PubMed Health⌕ Search

Biomedical subjects

M Amling

Publications and source records attributed to M Amling.

66 records · Page 4Linked to original sources
PubMed1995

Structural heterogeneity within the axis: the main cause in the etiology of dens fractures. A histomorphometric analysis of 37 normal and osteoporotic autopsy cases.

Fractures of the odontoid process are potentially serious injuries; Type II and III fractures, as described by Anderson and D'Alonzo, are seen in the emergency room especially in young adolescents and individuals over 60 years of age. The etiology of these fractures is still controversial. Malunion and nonunion in both types of fractures are presumed to be due to insufficient external or internal fixation, but this theory has not been fully explained. To examine these issues, the authors expanded their prior studies of the anatomy of the axis. For histomorphometric analysis of cancellous and cortical bone, the axis was removed in 37 autopsies (26 normal and 11 osteoporotic cases) and sectioned in the sagittal plane to a thickness of 1 mm using a surface-stained block-grinding technique. The base of the dens is the region of least resistance for fractures because of its reduced trabecular bone volume, a poorer trabecular interconnection, and a cortical thickness one-third that of the axis. In all cases, trabeculae were disconnected from the trabecular lattice, and in 30%, microcallus formations were demonstrated in the base of the dens. A special filigree type of trabeculae in the base of the dens is often seen in patients with osteoporosis; microarchitectural differences of cancellous bone between the base of the dens and the other regions of the axis are also markedly increased. The authors infer from the data that the bone structure of the axis is responsible for the location, distribution, and frequency of fractures of the odontoid process in normal healthy bone and this frequency is greatly increased in individuals with osteoporosis. The deficiency of bone mass within the base also suggests a new explanation for the occurrence of nonunions, even after treatment of fractures of the base of the dens.

Adolescent↗
PubMed1994

[Morphology of the surgically treated dens fracture].

The peculiarities within the microarchitecture of the base of the dens have to be assumed as one of the underlying causes for type II and III fractures of the dens according to Anderson and D'Alonzo. As can be demonstrated in a section of the dens of a patient after primary osteosynthesis using two small fragment AO cancellous screws this leads to multiple local trabecular fractures and destruction of the cancellous microarchitecture. Further more compression by the screws results in a higher density of the bone mass in the region of fracture. Apart from the fact that two AO screws guarantee rotational stability, this type of osteosynthesis seems to favour intracorporal bony fusion by increased trabecular bone volume and induction of microcallus within the base of the dens. In a patient with a small intracortical transverse diameter of the dens the available space is completely filled by the screws threads. Partial penetration of the threads through the cortical bone seems to be of no clinical and biomechanical relevance and can be avoided using screws of smaller diameter.

Aged↗
PubMed1994

[Presentation of the 3-dimensional spongiosa structure of the spine in renal osteopathy after chronic hemodialysis].

Characteristic skeletal changes occur in patients with chronic renal insufficiency. The aim of this study was comprehensively to record bone volume changes in the spine, from C2 to L5, after a long history of hemodialysis. The spinal columns of nine autopsy cases who had undergone 4 to 15 years of dialysis were thoroughly examined. The age-related control group consisted of 26 autopsy cases with intact skeletons. A iliac crest biopsy facilitated a direct comparison of the diagnostic biopsy location and the spinal column. A newly developed preparation technique enables a combined two- and three-dimensional analysis to be made, so that in addition to the histologic image, the directly underlying three-dimensional structure can be analyzed. The spine deformity index (SDI), the bone volume (BV/TV), and the trabecular interconnection (TBPf) was quantitatively evaluated. The SDI shows vertebral fractures in renal osteodystrophy (ROD) types I and II in spite of a trabecular bone volume within normal limits. The trabecular bone volume shows a distribution throughout the spinal column familiar from the skeletally intact control group. The plateau-like curve line, decreasing from the cervical spine to the lumbar spine is, however, 5% lower in ROD. BV/TV values of 51.2% and 74.1% in the 2nd lumbar vertebra are clearly lower than in the corresponding iliac crest biopsy. Cases with a longer history of hemodialysis show higher BV/TV values irrespective of age and sex. Normal BV/TV does not mean physiological linking. Three-dimensional analysis in ROD shows, in comparison to the controls, a much stronger restructuring of the architecture than can be assumed from the two-dimensional histological sections.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Micro-callus formation of spongiosa. An up to now underestimated repair mechanism of the skeletal system].

Microcallus formations are demonstrable in nearly all cancellous bones by means of suitable preparation techniques. Histologically, these structures are immature fibrous bone formed in local overloaded parts of the trabeculae. Using a preparation technique that allows combined two- and three-dimensional analysis, 26 normal human spines and 11 osteoporotic spines were investigated for microcallus. Microcallus formations occur frequently in people over 45 years of age. They are mainly localized in the lower thoracic and lumbar spine and occur significantly more frequent in females than in males. The number of microcallus formations depends more on the microarchitecture of the cancellous bone than on individual trabecular parameters. In about 33% of cases microfractures are demonstrable in the centre of the microcallus formation. In non-invasive studies the bone mass could be misinterpreted due to microcallus. Although it indicates instability of the bone structure, microcallus formation is not a purely negative mechanism. It stabilizes and regenerates the bone tissue. Furthermore, complete new trabeculae can be formed due to bridges of microcallus between residual trabeculae. Osteoporosis is not the result of an inability to form microcallus.

Adolescent↗
PubMed1994

[Apoptosis: bcl-2 as a key protein for programmed cell death].

The realization that malignant tumors may grow not only due to proliferation but also because cells don't die when they should provides absolute new directions in basic and clinical tumor research. Thus, apoptosis, the programmed cell death is very hot now in the scientific community. In the center of interest are the regulation mechanisms of apoptosis and its significance in different tumor entities. Recently, numerous studies on apoptosis during embryogenesis, different stages of tissue development and in epithelial and hormone dependent tumors have been published. The data suggested an important role of bcl-2 in regulation of apoptosis. In this view the demonstration of bcl-2 oncogene expression in osteosarcoma, a mesenchymal tumor, is of potential great interest.

Animals↗
PubMed1994

[Osteosarcoma--apoptosis and proliferation. Study of bcl-2 expression].

The relationship between the growth of tumors and the expression of the protooncogene Bcl-2 could be shown in epithelial tumors. A bcl-2 expression leads to a prolonged cell survival due to an inhibition of apoptosis. The potential meaning of bcl-2 expression in mesenchymal tumors remains still unknown. The fact, that the heterogenous group of osteosarcoma is not sufficiently characterized at present, suggested to investigate the bcl-2 expression in osteosarcoma. Thus, immunohistochemistry was used to analyze 47 specimens of different osteosarcomas of 36 patients. Sixteen cases (46%) showed a strong expression of bcl-2 and 13 cases (35%) were moderately positive for bcl-2. Seven cases (19%) were negative for bcl-2. The heterogenous, negative up to strong expression of bcl-2 yield clues, that the Bcl-2 controlled regulation of programmed cell death could be an important factor of cellular kinetics. Additionally the cellular proliferation rate was determined with the monoclonal antibody MIB 1, directed against the Ki-67 epitope. The data of bcl-2 expression and cellular proliferation rate lead to a classification correlating with the histological classification. To verify the importance of apoptosis in the genesis of mesenchymal tumors and whether Bcl-2 may play an important role as a predictive factor for the prognosis of osteosarcoma, further investigations will be needed.

Adolescent↗
PubMed1994

Polyostotic heterogeneity of the spine in osteoporosis. Quantitative analysis and three-dimensional morphology.

It was the aim of this study to record quantitatively and qualitatively the distribution of the three-dimensional microarchitecture throughout the human spine in osteoporosis. Bone biopsies of the iliac crest and the complete spine of 26 autopsy cases without skeletal disease and 11 female patients with proven osteoporosis were removed. Grindings of all vertebrae by a technique which we developed allowed two- and three-dimensional measurements simultaneously. The analysis included an evaluation of trabecular bone volume, trabecular interconnection, and trabecular thickness, as well as a qualitative investigation of the structure of cancellous bone. The bone loss in osteoporosis is a loss of structure. The relative loss of the trabecular microarchitecture is greater in the iliac crest than in the lumbar spine. It is a gradual change from normal bone to osteoporosis. Transformation from plates to rods and the loss of whole trabeculae are caused by perforations. The polyostotic heterogeneity in osteoporosis is remarkable. Adjacent vertebrae may show differences of up to 100% in bone structure and bone volume. This explains the difficulties in early diagnosis of osteoporosis. Due to the polyostotic heterogeneity it is impossible to define a threshold mineral content for osteoporotic fractures.

Aged↗
PubMed1994

Three-dimensional analysis of the spine in autopsy cases with renal osteodystrophy.

The spinal column was removed from nine autopsy cases with chronic maintenance dialysis and sectioned in the sagittal plane to a thickness of 1 millimeter using a surface-stained block grinding technique. A combination of two- and three-dimensional analysis included an evaluation of the spine deformity index (SDI), the bone volume (BV/TV), the trabecular interconnection (TBPf), the trabecular thickness (Tb.Th), the trabecular number (Tb.N) as well as a qualitative investigation of the structure of cancellous bone. The control group consisted of 26 autopsy cases with intact skeletons. An iliac crest biopsy made a direct comparison of the diagnostic biopsy location and the spinal column possible. The SDI showed vertebral fractures in renal osteodystrophy (ROD) of types I and II, in spite of a trabecular bone volume within normal limits. The trabecular bone volume showed mean values and a distribution throughout the spinal column familiar in the skeletally-intact control group. Those cases with a longer history of hemodialysis showed higher BV/TV values regardless of age and sex. A trabecular volume within normal limits did not mean physiological trabecular interconnection. Perforations were commonly observed with ROD. Classical, hidden and tunnelling perforations were distinguished. Microcallus formations were frequently seen in the periphery of vertebrae at rod nodes, rods and plate intersections. Three-dimensional analysis in ROD shows a greater alteration in architecture than can be assumed from the two-dimensional histological sections.

Autopsy↗
PubMed1994

The microarchitecture of the axis as the predisposing factor for fracture of the base of the odontoid process. A histomorphometric analysis of twenty-two autopsy specimens.

The axis from twenty-two cadavera was removed at autopsy and was sectioned in the sagittal plane to a thickness of one millimeter with use of a surface-stained block-grinding technique. Combined two and three-dimensional analysis included an evaluation of the volume of the trabecular bone, the trabecular interconnection, and the cortical thickness as well as qualitative investigation of the structure of the cancellous bone. The body of the axis, the base of the odontoid process, and the odontoid process were analyzed separately. The base of the odontoid process is a region of least resistance for fractures because of its unique microarchitecture. The mean volume of trabecular bone of the base of the odontoid process is 55 per cent less than that of the axis and the odontoid process. The base also has a markedly poorer trabecular interconnection and a cortical thickness that is one-third that of the odontoid process. In all of the specimens, trabeculae that were disconnected from the trabecular lattice (trabeculae with free ends) were demonstrated in the base of the odontoid process. The formation of microcallus in six (27 per cent) of the specimens supports the hypothesis that microfractures occur as a result of stress peaks, mechanical fatigue, and the relative insufficiency of bone in the static condition. Therefore, the base of the odontoid process can be considered as a site of predilection for fractures.

Adolescent↗
PubMed1994

[Structure of the axis--key to the etiology of the dens fracture].

Fractures of the dens are seen especially in young adolescents but also in individuals after the sixth decade of life. The etiology of these fractures and the occurrence of non-union after initial treatment is still discussed controversially. To address these issues, the axis was removed from thirty-seven autopsy cases for histomorphometric analysis. The base of the dens is a region of least resistance for fractures due to its reduced trabecular bone volume, a poorer trabecular interconnection and a cortical thickness one third that of the axis. In all of the cases, trabeculae disconnected from the trabecular lattice, and in 30% microcallus formations were demonstrated in the base of the dens. In osteoporotics the microarchitectural differences of cancellous bone between the base of the dens and the other regions of the axis are increased markedly. The obtained data suggest that the bone structure of the axis is responsible for the location, the distribution and the frequency of fractures of the odontoid process. The deficiency of bone mass within the base also offers a new explantation for the occurrence of non-unions even after treatment of fractures of the base of the dens.

Adolescent↗