[en] 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. (Auth.)

[en] The effect on bone growth of two locally given, different, unfractionated radiation doses (0.1 and 24 Gy) was tested in a rabbit litter aged 57 days. The effects on growth were registered with roentgen stereophotogrammetric length measurements for 75 days after irradiation. Growth of the right irradiated tibia was compared with the growth of the left non-irradiated tibia. After 7 to 9 days, 24 Gy had caused a linear fall in growth to about 15 per cent. After a period of complete cessation, a slight growth was registered. 0.1 Gy had no significant growth retarding effect. (author)

[en] Model experiments and tests on 2 patients were performed to probe the feasibility of roentgen stereophotogrammetry for evaluating variations in shape and volume of the liver. The surface of the object was marked with indicators, and the three-dimensional marker coordinates were determined. The model experiments demonstrate a good correlation between true volume and the volumes defined by the indicators, and also demonstrate the possibility of localizing an expansivity. The variability of the volume of a polyhedron defined by 15 liver indicators with stage of breathing is discussed. (Auth.)

[en] 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

[en] The spatial location of points in an object can be determined by roentgen stereophotogrammetry. A technique of high accuracy was applied in a determination of the daily skeletal growth of young rabbits. The tibia was labelled with tantalum markers on each side of the growth zones, and the increasing distance between these markers due to longitudinal bone growth was measured. Three different types of markers were tested, and the methodologic error was estimated. It varied between 30 and 43 μm for one growth interval, depending on the type of marker used. The method has clinical implications currently under investigation. (Auth.)

[en] Using a roentgen stereophotogrammetric method, the three-dimensional movements in the sacroiliac joints were quantified in 4 patients. To provoke motion of the sacrum, changes between body positions and a test with manual pressure were used. In tests with symmetric forces on the sacrum, it in most cases rotated mainly about a transverse axis and at most approximately 2⁰. The axis of rotation passed through the iliac bones mainly in the lower part of the iliac tuberosity. The rotations between the iliac bones and the sacrum about any of the three main axes were determined with a precision in the mean of 0.2⁰. The distance between the two superior posterior iliac spines varied at most 0.4 mm between seven different body positions. (Auth.)

[en] Soon after Roentgen's discovery, the 'new' rays were used to produce stereoscopic images or used for spatial reconstruction of positions of foreign bodies. However, no systematic use of roentgen stereo measurements seems to have occurred until the 1970's, although many attempts have been made before. Since 1972, a system for roentgen stereophotogrammetry has been in use at the University Hospital in Lund. The system has been named RSA, roentgen stereophotogrammetric analysis. It is a complete system, including instrumentation for implanting tantalum landmarks, devices for calibration of the stereo roentgen set-up, and comprehensive software. Using different calibration set-ups, any part of the body can be investigated under different conditions using standard roentgen equipment. The computer programs make it possible to calculate spatial landmark coordinates from measured film coordinates, and further to calculate growth, and volume changes or kinematic variables in well-defined and generally used terms. After the basic principles have been established, a survey of applications grouped according to anatomic regions follows. Special emphasis is laid on total hip and knee replacement, which besides complex craniofacial and spinal disorders are the most rewarding fields of study. (orig.)

[en] A method for in vivo determination of orientation and relation in space of components of total hip prosthesis is described. The method allows for determination of the orientation of the prosthetic components in well defined anatomic planes of the body. Furthermore the range of free motion from neutral position to the point of contact between the edge of the acetabular opening and the neck of the femoral component can be determined in various directions. To assess the accuracy of the calculations a phantom prosthesis was studied in nine different positions and the measurements of the space oriented parameters according to the present method correlated to measurements of the same parameters according to Selvik's stereophotogrammetric method. Good correlation ws found. The role of prosthetic malpositioning and component interaction evaluated with the present method in the development of prosthetic loosening and displacement is discussed. (orig.)

[en] Different degrees of artificial L5-S1 spondylolisthesis were created using a lumbar specimen. Lateral radiographs were obtained of each, with the specimen tilted and/or rotated. The true spondylolisthesis was determined stereophotogrammetrically. The slip, measured on the radiographs, was calculated according to two methods modified from BOXALL et coll. (2). No significant difference in accuracy was found between these two methods. The difference in calculated slip between examinations needs to be at least 20 per cent of the sagittal length of L5 to be regarded as a true progression. A true progress of slip of less than 20 per cent is difficult to detect with statistical certainty. (orig.)

[en] A comparison of two- and three-dimensional methods for the determination of the orientation of total hip prostheses was made in a group of 57 patients. The acetabular inclination and the collum-diaphyseal angle measured on a.p. projections (2-D) were adequate in most cases for assessing how vertically the prostetic component was inserted, but in individual cases with a high degree of version these measurements could be misleading. Anteversion measured in the transverse plane (2-D) was more sensitive to errors than planar anteversion measured as a rotation around the longest diameter of the ellipsoid projection of the acetabular opening, but it gave a rough estimate of the relation of the prostetic components. Determination of the spatial (3-D) orientation of the components provides a precise estimate of the component relations. (orig.)