gms | German Medical Science

Objectives/Interrogation: Several surgical methods are described for the treatment of the mallet fracture. Most closed techniques use a K-wire fixation through the distal interphanageal (DIP) joint for temporary transfixation. Multiple tries to achieve an acceptable K-wire position may cause cartilage damage and increase the risk of a joint infection. Based on the Ishiguru technique, we describe a new method, using a single K-wire, without transfixation of the DIP joint. The purpose of the study is a biomechanical comparison of the new surgical technique to the proven technique according to Ishiguru.

Methods: 32 fingers (Digit 2-5) from 4 freshly frozen hand pairs were disarticulated at the PIP joint and fixed in PMMA. Exclusion criteria were previous soft tissue injuries, fractures and loose fingernails. The hands were randomized to have a donor's hand in each group. The fractures were created with a flat chisel under fluoroscopic control. Including criteria were fractures up to 30% of the articular surface and subluxation of the distal phalanx. One group was treated using the Ishiguru method and the other group using the new fixation method. We use single K-wire which enables indirect fracture fragment fixation, as described in the original Ishiguru technique. The same K-wire is bent distally over the fingernail and is fixed with a special device without intra-articular K-wire transfixation of the DIP joint. The fingers underwent a cyclic load test consisting of 2000 cycles with a load between 1N and 7N. After this cyclic test, a load to failure test was performed. The load applicator was applied to the finger nail. X-rays were taken every 500 cycles, and again after the load to check the reduction and the plastic deformation.

Results and Conclusions: So far, 14 fingers have been tested. All fingers in the fixator group were superior in both maximum load and stiffness (max. load mean 29N and 19N, p=0.0014, stiffness mean 4N/mm and 8N/mm, p=0.0086). There was no significant difference in the plastic deformation and loss of reduction after the cyclic load test. The first fingers were tested with a force of 10N. The Ishiguru group failed immediately in the first cycles; therefore the cycling load was reduced to 7N.

The remaining test results are pending. The initial biomechanical test results demonstrated superiority to an already established method. We could demonstrate higher biomechanical stiffness without intra-articular K-wire placement avoiding cartilage damage. Further applications are being tested.