Biomechanical evaluation of four surgical techniques for ventral stabilization of the atlantoaxial joint in dogs.

PURPOSE: This study compared, through biomechanical evaluation under ventral flexion load, four surgical techniques for ventral stabilization of the atlantoaxial joint in dogs. METHODS: In total, 28 identical atlantoaxial joint models were created by digital printing from computed tomography images of a dog, and the specimens were divided into four groups of seven. In each group, a different technique for ventral stabilization of the atlantoaxial joint was performed: transarticular lag screws, polyaxial screws, multiple screws and bone cement (polymethylmethacrylate-PMMA), and atlantoaxial plate. After the stabilization technique, biomechanical evaluation was performed under ventral flexion load, both with a predefined constant load and with a gradually increasing load until stabilization failure. RESULTS: All specimens, regardless of stabilization technique, were able to support the predefined load without failing. However, the PMMA method provided significant more rigidity (p ≤ 0.05) and also best resisted the gradual increase in load, supporting a significantly higher maximum force (p ≤ 0.05). There was no statistical difference in flexural strength between the transarticular lag screws and plate groups. The polyaxial screws method was significantly less resistant to loading (p ≤ 0.05) than the other groups. CONCLUSIONS: The PMMA technique had biomechanical advantages in ventral atlantoaxial stabilization over the other evaluated methods.

Biomechanical evaluation of four surgical techniques for ventral stabilization of the atlantoaxial joint in dogs

Purpose: This study compared, through biomechanical evaluation under ventral flexion load, four surgical techniques for ventral stabilization of the atlantoaxial joint in dogs. Methods: In total, 28 identical atlantoaxial joint models were created by digital printing from computed tomography images of a dog, and the specimens were divided into four groups of seven. In each group, a different technique for ventral stabilization of the atlantoaxial joint was performed: transarticular lag screws, polyaxial screws, multiple screws and bone cement (polymethylmethacrylate­PMMA), and atlantoaxial plate. After the stabilization technique, biomechanical evaluation was performed under ventral flexion load, both with a predefined constant load and with a gradually increasing load until stabilization failure. Results: All specimens, regardless of stabilization technique, were able to support the predefined load without failing. However, the PMMA method provided significant more rigidity (p ≤ 0.05) and also best resisted the gradual increase in load, supporting a significantly higher maximum force (p ≤ 0.05). There was no statistical difference in flexural strength between the transarticular lag screws and plate groups. The polyaxial screws method was significantly less resistant to loading (p ≤ 0.05) than the other groups. Conclusions: The PMMA technique had biomechanical advantages in ventral atlantoaxial stabilization over the other evaluated methods.

Uncommon Atlantoocciptal Localization of Tumoral Calcinosis in a Dog.

A 5-month-old male Rottweiler dog presented with an acute upper motor neuron tetraparesis. A computed tomography study of the cervical spine revealed amorphous mineralization of the soft tissues dorsal to the articular surface of the occipital bone and atlas. The calcification extended into the vertebral canal, causing significant dorsal compression of the spinal cord. Suboccipital craniectomy and partial dorsal atlas laminectomy were performed to remove the extradural calcification. Histopathology was compatible with tumoral calcinosis. Significant clinical improvement was noted in the immediate postoperative period, and there was complete recovery with no recurrence at the last clinical follow-up 15 months postoperatively. Suboccipital craniectomy and partial dorsal atlas laminectomy allowed successful surgical resection of a dorsal craniooccipital tumoral calcinosis in this dog. The decompression resulted in resolution of clinical signs and recurrence is unlikely since there is no underlying disease.

Cervical ventral slot in rabbits (Oryctolagus cuniculus). Piezosurgery versus conventional technique.

PURPOSE: To investigate the applicability of piezosurgery for cervical ventral slot (CVS), comparing it with the conventional technique of using high-speed burs for bone wear. METHODS: Thirty rabbits (Oryctolagus cuniculus) were divided into two treatment groups (T1 and T2) corresponding to CVS between C3-C4. In T1, the surgery was performed with piezoelectric apparatus, and in T2 with high-speed burs. The evaluated parameters were: duration of each stage of surgery, temperature variations during CVS, visibility of the surgical field, intra and postoperative complications, and anesthetic monitoring. At 14, 28, and 56 postoperative days, five animals from each treatment group were submitted for histopathological study of the surgical site. RESULTS: Compared with T2, T1 had more precise bone cut, and better visibility of the operative field, although it required longer total surgical time (p = 0.02) and triggered a greater number of intraoperative complications (p < 0.01), microscopic lesions in the spinal cord (p < 0.05), and transient neurological deficits in the postoperatively (p < 0.05). CONCLUSIONS: It is necessary to perform surgical planning and have several tips of the piezoelectric instrument available for the safe use of the piezoelectric device in neurosurgery.