Estimating polyethylene wear in total hip arthroplasty by using computed tomography and alternative RSA techniques

Introduction: Traditionally Total Hip Arthroplasty (THA) components performance, and in particular the performance of the polyethylene liner, is evaluated in 2D by examining plain radiographs or in 3D using Radio Stereo-metric Analysis (RSA). While 2D techniques require only a plain radiograph, they are less accurate. RSA systems, on the other hand, are more accurate but are more complicated to set up and require dedicated equipment. CT scanners are widely available and can measure THA performance in 3D. These techniques fail to estimate wear when tantalum cups are implanted, and alternative methods are needed. Specific Aims: Validate a Computerized Tomography (CT) technique for evaluating THA wear, develop and test algorithms to estimate wear in THA when tantalum cups are implanted. Methods: To validate the 3D CT data and software, a supine hip phantom fitted with a 3-axis micrometer tower was scanned, first (as a feasibilty study) in an experimental ultra-high resolution flat panel CT scanner and then in a multi-detector CT scanner. The micrometers were displaced in the x, y, and z axes, displacement of the micrometers (femoral head) was estimated and then compared to the actual micrometer readings (studies I and II). Wear was also estimated from clinical CT data of patients that had their THA revised: images were analyzed and compared to a coordinate measurement machine (CMM) and a micrometer (study III). For the analysis of liner wear when tantalum cups are used, four methods were tested: standard RSA, Model Based RSA, RSA-Helical axis, and RSA Center of Rotation. To test these methods a supine hip phantom was used and the femur was abducted. The center of the femoral head was calculated using these four methods (Study IV). Results: Study I - Measuring femoral head displacement using a phantom in the high resolution flat panel CT scanner, the mean difference between the actual micrometer displacement and the CT readings was found to be -0.14±0.12 mm (-0.06 to -0.21 mm 95% CI). In study II, similar to study I, a hip phantom was placed in a multi-detector CT and the femoral head displacement was compared between readings from CT data and the actual micrometers displacement. The mean accuracy and precision for the individual axis x, y, and z was 0.159±0.056 mm, 0.113±0.029 mm, and 0.209±0.036 mm respectively, with combined accuracy of 0.285 mm. In study III, we compared CT wear measurement to the actual wear of the same retrieved implant. Ex-planted liners were measured using CMM and micrometer, the average differences and standard deviations were: CMM-CT 0.09±0.29mm, CMM-Micrometer 0.01±0.32, and micrometer-CT 0.11±0.44. In study IV, comparing alternative techniques of calculating femoral head center when tantalum cups are used, the 2D average head-cup distance was calculated by: standard RSA 0.41mm, Model Based RSA 0.38mm, RSA RSA-HAT 0.96mm, and RSA-COR 1.41mm. Conclusion: Under ideal conditions, with no soft tissue or motion artifacts, and with a highresolution flat panel scanner it is possible to record femoral head penetration to a clinicaly acceptable level.When considering the clinical application of current CT technology and measurement techniques, the expected wear measurement accuracy should be 0.3 mm. In cases where CT technology does not provide an adequate solution for wear measurement (when tantalum cups are implanted), model based RSA provides the closest agreement to gold standard RSA and should be considered as a viable solution for wear measurement

Ambulatory measurement of knee motion and physical activity: preliminary evaluation of a smart activity monitor

BACKGROUND: There is currently a paucity of devices available for continuous, long-term monitoring of human joint motion. Non-invasive, inexpensive devices capable of recording human activity and joint motion have many applications for medical research. Such a device could be used to quantify range of motion outside the gait laboratory. The purpose of this study was to test the accuracy of the modified Intelligent Device for Energy Expenditure and Activity (IDEEA) in measuring knee flexion angles, to detect different physical activities, and to quantify how often healthy subjects use deep knee flexion in the ambulatory setting. METHODS: We compared Biomotion Laboratory (BML) "gold standard" data to simultaneous IDEEA measures of knee motion and gait, step up/down, and stair descent in 5 healthy subjects. In addition, we used a series of choreographed physical activities outside the BML to confirm the IDEEA's ability to accurately measure 7 commonly-performed physical activities. Subjects then continued data collection during ordinary activities outside the gait laboratory. RESULTS: Pooled correlations between the BML and IDEEA knee flexion angles were .97 +/- .03 for step up/down, .98 +/- .02 for stair descent, and .98 +/- .01 for gait. In the BML protocol, the IDEEA accurately identified gait, but was less accurate in identifying step up/down and stair descent. During sampling outside the BML, the IDEEA accurately detected walking, running, stair ascent, stair descent, standing, lying, and sitting. On average, subjects flexed their knees >120° for 0.17% of their data collection periods outside the BML. CONCLUSION: The modified IDEEA system is a useful clinical tool for evaluating knee motion and multiple physical activities in the ambulatory setting. These five healthy subjects rarely flexed their knees >120°

Analysis of finger motion coordination during packaging interactions

Packaging accessibility is a significant problem for many older people. Whilst the majority of studies have focused on issues surrounding strength, work has shown that dexterity required to open a pack is also a major issue for many older people. Hence, the work undertaken here, reports a quantitative study that aimed to analyse motion coordination patterns across digits 2–5 (index to little finger) during interactions with three of the most common types of packaging: plastic bottles, jars, and crisps packets, and comparing those interactions to a common measure of dexterity, the Perdue Pegboard. Ten subjects (6 males and 4 females) were examined while reaching forward to grasp and open a 300ml plastic bottle and a 500g jar. A ten-camera opto-electronic motion capture system measured trajectories of 25 miniature reflective markers placed on the dorsal surface landmarks of the hand. Joint angular profiles for 12 involved flexion–extension movements were derived from the measured coordinates of surface markers. The results showed that finger correlations vary widely across the differing pack formats with the crisps having the lowest finger movement correlation and the jar having the highest. Speed and jerk metrics were also seen to vary across the various pack formats. However, finger correlations were seen to be more relevant to perceived dexterity of pack opening than finger speeds and jerk motions

Tai Chi and vestibular rehabilitation improve vestibulopathic gait via different neuromuscular mechanisms: Preliminary report

BACKGROUND: Vestibular rehabilitation (VR) is a well-accepted exercise program intended to remedy balance impairment caused by damage to the peripheral vestibular system. Alternative therapies, such as Tai Chi (TC), have recently gained popularity as a treatment for balance impairment. Although VR and TC can benefit people with vestibulopathy, the degree to which gait improvements may be related to neuromuscular adaptations of the lower extremities for the two different therapies are unknown. METHODS: We examined the relationship between lower extremity neuromuscular function and trunk control in 36 older adults with vestibulopathy, randomized to 10 weeks of either VR or TC exercise. Time-distance measures (gait speed, step length, stance duration and step width), lower extremity sagittal plane mechanical energy expenditures (MEE), and trunk sagittal and frontal plane kinematics (peak and range of linear and angular velocity), were measured. RESULTS: Although gait time-distance measures were improved in both groups following treatment, no significant between-groups differences were observed for the MEE and trunk kinematic measures. Significant within groups changes, however, were observed. The TC group significantly increased ankle MEE contribution and decreased hip MEE contribution to total leg MEE, while no significant changes were found within the VR group. The TC group exhibited a positive relationship between change in leg MEE and change in trunk velocity peak and range, while the VR group exhibited a negative relationship. CONCLUSION: Gait function improved in both groups consistent with expectations of the interventions. Differences in each group's response to therapy appear to suggest that improved gait function may be due to different neuromuscular adaptations resulting from the different interventions. The TC group's improvements were associated with reorganized lower extremity neuromuscular patterns, which appear to promote a faster gait and reduced excessive hip compensation. The VR group's improvements, however, were not the result of lower extremity neuromuscular pattern changes. Lower-extremity MEE increases corresponded to attenuated forward trunk linear and angular movement in the VR group, suggesting better control of upper body motion to minimize loss of balance. These data support a growing body of evidence that Tai Chi may be a valuable complementary treatment for vestibular disorders

Identification of Novel Notch Target Genes in Breast Cancer

Notch signaling plays a key role in development, tissue homeostasis, and cancer. High expression levels of Notch signaling components are associated with aggressive disease and poor patient prognosis in breast cancer. Mesenchymal‐epithelial transition factor (MET) is a receptor tyrosine kinase with an established prognostic significance correlating with poor disease outcome in breast cancer patients as a result of high metastatic rate. We performed expression array analysis to identify candidate Notch target genes; we identified and validated MET as a target of NOTCH1 signaling in breast cancer. We found that NOTCH1 knockdown significantly reduces MET promoter activity, as well as expression levels of MET transcript and protein. The mechanism of NOTCH1 regulation of MET expression will be the focus of future work. To further identify candidate target genes of NOTCH1 signaling, we generated and validated a NOTCH1 antibody for use in chromatin immunoprecipitation experiments.MAS