ABSTRACT 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.

RESUMO: A laminectomia dorsal é realizada com frequência no tratamento de compressões medulares ou estenose do canal vertebral cervical. No entanto, complicações relevantes têm sido descritas em cães. Considerando que ainda não há entendimento completo da necessidade de estabilização cirúrgica complementar após a realização de uma ou múltiplas laminectomias na região cervical, o objetivo deste estudo foi comparar a resistência e amplitude de movimento (ADM) da coluna cervical submetida à laminectomia Funkquist B entre a sexta e a sétima vértebras em cães. Quarenta e quatro colunas vertebrais cervicais (C2-T1) de cães, com peso médio de 26,2 ± 3,8 kg, foram selecionadas por meio de radiografia e tomografia computadorizada. Quatro grupos experimentais (n = 11) foram estabelecidos de acordo com o teste mecânico realizado: dois grupos controle (flexão e extensão controle) e dois grupos laminectomia (flexão e extensão laminectomia). Os resultados numéricos da carga máxima para medir a resistência e ADM das colunas dos dois grupos de controle e dos dois grupos de laminectomia foram comparados. Os grupos de laminectomia apresentaram menores valores de carga máxima, independentemente do teste mecânico realizado (P < 0,001). A ADM não foi influenciada pela laminectomia, tipo de teste mecânico (flexão ou extensão ventral) ou sua interação (P < 0,05). Não houve interação entre o efeito do fator de laminectomia, sim ou não, ou o efeito do teste mecânico na flexão ou extensão ventral (P < 0,05). A laminectomia cervical dorsal Funkquist B entre C6 e C7 diminui a resistência mecânica com uma força de carga suprafisiológica, mas não altera a ADM, sugerindo que pode ser usada sem estabilização mecânica adicional em cães.

ABSTRACT: Dorsal laminectomy is routinely performed for spinal cord compressions or stenosis of the cervical vertebral canal. However, despite good results, relevant complications have been described in dogs. Considering the incomplete understanding of the necessity for complementary surgical stabilization after performing laminectomies in the cervical region, this study compared the resistance and range of motion (ROM) of the cervical spinal column subjected to Funkquist B laminectomy between the sixth and seventh vertebrae in dogs. Forty-four cervical vertebral columns (C2-T1) of dogs, with an average weight of 26.2±3.8 kg, were selected using radiography and computed tomography. Four experimental groups (n=11) were established according to the mechanical test: two control groups (flexion and extension control) and two laminectomy groups (flexion and extension laminectomies). Numerical results of the maximum load for measuring the resistance and ROM of the columns of the two control groups and the two laminectomy groups were compared. The laminectomy groups showed a lower maximum load, regardless of the mechanical test performed (P<0.001). The ROM was not influenced by laminectomy, the type of mechanical test (ventral flexion or extension), or its interaction (P<0.05). There was no interaction between the effect of the laminectomy factors (yes or no) and the effect of the mechanical tests for ventral flexion or extension (P<0.05). In conclusion, Funkquist B dorsal cervical laminectomy between C6 and C7 decreases mechanical resistance with a supraphysiological loading force but does not alter the ROM, suggesting that it can be used without additional mechanical stabilization in dogs.

RESUMO: Este trabalho descreve a fratura patológica da cabeça do femur (displasia fiseal) em quatro machos (três raças mistas e um Bengal), com idade média de 16 meses, que foram tratados com ostectomia da cabeça e colo femorais. Três gatos eram castrados e um inteiro. Todos apresentaram leve claudicação intermitente nos membros pélvicos. O deslocamento da epífise femoral e a reabsorção do colo femoral estavam presentes, a excisão da cabeça e colo femoral foi realizada em todos os casos. O exame histológico mostrou focos de compacteção e fibrose trabecular com deposição de tecido conjuntivo fibroso, permeado por tecidos de granulação, consistentes com o suposto diagnóstico. A função dos membros melhorou em todos os paciente entre dois a quatro semanas pós-operatório. O diagnóstico da displasia fiseal pe desafiador e o tratamento é diferente das fraturas traumáticas agudas. A excisão de cabeça e colo femoral é considerada uma boa alternativa nesses pacientes.

ABSTRACT: This report described pathological fracture of the femoral head (physeal dysplasia) in four male cats (three mixed breed and one Bengal), with an average age of 16 months, treated by an ostectomy of the femoral head and neck. Three cats were neutered and one entire. All presented with mild intermittent lameness in the pelvic limbs. Displacement of the femoral epiphysis and resorption of the femoral neck were present and excision of the femoral head and remaining neck was performed in all cases. Hstological examination showed mild foci of compaction and trabecular fibrosis with deposition of fibrous connective tissue, permeated by granulation tissues, consistent with the original diagosis. Limb function improved in all patients from 2 to 4 weeks postoperatively. Diagnosis of physeal dysplasia is challenging and treatment is different from acute traumatic fractures. Femoral head and neck excision was considered a good alternative in these patients.