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At least 1,477 records · Page 82Linked to original sources
PubMed1996

Migration and wear of a hydroxyapatite-coated hip prosthesis. A controlled roentgen stereophotogrammetric study.

A consecutive series of 30 total hip replacements using a hydroxyapatite (HA)-coated, modular implant (Omnifit) was followed clinically and by roentgen stereophotogrammetric analysis for two years and compared with two control groups, one of 27 cemented Charnley sockets and one of 40 cemented Charnley stems. Omnifit sockets with a central gap between the dome of the socket and the acetabular bone in the postoperative radiographs, migrated less than sockets without such gaps (p = 0.01). After adjustment for patient-related factors (age, gender and weight), no significant difference was found between the two prostheses with respect to micromotion and wear. We conclude that the early fixation of the HA-coated Omnifit prosthesis compares with that of the cemented Charnley prosthesis.

Adult↗
PubMedDate not supplied

Prosthesis misfit and marginal bone loss in edentulous implant patients.

The objective of this study was to statistically correlate in vivo measurements of prosthesis misfit and change of marginal bone level in implants placed in the edentulous maxilla. Two groups, each comprising seven patients, were followed up either prospectively for 1 year or retrospectively for the last 4 years of the 5-year period after second-stage surgery. Measurements of prosthesis misfit were performed by means of a three-dimensional photogrammetric technique, and marginal bone levels were measured from standard intraoral radiographs. Results showed that none of the prostheses presented a completely passive fit to the implants in vivo. Furthermore, similar distortions of the prostheses were found in the two groups, indicating that the implants seemed to be stable and did not move, even after several years in function. The maximal range of three-dimensional distortion of cylinder center points was about 275 microns for both groups. Mean center point misfit was 111 (SD 59) and 91 (SD 51) microns for the 1-year and 5-year groups, respectively. The corresponding mean marginal bone loss was 0.5 and 0.2 mm for the two follow-up groups. No statistical correlations (P > .05) between change of marginal bone levels and different parameters of prosthesis misfit were observed in the two groups. The study indicated that a certain biologic tolerance for misfit may be present. The degree of misfit reported in the study was clinically acceptable with regard to observed marginal bone loss.

Adaptation, Physiological↗
PubMed1996

The mobility of the sacroiliac joint in healthy subjects.

A three-dimensional stereophotogrammetric method is described for measuring the mobility of the sacroiliac joint, which was based on preliminary two-dimensional in vitro experiments. The investigations were carried out with intraosseous markers in 24 healthy volunteer male (15) and female (9) subjects having an age range of 20 to 50 years. Considerable intra- and inter-individual variability was found for both the measurements of rotation and translation. The position and direction of the movement axes showed wide variations, but a basic pattern could always be recognized. The average values for rotation and translation were low, being 1.8 degrees / 0.7 mm for the males and 1.9 degrees / 0.9 mm for the females. No statistically significant differences could be demonstrated with respect to either sex or age. On the basis of the measurement results, it is postulated that there is pathological sacroiliac joint movement when rotation is more than 6 degrees and translation more than 2 mm. This increased mobility seems to be of greater clinical significance than reduced mobility.

Adult↗
PubMedDate not supplied

Dentin adhesive superior to copal varnish in preventing microleakage in primary teeth.

Microleakage presents a major challenge to the success of all restorations placed in the oral cavity, resulting in postoperative sensitivity, pulpal irritation, and secondary caries formation. The objective of this study was to evaluate the effects of an adhesive cavity liner under amalgam restorations in primary teeth. Sixty class V amalgam restorations were placed on the buccal and/or lingual surfaces of 38 primary molars and canine teeth. A dentin adhesive cavity liner was placed under 20 of the amalgam restorations. Another 20 restorations were lined with copal cavity varnish prior to amalgam condensation. The remaining 20 had no liner. All teeth were thermocycled in 0.5% basic fuschin dye, sectioned, and examined under a stereomicroscope to evaluate microleakage. While all specimens demonstrated leakage around the margins of the restorations, only the teeth with adhesive resin liners prevented leakage into the dentinal walls of the restoration. The copal cavity varnish group displayed microleakage approaching the pulpal chamber, whereas the unlined specimens consistently displayed dye penetration into the pulp chamber. At P < 0.01, the use of an adhesive cavity liner under amalgam restorations in primary teeth resulted in significantly less microleakage.

Adhesives↗
PubMed1997

Stereo fluoroscopy-assisted percutaneous needle puncture of the vertebral body.

The purpose was to determine whether real-time three-dimensional imaging by stereo fluoroscope could alleviate the nuisance of moving the fluoroscope C-arm during needle biopsy of the spine. Fifteen lumbar vertebrae of four beagle dog cadavers were used in a simulation. We used a newly devised portable-type stereo fluoroscope, which alternatively exposes the X-ray from left and right X-ray tubes so that a surgeon can decode left and right images displayed alternately on a monitor by using polarizing glasses. A 2-mm-diameter Kirschner wire was inserted into the vertebral bodies by a posterolateral approach without moving the C-arm. An axial view of the roentgenogram of each vertebra found all 15 wires to be appropriately inserted. This would appear to be a time-saving feature.

Animals↗
PubMed1996

[Radiological study of the migration of prosthetic implants following hip arthroplasty].

Migration of the acetabular and femoral implants after THR is a better index of the stability of the bone-implant interfaces than are clinical or radiological results. Roentgenstereophotogrammetry (RSA) studies 3-D migration of the implants with high accuracy (0.15 to 0.28 mm for linear migrations). RSA presents several drawbacks which restrict its use to prospective studies on small numbers of patients. Simpler methods have therefore been developed to assess 2-D migration on standard films in retrospective studies. The precision of these "simple" methods is limited, due to several factors: the difficulty to define reliable landmarks on femur or pelvis, sometimes even on implants, measurement errors, related to variations in radiographic technique (focal distance, beam centering, patient positioning). Sutherland, Wetherell and Nunn have proposed methods with an accuracy around 2-3 mm. It appears impossible to correct migration measurements for distorsions due to patient positioning; the EBRA method was therefore developed to reject non-comparable films using a comparability algorithm. A precision of 0.20 to 0.32 mm can thus be reached for the study of cup migration. The same pitfalls are encountered in assessment of migration of the femoral implant; a preliminary theoretical study is mandatory for every implant studied. The data presently available show that migration at 2 years is predictive of the long-term evolution of an implant; for the cup, migration of 1 mm or more at 2 years is predictive of late failure, and similar conclusions can be drawn regarding the femoral implant. The 2-D assessment of implant migration using a correct "simple" method provides a mean to evaluate a new implant or an innovative technical modification in a reasonable amount of time, on a limited number of patients.

Acetabulum↗
PubMed1977

Photogrammetric calibration of electron microscopes.

Attention is drawn to sound mensural calibration of the electron microscope system. A general understanding of the inherent distorsions is imperative. By using the collinearity condition and a photogrammetric self-calibration technique, one obtains the patterns of scale, radial, tangential and spiral distorsions. These are discussed and fundamental concepts involving such calibrations are presented. Some actual data are presented for illustration purposes.

Calibration↗
PubMedDate not supplied

Photogrammetric analysis of the three-dimensional geometry of normal and glaucomatous optic cups.

Using photogrammetrically generated maps and measurements, the geometric configuration of the optic cups from a group of normal, hypertensive, and glaucomatous eyes were analyzed in detail. Six distinct three-dimensional shapes were found to characterize the range of normal cups. These forms closely resemble a cone, a cylinder, a hemisphere, a cone-cylinder, a cone-hemisphere, and a cylinder-hemisphere. A composite picture of glaucomatous change was produced by collating the data obtained from different nerve heads which were thought to represent serial stages of disease. Among the many topographic features identified by this analysis is the early deepening of the optic cup which seems to take place only in disc in which the lamina was not visible before glaucoma began. In cups in which this process has occurred and in those in which the lamina was already exposed during the physiologic state, no further increase in the maximum value of this dimension appears to take place until late in the course of the disease. On the surface of the disc, the pattern of erosion is more vertical than horizontal in direction, creating a vertically oriented ellipse of the cup orifice. Its enlargement occurs in a concentric fashion and usually leads to the disappearance of the superior or inferior disc margins or both before losing the rest of the rim. In spite of the precision with which the optic cup morphology was mapped and measured, the end result still lacks the specificity which could be achieved by actually following the same optic discs while they are undergoing progressive atrophy. Such a study is now underway.

Glaucoma↗
PubMed1997

Radiostereometry of hip prostheses. Review of methodology and clinical results.

Radiostereometric analysis is a science that enables reliable measurements to be made from radiographs. The method involves several steps including insertion of spheric tantalum markers, radiographic examinations, measurements of radiographic films, and calculations of three-dimensional movements. The precision of the method corresponding to the 99% significance interval varies between 0.15 and 0.6 mm and 0.3 degree and 2 degrees when applied to total hip replacement depending on the technique used. Measurements of implant micromovement during 1 to 2 years after surgery have proved to be of value to predict later clinical failure because of aseptic loosening and revision. Subsidence of the femoral stem or proximal migration of the acetabular cup between 1 and 2 mm has indicated increased risk of early or intermediate term revisions in those prosthetic designs studied so far. Minimum early migration has been recorded for clinically well documented nonpolished stems and polyethylene cups, which probably is one explanation for their long term success. This small amount of early micromotion also has been found in porous coated and screw fixated press fit cups and all hydroxyapatite coated designs hitherto studied. As a first step in a clinical evaluation of new implants or surgical techniques, the predictive value of radiostereometric analysis measurements can be used to reduce the number of patients exposed to the potential risk of clinical failure.

Arthroplasty, Replacement, Hip↗
PubMed1997

A three-dimensional imaging system for archiving dental study casts: a preliminary report.

Dental study casts form an essential part of patient records for both diagnostic and medicolegal purposes. Storage of study casts poses major problems because of inconvenience and cost of mass storage. Various methods for recording and storage of study casts are discussed. A new biostereometric technique for digitally recording and storing dental casts, and using the recent advances in stereophotogrammetry, is presented. Archiving dental casts in a digital format would reduce problems of mass storage and provide new benefits such as duplication of casts and use in clinical and research studies.

Archives↗
PubMed1996

Three-dimensional modeling for modern diagnosis and planning in maxillofacial surgery.

The existing methods of recording the face in three dimensions are reviewed, and a new method for three-dimensional facial modeling is introduced. The technique utilizes two stereo pairs of videocameras, a stereo pair at each side of the patient's face. The system allows rapid capture of the face in three dimensions and precise measurement of anatomic landmarks. The system can be used to capture the facial image and a cephalogram almost simultaneously, allowing more accurate superimposition of soft and hard tissues. This precision will facilitate development of the surgical treatment plan. A computer program in the early stages of development will use the data generated by this biostereometric measurement system to predict soft tissue changes following orthognathic surgery.

Cephalometry↗
PubMed1998

Early inducible displacement of tibial components in total knee prostheses inserted with and without cement: a randomized study with roentgen stereophotogrammetric analysis.

The fixation of tibial components randomized to insertion with or without cement in twenty-six knees was examined for inducible displacement at six weeks and one year postoperatively with use of roentgen stereophotogrammetric analysis. Furthermore, migration was studied during the first two postoperative years. Inducible displacement was found in all knees at both the six-week and the one-year follow-up examination, but no differences were detected with respect to the type of fixation (p > 0.05). All tibial components migrated for as long as one year postoperatively, after which most stabilized. No difference was found between the groups with respect to migration during the first two years postoperatively (p > 0.05), with the exception of subsidence of the component, which was found to be 0.0+/-0.1 millimeter (mean and standard error of the mean) for the components inserted with cement and 0.5+/-0.1 millimeter for the components inserted without cement (p < 0.01). Migration after one year was the same for both groups. We found a relationship between inducible displacement at six weeks and at one year as well as one between inducible displacement and migration at one year. To our knowledge, the present study is the first in which the micromotion of an interference-fit prosthesis was found to be similar to that of a device inserted with cement. The results of the present study emphasize the importance of the initial prosthetic fixation.

Aged↗
PubMed1976

Effects of anticopper therapy on hepatocellular mitochondria in patients with Wilson's disease: an ultrastructural and stereological study.

Liver biopsy specimens from 7 patients with Wilson's disease (hepatolenticular degeneration), obtained before and after 3 to 5 years of D-penicillamine therapy, were studied by electron microscopy and stereology. The characteristic mitochondrial abnormalities encountered in the hepatocytes of untreated patients were less pronounced or disappeared after treatment in 5 of the 7 patients. Simultaneously, relative mitochondrial volume, surface density of the external mitochondrial membranes, and the number of these profiles per unit area increased, whereas abnormal elevations SGOT and SGPT returned to normal levels.

Adolescent↗
PubMed1998

Three-dimensional spinal coupling mechanics: Part I. A review of the literature.

OBJECTIVE: To determine the state of knowledge relative to three-dimensional spinal coupled motion and to check the validity of currently accepted two-dimensional coupling as taught in chiropractic. DATA COLLECTION: A hand search of available reference texts and a computer search of literature from Index Medicus were collected with an emphasis on three-dimensional studies of human spinal movements. RESULTS: Most postural movements result in complicated three-dimensional spinal coupling in six degrees of freedom. Previous spinal coupling results based upon two-dimensional radiographic studies are inadequate and inaccurate. It is important that chiropractic colleges and techniques use the three-dimensional spinal kinematics to update their curricula and advance chiropractic treatment procedures. CONCLUSION: Full three-dimensional investigations of spinal coupling patterns have shown that the vertebrae rotate and translate in all three axes and that previous theories of spinal coupling based upon two-dimensional studies are inaccurate and invalid. Postural rotations and translations, which are the main motions studied in spinal coupling research, and altered configurations of the normal sagittal plane curves are the cause of both normal and abnormal spinal coupling patterns in three dimensions. Chiropractic letter listings (such as PRS, ASRP, etc.) are outdated, incomplete, invalid representations of coupled segmental movements. Mechanical loading of the neuromusculoskeletal tissues plays a vital role in position, dynamics, proper growth, repair and symptoms. Future studies of spinal kinematics should study the postural translations of the skull and thorax for their associated coupling in three dimensions. Combined postural rotations and translations along with altered sagittal curvatures need to be studied for their associated coupling characteristics as well.

Biomechanical Phenomena↗