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Sunday, September 30, 2018: 10:30 AM
PURPOSE: The desire to avoid flexor tendon injury after volar plating of distal radius fractures has lead to a myriad of new plate designs. However, the rate of innovation has outpaced the data addressing whether these new models actually decrease the rate of tendon injury. The purpose of this study is to determine whether the designs of three representative distal radius plates impact the amount of force exerted on the FDP and FPL tendons when the plates are placed proximal and distal to the watershed line.
METHODS: Three commercially available plates, including a 2.0 mm thick FPL sparing plate, a 2.0mm adaptive plate, and a 1.6mm babyfoot plate were applied to ten fresh, matched-pair upper extremity specimens fixed to a custom jig to mimic pinch grip. Plates were placed at various positions relative to the watershed line. External cyclical loading was applied to the FPL and FDP tendons, and the force generated between each tendon and plate was measured with a thin, flexible pressure sensor. Linear mixed effect models were used to evaluate differences in maximum and mean force by plate position and plate design.
RESULTS: The maximum and mean force on the FPL and FDP tendons differed significantly between positions relative to the watershed line, as measured by Soong grade. For the FPL tendon, the maximum force experienced with a plate in Soong 2 was 4.50 [95% CI: 2.8, 7.3] times higher than when the plate was in a Soong 0 placement, and 4.63 [95% CI: 2.82, 7.61) times higher for the FDP tendon. There was a consistent trend towards a decreased maximum and mean force with the babyfoot plate, likely due to the thinner plate profile, although this difference did not achieve statistical significance.
CONCLUSIONS: The main determinant of plate prominence and therefore flexor tendon injury potential is placement in relation to the watershed line. While not statistically significant, decreased observed force values with a thinner plate indicate that plate thickness could also represent a clinically meaningful difference in plate prominence. Due to the variability in distal radii, use of the Y-shaped, FPL sparing plate does not lead to a consistent decrease in force on the FPL tendon in comparison to other plate designs. Our results do not clearly show superiority of one plate type, but suggest that decreasing the overall plate profile may have greater utility in preventing flexor tendon injury than anatomic plate design.
METHODS: Three commercially available plates, including a 2.0 mm thick FPL sparing plate, a 2.0mm adaptive plate, and a 1.6mm babyfoot plate were applied to ten fresh, matched-pair upper extremity specimens fixed to a custom jig to mimic pinch grip. Plates were placed at various positions relative to the watershed line. External cyclical loading was applied to the FPL and FDP tendons, and the force generated between each tendon and plate was measured with a thin, flexible pressure sensor. Linear mixed effect models were used to evaluate differences in maximum and mean force by plate position and plate design.
RESULTS: The maximum and mean force on the FPL and FDP tendons differed significantly between positions relative to the watershed line, as measured by Soong grade. For the FPL tendon, the maximum force experienced with a plate in Soong 2 was 4.50 [95% CI: 2.8, 7.3] times higher than when the plate was in a Soong 0 placement, and 4.63 [95% CI: 2.82, 7.61) times higher for the FDP tendon. There was a consistent trend towards a decreased maximum and mean force with the babyfoot plate, likely due to the thinner plate profile, although this difference did not achieve statistical significance.
CONCLUSIONS: The main determinant of plate prominence and therefore flexor tendon injury potential is placement in relation to the watershed line. While not statistically significant, decreased observed force values with a thinner plate indicate that plate thickness could also represent a clinically meaningful difference in plate prominence. Due to the variability in distal radii, use of the Y-shaped, FPL sparing plate does not lead to a consistent decrease in force on the FPL tendon in comparison to other plate designs. Our results do not clearly show superiority of one plate type, but suggest that decreasing the overall plate profile may have greater utility in preventing flexor tendon injury than anatomic plate design.