Biomechanical comparison of plantar-to-dorsal and dorsal-to-plantar screw fixation strength for subtalar arthrodesis

• Published in: Einstein (São Paulo, Brazil) Vol. 18; p. e0AO5052
• Main Authors: Chaudhari, Nileshkumar, Godoy-Santos, Alexandre Leme, Netto, Cesar de Cesar, Rodriguez, Ramon, Dun, Shouchen, He, Jun Kit, McKissack, Haley, Fleisig, Glenn S, Pires, Eduardo Araujo, Shah, Ashish
• Format: Journal Article
• Language: English
• Published: Brazil Instituto Israelita de Ensino e Pesquisa Albert Einstein 01.01.2020
• Subjects: Ankle; Arthritis; Arthrodesis; Arthrodesis - instrumentation; Arthrodesis - methods; Biomechanical Phenomena; Bone Screws; Cadaver; Calcaneus - surgery; Humans; Joint diseases; Joint instability; MEDICINE, GENERAL & INTERNAL; Original; Reproducibility of Results; Subtalar joint; Subtalar Joint - surgery; Talus - surgery; Torque; Treatment Failure; Ankle; Tornozelo; Joint instability; Artropatias; Subtalar joint; Articulação subtalar; Instabilidade articular; Arthrodesis; Arthritis; Joint diseases; Artrite; Artrodese
• ISSN: 1679-4508; 2317-6385; 2317-6385
• DOI: 10.31744/einstein_journal/2020AO5052

To compare screw fixation strength for subtalar arthrodesis. 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. 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). 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.