Assessment of Fracture Line Angle in Mallet Fractures.

Background: Surgery is often offered to patients with mallet fractures that have a large, displaced fragment and/or joint subluxation. However, the surgical approach remains a subject of debate, and surgery is frequently associated with unsatisfactory outcomes. We felt that the angle formed by the fracture line and the long axis of the distal phalanx on a lateral view radiograph (fracture line angle [FLA]) could be useful in determining the appropriate treatment strategy. The aim of this study was to assess the FLA and its distribution in mallet fractures. Methods: Three researchers measured the mallet FLA and the percentage of articular surface (PAS) involved in the lateral radiographs of 103 patients with a mallet fracture. Results: There was a strong correlation between the mallet FLA and the percentage of joint surface involvement between the three researchers. The mean FLA was 42.59° (±11.54) and it ranged from -1 to +1 standard deviation in 73 individuals (70.87%). The FLA varied over a wide range, while clustering near the average value. The average PAS involvement was 46.5% (±8.7%). There was no correlation between FLA and PAS involvement (p > 0.05). Conclusions: It is possible to quantify the mallet FLA accurately and consistently. It varies widely, regardless of the PAS involvement. When choosing the type of treatment and making prognostic predictions, the mallet FLA may be a helpful guide. Level of Evidence: Level IV (Diagnostic).