The Relationship of Volar Plate Position and Flexor Tendon Rupture: Should We Question the Validity of the Soong Classification?

Background: The authors sought to determine the reliability of the Soong classification, which relates the position of the implant to the watershed line of the distal radius, for predicting flexor tendinopathy in distal radius fractures treated with volar plate fixation. Methods: Medical records were reviewed, including demographics, fracture and operative characteristics, tendon-related complications, and radiographic outcomes. Six hundred fifty-nine distal radius fractures were reviewed with a mean duration of clinical follow-up of 12.9 ± 0.7 months. Results: The incidence of isolated flexor tendinopathy and tendon rupture was 0.9 and 0.3 percent, respectively. The Soong classification failed to independently predict flexor tendon rupture or tendinopathy. Fractures classified as inadequately reduced were significantly associated with Soong grade 0 or grade 2, whereas adequately reduced fractures were significantly associated with Soong grade 1. Conclusion: The Soong classification is not the sole predictor of flexor tendinopathy and may be viewed as a reflection of the overall appropriateness of fracture reduction.