Antebrachium
Angular limb deformity
Panosteitis
Hypertrophic osteodystrophy
Retained cartilage core
Radioulnar Ischemic Necrosis
Osteosarcoma
Trauma/Fractures
Angular limb deformity
Signalment
Breeds – Any breed is susceptible, but may be more common in large dogs
Gender – No gender predilection
Age – Condition occurs in dogs with open growth plates
Etiology - Trauma is the cause of angular limb deformities in nonchondrodystrophic dogs. Chondrodystrophic dogs commonly have growth plate conditions that result in angular limb deformities, but the deformity may be worse with trauma superimposed. Angular limb deformities generally occur in the antebrachium or crus as a result of damage to the growth plate of one of the bones of a 2-bone system in those regions of the limb. Premature closure or partial closure of a growth plate in one bone with continued growth in the other results in angulation and rotation of the limb.
History
Trauma is generally in the history, and can range from automobile trauma to jumping from a height. Initially, lameness is present. If there is a complete fracture, owners may notice swelling and disruption of the bony column. Primary treatment of the fracture may be successful only to have angular limb deformity develop as a result of growth plate damage. In cases of minor trauma without complete fracture dogs may initially have lameness, then become more sound, with progressive angulation and/or rotation of the limb. The affected limb may be shorter than the contralateral normal limb. As the condition progresses, lameness may occur as a result of malarticulation of the joint about or below the injury.
​
Clinical Findings
Dogs with complete fractures will have obvious disruption of the bone column will have non weight-bearing lameness. Over time, even though the primary fracture has undergone healing, rotation and angulation of the limb may become more apparent. The classic angular limb deformity involves premature closure of the distal ulnar physic with continued growth of the radius. This causes cranial and lateral bowing of the radius, shortening of the ulna (and many times the entire antebrachium, valgus deformity, external rotation of the foot, and in severe cases, subluxation of the carpus and/or elbow joints. Pain may be present in the carpus and elbow joints when subluxation occurs. Although this is the most common angular limb deformity, injury to growth plates can have different appearances and consequences depending on the severity of injury to the various growth plates.
Diagnostics
Radiographs generally show complete or partial closure of one or both growth plates, in addition to the angulation and rotation of the limb. A CT more accurately depicts the condition, especially with 3-D reconstruction. A model may be printed of the bones to help with surgical planning and practice.
Treatment Options
Treatment of angular limb deformities can be complex, and consultation with a veterinarian experienced in the management of these cases is highly recommended. When considering the approach to managing these cases, the following are helpful: 1) Age of the animal and remaining growth potential, 2) Which bone(s) is(are) affected, 3) Complete or partial physeal closure, 4) Is joint subluxation present, 5) How much shortening is present, and how much can be tolerated, 6) How severe are the rotational and angular deformities?
​
Options for treatment include ostectomy of the shortened bone, osteotomy(ies) of bone(s) with rotation and straightening of limb. A variety of osteotomy techniques may be used. Some cases may require osteotomies in the distal and proximal portions of the bone. Fixation devices commonly used include bone plates and screws, linear external fixators, ring external fixation, or hybrid fixation devices.
​
Panosteitis
Signalment
Breeds – Large and giant breeds, especially German shepherd dogs and Bassett hounds
Gender – Males are more commonly affected, but females are also affected
Age – 5 months up to 2 years (although it is uncommon after 1 year of age)
Etiology – Unknown, but nutrition and genetics may play a role. A viral cause has also been postulated.
History
Mild to moderate lameness, often moves between different limbs, may be lethargic with decreased appetite
Clinical Findings
Mild to moderate lameness, pain on palpation of diaphysis of long bones
Diagnostics
Radiographs are helpful, but not always diagnostic depending on stage. There may be attenuation of trabecular patterns in the proximal and distal aspects of the diaphysis. This may be followed by the development of patchy densities, especially around the nutrient foramen of bones. The periosteum may demonstrate reactive changes, followed by thickening of the cortices. CT may also be helpful.
Treatment Options
Rest, nonsteroidal anti-inflammatory drugs, change to large dog growth diet or adult dog food
Hypertrophic osteodystrophy (Metaphyseal osteopathy)
Signalment
Breeds – Medium and large breeds of dogs, especially Great Danes, Irish Setters, boxers, Labrador retrievers, Weimaraners
Gender – Males may be predisposed
Age – 2 to 6 months of age
Etiology - The cause is unknown, but recent studies in Weimaraners suggest it may be an immune-mediated condition. Other potential causes include bacterial, viral, or post-vaccination. Vitamin C deficiency has long been mentioned, but there is no proof of this, and treatment does not seem to affect the course of the disease.
History
Affected dogs may often have a history of lethargy, anorexia, pain, reluctance to move, and lameness.
​
Clinical Findings
Lethargy, pyrexia, lameness, a roached back appearance while standing, swelling and pain on palpation of metaphyseal regions of long bones, anorexia.
Diagnostics
Radiographs are often diagnostic. Changes include a linear radiolucency near the normal growth plate (double physeal line). Later in the course of the disease, there is periosteal reaction in the metaphyseal region. In severe cases, the physis may close prematurely as a result of the periosteal reaction, resulting in an angular limb deformity. CT examination may also be performed, but is usually not necessary unless radiographic signs are subtle.
Treatment Options
Supportive care is important, based on clinical status. Fluid therapy may be indicated if dehydration is present. Feeding a large breed growth diet should be instituted. Analgesics may be needed. If nonsteroidal anti-inflammatory medications are initiated, do not treat with steroids. Recent studies of Weimaraners with a presumed immune-mediate component have responded to corticosteroid treatment, but concurrent use of NSAIDs will likely result in gastrointestinal signs, and even gastric perforation. Range of motion of affected joints and cryotherapy applied to the area may be beneficial.
Retained cartilage core (Retained hypertrophied endochondral cartilage)
Signalment
Breeds – Usually in large breeds of dogs
Gender – No apparent gender predilection
Age – 4-8 month old dogs
Etiology - Unknown, but a dietary influence has been suggested. Affects the distal ulna with retained hypertrophied cartilage.
​
History
Dogs may have progressive valgus deformity and lameness.
​
Clinical Findings
In addition to lameness and valgus deformity, dogs may have instability of the lateral carpus as a result of shortening of the distal ulna because of retained cartilage. There may be cranial bowing of the distal radius.
Diagnostics
Radiographs are diagnostic and show a "candlewick" appearance to the distal ulna, proximal to the typical conical physis. The ulnar styloid process may also be shortened. The condition may occur in one or both ulnas.
Treatment Options
If the condition is severe enough to cause lameness or virus deformity, an ostectomy of the region of retained cartilage is usually curative.
​
​
Radioulnar Ischemic Necrosis
Signalment
This condition is rare, and there is not a clear signalment. It has been reported in an 11 month old Golden retriever, a 3 year old male Pomeranian, and a 7 year-old Jack Russell Terrier
​
Etiology - Radioulnar ischemic necrosis (RUIN) is a term to describe osteonecrosis secondary to ischemia of the radius and ulna. Underlying causes may include osteomyelitis, neoplasia, chronic desmopathy of the interosseous ligament, previous low grade trauma. Hemangioma and hemangiosarcoma are potential neoplastic causes.
​
History
Dogs may present with a progressive lameness of the affected forelimb. The lameness may be severe in some cases.
Clinical Findings
Dogs may have lameness, muscle atrophy, and pain on palpation of the affected area. Because young dogs may be affected, consideration must also be given to panosteitis.
Diagnostics
Radiographically, RUIN lesions appear as osteolytic lesions on the opposing radial and ulnar cortices, usually in the proximal 1/3 of the radius and ulna in the region of the caudal interosseous artery. Periosteal reaction may also be noted on the adjacent cortices. CT images have similar findings.
Fine needle aspirates, bone biopsy, and culture and sensitivity testing may ellucidate the underlying cause, although a definitive cause may not be identified.
Treatment Options
If an underlying cause can be identified, treatment of the etiology may resolve the lameness. Nonneoplasic and noninfectious causes may be treated by currettage of the lesion and packing with a bone graft. Extensive lesions may result in a fracture and should be treated accordingly. An amputation may be necessary for neoplastic causes, depending on the type of tumor and prognosis.
RUIN lesion in radius
RUIN lesion in radius on cross-sectional CT image.
Osteosarcoma
Signalment
Breeds – Large and giant breeds
Gender – No apparent predilection
Age – Median age is 7 years, but cases may also occur between 18-24 months of age
Etiology – Unknown, but may have a genetic basis
History
Progressive lameness that may progress to severe lameness with development of a pathologic fracture, owners may notice swelling of the affected area, weight loss, and poor appetite in later stages of the condition.
​
Clinical Findings
Mild to moderate lameness, swelling of distal radius, pain on palpation, possible crepitus and instability if a pathologic fracture is present.
Diagnostics
Radiographs of antebrachium and chest radiographs or CT for evaluation of metastatic disease. Fine needle aspirate or biopsy is recommended to confirm clinical suspicions.
Treatment Options
Amputation with chemotherapy gives the best prognosis with a median survival time of approximately 1 year. Amputation alone gives palliative pain relief, but does not prolong survival. Other limbs and joints should be assessed to be certain that the dog can cope with an amputation. Limb sparing treatment may be an option in some early cases. Euthanasia is also an option.
Trauma/fractures
Signalment
Breeds – Any breed
Gender – No gender predilection
Age – Any age
​
Etiology – Trauma. Many cases occur as a result of automobile trauma. Because of this and the fact that the forelimb is affected, careful evaluation of the thoracic structures is important to detect cardiac arrhythmias, pneumothorax, pulmonary edema, or diaphragmatic hernia.
History
Often owners witness trauma, such as a fall, hit by automobile, or other sudden traumatic event that results in sudden onset of severe lameness.
Clinical Findings
Fractures of the antebrachium result in pain on manipulation and crepitation during manipulation of the limb.
Diagnostics
Radiographs are generally diagnostic, but CT evaluation may give additional details.
Treatment Options
Most fractures of the antebrachium require internal or external fixation to restore anatomy and function. Internal fixation devices include bone plate and screws. External fixation includes standard linear external fixators, circular external fixators, and hybrid external fixators. Simple fractures in young dogs may be treated with a cast in some situations. An intramedullary pin is not a treatment option for the radius because there is no nonarticular access point to place the pin. An intramedullary pin may be placed in the ulna, however.