Biomedical subjects
Publications and source records attributed to G Selvik.
Roentgen stereophotogrammetric analysis was used in the evaluation of subsidence in eight noncemented femoral components of the HP-Garches prosthesis. After 2 years, seven components had subsided 0.6-3.9 mm, i.e., more than observed in some cemented prostheses. No distinct symptoms related to the micromotion appeared.
Micromotion of the tibial component of eight Freeman-Samuelson arthroplasties without cement for gonarthrosis were followed for two years and studied by roentgen-stereophotogrammetric analysis (RSA). In five cases, displacement over time was studied, and in all cases migration was found to range from 0.7 to 4.8 mm after two years. One tibial component migrated continuously during the period studied, while the remaining prostheses migrated mostly during the first six months. The direction of the migration was erratic. Inducible displacement ranging from 0.8 to 5.0 mm was found in all cases. Clinically, all of the patients were scored as successful although one with continuous migration had the lowest score. This degree of micromotion is compatible with good results after two years, and appears to be a characteristic of the immediate interlocking fixation used in the Freeman-Samuelson prosthesis.
Micromotion of the tibial component in 27 knee arthroplasties for gonarthrosis, three of which were regarded as failures for reasons other than mechanical loosening, was studied using high-resolution roentgen stereophotogrammetric analysis (RSA). Migration over time was found in all cases, ranging from 0.2 to 2.1 mm. The majority of the cases showed migration during the first year only, while a minority migrated continuously during the period studied. The latter group showed more migration even after 1 year. All cases showed inducible displacement in response to external forces, ranging from 0.2 to 1.0 mm. The micromotion correlated with the age of the patient but not with other demographic parameters. Alignment or component position did not correlate with the micromotion. All cases but one had developed a radiolucent zone, and it was concluded that the micromotion occurred in the soft tissue interface between bone and cement. Such micromotion is a normal finding in cemented tibial components in knee arthroplasty.
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.
Displacement of the mandible 2-2 1/2 years after oblique sliding osteotomy of the mandibular rami is reported. Stability of the osteotomy site has been assumed to be complete much earlier, however. In the present stereo radiographic study mobility at the osteotomy site was recorded as late as 2 years after surgery. No sign of delayed healing was recorded in the plain radiographic examination. It seems possible that relapse after oblique sliding osteotomy continues as long as the functional matrix can influence an unstable osteotomy site. As plain radiography does not give full information on the quality of bone, the stability of the osteotomy site can not be assessed by this method.
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In 7 adult volunteers, a roentgen stereophotogrammetric technique was used to analyze the tibiofibular relationship during active unloaded movements of the ankle. The greatest movements were observed during plantar to dorsiflexion with an average widening of the ankle mortise of 1.0 mm and an average dorsal translation of the fibula of 0.9 mm. No significant rotation of the fibula could be revealed.
A prospective randomized study was performed comparing immediate and late weight bearing in 53 dislocated bimalleolar and trimalleolar fractures. Using cerlage, staples, and pins (Cedell 1967), an exact reconstruction of the ankle mortise was achieved in 41/53 ankles. At follow-up after 3 and 6 months, the two groups were equal regarding clinical results. Evaluation radiographically and by roentgen stereophotogrammetric analysis (Selvik 1974) indicated that the stability of the ankle mortise was sufficient to allow early postoperative weight bearing.
Sixteen patients were examined by roentgen stereophotogrammetry during the first year after total hip arthroplasty. Eight prostheses were fixed with low-viscosity and eight with high-viscosity cement. Eight acetabular components, four in each group, migrated cranially, and three femoral components, all in the low-viscosity group, migrated distally. Our findings suggest that low-viscosity cement does not improve prosthetic fixation.
Kinematic studies of the rheumatoid knee joint with the aid of roentgen stereophotogrammetry were performed in 4 patients (6 knees). Three kinds of experiments were carried out. The screw axis of rotation between various flexion angles was determined. The displacement of the screw axis indicated pathological function in all cases. Using different treatment techniques the effect of traction was studied. A separation between the femur and the tibia of 1.3-3.8 mm was found in 3 knees which were slightly flexed during the traction. The compression effect of isometric knee extension was determined in 4 knees. Compression of 0.5 mm at a medial point and of 0.3 mm at a lateral point of the femoral condyle were found in one knee. The present study indicates that roentgen stereophotogrammetric analysis may give additional information on the development of internal derangement of the rheumatoid knee joint.
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.
In an earlier study (Rosenquist et al., 1985) on oblique sliding osteotomy in 14 patients, operative repositioning and postoperative displacement of the mandible during intermaxillary fixation were presented. In the present stereometric study on the same patients displacement of the mandible after removal of the intermaxillary fixation is presented. A continuous anterior and a minor initial cranial translation and an anterior rotation of the mandible were found. Proclination of both upper and lower incisors was recorded. Correlations were found between operative repositioning and postoperative displacement of the mandible after removal of the intermaxillary fixation. Possible relapse mechanisms are discussed.
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.
Twenty patients were examined by standard radiography and roentgen stereophotogrammetric analysis (RSA) during a two-year period after total hip arthroplasty. Eleven of the acetabular components migrated cranially and three femoral components migrated distally. This migration was most rapid during the first four months after operation. Our findings support the possibility that mechanical loosening is initiated by thermal injury during polymerisation of the cement; the less frequent migration of the metallic femoral component compared with the polyethylene acetabular component may be because the metal acts as a heat sink. Standard radiographs were inadequate for assessment of early mechanical loosening, whereas RSA could reveal migration within four months of the arthroplasty.
A prospective randomized investigation of early versus late weight bearing in 46 patients with fracture of the lateral malleolus was performed. In 43/46 patients an exact operative reconstruction of the ankle mortise could be achieved using pins, staples and cerclage (Cedell, 1967). Radiographic and stereophotogrammetric analysis of the ankles after 3 months showed no significant differences, nor did the clinical follow-up.
Using roentgen stereophotogrammetric analysis (RSA), the integrity of the bond between the tibial component and the tibia was studied in seven knees, implanted with a cemented Kinematic total knee prosthesis for gonarthrosis. Migration ranging from 0.3 to 1.9 mm over a two-year period occurred in all seven cases. Displacement, induced by external forces, ranging from 0.2 to 1.0 mm was observed in five cases. Measurable migration and inducible displacement may be the rule rather than an exception in total knee arthroplasty (TKA). Accordingly, absolute rigid fixation would not be necessary for successful function of a TKA.
The postnatal development of the cranial vault is reviewed with special emphasis upon the rabbit in respect to longitudinal, volumetric, and kinematic growth. Also, the calvarial growth relative to long bone growth is discussed. The cranial vault suture is a multifunctional syndesmosis with variable structure and a rich variability of local behavior.
Knowledge of normal suture development is vital to the understanding of aberrant suture growth. The purpose of the present investigation was to comprehensively analyze the complete growth period of the calvarium in rabbits, thus including increment beyond maturity (20 weeks). 5 male New Zealand white rabbits were studied from age 14 d until cessation of cranial growth using roentgen stereophotogrammetry. Growth at the coronal and sagittal sutures seemed completed at 8 months of age, while the frontonasal suture still exhibited minute expansion at the end of the observation period (13 months). Coronal suture growth decelerated linearly relative to the frontonasal suture. Bone separation at the sagittal suture varied less with age as compared to that of the transverse sutures. A brief period of growth reduction, pertaining to all cranial vault sutures, during the second interval (d 35-42) corresponded well with cessation of weaning. Balanced growth fluctuations were frequent. Spatial alterations correlated well with longitudinal increments as to growth arrest. Changes of rotational direction during active growth as well as, in some cases, widespread variations between individuals demonstrated the flexibility of angular calvarial development. In conclusion, the registered growth activity beyond maturity craves consideration during the evaluation of experimental changes of sutural growth so as not to disregard compensatory adjustments.