The increasing use of orthopaedic implants makes international efforts of standardization with their objectives unification and benefit of the patient necessary and sufficient. In 1975 an ISO-Draft for "bone-screws" has been finished. To get experimental data there was a test series of breaking bone-screws of five producers by torsional stress. Comparable screws showed considerable differences. The control of conformity to standards gave partially distinct differences to the standard profile and different hardness values, what affects to the screws' security of twisting off.
Fracture of the distraction rod is one of the complications following operative treatment of scoliosis by the device of Harrington. It is reported to occur in about 7% of cases. We found this complication twice in our own number of 41 patients during a follow up period of 1 to 4 years. The rods had broken 18 and 23 months after operation, but we never saw a breakage in the 1st postoperative year during the time of cast fixation. The fracture surfaces of each rod were examined under the scanning electron microscope. In one case a fatigue fracture with two beginnings at the opposite sides of the rod was found in combination with a forced fracture in the middle. The number of alterations of load from the beginning of the fracture to the complete breakage was about 10,000. The X-ray showed a loss of correction in the curve of 20 degrees with a pseudoarthrosis visible in the fusion. In the other case a typical pure fatigue fracture was seen 23 months after the operation with 18,000 alterations of load. The X-ray showed only a slight loss of correction of less than 5 degrees and no pseudoarthrosis was visable, neither in the X-ray nor in the operative exploration of the fusion. The breakage of the distraction rod results not only from a pseudoarthrosis but also from other explained facts of the procedure. Further treatment depends on a proven pseudoarthrosis.
In addition to the improved, universal unsable, electronic-hydraulic directed hip-joint-simulator type "MUNCHEN I", a new simulator with simplified construction has been developed. This mechanical hip-joint-simulator is marked by a dual drive of movement and strain mechanism, that has been realized by a toothed belt drive. The adjustable, three-axial movement simulates level walking. According to its special, easier design the new simulator is highly adapted for comparative testing of total hip endoprostheses regarding the fields of quality improvement or standardization testing.
A follow-up study on 160 patients with an arthrodesis of the ankle and/or subtalar joint has been made. Besides clinical and roentgenological examinations the gait of the patients was checked with a new electronic device. In addition we tested the pressure distribution underneath the sole of the affected foot and compared it to the contralateral side. This was found to be a valuable contribution to the examination methods used and can help to give a more objective judgement of the patients subjective complaints. Besides confirming known facts it was found that there were divergent results of electronic gait studies from examinations which are based on the usual clinical and X-ray studies. This may help to improve the patient's gait by correcting mechanical aids or, in rare cases, indicating another operation.
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