gms | German Medical Science

Objectives/Interrogation: Many authors have reported the good results of the extension block technique described by Ishiguro et al. for the treatment of mallet fractures. However, there are several cases that postoperative extension lag and incongruity of joint surface remain. We aimed to evaluate the clinical results using preoperative three-dimensional computed tomography (3D-CT).

Methods: Between 2012 and 2017, 23 patients (11 men and 12 women; mean age, 35.4 years; range, 12-70 years) with mallet fractures were treated using the extension block pinning by Ishiguro method. Konishiike et al. classified the mallet fractures into 4 types: type 1, avulsion; type 2, rotate avulsion; type 3, split avulsion; and type 4, split compression. According to this classification, there were 3 cases of type 1, 5 cases of type 2, 7 case of type 3, 8 case of type 4. Evaluation of preoperative 3D-CT was classified as center (non-deviation group) and ulnar or radial side (deviation group) in the deviation direction of the bone fragment. Patient outcomes were assessed with DIP range of motion measurement, radiographic examination, range-of-motion measurements, and Crawford classification.

Results and Conclusions: This mean follow-up period was 4.2 months (range, 2-12 months). In preoperative 3D-CT, the non-deviation group were 15, and the deviation group were 8. In Konishiike classification, type 4 was the most frequent in the no-deviation group and type2 was the most frequent in the deviation group. At the final follow-up, the mean extension angle in the non-deviation group was -8.6°, which was significantly different from that of the deviation group (mean, -16.8°). The step-off was seen in the deviation group significantly compared with the no-deviation group in the X-ray. Crawford classification was no significant difference between the non-deviation and the deviation group. It is considered restoring the joint surface with accurate reduction to be important to prevent secondary osteoarthritis, and loss of movement. In the evaluation of bone fragment for mallet fractures, it may be difficult to assess the displace of it in the X-ray. In the preoperative 3D-CT evaluation, the clinical results were poor in the deviation group compared with the no-deviation group. Therefore, 3D-CT examination is a useful, and it is suggested that it will help to determine the surgical technique for mallet fractures.