Rethinking Lafontaine Criteria: Second Metacarpal Cortical Percentage as a Reliable Predictor of Distal Radius Fracture Instability

Background: Distal radius fractures represent a significant cause of morbidity and loss of independence, particularly in older patients. There is no good consensus on which fractures managed nonoperatively will be unstable in a cast or splint other than Lafontaine criteria, the only relevant clinical study to date. Second metacarpal cortical percentage (2MCP) has been shown to be a reliable predictor of osteoporosis and poor bone quality. This study investigates the utility of 2MCP as an independent predictor of fracture displacement in nonoperative fracture management. Methods: A retrospective cohort of distal radius fractures treated conservatively over 7 years (2013-2020) was investigated. Injury, postreduction, and 4-week follow-up radiographs were reviewed for 2MCP, volar tilt, ulnar variance, and other demographic factors. Multivariate regression analysis was used to predict fracture displacement. Results: Only 2MCP and initial fracture displacement were associated with displacement at 4 weeks (P =.008, P =.008). Other than initial fracture displacement, Lafontaine criteria were not associated with radiographic outcomes. A 2MCP threshold of 53.5% optimized sensitivity (67.5%) and specificity (70.2%) in predicting 10° of fracture displacement (P =.003). A 2MCP threshold of 49.5% was 86.7% sensitive and 74.7% specific at detecting dorsal malunion (P =.032). Conclusions: Second metacarpal cortical percentage is a useful clinical tool in predicting distal radius fracture instability. Clinicians can use 2MCP both in guiding decision-making when selecting patients who may benefit from operative management and as a screening tool for osteoporosis and initiation of antiresorptive therapy.