Interfragmentary compression across a simulated scaphoid fracture—analysis of 3 screws1
Section snippets
Materials and methods
Thirty-two fresh frozen cadaveric scaphoids were used and all soft tissues were removed before storage at −20°C until testing. The average specimen age was 72 years (range, 40–88 years). Three different scaphoid screw systems were tested: the Acutrak Standard, the Acutrak Mini, and the Bold. The gender and side of the specimens were similar between the groups (Table 1).
The Bold screw (Fig. 1) is of similar design to the Herbert screw12 with a central threadless shaft and differential pitch
Results
The average screw length and range were 26.3 mm (22.5–30.0 mm) for the Acutrak Standard, 25.8 mm (24.0–26.0 mm) for the Acutrak Mini, and 28.8 mm (26.0–32.0 mm) for the Bold. This length incorporates the interposing load cell; therefore screw lengths in vivo would be approximately 2 sizes (5 mm) shorter.
Five minutes after screw insertion we found a significant difference in the magnitude of interfragmentary compression produced by the 3 different screws (p = .01) (Table 2, Fig. 3). The
Discussion
We found that the Acutrak Standard screw produced significantly more compression across a simulated scaphoid fracture (152 ± 21 N) than either the Bold (103 ± 46 N) or Acutrak Mini screws (92 ± 56 N) (p = .01) and that it was more consistent, as reflected by the lower standard deviation. The compressive force achieved by the Acutrak Standard and Mini screws was better sustained over time than that of the Bold screw, with which a small but significant loss of compression was noted in the 5
Acknowledgements
The authors would like to thank Acumed (Hillsboro, OR) and Wright (Arlington, TN) for providing their respective screws and instruments for testing.
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