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PubMed2002

Linear photogrammetric analysis of the soft tissue facial profile.

This study digitally analyzes the soft tissue facial profile of a European white population of young adults by means of linear measurements made on standardized photographic records taken in natural head position. The application of the Student t test showed sexual dimorphism in most parameters of the labial, nasal, and chin areas. In general, males had greater heights and lengths as well as greater prominences of these 3 areas. They also had greater nasal and facial depths at the level of the tragus point.

Adolescent↗
PubMed2002

Three-dimensional craniofacial reconstruction imaging.

This review article aims to describe and discuss the imaging techniques most commonly used in medicine and dentistry to obtain three-dimensional images of the craniofacial complex. Three-dimensional imaging techniques provide extensive possibilities for the detailed and precise analysis of the whole craniofacial complex, for virtual (on-screen) simulation and real simulation of orthognathic surgery cases on biomodels before treatment, as well as for the detailed evaluation of the effects of treatment. Laser scanning in combination with the stereolithographic biomodeling seems to be a very promising combination for three-dimensional imaging, although there is still considerable room for improvement. Constant efforts should be made in the direction of developing and enhancing the existing techniques as well as exploring the potential for developing new methods based on emerging sectors of technology.

Cephalometry↗
PubMed2002

Accommodation to large disparity stereograms.

PURPOSE: The purpose of this study was to test whether observers would show accommodation changes to depth depicted in large disparity stereograms and whether the amount of accommodation was related to the amount of depth seen in the stereograms. Previous studies have shown small accommodation changes to depth depicted in stereograms. We tested a larger range of depths than previously investigated and also asked observers to judge the depth depicted in the stereogram, because a previous study had suggested that this might be an important factor. METHODS: All our observers had emmetropia. Accommodation was measured with a Canon Autoref R-1autorefractor as an observer viewed a depthful 4-by-4 cm planar target set against a 20-by-20 cm planar background 57 cm from the observer. The target was presented at a range of depths, -8 to +8 cm, either in stereogram stimuli or real stimuli. Each observer also made depth judgments of stereogram targets, after training with real targets. We also recorded the time taken for each observer to discern the depicted depths in stereograms. RESULTS: The accommodation shown by all observers (n = 9) to stereogram targets was significant but was on average about 60% of that predicted. There were individual differences in the accommodation an observer showed to stereogram targets, but this was not related to the amount of depth the observer saw in the stereogram. CONCLUSIONS: Accommodation changes did occur to stereogram targets, but these were generally less than predicted and also less than those shown for real targets. Possible reasons for these findings and the implications for the use of stereograms in clinical tests are discussed.

Accommodation, Ocular↗
PubMed1997

Computerized measurement of the three-dimensional distribution of optic disc pallor.

PURPOSE: To describe a method which provides quantitative measurements of the surface area of pallor in each quadrant of the three-dimensional optic cup, using photogrammetric measurements from simultaneous stereophotographs and computerized image analysis. METHODS: Simultaneous stereophotographs of one normal subject and two subjects with primary open angle glaucoma were digitized and analyzed for depth measurements. The boundaries of the optic disc, optic cup and region of pallor were identified. Pallor/disc and pallor/cup ratios were subsequently calculated for the superior, temporal, inferior and nasal walls. RESULTS: A digitized photograph and a Laplacian-filtered image were obtained for each eye to be studied. After processing each stereo pair through a similarity sequential detection-based algorithm, depth measurements are represented as a grey scale image, a contour plot, and a wire mesh, with the boundaries of the optic disc, optic cup and pallor superimposed. Ratios are given of the surface area of pallor to the surface area of the disc and the surface area of pallor to the surface area of the cup, by quadrant. CONCLUSIONS: Determination of surface area of pallor to cup may be useful in detecting early visual field loss in glaucoma and neurological disease.

Adult↗
PubMed2000

Radiostereometric analysis in hip revision surgery--optimal time for index examination: 6 patients revised with impacted allografts and cement followed weekly for 6 weeks.

We revised the hip (6 stems and 5 sockets) with impacted morselized allografts and cement in 6 patients. We followed prosthetic migration by roentgen radiostereometric analysis (RSA) every 7th day for 6 weeks after the first (index) examination performed on the first postoperative day before mobilization. Most of the migration occurred during the first 2 weeks. In most cases more than half of the distal stem migration was seen between the 1st and 14th days. In all cases, the stem and socket migrations slowed down gradually and several prosthetic components had become stable after 5 weeks. We conclude that it is essential to perform the index RSA examination on the 1st or 2nd day after surgery and to state when and how weight bearing should be permitted. Otherwise it will be difficult to compare prosthetic migration in various studies and define normative values for migration predicting survival.

Aged↗
PubMed2000

Methods for determining the accuracy of radiostereometric analysis (RSA).

The problem of determining the noise level in any measuring system remains urgent. Radiostereometric analysis (RSA) is a radiographic system of unique accuracy which has applications in areas where minute motions or no motion at all occurs. Examples are micromotion between endoprostheses and bone and in fracture healing. We have determined the accuracy of the RSA system as applied to a clinical series of spinal fusions, where the conditions for RSA were not optimal. Using the usual test-retest methodology on a phantom, we showed that its accuracy can be grossly overestimated in the individual case. We found considerable variations in the accuracy in the individual case, depending on the rigid-body configuration. The overall accuracy, expressed as 3-D "vectors" for rotation and translation, respectively, correlated with the condition number, a method for characterizing the marker configuration. Indeed, the condition number explained as much as 92% of the variation in overall rotation. This condition number, however, cannot be used to analyze the accuracy of one degree of freedom of rotation alone. Mathematical simulation of the accuracy in the individual case of the individual dimension, using in-house software, showed that the accuracy (95% confidence) varied between 0.4 and 4.6 degrees of rotation about the transverse axis, corresponding to a clinical stress series of extension and flexion.

Artifacts↗
PubMed2001

Kinematics after tear in the anterior cruciate ligament: dynamic bilateral radiostereometric studies in 11 patients.

We studied the kinematics of both knees using radiostereometry in 11 patients with unilateral injury of the anterior cruciate ligament and normal contralateral knee. Continuous radiostereometric exposures at a speed of 24 exposures a second were performed, when the patients ascended an 8 cm high platform. The tibial center was more dorsally displaced and the tibia more externally rotated on the injured side. This increasing external tibial rotation was associated with increased anterior displacement of the lateral femoral condyle. The latter also displayed less anterior-posterior translations during continuous extension. The anterior-posterior translation of the medial condyle was about the same as on the uninjured side. Changes in the kinematics of the knee joint due to rupture of the anterior cruciate ligament can result in an abnormal joint load, which may increase the risk of damage to the cartilage and the menisci.

Adolescent↗
PubMed2003

External rotation stress imaging in syndesmotic injuries of the ankle: comparison of lateral radiography and radiostereometry in a cadaveric model.

We compared the value of 7.5 Nm external rotation stress in diagnosing tibiofibular syndesmotic injuries of the ankle on lateral radiographs with radiostereometric analysis (RSA) in 10 cadaveric legs. After sectioning 2 ligaments, RSA showed an increase in posterior translation and external rotation of the fibula. This increase in posterior translation was smaller than the posterior displacement of the fibula on the lateral radiograph, and RSA showed mainly an increase in external rotation of the fibula that can not be measured on conventional radiographs. We conclude that instability of the syndesmosis in cadaveric ankles can be detected with 7.5 Nm external rotation stress RSA, but that external rotation stress lateral radiography is unreliable.

Aged↗
PubMed2003

Insertion of tantalum beads in RSA of the hip: variations in incidence of extra-osseous beads with insertion site.

Radiostereometric analysis (RSA) is a technique that can be used to measure the in-vivo micro-motion of the components of hip arthroplasty. It requires the insertion of tantalum beads into the bone permitting analysis of the radiographs. Extra-osseous beads reduce the usable bead pattern and previous studies have reported their incidence in the proximal femur as between 11% and 13% of all inserted beads. We reviewed the relative incidence of extra-osseous beads by examining 1038 radiographs of 97 patients who were part of an ongoing RSA hip study. Extra-osseous beads were seen in 44% of our patients with most having a single extra-osseous bead. The relative incidence of extra-osseous beads was 2% and 6% in the femur and pelvis, respectively. We observed a reduction in the incidence of the femoral beads with time, but not of the pelvis, which suggests that experience in the insertion technique improves the insertion rates at least of the femur. Our findings indicate that the incidence of extra-osseous beads is lower than previously reported. However, care should be taken in the design of studies to ensure that an adequate number of beads are placed in locations which are both surgically achievable and technically useful.

Arthroplasty, Replacement, Hip↗
PubMed2005

Migration of the acetabular component: effect of cement pressurization and significance of early radiolucency: a randomized 5-year study using radiostereometry.

BACKGROUND: Cementing technique is a crucial factor in prosthesis fixation. No randomized studies have been published, however, comparing the outcome of conventional fingerpacking with the outcome of pressurization of the cement prior to cup insertion. PATIENTS AND METHODS: We randomized 50 THAs to either fingerpacking or sequential pressurization (including individual pressurization of each anchorage hole) and followed the patients with RSA for 5 years. The penetration of cement into the anchorage holes was measured on digital radiographs. Postoperative radiolucent lines around the cup were correlated to later RSA results. For clinical evaluation, we used SF-36 and HHS. RESULTS: The pressurized group of THAs was more stable regarding changes in inclination. We found no other difference in the migratory behavior. The cement penetration into the anchorage holes was deeper with the pressurization technique than with fingerpacking. For the whole group taken together, there was a strong relation between the presence of radiolucent lines as measured on the postoperative radiograph and later migration observed by RSA at 2 and 5 years. INTERPRETATION: Pressurization of the cement produced better cement penetration and increased the cup stability in terms of changes in inclination. Early findings of radiolucent lines can predict later unfavorable cup migration.

Acetabulum↗
PubMed2002

Research for medical photographers: photographic measurement.

Many first degrees in photography or photography-related topics lack a thorough grounding in the photographic sciences. This in turn leads to difficulties for medical photographers who graduate from these courses, when it comes to designing photographic protocols for research projects that will utilize photography as a means of data collection. The concept of the image as subject analogue is introduced and means of visualizing the subject are outlined. The considerations for undertaking photometric, photogrammetric and time-based measurements are given. The variables that need to be controlled in each modality are highlighted and a bibliography is appended so that readers can discover for themselves working examples of the techniques described.

Data Collection↗
PubMedDate not supplied

Eye measurements in 7-year-old black South African children.

BACKGROUND: Ethnic variation often renders anthropometric reference values obtained in one population unsuitable for use in others. Fetal alcohol syndrome (FAS) diagnosis relies in part on the evaluation of certain anthropometric facial features. Measurements of these facial features in South African children have not been compared with measurements obtained in other populations. AIM: The study seeks to determine the suitability of reference values obtained in other populations for the diagnosis of the facial phenotype associated with FAS in South African children. PARTICIPANTS AND METHODS: Palpebral fissure length (PFL), interpupillary distance (IPD), inner canthal distance (ICD) and outer canthal distance (OCD) measured in a group of black South African children were obtained from digital photographs using stereophotogrammetry, and compared with measurements published for other populations. The study population comprised 17 7-year-old boys and 17 7-year-old girls. The precision and reliability of measurements were examined with reference to published data. RESULTS: Eye distance measurements in the study population do not consistently reflect those in any one other population for which such measurements have been published. CONCLUSION: Population-specific reference values of eye distance measurements should be established for South African children.

Anthropometry↗
PubMed1976

An assessment of a stereophotogrammetric technique for the study of facial morphology in the child.

An assessment has been made of a stereophotogrammetric technique (Beard and Burke, 1967) for measuring and contouring the face. Its contouring capabilities depend on the skin surface texture of the subject. Adults have good skin texture and accurate contours can be drawn. Young children cannot be contoured satisfactorily because they lack adequate skin texture, and only linear measurements can be obtained with precision. The disadvantage of incomplete facial coverage was eliminated by using a pair of oblique exposures instead of the conventional frontal exposure. The need for mechanical head positioning was avoided by use of a sighting device incorporated in the system to orientate each exposure to a common datum.

Child↗
PubMedDate not supplied

The adolescent growth spurt in the soft tissues of the face.

The faces of 8 boys and 8 girls were recorded annually by short base stereophotogrammetry. The output for the 16 children consisted of 158 life-size facial maps allowing the serial three-dimensional measurement of 13 soft tissue facial parameters. Three of these parameters (1, 2 and 3) measured the width of the palpebral fissures and the intercanthal distance and were therefore related to the eyes, and 'neural' in character. The remaining 10 parameters (4-13) measured facial characteristics. Standing height was also recorded. The values for each characteristic were age-corrected. Means for the different soft tissue facial parameters are reported for ages 9-16 years. The original individual readings were then three-point smoothed and related first to the year in which peak growth was achieved in standing height, second to the two years preceding and, third, to the two years following that year. The means for the 10 facial parameter growth velocities extending below the eyes showed an adolescent growth spurt related to that in standing height, although not necessarily coinciding with that year. Of the 10 parameters, 5 peaked in PHV year, 3 in -1 PHV year and 2 in +1 PHV year. The facial parameters at eye level, which are really 'neural' parameters, showed much smaller growth velocities and no spurt.

Adolescent↗
PubMedDate not supplied

A serial study of normal facial asymmetry in monozygotic twins.

Asymmetry of the soft tissues of the face was measured by comparing three pairs of bilateral facial parameters connecting the landmarks external canthus, tip of nose and angle of mouth. The subjects were six pairs of monozygotic twins (eight girls and four boys) in the age range 8-19 years. A clinical contour mapping technique known as short-base stereophotogrammetry provided life-size facial maps on which the parameters were measured in three dimensions. The study was based on annual serial records over an average period of 9 years for each pair, and was almost entirely longitudinal. The asymmetry in millimetres was given a positive or negative sign, depending on whether right or left side dominated. Asymmetry in the facial parameters was found to be very small, amounting at most to a few millimetres, and was not much larger than the measuring error of the method. Nevertheless, asymmetry was statistically significant (p < 0.05) in 12 out of 60 indicators, and of these seven were at p < 0.01 level. Asymmetry could not be related to twin zygosity, adolescence or age.

Adolescent↗