Biomedical subjects

D Stock

Publications and source records attributed to D Stock.

41 records · Page 3Linked to original sources

PubMedDate not supplied

[Further development of the graded-shaft fixation principle].

A new concept is presented for the design of total hip prostheses. After the discussion of the commonly used gliding materials the use of ceramic-ceramic gliding surfaces is justified in respect to its minimal wear rate. The most important biomechanical recommendations concerning the design of femoral stems and ceramic acetabular cups are summarized. Own clinical results with a ceramic-ceramic cementless hip endoprostheses are presented. A new concept of femoral stem fixation is introduced in consequence of those biomechanical recommendations and of own clinical experiences. 4 photographs are showing the new stem design.

Biomechanical Phenomena↗

PubMedDate not supplied

[Aggressive fibromatoses in orthopedics].

Aggressive fibromatoses which may develop either in soft tissue or in the bone present considerable problems for the pathologist trying to establish a diagnosis as well as for the radiologist and surgeon. In radiographs, a destruction of the soft and osseous tissue is seen which suggests a malignant tumor. Histologically a monomorphic connective tissue prevails in the biopsy showing no essential signs of malignancy. Under pathoanatomical aspects often a benign proliferation of the connective tissue is assumed. Surgically the tumor may either be removed in a too radical and mutilating way, or the excision may remain incomplete. Two cases of desmoplastic bone fibroma (aggressive fibromatosis in the ulna and in the sacrum) are described in which the complete tumor removal led to healing, whereas the incomplete excision of the tumor resulted in recurrences. Aggressive fibromatosis represents a semimalignant tumor which has a locally destructive and invasive growth tendency but does not metastasize. The various fibromatoses are defined with regard to their biological growth tendency and the therapeutic consequences are discussed.

Adolescent↗

PubMedDate not supplied

[Postoperative pain in cement-free femur shaft prosthesis].

With practically all hip endoprosthesis systems the femoral components of which are implanted cement-free irritations in the femoral region persisting for up to two years p.o. have been reported significantly more frequently than with cemented shafts. The discussion of this observation is based on the fact that stems inserted cement-free are mostly press-fitted into the surrounding bone, thus, creating a completely different stress and strain field as compared to cemented shafts. The usually spontaneous disappearance of these initial irritations is attributed to remodelling reactions which, controlled by the load distribution in the surrounding bony tissue which, in turn, is mainly controlled by the shape of the prosthesis, results in the formation of well load bearing bony structures along steps and other surface undulations along the proximal part of the prosthesis.

Body Weight↗

PubMedDate not supplied

[Experimental results of stepped titanium shafts for hip endoprostheses].

Among the materials which can be used for hip prostheses to be implanted without bone cement, ceramics and titanium possess the best overall properties for insuring long-term stability in the light of present knowledge. However, considered separately, the two materials are most suitable for different special requirements. Results of long-term animal experiments conducted by different working groups on functionally stressed hip and tooth-root implants made of bio-inert Al2O3 ceramic and titanium have furnished knowledge of the possibilities and limitations of the adaptation reaction of the bone tissue. The present authors investigated whether, by combining Al2O3 ceramic and titanium, a cement-free total hip replacement can be adapted to specific local stresses, taking biomechanical rules and anatomical factors into account. In recent experimental series it proved possible to limit the problems which had occurred in previous series, reported elsewhere. Positive results in dogs led to a human implant which has so far been used 15 times, with Al2O3 (FRIALIT) acetabula and heads, which have been implanted successfully for a number of years, in combination with the new stepped titanium shaft. In addition to a short review of follow-up findings thus far, the results of the experimental investigations are presented.

Animals↗

PubMedDate not supplied

Structural investigation of proteasome inhibition.

The novel proteolytic mechanism of the 20S proteasome from T. acidophilum has been investigated by X-ray crystallography using small-molecule inhibitors and substrate analogues. The 20S proteasome degrades unfolded substrates into small peptides of a defined length. Calpain inhibitor II, chymostatin and lactacystin all bind in the previously identified active site pocket near Thr1 of all fourteen beta-subunits. The chromogenic substrate analogue Suc-LLVY-AMC binds in the same pocket of the proteolytically inactive T1A mutant of the beta-subunit, but with a significantly altered geometry. The heavy-atom cluster Ta6Br12(2+) used in X-ray structure determination occupies seven sites in the inner compartment of the proteasome and exhibits inhibition of the chymotrypsin-like activity. Other effectors of proteasome activity showed no significant difference in electron density.

Acetylcysteine↗