RESUMEN
BACKGROUND: We assessed factors associated with change in radiographic teardrop angle following volar locking plate (VLP) fixation of volarly displaced intra-articular distal radius fractures with volar ulnar fragments (VUF) within the ICUC database. The primary outcome was change in radiographic alignment on follow-up imaging, defined as a change in teardrop angle from intra-operative fluoroscopy greater than 5°. METHODS: Patients with distal radius fractures 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°, 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. Descriptive statistics were used to assess variables' distributions. A Random Forest supervised machine learning algorithm was used to classify variable importance for predicting the primary outcome. Traditional descriptive statistics were used to compare patient, fracture, and treatment characteristics with volar rim loss of reduction. Volar rim loss of reduction and final ROM in degrees and as compared with contralateral unaffected limb were also assessed. RESULTS: Fifty patients with volarly displaced, intra-articular distal radius fractures treated with a 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 postfixation axial plate position in relation to the sigmoid notch were significantly associated (P < .05) with volar rim loss of reduction. All cases of volar rim loss of reduction occurred when VUF was 10.8 mm or less. CONCLUSIONS: The size of the VUF was the most important variable for predicting volar rim loss of reduction followed by postfixation plate position in an axial position to the sigmoid notch and the number of volar fragments in the Random Forest machine learning algorithm. There were no significant differences in ROM between patients with volar ulnar escape and those without.
RESUMEN
BACKGROUND: The Soong classification grades the prominence of volar locking plates used to treat distal radius fractures in relation to the volar rim. The basis of the classification scheme is that increasing plate prominence over the volar rim and distal radius watershed zone is associated with increased likelihood of flexor tendon irritation and need for plate removal. However, recent studies report mixed results on the predictive value of the Soong classification for these outcomes. We hypothesized that the decreased predictive accuracy of Soong classification is due to misclassification between Soong grades secondary to a suboptimal correlation between the Soong classification on radiographs (XRs) and computed tomography (CT). METHODS: Fifty volarly displaced distal radius fractures treated with a volar locking plate in the international and publicly available ICUC database were reviewed. All cases with a postoperative XR and CT were included. Soong classification of the volar locking plate in relation to the volar ulnar rim was determined on both XR and CT by 2 independent, fellowship-trained hand surgeons using CT imaging as the gold standard. The distribution of Soong grades on XR and CT was compared using Pearson's χ2 test, and correlation was calculated using the Matthews correlation coefficient (MCC). A multi-class confusion matrix was used to calculate each grade's positive predictive value (PPV). RESULTS: We found an MCC of 0.65, indicating only moderate correlation between the 2 modalities. Per individual Soong grade, the PPV was the highest for grade 2 (0.96), with lower PPVs for grade 0 (0.63) and grade 1 (0.60). CONCLUSIONS: The distribution of Soong grades was significantly different when using XR versus CT (P < .001). LEVEL OF EVIDENCE: Oxford Centre for Evidence-Based Medicine, diagnostic, level 2b.
