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Idiopathic osteomyelitis/osteonecrosis of the jaw in dogs

When they enter your exam room, you will smell what’s going on before you are able to see it

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Figure 1: Photograph of the left mandible of a cocker spaniel presenting with bilateral osteomyelitis/osteonecrosis.

Osteomyelitis of the maxilla, mandible, or incisive bone, can occur due to severely diseased teeth in an area, but some cases don’t seem to be simply the result of an extension of periodontal or endodontic disease. These cases are often more than just osteomyelitis. Instead, they show evidence of dead bone, often in the form of a sequestrum, a necrotic piece of bone that may want to come out in one large piece during surgical exploration. In the absence of any history of radiation therapy or bisphosphonate administration, these cases are best described as idiopathic osteomyelitis/osteonecrosis. When they enter your exam room, you will smell what’s going on before you are able to see it.

For your consideration

Case 1: A four-and-a-half-year-old castrated male cocker spaniel presented for severe halitosis and lethargy. The patient had a history of ear, skin, and anal gland disease suggestive of allergic origin. Halitosis had begun approximately three months earlier, at which time the patient was taken to its local veterinarian, who extracted one tooth and performed a dental cleaning. Halitosis continued and lethargy ensued for approximately two months until the patient presented to our hospital.

Figure 2: Radiograph of the right mandible of the same patient shown in Figure 1. Note the sequestrum as evidenced by the radiolucent line separating a large portion of bone from the mandible.

The physical exam was limited due to the patient’s aggressive nature, but a yellow-green oral discharge was seen adhered to the fur of the chin. Evidence of ear, skin, and lip fold disease was present. Palpation of the mandibles was accomplished after muzzling the patient, revealing firm bilateral swelling of the mandibles. Moderate mandibular lymphadenomegaly was noted bilaterally. Preoperative blood work was nonremarkable except for slight elevations in globulin, aspartate aminotransferase, platelets, and monocytes. The patient was anesthetized for a thorough oral examination, which revealed mobile and missing molars and severe gingival recession with tan-yellow exposed bone in the area of mandibular first and second molars bilaterally (Figure 1).

Dental radiographs revealed multiple punctuate radiolucencies within affected bone, a marked periosteal reaction, and evidence of sequestrum formation (Figure 2). Diseased teeth and healthy teeth immediately adjacent to the infected bone were extracted. Necrotic bone was removed, leaving only the ventral mandible intact. The neurovascular bundle of the mandibular canal was no longer recognizable due to severe necrosis. The area was curetted and lavaged with 0.12 percent chlorhexidine solution. A mucoperiosteal flap was created using the alveolar and buccal mucosa, and sutured using monofilament absorbable suture in a simple interrupted pattern. A fentanyl transdermal patch was placed postoperatively and the patient was supplemented with injectable opioids.

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Bilateral maxillary osteonecrosis in a standard poodle showing characteristic soft tan/brown bone.

Intraoperative intravenous ampicillin was given after bacterial cultures were obtained from the diseased mandibles and the lip fold area. Culture of the mandibles grew Proteus mirabilis, E. coli, and E. faecalis. Cultures of the lip fold area grew Proteus mirabilis, E. coli, and Pseudomonas aeruginosa. Though anaerobic cultures were performed, no growth was observed. Histopathology of the mandible revealed diffuse bone necrosis with chronic suppurative osteomyelitis and colonies of filamentous bacteria. Clindamycin (10 mg/kg PO bid x 7 weeks) and concurrent metronidazole (30 mg/kg PO q24h x 1 week, then 15 mg/kg PO q24h for 6 weeks) were prescribed. Reexaminations were performed at two weeks and one month postoperatively. Anesthetized reexamination was done nine months postoperatively. Oral exam and dental radiographs revealed resolution of infection in previously affected areas and no signs of osteonecrosis in previously unaffected areas.

Case 2: A seven-year-old male standard poodle presented for severe halitosis and bilateral facial swelling in the area of the maxillary fourth premolars. Halitosis had begun approximately four months earlier, at which time the patient was taken to its local veterinarian, who extracted both maxillary fourth premolars and noted the surrounding bone to be necrotic. Cytology of the surrounding bone revealed suppurative, septic inflammation. The patient was placed on clindamycin, but halitosis continued. Metronidazole was then prescribed and a response was seen, but odor and swelling returned within 10 days of discontinuation of treatment.

Four months after initial presentation, the dog was referred. Tremoring of the lower jaw, presumably a manifestation of the jaw opening reflex, was seen for two months prior to presentation. Appetite was normal, but the client felt the dog was sleeping more than usual. Physical examination was nonremarkable with the exception of orofacial abnormalities. Severe halitosis was present. Both maxillary fourth premolars were missing and the bone in these areas was exposed and tan/yellow (Figure 3). Firm swellings were present ventral to the orbits bilaterally. Moderate mandibular lymphadenomegaly was noted bilaterally. Preoperative blood work revealed moderately elevated globulin and mild monocytosis. The patient was placed under general anesthesia for oral examination and dental radiographs.

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Maxillary first molar tooth and bone sequestrum retrieved from the same patient in Figure 3.

Dental radiographs revealed a marked periosteal reaction, and evidence of sequestrum formation. Diseased teeth were extracted, as were healthy teeth immediately adjacent to the infected bone. Necrotic bone was removed, including a large sequestrum from both sides (Figure 4). Aerobic culture grew Proteus mirabilis, E. coli, and E. faecalis. Anaerobic culture grew Clostridium and unidentified fusiform bacteria. Histopathology revealed bone necrosis with colonies of filamentous bacteria and suppuration. The infraorbital neurovascular bundle was no longer recognizable due to severe necrosis, with a deep bed of granulation separating the sequestrum from the nasal passage/sinus. The area was lavaged copiously with 0.12 percent chlorhexidine solution. A mucoperiosteal flap was created using the alveolar and buccal mucosa and sutured using monofilament absorbable suture in a simple interrupted pattern. A fentanyl transdermal patch was placed postoperatively and the patient was supplemented with injectable opioids until leaving the hospital 16 hours later.

Intraoperative intravenous cefazolin was given after bacterial cultures were obtained. Clindamycin (8.6 mg/kg PO bid x 6 weeks) and concurrent metronidazole (29 mg/kg PO q24h x 1 week, then 9.6 mg/kg PO q24h for two weeks) were prescribed. A reexamination was performed 18 days postoperatively. Sites appeared to be healing well and suborbital swelling was resolved. The clients were contacted by telephone 21 months after initial presentation and no signs of recurrence (odor, decreased appetite, oral discharge) were seen.

The key point about these cases is that antibiotics alone will not fix the problem. Aggressive surgical debridement, sequestra removal, and extraction of teeth in the area are necessary, followed by long-term antibiotics. Good outcomes can be achieved with aggressive treatment.

Recommended reading
1) Peralta S, Arzi B, Nemec A, Lommer MJ, Verstraete FJ. Non-Radiation-Related Osteonecrosis of the Jaws in Dogs: 14 Cases (1996-2014). Front Vet Sci. 2015 May 5;2:7. doi: 10.3389/fvets.2015.00007.

2) Stepaniuk K. Bisphosphonate related osteonecrosis of the jaws: a review.
J Vet Dent. 2011; 28(4): 277-81.

Have you ever seen a case of jaw osteonecrosis in a dog or cat? If so, let me know the details of your case at info@siloacademy.com. I hope you and yours have a wonderful holiday season.

John Lewis, VMD, FAVD, DAVDC, practices dentistry and oral surgery at NorthStar VETS in Robbinsville, N.J., and is the founder of Silo Academy Education Center in Chadds Ford, Pa.

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