Biomedical subjects
Publications and source records attributed to N Stärk.
There is a good chance to reduce the scaring between conjunctiva, Tenon's capsule, muscle and sclera after surgical treatment of rectus and oblique muscles if a careful reconstruction of Tenon's capsule is made. In the rare cases that you have to reoperate, you will experience the benefit of these additional stitches (7-0 vicryl) that restore the integrity of Tenon.
In patients with malignant tumors in the region of the shoulder, radical resection can avoid amputation in most instances. To improve the function of the arm, endoprosthetic replacement of the defect is desirable. A three-component endoprosthesis made of a bioceramic material (aluminium oxide) was designed, implanted without bone cement. Fast anchorage to bone is achieved by using a conical sleeve, fixed upon the previously conically reamed humerus shaft. A stable primary fit is always feasible. Subsequent bone in growth into grooves inside the conical sleeve provides a permanent anchorage of the endoprosthesis. The authors experiences are based on implantations of 38 endoprostheses. The original diseases were primary malignant bone tumors in 19 patients, one case of "solitary" plasmocytoma and metastases into the proximal humerus in 16 patients. In two women, resection was made because of posttraumatic subcapital humeral pseudarthrosis. The follow-up study includes only those 27 cases operated on at least one year ago. 12 of the 14 patients with primary tumors have been surviving for 12-55 months (range 27.4) without signs of metastases or recurrent disease. Seven patients with metastases died of their original diseases after 7.7 months on the average. Owing to extensive resection of the shoulder musculature the mobility in the shoulder joint is considerably reduced. All the patients have good movement of the elbow joint and free function of the hand.
The tenotomy or tenectomy of an overactive superior oblique produces a similar effect as an elongation of the tendon. Its efficiency cannot be compared with the tenotomy or myotomy of an overactive inferior oblique or rectus muscle. No discernible underaction or complete paralysis of the superior oblique are to be feared, if the surgical indication and technique are correct. We prefer the tenotomizing of the overactive superior oblique to the recession of its insertion. Commonly, but still not always, the overaction of the superior obliques is associated with an A syndrome. Besides, the tenotomy and tenectomy of the superior oblique may be useful in true Brown's syndrome and as an additional procedure in cases of paralysis of the two elevators of one eye, During the past four years this operation was done 32 times on 24 patients. In none of these cases an insufficiency of the superior oblique was produced.
Dense, highly pure A12O3 ceramic not only shows excellent wear resistance and tissue biocompatibility, but also has sufficient mechanical strength for loaded endoprostheses. The necessary diameter size of the material to sustain adequate shear stresses can be achieved, if the endoprosthesis is attached extracortically to the conically truncated long bone according to the principle of the conical sleeve. Extracortical attachment of the endoprosthesis causes minor nutritive damage since long bones derive their vascular supply mainly from the medullary cavity. In this way a primary stable and loadable connection is established, which is a prerequisite for permanent anchorage of the implant through new bone formation. After experiments in 12 dogs bioceramic endoprostheses were implanted in a total of 40 human patients using this technique of extracortical attachment (12 hip joints, 24 proximal humeri, 4 special constructions). Thirty-six of these implants were stable after observation periods ranging from one to 49 months. A stable anchorage of the prostheses to the pre-existing bone through new bone formation could be demonstrated histologically. The above preliminary results show that bioceramic endoprostheses can be "incorporated" in the skeleton and possibly also withstand the functional stresses.
A new total hip endoprosthesis for implantation without bone cement is reported. This prosthesis consists of a ceramic socket and a titanium femoral component which is covered with a ceramic layer (Al2O3). The proximal end of the femoral component is shaped to a conus on which a ceramic ball for articulation with the socket is placed. Beside the construction principles the implantation technique and first clinical experiences are described.
This paper describes the design principles of a new endoprosthesis made of dense aluminum oxide (A12O3) and implanted without bone cement. Mechanical tests and animal experiments have proved the sufficient mechanical strength of the bone-prosthesis connection as well as the biocompatibility of the material. So far, 12 tumor patients selected according to strict indication criteria have been operated on. Both the clinical-radiologic and the first histological findings available are encouraging. Special reference is made to the first fully ceramic total hip joint endoprostheses implanted in a human without bone cement.
The results of penalisation treatment are given in the cases of 233 children with squint and 9 with amblyopia without a squint angle. With regard to amblyopia treatment penalisation is indeed not so effective as direct total occlusion, but it can be used, for example when the parents or children fight against the occlusion or when a plaster allergy is present. Even in school children the near-penalisation in cases of amblyopia diagnosed too late can bring very satisfactory visual improvements (in over 50%), provide care and stamina are present. For prophylaxis against amblyopia, the penalisation is especially suitable. In only 1/3 of cases the squint angle becomes obviously smaller, and signs of incomitance are not affected. Less than one third incomitance are not affected. Less than one third of the children attain with penalisation alone binocular vision--and even this usually on the basis of anomalous development.
A cement-free bioceramic aluminum oxide double cup endoprosthesis is under investigation as an alternative to the cemented stem endoprosthesis. Nine patients with 11 operated hips are without complaints after an average of 20.8 months (range 8--28 months). Early loosening of 2 femoral components occurred because of technical mistakes during operation. In 3 patients loosening of the femoral component was seen 5--7 months after surgery. Mobilization of the hip joint and walking capacity are similar to the usually implanted stem endoprosthesis. Stable long-lasting anchorage is possible if the femoral component is implanted in valgus position and in contact with living bone. Failures are treated by a traditional type of endoprosthesis.