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Biomedical subjects

G O Hofmann

Publications and source records attributed to G O Hofmann.

At least 55 records · Page 3Linked to original sources
PubMed1994

[Implants and transplants in bone replacement].

Implants and grafts are employed in the fields of orthopaedic surgery to fill osseous defects and to restore destroyed joints. These bone substitute materials may be derived from different biological and technical sources. In this overview-paper the various methods of bone and joint substitution are discussed concerning their advantages and their disadvantages in comparison to the alternative methods. The decision, which way to go, which implant or graft should be employed in each individual case must be based on the specific medical, economical and social situation of every single patient. Finally future aspects of allogeneic bone and joint grafting are discussed, an hopeful experimental approach for a biological form of joint replacement.

Bone Lengthening↗
PubMed1994

Positive donor and negative recipient cytomegalovirus status is a detrimental factor for long-term renal allograft survival.

In 524 allogeneic cadaveric kidney transplants, the impact of cytomegalovirus (CMV) donor/recipient status on the incidence of CMV infection, CMV disease, early and long-term graft, and patient survival have been analyzed with respect to rejection episodes. Most CMV infections (59%) and diseases (17%) were found in CMV-negative recipients of CMV-positive kidneys. The 1-year function rate of CMV-positive kidneys (75%) dropped about 10% below that of CMV-negative organs (85%), and in the case of CMV-negative recipients an additional graft loss of more than 10% happened within the 4th and 5th years (5-year graft survival pos./neg.: 56%). This detrimental effect was exaggerated if it coincided with antibody-treated rejection episodes.

Adult↗
PubMed1994

Early infiltration of renal allografts with 27E10-positive macrophages and graft outcome.

Recently, we have demonstrated that acute cellular rejection is correlated with a massive infiltration of 27E10-positive macrophages. To examine the distribution of macrophage differentiation markers in the infiltrate in the very early post-transplantation period, two biopsies were taken intraoperatively, approximately 1 h following reperfusion, in each of 16 renal transplant recipients. One biopsy was taken for conventional histology and the other biopsy was snap-frozen. The sections were stained using an ABC indirect immunoperoxidase technique. A panel of monoclonal antibodies against three macrophage differentiation markers (27E10, 25F9 and RM3/1) was used to stain the sections. Using the early inflammation macrophage marker 27E10, there was an unexpected strong staining in 3 out of 16 biopsies. This severe infiltration of 27E10-positive macrophages with 10-20 macrophages per high power field (compared to 0-2 in others) was correlated in all cases with a poor outcome of the graft. All seven kidneys with no 27E10-positive infiltration showed a good function 6 weeks post-transplantation. The other macrophage markers, 25F9 and RM3/1, showed a less marked correlation with graft outcome. In conclusion, a massive infiltration of renal allografts with 27E10-positive macrophages 1 h post-transplantation may be a very early predictor of poor graft outcome.

Antigens, Surface↗
PubMed1993

New implant designs for bioresorbable devices in orthopaedic surgery.

From today's point of view it is not possible to transfer the designs of metal implants in orthopaedic surgery to biodegradable polymers. The attempt of a simple mimicry of metal implants for those made of polymers was condemned to fail from the very beginning. In this paper some fundamental limitations of implants made from biodegradable polymers (PGA and PLA) are experimentally demonstrated. Fixing devices adapted to the characteristic properties of polymers and adjusted to the specific therapeutic problems have to be developed. The creation of new implant devices made of biodegradable polymers depends on the influence of manufacturing processes, composite materials, fibre reinforcement, coating, specific erosion processes and the development of new implant designs. The basis for a new implant philosophy is discussed.

Biodegradation, Environmental↗
PubMed1992

Biodegradable implants in orthopaedic surgery--a review on the state-of-the-art.

Until recently, internal fixation of fractured bones and joints has been managed by metal implants. Certain disadvantages of the metal implants are: the properties of the materials are stiffer than those of cortical bone and removal of the implants requires a second operation. About 40 different biodegradable polymers, copolymers and composites have been developed in order to substitute the metal implants for internal fracture fixation. First experimental and clinical results demonstrate the limitations of these new methods. The main problem of the material is the loss of mechanical strength within a time interval not long enough to guarantee bone healing. The development of sterile sinus at the site of implantation is also a problem reported by various groups. Despite some drawbacks, there are indications for the isolated or the adjuvant implantation of biodegradable materials.

Biocompatible Materials↗
PubMed1990

The influence of bacterial contaminations on the biodegradation of PLA implants.

Metal implants employed in orthopaedic surgery have certain disadvantages. Intensive research work is therefore being done in the field of biodegradable implants, the behavior of which in the case of possible contamination or infection at the operation site has not yet been studied. In-vitro experiments on PLA-test bodies were performed to clarify the influence of bacteria on the polymer degradation. The investigated parameters were germ growth, course of the pH-value of the culture media, bending stiffness of the PLA-test bodies and the decrease in their molecular weight. The experiments performed did not demonstrate an accelerated degradation of PLA specimen in vitro incubated in different bacterial contaminated media. Therefore bacterial contamination may possibly not lead to a premature collapse of the PLA used in connection with fracture treatment by biodegradable osteosynthesis implants.

Bacterial Infections↗
PubMed1990

[Tendon rupture in chronic kidney insufficiency--"uremic tendonopathy"? A literature-supported documentation of 3 cases].

This is a report on three cases with spontaneous ruptures of major tendons of the lower extremities. In two cases ruptures occurred in the quadriceps tendon, one of them bilaterally, and in one case in the Achilles' tendon. All patients suffered from chronic renal failure and were treated by long-term hemodialysis. Coincidentally secondary hyperparathyroidism was noticed twice. The pathophysiological relation between chronic renal failure and spontaneous tendon rupture is still unknown. An "uremic tendopathy" is discussed.

Achilles Tendon↗
PubMed1989

The cruciate ligaments in knee replacement.

The cruciate ligaments were resected with their bony insertions during total knee arthroplasty carried out in 12 patients with severe rheumatoid or osteoarthritis. The ligaments were examined histologically and biomechanically, using ten specimens from healthy adults as a control. A significant difference was found in the tensile stiffness and viscoelastic properties of the ligaments between the arthritic and the control group. The ligaments in the rheumatoid knees had a distinctly inferior tensile strength compared with the osteoarthritic knees. Total knee replacement, which also replaces ligament function, should therefore be considered in severely damaged rheumatoid knees.

Arthritis, Rheumatoid↗
PubMed1987

Pathomechanics of the femoropatellar joint following total knee arthroplasty.

Persistent discomfort in the femoropatellar joint is still one of the most disappointing aspects following total knee arthroplasty (TKA). Especially, TKA without patellofemoral replacement has a significant incidence of patellofemoral problems with a frequency between 5% and 45%. Pathomechanical factors in the development of retropatellar problems are loss of patellar thickness and retropatellar erosions. In 157 TKAs using Gschwend, Scheier, Bähler (GSB) joints without patellar resurfacing, pathomechanically postoperative vertical patellar malposition appeared to be the main cause of dysfunction. In many cases, the implantation technique leads to an artificial form of patella alta. This altered knee anatomy results in pathologic biomechanics, thus leading to reduced function. The combination of altered anatomy and reduced function leads to extensive patellar destruction and ultimately to intractable retropatellar pain.

Biomechanical Phenomena↗
PubMed1985

[Scintigraphic research on patellar changes after endoprosthetic replacement of the knee joint].

A clinical and x-ray review of 118 GSB-Knee-Protheses without resurfacing the patella--mean time of follow-up 4 years--was performed. In 50 knees of these an additional quantifying bone-scan with 99mTc-MDP ("ROI-method") indicated new aspects of the pathomechanics of the patella after knee replacement. Comparing 42 healthy knee joints and 82 knees with osteoarthrosis principles for early diagnosis of patellar changes could be set up. According to these findings the quantifying scans show the development of dystrophic patellar changes after knee replacement.

Aged↗