Foot pain and the elusive diagnosis

New information about foot anatomy, effects of local analgesia, and advances in diagnostic imaging (ultrasonography, nuclear scintigraphy, MRI, CT, and endoscopy) has opened the way for more specific diagnoses of lameness. New questions have been raised, however, and some older ideas are now in doubt. This article discusses some of these findings in the light of our own clinical experiences as they relate to diagnosis of the causes of foot pain.

Estimates of heritability for ossification of the cartilages of the front feet in the Finnhorse

REASONS FOR PERFORMING STUDY

Ossification of the cartilages in the foot is common in coldblooded horses, but prevalence as well as ossification pattern varies between breeds; research on estimation of heritability for the condition has been limited.

OBJECTIVES

Our purpose was to calculate estimates of 1) heritability for ossification parameters of the cartilages in the front feet of the Finnhorse and 2) genetic correlations between the different ossification parameters.

METHODS

Estimates of heritability for different ossification parameters of the cartilages in the front feet and of genetic correlations between different parameters were evaluated in data consisting of dorsopalmar radiographs of the front feet and pedigree up to the fourth generation of 964 Finnhorses (age > or = 2 years; 345 females and 619 males). Ossification at the base of the cartilages and total ossification, including separate centres of ossification, were graded 0-5 according to the most proximal point of ossification and the presence of separate centres of ossification was recorded separately. The data were analysed using a model including a fixed sex-age subclass effect and a random animal effect. Variance and covariance components were estimated with the restricted maximum likelihood (REML) method assuming an animal model.

RESULTS

Females had more ossification than males and this difference increased with age. The ossification in the medial cartilages progressed significantly with age in females but not in males. In the lateral cartilages, the increase in ossification with age was evident in both sexes. Separate centres of ossification were an incidental finding. Estimates of heritability for the ossification parameters varied slightly between the cartilages as well as between the front feet. For total ossification, the estimates of heritability varied between 0.31 (right lateral) and 0.50 (left medial) and were slightly higher for ossification at the base of the cartilages. High genetic correlations were found for total ossification between the medial and lateral cartilages in the foot and for parallel ossification parameters between the right and left foot.

CONCLUSIONS

The estimates of heritability were relatively high, and both cartilages and front feet have a similar genetic tendency to ossify.

POTENTIAL RELEVANCE

This information is useful in further studies assessing other factors contributing to the ossification process and also in the planning and modifying breeding programmes.

Collateral cartilage ossification of the distal phalanx in the Brazilian Jumper horse

Collateral cartilage ossification of the distal phalanx in the Brazilian Jumper horse is a common finding. The objective of this study was to evaluate the prevalence and the degree of ossification of the collateral cartilages of the distal phalanx in Brazilian Jumper horses. In an analysis of 652 collateral cartilages from the front feet of 163 horses, 93% of these cartilages had collateral cartilage ossification (P < 0.005), and 7% of these cartilages did not have any type of ossification. In ossified cartilages, 86.4% had ossification beginning from the base, and 6.6% had a separate center of ossification.

Most dogs with medullary rim sign on ultrasonography have no demonstrable renal dysfunction

The medullary rim sign is a distinct hyperechoic line in the renal medulla parallel to the corticomedullary junction that has been reported in dogs with a variety of renal diseases. To examine the association between medullary rim sign and renal disease, the medical records of thirty-two dogs that had medullary rim sign were reviewed retrospectively. Eighteen dogs (56%) had no evidence of renal dysfunction; 14 (44%) had clinicopathological evidence of renal disease, including 6 (19%) that had hypercalcemic nephropathy. Most dogs (72%) in which medullary rim sign was the only ultrasonographic finding affecting the kidneys had no evidence of renal dysfunction. In contrast, 78% dogs that had medullary rim sign and other renal signs (reduced size, increased medullary echogenicity, and pyelectasia) had renal disease. On the basis of this study, the medullary rim sign appears to be a non-specific ultrasonographic sign; however, the possibility cannot be excluded that is a sentinel sign of subclinical renal disease.

Ossification of the cartilages in the front feet of young Norwegian coldblooded horses

The purpose of the present study was to evaluate the nature of ossification of the cartilages in the front feet of young, about 2-year-old Norwegian coldblooded horses, and to compare offspring of different sires in this respect. Dorsopalmar radiographs of the front feet of 392 horses (187 female and 205 male) were evaluated for ossification at the base of the cartilage and for separate centres of ossification. The horses were offspring of 45 different sires. Ossification extending above the navicular bone and separate centres of ossification were considered as significant. Minimal to mild ossification at the base of the cartilages was commonly seen, and significant ossification was present in one or more of the cartilages in 11.5% of the horses. The lateral compared to medial cartilages had more ossification and females had more ossification and more separate centres of ossification than males. The prevalence of horses with significant ossifications was significantly higher (46.3%) among offspring of one frequently used stallion than in the group consisting of offspring of 4 other popular stallions (3.5%) and in another group consisting of offspring of other, less frequently used stallions (9.6%). Ossification of the cartilages is considered to have a hereditary background in Norwegian coldblooded horses.

Subclinical CT abnormalities in the lumbosacral spine of older large-breed dogs

Computed tomography (CT) of the L5-S3 vertebral levels was performed in six, large-breed dogs presented for problems unrelated to the lumbosacral spine. All dogs were asymptomatic for lumbosacral stenosis on neurologic examination. Breeds included German Shepherd, Golden Retriever, Boxermix and Belgian Malinois. Ages ranged from 5-12 years. Five out of six dogs exhibited CT abnormalities. Among the 18 disc levels examined, the most common findings were idiopathic stenosis, loss of vertebral canal epidural fat, and nerve tissue displacement. Less common abnormalities were vertebral canal or foraminal bone proliferation, loss of intervertebral foramen fat, vertebral canal disc bulging, degenerative articular process joint disease, transitional vertebra, dural ossification, foraminal disc bulging, Schmorl's nodes, calcified extruded disc fragment, and sacroiliac joint osteophytes. Vertebral subluxation was absent in all dogs. Findings indicate that some lumbosacral CT abnormalities may be clinically insignificant, especially in older dogs.

Oral malignant melanoma with osteoid formation in a dog

Melanomas are the most frequent malignant neoplasms of the oral cavity of dogs. Osteogenic melanoma is a rare variant of melanoma that has been described in humans but not in animals. We describe a case of malignant melanoma with bone production affecting the gingiva of a 12-year-old Miniature Dachshund dog. The tumor was a round, lightly pigmented mass that measured 1 cm in diameter and was hard to cut. Histologically, the tumor was composed of nests and lobules of anaplastic, round, melanin-containing cells supported by a stroma displaying abundant osteoid matrix. Many of the neoplastic melanocytic cells were in close contact with the osteoid trabeculae. Immunohistochemical tests revealed that the neoplastic cells were immunoreactive for S-100 and vimentin and showed no staining with cytokeratin. The animal had a local recurrence of the tumor 3 months after the initial excision. This is the first case of malignant melanoma with osteoid formation reported in animals.

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 sidebones 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.

Evaluation of the variably ossified collateral cartilages of the distal phalanx and adjacent anatomic structures in the Finnhorse with computed tomography and magnetic resonance imaging

Six Finnhorse cadaver forefeet were selected to represent radiographically different types and grades of ossification of the collateral cartilages of the distal phalanx. These cartilages and adjacent tissues were evaluated with computed tomography (CT) and high field magnetic resonance imaging (MRI). In CT the internal structure of the cartilages was consistent, but in MRI some differences were noted. The shape of the collateral cartilages and their ligamentous attachments varied. The border between ossified and non-ossified cartilage appeared distinct, with considerable variation in the extent of the ossified area in regard to the cross-sectional area of the cartilage. Ossification originating from the palmar processes and extending in the proximal/palmaroproximal direction, without separate centers of ossification, generally appeared smooth and inactive. Palmar ossification followed the irregular shape of the cartilage. Separate centers of ossification had a medullary cavity or were sclerotic. Presence of a medullary cavity or sclerosis were also found at the base of the cartilages. The incomplete fusion lines between separate centres of ossification and the ossified base of the cartilage varied from congruent and inactive to reactive with marked sclerosis, flared margins and parachondral changes. Incomplete fusion may be clinically significant. Local conformational adaptations of the hoof were also documented with extensive ossification of the collateral cartilage.

Effects of sex and age on the ossification of the collateral cartilages of the distal phalanx of the Finnhorse and the relationships between ossification and body size and type of horse

The ossification of the collateral cartilages of the distal phalanx was evaluated in dorsopalmar radiographs of the front feet of 202 Finnhorses (101 females and 101 males, aged six months to 20 years) with reference to the sex, age, body measurements and type of horse. Ossification was more common and more extensive in females than in males from about two years of age. In females, the lateral cartilages were significantly more ossified than the medial cartilages; in males, ossification was more symmetrical in the cartilages of each foot. The amount of ossification increased rapidly during the second and third years of life, and more slowly in adults. The low positive correlation coefficients between ossification and different body measurements of the horse suggested that there was more ossification in large horses, and the correlation between chest-width in adults and the extent of ossification was statistically significant. The working type of horses showed slightly more ossification than trotters and riding horses. Ossification variables, which included ossification at both the base of the cartilage and at the possible separate centres of ossification (total ossification of individual cartilages and "possibly significant' ossification in the front feet), were found to be most satisfactory for expressing the extent of ossification.

Effusive-constrictive pericardial disease secondary to osseous metaplasia of the pericardium in a dog

Osseous metaplasia of the pericardium causing effusive-constrictive pericardial disease has not, to our knowledge, been reported in dogs. Clinical signs of right-sided congestive heart failure prompted examination of the dog of this report. Documented causes of constrictive pericardial disease in dogs include trauma and actinomycotic, mycobacterial, and fungal infections. These causes were ruled out in this dog. Immune-mediated disorders, as have been reported in people, also were considered unlikely on the basis of test results. It was concluded that this dog had idiopathic osseous metaplasia of the pericardium and pleura. Signs of right-sided congestive heart failure resolved after subtotal pericardiectomy was performed.

Ameloblastoma with prominent ossification in the mandible of a dog

A rare case of ameloblastoma with prominent stromal ossification in an 8-year-old female dog was studied. A bony mass recurred rapidly in the right mandible at the first molar region. Histopathologic examination revealed the lesion to be an atypical variant of ameloblastoma. Epithelial cells showed marked cell atypia, and mitotic figures were rather common. The collagenous stroma was abundant, with prominent formation of bone trabecular rimmed by active osteoblasts. The tumor was highly proliferative and aggressive, and thought to be malignant in nature.

[Tendovaginitis of the musculi biceps brachii in dogs]

Successful surgical correction of bicipital tenovaginitis and extensive new bone formation in the shoulder joint of an 8-year-old dog is described. Radiography and computed tomography revealed severe arthrosis of the shoulder joint with osteophyte formation encircling the bicipital tendon in the intertubercular groove. The diagnostic approach and therapy are described and discussed with reference to recent literature.

Mineralized paraprostatic cyst in a dog

Images

Radiographic evaluation of ossification of the collateral cartilages of the third phalanx in Finnhorses

Of 462 Finnhorses (age 1-20 years) evaluated and graded (scale 0-5) radiographically for ossification of the collateral cartilages of the 3rd phalanx of the front feet, 22.9% were totally free from sidebones (Grade 0), and 49.1% had minimal or mild ossification (Grade 1 or 2) at the base of 1 or more of the cartilages. Moderate ossification (Grade 3) was present in 10.2% of the horses, whereas ossification was advanced (Grade 4) or extensive (Grade 5) in 17.8%. In most horses > 1 cartilage was affected and 7.6% of the horses had separate centres of ossification in 1 or more of the cartilages. Large sidebones and separate centres of ossification were more common in females than in males (P < 0.001). The incidence of large sidebones was lower in young females (1-3 years) than in mares 4-6 years of age (P < 0.05), but did not increase significantly with age when young horses, 4-6 years of age, were compared with older ones. Grade 4 and 5 sidebones as well as separate centres of ossification were more common in the lateral than in the medial cartilage (P < 0.001), but no difference was observed in this respect between the front feet.

[Radiographic studies of ossification of the hoof cartilage of horses and its clinical evaluation]

Radiographic examination is a valuable means for the identification of ossified lateral cartilage. The extent and stages of development of the ossification can be determined. The active stage of development of ossified lateral cartilage, which by itself can provoke lameness, can be defined. By means of the X-ray it is tried to differentiate the three kinds of ossification: the enchondral, the peri- and parachondral ossification of the lateral cartilage. Centres of ossification and fractures of the ossified lateral cartilage are described.

von Willebrand heterotopic osteochondrofibrosis in Doberman pinschers: five cases (1980-1987)

Five cases involving female Doberman Pinschers, each with a mass composed of osseous, chondrous, or fibrous tissue, or a combination thereof, formed in or around the muscles of the hip, were reviewed. In each dog, the mass severely limited the coxofemoral joint range or motion, especially when the joint was extended. Surgical debulking resulted in a favorable outcome. All dogs tested had plasma concentrations of von Willebrand factor antigen below established normal limits. We believe that the low concentrations of von Willebrand factor antigen commonly found in Doberman Pinschers may predispose them to the development of this condition and its resulting pelvic limb lameness, presumably because of increased risk of microvascular bleeding. This association is presumptive because 2 dogs in our study had a history of excessive bleeding either before or after being treated for the hip condition. Trauma was associated in 2 cases. All 5 dogs, however, bled more than usual during the curative surgery. These 5 cases, plus additional reported cases, confirm this syndrome, which warrants recognition. The name von Willebrand heterotopic osteochondrofibrosis of Doberman Pinschers was selected because it identified the basic features of the syndrome.