Number and locations of screw fixation for volar fixed-angle plating of distal radius fractures: biomechanical study

• Published in: The Journal of hand surgery (American ed.) Vol. 35; no. 6; p. 885
• Main Authors: Mehling, Isabella, Müller, Lars P, Delinsky, Katharina, Mehler, Dorothea, Burkhart, Klaus J, Rommens, Pol M
• Format: Journal Article
• Language: English
• Published: United States 01.06.2010
• Subjects: Aged; Aged, 80 and over; Biomechanical Phenomena; Bone Plates; Bone Screws; Equipment Failure Analysis; Female; Fracture Fixation, Internal - methods; Humans; Male; Middle Aged; Radius Fractures - surgery
• ISSN: 1531-6564
• DOI: 10.1016/j.jhsa.2010.03.027

To compare the biomechanical properties of different numbers and locations of screws in a multidirectional volar fixed-angle plate in a distal radius osteotomy cadaver model. We created an extra-articular fracture in 16 pairs of fresh-frozen human cadaver radiuses. The 32 specimens were randomized into 4 groups. All fractures were fixated with a multidirectional volar fixed-angle plate. We tested 4 different screw-placement options in the distal fragment. The distal fragment was fixed with 4 locking screws in the distal row of the plate in group a, and with 4 locking screws alternately in the distal and proximal rows in group b. In group c, 3 locking screws were used in the proximal row; in group d, 7 locking screws were used, filling all screw holes in the distal and proximal rows of the plate. The proximal fragment was fixed with 3 screws. The specimens were loaded with 80 N under dorsal and volar bending and with 250 N axial loading. Finally, load to failure tests were performed. Group d had the highest mean stiffness, 429 N/mm under axial compression, and was statistically significantly stiffer than the other groups. Group b had a mean stiffness of 208 N/mm, followed by group a, with 177 N/mm. Group c showed only a mean stiffness of 83 N/mm under axial compression. There were no statistically significant differences under dorsal and volar bending. In this model of distal radial fractures, there was a difference regarding the stiffness and the placement of screws in the distal rows of a volar fixed-angle plate. Inserting screws in all available holes in the distal fragment offered the highest stability. Using only the proximal row with 3 screws created an unstable situation. Based on these findings, we recommend placing at least 4 screws in the distal fragment and assigning at least 2 screws to the distal row of the multidirectional screw-holes.