Factors Associated with Loss of Reduction of Volar Ulnar Rim Fragments following Volar Locking Plate Fixation of Intra-articular Distal Radius Fractures
Rachel E Cross, BA1, Justin McCarty, DO, MPH1, Charlotte Louise Ernestine Laane, MD1, Yannick Albert J. Hoftiezer, MD1, Aquiles Gavagnin, MD2, Pietro Regazzoni, MD3, Alberto Fernandez Dell'Oca, MD2, Jesse B Jupiter, MD4 and Abhiram R. Bhashyam, MD, PhD5, (1)Massachusetts General Hospital, Boston, MA, (2)Hospital Britanico Montevideo, Montevideo, Montevideo, Uruguay, (3)University Hospital of Basel, Basel, Basel, Switzerland, (4)Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Boston, MA, (5)Massachusetts General Hospital / Harvard Medical School, Boston, MA
Hypothesis: To assess factors associated with loss of reduction of volar ulnar fragments following volar locking plate (VLP) fixation of intra-articular distal radius fractures. We hypothesized that volar ulnar fragment (VUF) size and plate placement would be critical variables driving the incidence of volar rim loss of reduction.
Methods: All patients with a volarly displaced, intra-articular distal radius fracture treated with a VLP within the ICUC database, an international collaborative and publicly available dataset, were identified. The primary outcome was volar rim loss of reduction on follow-up imaging, defined as a change in radiographic alignment from intra-operative fluoroscopy, teardrop angle less than 50 degrees, or loss of normal radiocarpal alignment. Secondary outcomes were final range of motion (ROM) of the affected extremity. Radiographic Soong classification was used to grade plate position. Traditional descriptive statistics were used to compare patient, fracture, and treatment characteristics with volar rim loss of reduction. A Random Forest supervised machine learning algorithm was used to classify variable importance for predicting the primary outcome.
Results and Conclusion: Fifty patients with volarly displaced, intra-articular distal radius fractures treated with VLP were identified. Six patients were observed to have a volar rim loss of reduction, but none required reoperation. Volar ulnar fragment size, Soong grade 0, and post-fixation axial plate position in relation to the sigmoid notch were significantly associated (p<0.05) with volar rim loss of reduction. All cases of volar rim loss of reduction occurred when VUF was 10.8 mm or less. The size of the VUF was the most important variable for predicting volar rim loss of reduction, followed by post-fixation axial plate position in relation to the sigmoid notch and the number of volar fragments in the Random Forest machine learning algorithm.
Summary: • Size of the volar ulnar fragment was the variable classified as having the most importance for volar rim reduction loss after VLP and occurred when the size was less than 10.8 mm.
• Variables significantly associated (p<0.05) with volar rim reduction loss include volar ulnar fragment size, Soong grade 0, and post-fixation axial plate position in relation to the sigmoid notch.
• Fracture characteristics can influence the treatment approach to address these risk factors.
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