Retardation of endochondral ossification at the distal ulnar growth plate in dogs

Retained cartilaginous core in the distal radius of a small breed dog

A 5-month-old castrated male Smooth Fox Terrier presented for a 1-month history of right thoracic limb lameness. Physical examination revealed right elbow pain on extension and mild soft tissue swelling of the distal antebrachium. Radiographs and computed tomography showed elongated focal radiolucent regions in the distal radial metaphysis. There was incongruity of the right elbow with a short radius. Bone biopsy and histopathology of the regions confirmed a retained cartilaginous core characterised by bony trabeculae with frequently retained central cartilaginous cores. A dynamic proximal ulnar ostectomy was performed to improve elbow congruity. The owner was instructed to restrict activity to short leash walks for 8 weeks followed by a gradual activity increase. On follow-up examination 16 weeks after operatively, the lameness and elbow pain were resolved. Radiographs at that time showed a healed ulnar ostectomy, proper elbow congruity, and resolved retained cartilaginous core.

Short term outcomes and complications of distal ulnar ostectomy in 23 juvenile dogs with carpal valgus secondary to discordant radial-ulnar physeal growth

Objective

The goal of this study was to report short term clinical and radiographic outcomes after distal ulnar ostectomy in dogs with carpal valgus due to discordant radial-ulnar growth.

Study design

Retrospective case study.

Sample group

Client owned dogs under 1 year of age with carpal valgus and open distal radial physes pre-operatively.

Methods

Medical records from four veterinary referral centers were searched from January 1, 2015 to January 1, 2022 for juvenile dogs that had been treated with distal ulnar ostectomy for carpal valgus due to premature closure of the distal ulnar physis. Patients were excluded if they were skeletally mature at the time of ostectomy; medical records were incomplete; radial physis was closed at surgery; or definitive corrective osteotomy was performed. Radiographs were evaluated pre-operatively and for short term follow up at ~8 weeks. Complications and short term clinical outcomes were evaluated also.

Results

31 limbs from 23 dogs were evaluated. Patients ranged from 4 to 10.8 months of age. All dogs presented for visible carpal valgus and varying degrees of thoracic limb lameness. Sixty-four percent of patients showed resolution of lameness while an additional 13% showed an improvement in clinical lameness without complete resolution. Complications were seen in 32% of patients with 70% percent of those being minor, bandage related complications. Radiographically, 38% of limbs showed bridging callus formation of the ostectomy at an average of 7.5 weeks post operatively and 75% percent of patients with elbow incongruity improved radiographically. There was no significant difference in radial joint angles pre-operatively and at the time of follow up.

Conclusion

Distal ulnar ostectomy ameliorates lameness in juvenile dogs with premature distal ulnar physeal closure and shows lack of progression of distal carpal valgus deformity, but does not improve joint angulation.

Clinical significance

Distal ulnar ostectomy is associated with mild bandage-related complications and halting of progressive limb deformity within the time frame evaluated, and should therefore be considered a treatment for premature closure of the distal ulnar physis. It does not lead to deformity correction at 8 weeks following surgery but is associated with improved elbow congruity.

Assessment of normal radial joint orientation angles in nonchondrodystrophic small-breed dogs

OBJECTIVE

To establish reference intervals for radial joint orientation angles in the frontal and sagittal planes in small-breed dogs and to compare them to those previously reported for medium- and large-breed dogs.

ANIMALS

Antebrachii of 30 skeletally mature, nonchondrodystrophic small-breed dogs were evaluated radiographically.

PROCEDURES

Orthogonal radiographs were retrospectively assessed to determine the anatomic medial proximal radial angle, anatomic lateral distal radial angle, anatomic cranial proximal radial angle (aCrPRA), and anatomic caudal distal radial angle (aCdDRA). The frontal plane angle, θ angle, and procurvatum were also calculated. The radial joint orientation angles determined were compared to those previously reported for medium- and large-breed dogs via a 1-sample t test.

RESULTS

Mean and SD values for anatomic medial proximal radial angle, anatomic lateral distal radial angle, aCrPRA, and aCdDRA were 80.86 ± 2.86°, 85.60 ± 1.74°, 87.99 ± 2.79°, and 83.08 ± 3.14°, respectively. The mean and SDs for frontal plane angle, θ angle, and procurvatum were 4.75 ± 2.46°, 11.88 ± 1.76°, and 16.79 ± 4.13°, respectively. aCrPRA and aCdDRA were significantly different when compared to previously reported radial joint angles for medium- and large-breed dogs.

CLINICAL RELEVANCE

Reference intervals for small-breed dog radial joint orientation angles were reported. Significant differences were identified for some joint orientation angles when compared to medium- and large-breed dogs. This small-breed reference interval reported can be utilized in planning of radial angular limb deformity corrective surgery, particularly when dogs are bilaterally affected.

Juvenile Disease Processes Affecting the Forelimb in Canines

Several juvenile diseases affect the canine forelimb. The most common are hypertrophic osteodystrophy, panosteitis, and retained cartilaginous core. Panosteitis and hypertrophic osteodystrophy tend to be self-limiting, with a good long-term prognosis, although severe cases can develop. These diseases may recur during growth. Severe cases of hypertrophic osteodystrophy can lead to angular limb deformities and may even be fatal. Retained cartilaginous cores can be benign with no evidence of clinical signs and be found incidentally on radiographs. However, if they disrupt the distal ulnar physis, angular limb deformities may persist requiring surgical intervention with a corrective osteotomy.

Proximal focal humeral deficiency in a large breed dog

A 26-week-old female Boerboel was referred for evaluation of progressive left thoracic limb lameness. Computed tomography and radiographic evaluation revealed radiolucency of the caudal region of the proximal humeral metaphysis, absence of the humeral head, and gross distortion of the glenoid. Given the severe glenohumeral deformation, arthrodesis of the left shoulder was performed using orthogonal locking bone plates, lag screw fixation, and bone grafting. Despite late implant failure, arthrodesis was successful in this case, and satisfactory limb function was restored. To the author's knowledge, this is the first report of a case of a focal developmental deficiency of the proximal humerus reported in a dog.

Ulnar metaphyseal osteochondrosis in seven captive bred cheetahs (Acinonyx jubatus)

Distal ulna metaphyseal osteochondrosis was identified in seven captive bred cheetahs raised in Australia between 1984 and 2005. The disorder was characterized by bilateral carpal valgus conformation. In the metaphyseal region of the distal ulnae, an osteolucent defect that appeared as a proximal extension of the lucent physis was identified radiographically between 6 and 10 months of age. Ulna ostectomy was done to correct the angular limb deformity. Histologically, changes were identified in the osteolucent lesion that resembled osteochondrosis. We propose that the condition is probably familial and/or dietary in origin.

A new type of radiographic bone remodeling in the distal radial and ulnar metaphysis in 54 Newfoundland dogs

In this longitudinal observational study, 118 growing Newfoundland dogs were followed with sequential radiographic examination of the right front limb, which were scheduled at ages 3, 4, 6, 12, 18, and 24 months to record evidence of skeletal changes. All affected dogs had evidence of changes at 6 months and dogs included in this study had radiographic examination at 6 months and at least two other scheduled examinations that included either 4 or 12 months. The dogs were privately owned and had individualized nutrition and environment with no maintenance protocol required by the project leaders. Irregularities in bone remodeling in the distal radius and ulna were seen in radiographs of 54 of 118 (45.8%) dogs. These irregularities differ from changes previously described in the Newfoundland dog. The reported irregularities were seen as islands of reduced opacity outlined by thickened, radiopaque osseous trabeculae, which were aligned with the axis of stress. All the 54 dogs with irregularities during some phase of development consistently had changes at 6 months of age. Reorganization of the changes in the bone was slow, and residual changes were visible at 18-24 months of age in many cases. The significance of these findings may lie in their potential for misinterpretation if they had been discovered in the presence of clinical signs such as any lameness or growth arrest. Radiographic appearance indicates disturbances in the bone maturation. The etiopathogenesis is unclear. Nutritional, environmental and genetic factors have to be studied.

Forelimb lameness in the young patient

Forelimb lameness is a common problem in young dogs and can be caused by a wide variety of problems. Accurate and comprehensive diagnosis and treatment must be provided for these patients. Differential diagnoses for forelimb lameness in the young patient fall into the categories of congenital abnormalities; developmental disorders; trauma; and infectious, nutritional, metabolic, and neoplastic causes. The etiopathogeneses of many of these disorders are still unknown, and treatment options and prognoses vary tremendously. Until definitive causes are determined, it is the responsibility of veterinarians to address the factors that contribute to the development and progression of these disorders. These areas primarily involve weight and nutritional management as well as breeding programs.

The pathophysiology of osteochondrosis

Osteochondrosis is a disorder of epiphyseal cartilage about which there is considerable confusion in the literature. We believe that this is due to the fact that osteochondrosis has been studied in the chronic stage when the lesions are morphologically complicated and the initial causative insult is impossible to determine. The etiology of osteochondrosis appears to be multifactorial, with trauma, hereditary factors and rapid growth, nutritional factors, and ischemia all having a role in its pathogenesis. Although predilection sites are variable among species, the morphology of the early lesions is strikingly similar, strongly suggesting that the pathogenesis of osteochondrosis is the same, regardless of the species affected. Based on recent studies in pigs and horses, and supported by observations in dogs and cattle, we believe that local ischemia secondary to defects in cartilage canal blood supply is a key factor in the initiation of lesions of osteochondrosis and explains many of the features of this disease. Local ischemia to the epiphyseal cartilage of the articular-epiphyseal cartilage complex leads to the formation of highly vulnerable zones of necrotic epiphyseal cartilage which later cause a delay in endochondral ossification, with extension of necrotic cartilage into the subchondral bone. Trauma, whether major or minor, to the overlying articular cartilage leads to cartilage cleft formation, clinical signs of pain and lameness, and other chronic sequelae. Studies aimed at further elucidating the pathogenesis of osteochondrosis should attempt to determine the cause of the vascular defect and whether or not it may be modified by experimental manipulations.