Biomechanical comparison of distal locking screws for distal tibia fracture intramedullary nailing

Abstract

Background: Newer generation intramedullary (IM) tibial nails provide several distal interlocking screw options. The objectives were to determine: 1) if the new oblique interlocking option provides superior stability, 2) which screw orientation/ configuration is the most biomechanically stable, and 3) if three distal interlocking screws provide better stability. Methods: A preliminary experiment was performed in torsion, compression, and bending tests with four different screw configurations: (I) one medial-to-lateral and one oblique, (II) two me-dial-to-lateral, (III) one medial-to-lateral and one anterior-to-posterior, and (IV) one medial-to-lateral, one anterior-to-posterior and one oblique in simu-lated distal metaphyseal fracture tibiae. Twenty- four Synthes EXPERT tibial IM nails were used for six specimens of each screw configuration. Parts I and II, tibial IM nails were locked with 5.0 mm in-terlocking screws into simulated distal tibiae (PVC and composite analogue tibia). Part III, the two most stable configurations were tested using five pairs of simulated cadaveric distal tibiae metaphy-seal fractures. Results: Significant differences were attributable to distal screw orientation for intrame- dullary nailing of distal tibia fractures. Configura-tions II and IV were found to be more stable than the other two configurations. No significant differ-ence was detected in construct stability in all modes of testing between Configurations II and IV. Dis-cussion: Configuration I did not provide superior stability for the distal tibia fracture fixation. Con-figurations II and IV provided equivalent stability. When choosing IM fixation for treatment of distal tibia metaphyseal fractures two medial-to-lateral screws provide the necessary stability for satisfac-tory fixation. Clinical Relevance: This study indi-cated an option for operative treatment of distal metaphyseal tibia fracture fixation where preserva-tion of soft tissue and rigid stabilization are needed.