A modified ventral fixation for surgical management of atlantoaxial subluxation in 19 dogs

OBJECTIVE: To describe a modified ventral stabilization technique for surgical management of atlantoaxial subluxation in dogs and to evaluate the outcome. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Nineteen client-owned dogs. METHODS: Medical records of 19 dogs with a radiographic diagnosis of atlantoaxial subluxation surgically managed by a modified ventral fixation technique (cortical screws, Kirschner wires, polymethylmethacrylate) were reviewed. Data on pre- and post-operative neurologic status, surgical technique, and complications were retrieved. Follow-up evaluation was performed at approximately 1 month. Telephone interview of the owner was used for long-term assessment (median follow-up for 17 surviving dogs was 10.5 months). RESULTS: Adequate reduction and stabilization was achieved in all dogs based on radiographic assessment immediately after surgery. Improved neurologic outcome occurred in 16 dogs at 1 month and in 15 dogs at follow-up; 2 dogs died of post-operative complications within 24 hours of surgery. One dog was euthanatized at the owners' request because of recurrent neck pain associated with implant failure after 1 month. Two dogs required surgery to remove broken and migrated implants, but further stabilization was not necessary. CONCLUSIONS: Adequate stabilization and improved neurologic outcome was achieved in most dogs. However, on account of the small size of the study and the variable neurologic signs of the dogs on admission, the surgical technique described could not be compared to those previously reported. CLINICAL RELEVANCE: The surgical technique described is an effective means of surgical treatment for atlantoaxial subluxation.     

Occipitoatlantoaxial malformation with atlantoaxial subluxation in a cat

Occipitoatlantoaxial malformation and atlantoaxial subluxation was diagnosed in a three-year-old castrated male domestic shorthair cat. Clinical signs included ataxia, postural reaction deficits, abnormal spinal reflexes, and behaviour changes. Radiographic examination revealed malformation and hypoplasia of the occipital condyles, hypoplasia of the dens, and atlantoaxial subluxation. Electroencephalographic (EEG) findings included high voltage slow activity and sharp waves with superimposed low voltage fast activity in the occipital leads and sinusoidal beta waves in the frontal leads. Basilar artery compression as a result of atlantoaxial instability is suspected to have caused the behavioural changes and EEG abnormalities in this patient. The cat was treated by stabilisation of the atlantoaxial subluxation by ventral cross pin fixation, odontectomy, and arthrodesis of the atlantoaxial articulation. The patient responded well to treatment and was neurologically normal 18 months after surgery.     

Dorsal cross pinning of the atlantoaxial joint: New surgical technique for atlantoaxial subluxation

The subluxated atlantoaxial joint of a tetraplegic Yorkshire terrier was reduced and secured in position by means of cross pinning applied via a dorsal approach. The dog made a very satisfactory recovery. The surgical technique for this new procedure is described. Further investigations into the biomechanics of such fixation, and long term follow-up of treated cases, will be required to evaluate accurately the value of this technique.     

Laminectomy for relief of atlantoaxial subluxation in four horses

Malalignment of the atlas and axis was seen in 4 horses with an idiopathic form of atlantoaxial subluxation characterized by spinal cord compression on extension. The bone structure and density of the atlas and axis were radiographically normal in 3 of the 4 horses. Clinical signs appeared when the horses were 6 to 30 months old, and 3 of the 4 horses had a history of trauma. Although a congenital anomaly could not be ruled out, the cause was thought to be trauma. The horses were moderately to severely ataxic at the time of examination. Myelography revealed compression of the spinal cord at the atlantoaxial junction on extension. Flexion completely relieved the compression. In each horse, subtotal laminectomy of the caudal two thirds of the dorsal arch of the atlas was used to relieve the spinal cord compression. Two horses recovered fully, one had residual grade-1 neurologic deficits, and a fourth was euthanatized after it fractured a limb 6 weeks after surgery.     

Bone plating to stabilize atlantoaxial subluxation in four dogs

Four dogs with atlantoaxial subluxation were treated surgically via a ventral approach and the application of an ASIF mini H plate and 2·0 mm screws to the vertebral bodies. Three dogs recovered and are well but one dog died of a cardiac arrest postoperatively.     

Stabilisation of atlantoaxial subluxation in the dog through ventral arthrodesis

Ten miniature breed dogs with atlantoaxial subluxation underwent ventral lag screw stabilisation. The procedure did not include bone graft packing into the atlantoaxial articulation. Four dogs showed continuous improvement after surgery. Three dogs developed complications due to external trauma and postoperative implant failure but improved with conservative therapy. Three patients died or were euthanized in early perioperative or postoperative period. The long-term outcome was good or favourable in all surviving patients. Suspected fibrous tissue proliferation and stabilisation without permanent bone fusion was found to be clinically satisfactory when the atlantoaxial joint has been subjected to limited stress during a long-term monitoring period.     

Surgical decompression for traumatic atlantoaxial subluxation in a weanling filly.

A filly with ataxia and splinting and crepitation in the neck was found to have atlantoaxial subluxation. Radiographic diagnosis was based on the same criteria as those used in other species, ie, increased distance between the atlas and spine of the axis and increased distance between the dens and floor of the atlas. Extensive hemilaminectomy was performed to decompress the spinal cord. Stabilization was not attempted. Immediate postoperative response was encouraging, but the untimely death of the filly prevented further evaluation of the procedure.     

Partial ostectomy of the dens to correct atlantoaxial subluxation in a pony

Objective: To report a surgical technique that allows decompression and anatomic re‐alignment for management of subluxation of the atlantoaxial articulation. Study Design: Clinical report. Animals: Four‐year‐old Welsh Section B pony gelding. Methods: Attempts at closed reduction of subluxation of the atlantoaxial articulation under general anesthesia were unsuccessful, so a ventral surgical approach allowing partial ostectomy of the dens of the axis was used to facilitate reduction. Result: Recovery from surgery was uneventful and the pony remained comfortable without neurologic deficits. Both neck stiffness and ataxia resolved. Radiographic examination at 5 days and 6 months postoperatively showed normal anatomic position of the dens of the axis and stabilization of the atlantoaxial joint. Conclusion: Partial ostectomy of the dens using a ventral approach can be used to facilitate reduction of atlantoaxial subluxation.     

Stabilization of atlantoaxial subluxation secondary to atlantooccipital malformation in a Devon calf

Atlantoaxial subluxation secondary to atlantooccipital malformation in a 14-day-old female Devon calf was corrected by alignment and stabilization of the atlantoaxial joint. Stabilization was achieved by the ventral placement of pins and screws, and the dorsal placement of a figure 8 tension band wire. At 2 and 14 days post operatively, adequate alignment of the atlantoaxial joint was confirmed radiographically. Following surgery the calf improved clinically, but was terminated 14 days following the surgery due to a pneumonia. At necropsy the fixation was stable and spinal cord decompression had been achieved. It was concluded that this technique could be utilized to allow decompression, anatomical alignment, and stabilization of an atlantoaxial subluxation secondary to atlantooccipital malformation in a calf. At necropsy, there was gross and histologic evidence of congenital fusion of the basioccipital bone to the malformed atlas.     

Ventral approach for stabilization of atlantoaxial subluxation secondary to odontoid fracture in a foal

Atlantoaxial subluxation secondary to odontoid fracture in a 30-day-old foal was corrected by alignment of the atlantoaxial joint and stabilization with 2 ventrally placed dynamic compression plates. At 90 days after surgery, healing of the fracture, with adequate alignment of the atlantoaxial joint, was confirmed radiographically. The foal was only slightly tetraparetic at that time. At 1 year after surgery, the gait was normal. It was concluded that the technique has advantages over the use of Steinmann's pins or external coaptation for stabilization. The ventral approach allows decompression, anatomic alignment, and immediate stabilization of the subluxation. Potential complications of the ventral approach include laryngeal paralysis.     

Conservative management of pyothorax in an Amur tiger (Panthera tigris altaica)

Therapy for pyothorax, or pleural empyema, has not been described for large felids. This case describes the successful treatment of pyothorax in a captive, large felid. A 15-yr-old multiparous, female Amur tiger (Panthera tigris altaica) presented with nonspecific clinical signs caused by an insidious onset of pyothorax. Management of pyothorax cases in companion animals often involves thoracostomy tube placement with recurrent drainage of the pleural cavity, intensive supportive care, and monitoring. In this case, conservative management was elected because hospitalization was not a viable option. Thoracocentesis was performed to drain as much fluid from the chest cavity as possible, yielding more than 1.3 L. Corynebacterium sp. and unidentified anaerobic gram-positive cocci were cultured. Treatment included cefovecin subcutaneously, oral antibiotic therapy with clindamycin and marbofloxacin, meloxicam, and restricted exercise by minimizing access to the main exhibit. Significant improvement was noted clinically and radiographically 6 wk later, and no relapses were noted in the following weeks. An examination 11.5 mo later confirmed resolution.     

Risk factors affecting the outcome of surgery for atlantoaxial subluxation in dogs: 46 cases (1978-1998)

OBJECTIVE: To identify risk factors for successful surgical management of dogs with atlantoaxial subluxation (AAS). DESIGN: Retrospective study. ANIMALS: 46 dogs managed surgically for AAS. PROCEDURE: Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, radiographic appearance of the dens, type (dorsal or ventral procedure) and number (1 or 2) of surgeries performed, grade of postoperative atlantoaxial joint reduction, and neurologic status prior to surgery (preoperative), when dogs were discharged from the hospital (postoperative), and during a follow-up evaluation (final) were obtained from the dogs' medical records. Risk factors for surgical success and degree of neurologic improvement were identified and analyzed for predictive potential. RESULTS: Age at onset of clinical abnormalities < or = 24 months was significantly associated with greater odds of a successful first surgery and final outcome and a lower postoperative neurologic grade. Duration of clinical abnormalities < or = 10 months was significantly associated with greater odds of a successful final outcome and a lower final neurologic grade. A preoperative neurologic grade of 1 or 2 was significantly associated with a lower final neurologic grade. Potential risk factors that did not affect odds of a successful outcome included type of surgery performed, grade of atlantoaxial joint reduction, radiographic appearance of the dens, or need for a second surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Age at onset of clinical abnormalities, duration of clinical abnormalities prior to surgery, and preoperative neurologic status are risk factors for success of surgical management of AAS in dogs.     

Conservative management of uroperitoneum in a gelding.

Uroperitoneum as a sequela to urethral calculus in an adult gelding was successfully managed by use of subischial urethrotomy and abdominal drainage. Necrosis of bladder mucosa was seen endoscopically, but a tear or rupture was never identified. Peritonitis developed but was controlled with antibacterial treatment. Although uroperitoneum is usually a sequela to bladder rupture and the ideal treatment is surgical repair, conservative management may be warranted in selected cases.     

Conservative management of cystorrhexis in four adult horses

Rupture of the urinary bladder is rare in adult horses with various standing or recumbent surgical repair techniques historically reported as the treatments of choice. This case series describes the successful conservative management of cystorrhexis in 4 adult horses. Conservative management is therefore a potentially viable treatment option which forgoes the risks of general anaesthesia and may reduce the post operative complications associated with surgery of the bladder.