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At least 343 records · Page 19Linked to original sources
PubMed1999

Mid-term migration of a cemented total hip replacement assessed by radiostereometric analysis.

We have previously reported the short-term migration of cemented Hinek femoral components using radiostereometric analysis (RSA). We now report the mid-term migration. During the first 2 years after implantation the prosthesis subsided into varus and rotated internally. Between years 3 and 8 the prosthesis continued to rotate internally with the head moving posteriorly (0.07 mm/year, P=0.004). It also continued to fall into varus with the tip moving laterally (0.07 mm/year, P=0.04). The head (0.06 mm/year, P<0.0001), shoulder (0.04 mm/year, P=0.0001) and tip (0.04 mm/year, P=0.001) continued to migrate distally. There were two cases of failure due to aseptic loosening during the follow-up period. During the second year both of these had posterior head migration, which was abnormally rapid (>2 SD from the mean). We have demonstrated that a cemented implant has slow but significant levels of migration and rotation for at least 8 years after implantation. Our study confirms that implants with abnormally rapid posterior head migration during the second year are likely to fail.

Bone Cements↗
PubMed2007

Stereolithographic reproduction of complex cardiac morphology based on high spatial resolution imaging.

BACKGROUND: Precise knowledge of cardiac anatomy is mandatory for diagnosis and treatment of congenital heart disease. Modern imaging techniques allow high resolution three-dimensional (3D) imaging of the heart and great vessels. In this study stereolithography was evaluated for 3D reconstructions of multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) data. METHODS: A plastinated heart specimen was scanned with MDCT and after segmentation a stereolithographic (STL) model was produced with laser sinter technique. After scanning the STL model with MDCT these data were compared with those of the original specimen after rigid registration using the iterative closest points algorithm (ICP). The two surfaces of the original specimen and STL model were matched and the symmetric mean distance was calculated. Additionally, the heart and great vessels of patients (age range 41 days-21 years) with congenital heart anomalies were imaged with MDCT (n=2) or free breathing steady, state free-precession MRI (n=3). STL models were produced from these datasets and the cardiac segments were analyzed by two independent observers. RESULTS: All cardiac structures of the heart specimen were reconstructed as a STL model within sub-millimeter resolution (mean surface distance 0.27+/-0.76 mm). Cardiac segments of the STL patient models were correctly analyzed by two independent observers compared to the original 3D datasets, echocardiography (n=5), x-ray angiography (n=5), and surgery (n=4). CONCLUSIONS: High resolution MDCT or MRI 3D datasets can be accurately reconstructed using laser sinter technique. Teaching, research and preoperative planning may be facilitated in the future using this technique.

Adolescent↗
PubMed2003

Hip revision with impacted morselized allografts: unrestricted weight-bearing and restricted weight-bearing have similar effect on migration. A radiostereometry analysis.

BACKGROUND: No consensus exists as to whether to let patients bear weight or not after revision of a loosened hip prosthesis using morselized and impacted allograft bone and cement. In the original description of the method, the patients were advised not to bear weight for 3 months postoperatively. Theoretically, bone graft remodeling is enhanced by mechanical load, but an increased migration of the prosthesis within the graft can also be anticipated. In addition, practicing restricted weight-bearing is cumbersome for the patients. METHODS: The present study was initiated to evaluate the migration, as measured by radiostereometry analysis (RSA), in patients mobilized with unrestricted weight-bearing after a hip revision using the X-change Revision Instruments System. This group was compared with a previous series with restricted weight-bearing for the initial 3 months postoperatively. Seven stems and 12 sockets were evaluated by RSA over 2 years. Only patients without intraoperative complications were mobilized with unrestricted weight-bearing. RESULTS: All 7 stems migrated in the distal direction (median 2.6 mm; range 0.8-16.5 mm) and in the posterior direction (median 2.3 mm; range 0.7-22.1 mm). Eleven of the 12 sockets migrated in the proximal direction (median 2.5 mm; range 0.2-8.1 mm). The migration rate decreased gradually in all directions, but 3 stems and 5 sockets still migrated between the 1.5- and 2-year follow-ups. There were no significant differences in migration in any direction for either the stems or the sockets compared to the group with restricted weight-bearing. CONCLUSION: No increased migration occurred in the group free to bear weight as compared to restricted weight-bearing. We shall continue to allow unrestricted weight-bearing in cases where the femoral bone feels competent to withstand the initial load. It simplifies the postoperative mobilization, and we speculate that it might increase the remodeling of the graft.

Arthroplasty, Replacement, Hip↗
PubMed2006

The distal tibiofibular syndesmosis during passive foot flexion. RSA-based study on intact, ligament injured and screw fixed cadaver specimens.

INTRODUCTION: The aim of the study was to investigate the kinematics of the distal tibiofibular syndesmosis in intact and ligament injured ankles and to assess how effective is the syndesmotic screw in restraining mortise width variations during passive foot flexion. MATERIALS AND METHODS: The trials were carried out on seven fresh frozen cadaver specimens. The distal tibiofibular syndesmosis widening was investigated using Roentgen stereophotogrammetric analysis, in intact and ligament injured ankles and after the fixation of the syndesmotic screw. The AO-ASIF recommendations were followed for screw implant. RESULTS: Injury to the syndesmotic and deltoid ligaments of the ankle did not result in a significant variation of the syndesmosis behavior during passive foot flexion. The 4.5-mm diameter cortical screw used in this study proved effective in restraining mortise width variation during foot flexion. The recorded mortise widening in the flexion arc extending from the neutral to the maximally dorsiflexed position was negligible in intact and ligament injured joints. CONCLUSION: The result does not endorse the recommendation of placing the foot in full dorsal flexion during screw implantation. The choice of screw fixation as a treatment for ankle syndesmosis disruption should be carefully evaluated.

Ankle Injuries↗
PubMed1998

The relationship between deterioration and reversal of optic disc cupping in monkeys with chronic experimental high-pressure glaucoma.

PURPOSE: To investigate the correlation between the deterioration in optic disc cupping during the chronic elevation of intraocular pressure (IOP) and the reversal of cupping during a subsequent reduction in IOP in experimental glaucoma. METHODS: We examined changes in the vertical and horizontal cup to disc ratios, the rim area to disc area ratio, and the cup volume to disc area ratio in 11 monkey eyes with laser-induced glaucoma using computerized stereo-image analysis. Correlations between changes in disc parameters during a spontaneous IOP reduction and changes in disc parameters during a period of chronic IOP elevation from baseline before laser exposure (baseline) to before the IOP reduction (pre-IOP reduction) and during the period from baseline to after the reduction in IOP (post-IOP reduction) were determined by linear regression analysis. RESULTS: All disc parameters improved significantly during IOP reduction and deteriorated significantly during the periods from baseline to the pre-IOP reduction and from baseline to the post-IOP reduction. The degree of reversal in disc parameters was correlated with the deterioration from baseline to the pre-IOP reduction and from baseline to the post-IOP reduction in the vertical cup to disc ratio (r = 0.68, P = 0.0218 and r = 0.97, P < 0.0001, respectively), the horizontal cup to disc ratio (r = 0.57, P = 0.0649 and r = 0.98, P < 0.0001, respectively), the rim area to disc area ratio (r = 0.68, P = 0.0227 and r = 0.98, P < 0.0001, respectively), and the cup volume to disc area ratio (r = 0.67, P = 0.0256 and r = 0.88, P = 0.0004, respectively). CONCLUSION: The degree of deterioration in cupping from baseline before the induction of glaucoma may be an important determinant of the degree of cupping reversal during subsequent reductions in IOP in primate glaucoma.

Animals↗
PubMed2005

Comparing precision of distortion-compensated and stereophotogrammetric Roentgen analysis when monitoring fusion in the cervical spine.

Two methods to measure sagittal plane segmental motion in the cervical spine are compared. Translational and rotational motion was measured in nine cervical motion segments of nine patients by distortion-compensated (DCRA) as well as by stereophotogrammetric Roentgen analysis (RSA). To compare measurement precision of the new DCRA protocol with the established RSA technique under realistic clinical conditions and to discuss advantages and disadvantages of both methods in clinical studies. RSA constitutes the most precise method available to assess segmental motion or to monitor fusion in the cervical spine. Due to the invasive nature of the procedure there is an interest in alternative, non-invasive protocols, based on conventional, lateral radiographic views. In nine patients, segmental motion of nine cervical segments with spinal surgery and fusion had previously been assessed from stereo views by RSA. From the archive radiographs, sagittal plane segmental motion was re-assessed by DCRA. Results for sagittal plane translational and rotational motion obtained by both methods are compared. With respect to RSA, sagittal plane rotation was determined by DCRA with an error of 2.4 degrees and a mean difference not significantly different from zero. Sagittal plane translation was determined by DCRA with an error of less than 0.78 mm and a mean difference not significantly different from zero. As two methods are compared, these errors represent the combined (propagated) errors of RSA and DCRA. Averaged over the cohort investigated, measurement of sagittal plane segmental motion exhibited no significant difference between DCRA and RSA.

Cervical Vertebrae↗
PubMed2000

A method to evaluate the in vivo behaviour of lumbar spine implants.

The aim of the study was to design a method for evaluating the stabilizing effect of different lumbar spine implants in vivo, and to apply this method to a comparison of plates versus rods in lumbar spine posterolateral fusion using transpedicular screw fixation. Fourteen patients, seven operated on with transpedicular plates and screws (VSP), and seven operated on with rods and screws (Diapason), matched according to number of levels fused, had tantalum markers inserted in the vertebrae at surgery, enabling roentgen stereophotogrammetric analysis (RSA). Mean patient age was 45 (range 33-56) years. In each group, two patients underwent fusion between L4 and L5, three between L5 and S1, and two from L4 to S1. In three patients, concomitant nerve root decompression was performed using a facet joint preserving technique. RSA was performed 4 weeks after surgery. This interval was chosen to allow enough time for soft tissue healing, but not fusion healing, to occur. RSA was performed in supine and standing position without any mobility provocation, in line with the postoperative regimen given. Movements between the outermost vertebrae of the fusion were calculated along the transverse, vertical and sagittal axes. The method of measurement along these three axes has previously been determined to be accurate to 0.3, 0.6 and 0.7 mm, respectively. One patient stabilized with rods and screws between L5 and S1 displayed a sagittal translation of 1.01 mm but no mobility along the transverse or vertical axes. In the remaining 13 patients, positional change from supine to standing did not provoke any intervertebral mobility above the RSA accuracy along any of the axes. With the limited provocation described, in line with the postoperative regimen for lumbar fusion patients, plates with transpedicular screws and rods with transpedicular screws both seem to give adequate intervertebral stability in posterolateral lumbar fusions.

Adult↗
PubMed2000

[Initial experiences with digital 3-dimensional stereophotogrammetry imaging].

A digitised three-dimensional (3-D) image of the face has many valuable uses. These include accurate measurements of facial morphology, clinical documentation and objective analyses of surgical procedures. A new system presented here, based on stereophotogrammetric techniques, instantaneously captures digitised images using high-resolution cameras. It has an accuracy of more than 0.5 mm RMS and creates the 3-D image from approximately 20,000 points. The principles of the image capturing are demonstrated and the potential uses discussed. Surgical changes of the soft tissue in two patients following orthognathic surgery are also illustrated. This new capturing and measurement system provides a simple method of determining 3-D changes in soft tissue following surgery and is a useful tool for clinical purposes.

Adult↗
PubMed2006

Effect of marker cluster design on the accuracy of human movement analysis using stereophotogrammetry.

This paper presents a new, simple model to evaluate the instrumental random errors in kinematic analysis of human movements using stereophotogrammetry. By means of equations analogous to that relate linear or angular momentum with linear or angular velocities, a direct measurement of instantaneous motion can be made without previous finite displacement analysis. Single explicit expressions can be obtained to evaluate the influence of instrumental random errors in the accuracy of the kinematic variables. From these expressions, some conclusions about the effect of marker cluster design on the experimental errors are obtained. An experiment has been carried out in order to validate the proposed technique and to assess the experimental errors in linear and angular velocity measurement and its influence in instantaneous helical axis determination.

Biomechanical Phenomena↗
PubMed1975

Photogrammetric analysis of volume asymmetry of the optic nerve head cup in normal, hypertensive, and glaucomatous eyes.

Recent studies of optic cup volume, depth, and orifice area demonstrated a large overlap of the range of these factors for normal and glaucomatous eyes, suggesting that it is usually not possible to distinguish abnormal disks on the basis of a particualr set of geometric quantifiers. Because of the knowledge that qualitative asymmetry of a person's optic cups may be a sign of glaucoma, calculation of the quantity of cup asymmetry using the aforementioned geometric parameters was undertaken in 90 patients. Results indicated that 90% of the bilaterally normal subjects who were studied and 80% of the ocular hypertensives had less than 0.20 mm3 cup volume asymmetry. In contrast, however, all of the unilateral glaucoma patients in this sample exceeded that value. It therefore appears that measurement of the amount of, volume asymmetry between a person's optic cups may be a useful tool in the diagnosis of glaucoma.

Adult↗
PubMed1979

Comparison of photographic techniques and films used in stereophotogrammetry of the optic disk.

We compared photogrammetric measurements of optic cup volume, area, and depth made from two types of stereophotography and two types of film to determine their effect on the precision of the measurements. We found that measurements from simultaneous stereophotography (Donaldson stereoscopic fundus camera) had a smaller range of values and a smaller mean percent error than measurements from consecutive stereophotography (Zeiss Fundus Flash II camera). However, a Student's t-test for related measures showed no significant difference. The measurements from Kodachrome 25 film and Kodak Photomicrography film varied in range and mean percent error without a pattern. The Student's t-test for related measures showed no significant difference.

Evaluation Studies as Topic↗
PubMed1984

Reliability of optic disk topographic measurements recorded with a video-ophthalmograph.

The video-ophthalmograph records the topography of the optic disk via simultaneous stereoscopic images which are stored and analyzed with the help of a microcomputer. This information is used to generate the vertical cup-disk ratio, the vertical optic disk diameter, the cup volume, and the neuroretinal rim area. To determine the reliability of the data, we recorded information for one eye of each of five patients ten times to determine the interphotographic error variance. We also analyzed one photograph for each of five patients ten times to determine the intraphotographic variance attributable to repeated analysis of the same photograph. The interphotographic and intraphotographic coefficients of variation were 2% to 18% and 2% to 7% respectively for these measurements.

Computers↗
PubMed1989

Glaucomalike disks without increased intraocular pressure or visual field loss.

We studied 48 patients who had glaucomalike disks with increased cupping and pallor, superior or inferior extension of cupping and pallor and asymmetry of cupping and pallor between eyes without increased intraocular pressure or visual field loss, and open angles. We compared these patients with a randomly selected group of 48 patients with primary open-angle glaucoma. The mean age of the patients with glaucomalike disks (45.1 +/- 16.1 years) was significantly younger than the group with open-angle glaucoma (63.8 +/- 11.3 years). Of the patients with glaucomalike disks, 11 (23%) had a family history of glaucoma, 75% of 22 eyes with optic disk fluorescein angiograms had abnormal readings, and 59% of 43 eyes with retinal nerve fiber layer defects had abnormal readings. Photogrammetric measurements of the left disk cups were compared in 22 of the patients with glaucomalike disks to 16 matched patients with primary open-angle glaucoma. The only statistically significant difference was that the patients in the glaucoma group showed a larger cup area (surface opening) of the inferior quadrant. Our findings suggest that some glaucomalike disks may be one variant of primary open-angle glaucoma.

Adult↗
PubMed1977

Biostereometric analysis of surgically corrected abnormal faces.

Biostereometrics is an accurate anthropometric system for quantifying geometric changes of facial form and the relationship of features as they are influenced by growth and by surgery. Facial features distant from the site of surgical intervention are influenced in their geometric relationship to each other by changes in the soft-tissue drape brought about by manipulation of skeletal tissues. The most accurate coordinate system should be elsewhere than on the surface of the face, but if this is not possible it should be in an area farthest removed from the surgical site. This investigation demonstrates that a usable coordinate transformation system can be created by connecting points supernasale and subnasale for establishing the Y Z plane and the construction of the X Z plane at subnasale. Accurate comparative numerical measurements can be made by using soft-tissue landmarks.

Acrocephalosyndactylia↗
PubMed1980

Movement of maxillary segments after expansion and/or secondary bone grafting in cleft lip and palate: a roentgen stereophotogrammetric study with the aid of metallic implants.

The study was undertaken to examine the effects of expansion treatment and secondary bone grafting in cleft lip and palate. Movement of the lateral maxillary segments in four patients with complete bilateral cleft lip and palate (BCLP) was complicated and asymmetric, and a greater relative widening of the dental arch was observed. The least expansion was found in the oldest patient. Bone grafting did not bring about a stable relationship between the segments. The width of the dental arch was mostly maintained despite segmental movement. In one patient with unilateral cleft of the lip and primary palate (UCL) growth in the midpalatal suture followed the pattern observed in noncleft patients but was less extensive. Accurate and comprehensive recording of the relatively small maxillary movements requires that implant stability is checked and that a reference is established outside the maxilla.

Adolescent↗
PubMed1982

Posteroanterior traction in maxillonasal dysplasia (Binder syndrome). A roentgen stereometric study with the aid of metallic implants.

The study was undertaken to examine the effect of posteroanterior traction in an 11-year-old boy with maxillonasal dysplasia. Movement of the maxillary bones and of the mandible was recorded, by means of roentgen stereophotogrammetry, in relationship to the frontal bone during and after treatment. In the examined child face-mask therapy mainly influenced the position of the mandible while the recorded advancement of the maxillary bones was slight (0.6 mm.). It is possible that the limited maxillary response to traction may be due to insufficient growth capacity of the circummaxillary sutures in a child with maxillonasal dysplasia. While movement of the maxillary bones and of the mandible during traction conformed with the pattern of treatment effect described by Delaire a total maxillary relapse occurred in the posttreatment observation period (no retention), possibly in adaptation to the retropositioned mandible. In our patient, posteroanterior traction accomplished improvement of the maxillary retrusion in relationship to the mandible only.

Child↗
PubMed1986

Roentgen stereophotogrammetry for analysis of cranial growth.

A system of roentgen stereophotogrammetric analysis (RSA) has been developed and its value in studies of cranial growth in both man and the experimental animal (rabbit) has been delineated. This method is based on measurements from metal bone marker images on roentgenograms. Two roentgen tubes simultaneously expose the object, which is placed in one of two types of calibration cages. The object position does not need to be identical from one examination to the next. The cage, holding indicators of predetermined internal positions (in two or four planes), defines a laboratory coordinate system. Two-dimensional image coordinates are obtained by means of a highly accurate cartographic instrument. By computer reconstruction of the x-ray beams through the markers, 3-D object coordinates are calculated. For subsequent analysis of growth processes, extensive software is necessary. To control intrasegmental stability (routinely performed at each examination), a minimum of two markers is required, whereas three markers are needed in each skeletal segment for kinematic analysis using the rigid-body concept. Careful planning of marker placement before implantation minimizes implant loss and instability that otherwise might be a problem. Complications other than bone marker loosening have been nonexistent. The technical accuracy is high. Consequently, roentgen stereophotogrammetry, with the aid of metallic implants, is a superior means to obtain biometric information on cranial growth with relative ease.

Animals↗