gms | German Medical Science

Objectives/Interrogation: The purpose of this study was to determine whether only one extension block Kirschner-wire was sufficient fixation for mallet finger fractures.

Methods: We reviewed 33 cases with a mallet fracture, involving more than one-third of the articular surface, with or without volar subluxation of the distal phalanx. There were 12 females and 21 males with a mean age of 35.4 years (15 to 62). A case injured his index finger, thirteen cases their middle finger, thirteen cases their ring finger, and six cases their little finger. We measured transverse diameter of the proximal fragment and whole distal phalanx in the axial view of computed tomography (CT), then ratio of proximal fragment size was calculated. The fragment deviation from center of distal phalanx was evaluated in the three dimensional reconstruction image of CT. The deviation defined the percentage which the length between fragment center and whole distal phalanx center divided by transverse diameter of the proximal fragment and whole distal phalanx.

Results and Conclusions: The mean joint surface involvement was 50.6% (33% to 71.7%) in sagittal view of CT. The average of transverse diameter and ratio of the proximal fragment was 7.4mm and 75.2%, respectively. There was the case whose proximal fragment was less than half of distal phalanx diameter. The mean deviation from center of distal phalanx was 3.1%. The largest deviation was 10.3%. The proximal fragment was broken into 2 pieces in the 2 cases. In conclusion, in the case of one part fragment, it was able to support the proximal fragment with the central extension block of distal phalanx. But in the case of two parts fragment, one part was supported with the extension block, whereas another part was not supported. And so, only one extension block may be insufficient. We evaluated the size and the deviation of the proximal fragment by CT. It was difficult to evaluate correctly them by plain radiograph, therefore the preoperative CT evaluation was useful. In the future, the injury mechanism should be solved for the case of two parts fragment.