Search PubMed⌕ Search

Biomedical subjects

D Kohn

Publications and source records attributed to D Kohn.

At least 19 recordsLinked to original sources
PubMed1995

[Critical age as the main parameter of deterioration of health in the elderly].

The concept of critical age (CA) relates to accelerated development of illness in the elderly and defines the decade in which there is the greatest increase in a specific pathological condition. Clinically, increased rates for pathological medical, biological, psychological and social conditions occur in defined populations. 78 parameters with linear increase in rate were excluded. 693 parameters were computed and classified according to both decade of life and to physiological and multisystem problems (such as diabetes). The most dangerous age is 70-79 years, when calamities of various degrees of severity "bomb" a subject approximately twice a month. CA was similar for some systems (immune, endocrine, and cardiovascular), and for diabetes and hypercholesterolemia. Among 351 CA distributions relating to 27 systemic and multisystemic problems, there were 103 statistically different CAs. We conclude that the rate of deterioration in health is largely system-oriented. Following the most dangerous decade, rates of increase in CA slow or CA even decreases, so that health is relatively stabilized. Such stabilization is related in part to improvement in risk factors. Improved health at age 80 seems to be related to selection by the death of the sick, but the concept of true functional improvement at this age is being seriously discussed. Physical, psychological and social bilateral adaptation of both old people and of western society, play important roles, because better medical and social protection improves living conditions. Our data confirm the identification of 2 subpopulations of the elderly, the young-old and the old-old. Study of frailty according to both age and physiological systems gives additional useful information.

Age Factors↗
PubMed1995

Arterial blood supply of the infrapatellar fat pad. Anatomy and clinical consequences.

The arterial blood supply to the infrapatellar fat pad (Hoffa's fat pad) was investigated in 12 knee joints of human cadavers. The infrapatellar fat pad is supplied by an anastomotic network which displays some striking topographic features. Its vascular blood supply protects it against necrosis, when either reconstructive operations are carried out or extensive surgical exposures of the knee are done. The blood supply to the center of the fat pad is limited. This is of practical importance for the choice of arthroscopic portals. In addition, arthroscopically verified sources of bleeding are described in 57 patients with hemarthrosis without clinically detectable instability. Rupture of the infrapatellar synovial fold can be a cause of posttraumatic hemarthrosis in rare cases. Arteries irregularly found within the fold contribute to the blood supply of the anterior aspect of the synovial membrane covering the cruciate ligaments.

Adipose Tissue↗
PubMed1995

Meniscus insertion anatomy as a basis for meniscus replacement: a morphological cadaveric study.

A morphological cadaveric study was carried out to gain exact data concerning location, shape, and size of the meniscal insertions to bone. Ninety-two knee joints were dissected (46 donors; age 18 to 58 years). Peripheral length of the menisci, including their insertion ligaments, was measured. The peripheral length was 111 +/- 14 mm for the medial and 111 +/- 10 for the lateral meniscus. The tibial insertion ligaments for the medial meniscus were fixed in areas that could be defined by bony landmarks. The posterior insertion area measured 80 +/- 10 mm2, the anterior insertion area measured 139 +/- 43 mm2. Bony tibial insertions of the lateral meniscus were less well defined. The posterior meniscofemoral ligament (Wrisberg) was found in 76% of the knees; the anterior meniscofemoral ligament (Humphry) was found in 50% of the specimens. The meniscofemoral ligaments in the right knee and the left knee of the same individual were frequently different. The anterior transverse ligament was found in 64% of the specimens. We concluded that an anatomical attachment of a medial meniscus substitute should be possible but to restore the lateral meniscus anatomically would be far more complicated.

Adult↗
PubMed1995

[Endoprosthesis and bone reaction].

Prosthetic implants cause a reaction on the part of the surrounding bone. Bone reaction can be interpreted as a dynamic response of the internal bone architecture to stress and strain. On the other hand, instability at the bone-implant interface or biological reactions to wear particles may lead to bone resorption. Standard X-ray examination has remained the most important tool for evaluation of the bone-implant relationship. Knowledge of the radiological features of bone remodelling and bone reaction is therefore a prerequisite for the orthopaedic surgeon. Based on eight case reports after prosthetic replacement of the hip, important radiological signs of bone reaction are presented. If possible a biomechanical or biological explanation is attempted. The information drawn from these cases, as well as from the current literature, suggests that after prosthetic joint replacement routine X-ray follow-up is required, even in asymptomatic patients, and that progressive osteolysis requires early operative revision, even if there are no acute clinical problems.

Aged↗
PubMed1994

Solitary skeletal lesions as primary manifestations of non-Hodgkin's lymphoma. Report of two cases and review of the literature.

Two patients with solitary skeletal lesions of the lower extremity were eventually diagnosed as having high-grade malignant B-cell non-Hodgkin's lymphoma. In both cases staging revealed no other nodal or extranodal involvement. One patient had been symptomatic for more than 2 years, presenting originally as a case of chronic synovitis. The second patient presented with slight exertional pain in his left knee of relatively recent history. In his case the initial plain X-ray showed little evidence of bony destruction, while magnetic resonance imaging revealed an extensive lesion in the left tibial plateau. Orthopedic surgeons should be aware of the differential diagnosis of primary lymphoma of bone. Early use of magnetic resonance imaging, in addition to plain X-ray and scintigraphic imaging, can be helpful in leading to an early biopsy and consequently early treatment. Magnetic resonance imaging should be regarded as the method of choice for follow-up examinations of lymphoma lesions.

Adolescent↗
PubMed1994

Erythrocytes from young but not elderly donors can bind and degrade immune complex- and antibody-bound C3 in vitro.

In situ aged erythrocytes (senescent erythrocytes from young donors and both young and old erythrocytes from elderly donors) demonstrate high levels of membrane-bound C3c and C3d and elevated susceptibility to in vitro phagocytosis. In this study we demonstrate that in situ aged erythrocytes are defective in their ability to degrade C3 fragments and clear them from the erythrocyte membrane. Erythrocytes from young donors bind complement-bearing immune complexes via CR1 and become susceptible to complement-mediated erythrophagocytosis ('innocent bystander' sequestration). Erythrocytes from elderly donors are defective in their ability to bind such immune complexes, as attested by the lack of an increment in membrane-associated C3 fragments as detected by flow cytometry and lack of an increment in in vitro sequestration. Factor I (serum)-dependent cleavage of C3 fragments and release of immune complexes from the erythrocytes of young donors lead to a drop in erythrocyte-associated C3 fragments and the disappearance of the 'innocent bystander' phenomenon. Inhibition of Factor I, and thus inhibition of C3b degradation and immune complex release for the erythrocyte membrane, enhances the levels of 'innocent bystander' sequestration of erythrocytes from young donors. Erythrocytes from elderly donors are defective in the dynamic process of CR1 binding of complement-bearing immune complexes and Factor I-associated release of membrane-associated C3 fragments. A defect in the ability of all in situ aged erythrocytes to clear their membranes of C3 fragments is also demonstrated for complement bound to the erythrocyte via IgM isoagglutinins. While erythrocytes from both young and elderly donors allow for the IgM-mediated binding of complement to the erythrocyte, only young erythrocytes from young donors demonstrate degradative activity with the release of membrane-associated C3c. Erythrocytes from elderly donors demonstrate lower levels of detectable CR1 (CD35), decay accelerating factor (DAF) (CD55) and Protectin (CD59) than do erythrocytes from young donors. Time course studies determine that the defect in handling of immune complexes observed for in situ aged erythrocytes is not due to differences in the kinetics of loading or releasing of immune complexes. These findings on the refractiveness of erythrocytes of elderly donors to uptake of immune complexes and the degradation of C3 fragments may be of importance not only in the understanding of erythrocyte sequestration, but also in the physiology of immune clearance in the elderly.

Adolescent↗
PubMed1994

[Assessment of vital activity in geriatric patients].

17 parameters of vital activity (VA) were scanned in 35 female and 12 male dependent geriatric patients (mean age 81). These included mental testing, Barthel score, lung function, urinanalysis, creatinine clearance, Hb, albumin, globulin and electrolytes, skin-folds, locomotion, presence of IHD, hemodynamic state, continence, infections, WBC and lymphocyte count, pressure sores and dysphagia, 4 main templates of VA deterioration identified were: IHD, hemisyndrome (due to CVA), vegetative state (post-CVA) and senile dementia (SDAT). The IHD template was characterized by marked variations in VA, ending in death due to cardiac complications (pulmonary edema, ischemia, etc.). In the 3 other templates VA gradually deteriorated. Gradual declining VA allowed assessment of individual mortality prognosis. Assessment was by approximation of the computed exponent of the extrapolated VA curves; the longer the observation, the fewer the mistakes in assessment. Epidemiologic prognosis data of 48 dependent patients is described; mean age was about 81 years. Hospitalization mean was 853.5 +/- 601 days and for patients with dementia, 1158.6 +/- 622.7 days.

Aged↗
PubMed1994

[Transplantation of allogeneic menisci].

The increase in severe ligament injuries of the knee has led to consideration of the need for meniscal transplantation in reconstructive operations for chronic rotational instability. Transplantation of the medial meniscus was carried out in 30 sheep, which were divided up into 2 groups, each containing 15 sheep. In the first group lyophilized, y-sterilized allogeneic menisci were transplanted and these underwent complete remodelling in 48 weeks. In the other group, deep-frozen allogeneic menisci were used and these remained fully functional without remodelling. Twenty-three transplantations of the medial meniscus combined with replacement of the anterior cruciate ligament were performed from May 1984 to December 1986. Clinical follow-ups were coupled with arthroscopic follow-ups on an average of 10 months post-operatively in 19 sheep. In 17 cases a lyophilized meniscus was transplanted and in 6 cases a deep-frozen allogenous meniscus was used. There were no operation-specific complications in either group. Both the lyophilized meniscus transplants and the deep-frozen ones underwent a reduction in size during the observation period. Good-to-excellent results were generally obtained with the deep-frozen transplants; however, there is the risk of transmitting disease. The results seen in the lyophilized transplants were less satisfactory due to a reduction in size, sometimes down to the regeneration size. Taking the infrapatellar fatty pad for meniscal replacement (as suggested by Lexer), we saw only weak meniscus-like tissue after the first year postoperatively. The meniscus tendon by means of an autologous tendon for meniscus replacement may be an alternative procedure. Therefore, allogeneic meniscus transplantation for reconstruction of the knee joint cannot be recommended at present as a standard procedure.

Adult↗
PubMed1994

[Meniscus replacement].

Partial meniscectomy and meniscus reconstruction are the procedures of choice for the majority of symptomatic meniscus lesions. If total meniscectomy cannot be avoided or was already performed, there is a risk of osteoarthritis, especially in the unstable knee. Different approaches of meniscus replacement are under experimental and clinical investigation at present. Replacement by a tendon autograft, by a meniscus allograft, by a prosthesis or by a collagenous scaffold are discussed. This article is an up-date on the current situation today.

Animals↗
PubMed1994

[Meniscus insertion].

In meniscus replacement procedures anatomically correct fixation of the graft is one of the prerequisites for a successful outcome. An anatomical cadaver study was carried out to identify the insertion areas in the femur and tibia as well as the peripheral meniscus length. Ninety-two fresh knees from 46 human donors were included. The tibial insertions of the medial meniscus could be defined by bony landmarks. The peripheral length was 111 +/- 11 mm for the medial and 110 +/- 13 mm for the lateral meniscus. Wrisberg's ligament was present in 76% of all knee specimens and Humphry's ligament could be found in 50%. The correlation between the right and left knee in the same individual was poor concerning the presence of the meniscofemoral ligaments and the size of the tibial meniscal insertions to bone.

Adolescent↗
PubMed1993

Langerhans' cells of elderly patients with decubital ulcers.

An ultrastructural and morphometric study compared Langerhans' cells in sacral epidermis, 8-10 cm from the lesion of patients (mean age 70) with decubital ulcers, with those in the patients' own normal epidermis from the upper leg and with those in the epidermis from the upper leg of normal age-matched volunteers. The Langerhans' cell section area was significantly lower in patients' control leg epidermis (25.86 +/- 2.29 microns2) than in that from normal controls (35.74 +/- 3.76 microns2) or that from patients' sacral epidermis near the lesion (41.26 +/- 3.45). The number of Langerhans' cell granules was higher in control leg epidermis of patients (10.22 +/- 1.26) and was significantly higher in lesioned sacral epidermis (12.94 +/- 1.90) than in normal controls (6.97 +/- 1.47). In Langerhans' cells in patients' epidermis, formative stages of Langerhans' cell granules were observed. The findings may indicate that Langerhans' cells in patients' epidermis are in an active state.

Aged↗
PubMed1993

T lymphocyte ontogeny in adenosine deaminase-deficient severe combined immune deficiency after treatment with polyethylene glycol-modified adenosine deaminase.

Adenosine deaminase (ADA) deficiency causes severe combined immune deficiency (SCID) by interfering with the metabolism of deoxyadenosine, which is toxic to T lymphocytes at all stages of differentiation. Enzyme replacement with polyethylene glycol-modified ADA (PEG-ADA) has been previously shown to correct deoxyadenosine metabolism and improve mitogen-induced T lymphocyte proliferation. We studied the biochemical and immunologic effects of PEG-ADA in two infants with ADA-deficient SCID. While in a catabolic state, higher doses of PEG-ADA than previously described were required to normalize deoxyadenosine metabolism. After biochemical improvement, the patients recovered immune function in a pattern similar to that observed in normal thymic ontogeny and in patients with immunological reconstitution after bone marrow transplantation. Immune reconstitution was marked by the sequential appearance in the peripheral blood of phenotypic T lymphocytes corresponding to successive stages of thymic differentiation. Functional reconstitution was marked by the successive appearance of mitogen responses dependent on exogenous in vitro IL-2, mitogen responses not requiring exogenous IL-2, antigen-specific responses dependent on exogenous IL-2, and finally, antigen-specific responses not requiring exogenous IL-2. Natural killer function was tested in one patient and normalized with PEG-ADA therapy. Optimal PEG-ADA therapy appears to normalize thymic differentiation in ADA-deficient SCID, resulting in normal antigen-specific immune function.

Adenosine Deaminase↗
PubMed1993

[Revision surgery after failed anterior cruciate ligament repair].

Not every reconstruction of the anterior cruciate ligament is successful. Possible reasons for failure are renewed severe trauma, inadequate fixation of the transplant, an isometric mistake, weak transplant material, an anterior cruciate ligament reconstruction performed in isolation in a complex unstable knee, or prosthetic ligaments. Revision surgery is indicated when patients complain about the recurrence of knee instability. Preoperative diagnostic procedures must include X-rays with the knee in defined positions in order to determine drill hole courses and visualize any signs of arthrosis and the patellar position. Revision surgery is hampered by disadvantageously placed drill holes, exhaustion of the supply of transplant material, secondary instabilities, gonarthrosis or a possible arthrofibrosis. During rehabilitation a variable knee position is imperative, because of the different procedures that might need to be implemented.

Anterior Cruciate Ligament↗
PubMed1992

Lack of changes in histomorphometric, bone mass, and biochemical parameters in ovariohysterectomized dogs.

A predictable animal model with skeletal remodeling characteristics similar to those of humans is needed to facilitate the understanding of the mechanism of postmenopausal osteoporosis. We have utilized the ovariohysterectomized (Ovh) dog to examine cellular and biochemical responses to estrogen depletion and PTH stimulation. Histomorphometric measurements of bone biopsies taken prior to (first biopsy) and five months after the operation (second biopsy) showed no significant differences in static and dynamic parameters. Bone mineral density of the excised vertebrae displayed the same values between the two groups six months after surgery. Between the second biopsy and sacrifice, two infusion studies were performed. A two-hour infusion of EDTA followed by a two-hour recovery period elicited a rapid response in PTH production, highly correlated to the changes in ionized calcium, but no significant difference in response was observed between Sham and Ovh groups. A short-term (24-h) infusion of 1-34 hPTH increased circulating ionized calcium and 1,25-(OH)2-D levels to a similar extent in both groups. The levels of alkaline phosphatase were constant and both groups showed a small but nonsignificant increase in osteocalcin. The lack of sizable responses in histomorphometric, bone mass, and biochemical parameters may limit the utility of dogs for the study of cancellous bone loss in ovarian-dysfunction osteoporosis.

Animals↗
PubMed1992

[The value of dynamic examination methods in instability of the shoulder joint].

We prospectively examined 25 patients with shoulder instability by clinical examination and by fluoroscopic and sonographic imaging. 14 patients were classified as recurrent, posttraumatic instabilities, 12 of these anterior and two posterior. Clinical examination revealed the direction of instability in 5 patients, fluoroscopy in 5 and sonography in 3 patients. 11 patients had non-traumatic recurrent instabilities. Of these, clinical examination and fluoroscopy demonstrated identical directions of laxity in 8. Sonography concurred with the other techniques in only three cases. We recommend manual instability testing followed by fluoroscopy for evaluation and documentation of patients with non-traumatic, recurrent shoulder instability. Posttraumatic instabilities should be diagnosed with other, static procedures.

Adolescent↗