Pelvic Tilt Angle Differences Between Symptom-Free Young Subjects and Elderly Patients Scheduled for THA: The Rationale for Tilt-Adjusted Acetabular Cup Implantation.

BACKGROUND: The question whether Pelvic Tilt (PT) angles measured in the supine position are adequate for the alignment of the acetabular cup without an adjustment for anatomical differences between patients is of clinical importance. The aim of this work was to test for factors that can significantly affect PT angles. METHODS: In the present retrospective cohort comparison, the PT angles of 12 Symptom-Free Young Subjects (SFYS) and 45 patients scheduled for Total Hip Arthroplasty (THA) were compared. The data was collected during two studies with the use of a novel smartphone-based navigated ultrasound measurement system. Multi-factorial analysis of variance was run to determine which factors significantly affect PT. RESULTS: Body position (F= 126.65; P< 0.001) and group (SFYS vs. THA patients) (F= 17.52; P< 0.001) had significant main effects on PT. There was also a significant interaction between body position and group (F= 25.59; P< 0.001). The mean PT increased by 8.1° from an interiorly to a neutral tilted position (P< 0.001) and 21.4° from a neutral to a posteriorly tilted position (P< 0.001) with the transition from the supine into the upright position for the SFYS and THA patients, respectively. CONCLUSION: In both groups, PT changed significantly with a transition from the supine to the upright position. A position-dependent mean PT increase in the patient group showed that acetabular cup alignment based on PT in the supine position is not reliable without taking into consideration the inclination of the pelvis in standing position. This may lead to instability and dislocations.

Intra- and Inter-rater Reliability of Navigated Ultrasound in the Assessment of Pelvic Tilt in Symptom-Free Young Adults.

OBJECTIVES: Pelvic tilt is the angle between the anterior pelvic plane and the coronal plane. It affects cup positioning in total hip arthroplasty. The primary objective of this study was to test the intra- and inter-rater reliability of a navigated smart device-based ultrasound system for pelvic tilt assessment. The secondary objective was to test the inter-rater variability of the measurements on a hip phantom. METHODS: A repeated-measures design was used. Two raters measured the pelvic tilt of 12 symptom-free young adults in upright and supine positions. Additionally, pelvic tilt was measured on a hip phantom. Each rater performed 3 measurements in each body position on the participants and 12 measurements on the hip phantom. Intra- and inter-rater reliability were calculated with the use of intraclass correlation coefficients. The variability in measurements on the hip phantom was assessed by a Bland-Altman analysis of agreement. RESULTS: Intraclass correlation coefficient 95% confidence intervals for intra-rater reliability ranged from good to excellent and moderate to excellent for the supine and upright positions respectively. Intraclass correlation coefficient 95% confidence intervals for inter-rater reliability ranged from poor to excellent for both positions. Hip phantom measurements showed no significant average bias (P > .05) and no significant proportional bias (P > .05). The 95% inter-rater limits of agreement were ±1.3° and ±1.7° for the supine and upright positions, respectively. CONCLUSIONS: The intra-rater reliability values achieved were suitable. Intraclass correlation coefficient values for inter-rater reliability remained below an acceptable level. Possible reasons and overcoming strategies were presented. The 95% limits of agreement were good, at less than ±2°.

Preoperative Ultrasonographic Assessment of the Anterior Pelvic Plane for Personalized Total Hip Replacement.

OBJECTIVES: Correct positioning of the acetabular component is a key factor in minimizing the risk of dislocation after total hip replacement (THR) surgery. A "safe" orientation of the cup is usually defined by 2 angles measured between its geometric axis and the anterior pelvic plane. However, in the current state-of-the-art approach to THR surgery, the intraoperative orientation of the anterior pelvic plane cannot be measured. Even less is known about the functional orientation of the pelvis, which determines the postoperative orientation of the cup during the patient's everyday activities. The aim of this article is to present an original approach to personalized THR surgery, in which the necessary measurements are done preoperatively without interfering with the surgical work flow, and the individual orientation of the cup is obtained without navigation using standard tools that are available in the operating room. METHODS: To quantify the effect of the anatomic conditions on the final orientation of the cup, we measured the orientation of the anterior pelvic plane in 43 patients scheduled for THR using a newly developed noninvasive method based on ultrasonography and mobile devices. RESULTS: Our results confirm a large variability of the pelvic orientation in both supine and standing positions. We further show how this variability affects the final position of the cup and discuss its consequences for the patient. Finally, we explore a few practical solutions for individualized cup placement, including our own approach, which is based on tilting of the operating table. CONCLUSIONS: In this work, we show that the common guidelines used today for cup implantation can only be effectively applied to a small portion of the population. In most cases, it is crucial that the orientation of the cup is readjusted for the particular anatomy of the individual patient.

Reliability of an Integrated Ultrasound and Stereophotogrammetric System for Lower Limb Anatomical Characterisation.

BACKGROUND: Lower extremity analysis for preoperative total knee and hip arthroplasty routines can increase surgery success rate and hence reduce associated costs. Current tools are limited by being invasive, limited to supine analysis, or too expensive. This study aimed to propose and validate a device, OrthoPilot®, based on the combined use of a stereophotogrammetric and ultrasound system which can in vivo and noninvasively measure varus/valgus, flexion/extension, femur and tibia torsion, and femur and tibia lengths. METHODS: A phantom was measured by four operators to determine the resolution of the system. Interoperator variability was measured on three operators who measured the above six variables on both legs of three subjects in standing and supine positions. Intraoperator variability was assessed on data from three repeats from 9 subjects (18 legs). RESULTS: All 6 variables were reliably detected on a phantom, with a resolution of 1 mm and 0.5°. Inter- and intraoperator consistency was observed for varus/valgus, flexion/extension, and length measurements on the healthy subjects in standing and supine positions (all ICC > 0.93). For torsion measurements, there was a considerable variation. CONCLUSION: The proposed system, when used on healthy subjects, allowed reliable measurements of key parameters for preoperative procedures in both supine and standing positions. Accuracy testing and further validation on patient populations will be the next step toward its clinical adoption.

Application of Navigated Ultrasound for Assessment of the Anterior Pelvic Plane in Patients With Degenerative Hip Diseases.

OBJECTIVES: Correct positioning of the acetabular cup is the key for successful total-hip replacement. In common clinical practice, the target alignment of the cup is defined with respect to the anterior pelvic plane. In patients with substantial anterior pelvic plane inclination, this condition may lead to inappropriate distribution of the load on the cup, as most of the forces exerted within the hip joint act along the vertical axis. With the known pelvic inclination, it is possible to readjust the position of the cup with respect to the individual posture of the patient. In this work, we present the first clinical evaluation of a new approach to measurement of the pelvic tilt angle using navigated ultrasound. METHODS: In our method, the ultrasound probe is tracked with an optical localizer implemented on a handheld mobile device. The method was tested by taking preoperative measurements from 20 patients with osteoarthritis in standing, sitting, and supine positions. RESULTS: The mean values of the measured angles were consistent with the corresponding results reported by other authors. CONCLUSIONS: Considering the noninvasiveness of the method and affordability of the hardware used in our system, it can be used in preoperative and postoperative measurements of pelvic orientation for supporting surgery planning and evaluation of treatment outcomes.

Bone segmentation applying rigid bone position and triple shadow check method based on RF data.

Noninvasive 3D reconstruction of a bone requires very accurate 2D navigated scans of bone. The use of brightness-mode ultrasound seems to be promising, if some 2D scans of bone are obtained in a fully automatic manner. This paper presents a rapid and fully automatic method for segmenting bone in a standard 2D ultrasound image (B-mode image). The algorithm focuses on segmenting bone in the B-mode image using RF data of the image. The article introduces the signal-processing scheme designed based on RF data to automatically segment bone in the B-mode image. The segmentation accuracy was assessed by performing various tests for this algorithm for various locations of the limbs of the human body. The algorithm was tested for 120 images taken at different locations of limbs of the human body. The sensitivity of these tests was calculated to be 0.99 and specificity was found to be 1. The suggested segmentation approach provides a reliable means of detecting bone in B-mode image.

Pesticide adsorption in relation to soil properties and soil type distribution in regional scale.

Study was focused on the evaluation of pesticide adsorption in soils, as one of the parameters, which are necessary to know when assessing possible groundwater contamination caused by pesticides commonly used in agriculture. Batch sorption tests were performed for 11 selected pesticides and 13 representative soils. The Freundlich equations were used to describe adsorption isotherms. Multiple-linear regressions were used to predict the Freundlich adsorption coefficients from measured soil properties. Resulting functions and a soil map of the Czech Republic were used to generate maps of the coefficient distribution. The multiple linear regressions showed that the K(F) coefficient depended on: (a) combination of OM (organic matter content), pH(KCl) and CEC (cation exchange capacity), or OM, SCS (sorption complex saturation) and salinity (terbuthylazine), (b) combination of OM and pH(KCl), or OM, SCS and salinity (prometryne), (c) combination of OM and pH(KCl), or OM and ρ(z) (metribuzin), (d) combination of OM, CEC and clay content, or clay content, CEC and salinity (hexazinone), (e) combination of OM and pH(KCl), or OM and SCS (metolachlor), (f) OM or combination of OM and CaCO(3) (chlorotoluron), (g) OM (azoxystrobin), (h) combination of OM and pH(KCl) (trifluralin), (i) combination of OM and clay content (fipronil), (j) combination of OM and pH(KCl), or OM, pH(KCl) and CaCO(3) (thiacloprid), (k) combination of OM, pH(KCl) and CEC, or sand content, pH(KCl) and salinity (chlormequat chloride).

Clinical requirements for an ultrasound-based tool navigator for minimally interventional procedures.

BACKGROUND: The past years showed a considerable progress in the development of imaging and navigation systems to support minimal-invasive surgery. However, these methods do not always meet actual clinical requirements of surgeons. They often cause technical and logistic efforts and considerable costs. Purpose of our study was the development of a navigation system relying on simple, familiar and cheaper components. It is based on two-dimensional ultrasound visualization, is quickly applicable to a wide range of minimal-invasive interventions, and is easily to be learned. MATERIAL/METHODS: The imaging system is composed of widely used, well-accepted components and relies only upon conventional two-dimensional sonography using a navigated ultrasound probe, a navigated surgical instrument, and a coordinate tracker, combined with new custom-made navigation software. Accuracy tests were performed, possible error sources were mentioned and the easy and safe handling of this system was demonstrated. RESULTS: Our custom-made software integrates information about the three-dimensional position of an instrument into a two-dimensional ultrasonic image. On-screen navigation aids are offered to reach a sonographically depicted target structure. These navigation aids are easily to be learned and make the use of this system very comfortable. The system shows a mean three-dimensional error of only 0.9+/-0.2 mm. CONCLUSIONS: Our navigation system combines several advantages: as to visualization, it relies solely on the familiar two-dimensional ultrasound image, its use is easy, it is more economic than comparable ultrasound navigation systems, and it can be used in a wide range of minimal-invasive interventions.

Impact of varying soil structure on transport processes in different diagnostic horizons of three soil types.

When soil structure varies in different soil types and the horizons of these soil types, it has a significant impact on water flow and contaminant transport in soils. This paper focuses on the effect of soil structure variations on the transport of pesticides in the soil above the water table. Transport of a pesticide (chlorotoluron) initially applied on soil columns taken from various horizons of three different soil types (Haplic Luvisol, Greyic Phaeozem and Haplic Cambisol) was studied using two scenarios of ponding infiltration. The highest infiltration rate and pesticide mobility were observed for the Bt(1) horizon of Haplic Luvisol that exhibited a well-developed prismatic structure. The lowest infiltration rate was measured for the Bw horizon of Haplic Cambisol, which had a poorly developed soil structure and a low fraction of large capillary pores and gravitational pores. Water infiltration rates were reduced during the experiments by a soil structure breakdown, swelling of clay and/or air entrapped in soil samples. The largest soil structure breakdown and infiltration decrease was observed for the Ap horizon of Haplic Luvisol due to the low aggregate stability of the initially well-aggregated soil. Single-porosity and dual-permeability (with matrix and macropore domains) flow models in HYDRUS-1D were used to estimate soil hydraulic parameters via numerical inversion using data from the first infiltration experiment. A fraction of the macropore domain in the dual-permeability model was estimated using the micro-morphological images. Final soil hydraulic parameters determined using the single-porosity and dual-permeability models were subsequently used to optimize solute transport parameters. To improve numerical inversion results, the two-site sorption model was also applied. Although structural changes observed during the experiment affected water flow and solute transport, the dual-permeability model together with the two-site sorption model proved to be able to approximate experimental data.

Improving surgical precision--application of navigation system in orthopedic surgery.

Navigation systems track objects with precision expressed as root mean square equalling even up to 0.15 mm. Application of navigation system combined with imaging technique makes surgical operations less invasive, which results in the reduced risk of infection, smaller scar and a shorter time of rehabilitation. Imaging techniques allow surgeon to create individual virtual models for virtual surgery planning. Navigation system tracks the positions of surgical tools in relation to the patient's coordinate systems. Medical imaging enables low-invasive surgery, whereas the position of surgical instruments is monitored on screen. The paper presents a newly developed computer-aided surgical system consisting of ultrasonographic probe and tracking system to measure bone geometry, design surgical scenario virtually and follow it intraoperatively. The system assists surgeon to correct bone deformities. The paper presents the results of several accuracy tests, which demonstrate good repeatability and accuracy.

Development of prototype for navigated real-time sonography for the head and neck region.

BACKGROUND: To date, few imaging methods have been established for the head and neck region, in particular for soft tissues, that allow adequate visualization and simultaneously adequate real-time orientation. METHODS: We report a new method using a navigated ultrasound device and a navigated surgical instrument that allows--even in the absence of bony landmarks--appropriate visualization and reliable orientation in real time. RESULTS: The practical applicability of the system was tested. Good handling and acceptance of the system could be shown. The "3-dimensional error" derived from the deviations in all 3 dimensions lies at 0.64 mm. CONCLUSIONS: With this ultrasound-guided navigated procedure, an accurate approach of soft tissue structures with a surgical instrument is possible. Changes of the situs are represented in real time.

A new experimental measurement and planning tool for sonographic-assisted navigation.

In this study, we present a new 2.5-dimensional ultrasonic navigation system for measuring axes, lengths, and torsions preoperatively, intraoperatively, and postoperatively. The system comprises an ultrasound unit with a 5-MHz linear probe (TELEMED Echoblaster 128; Telemed, Vilnius, Lithuania) and a navigation system (OrthoPilot; B. Braun Aesculap, Tuttlingen, Germany) with a Polaris camera (Northern Digital, Waterloo, Canada). Specialized software developed for this application allows for selecting any body region on a virtual 3D skeleton. With a virtual ultrasound probe, planes needed for measurements can be defined. For each section, the respective surface contour of the bone, which is also shown in the ultrasound image, is displayed. Alternatively, the clinician can use established standard sections. Finally, the required length, axes, and torsions are defined. The accuracy and precision of the system were tested using a plastic model. The measurements of length, torsion, and axis values were accurate to -0.1 +/- 0.3 mm (95% CI), 0.1 degree +/- 0.2 degree (95% CI), and 0.0 degree +/- 0.006 degree (95% CI), respectively. The precision variances for length, torsion, and axis were 1.17 mm (standard deviation) and 0.94 degree and 0.66 degree. These results suggest that the new sonographic method is more accurate than conventional radiographic techniques.

Frameless image guidance improves accuracy in three-dimensional interstitial brachytherapy needle placement.

PURPOSE: The aim of this work was to adapt a computer-assisted real-time three-dimensional (3D) navigation system for interstitial brachytherapy procedures. METHODS AND MATERIALS: The 3-D navigation system Surgical Planning and Orientation Computer System (SPOCS; Aesculap, Tuttlingen, Germany) was adapted for use in interstitial brachytherapy. A special needle holder with mounted infrared-emitting diodes (IRED) for 3D navigation-based needle implantation was developed. Measurements were made on a series of different phantoms to study the feasibility and the overall accuracy and precision of the navigation system with regard to single-needle application and volume implants (multiple-needle implantations). In all, 250 single implants and 20 volume implants were performed. Accuracy was measured as the target registration error (TRE) between the preoperatively defined and the achieved target position. RESULTS: Analyses of the 250 different targets showed a mean TRE for single-needle applications of 1.1 mm (SD +/- 0.4 mm), 0.9 mm (SD +/- 0.3 mm), and 0.7 mm (SD +/- 0.3 mm) in the x, y, and z direction, respectively. The maximal deviation was 2.3 mm. The corresponding TRE in the x, y, and z direction for volume implants was 1.6 mm (SD +/- 0.4 mm), 1.9 mm (SD +/- 0.6 mm), and 1.0 mm (SD +/- 0.4 mm), respectively. The maximum deviation was 2.9 mm. CONCLUSIONS: The adaptation of a commercially available surgical planning and navigation system to interstitial brachytherapy is feasible. It enables virtual planning and improved accuracy in 3D interstitial needle implantation.