Humerus
Panosteitis
Osteosarcoma
Metastatic bone tumor
Trauma/fractures
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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
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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.
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Clinical Findings
Mild to moderate lameness, swelling of proximal humerus, pain on palpation, possible crepitus and instability if a pathologic fracture is present.
Diagnostics
Radiographs of humerus 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. Euthanasia is also an option.
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Metastatic bone tumor
Signalment
Breeds – Any breed is possible
Gender – No apparent breed predilection
Age – Generally middle-aged to older dogs
Etiology – Metastatic lesions may occur to the bone from a variety of neoplasms, but especially mammary cancer, multiple myeloma, prostate cancer.
History
Dogs generally have clinical signs consistent with the primary tumor. Metastatic lesions to the bone cause variable degrees of lameness. Veterinarians should be cautious when other concurrent orthopedic conditions exist.
Clinical Findings
Variable degrees of lameness, pain on palpation of the midshaft of long bones.
Diagnostics
Radiographs or CT evaluation of bones. Metastatic bone tumors generally occur in the midshaft of long bones, whereas osteosarcoma generally occurs in the metaphyseal region of bones. Diagnostic assessment of the primary neoplasm should be undertaken. Biopsy is recommended to confirm clinical suspicions.
Treatment Options
Treatment of the primary neoplasm is recommended. Chemotherapy is likely to improve lameness due to metastatic bone tumors. Local radiation therapy may give local control of bone tumors.
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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 humerus 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 humerus require internal fixation to restore anatomy and function.