Purpose: The 3-category rating of volar plate prominence in relation to the most volar edge of the distal radius (the watershed line) on lateral radiographs was reliable among a small group of surgeons and associated with the probability of flexor tendon irritation and potential rupture. Classifications are often less reliable when tested among a large group of practicing surgeons in different environments.
Methods: In this survey-based experiment, an international group of 115 fracture and upper extremity surgeons viewed 1 of 4 sets of 24 lateral radiographs (96 unique lateral radiographs) of patients with distal radius fractures who underwent volar plating in the practice of a single surgeon using 2 types of plates. Surgeons were asked to rate the following metrics: (1) the grade of plate prominence according to Soong, (2) whether the plate was more prominent than the watershed line, (3) whether the plate was separate from the bone distally, and (4) whether there is more than 5° of dorsal angulation of the distal radius articular surface.
Results: The interobserver agreement of the classification was "fair" (κ = 0.32; 95% confidence interval [CI] = 0.27-0.36), and grading was more reliable among surgeons who do not supervise trainees. Volar prominence was less reliable (κ = 0.034; 95% CI = 0.013-0.055) than plate separation from bone (κ = 0.50; 95% CI = 0.42-0.59) and more than 5° of dorsal angulation (κ = 0.42; 95% CI = 0.35-0.48).
Conclusions: Among a large number of international practicing surgeons, the classification of volar plate prominence in 3 categories was fair.
Clinical relevance: The diagnosis of plate prominence might develop toward criteria with moderate reliability, such as separation of the plate from the bone and residual angulation of the distal radius.
Keywords: Distal radius fractures; Soong classification; interobserver agreement; plate positioning; plate prominence; reliability; tendon rupture.
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