[Biomechanical tests on osteosynthesis with small-bone plates (author's transl)].

Plating in handsurgery has become a more frequently used method since the special instruments of the Swiss AO and the self-compression plates of Mittelmeier (made by Osteo AG) have been introduced. The results of biomechanical measurements, comparing the interfragmental compression power and tensile strength of the small-fragment-plates of the AO with the crescent-formed plates of Mittelmeier are reported. The compression power of the first reach their maximum by 8 kp, the latter an average of 20 kp. A gapping of the fracture occures under a deflection-momentum of 4 kp - cm using AO-plates and 10 kp - cm using the crescent-formed plates. The bending stiffness under deflection momentum to the off side of the plate is in the crescent plate 10 times higher. Only an angulating bending in the middle gives in both plates an all over good contact to the fragments. Finger osteosyntheses are very rigid against a deflection momentum in the level of the plate. (Regarding that, we fixe the plate sidewise on the bone.) Our conclusion is, that the better biomechanical stability of the self-compression plates--Mittelmeier-plates--is a result of the higher compression powers.