Računalniška sistema za opredeljevanje porazdelitve tlaka na kolčni sklepni površini

Background. In this work, we describe the computer systems Viprecox and ActiveContours that are used in the process of realistic estimation of some biomechanical parameters of the hip joint, including the maximal value of the stress in the hip joint p max. The computer system Active Contours uses standard anteroposterior radiographs of the whole pelvis and both hips for itscalculations and Viprecox in its kernel uses a relatively simple three-dimensional mathematical model of stress distribution in the hip-joint articular surface which has been extensively elsewhere (e.g. Iglič 1996). Material and methods. Both state-of-the-art computer systems were tested by analysing the calculated values of p max for 81 patients (37 males and 44 females). Conclusions. In this way we prove that the described computer systems can be used for the determination of the contact stress distribution from standard AP radiographs.Izhodišča. V delu sta opisana računalniška sistema Viprecox in Active Contours, ki ju uporabljamo v procesu ocenjevanja nekaterih biomehanskih parametrov kolčnega sklepa vključno z največjo vrednostjo tlaka v kolčnem sklepu p max. Raunalniški sistem Active Contours za svoje izračune uporablja standardne antero-posteriorne rentgenograme cele medicine in obeh kolkov. Aplikacija Viprecox v svojem jedru uporablja relativno enostaven tridimenzionalen matematični model porazdelitve tlaka na kolčni sklepni površini, ki je podrobno predstavljen drugje (npr. Iglič 1996). Material in metode. Oba računalniška sistema smo preizkusili tako, da smo analizirali izračunane vrednosti p max za 81 bolnikov (37 moških in 44 žensk). Zaključki. Pokazali smo, da sta opisana sistema uporabna pri določanju porazdelitve kolčnega sklepnega tlaka iz standardnih anteroposteriornih AP rentgenogramov

Variation of Pelvic Diameters Due to Different Scanning Positions – The Experimental Study

The distortion of human pelvis X ray scans, due to different scanning positions, can cause huge mistakes in estimation of pelvic diameters. The aim of the study was to quantify distortion of pelvic diameters in relation to scanning inclination angles. Twenty anatomically defined spots on the pelvis of a young male cadaver, freed of soft tissues, were marked with 3 mm metal balls. The digitalized X-ray scans were made with seven different but similar inclination angles, and marked spots were recognized by computer software. Obstetrical-gynecological (Ob-Gyn), horizontal and vertical diameters were measured between marked spots, and percentages of distortion were calculated for each new scanning position. Twenty seven distances on human pelvis from seven X-ray scans varied from –35.9% to 28.3%, on average 0.47%. This study has pointed to a high variation of vertical pelvic dimensions (4.94±5.73%), consequently making them unreliable in the estimation of general pelvic shape, and low variation of horizontal dimensions (0.92±0.61%). Generally, the percentage of variation of pelvic dimensions highly increases with inclination angle, in frontal and sagital plane. Alteration of scanning distance by 4 cm has a weak influence on pelvic diameters. The most reliable Ob-Gyn pelvic diameter was conjugata diagonalis, then diameters obliqua prima and secunda, with an average length deviations of 3.4, 4.0, and 6.0% respectively. The conjugata anatomica was themost unreliable with an average variation of 11.5%

Attribute Interactions in Medical Data Analysis

There is much empirical evidence about the success of naive Bayesian classification (NBC) in medical applications of attribute-based machine learning. NBC assumes conditional independence between attributes. In classification, such classifiers sum up the pieces of class-related evidence from individual attributes, independently of other attributes. The performance, however, deteriorates significantly when the “interactions” between attributes become critical. We propose an approach to handling attribute interactions within the framework of “voting” classifiers, such as NBC. We propose an operational test for detecting interactions in learning data and a procedure that takes the detected interactions into account while learning. This approach induces a structuring of the domain of attributes, it may lead to improved classifier’s performance and may provide useful novel information for the domain expert when interpreting the results of learning. We report on its application in data analysis and model construction for the prediction of clinical outcome in hip arthroplasty

Cluster Analyses of Association of Weather, Daily Factors and Emergent Medical Conditions

The goal of this study was to evaluate associations between the meteorological conditions and the number of emergency cases for five distinctive causes of dispatch groups reported to SOS dispatch centre in Uppsala, Sweden. Center’s responsibility include alerting to 17 ambulances in whole Uppsala County, area of 8,209 km² with around 320,000 inhabitants representing the target patient group. Source of the medical data for this study is the database of dispatch data for the year of 2009, while the metrological data have been provided from Uppsala University Department of Earth Sciences yearly weather report. Medical and meteorological data were summoned into the unified data space where each point represents a day with its weather parameters and dispatch cause group cardinality. DBSCAN data mining algorithm was implemented to five distinctive groups of dispatch causes after the data spaces have gone through the variance adjustment and the principal component analyses. As the result, several point clusters were discovered in each of the examined data spaces indicating the distinctive conditions regarding the weather and daily cardinality of the dispatch cause, as well as the associations between these two. Most interesting finding is that specific type of winter weather formed a cluster only around the days with the high count of breathing difficulties, while one of the summer weather clusters made similar association with the days with low number of cases. Findings were confirmed by confidence level estimation based on signal to noise ratio for the observed data points

Variations of Femoral Condyle Shape

The aim of this study is to mathematically approximate the shape of the femoral articulating line and compare radiuses of condylar curves within and between males and females. Ten male and ten female participants were included in the study. Radiuses of medial and lateral condylar curves were calculated from the side view knee X-ray by original mathematical equation. Average radiuses of condylar curves were between 4.5 and 1.7 cm medially, and between 3.2 and 1.8 cm laterally, for 0° and 90° flexion contact point respectively. Males had longer curve radiuses of both condyles (p<0.05). Differences turned out to be statistically insignificant after adjusting to body height. Even small changes in the joint geometry during lifetime could make a joint susceptible to osteoarthritis or injuries. Approximation of the radiuses of femoral condyle curves is a useful method in anthropometric, radiological and virtual calculations of the knee geometry, and other ellipsoidal structures in human body, like wrist, scull segments, dental arches, etc

Biomechanical and Clinical Alterations of the Hip Joint Following Femoral Neck Fracture and Implantation of Bipolar Hip Endoprosthesis

The implantation of a bipolar partial hip endoprosthesis is a treatment of choice for displaced medial femoral neck fracture. We present an experimental study which asses and compare biomechanical and clinical status through period before and after hip fracture and implantation of bipolar partial hip endoprosthesis. This study encompassed 75 patients who suffered from an acute medial femoral neck fracture and were treated with the implantation of a bipolar partial hip endoprosthesis. Their biomechanical status (stress distribution on the hip joint weight bearing area) and clinical status (Harris Hip Score) were estimated for the time prior to the injury and assessed at the follow-up examination that was, on average, carried out 40 months after the operation. Despite ageing, the observed Harris Hip Score at the follow-up examination was higher than that estimated prior to the injury (77.9>69.6; p=0.006). Similarly, the hip stress distribution was reduced (2.7 MPa<2.3 MPa; p=0.001). While this reduction can be attributed to a loss of weight due to late ageing, the principal improvement came from the operative treatment and corresponding restoration of the biomechanical properties of the hip joint. The implantation of a bipolar partial hip endoprosthesis for patients with displaced medial femoral neck fractures improves the biomechanical and clinical features of the hip, what should have on mind during making decision about treatment

Morphometric Alteration of Femoral Condyles Due to Knee Osteoarthritis

Aim of this study was to estimate how knee osteoarthritis (OA) affects the shape of femoral condyles by comparing the radiuses of condylar curves between healthy and OA knees. Seventeen female and five male patients with established diagnosis of knee OA were included in the study. Radiuses of medial and lateral condylar curves were calculated from the side view knee X-ray by original mathematical equation and compared to referent values of healthy knees, after adjusting to body height. The average radiuses of condylar curves were between 52.6 ± 6.2 and 17.6 ± 3.5 mm medially, and between 43.3 ± 8.4 and 15.4 ± 3.7 mm laterally, for 0° and 90° femoral flexion contact points, respectively. The OA knees had longer curve radiuses medially and laterally at 0°, 10°, and 20° femoral flexion contact points in comparison to the healthy sample (P<0.001; t-test). Our results suggest that the shape of the femoral condyles in OA knees is changed. It should be aware not only in researching of OA etiology, but also in designing of knee endoprostheses, in a manner to achieve better individual sizing