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 ( = .008, = .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 ( = .003). A 2MCP threshold of 49.5% was 86.7% sensitive and 74.7% specific at detecting dorsal malunion ( = .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.