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At least 1,459 records · Page 81Linked to original sources
PubMed1993

Increased varus-valgus tilting of screw-fixated knee prostheses. Stereoradiographic study of uncemented versus cemented tibial components.

Twenty-six women and three men (34 knees) with osteoarthrosis were operated with the Miller-Galante I (Zimmer, Warsaw, IN) knee prosthesis. The patients were randomized to either cemented or uncemented fixation of the tibial component. All patients received a TiVaAl alloy tibial plate with four pegs and titanium fiber-mesh undersurface. In the uncemented knees four screws were added. The fixation of the tibial component was determined by roentgen stereophotogrammetric analysis during the first 2 postoperative years. Rotations of the entire tibial component were recorded, as well as proximal or distal translation of various parts of the prosthetic edge corresponding to subsidence and lift-off. The uncemented components displayed almost all rotation and translation during the first 6 weeks, whereas the cemented ones displayed a more gradually increasing migration during the 2 years. Tibial component rotation about the sagittal axis was significantly increased in the uncemented knees throughout the investigation period. This corresponded to increased subsidence medially or laterally in the uncemented knees, whereas lift-off was equal in the two groups. Thin (8.5 mm) uncemented tibial components displayed more subsidence than the thicker ones at the medial or lateral edge 3 months after surgery.

Aged↗
PubMed1993

Neuroretinal rim area in early glaucoma.

Neuroretinal rim area (NRA) is the only clinical measurement that reflects the real amount of nerve fibers in optic disc. We measured the photographs of the optic disc in 132 eyes of 132 subjects in 6 groups: normal subjects with small cups, normal subjects with large cups, suspected glaucoma with small cups and those with large cups, primary open angle glaucoma (POAG), low tension glaucoma (LTG). The mean NRAs of POAG, LTG and suspected glaucoma with large cups were less than those of normal subjects with large cups. In normal subjects, a high correlation between cup area and disc area was found, while NRA correlated weakly with disc area. Both semiquantitative scores of diffuse and localized retinal nerve fiber layer defects were correlated significantly with NRA. We suggest that measurement of NRA and examination of retinal nerve fiber layer defect could improve the detection of acquired changes of optic disc in early glaucoma.

Adult↗
PubMed1993

Micromotion of a noncemented tibial component with screw fixation. An in vivo roentgen stereophotogrammetric study of the Miller-Galante prosthesis.

Micromotion of the tibial component was studied in ten cases of successful arthroplasty for gonarthrosis using the Miller-Galante total knee prosthesis with roentgen stereophotogrammetric analysis (RSA). In six of seven cases, there was a mean of 0.6-mm migration during the first year. Most of this migration occurred as tilt and rotation. Subsidence was seldom found. Inducible displacement was observed in seven cases after one year; in six, deflections were found. In five cases, the inducible displacement was small, approximately 0.3 mm, whereas the sixth case showed inducible displacement of 1.7 mm. The micromotion found in this study was smaller than has previously been reported for other noncemented prostheses. In some of these cases, the RSA data may be compatible with mechanical coupling of the prosthesis to the bone by bony ingrowth.

Aged↗
PubMed1993

Early migration of acetabular components revised with cement. A roentgen stereophotogrammetric study.

Roentgen stereophotogrammetric analysis (RSA) was used to evaluate the migration in 17 cemented acetabular components after revision operations for mechanical loosening. All of the hips were examined four months and one year after surgery; ten of the hips were also examined after two years. In 15 of the 17 components, definite migration (0.5-2.7 mm) was identified, whereas two acetabular components showed no significant migration (< 0.25 mm). In 13 hips, the migration was seen within four months after surgery. There was a tendency for larger migration in revisions for severe bone destruction. These findings indicate that prosthetic fixation in revision operations is relatively poor. In cases with severe bone loss, cement fixations is extremely poor.

Acetabulum↗
PubMed1993

Instability and femoral head vitality in fractures of the femoral neck.

Sixteen patients with femoral neck fractures were studied with roentgen-stereophotogrammetric analysis (RSA) and low-field magnetic resonance (MR) imaging in addition to plain roentgenography. In six patients, these results were compared with the results of histopathologic analyses. All fractures were stabilized with two cannulated titanium screws. Evaluation of fracture movement before weight bearing (nine fractures) revealed no or only slight movement (less than 3.4 mm or 4.7 degrees). During weight bearing, two undisplaced fractures were compressed about 5 mm and one 20.3 mm, because of delayed union, which was verified by repeated RSA measurements and MR imaging. The average compression in nine displaced fractures that subsequently healed was 13.3 mm. MR imaging revealed signs of femoral head necrosis in three healed and two unhealed fractures. Segmental or total femoral head necrosis was histologically confirmed in all removed femoral heads, and the fracture areas were shown to be bridged by bone trabeculae to a varying degree. Absence of micromovement six months after fracture implied uncomplicated healing. Fracture stabilization at nine to 12 months postfracture was associated with femoral head necrosis or delayed union in four of six cases. Micromotion after more than one year indicated femoral head necrosis or pseudarthrosis.

Aged↗
PubMed1993

99mTc-diphosphonate scintigraphy in successful knee arthroplasty and its relation to micromotion.

Nineteen tibial components after successful knee arthroplasty were studied with technetium 99m scintigraphy. All cases were also followed from the operation with roentgen stereophotogrammetric analysis (RSA). All but three cases became stable after an initial period of migration. Scintigraphic uptake was found in all cases, with a ratio as high as seven in the medial compartment and three in the lateral compartment. A group of cases with proven mechanical loosening showed an uptake ratio as high as 6.9 in the medial compartment and 5.5 in the lateral compartment. No correlation was found between scintigraphic uptake and alignment, whether cement was used, or the presence/absence of migration. Technetium 99m scintigraphy is not a useful method for assessing loosening in individual symptomatic cases of knee arthroplasty.

Aged↗
PubMed1995

Image- and model-based surgical planning in otolaryngology.

Preoperative evaluation of any operating field is essential for the preparation of surgical procedures. The relationship between pathology and adjacent structures, and anatomically dangerous sites need to be analyzed for the determination of intraoperative action. For the simulation of surgery using three-dimensional imaging or individually manufactured plastic patient models, the authors have worked out different procedures. A total of 481 surgical interventions in the maxillofacial region, paranasal sinuses, orbit, and the anterior and middle skull base, in addition to neurotologic procedures were presurgically simulated using three-dimensional imaging and image manipulation. An intraoperative simulation device, part of the Aachen Computer-Assisted Surgery System, had been applied in 407 of these cases. In seven patients, stereolithography was used to create plastic patient models for the preparation of reconstructive surgery and prostheses fabrication. The disadvantages of this process include time and cost; however, the advantages included (1) a better understanding of the anatomic relationships, (2) the feasibility of presurgical simulation of the prevailing procedure, (3) an improved intraoperative localization accuracy, (4) prostheses fabrication in reconstructive procedures with an approach to more accuracy, (5) permanent recordings for future requirements or reconstructions, and (6) improved residency education.

Child↗
PubMed1995

Application of recent stereological tools for unbiased three-dimensional estimation of number and size of nuclei in renal cell carcinoma samples.

New stereological methods have appeared in recent years that allow an unbiased and efficient estimation of quantitative characteristics of three-dimensional biological structures. The aim of this study is to apply the new stereological tools on renal tissue and investigate the changes in the number and size of nuclei in renal cell carcinomas. The simple and easy use of the disector, point-sampled intercepts and selector methods on kidney biopsies is demonstrated. Using these approaches, the mean number of nuclei per unit reference volume: NV(nucl/tis), the volume-weighted mean nuclear volume: nu V(nucl) and the number-weighted mean nuclear volume: nu N(nucl) were estimated in histological sections from 20 renal cell carcinomas. The study was performed on 10 grade 2 and 10 grade 3 renal cell carcinomas previously diagnosed by the pathologist on the basis of nuclear size increase, irregularity and nucleolar prominence. Basically, serial optical kidney sections from a 25-millimicrons thick slice were used for stereological study. The size estimations of the individual particles nu V(nucl) and nu N(nucl) obtained by the 'point-sampled intercepts' and 'selector' methods, respectively, turned out to be the most adequate parameters employed in discriminating between renal carcinoma grades (P less than or = 0.001).

Carcinoma, Renal Cell↗
PubMed1995

Classification of colorectal adenomas with quantitative pathology. Evaluation of morphometry, stereology, mitotic counts and syntactic structure analysis.

In search for an objective classification rule for the morphologic changes in colorectal adenomas, the results of nuclear morphometry for assessing geometric characteristics of tumour nuclei, syntactic structure analysis for assessing the arrangement of nuclei in the epithelium, stereological assessment of glandular changes, and area weighted mitotic counts were evaluated in a multivariate analysis. The H&E stained tissue sections of 59 colorectal adenomas were studied, of which 20 showed mild, 20 moderate and 19 severe dysplasia, according to blind duplicate assessments by two pathologists. In a stepwise jackknifed discriminant analysis, the combination of variables was selected that could best discriminate the cases into the previously assessed grade of dysplasia. With the combination of two variables (minimum line length and inner gland surface density), 71% of the cases could be correctly classified according to the previously assessed grade. No cases with mild dysplasia were classified as severe dysplasia and vice versa. However, since the reproduction of subjectively assessed grade was not the ultimate goal, we aimed to discriminate the cases into two groups on the basis of measurements results alone, by means of a cluster analysis. These two groups would merely reflect the cases with major versus minor morphologic changes. The results of the cluster analysis showed that all mild dysplasia cases were allocated into the low grade cluster, and that the moderate dysplasia cases were divided over both the low grade and high grade cluster. Two severe dysplasia cases with borderline morphometric results were allocated into the low grade cluster, and the remaining 16 into the high grade cluster. It is concluded that objective evaluation of dysplasia in colorectal adenomas is possible by a combination of morphometric techniques. The results of the morphometric analyses seem to favor a two-grade classification system rather than a three-grade system.

Adenoma↗
PubMedDate not supplied

In vivo measurements of precision of fit involving implant-supported prostheses in the edentulous jaw.

The objective of this study was to measure and compare the precision of fit of implant-supported prostheses in the edentulous jaw by using both the master cast replicas and the intraoral implants as references. Seven maxillary and 10 mandibular prostheses were randomly selected and measured by means of a three-dimensional (3-D) photogrammetric technique. The results indicated that prostheses routinely connected to osseointegrated implants could demonstrate distortion between the framework and individual implants of up to several hundred microns. When master casts were used as a reference, the mean 3-D distortion of the center point of gold cylinders was 37 microns (SD 18) and 75 microns (SD 40) for mandibular and maxillary prostheses, respectively. The corresponding mean displacement was 90 microns (SD 51) and 111 microns (SD 59), respectively, when the intraoral implants were used as references. The mean 3-D distortion was significantly higher for the intraoral measurements in both arches (P < .001 and P < .05). Furthermore, the overall distortion was significantly higher for the maxillary prostheses when the master casts were used as the reference (P < .05). However, for the intraoral measurements, no statistically significant difference of fit between the arches was possible to observe (P < .05). This could possibly be explained by the finding that intraoral measurements of the mandibular prostheses indicated a deformation and rotation of the mandible that was not observed in the maxillary prostheses. A further factor in the lack of statistical significance could be the relatively small sample size.

Dental Abutments↗
PubMed1996

Monitoring surface shape variations on the human body.

Monitoring changes on the surface of the human body can be difficult due to the very unstable nature of skin. Stable control points between epochs are difficult to establish. This paper examines previous attempts to monitor the human surface. An algorithm is presented which is capable of matching two models of the one area on the human body which have been gathered at different epochs. No control points are required to exist on the human surface, or between epochs. Further, the algorithm is expanded to include surface differencing capabilities. This allows surfaces which have changed shape between epochs to be matched and the differences identified.

Algorithms↗
PubMed1996

Stereologic study of splenic tissue compartments from traumatically injured and cancer patients.

Carefully age-matched groups of patients, surgically treated for either traumatic injury (n = 5; mean = 71.2 years) or for early stage carcinoma (n = 5; mean = 74.2 years), were used to investigate all the splenic tissue compartments applying model-based stereology. The point-counting method was utilized to study the volume densities of following tissue compartments: red pulp, perifollicular zone, white pulp (this compartment was divided into two subcompartments: follicles and periarteriolar lymphatic sheath), marginal zone and connective tissue. The following stereologic parameters of lymphoid follicles were determined: areal numerical density (the number of follicles per mm2 of tissue section), the numerical density (number of follicles per mm3 of tissue), and the mean follicle diameter. The identity of tissue compartments was verified using immunohistochemical staining for B- and T- lymphocytes. Significantly increased volume densities of perifollicular zone and periarteriolar lymphatic sheath were registered in patients treated for traumatic spleen injury. On the other hand, the significantly increased number of lymphoid follicles per mm2 and per mm3 of splenic tissue were registered in the group of cancer patients. The differences observed, whether attributable to the immune stimulation of the ruptured spleen or the alterations of the immune system due to malignant disease, suggest that this issue deserves further attention.

Aged↗
PubMed1996

Migration of cemented femoral components after THR. Roentgen stereophotogrammetric analysis.

We studied the migration of 58 cemented Hinek femoral components for total hip replacement, using roentgen stereophotogrammetric analysis over four years. The implants migrated faster during the first year than subsequently, and the pattern of migration in the second period was very different. During the first year they subsided, tilted into varus and internally rotated. After this there was slow distal migration with no change in orientation. None of the prostheses has yet failed. The early migration is probably caused by resorption of bone damaged by surgical trauma or the heat generated by the polymerisation of bone cement. Later migration may be due to creep in the bone cement or the surrounding fibrous membrane. The prosthesis which we studied allows the preservation of some of the femoral neck, and comparison with published migration studies of the Charnley stem suggests that this decreases rotation and may help to prevent loosening.

Adult↗
PubMed1996

Single image random dot stereogram: principles and clinical implications.

BACKGROUND: The single image random dot stereogram is different from traditional stereograms in that it does not require a stereoscope or stereo glasses for viewing. There is an artistic variation of these stereograms in which the random dots have been replaced with colorful geometric patterns. An observer needs to view them according to specific instructions. While most observers can see the hidden stereo images after a few trials, some are not able to perceive the effect even after numerous attempts. METHODS: This paper explains the underlying principles by which these stereograms are constructed and describes the reasons why some individuals are not able to appreciate this stereo effect. A unique requirement for the successful viewing of these stereograms is divergence of the eyes from the plane of the stereogram. This unusual divergence may be the reason for unsuccessful viewing. By converting a single image random dot stereogram to a Brewster stereogram, an observer can view the same stereogram with a stereoscope, thus eliminating the divergence requirement. RESULTS: Using this modified viewing method, some previously unsuccessful observers were able to see the stereo effect. CONCLUSIONS: The main reason for unsuccessful viewing by a person with normal stereo vision is an inability to initiate or maintain the proper amount of divergence.

Depth Perception↗
PubMed1996

Knee joint loading and tibial component loosening. RSA and gait analysis in 45 osteoarthritic patients before and after TKA.

We report a prospective study of gait and tibial component migration in 45 patients with osteoarthritis treated by total knee arthroplasty (TKA). Migration was measured over two years using roentgen stereophotogrammetry. We used the previously established threshold of 200 microm migration in the second postoperative year to distinguish two groups: a risk group of 15 patients and a stable group of 28 patients. We performed gait analysis before operation and at six months and at two years after TKA. On all three occasions we found significant differences between the two groups in the mean sagittal plane moments of the knee joint. The risk group walked with higher peak flexion moments than the stable group. The two groups were not discriminated by any clinical or radiological criteria or other gait characteristics. The relationship which we have found between gait with increased flexion moments and risk of tibial component loosening warrants further study as regards the aetiology of prosthetic loosening and possible methods of influencing its incidence.

Aged↗