Biomedical subjects
Publications and source records attributed to U Maronna.
A distinction must be drawn between the older constrained prostheses, in which load was transferred via metal-coated hinges, and later models using the low-friction principle, where the axle is not load bearing. The latter show good long-term results. The greater stability of constrained prosthesis allows earlier and less complicated mobilization even of elderly patients.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Hollow prostheses appear to represent a promising approach for the durable fixation of cementless hip-joint endoprostheses. The goal of the planned development is the design-engineering, quality-assured production and clinical testing of hollow prostheses displaying largest possible interior space and optimized wall thickness. With hollow prostheses the possibility exists for the first time of filling both the interior space of the prosthesis and cavities between the prosthesis bearing and the prosthesis with spongiosa. Theoretical considerations indicate that this should result in early and durable secondary stability. First results from animal experiments show that the canine femora operated on display a stress distribution closely approximating the natural stress distribution in the bone and exhibit the expected ingrowth of spongiosa into the interior space of the hollow prosthesis. The choice of suitable materials and particularly of wall thickness and cross-sectional shape has a decisive bearing on the elastic behaviour of the prosthesis. Compared with a solid prosthesis of the same geometry, a hollow prosthesis exhibits reduced flexural rigidity and hence higher elasticity. The dynamic tests performed on hollow prostheses in line with DIN 58,840 have shown that--given careful design and manufacture as well as effective quality-assurance measures--fatigue failure is not to be expected in the case of hollow prostheses.
In objection to knee hinge prostheses there is often mentioned a higher complication rate. An increased load impact on the bone-cement interface results from the close connection of tibial and femoral components. This is assumed to cause bad results, as reported from early artificial knee joint replacements, characterised by weight bearing axes and direct contact metal to metal. These are contrasted to long term results of the Blauth hinge prosthesis. The Blauth prosthesis is constructed according to the low friction principle without a weightbearing axis. A prospective multicentric long term follow-up study reports on 556 prostheses. 463 (83%) were controlled between 1 and 15 years after operation (average: 43 months). Aseptic loosenings had to be confirmed in 1.3% of the patients, deep infections in 2.6%. The survival analysis did not show an erratic deterioration in dependence of the observation period. After 10 years there is still a probability of 89% that a prosthesis does not show a deep infection or loosening. The efficiency of artificial knee joint replacement by hinge joints should therefore not be judged on the results of the first generation of these models.
After an experience of two and a half years with the cementless total hip replacement after Judet we report about the preliminary results in special cases. The implantation of this model of prosthesis is not difficult in case of a good bony stock. We achieved also good results in special indications like in coxarthritis after CDH, hip protrusion and revisions of loosened endoprosthesis. Special techniques are pointed out to enlarge or improve the prosthetic anchorage.