Treatment response and athletic outcome of foals with tarsal valgus deformities: 39 cases (1988-1997)

OBJECTIVE: To evaluate the response to various treatments and long-term outcome of foals with tarsal valgus deformities. DESIGN: Retrospective study. ANIMALS: 39 foals with tarsal valgus deformities. PROCEDURE: Data collected from medical records, included signalment, history, reason for admission, and clinical findings. Radiographic views of the tarsus were evaluated for incomplete ossification of tarsal bones and were classified as normal in appearance, type-I incomplete ossification, or type-II incomplete ossification. Treatment and athletic outcome were documented for each foal. RESULTS: Radiographic assessment revealed that 22 of 39 foals (56%) had concomitant tarsal valgus deformities and incomplete ossification of the tarsal bones. Eight of 19 foals with tarsal valgus deformities that were treated with periosteal stripping responded favorably. Foals < or = 60 days old were significantly more likely to respond to periosteal stripping than older foals. Five of 8 foals with tarsal valgus deformities that were treated with growth plate retardation responded favorably. Eleven of 21 foals with long-term follow-up performed as intended. Compared with foals with type-II incomplete ossification, foals with tarsal bones that had a normal radiographic appearance or type-I incomplete ossification were significantly more likely to perform as intended. CONCLUSIONS AND CLINICAL RELEVANCE: Foals with tarsal valgus deformities should have lateromedial radiographic views of the tarsus obtained to assess the tarsal bones for incomplete ossification, which will affect athletic outcome. Because foals with type-II incomplete ossification of the tarsal bones respond poorly to periosteal stripping alone, treatment by growth-plate retardation is recommended.     

A SKELETAL OSSIFICATION INDEX FOR NEONATAL FOALS

A skeletal ossification index (SOI) was devised to standardize the radiographic evaluation of the carpal and tarsal regions of newborn foals (less than two weeks of age). This index was based on two radiographic views of a carpus and a tarsus. Four grades of cuboidal bone ossification were discerned: Grade 1 foals had some cuboidal bones with no ossification; Grade 2 was assigned when all cuboidal bones had radiographic evidence of some ossification; in Grade 3 the bones were small and round; in Grade 4 the cuboidal bones were shaped like the adult counterparts. Radiographs were taken of 24 neonatal foals of various gestational ages (range, 297–374 days). The relationships between the SOI and two measures of newborn foal developmental maturity, gestationai age and body weight, were assessed. There was no relationship between the sex of the foal and the SOI, but there was a relationship between the SOI and the gestational age (one-tailed Spearman's rank correlation coefficient, r = 0.748) and between the SOI and body weight (r = 0.77) for the 24 foals. For the ten foals with gestational ages less than 320 days, the relationship between body weight and the SOI was significant (r = 0.953), but the relationship between gestational age and the SOI was not significant (r = 0.605). The degree of ossification of the bones of neonatal foals that are born prematurely (< 320 days of gestation) or are "small-for-gestational age" at birth may be incomplete, and we suggest that radiographs of these regions should be made to assess ossification in foals in these two high risk groups.     

MONITORING THE PROGRESSION OF TARSAL OSSIFICATION WITH ULTRASONOGRAPHY AND RADIOGRAPHY IN THREE IMMATURE FOALS

Repeated ultrasonographic and radiographic examinations of both tarsi were performed on three immature foals at individually adjusted times to monitor the progression of ossification. The first examination was performed soon after birth, and all foals were found to have incomplete ossification of the tarsal bones. Two of the foals were monitored until ossification of the small tarsal bones was complete. The rate of ossification varied, and it seemed to be affected by the general health of the foal and by its weight-bearing. In two foals the pattern of ossification was markedly irregular and several ossifying foci were often found within the bones. Ultrasonography was found to be a practical method for monitoring the changes in the outline and echogenity of the bones in the distal tarsal area. Radiography confirmed the ultrasonographic findings and was necessary for evaluating the internal structure of the bones.     

Anatomo-radiographic Study on the Osteogenesis of Carpal and Tarsal Bones in Horse Fetus

The aim of this study is to point out the time of appearance of the carpal and tarsal bones in the fetal horse, considering an estimated fetal age, to follow their morphological development through to birth, and to characterize possible abnormal shape and/or delay of their ossification. The right carpal and tarsal region of 140 equine fetuses of both sexes (71 males, 69 females) and different ages (from 70 to 340 days of gestation) were examined radiographically in order to identify the sites of ossification from their earliest appearance. The times of appearance of the sites of ossification of the carpal bones are chronologically stated for each bone.     

Prolonged gestation in a Holstein cow: adenohypophyseal aplasia and skeletal pathology in the offspring

A Holstein fetus was delivered by Caesarean section at a gestational age of 441 days. The pituitary pars distalis was aplastic and the adrenal and thyroid glands were severely hypoplastic. Arrested or retarded cartilage cell maturation resulted in absence or minimal development of epiphyseal ossification centers, delayed ossification of carpal bones, and arrest of longitudinal growth of bones. The pathophysiology of prolonged gestation and of skeletal pathology is discussed.     

A system of grading ossification in limbs of foals to assist in radiologic interpretation.

Tetracycline-labeled bones of 23 foals from 52 to 104 days old were sectioned and macroscopically examined to assess the extent of ossification or fusion of ossification centers. A grading system was devised with which to record information about the ossification centers and growth plates. The objective was to define anatomic standards which could contribute toward obtaining an accurate radiologic interpretation. Labeled limb bones of 3 neonatal foals were similarly treated, but grading of these was limited to the consideration of whether each site was still cartilaginous or had commenced to ossify.     

Musculoskeletal disorders in neonatal foals

Angular limb deformities are not uncommon in foals. Mild angular deviation due to laxity of supporting soft tissues often resolves spontaneously. However, external splinting or casting may be needed in severe cases or in those that do not resolve. When incomplete ossification of carpal or tarsal bones is the cause of the limb deformity, external support is mandatory to prevent further deformation and abnormal development of the bones. When epiphyseal and metaphyseal abnormalities cause axial deviation, surgical intervention is usually necessary. Circumferential periosteal transection and/or transphyseal bridging are methods used. The choice is dictated by the type and severity of the deformity. Flexor contractures of the forelimb vary greatly in degree and joints affected. Physical therapy combined with intermittent splint application is often successful, but surgical intervention may be necessary in unresponsive cases. Flexor tendon laxity is usually self-correcting but physical therapy, restricted exercise, and splinting may be needed. Rotational abnormalities are easier to correct in the forelimbs than in the hind limbs. Correction is usually accomplished by frequent corrective hoof trimming. Miscellaneous anomalies of the musculoskeletal system may sometimes be amenable to surgical correction, although the potential disadvantages must be carefully considered. Septic arthritis is a frequent sequela to neonatal septicemia and must be treated aggressively and early in its development. Appropriate systemic antibiotics, joint lavage, and rest are indicated. Neonatal osteomyelitis has a poor prognosis and requires prompt, vigorous therapy; even then, growth anomalies of the limb or contiguous septic arthritis may develop and further worsen the prognosis. Early accurate diagnosis and prompt appropriate therapy are vital in treating musculoskeletal disorders in foals, especially when a successful outcome is judged by the animal becoming a functional athlete.     

The onset and consequences of tarsal bone fractures in foals

Fractures of the central tarsal and/or third tarsal bones involving both limbs of six foals are described. Five of the subjects were born either premature or of twin pregnancies. Fractures occurred in the neonatal period and coincided with disablement. Features of behaviour, posture and gait are described, together with gross radiographic findings, bone ash determination and blood chemistry. Lesions observed on the artitular faces of tarsal bones recovered from adult horses may have originated during the neonatal period.     

The onset and consequences of tarsal bone fractures in foals

Fractures of the central tarsal and/or third tarsal bones involving both limbs of six foals are described. Five of the subjects were born either premature or of twin pregnancies. Fractures occurred in the neonatal period and coincided with disablement. Features of behaviour, posture and gait are described, together with gross radiographic findings, bone ash determination and blood chemistry. Lesions observed on the articular faces of tarsal bones recovered from adult horses may have originated during the neonatal-period.     

Tarsal osteomyelitis in foals

Nine foals with haematogenous osteomyelitis of the tarsal bones were studied clinically, radiologically and pathologically. Clinical examination, including aspiration of articular or periarticular effusions in the tarsal area, and radiological study provide definitive diagnosis in most cases.     

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.     

Carpal and fetlock conformation of the juvenile Thoroughbred from birth to yearling auction age

REASONS FOR PERFORMING STUDY: There is little information available about conformational changes in the forelimbs of growing foals. OBJECTIVES: To describe the conformation of the carpus and fetlock of Thoroughbred foals from birth to yearling sale age. METHODS: Subjective assessments of the fetlock and carpal conformation of 119 Thoroughbred foals were made within the first month of life and then at 30 day intervals until at least age 120 days. At least 70 subjects were examined further at 60 day intervals until September of their second year. Conformation grades are reported for 5 age groups: first 7 days and at a mean of 46, 176, 362 and 525 days. The conformation of all available sires and dams of subjects was also graded. RESULTS: All subjects demonstrated carpal deviations, such as valgus, outward rotation and offset, and approximately 30% had fetlock deviations. Heavier birth weights were associated with carpal offset and fetlock inward conformation at most ages, and heavier yearlings were more likely to be carpal valgus. The carpal conformation of the sire (offset and outward rotation) was associated with similar yearling carpal conformation. During the study period, the carpal conformation of Thoroughbred foals became less valgus and more offset. Fetlock conformation became more inwardly deviated during the first 6 months of the study. CONCLUSIONS: Carpal and fetlock conformation change greatly in Thoroughbred foals up to age 18 months. The phenotype of the sire can be associated with yearling carpal conformation and bodyweight, particularly at birth and as yearlings, is associated with yearling fetlock and carpal conformation. POTENTIAL RELEVANCE: New factors associated with forelimb conformational deviations have been identified that may help breeders better to manage young racing stock.     

The ossification of the pectoral girdle and wing skeleton of the quail (Coturnix coturnix japonica)

The onset of ossification centres of the pectoral girdle and wing skeleton of the quail (Coturnix coturnix japonica) has been studied in embryos and juvenile birds, which were sampled daily from the 4th day of incubation up to the 12th day after hatching. Specimens, which were cleared and were stained with Alcian Blue and Alizarin Red S, were examined at the stereomicroscope. The furcula ossified with intramembranous ossification at the 7th day of incubation. The first centres of perichondral ossification in the scapula and the coracoid bones were observed at the 7th day of incubation. In the humerus, radius and ulna, perichondral ossification was observed at the 6th day of incubation. The carpal bones were ossified between the 8th and 10th day of the post-hatching period. The 2nd metacarpal bone began to ossify at the 6th day of the post-hatching period, whereas the 3rd and 4th metacarpal bones were ossified at the 7th day of incubation. At the 9th day of incubation, ossification was observed in the 1st phalanx of the alular digit and in the phalanges of the major digit. The 2nd phalanx of the alular digit began to ossify at the 12th, whereas the phalanx of the minor digit at the 14th day of incubation. The data presented here provide useful baseline information on the normal sequential pattern of ossification in the pectoral girdle and wing skeleton in this species.     

Retrospective study of 108 foals with septic osteomyelitis

Objective   To determine the clinical characteristics, short-term outcome and future athletic performance of foals with septic osteomyelitis.
Design   Retrospective clinical study of 108 Thoroughbred foals with radiographic evidence of bone infection that were presented at the Scone Veterinary Hospital between August 1995 and December 2001. Medical records were reviewed and information concerning signalment, the clinical, laboratory and radiographic findings, treatment and outcome was obtained. Racing records were obtained and evaluated for surviving foals that had reached racing age.
Results   Mean age of foals at initial evaluation was 39 days (range 1–180 days); 21 foals had multiple radiographic bone lesions (19.4%), and 76 had concurrent septic arthritis (70.4%). The most frequently affected bones were the femur, tibia and distal phalanx. In total, 87 foals were discharged from the hospital (80.6%), 79 survived long-term to reach racing age and 52 raced (65.8%). Overall, 48% (52/108) of the foals treated for osteomyelitis raced. Foals less than 30 days of age at the time of diagnosis, critically ill foals and those with multiple bones or joints affected were significantly less likely to be discharged from hospital. Multiple septic joints, but not multiple bone involvement, had an unfavourable prognosis for racing.
Conclusions   The prognosis for survival of foals with septic osteomyelitis or osteitis is favourable. Multiple bone or joint involvement is an important short-term prognostic indicator; however, the involvement of multiple joints, but not multiple infected bones, is associated with an unfavourable prognosis for racing.     

Equine gestational length and location: is there more that the research could be telling us?

Clear definitions of ‘normal’ equine gestation length (GL) are elusive, with GL being subject to a considerable number of internal and external variables that have confounded interpretation and estimation of GL for over 50 years. Consequently, the mean GL of 340 days first established by Rossdale in 1967 for Thoroughbred horses in northern Europe continues to be the benchmark value referenced by veterinarians, breeders and researchers worldwide. Application of a 95% confidence limit to reported GL range values indicates a possible connection between geographic location and GL. Improved knowledge of this variable may help in assessing the degree of the neonate’s prematurity and dysmaturity at or soon after birth, and identification of conditions such as incomplete ossification of the carpal and tarsal bones. Associated pathologies such as bone malformation and fracture, angular limb deformity and degenerative joint disease can cause chronic unsoundness, rendering horses unsuitable for athletic purpose and shortening ridden careers. This review will examine both the factors contributing to GL variation and the published data to determine whether there is potential to refine our understanding of GL by establishing a more accurate and regionally relevant GL range based on a 95% confidence limit. This may benefit both equine industry economics and equine welfare by improving early identification of skeletally immature neonates, so that appropriate intervention may be considered.     

Radiological Evaluation of Juvenile osteochondral Conditions in Brazilian Warmblood Horse

The term juvenile osteochondral condition (JOCC) has been used to identify developmental changes in the growth plates. The condition is characterized by a set of changes with similar pathogenesis that affect the immature skeleton and joints of growing foals. The aim of the current study is to investigate the prevalence and degree of severity of osteochondral changes in Brazilian warmblood (BW) foals in two farms in the south of Brazil. Radiological evaluation was applied to the metacarpophalangeal (MCP), carpal (C), metatarsophalangeal (MTP), tarsal (T), and femorotibiopatellar (FTP) joints of 90 foals (47 females and 43 males) in the age group 16–36 months. The evaluation was made before the animals started their athlete performance. Changes were classified as a degree of severity 0 to 4. Changes were diagnosed in 56 foals (58%) that had 105 affected joints. Thirty-three (59%) out of the 56 animals had changes in more than one joint; 57% (19/33) of them had bilateral changes. MTP and MCP were the joints with the most severe changes, respectively (severity 2 and 3), followed by FTP, T, and C. Osteochondral fragments (59%), tarsal arthropathies (48%), irregularities and radiolucency in the FTP joint (7%), and subchondral cystic lesion in the FTP joint (1%), were the most observed changes. BW foals recorded the high prevalence of osteochondral alterations; although MTP and T were the most affected joints, MTP and MCP presented the most severe changes. The present study confirmed significant JOCC prevalence in BW. Further studies should be carried out in different properties.     

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.     

RADIOGRAPHIC AND PATHOLOGIC FEATURES OF OSTEOPETROSIS IN TWO PERUVIAN PASO FOALS

The radiographic and pathologic findings of two Peruvian Paso foals with osteopetrosis are described. Both foals, one male and one female, presented with respiratory difficulty, brachygnathia and failure to rise after birth. Both foals were mildly anemic, hypogammaglobulinemic and had elevations in serum alkaline phosphatase. Increased medullary bone opacity was noted on radiographs of the extremities, spine and skull in both foals. A lack of normal cortical:medullary bone distinction was evident radiographically. The medullary primary spongiosa appeared to run in parallel columns away from the physes of all long bones and the vertebrae. This created a distinctive hour glass appearance to the osteopetrotic bones. One foal developed a bacterial pneumonia. Both foals were euthanized due to failure to thrive. Histopathology and electron microscopy documented these foals to have normal osteoclastic numbers but lack normal ruffled borders, lack of a clear zone and normal lysosomal numbers indicative of cellular dysfunction. These clinical, radiographic and pathologic findings are similar to the juvenile, lethal autosomal recessive form of osteopetrosis described in humans. Osteopetrosis has not been previously described in a female foal.     

SILVER IMPREGNATION IN SITU

In evaluating radiographs of the limb joints and head, students encounter difficulty where superimposition occurs. By replacing calcium with silver salts in the bone, enhanced radiopacity can be produced. In this study, silver impregnation was used to increase the radiopacity of individual carpal and tarsal bones, selected bones of the skull and the sinuses, and guttural pouch of the horse. This provides an interpretation aid for teaching radiographic anatomy of these regions.