninvasive method for measuring cartilage thickness would be beneficial to screen for cartilage injury and allow for prompt initiation of interventional therapy. The objective of this methods comparison study was to compare computed tomographic arthrography (CTA), magnetic resonance imaging (MRI), and magnetic resonance arthrography (MRA) measurements of articular cartilage thickness with gross measurements in the metacarpophalangeal joint of Thoroughbred horses. Fourteen cadaveric, equine thoracic limbs were included. Limbs were excluded from the study if pathology of the metacarpophalangeal articular cartilage was observed with any imaging modality. Articular cartilage thickness was measured in nine regions of the third metacarpal bone and proximal phalanx on sagittal plane MRI sequences. After intra‐articular contrast administration, the measurements were repeated on sagittal plane MRA and sagittal CTA reformations. In an effort to increase cartilage conspicuity, the volume of intra‐articular contrast was increased from 14.5 ml, to maximal distention for the second set of seven limbs. Mean and standard deviation values were calculated, and linear regression analysis was used to determine correlations between gross and imaging measurements of cartilage thickness. This study failed to identify one imaging test that consistently yielded measurements correlating with gross cartilage thickness. Even with the use of intra‐articular contrast, cartilage surfaces were difficult to differentiate in regions where the cartilage surfaces of the proximal phalanx and third metacarpal bone were in close contact with each other.