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At least 1,441 records · Page 80Linked to original sources
PubMed1995

Micromotion of the acetabular component and periacetabular bone morphology.

The quality of the periacetabular bone might be an explanation for the increase in the rate of socket loosening seen radiographically in patients with rheumatoid arthritis as compared with patients with osteoarthrosis. Early implant micromotion, as measured by roentgen stereophotogrammetric analysis, is of predictive value with regard to long time retention. For uncemented porous sockets, the initial fixation might be decisive for the degree of bone ingrowth. Roentgen stereophotogrammetry was used to study cemented Charnley acetabular components in 32 hips with rheumatoid arthritis and 30 hips with osteoarthrosis, and uncemented Harris-Galante acetabular components in 19 hips with osteoarthrosis. Micromotions as long as 24 months after surgery were related to the periacetabular cancellous bone quality, as assessed by histomorphometric methods from samples taken during surgery. Acetabular components migrated more in hips with rheumatoid arthritis than in those with osteoarthrosis (p < 0.04). Hips with rheumatoid arthritis had approximately 4 times more nonmineralized bone than hips with osteoarthrosis (p < 0.0002). However, within each diagnostic group, no correlation was found between migration and the degree of mineralization (r < or = 0.24, p > or = 0.07). Migration of uncemented acetabular components did not correlate with the histomorphometric variables (r < or = 0.20, p > or = 0.42). Histomorphologic characteristics of the periacetabular trabecular bone do not seem to be of importance for acetabular component micromotion.

Acetabulum↗
PubMed1994

A high-resolution line sensor-based photostereometric system for measuring jaw movements in 6 degrees of freedom.

Photostereometry has widely been applied to the measurement of mandibular movements in 6 degrees of freedom. In order to improve the accuracy of this measurement, we developed a system utilizing small LEDs mounted on the jaws in redundant numbers and a 5000 pixel linear charge-coupled device (CCD) as a photo-sensor. A total of eight LEDs are mounted on the jaws, in two sets of four, by means of connecting facebows, each weighing approximately 55 g. The position of the LEDs are detected in three-dimensions by two sets of three CCD cameras, located bilaterally. The position and orientation of the mandible are estimated from the positions of all LEDs measured in the sense of least-squares, thereby effectively reducing the measurement errors. The static overall accuracy at all tooth and condylar points was considered to lie within 0.19 and 0.34 mm, respectively, from various accuracy verification tests.

Biomedical Engineering↗
PubMed1995

Roentgen stereophotogrammetric analysis as a predictor of mechanical loosening of knee prostheses.

The tibial components in 143 patients with total knee replacements performed before 1988 were assessed for micromotion using roentgen stereophotogrammetric analysis (RSA) over a period of 13 years. The fixation of the prostheses remained clinically sound in all cases, although revision had been required for other reasons in seven. In a second group taken from all cases with RSA available on our full database to 1990, 15 tibial components had been followed by RSA from the insertion until, 1 to 11 years after the initial arthroplasty, they were revised for mechanical loosening of the tibial component; 12 of these comprised all the loosenings in the base group, thus making a total of 155 consecutive cases, while an additional three were inserted after the base material had been compiled. The mean migration in the first group was about 1 mm at one year, but subsequent migration was slower, reaching a mean of about 1.5 mm after ten years. About one-third migrated continuously throughout follow-up, while two-thirds ceased to migrate after one to two years. In the revision group, 14 components had migrated continuously and at one year significantly more than those in the first group. One revision case lacked the crucial one-year follow-up and could not be classified. These findings suggest that mechanical loosening begins early in the postoperative period. Clinical symptoms which necessitate revision, seen at this stage in 20% of abnormally migrating tibial components, may not appear until up to ten years after the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

[Measurement of the polished surface of upper and lower complete dentures].

The authors measured the polished surface of fifty upper and lower complete dentures, with regard to sex. The measurements were performed using a special computer assisted stereo-fotogrammetric method in the National Cartographic Institute. The results show that the average area of the lower complete denture's polished surface is 2.096 mm2, and the upper's is, 3644 mm2. The authors did find any not differences according to sexes.

Computer-Aided Design↗
PubMed1995

Migration of the Charnley stem in rheumatoid arthritis and osteoarthritis. A roentgen stereophotogrammetric study.

Migration of 65 Charnley stems implanted with modern cementing techniques was studied by roentgen stereophotogrammetry. There were 25 patients with rheumatoid arthritis (RA) and 40 with osteoarthritis (OA) followed up for two years. In 43 cases a bone sample for histomorphometric analysis was obtained from the femur during the operation. In 22 cases the mean subsidence of the prosthetic head was 0.40 mm and in 20 the mean posterior migration was 1.25 mm. There was no difference in migration between the two diagnostic groups (p = 0.8) after adjusting for variations in gender, age and weight. Male gender was associated with increased subsidence (p = 0.006). Histological examination showed that the RA series had more osteoid surface (p = 0.04), but neither this, nor any of the other histomorphometric variables, influenced migration. These results suggest that, unlike the acetabular socket, the cemented Charnley femoral component is equally secure in osteoarthritis and in rheumatoid arthritis, and that its initial fixation is not influenced by the quality of the local cancellous bone. Our results provide data with which the early performance of new prosthetic designs and fixation methods can be compared.

Analysis of Variance↗
PubMed1994

Does early micromotion of femoral stem prostheses matter? 4-7-year stereoradiographic follow-up of 84 cemented prostheses.

Roentgen stereophotogrammetry was used to measure the migration of the centre of the femoral head in 84 cemented Lubinus SP I hip arthroplasties (58 primary operations, 26 revisions). Four to seven years later, seven femoral components had been revised because of painful loosening. These implants showed greater subsidence, medial migration and posterior migration during the first two postoperative years than did the hips which had not been revised. Six months after operation, subsidence of more than 0.33 mm combined with a total migration of more than 0.85 mm predicted an increased risk of subsequent revision; the amount of subsidence at two years was an even better predictor. The probability of revision was greater than 50% if the subsidence at two years was 1.2 mm or more.

Adult↗
PubMed1994

[Stereo-phlebographic examination and surgical treatment of varicose veins of the lower extremities].

The article deals with the little-known method of stereophlebographic examination of patients with varicosity of the lower limb veins. The method and techniques of stereophlebography, planning of the operation and the sequence of its performance are described. The work generalizes 10-year experience in the use of this method in the management of patients. Seven thousand patients were examined and operated on by this method during the 10-year period, 4,500 of them in the recent three years; the results were good.

Humans↗
PubMed1993

Basics of three-dimensional endoscopic vision.

The requirement of stereoscopic vision is based on the need for controlled manipulations in the object space. With the introduction of endoscopic surgery stereoscopic controlled manipulations proved to be helpful. Beyond this, the enhanced perceptibility of details and surfaces of pathological structures brought about by stereoscopy may lead to improvements in endoscopic diagnosis. The basic principle of stereoendoscopy is to make use of a combination of two monocular endoscopes aligned and adjusted for stereoscopic vision. The small objective base provides good perception of depth in a certain region close to the tip of the stereoendoscope. A set of stereoscopic equipment consists of various stereoendoscopes, a stereoscopic observing adapter, a stereo-video camera, and a stereoscopic monitor.

Accommodation, Ocular↗
PubMed1993

3-D video techniques in endoscopic surgery.

Three-dimensional visualisation of the operative field is an important requisite for precise and fast handling of open surgical operations. Up to now it has only been possible to display a two-dimensional image on the monitor during endoscopic procedures. The increasing complexity of minimal invasive interventions requires endoscopic suturing and ligatures of larger vessels which are difficult to perform without the impression of space. Three-dimensional vision therefore may decrease the operative risk, accelerate interventions and widen the operative spectrum. In April 1992 a 3-D video system developed at the Nuclear Research Center Karlsruhe, Germany (IAI Institute) was applied in various animal experimental procedures and clinically in laparoscopic cholecystectomy. The system works with a single monitor and active high-speed shutter glasses. Our first trials with this new 3-D imaging system clearly showed a facilitation of complex surgical manoeuvres like mobilisation of organs, preparation in the deep space and suture techniques. The 3-D-system introduced in this article will enter the market in 1993 (Opticon Co., Karlsruhe, Germany.

Animals↗
PubMed1994

True three dimensional stereographic display of 3D reconstructed CT scans of the pelvis and acetabulum.

Fractures of the acetabulum can cause the pelvis to shatter into a wide array of complex configurations which can be difficult to fully delineate preoperatively. In addition to plain radiography and standard computed tomography, technology now allows the reconstruction of magnetic resonance imaging (MRI) and computed tomography (CT) data into virtual objects; three dimensional (3D) representations of anatomy which exist only within the computer memory. Printouts and photographs of 3D reconstructions provide another level of anatomic information to the orthopaedic surgeon. However, current standard displays such as computer and video screens and photographic and radiographic film are all two dimensional (2D) modalities. Displaying 3D reconstructions in this standard 2D fashion, inescapably robs the images of up to one third of the information contained within them--all the true depth information which is the essence of 3D. Shading techniques and perspective have both been utilized to simulate depth, but true depth is still lacking. Recently, the authors have begun using a technique of computerized 3D reconstruction and recording which provides a true 3D display of the reconstructed images. The resultant gain in image realism is profound, somewhat similar to hearing full stereo audiophonic recording compared to monophonic, or to seeing in color rather than black and white. The image generation and display process is a computerized mathematical adaptation of the photographic technique of stereophotography. Once in place, the technique is relatively simple to use and can be achieved in several ways with a minimum of additional hardware. Potential benefits lie in the method's ability to convey, in one 3D display, the true 3D, spatial anatomic configuration of the imaged pelvis. The methods described are common to those forming the fundamental basis for virtual reality imaging. Current users of some 3D reconstruction systems can now easily generate images which can be viewed with all of the depth information restored, into a true 3D display.

Acetabulum↗
PubMed1994

Effect of low level energy laser irradiation on gingival inflammation.

The effect of low level energy infra-red laser irradiation on gingival inflammation was studied. Gingivitis was induced in ten female dental students by refraining from all oral hygiene measures for 28 days. On days 21 and 24 the marginal gingiva, buccal to one of the lateral mandibular incisors, was exposed to 4 minutes of laser irradiation (total dose = 1J). Serving as a control site the gingiva of the contralateral incisors was exposed to ordinary light. There was no statistical difference between the laser exposed sites and the control sites related to either plaque formation or gingival bleeding. The gingivitis reaction was evaluated with the aid of a stereophotographic method by calculating changes in the number of gingival vessels. It was found that the number of vessels identified increased over time for both laser exposed and control sites. The difference between sites at day 28 was not statistically significant (t = 0.82, P > 0.05). These results suggest that low energy laser irradiation (LLLT) does not influence the inflammatory reaction of the gingiva.

Adult↗
PubMed1994

Computer simulation of glenohumeral and patellofemoral subluxation. Estimating pathological articular contact.

Analytic stereophotogrammetry and an interactive computer graphics program were used to obtain first order assessments of joint contact patterns in patellofemoral and glenohumeral joints, simulating normal and abnormal articulations. Precise (90 microns accuracy) computer graphic representations of the humeral head, glenoid, patella, and femoral articular surfaces were obtained from cadaver knees and shoulders. These surface representations were then manipulated into an articulated position, and joint contact areas computed by a proximity criterion. Pathologic states were then simulated, and contact recomputed. Simulated glenohumeral subluxations dramatically reduced contact area, and focused it eccentrically on the glenoid rim. Simulated size mismatch of humeral heads to glenoids reduced contact area, producing a pattern of peripheral contact on the glenoid if the humeral head had a larger radius of curvature, and central contact on the glenoid if the humeral head had a smaller radius of curvature. At 30 degrees knee flexion, the patellofemoral joint demonstrated a broad distribution of contact along the distal aspect of the patella and proximal aspect of the trochlea. Simulated lateral tilt (5 degrees) and translation (5 mm) of the patella resulted in shift of the predominant contact area laterally, along with a drastic decrease in the contact area. These results have implications for prosthetic sizing and biomechanical modeling of the glenohumeral and patellofemoral joints, and in selecting models for more rigorous empiric studies of joint contact. Furthermore, this technique allows a first order assessment of the effects of specific surgical reconstructions on articular mechanics.

Computer Graphics↗
PubMed1993

The evaluation of prosthetic components in total joint replacement.

Evaluation of prosthetic components for total joint replacement has been attempted using a number of methods, most of which have defects. Clinical studies using scores have severe limitations; survivorship studies represent a fairly crude way of assessing new prosthetic components, and they require long periods of observation. Radiological evaluation is often subjective, as are most studies on component migration. There are fortunately alternative methods, such as roentgen stereophotogrammetric analysis, which give objective results within short delays; new methods are being developed which can provide similar information at a more reasonable expense. Illustrative studies are reported, and it is concluded that new components should be evaluated by measuring their early migration rate, which is shown to have a predictive value.

Acetabulum↗
PubMed1994

Influence of soft structures on patellar three-dimensional tracking.

During knee flexion, the human patella moves along a complex path resulting from the combined actions of articular contact and soft-tissue stabilization. The current study is an attempt to characterize the role of these soft structures on patellar kinematics. To this end, the three-dimensional patellar motion during full knee flexion was accurately measured before and after partial dissection of the joint. The guiding role of the femoral groove prevailed over soft-tissue action through most of the range of motion. At full extension, however, when the patella and the femur were not in contact, the influence of the retinaculi was most noticeable, highlighting the unstable behavior of the patella near extension. The differences between the intact and dissected knee kinematics suggested that control over patellar motion is ensured by the transverse soft-tissue structures near extension and by the patellofemoral joint geometry during further flexion.

Biomechanical Phenomena↗