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522 BIOMECHANICAL COMPARISON OF AN INTERNAL SPANNING WRIST PLATE AND AN EXTERNAL FIXATOR IN A HUMAN CADAVERIC MODEL OF DISTAL RADIUS FRACTURES.
  1. J. C. Wolf1,
  2. W. M. Weil2,
  3. D. P. Hanel2,
  4. T. E. Trumble2
  1. 1University of Washington School of Medicine, Seattle, WA
  2. 2Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA

Abstract

Background External fixation is a well-accepted surgical means of restoring hand and wrist function, but complications arise involving the percutaneous pins used to mount the external bar. An internal fixator placed across the fracture and secured by locked cortical screws to the radius and second metacarpal eliminates the need for pins. This study compares the biomechanical stability of distal radius fracture fixation with a new internal radiocarpal spanning locking plate, which acts as an internal distal radius fixator, versus a standard distal radius external fixator. The amount of locking screws necessary for optimal fixation of the plate was also assessed.

Study Design and Methods A 1 cm osteotomy was created in 10 cadaveric specimens to simulate an unstable distal radius fracture. An internal radiocarpal spanning 2.4 mm locked plate was fixed to the radius with four locking screws proximally and four distally. Sensors were attached across the fracture and the specimen was mounted into a loading device with cables attached to the two flexor and three extensor tendons. The tendons were incrementally loaded and fracture motion was measured. Proximal and distal screws were sequentially removed and the loads were repeated. The fixation was then changed to an external fixator and the loading tests were repeated.

Results Fracture fixation with the radiocarpal spanning 2.4 mm locking plate was significantly more stable with 4 screws proximally and 4 screws distally (4 × 4) and with the 3 × 3 configuration than with the external fixator in both flexion and extension (p values < .05). The 4 × 4 screw configuration was not significantly different from the 3 × 3 screw configuration (p values > .05). The 4 × 4 screw configuration was significantly more stable than the 2 × 2 and 1 × 1 screw configurations in both flexion and extension (p value < .05). All fixation configurations of the locking plate and the external fixator showed more fracture displacement at increasingly higher loading parameters.

Conclusions Fracture fixation with the new internal radiocarpal spanning 2.4 mm locking plate is more stable than with a standard distal radius external fixator. Only three locking screws proximally and three distally are required for optimal fixation of the locking spanning plate.

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