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).     

Physeal form of the longbones of the foal

The possible relationship between physeal diseases and physeal form prompted investigation of change in steepness of the physis in young foals. The distal and proximal aspects of the longbones were sawn sagittally in the right and frontally in the left bones. The slabs were washed to remove saw debris, arranged in order and inspected. The proximal physes had a flat or gently arched form, without obvious inclination. In the distal physes there were distinct inclinations. Inspection of an identical slab from the medial aspect of the distal radius of two series of foals of different breeds showed that the degree of inclination of the physis with respect to the long axis of the bone increased with age. In a further series of foals, the angle of inclination was measured from radiographs of identical sagittal and frontal slabs of the distal radius. A line drawn through the secondary spongiosa was produced to intersect a line drawn along the physis where it was mostly steeply inclined, and the angle measured. The angle decreased (physeal inclination increased) with increasing age, up to 35–90 days. The steepness in the lateral aspect of the physis was similar to that in the medial aspect, although evident in a different plane.     

Hypertrophic osteodystrophy of the proximal humerus in two dogs

Two dogs, 3 and 6 months of age, were presented with painful, swollen shoulder and carpal joints; reluctance to stand; and pyrexia. Radiographs in both cases revealed an irregular lucent zone in the metaphysis of the proximal humerus, parallel and adjacent to the physis. The same lucent zone was also evident in the physes of the distal radial and ulnar metaphyses. Clinical signs and radiographs were consistent with hypertrophic osteodystrophy. Clinical signs resolved in both dogs with administration of carprofen, tramadol, and intravenous fluids. No signs of recurrence were reported at 3-month follow-ups.     

The incidence of bone lesions in the carpal and tarsal regions and the rate of physeal closure in weanling quarter horses

Sixty weanlings were maintained in dry lots without forced exercise and individually fed a diet consisting of 25% Bermudagrass hay and 75% balanced concentrate twice dally. Radiographs of the carpus, metacarpus and first phalanx, and other radiographs of the tarsal region, were taken initially at approximately 180 d of age and at approximately 236, 292 and 348 d of age. The radiographs were evaluated for the presence or absence of subchondral and/or cystic lesions in the carpal and tarsal regions and for closure of physes of the distal third metacarpus and proximal first phalanx. Physeal scores were: 1 = open; 2 -- partially closed; 3 = closed. Only 1.7% of the horses had subehondral lesions in the carpal region at 180 d, and none had those lesions at 236, 292 or 348 d. There was a 3.3% incidence of subchondral lesions of the tarsus at 180, 236 and 292 d, but only 1.7% at 348 d. Cystic lesions of the carpus were evident in 13.3% of the horses at 180 d, 16.7% at 236 d and 18.3% at 292 and 348 d. None of the hrses had cystic lesions oftbe tarsus at 180, 236 or 348 d, but 1.7% had them at 292 d. Physeal closure scores for the distal metacarpus averaged 1.5 and 2.6 at 180 and 236 d, respectively. At 292 and 348 d, all of the distal metacarpi were closed. Physeal closure scores for the proximal first phalanges were 1.5, 2.6 and 2.9 at 180,     

Physeal Fractures in the Horse:I. Classification and Incidence

Seventy appendicular skeletal physeal fractures in 67 horses were reviewed and classified using the Salter-Harris classification. All the horses were less than 2 years old (mean age at injury 6.2 months). The mean age at injury for pressure physeal fractures (5.2 months) was significantly less (p < .05) than for traction physeal fractures (8.3 months). The majority (67.2%) of the horses were female. Forty-eight (69%) pressure physes and 22 (31%) traction physes were affected. The most common pressure and traction physeal fracture sites were the proximal femoral physis and the proximal ulnar physis, respectively. Sixty-seven physeal fractures were classified: 14 as Type I (20.9%), 42 as Type II (62.7%), six as Type III (8.9%), and five as Type IV (7.5%). Forty-six pressure physeal fractures were classified: six as Type I (13.0%), 30 as Type II (65.2%), five as Type Hi (10.9%), and 5 as Type IV (10.9%).     

Diffusion of radiodense contrast medium after perineural injection of the palmar digital nerves

Limited information exists on distribution of local anaesthetic solution following palmar digital nerve blocks. The aim of this study was to demonstrate potential distribution of local anaesthetic solution following perineural injection of the palmar digital nerves using 2 different volumes of contrast medium and 2 different injections sites. Twelve mature horses were used. Perineural injection of the palmar digital nerves were performed at the level of or 2 cm proximal to the proximal aspect of the ipsilateral ungular cartilage, using 1.5 or 2.5 ml radiopaque contrast medium. In total, 96 injections were performed. Four standard radiographic views of the pastern were obtained immediately after injections and 10 and 20 min later. Images were analysed subjectively and objectively. After distal injections, the contrast medium was more localised around the injection site; after proximal injections the contrast patch had greater proximal–distal length. The greatest proximal diffusion was to 31.7% of the length of the proximal phalanx (from the level of the proximal interphalangeal joint) after distal injections and to 70% after proximal injections. The larger volume resulted in significantly greater proximal diffusion than the smaller volume at the distal, but not at the proximal injection site (P<0.01). There was significant proximal diffusion with time after proximal and distal injections (P<0.01). In most limbs, numerous radiopaque lines of various thickness extended proximally from the contrast patches; subjectively, their number and thickness were greater at the distal injection site. In conclusion, palmar digital nerve blocks at the level of the ungular cartilage using ≤2.5 ml local anaesthetic solution may improve proximal interphalangeal joint and pastern region pain. If using a more proximal site, distal fetlock region pain may be improved. Due to diffusion into lymphatic vessels, too small a volume at the distal injection site may not provide sufficient analgesia.     

Morphological and Imaging Evaluation of the Metacarpophalangeal and Metatarsophalangeal Joints in Healthy and Lame Donkeys

The donkey is of socio-economic value yet imaging techniques in both healthy and abnormal limbs are a limiting factor in research and medicine. The objective was to determine anatomical features of both healthy and clinically abnormal donkey metacarpophalangeal and metatarsophalangeal joints (n = 13) using anatomical dissection, casting, X-ray and computed tomography. The joint capsule contained two palmar/plantar and two dorsal recesses. The proximal–palmar or plantar recess was larger than the distodorsal recess and potential sites of approaches to the recesses were determined. Soft tissue structures were distinguished using computed tomography at 300 mA, which was superior to 120 mA. This methodology gave better assessments of the synovial tendon sheath, joint recesses, and cruciate, collateral, and short sesamoidean ligaments. Computed tomography provided outstanding discrimination between the cortex and medulla of the third metacarpal, the proximal sesamoid bones, the proximal phalanx, and excellent details of the osseous structures. Although the joints appeared free from exostosis using X-ray; the position and extension of exostosis in pathologically affected donkeys (a novel finding) were revealed using computed tomography with 300 mA in comparison to 120 mA. The study also provided an anatomical record of the metacarpophalangeal and metatarsophalangeal joints using the latest technology, which could impact on clinical situations including anesthesia injection sites.     

A XERORADIOGRAPHIC STUDY OF THE DEVELOPING EQUINE FOREDIGIT AND METACARPOPHALANGEAL REGION FROM BIRTH TO SIX 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 meta-carpophalangeal regions of six Quarter Horse foals were radiographed at one day of age and at two-week intervals until the foals were six weeks old. The foals were then radiographed at four-week intervals until they were 12 months old. This report deals specifically with the first six months of postnatal development. 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 for each examination. The foals were weighed and measured at the withers immediately prior to each examination. Representative xeroradiographs were selected and appropriately labeled to demonstrate normal radio-graphic anatomy of these regions. First radiographic appearance of distal epiphyseal ossification in metacarpal 2 and metacarpal 4 was extremely variable and ranged from four to 38 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). When xeroradiographic physeal closure times were compared with scintigraphic closure times from a companion study, results correlated very well. A crena marginis solearis was observed in ten of 12 forelimbs (83.3%); its first radiographic appearance ranged from four to 22 weeks (mean = 11–12 weeks). A consistent groove in the hoof wall, which formed near the time of birth and moved distally at about 3 mm per week, was noted. The groove's distance from the proximal hoof border may be useful in age estimation of foals less than 18–20 weeks old.     

Effects of Live Yeast (Saccharomyces cerevisiae Strain 1026) Supplementation on the Closure of Articular Growth Plates in Quarter Horse Foals

To avoid osteoarticular injury and to minimize farm losses in animal use and sales, breaking in young horses is ideally done as soon as growth plates have closed. An experiment was performed to determine whether dietary live yeast could shorten the time for growth plate closure. Twenty-four female Quarter Horse foals, 8 months of age, were allotted to two treatment groups (12 animals each) in a completely randomized experimental design. Horses were fed 0 or 20 g live yeast daily from 8 to 24 months of age. Diets were regular for a stud farm in the area of the study in Argentina. Foals at 8 months of age had a low baseline calcium urinary fractional excretion compatible with a primary calcium-deficient diet for this age in Argentina. Growth plate closure was evaluated by dorsum–palmar radiographs at baseline. A second evaluation was performed when foals were 12 months of age and a third evaluation when foals were 24 months of age. Blood and urine were sampled simultaneously at the same intervals to evaluate bone and mineral metabolism parameters (serum phosphorus, calcium, magnesium; alkaline phosphatase; and hydroxyproline). Calcium, magnesium, and phosphorus urinary fractional excretions were also calculated. Closure scales of distal radius growth plate data were compared using Wilcoxon test and bone markers were compared using Student t-test. Baseline radiological evaluation of growth plates showed that in 84% of foals, the distal metacarpi were either half closed or fully closed at 8 months; therefore, subsequent evaluations were limited to the distal radius. After 4 months of supplementation with live yeast at 12 months of age, a positive but nonsignificant elevation in calcium urinary fractional excretion was observed. At 24 months of age, radiographs showed a nonsignificant but positive effect in the live yeast group, with more than 50% of foals having closed distal radius growth plates. Although bone markers at 24 months of age did not differ (P > .05) between groups, some individual horses showed a positive effect with yeast supplementation.     

RADIOGRAPHIC APPEARANCE OF THE NAVICULAR BONE AND DISTAL INTERPHALANGEAL JOINT AND THEIR RELATIONSHIP WITH OSSIFICATION OF THE COLLATERAL CARTILAGES OF THE DISTAL PHALANX IN FINNHORSE CADAVER FOREFEET

Radiographic findings in the navicular bone and distal interphalangeal joint as well as the ossification status of the collateral cartilages of the distal phalanx were evaluated in 100 Finnhorse cadaver forefeet. The most common shapes of the proximal articular margin of the navicular bone were convex and straight. Remodeling of the navicular bone was common, especially on the lateral extremity. No bony fragments were identified at the distal flexor margin even though this area appeared irregular in several feet. Several large, rounded or lollipop-shaped synovial invaginations were identified in only six feet. The thickness of the flexor cortex varied considerably, and the corticomedullary junction was uni- or bilaterally indistinct in nine feet. The shape of the sagittal ridge of the flexor cortex was commonly flat but varied. It appeared locally irregular or indistinct in 17 feet, but changes elsewhere along the flexor cortex were rare. Osteophytosis on the dorsal and palmar margins of the distal interphalangeal joint and entheseophytosis on the dorsal aspect of the middle phalanx and on the extensor process of the distal phalanx were common. "Possibly significant" ossification of the collateral cartilages (high side-bones or separate centers of ossification) was present in 36 feet; all grades of ossification in the proximal/ palmaroproximal direction as well as palmar ossification were seen. A statistically significant relationship was found between entheseophytosis on the proximal flexor margin of the navicular bone and "possibly significant" ossification. Osteophytosis on the palmarodistal margin of the middle phalanx was more common in feet with a relatively long distal phalanx, suggestive of palmar ossification. Radiographic changes in the navicular bone or in the distal interphalangeal joint did not otherwise appear to be associated with ossification of the collateral cartilages of the distal phalanx in Finnhorses.     

Radius fractures in the horse: a retrospective study of 47 cases

The case records, radiographs and treatment results of 47 consecutive equine radius fractures presented to The Ohio State University Veterinary Hospital from 1975 to 1985 were examined retrospectively. Chip fractures and incomplete fractures were not considered. Both diaphyseal fractures and fractures involving the physes were included. Diaphyseal fractures were placed into three major categories: comminuted, oblique and transverse; and subclassified as proximal, mid-diaphyseal, or distal. Fractures involving a physis were classified using the Salter-Harris classification system. The horses ranged in age from one day to 19 years old. Nineteen of the patients were destroyed humanely on presentation, and 28 were treated. Twenty-four of the 28 fractures treated were repaired by open reduction and internal fixation. Success rate was related to the age of the horse and the type of fracture. Adult radius fractures have a poor prognosis. Most fractures in foals are either physeal fractures or transverse or oblique diaphyseal fractures and have an excellent to good prognosis when repaired adequately.     

Cryosurgical Epiphysiodesis in the Dog

Transphyseal freezing of the canine distal femur was evaluated to determine its effect on physeal growth and closure. A specially designed cryoprobe was used to freeze the distal right femoral physis in 17 immature dogs. The left distal femoral physis was sham operated to serve as a control. Dogs were radiographed weekly and euthanized from 2 days to 8 weeks following surgery. The rate of long bone growth decreased in all dogs, and the physis was closed at 6 to 8 weeks.
Histologic studies on the distal femoral physes revealed that immediately after freezing, there was extensive hemorrhage in the epiphysis and metaphysis with disruption of the physis. Inflammation and death of the physeal cartilage followed. Blood vessels invaded the physis, and eventually bone was formed between the epiphysis and metaphysis, resulting in complete and premature physeal closure.     

Pathological fracture through a subchondral bone cyst in the proximal phalanx of a horse

A 12‐year‐old Morgan broodmare presented for a nonweightbearing right forelimb lameness. Radiography and computed tomography confirmed the presence of a pathological fracture of the proximal first phalanx through a large subchondral bone cyst (SBC) in the right forelimb and a large SBC in the proximal first phalanx of the left forelimb. Surgical repair of the large palmar medial eminence fracture of the proximal first phalanx fracture was performed using bone screws placed in lag fashion placed through stab incisions after debridement and bone grafting of the SBCs. Approximately 6 months after surgery the mare was ambulating comfortably at pasture. This case report describes a fracture through a large subchondral bone cyst in a horse despite chronicity and ongoing bone remodelling. Careful consideration regarding exercise or use should be considered in horses with large SBCs.     

FRACTURES OF THE DISTAL PHALANX AND ASSOCIATED SOFT TISSUE AND OSSEOUS ABNORMALITIES IN 22 HORSES WITH OSSIFIED SCLEROTIC UNGUAL CARTILAGES DIAGNOSED WITH MAGNETIC RESONANCE IMAGING

Ungual cartilage ossification in the forelimb is a common finding in horses. Subtle abnormalities associated with the ungual cartilages can be difficult to identify on radiographs. Magnetic resonance (MR) imaging findings of 22 horses (23 forelimbs) with a fracture of the distal phalanx and ossified ungual cartilage were characterized and graded. All horses had a forelimb fracture. Eleven involved a left forelimb (seven medial; four lateral), and 12 involved a right forelimb (five medial; seven lateral). All fractures were nonarticular, simple in configuration, and nondisplaced. The fractures were oriented in an axial proximal to abaxial distal and palmar to dorsal direction, and extended from the base of the ossified ungual cartilage into the distal phalanx. The fracture involved the fossa of the collateral ligament on the distal phalanx in 17 of 23 limbs. The palmar process and ossified ungual cartilage was abnormally mineralized in all horses. Ligaments and soft tissues adjacent to the ossified ungual cartilages were affected in all horses. The routine site of fracture in this study at the base of the ossified ungual cartilage extending into the distal phalanx suggests a biomechanical cause or focal stress point from cycling. The ligamentous structures associated with the ungual cartilages were often affected, showed altered signal intensity as well as enlargement and were thought to be contributing to the lameness. In conclusion, ossified ungual cartilages may lead to fracture of the palmar process of the distal phalanx and injury of the ungual cartilage ligaments.     

RADIOGRAPHIC CHARACTERISTICS OF THE FORELIMB DISTAL PHALANX AND MICROSCOPIC MORPHOLOGY OF THE LATERAL PALMAR PROCESS IN FOALS 3–32 WEEKS OLD

Developmental morphology of the forelimb distal phalanges and lateral palmar processes of 9 Thoroughbred foals aged 3–32 weeks was assessed using radiography, microradiography and histology. For inclusion in the study, all distal phalanges had no pathologic radiographic abnormalities.
Vascular channels that are characteristically found in the dorsal region of the distal phalanx were not evident radiographically in the palmar process. The proximal and distal angles of the palmar processes were separated by a lucent line continuous with the incisure in foals only through 12 weeks of age. The distal phalanges were triangular-shaped in foals 3–12 weeks of age, and were oval-shaped in older foals.
The palmar aspect of the distal phalanx was the major contributor to growth of the distal phalanx in the sagittal plane, especially between 3 and 12 weeks of age. Growth of the lateral palmar process occurred through the means of endochondral ossification. The body and cortices of the lateral palmar process were composed of coarse cancellous bone. Porosity within the lateral palmar process was greater in regions sampled axial, compared to abaxial, to the parietal sulcus and did not change with age.
A fracture was identified microradiographically and/or histologically in 9 of 18 (50%) and 10 of 17 (59%), respectively, of the lateral palmar processes examined. The fracture line was consistently associated with the parietal sulcus on the dorsal cortical surface and was always immediately abaxial to the deep digital flexor tendon attachment. No age-related morphological changes of the lateral palmar processes were identified with microradiography or histological examinations.     

Variable locations of nutrient foramina of the proximal phalanx in forelimbs of Thoroughbreds

Bilateral metacarpophalangeal radiographs of 100 Thoroughbreds were examined for visualization and location of the major nutrient foramen of the proximal phalanx. The foramina were located on the dorsal or palmar aspects of the cortex or were not visible radiographically. Of the 100 horses, 60 had the same pattern in both forefeet. In the remaining 40 horses, the left and right proximal phalangeal foramina were asymmetric. Of the 200 proximal phalangeal foramina (100 horses), 53 were on the dorsal aspect of the cortex and 101 were on the palmar aspect of the cortex; 46 were not visible radiographically. Significant effect of age or gender could not be determined.     

Asynchronous growth of the canine radius and ulna: effects of retardation of longitudinal growth of the radius.

After 2,000 rads of x-radiation to the right distal radial physis of eight 70-day-old dogs, the longitudinal growth of the right radius was retarded 42.1% when compared with the growth of the nonirradiated left radius. Asynchronous growth of the right radius and ulna resulted. The gross and radiographic changes that occurred over the subsequent 75 days were described. Subluxation of the humeroradial and humeroulnar joints occurred and was first observed 31 days after irradiation. By 75 days after irradiation, the radius was puller 7.8 mm distally by the radioulnar ligament. However, subluxation of the humeroradial joint was minimized by accelerated growth from the proximal radial physis and articular cartilage. Acceleration of growth also occurred at the distal radial articular cartilage. Growth from the distal ulnar physis and styloid process was retarded. It was thus apparent that after retardation of growth from the distal radial physis, considerable adjustment occurred in the relationship between the radius and the ulna and also in growth from their other physes, which reduced the deleterious effects of the growth retardation.     

Diffusion of radiodense contrast medium after a mid‐pastern ring block

Diffusion of local anaesthetic solution after a mid‐pastern ring block has not previously been investigated. The aim of this study was to demonstrate potential distribution of local anaesthetic solution following injection of radiodense contrast medium as performed for a mid‐pastern ring block. Twelve mature horses were used and 1.5 ml radiodense contrast medium injected over the medial or lateral palmar digital nerve at the level of the proximal aspect of the ungular cartilages. A dorsal ring block was performed on the ipsilateral side, 1.5 cm proximal to the palpable palmar aspect of the proximal eminence of the middle phalanx, using 2 or 5 ml contrast medium. Both forelimbs were injected on 2 days (48 injections). Four standard radiographic views of the pastern were obtained immediately, 10 and 20 min after injections. Images were analysed subjectively and objectively. After dorsal injections, the contrast medium was distributed in a diffuse patch over the ipsilateral half of the proximal phalanx (P1), extending proximally over the half of the length of P1 in all limbs (greatest proximal extension: 89.0% of the length of P1 [from distal] after 2 ml, 94.2% after 5 ml). There was significant proximal diffusion in the first 10 min after injection and significant dorsal diffusion between all time points (P<0.01). There was significant positive association between injected volume and the proximal extension of the dorsal contrast patch (P = 0.01). The median dorsal diffusion was to the dorsal midline of P1; 5 ml contrast medium resulted in significantly greater dorsal diffusion than 2 ml (P<0.01). The dorsal and palmar contrast patches did not merge. In conclusion, diffusion to the proximal aspect of P1 following a mid‐pastern ring block may occur even if only 2 ml of local anaesthetic solution is used.     

Spontaneous femoral capital physeal fractures in adult cats: 26 cases (1996-2001)

OBJECTIVE: To determine clinical, radiographic, and histologic abnormalities in adult cats > 1 year old with spontaneous (ie, nontraumatic) femoral capital physeal fractures. DESIGN: Retrospective study. ANIMALS: 26 cats. PROCEDURE: Medical records of cats > 1 year old with femoral capital physeal fractures and no history of trauma were examined. RESULTS: Mean +/- SD age of the cats was 22.5 +/- 6.5 months. Twenty-five cats were neutered males. Mean weight of the cats was significantly greater than mean weight of a group of age- and sex-matched control cats. Of 16 cats for which age at the time of neutering was known, 14 had been neutered before 6 months of age. Nine cats had bilateral fractures. Severity of femoral neck osteolysis and sclerosis increased with increased duration of clinical signs. The contralateral femoral capital physis, distal femoral physes, and proximal tibial physes were radiographically open in 13 of 18,19 of 24, and 24 of 24 cats, respectively. Histologically, the epiphysis contained normal articular cartilage and bone, but attached growth plate cartilage lacked the normal columnar arrangement of chondrocytes. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that adult cats with spontaneous femoral capital physeal fractures were most likely to be heavier, neutered males with delayed physeal closure.