Biomedical subjects

H Siegrist

Publications and source records attributed to H Siegrist.

10 recordsLinked to original sources

PubMed1991

Circumferential fusion of the lumbar and lumbosacral spine.

Seventy-four patients with circumferential fusion of the lumbosacral spine have been assessed after a mean follow up of 49.8 months. For the ventral procedure, an anterior interbody fusion with tricortical iliac bone graft was performed. The additional dorsal fusion was according to various techniques with mainly transpedicular internal fixation. Forty-six patients underwent a one-stage operation while 28 underwent the ventral and dorsal procedure in different sittings. The results favour the technique of a combined anterior/posterior approach for fusion of the lumbosacral spine in patients with instability and deformity of all three columns, such as fractures and spondylolisthesis of more than 50%. Optimal stability with satisfactory reduction of the deformity may be achieved. The one-stage operation proved to be superior, with less complications and a shorter hospital stay.

Adolescent↗

PubMed1991

[The GSB knee joint: reoperation and infections].

The GSB-III knee prosthesis is one of the semi-constrained types and consequently ranks between the non-constrained condylar prostheses and the fully constrained hinges. Its kinematics can be classified as "physiological" in the sagittal plane as far as the relationship between femur and tibia in the various degrees of flexion is concerned, which is a replica of a normal knee joint. The high average range of postoperative mobility as well as the extremely low aseptic loosening rate after 10 years prove the truth of this statement. A simple operative technique requiring a few special instruments allows even the less experienced knee surgeon to be successful and to obtain good results in cases with severe deformity and poor bone quality. The survival curves of the GSB-III prosthesis (n = 638) show a cummulative success rate of over 90% after 10 years. Looking separately at cases complaining of more or less severe pain, we frequently find underlying patellar problems, the main cause for revisional surgery. This problem is not specific for our prosthesis, but must be considered a so far unsolved worldwide problem. Infections are another relatively frequent cause for revisions. Disturbed wound healing, arterial insufficiency and malignant rheumatoid arthritis are the outstanding risk factors. For a reliable comparison of the different knee prostheses we ought to have a globally accepted evaluation system, which unfortunately still does not exist.

Adolescent↗

PubMed1989

[Girdlestone total prosthesis].

Thirteen out of 17 patients with a hip prosthesis according to the Girdlestone procedure were studied at a follow-up time of 26 months to 10 years. Seven patients were found to be satisfied with the total prosthesis, while the others complained about pain, walking disability and an insufficient range of motion. The implantation of a prosthesis using the Girdlestone procedure is technically difficult and should be restricted, as the results are superior to the Girdlestone hip in only a carefully selected group of patients with good abductor muscles and unsatisfactory results after the Girdlestone operation.

Femoral Neck Fractures↗

PubMed1989

[Loosening of hip prostheses in chronic rheumatoid polyarthritis].

The hip with rheumatoid arthritis (RA) is characterized by reduced bone resistance. Protrusion, fatigue fractures and femoral head collapse are the typical consequences. The survival rate of total hip prostheses in hips with RA seems to be higher than for hips with osteoarthritis (OA), possibly due to lower demands. When isolated loosening of the acetabular and femoral component are compared, there is a definite shift towards acetabular loosening in RA compared to OA. This is definitely due to the reduction in the mentioned bone resistance at the acetabular level. In primary joint replacement, well-cemented femoral components provide more reliable clinical results. They will remain the gold standard for long-term performance as well. On the other hand, it is very likely that non-cemented acetabular components, fixed by means of screws in the direction of the resulting force or based on a compression principle, may prove at least as effective as well-cemented acetabuli. For revision of the loose acetabular component, the use of special metal rings fixed with screws and bridging severe bony defects with a bone graft and frequently also bone cement, have proved to be of value. For loose femoral components with a thin and brittle cortical wall, special non-cemented prostheses combined with a bone graft seem to promise a more reliable long-term solution than cemented versions. The follow-up of our revision cases confirms the value of the described methods - at least at the short and medium-term follow-up. More definite conclusions can only be arrived at after long-term follow-ups which have been carried out with different systems and where the results are compared using the same documentation procedure.

Adult↗

PubMed1979

Macromolecular structural transitions in Pf1 filamentous bacterial virus.

The filamentous bacterial virus Pf1 is a simple model for biological filaments. We have studied the structure of the virion and report here that the helix parameters of Pf1 change sharply with temperature at about 8 degrees C. Local interactions between protein subunits change by only a few tenths of an angstrom, but the changes are amplified between one end and the other of the virion to a rotation of 15 turns and a translation of 1,000 A. The limited nature of the phase transition is probably due to the constraints of 'knobs-into-holes' interaction between side chains of adjacent alpha-helical protein subunits. Treatment of the virion with ether causes a rearrangement of protein subunits into sheets, with the alpha-helices normal to the plane of the sheet. This phase transition suggests a model for virion assembly in the bacterial membrane.

Bacteriophages↗

PubMed1978