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Biomedical subjects

G Selvik

Publications and source records attributed to G Selvik.

At least 73 records · Page 4Linked to original sources
PubMed1985

Volumetric changes in the developing rabbit calvarium.

Tantalum bone markers were implanted in the frontal, parietal, and temporal bones, at least two in each bone segment, in seven male New Zealand white rabbits. Roentgen stereophotogrammetric analyses were performed for regular intervals between ages 30 to 142 days. With the exception of a few implants in the temporal bone, bone markers remained stable during the observation period. Volumetric and longitudinal growth data were compared. Calvarial polyhedron volumes increased linearly. Growth at the actual neurocranial sutures demonstrated an individually fluctuating pace. No obvious correlation between volumetric and longitudinal growth was noted. This might be explained by sagittal and temporal suture growth in periods being close to the methodological error and failure to document bone rotations. Previous observations on the linearity in cerebral weight increase during corresponding periods of time points to the decisive role of neural mass growth in calvarial development in rabbits. Suture growth characteristics are discussed.

Animals↗
PubMed1985

Analytical stereophotogrammetric determination of three-dimensional knee-joint geometry.

An analytical stereophotogrammetric method is introduced to measure the three-dimensional geometry of articular surfaces in vitro. Information of this kind is particularly useful for mathematical joint models and anthropological studies. The method requires no specific equipment, such as a stereocomparator, contrarily to other techniques reported (e.g. Ghosh, 1983) and is relatively simple and inexpensive. The background of the method is outlined in the present paper, and results of accuracy and precision tests are presented. It is shown that an accuracy on the order of 0.2 mm (95% confidence interval) is well feasible in actual knee-joint evaluations, if the measuring procedure is conducted carefully. The method is illustrated by measuring and comparing the articular surface geometries of a bilateral pair of knee joints.

Biomechanical Phenomena↗
PubMed1985

Displacement of the mandible during intermaxillary fixation after oblique sliding osteotomy. A stereometric and cephalometric radiographic study.

The X-ray stereometric method was applied for the first time to a series of consecutive patients to record operative repositioning of the mandible during oblique sliding osteotomy and postoperative displacement of the mandible during intermaxillary fixation. Comparison with cephalometric measurements was presented. The operative repositioning pattern was presented. Postoperatively a posterior displacement pattern was found with incisor extrusion in both jaws. Correlation between operative repositioning and postoperative displacement and between the two measurement methods was assessed. The stereometric method offers information on displacement on all three planes and a higher degree of accuracy. To avoid incisor extrusion, besides intermaxillary dental fiscation also skeletal fixation is recommended.

Adolescent↗
PubMed1985

Definition of endoprosthetic loosening. Comparison of arthrography, scintigraphy and roentgen stereophotogrammetry in prosthetic hips.

Contrast arthrography, radionuclide arthrography, scintigraphy and roentgen stereophotogrammetric analysis (RSA) were used to detect mechanical loosening in 14 painful total hip replacements. All prosthetic components unstable by RSA, or with abnormal arthrogram, or with increased scintigraphic activity, or loose at revision were migrating, but no non-migrating components demonstrated any of these signs of loosening. Our findings indicate that mechanical loosening should be defined as migration.

Contrast Media↗
PubMed1984

Instability, migration and laxity of total hip prostheses. A roentgen stereophotogrammetric study.

Roentgen stereophotogrammetric analysis was used in the evaluation of clinical and/or radiographic problems in 28 total hip replacements without suspicion of infection. Instability of the acetabular and/or the femoral component was revealed in 14 cases. In 21 cases, examined twice, migration of the acetabular component was found in eight cases and migration of the femoral component in 15 cases. The method allows instability and migration of the prosthetic components as well as joint laxity to be determined with a high degree of accuracy.

Acetabulum↗
PubMed1984

Instability of total hip prostheses at rotational stress. A roentgen stereophotogrammetric study.

Roentgen stereophotogrammetric analysis (RSA) has been carried out on 24 total hip prostheses (24 patients), which were all painful at weightbearing. The examinations were made with the hip at distraction, compression, external and internal rotation. One acetabular component showed instability only at distraction-compression and one showed instability only at rotation. Four femoral components showed instability at distraction-compression and at rotation, six only at rotation, but none showed instability only at distraction-compression. Thus rotational provocation demonstrated instability in all unstable femoral components; rotational stress must be of importance in mechanical loosening of the femoral component.

Acetabulum↗
PubMed1984

Roentgen stereophotogrammetric analysis of neurocranial suturectomy in rabbits.

This investigation was conducted to further elucidate both the significance of a calvarial suture and the compensatory ability of the cranial vault. Four-week-old male New Zealand White rabbits were subjected to unilateral or bilateral extirpation of the coronal suture after insertion of metallic markers, and were then followed regularly by roentgen stereophotogrammetry until age 21 weeks. Bilateral extirpation of the normal coronal suture resulted in a dramatically increased initial rate of bone separation, which tended to remain supranormal for the rest of the investigation. Unilateral suturectomy showed differences in growth between the sides, the operated side initially separating significantly more than the other. Volumetric calvarial growth in rabbits with unilateral extirpation terminated similar to that in control animals, while volumes in rabbits with bilateral extirpations constantly exceeded control volumes, finally exceeding these by 65%. Responses at intact sutures confirmed the compensatory capacity of cranial vaults. The results indicate that the passive longitudinal and volumetric cranial vault bone growth responds quickly to growth disturbances, thereby demonstrating its plasticity, and that the neurocranial suture is a restraining and modulating component in cranial growth.

Animals↗
PubMed1984

Roentgen stereophotogrammetric analysis of restricted periods of neurocranial suture immobilization in rabbits.

The effect of temporary fusion of sutures on craniofacial growth was studied biometrically in 4-week-old male New Zealand White rabbits. Tantalum bone markers were implanted in the cranial vault, and the coronal suture immobilized with isobutyl-2-cyanoacrylate adhesive. Linear craniectomy was performed after 2 or 6 weeks of sutural growth restriction (four animals in each group). The animals were followed for approximately 17 weeks. Early craniectomy resulted in greatly increased coronal suture bone separation (175% of control growth rates in peers and 125% of maximal control rates). Growth after late craniectomy showed an age-dependent lower rate, but still the overshoot markedly surpassed controls (210% of control rates in peers and 65% of maximal control growth rates). Overall, both exhibited overcompensation in coronal suture growth. A rapid compensation of adjacent sutures to temporary growth restriction and a tendency toward spontaneous correction following release of growth inhibition were demonstrated. Thus, the total anteroposterior growth of the combined frontonasal and coronal sutures nearly equaled that of control animals. Following linear craniectomy, volumetric calvarial expansion increased considerably in both early and late groups, due to compensatory coronal suture growth, but probably due also to spatial bone rearrangements. Based upon the findings, the length of the suture immobilization period seems critical to longitudinal and volumetric growth as well as to subsequent compensatory activity after surgical correction.

Animals↗
PubMed1984

Longitudinal growth rate of the distal tibia and fibula in children.

In 61 children (30 boys and 31 girls), the growth rates in the distal tibia and fibula were recorded by use of a roentgen stereophotogrammetric technique. The average observation time was about one year and seven months. The growth rates were correlated with chronologic and skeletal age. Adjusting for skeletal age did not significantly change the average growth rates or the scattering of the values. The mean growth rate and the remaining growth from about nine years of age in the boys and eight years of age in the girls were calculated for separate age groups. In the distal tibia in the boys and the girls, the average growth rate decreases from a plateau of about 11 and ten years of age, respectively. Decreasing growth rates were found somewhat later in the distal tibia than in the distal fibula in both the boys and the girls. The growth rates were close to zero at about the same time in the distal tibia and fibula in both sexes. In determining the remaining growth, the large biologic variability indicates the importance of serial measurements on the individual patient. The individual growth charts, together with clinical and radiographic estimation of maturity, provide a guideline for treatment of a patient with growth disturbance of the distal tibia and fibula.

Adolescent↗
PubMed1984

Mobility of the pubic symphysis. In vivo measurements with an electromechanic method and a roentgen stereophotogrammetric method.

Mobility of the pubic symphysis can be measured in vivo by two new methods. One is electromechanic (EM), with steel pins inserted into the bone. The other is roentgen stereophotogrammetric analysis (RSA), with tantalum bone markers implanted into the hip bones. With the first method, movements are directly registered with resistive transducers mounted on the pins. With the second method, movements are deduced with kinematic analysis from roentgen stereophotogrammetric measurements of the positions of the bone markers. Both methods have high precision, about 0.1 mm for translations and 0.1 degrees for rotations. The methods were used in two young volunteers, a man and a woman. In provocative tests with identical loading (alternating, active straight-leg raising in the supine position and standing on alternating left or right leg) there was a good correlation between the two methods. The measured values, i.e., translations of up to 2 mm and rotations of up to 3 degrees, form a basis for more comprehensive studies of normal and pathologic mobility of the pubic symphysis.

Adult↗
PubMed1984

Changes in tibiofibular relationships due to growth disturbances after ankle fractures in children.

We analyzed the longitudinal growth of the distal tibial and fibular physes and the longitudinal displacement of the distal metaphysis and epiphysis of the fibula relative to the distal metaphysis and epiphysis of the tibia during growth using a roentgenstereophotogrammetric technique in eight children: six with a traumatic growth disturbance in one or both of the distal tibial and distal fibular physes and two with a normal ankle. In the normal ankles the distal fibular metaphysis moved distally in relation to the distal tibial metaphysis and the growth in the distal fibular physis was slower than that in the distal tibial physis. Growth arrest in the distal fibular physis and continued growth in the distal tibial physis resulted in distal displacement of the fibular metaphysis relative to the tibial metaphysis, probably due to traction on the distal ligaments of the fibula or more rapid growth in the proximal fibular physis than in the proximal tibial physis, or both. Valgus deformity of the ankle developed when the growth of the distal tibial physis exceeded the distal sliding of the fibula, as shown by the stereophotogrammetric analyses and orthoroentgenograms. Growth arrest in the distal tibial physis and continued growth in the distal fibular physis resulted in proximal sliding of the fibula, as shown by the roentgenstereophotogrammetric analyses and serial orthoroentgenograms. This mechanism compensated to some extent for the overgrowth of the fibula. Simultaneous growth arrest in both the distal tibial and the distal fibular physis was associated with movement of the distal end of the fibula in a distal direction relative to the tibia, probably due to the more rapid growth in the proximal fibular physis than in the proximal tibial growth plate. Therefore, growth arrest of the distal tibial or fibular physis may result in either proximal or distal sliding of the fibular metaphysis in relation to the tibial metaphysis. Probably growth arrest in the distal fibular physis has a less favorable prognosis than arrest in the distal tibial physis, because after tibial arrest proximal sliding of the fibula may compensate for overgrowth of the fibula better than distal sliding of the fibula can compensate for fibular arrest and overgrowth of the tibia.

Adolescent↗
PubMed1983

Kinematics of cranial vault growth in rabbits.

To characterize mathematically the spatial rearrangement of cranial vault bones of the rabbit during growth, a longitudinal study was undertaken from age 4-20 weeks. Initially, at least three nonlinear tantalum bone markers were implanted in the parietal, frontal, and the combined nasal bones. Thereafter, the animals were followed regularly with roentgen stereophotogrammetrical analysis. The parietal bones were found to rotate laterally upward (3 degrees), while the frontal bones rotated downward (2 degrees) relative to their contralaterals. The frontal bones rotated rostrally upward (12 degrees) and outward (3 degrees) as well as laterally downward (5 degrees) in relation to the parietal bones. Due to the morphology of the rabbit head, the examination positioning used in this study, and the direction of the growth process, growth at the coronal suture correlated fairly well with longitudinal axis translations; but the growth at the frontonasal suture relative to the frontal bones was directed about 45 degrees downward. This points to the importance of the bone-marker positioning, so that their connecting line is directed along the axis of growth. Also, this approach makes it possible to obtain new information on the development and treatment of craniofacial aberrations.

Animals↗
PubMed1983

Roentgen stereometry with the aid of metallic implants in hemifacial microsomia.

Displacement of the mandible and the maxilla with growth in relationship to the frontal bone was recorded in eleven children with hemifacial microsomia, aged 3 to 14 years at the initial examination. The goals were to assess the efficiency of the method for accurate recording of articular growth and to obtain information on facial development in each of these children. Correction of the skeletal asymmetry was not attempted during observation periods of from 707 to 1,484 days. In continued observations three of the children were treated with functional appliances. Roentgen stereometry with the aid of metallic implants proved to be an efficient method for highly accurate recordings of articular facial growth in relationship to the frontal bone. Displacement of the jaws was asymmetrical in all of the examined children as determined in the frontal and transverse planes of the head. In about 50 percent of the children the degree of asymmetry increased in one plane while it decreased in the other plane. No correlation was found between the extent of the mandibular deformity, as seen on orthopantomograms, and the displacements of the mandible. Generally, the displacement of the maxillary bones corresponded with the displacement of the mandible. Articular growth of the jaws was redirected toward a more favorable pattern in two of the children during the time they used a functional appliance. In the third child the use of a functional appliance had no such effect.

Activator Appliances↗
PubMed1983

Pattern of growth retardation after Blount stapling: a roentgen stereophotogrammetric analysis.

The roentgen stereophotogrammetric method has been used in 19 children treated by Blount stapling for progressive leg length discrepancy. The growth plates of distal femur and/or proximal tibia were stapled with a total of 31 growth regions stapled. Longitudinal growth rate of 25 intact growth regions of distal femur and proximal tibia was determined and correlated well to growth rates as derived from growth tables of Green and Anderson and Kember and Sissons. In stapled growth regions, a uniform pattern of growth retardation was found and correlated well to skeletal age: the more advanced the skeletal age at time of stapling, the more pronounced and rapid initial growth retardation and the lower basal growth rate. Significant asymmetric growth was registered in 5 of 31 stapled growth regions, especially in three patients who developed loosening of staples. In five patients the staple tip motion was analyzed. Widening of staples and staple tip movements within the bony epiphysis and metaphysis were small. In the skeletally younger cases the widening and tip movement were more pronounced than in the older cases. In summary, the roentgen stereophotogrammetric method was used in order to analyze pre- and postoperative growth pattern and was found valuable in checking growth rates after Blount stapling to detect early complications such as asymmetric growth and loosening of staples. Furthermore, the movements and the deformation of the staples by the growth process could be evaluated with high precision.

Adolescent↗
PubMed1983

Roentgen stereophotogrammetric analysis of growth at cranial value sutures in the rabbit.

Biometric characterization of rabbit cranial vault bone separation was attempted to further elucidate sutural growth mechanisms. The internasal and frontonasal sutures, connected to the facial skeleton, were also investigated. 17 male New Zealand white rabbits were studied from age 4 to 21 weeks using roentgen stereophotogrammetry with tantalum implants. A uniform cranial growth pattern with successively decreasing rates was observed, as were different growth rates at the neurocranial bones relative to those of the facial skeleton. Anteroposterior length increase was due mainly to bone separation at the frontonasal suture. Growth at the sagittal suture was minimal. Minor rate fluctuations and compensatory rebounds after periods of reduced growth were continuously observable. Small left-right differences within each individual were registered. Oscillations in growth rate across adjacent sutural areas and occasional negative growth values imply that bone separation at sutures demonstrates an alternating pattern of translations and rotations. The experimental data demonstrated the plasticity and variability of normal cranial vault growth.

Animals↗
PubMed1983

A roentgen stereophotogrammetric system. Construction, calibration and technical accuracy.

The principles for a system of roentgen stereophotogrammetric analysis for experimental and clinical applications are presented. Only the positions of implanted reference markers in the investigated object are measured. Tantalum balls, 0.5 or 0.8 mm in diameter, are used as reference markers. Standard roentgen equipment, permitting simultaneous exposure from two roentgen tubes, is employed. The calibration equipment, a glass calibration cage containing radiopaque markers, introduces a rectangular laboratory coordinate system in the roentgen investigation. The calibration of the calibration equipment itself and the obtained methodologic accuracy in determining distances, volumes and movement parameters is described for various film/screen and marker combinations.

Animals↗