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.     

Epiphyseal cartilage canal blood supply to the distal femur of foals

REASONS FOR PERFORMING STUDY: The developmental pattern of the cartilage canal blood supply to epiphyseal growth cartilage has been linked to osteochondrosis (OC) in the tarsus of foals. This pattern has not yet been described in the distal femur, another site frequently affected by OC. OBJECTIVE: To describe the developmental pattern of the blood supply to the distal femoral epiphyseal growth cartilage in 8 Standardbred foals age 0-7 weeks. METHODS: One foal was sacrificed weekly from birth to age 7 weeks (n=8) to undergo a barium perfusion procedure to demonstrate vessels within cartilage canals of one hindlimb. The distal end of the femur was cleared in methyl salicylate and perfused vessels were studied in the intact bones. Each distal femur was then sawed into 5 mm thick slabs in the transverse plane, and the slabs decalcified and radiographed. Finally, the lateral trochlear ridge was separated from each slab and examined histologically. RESULTS: The cartilage canal blood supply regressed with increasing age, but several regions remained vascularised in the oldest foal at age 7 weeks. Vessels arose from perichondrial and subchondral arterial sources, and coursed perpendicular or parallel to the ossification front. The midsection of parallel vessels became incorporated into the ossification front during growth. Anastomoses formed and vessels within the distal portion of canals with an original perichondrial source shifted to use subchondral vessels as their arterial source. Both parallel and perpendicular vessels therefore traversed the ossification front to enter cartilage canals. No histological lesions were observed in sections from any of the foals. CONCLUSION: The same anatomical feature (traversing the ossification front to enter cartilage canals) reported to render vessels vulnerable to failure in the tarsus was also present in the distal femur of foals. POTENTIAL RELEVANCE: OC may occur by the same pathogenetic mechanism in the distal femur as in the tarsus of foals.     

Epiphyseal cartilage canal blood supply to the metatarsophalangeal joint of foals

Reasons for performing study: It is presently unknown whether cartilage ischaemia plays any part in the pathogenesis of osteochondral fragmentation within the equine metatarsophalangeal joint, as no detailed studies on microcirculation in the area have been reported. Objective: To describe the developmental pattern of the blood supply to the epiphyseal growth cartilage in the metatarso‐phalangeal joint of foals. Methods: Eight Standardbred foals were sacrificed between birth and age 7 weeks to undergo a barium perfusion procedure to demonstrate vessels within growth cartilage canals of one hindlimb. The metatarso‐phalangeal joint was cleared in methyl salicylate and perfused vessels studied in the intact bones. The bones were sawed into 5 mm thick slabs, decalcified and radiographed. Selected slabs were cleared in methyl salicylate for a second time and examined at low magnification. The dorsal half of the sagittal ridge of the distal third metatarsal bone and the plantar half of the proximal phalanx were examined histologically. Results: Regions of the epiphysis with thick cartilage contained a greater number of perfused vessels than regions with thin cartilage. The cartilage canal vessels were oriented either parallel or perpendicular to the underlying ossification front. Cartilage canal vessels were incorporated into the ossification front during growth and became reliant on a subchondral arterial source. Macroscopically visible lesions were not detected in the current group of foals. On histological examination, pathological changes consisting of an area of chondronecrosis surrounded by fibrovascular granulation tissue were found in sections from the lateral proximo‐plantar eminence of the proximal phalanx in the 7‐week‐old foal. Conclusion: The same anatomical feature (traversing the ossification front to enter cartilage canals) reported to render vessels vulnerable to failure in the tarsus was also present in the metatarso‐phalangeal joint of foals. Potential relevance: Osteochondrosis may occur by the same pathogenetic mechanism in the metatarso‐phalangeal joint as in the tarsus of foals.     

Haematogenous osteomyelitis in cattle

The examination of 70 cattle with haematogenous osteomyelitis resulted in the classification of the bone lesions into two main groups: the physeal type, in which an infection, usually of metaphyseal bone, originated at or near the growth plate, usually in the distal metacarpus, metatarsus, radius or tibia, and the epiphyseal type, in which an infection originated near the junction of the subchondral bone and the immature epiphyseal joint cartilage, most often in the distal femoral condyle epiphysis, the patella and the distal radius. Combinations of physeal and epiphyseal defects and even diaphyseal involvement were occasionally seen. Epiphyseal osteomyelitis was mostly caused by salmonella infection, physeal by Corynebacterium pyogenes, salmonella and other bacteria. The salmonella affected animals were with one exception less than 12 weeks old and the majority had had some previous illness or came from a problem herd. The C pyogenes affected calves were in almost all cases more than six months old. The prognosis of the metaphyseal infection was in general satisfactory, and surgical intervention (osteotomy or sequestrectomy) was often required. The prognosis of the epiphyseal type was grave but two of the three animals in which physeal and epiphyseal defects were accompanied by diaphyseal lesions recovered.     

Epiphyseal cartilage canal blood supply to the tarsus of foals and relationship to osteochondrosis

REASON FOR PERFORMING STUDY: Pathological changes in the blood supply to growth cartilage have been implicated in the pathogenesis of osteochondrosis (OC) in horses, but have not been reported using vascular perfusion techniques. OBJECTIVE: To describe the developmental pattern of cartilage canal vessels in the distal tibial epiphysis and talar growth cartilage of foals. METHODS: Nine foals bred from parents with OC were sacrificed between the ages of 0 and 7 weeks to undergo a barium perfusion procedure. The distal end of the tibia and the entire talus were cleared in methyl salicylate and perfused vessels studied in the intact bones. Slabs with a thickness of 4-5 mm from 3 predilection sites for OC were examined in the stereomicroscope and with light microscopy. RESULTS: Cartilage canals were present for a limited period of growth. Perfused vessels initially entered canals from the perichondrium. Vessels in the proximal portion of canals retained their perichondrial arterial source throughout. With time, the ossification front advanced to incorporate the mid-portion of canals; and anastomoses formed between canal vessels and subchondral vessels. A shift occurred and vessels in the distal terminus of canals came to use subchondral vessels as their arterial source. Twelve histological lesions were found in 7 foals. All contained necrotic vessels surrounded by necrotic growth cartilage and 3 caused macroscopically visible delay in endochondral ossification. Lesions were located where vessels traversed the ossification front to enter the distal terminus of canals. CONCLUSION: Cartilage canal vessels are particularly susceptible to failure at the point where they cross the ossification front, with consequences for the viability of those chondrocytes that depend on them. POTENTIAL RELEVANCE: A better understanding of how lesions of OC arise may improve the ability to identify, monitor, prevent and treat this disorder. Involvement of cartilage canals in the pathogenesis of equine tarsal OC plausibly explains several clinical features of this disease.     

Early lesions of articular osteochondrosis in the distal femur of foals

Failure of the cartilage canal blood supply to epiphyseal growth cartilage has been implicated in the pathogenesis of articular osteochondrosis in horses and other animal species. In a previous study of the developmental pattern of the blood supply in the tarsus of foals, early lesions of osteochondrosis were consistently found in regions where the cartilage canal vessels traversed the chondro-osseous junction. The developmental pattern of blood vessels has also been described in the distal femoral epiphysis; however, the group of foals examined in that study did not have lesions of osteochondrosis in this location. Therefore, the relationship between the occurrence of early lesions of osteochondrosis and the developmental pattern of the blood supply to epiphyseal growth cartilage in this site in foals has not been examined. Distal femora were collected from 30 fetuses and foals (up to 11 months old) submitted for postmortem examination. Sections from the lateral trochlear ridge and medial femoral condyle of both hind limbs were examined histologically. Sixteen cartilage lesions were found in 7 of the 30 fetuses and foals. All lesions contained evidence of cartilage canal necrosis and ischemic chondronecrosis. The lesions were located in regions where cartilage canal vessels traversed the chondro-osseous junction, as previously observed in the tarsus. The location and morphology of lesions indicated that a subclinical stage of ischemic chondronecrosis existed that preceded and predisposed to the development of osteochondrosis dissecans and subchondral bone cysts.     

The site of focal osteomyelitis lesions in foals

The long bone ends of foals with infectious disease were sawn into sagittal slabs, washed and inspected. Tissue suspected to be abnormal on the basis of change of colour and consistency was radiographed, and then decalcified and examined histologically. The exact site of 140 focal osteomyelitis lesions from 18 foals was determined. There were more lesions in the epiphysis than the metaphysis. Epiphyseal lesions were in specific sites within a given epiphysis, and in most epiphyses the lesions were at the site of thickest cartilage. Metaphyseal lesions in the metacarpal, metatarsal and distal radial growth plates tended to be on the more inclined parts of the growth plate.     

The site of focal osteomyelitis lesions in foals

Summary

The long bone ends of foals with infectious disease were sawn into sagittal slabs, washed and inspected. Tissue suspected to be abnormal on the basis of change of colour and consistency was radiographed, and then decalcified andexamined histologically. The exact site of 140 focal osteomyelitis lesions from 18 foals was determined. There were more lesions in the epiphysis than the metaphysis. Epiphyseal lesions were in specific sites within a given epiphysis, and in most epiphyses the lesions were at the site of thickest cartilage. Metaphyseal lesions in the metacarpal, metatarsal and distal radial growth plates tended to be on the more inclined parts of the growth plate.     

Vascular pattern of the developing knee joint in the domestic fowl

Laying strain fowls were reared from hatching till 20 weeks old. Birds were killed throughout the growth period and specimens from the distal femur and proximal tibiotarsus prepared for study. The origin and nature of cartilage canals were established in the two bone extremities. The canals follow a pattern of development which was similar in fowls of the same age. Similarities were noted with the vascular patterns reported in other species. The epiphyseal ossification centre of the proximal tibiotarsus formed in an area extensively perfused by cartilage canals. Anastomoses occurred between epiphyseal vascular canals in association with the formation and growth of the epiphyseal ossification centre in the proximal tibiotarsus. Anastomoses between epiphyseal vascular canals did not occur at any other site. The development of the epiphyseal ossification centre in the proximal tibiotarsus suggests that this is a traction epiphysis.     

Immunolocalization of basic fibroblast growth factor in porcine epiphyseal growth plate

Recent evidence clearly indicates that basic fibroblast growth factor (bFGF) signal transduction is essential for normal skeletal development. Here, we report that bFGF and its receptor are specifically localized in the terminal hypertrophic chondrocytes of the porcine epiphyseal growth plate, the tissue responsible for longitudinal bone growth. Similar observations were obtained with the chondrocytes immediately adjacent to resorbing blood vessels in the secondary center of ossification of the epiphysis. These results are consistent with a recent proposal that bFGF functions in coupling osteogenesis with chondrogenesis by attracting the vascular invasion of cartilage from adjacent trabecular bone.     

Cartilage matrix changes in the developing epiphysis: early events on the pathway to equine osteochondrosis?

REASONS FOR PERFORMING STUDY: The earliest osteochondrosis (OC) microscopic lesion reported in the literature was present in the femorotibial joint of a 2-day-old foal suggesting that OC lesions and factors initiating them may arise prior to birth. OBJECTIVE: To examine the developing equine epiphysis to detect histological changes that could be precursors to OC lesions. METHODS: Osteochondral samples from 21 equine fetuses and 13 foals were harvested from selected sites in the scapulohumeral, humeroradial, metacarpophalangeal, femoropatellar, femorotibial, tarsocrural and metatarsophalangeal joints. Sections were stained with safranin O and picrosiruis red to assess cartilage changes and structural arrangement of the collagen matrix. RESULTS: Extracellular matrix changes observed included perivascular areas of paleness of the proteoglycan matrix associated with hypocellularity and, sometimes, necrotic chondrocytes. These changes were most abundant in the youngest fetuses and in the femoropatellar/femorotibial (FP/FT) joints. Indentations of the ossification front were also observed in most specimens, but, most frequently, in scapulohumeral and FP/FT joints. A cartilage canal was almost always present in these indentations. The vascular density of the cartilage was higher in the youngest fetuses. In these fetuses, the most vascularised joints were the metacarpo- and metatarsophalangeal joints but their cartilage canals regressed quickly. After birth, the most vascularised cartilage was present in the FP/FT joint. Articular cartilage differentiated into 4 zones early in fetal life and the epiphyseal cartilage also had a distinct zonal cartilage structure. A striking difference was observed in the collagen structure at the junction of the proliferative and hypertrophic zones where OCD lesions occur. CONCLUSION: Matrix and ossification front changes were frequently observed and significantly associated with cartilage canals suggesting that they may be physiological changes associated with matrix remodelling and development. The collagen structure was variable through the growing epiphysis and a differential in biomechanical properties at focal sites may predispose them to injury.     

Intra-osseous pressure of the equine third metatarsal bone

Intra-osseous pressure was measured in the third metatarsal bone of 8 pony foals at the age of 1, 3, 6 and 26 weeks of age, and on one occasion in the third metatarsal bone of 5 ponies aged 1-5 years; the animals were under general anesthesia and in lateral recumbency. Saphenous venous pressure and lateral superficial plantar metatarsal arterial pressure were also monitored throughout the procedure. There were no statistically significant changes in the epiphyseal, diaphyseal, venous or arterial pressures with increasing age of the foals. There was no statistically significant difference between the mean epiphyseal and mean diaphyseal pressures in the foals. Individually however, the diaphyseal pressure exceeded the epiphyseal pressure in 32 of the 36 measurements made in the foals. Saphenous vein occlusion and intravenous adrenalin administration showed that both venous and arterial pressures influence intra-osseous pressure. Intra-osseous injection of heparinized saline on one side of the growth plate produced an immediate massive increase in intra-osseous pressure on that side of the growth plate, but in almost all cases a concomitant rise in intraosseous pressure on the other side of the physis did not occur. Simulated effusion of the metatarsophalangeal joint was associated with an increase in intraosseous pressure in the adjacent metatarsal epiphysis, and flexion of the joint with an increase in intraosseous pressure in both the epiphysis and the metaphysis.     

Conservative Management of a Distal Epiphyseal Metacarpal Fracture in a Skyros Pony

Epiphyseal fracture, also known as epiphysiolysis, is the loosening or separation, either partial or complete, of an epiphysis from the shaft of a long bone. Distal epiphyseal fractures in foals pose a substantial challenge due to their guarded prognosis. This report describes the clinical signs, diagnosis, successful conservative treatment of an 1-month-old, male Skyros pony with an epiphyseal fracture of the right third metacarpal bone (type II Salter-Harris). The owner declined surgical treatment because of financial considerations along with the unfavorable prognosis. Conservative fracture treatment was pursued through external reduction and coaptation. The total duration of the conservative treatment was eighteen weeks and the foal returned to complete health.     

Evaluation of an Interfragmentary Compression System for the Repair of Equine Femoral Capital Physeal Fractures

Femoral neck and proximal epiphyseal lengths were measured in 37 femurs from 19 cadaver foals that were 1 day to 12 months old to determine the applicability of a human interfragmentary compression system to equine femoral capital physeal fractures. Because components of the implant system are available only in fixed sizes, its use was possible in foals older than 5 weeks of age, but not in younger foals. The 135 degree angle plate conformed best to the equine femur. Femoral capital physeal fractures were created surgically and repaired with the implant system in three foals. Fracture stability was evident clinically and radiographically in all three foals until euthanasia at month 3. At necropsy, the treated femurs were 4, 8, and 27 mm shorter than their mates. Epiphyseal viability was verified in all three foals by tetracycline deposition and new appositional bone growth comparable with that in the contralateral control epiphyses. The treated capital physis was open but reduced in thickness in one foal, disorganized in one foal, and closed in one foal. Fixation by compression with the implant system resulted in stability sufficient for fracture healing and maintenance of epiphyseal viability, although it was associated with reduced longitudinal femoral growth.     

MAGNETIC RESONANCE IMAGING IN FOALS WITH INFECTIOUS ARTHRITIS

The magnetic resonance (MR) imaging findings of foals with infectious and noninfectious arthritis are described. Six foals with infectious arthritis and three foals with noninfectious arthritis were grouped based on synovial fluid analysis results and examined with radiography and MR imaging. Four out of six foals with infectious arthritis had osseous lesions in MR images indicative of osteomyelitis and only 4/19 lesions were detected on digital radiographs. The three foals with noninfectious arthritis had no osseous lesions in MR images or radiographically. Of the six joints that had osseous lesions detected with MR imaging, three had at least one lytic lesion detected radiographically. Osseous lesions in the epiphysis, metaphysis, and physis appeared in MR images as T2W, short tau inversion recovery, and proton density hyperintense foci with a hypointense halo. The same lesions appeared hyperintense in the 3D RSSG water excitation pulse sequence but lacked a surrounding hypointense halo. Most joints of foals with infectious arthritis had heterogenous signals within the synovial fluid whereas all of the nonseptic joints had homogenous synovial fluid signals. MR imaging appears to be better than radiography in the detection of osseous lesions in foals diagnosed with infectious arthritis and may be a valuable screening test for the presence of osteomyelitis.     

Rib osteomyelitis in three foals

Three foals aged between 21 and 44 days were presented for evaluation of pyrexia and lameness. Each had subcutaneous abscessation associated with osteomyelitis of a rib at the costochondral junction and pathological fracture of the affected rib; one foal had more than one rib affected. Other localised sites of infection included other sites of osteomyelitis, omphalophlebitis, uveitis, enterocolitis, and calcaneal bursitis. The subcutaneous abscessation and rib osteomyelitis was treated surgically in two foals. Salmonella typhimurium was isolated from the subcutaneous abscess in one foal and from the faeces of another. Two of the three foals were euthanased. Ultrasonography was a more useful modality than radiography for establishing the diagnosis of costal osteomyelitis.     

Microangiographic studies of metaphyseal vessels in young foals

Selective perfusion and microangiographic examination of the radius and metacarpus of 30 foals were performed. Vessels of extraosseous origin supplying the peripheral part of the metaphysis were not demonstrated in young foals, but became more obvious in older animals. The development of this vessel system coincided with the reduction of transphyseal vessels from the epiphysis crossing the growth plate.     

Effect of two different nutritional programs on orthopedic alterations in mangalarga marchador foals

This study was carried out to verify the effects of two nutritional programs (TA: supplementation with concentrate plus mineral mix between two and 12 months of age, and TB: supplementation with concentrate plus mineral mix from weaning at 165 days of age to 12 months on growth parameters in 22 Mangalarga Marchador foals. Data recorded were: cortical index (CI), time of epiphyseal cartilage closure of distal metacarpus and proximal phalange, epiphysitis and flexural deformity occurrences and weight/height ratio (W/H). Body measurements were taken monthly and radiographs every two months. Animals were born from September 1993 to February 1994 and were allocated to treatments according to the following criteria: each two subsequent foals of the same sex, from the same stallion were randomly assigned to opposite treatments. Data from the randomized block design were submitted to analysis of variance and their means compared by F test. TA foals showed less epiphysitis until 272 days of age and better CI from 228 days on. W/H up to 2:1 did not influence epiphysitis occurrence. Feed restriction (TB) delayed epiphyseal cartilage closure of distal metacarpus and proximal phalanx. No flexural limb deformity was observed in foals on either treatment.     

Fractures of the distal phalanx of the forelimb in eight foals

Fractures of the distal phalanx of the forelimb were diagnosed in 5 colts and 3 fillies ranging in age from 2 weeks to 5 1/2 months at the time of fracture. Three fractures entered the distal interphalangeal joint and 6 fractures (one foal had bilateral fractures) were nonarticular. All foals with articular fractures became sound with conservative treatment. Four of 5 foals with nonarticular fractures became sound with conservative treatment and 1 foal developed separation of the hoof at the coronary band after application of acrylic around the hoof. On the basis of our observations in these foals, sagittal articular and nonarticular distal phalangeal fractures in foals should be treated conservatively. Foals so treated would have an excellent prognosis for return to soundness.     

A XERORADIOGRAPHIC STUDY OF THE DEVELOPING QUARTERHORSE FOREDIGIT AND METACARPOPHALANGEAL REGION FROM SIX TO TWELVE MONTHS OF AGE

The purpose of the project was to provide a reference for radiographic anatomy of the developing equine foredigit and metacarpophalangeal region. Using xeroradiographic techniques, both foredigits and metacarpophalangeal regions of six Quarter Horse foals were radiographed at 1 day of age and then at 2-week intervals until the foals were 6 weeks old. The foals were then radiographed at 4-week intervals until they were 12 months old. The period from birth to 6 months has been described in a previous report. This paper deals with the period from 6 to 12 months of age. Lateromedial and dorsopalmar xeroradiographs of each foredigit and metacarpophalangeal region and a dorsal 65° proximal-palmarodistal oblique view of the distal part of the digit were made at each examination. Foals were weighed and were measured at the withers immediately prior to each examination. Representative xeroradiographs were selected and appropriately labeled to demonstrate normal radiographic anatomy of these regions. Earliest radiographic visualization of distal epiphyseal ossification in metacarpal 2 and metacarpal 4 was extremely variable and ranged from 4 to 38 weeks. It was not possible to determine accurately the ages at which distal physes of the small metacarpal bones closed. In one foal, three of four of these physes were closed at 26 weeks, while in another foal, none had closed when last radiographed at 54 weeks. Radiographic closure of the proximal physis of the middle phalanx ranged from 18 to 30 weeks (mean = 26 weeks). Radiographic closure of the proximal physis of the proximal phalanx ranged from 22 to 38 weeks (mean = 30 weeks). Radiographic closure of the distal physis of metacarpal 3 ranged from 18 to 38 weeks (mean = 29 weeks).