RESUMEN
OBJECTIVE: To compare screw fixation strength for subtalar arthrodesis. METHODS: Eight matched pairs of cadaver feet underwent subtalar joint arthrodesis with two 7.3mm cannulated screws. Randomization was used to assign screw orientation, such that one foot in each pair was assigned dorsal to plantar screw orientation (DP Group), and the other foot, plantar to dorsal orientation (PD Group). Standard surgical technique with fluoroscopy was used for each approach. Following fixation, each specimen was loaded to failure with a Bionix ® 858 MTS device, applying a downward axial force at a distance to create torque. Torque to failure was compared between DP and PD Groups using Student's t test, with p=0.05 used to determine statistical significance. RESULTS: Statistical analysis demonstrated that the mean torque to failure slightly favored the DP Group (37.3Nm) to the PD Group (32.2Nm). However, the difference between the two groups was not statistically significant (p=0.55). CONCLUSION: In subtalar arthrodesis, there is no significant difference in construct strength between dorsal-to-plantar and plantar-to-dorsal screw orientation. The approach chosen by the surgeon should be based on factors other than the biomechanical strength of the screw orientation.
Asunto(s)
Artrodesis/métodos , Tornillos Óseos , Articulación Talocalcánea/cirugía , Artrodesis/instrumentación , Fenómenos Biomecánicos , Cadáver , Calcáneo/cirugía , Humanos , Reproducibilidad de los Resultados , Astrágalo/cirugía , Torque , Insuficiencia del TratamientoRESUMEN
ABSTRACT Objective To compare screw fixation strength for subtalar arthrodesis. Methods Eight matched pairs of cadaver feet underwent subtalar joint arthrodesis with two 7.3mm cannulated screws. Randomization was used to assign screw orientation, such that one foot in each pair was assigned dorsal to plantar screw orientation (DP Group), and the other foot, plantar to dorsal orientation (PD Group). Standard surgical technique with fluoroscopy was used for each approach. Following fixation, each specimen was loaded to failure with a Bionix ® 858 MTS device, applying a downward axial force at a distance to create torque. Torque to failure was compared between DP and PD Groups using Student's t test, with p=0.05 used to determine statistical significance. Results Statistical analysis demonstrated that the mean torque to failure slightly favored the DP Group (37.3Nm) to the PD Group (32.2Nm). However, the difference between the two groups was not statistically significant (p=0.55). Conclusion In subtalar arthrodesis, there is no significant difference in construct strength between dorsal-to-plantar and plantar-to-dorsal screw orientation. The approach chosen by the surgeon should be based on factors other than the biomechanical strength of the screw orientation.
RESUMO Objetivo Comparar a força de fixação dos parafusos para artrodese subtalar. Métodos Oito pares de pés de cadáveres frescos foram submetidos à artrodese da articulação subtalar com dois parafusos canulados de 7,3mm. A randomização foi usada para atribuir a orientação do parafuso, de modo que um pé em cada par foi designado com orientação de dorsal para plantar (Grupo DP), e o outro pé com orientação de plantar para dorsal (Grupo PD). Técnica cirúrgica padrão com radioscopia foi usada para os procedimentos. Após a fixação, cada amostra foi testada até a falha com um dispositivo Bionix®858 MTS, aplicando força axial descendente a uma distância para criar torque. O torque de falha foi comparado entre os Grupos DP e PD, usando o teste t de Student, com p=0,05 usado para determinar significância estatística. Resultados A análise estatística demonstrou que a média do torque até a falha favoreceu ligeiramente o Grupo DP (37,3Nm) em relação ao PD (32,2Nm). No entanto, a diferença entre os dois grupos não foi estatisticamente significativa (p=0,55). Conclusão Na artrodese subtalar, não há diferença significativa na força de compressão entre as orientações dos parafusos dorsal-plantar e plantar-dorsal. A abordagem escolhida pelo cirurgião deve ser baseada em outros fatores, sem preocupação com a força biomecânica da orientação dos parafusos.