Biomedical subjects

T Hopf

Publications and source records attributed to T Hopf.

39 records · Page 3Linked to original sources

PubMedDate not supplied

[Improving fiber adhesion by surface oxidation in carbon fiber reinforced bone cement].

The mechanical superiority of carbon fiber reinforced PMMA containing additional apatite was shown previously. For further improvement these carbon fibers were now submitted to a superficial oxidation treatment by HNO3. A closer contact between the carbon fibers and PMMA and even trabeculae-like adhesions were detected by Scanning Electron Microscopy. The fatigue strength of the carbon fiber reinforced bone cement could be increased at 17% by this oxidation treatment. This increase, however, is less than that observed in the case of other fiber reinforced composites. Most likely this is caused by the pronounced polymerisation contraction of PMMA. Further improvement of the adhesion of the fibers to cement may be achieved by different oxidation techniques, further extraction of foreign substances or graft polymerization of the carbon fibers by PMMA or other polymers.

Adhesiveness↗

PubMedDate not supplied

[Interfragmental compression of the Zespol osteosynthesis system. Experimental biomechanical studies].

Apart from the advantages of plate osteosynthesis, like primary bone healing and immediate post-operative mobilisation treatment, the disadvantages of this method must be mentioned. First of all these are the high pressure on the surface of the bone by the plate and the high tension stress on the bone by the thread of the screws, which can lead to bone atrophy. Besides the splinting by the plate is accompanied by a functional lack of the bone. The bone reacts on this "stress protection" by reduction of material, especially under the plate. These disadvantages shall be avoided by a new osteosynthesis system, called ZESPOL, which has been developed in Poland. Here the plate does not contact directly the bone, but is fixed above the periost by special screw bolts. Although this method is used in Poland clinically with success, until now no experimental examinations concerning the stability of this osteosynthesis have been published. In the following biomechanical tests we examined, whether the new method achieves a comparable interfragmental compression like common selfcompressing plate systems. We measured the maximal interfragmental compression with an interposed piezo-electric element on human cadaver tibiae. Because the original ZESPOL plates have greater dimensions than common plates, we did not use these original plates. In order to get a comparability between the two systems, we modified small Autocompression plates (ACP) by milling a slot in the underside, so that they could be used with the original ZESPOL screw bolts. These modified ZESPOL plates we compared with common 6-hole Autocompression plates and cortical screws.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMedDate not supplied

[Experimental studies of the optimal plate pre-bending angle in compression osteosynthesis with reference to the plastic-elastic behavior of the osteosynthesis plate].

In order to achieve uniform pressure distribution in the osteotomy crack, the plate used in plate osteosynthesis has to be over-bent prior to fixation. To determine experimentally the extent to which the plate is usually pre-bent "intuitively", the bone axis was measured with narrow autocompression plates pre-bent at various angles on bones of cadavers, using a laser-optic system. The optimal pre-bending angle for the six-hole plate was found to be 3-5 degrees, for the eight-hole plate 5-6.5 degrees. The importance of the sliding-hole screw with regard to stability is pointed out. Both elastic and plastic deformation are affected when the plate bends back. However, the strength of the osteosynthesis is only affected by the plastic portion. An examination of the plate after osteosynthesis revealed the 20-30% of the original pre-bending had been lost; this corresponds approximately to the plastic portion.

Bone Plates↗