Motion of bones and volume changes in the neurocranium after craniectomy in Crouzon's disease. A roentgen stereometric study

Roentgen Stereophotogrammetric Analysis

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.

RSA Applications in Monitoring of Fracture Healing in Clinical Trials

Radiostereometric analysis (RSA) was originally developed as a method for performing highly accurate three-dimensional measurements in vivo over time from sequential radiographs. Since its introduction over twenty years ago, the RSA method has proven itself as a powerful tool with numerous orthopaedic applications. RSA has been used extensively in studies of prosthetic fixation and has been shown to be the method of choice for these studies. RSA has, however, also been successfully applied to a limited number of studies examining fracture healing, namely in fractures of the radius, ankle, tibial plateau, trochanter and femoral neck, as well as studies of bone healing following spinal fusion and tibial osteotomies. RSA follow-up of a fracture will provide definitive demonstration of the exact time of union, i.e. the achievement of fracture stability. This information can be invaluable in randomized clinical trials of fracture treatment. Phantom model studies have proven useful for effective preoperative planning and interpretation of RSA results. The RSA method is a highly accurate, precise and safe objective method for studying fracture healing in clinical trials. The RSA method may serve as a scientific tool to accurately evaluate the significance of supporting novel biomaterials for the early stability and the rate of healing in fractures.

The history and future of radiostereometric analysis

Roentgen stereophotogrammetry allows one to localize the position of an object in space using roentgen rays. For orthopaedic purposes it was developed 35 years ago by Göran Selvik, and since that time many investigators have refined the radiostereometric calculations and evaluative software. Many uses and mathematical algorithms have been developed, and advancements in computer programs and digital radiography continue to expand its capabilities. Despite these advances, improvements in the technical accuracy and type of kinematic analyses possible have been relatively modest. However, radiostereometric analysis is now easier and less time consuming to use, with a resolution in clinical practice almost equal to what could only previously be obtained under ideal laboratory conditions. The ability to measure skeletal and implant movements with high resolution in vivo images was an important progressive step for the orthopaedic community. Radiostereometric analysis has helped develop new fields in clinical orthopaedic research and continues to improve advancements in orthopaedic health care.

Component bone marker displacements revealed by image-corrected cephalometric analysis. A lateral cephalometric study of the cranium in normal and craniosynostosis--an implant study

Displacement of bony component anatomy has not been comprehensively described in human cranial development. In this study, tantalum implants were used to define cranial bone position on serial cephalometric surveys. Image correction (ICCA method) was used to eliminate artifactual shift of component markers before serial analysis was used to define implant movement. In addition, applicable normative standards were used to assess all case presentations. Three normal subjects comprised a normal mixed longitudinal sample aged 2 to 84 months. Two plagiocephaly subjects were studied, one from 6 to 77 months and the other from 16 to 44 months of age. Three syndromic craniosynostosis subjects demonstrated both abnormal and normalized growth following craniotomy, from 14 to 45, from 0.5 to 5.5, and from 2 to 75 months of age. A pattern of backward rotation of cranial component anatomy was observed in three normal subjects and two plagiocephaly subjects. The posterior fossa (PF) showed the greatest growth activity, with displacement adjustments throughout the study, and the anterior cranial fossa (ACF) least growth activity, with imperceptible frontal bone movement after age 3 years. After traditional bifrontal craniotomy, an abnormal displacement growth pattern was observed from age 14 to 45 months in the patient with syndromic craniosynostosis (Pfeiffer syndrome). Extensive fronto-parietal "bossing" and grossly deficient movement in the PF were observed. However, after a bifrontal craniotomy that also crossed lambdoid sutures, a normalized pattern of displacement growth was observed in two Apert syndrome patients. These two patients with extensive syndromic craniosynostosis had cranial component pattern adjustments as in the normal and plagiocephalic subjects.

Crouzon syndrome: cephalometric analysis and evaluation of pathogenesis

Crouzon syndrome is a craniofaciostenosis characterized by brachycephaly, ocular proptosis, and maxillary retrusion. The hypothesis has been forwarded that an alteration in anterior cranial base synchondrosis activity is responsible for the skeleton abnormalities which are associated with this disorder. The present work was aimed at assessing this pathogenetic hypothesis. Cephalometry was used as the analysis method and care was taken in determining the three-dimensional measurements of some functional spaces (e.g., orbit, rhinopharynx, and nasal cavity). The results indicate that in Crouzon syndrome the craniofacial alterations depend not only on reduced synchondrosis activity of the anterior cranial base, but also of the posterior cranial base.

Roentgen stereophotogrammetry. A method for the study of the kinematics of the skeletal system

I have developed a roentgen stereophotogrammetric method for determination of positions of radiopaque markers in an object. The space coordinates are determined in a laboratory coordinate system, which is defined by markers in a test "cage". The markers in the test cage function as calibration points, and are roentgenographed on the same film(s) as the object. Calibration markers and object markers are exposed from two roentgen foci. The cage markers, are in their function, of two kinds, of which one (fiducial marks) is used for projective transformations of the image points to the laboratory coordinate system, while the other (control points) is used for determining the roentgen foci positions in the same coordinate system. After these calculations have been performed, the three-dimensional coordinates of object indicators are determined by crossing of lines between the roentgen foci and the transformed image points. The mathematical principles for the reconstruction of the bundles of rays from the roentgen foci at the moment of exposure are discussed in Chapter 2. Three constructions of test cages, Models 1A and 1B, and Model 2 are also discussed there. In Test Cage Model 1, the two exposures of the object are obtained on one film, but in Model 2 we expose on two films that are perpendicular to each other. The three cage models are, in turn, intended for high-accuracy determinations of lengths (Model 1A), general determinations of space coordinates, especially in larger objects (Model 1B), and high-accuracy determinations of space coordinates in medium-sized objects (Model 1B), and high-accuracy determinations of space coordinates in medium-sized objects (Model 1B). Note, that if the positions of the roentgen foci and the film are not altered, we can roentgenograph the calibration points separately on a film, and then, after removal of the test cage, roentgenograph the object on the same film. The calibration of the test cages is discussed in Chapter 3. To determine coordinates of markers in a plane is easy, if a rectangular coordinatograph is accessible, and we use the same instrument as for the measurements of the films, a Wild Autograph A8. Determination of the position in space of the plate with control points in relation to the plate with fiducial marks requires more consideration. We describe how the degrees of freedom of the plate with control points (translations in x- and y-directions, rotation angle phi about a z-axis), which are difficult to control at construction of the test cages, can be determined by specific calibration procedures.(ABSTRACT TRUNCATED AT 400 WORDS)

Roentgen stereophotogrammetry. Review of orthopedic applications

Roentgen stereophotogrammetry is based on radiographic examinations of calibration cages and object markers implanted in the skeleton. Accurate measurements of radiographs and computer-assisted calculations can provide a three-dimensional motion analysis. Since its introduction 15 years ago, roentgen stereophotogrammetry has found an increasing number of orthopedic applications, which are reviewed here: growth, prosthetic fixation, joint kinematics and stability, fracture stability, and the healing course of spinal fusion and pelvic and tibial osteotomies.

Calvarial growth after linear craniectomy in scaphocephaly as evaluated by X-ray stereophotogrammetry

An roentgen stereophotogrammetric system for the evaluation of skeletal adjustments following corrective surgery in craniosynostosis is described. Four illustrative cases of scaphocephaly, all treated with midline linear craniectomy, with uneventful postoperative follow-up periods of more than 4 years, are reported. The postoperative development, as evaluated by volumetric and kinematic analyses, was uniform but still rich in individual and local growth variations. This study confirms that roentgen stereometry ( = exact measurements from stereoradiographs), being an accurate and objective method, adds greatly to previous methods of postoperative assessment in craniofacial skeletal disorders.

Roentgen stereometry in the study of craniofacial anomalies--the state of the art in Sweden

The paper is a review of ten years' experience with the method for Roentgen Stereophotogrammetric Analysis (RSA) which was presented by Selvik in 1974. The RSA was developed for the study of bone displacement in three dimensions and intended for clinical use. The accuracy of the recordings is about 0.1 degrees for rotations about and 0.05 mm for translations along any one of the three cardinal axes of the head. The method, based on the use of metallic implants, is essentially individual. Some results from our stereometric studies of patients with cleft lip and palate, hemifacial microsomia, craniofacial dysostosis (Crouzon syndrome) and dysgnathia are presented. The recordings concern the direction, the rate, and the amount of articular growth in the craniofacial sutures and the temporomandibular joints (TMJs). The information obtained is thus highly relevant to treatment planning and follow-up in craniofacial anomalies.

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.

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.

Description of a dry skull with Crouzon syndrome

A dry skull from a young adult subject showing the stigmata of Crouzon syndrome was described. All calvarial sutures were prematurely fused. The calvaria was high and pointed in the region of the anterior fontanelle. The cranial base revealed premature fusion of all sutures and of the spheno-petrosal and petro-occipital synchondroses. Furthermore, the internal cranial base showed a number of abnormal morphological traits, especially in the region of the sella turcica. The optic foramina were compressed vertically. Most sutures in the bony orbit were prematurely fused. The orbital cavities were short and their axes deviated laterally. The interorbital distance was increased. Nearly all maxillary sutures were fused and the maxilla was short and narrow, whereas the mandible showed no marked deviations. The molar occlusion was mesial and there was mandibular overjet and bilateral crossbite. The findings were discussed and it was suggested that the involvement of fibrous cartilage may be one of the factors distinguishing the complex forms of craniosynostosis from the simple.