2.1 Osteomyelitis and Osteosarcoma Flashcards
What is the main diagnostic problem in distinguishing osteomyelitis and osteosarcoma?
- both can present acutely
- both can present with soft tissue swelling
- both can show bone lysis and proliferation on radiograph
the question is: how does one make a diagnosis?
What is the signalment and site predilection of osteosarcoma?
(1) common in older, large breeds
- median age is ~7
- rottweilers, great danes, greyhounds, golden retrievers, etc.
(2) occurs in metaphyses
- mostly in limbs: vary rare in other locations
- areas of bone near the joints
if these criteria are not met, consider osteomyelitis
What is often found on history and physical exam in cases of osteosarcoma?
(1) history
- acute or chronic lameness
- often VERY painful
- can present with a pathological fracture
(2) physical exam
- swelling in bone metaphysis
- bone pain
- +/- crepitus
- +/- palpably soft cortex
note that recent wounds, trauma, or other infection may point more toward osteomyelitis
What are the most common sites of osteosarcoma?
TOWARD the knee, AWAY from the elbow
How do you work up an osteosarcoma suspect diagnostically?
- radiograph the painful area(s): assess for osteolysis, osteoproliferation, periosteal reaction (note that osteosarcoma is almost always monostotic - it affected only one bone)
- throracic radiographs / CT: evaluate for metastases
- if older, large breed dog is presenting for fracture, know that it could be pathological (secondary to osteosarcoma)
- biochem, CBC, urinalysis (ALP may increase with bone remodelling)
- FNA of bone lesion (70% accuracy, less challenging than biopsy, less risk of fracture)
- biopsy: jamshidi needle or michele trephine (80-90% accuracy, open or closed)
note that radiographs can only show so much: bone formation or lysis (it may not be enough to distinguish between differentials)
metastases may be in the lung, or within other bone; often, cytology is not performed, and a presumptive diagnosis is instead accepted
What are other differentials for osteosarcoma?
- osteomyelitis
- other neoplasia: chondrosarcoma, fibrosarcoma, hemangeosarcoma, multiple myeloma, lymphoma
- bone cyst
What are the treatment options and what influences decision makeing?
often unremittingly painful if left untreated, and analgesia alone will not do
- must treat the primary tumor sucessfully (pain has a significant impact on QOL NOW), and consider secondary spread (90% of patients have micrometastases within the lungs at the time of diagnosis)
options:
(1) amputation (4 months)
- complete resection removes pain
- prefents further metastases
- assess for stability for amputation (ortho disease and BSC)
(2) amputation and chemotherapy (~1 year)
(3) limbsparing surgery and chemotherapy (~1 year)
- remove dieased area and preserve limb (e.g., partial amputation)
- good QOL and MST
- contraindicated in pathological fracture: spread to local tissue
(4) radiotherapy (palliative)
(5) NSAIDs +/- biphosphonates (palliative)
(6) euthanasia
What is the most common site for osteosarcoma in cats?
the tibia
- prognosis batter than in dogs with amputation - possibly curative
What are the other primary neoplasms (differentials)?
- SCC > malignant melanoma > etc, of digit
- chondrosarcoma
- joint sarcoma
- rhabdomyosarcoma
- hemangiosarcoma (intramuscular vs subcutaneous)
- benign lipoma, infiltrative lipoma, liposarcoma
(6) Normal stifle
(7) Very mildly-suggestive neoplastic changes of the bone itself, but with very intense joint effusion. Because radiographs are not obvious, one should take. Sample of the joint fluid. If this is not successful, take a biopsy of the synovial membrane. Treatment is likely amputation.
(8) Picture of an infiltrative lipoma
What is osteomyelitis?
inflammation of the bone and/or bone marrow due to a bacterial or fungal infection
- may be post traumatic or hematogenous
- hematogenous osteomyelitis is not associated with trauma or surgery; the animals often have signs of systemic illness, such as fever and anorexia
- post traumatic osteomyelitis is an infection (inflammation) of the bone after trauma or surgery to the bone
- chronic osteomyelitis usually results from inadequate treatment of acute osteomyelitis
In dogs, the only osteomyelitis that frequently has a hematogenous route is spondylitis or discospondylitis, although epiphysitis has been described as well
What are the clinical signs of osteomyelitis?
actue:
- injury or history of surgery
- systemic signs: pyrexia, leukocytosis
- high grade lameness of acute onset
- soft tissue swelling with pain on palpation
- +/- draining sinuses: very good indicator of osteomyelitis
chronic:
- historic injury or surgery
- low to moderate grade lameness, persisting or intermittent
- pain on palpation
- potential pathological fracture
How do you diagnose osteomyelitis?
- radiographs (often not enough alone)
- FNA with culture and sesitivity
- biopsy with culture and sesitivity
on radiographs: collapsing bone with thick layers of new bone formation, suggestive of osteomyelitis
How is osteomyelitis treated?
prompt antibiotics: initially emperical (amoxicillin clavulanate), then based on cuture and sensitivity
- consider local antibiotics (beads / sponges)
- long course: typically aorund 6 weeks
remove sutures or implants that protect bacteria or maintain a biofilm (where possible)
- varied but guarded prognosis
