The Journal of hand surgery
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The compressive force generated by a 3.5 mm ASIF cannulated cancellous screw with a 5 mm head was compared with that generated by a standard 3.5 mm ASIF screw (6 mm head), a 2.7 mm ASIF screw (5 mm head), and a Herbert screw. The screws were evaluated in the laboratory with the use of a custom-designed load washer (transducer) to the maximum compressive force generated by each screw until failure, either by thread stripping or by head migration into the specimen. ⋯ The 3.5 cannulated screw generated greater compressive forces than the Herbert screw but less compression than the 2.7 mm and 3.5 mm ASIF cortical screws. The 3.5 mm cannulated screw offers more rigid internal fixation for scaphoid fractures than the Herbert screw and gives the added advantage of placement over a guide wire.
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Comparative Study
Biomechanical comparison of cannulated small bone screws: a brief follow-up study.
The compressive forces generated by the ASIF and Herbert small bone cannulated screws were measured in the laboratory with the use of simulated bones and a custom-designed load washer as a means of quantifying their fixation capabilities. Comparative data were also generated for the Herbert scaphoid bone screw and the ASIF 4 mm cancellous screw. ⋯ Both generated compression forces approximately five times those of the Herbert scaphoid bone screw. The ASIF small cannulated screw demonstrated a compressive capacity 2 1/2 times that of the Herbert screw.
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The extensor medii proprius is a muscle analogous to the extensor indicis proprius in that it has a similar origin, but inserts into the long finger. The extensor indicis et medii communis muscle is an extensor indicis proprius muscle that splits to insert into both the index and long fingers. The extensor tendons to the fingers were dissected in 58 adult hands to determine the incidence and anatomy of the extensor medii proprius and extensor indicis et medii communis. ⋯ The tendon slip of the extensor indicis et medii communis inserting into the long finger did not insert into the dorsal aponeurosis, but into the deep fibrous tissue near the metacarpophalangeal joint. Both the extensor medii proprius and the extensor indicis et medii communis may represent evolutionary remnants. Awareness of their potential presence and anatomy should be helpful in extensor identification, repair, and transfer.