The thumb carpometacarpal (CMC) joint is often affected by osteoarthritis--a mechanically mediated disease. Pathomechanics of the CMC joint, however, are not thoroughly understood due to a paucity of in vivo data. We documented normal, in vivo CMC joint kinematics during isometric functional tasks. We hypothesized there would be motion of the CMC joint during these tasks and that this motion would differ with sex and age group. We also sought to determine whether the rotations at the CMC joint were coupled and whether the trapezium moved with respect to the third metacarpal. Forty-six asymptomatic subjects were CT-scanned in a neutral position and during three functional tasks (key pinch, jar grasp, jar twist), in an unloaded and a loaded position. Kinematics of the first metacarpal, third metacarpal, and the trapezium were then computed. Significant motion was identified in the CMC joint during all tasks. Sex did not have an effect on CMC joint kinematics. Motion patterns differed with age group, but these differences were not systematic across the tasks. Rotation at the CMC joint was generally coupled and posture of the trapezium relative to the third metacarpal changed significantly with thumb position. The healthy CMC joint is relatively stable during key pinch, jar grasp, and jar twist tasks, despite sex and age group. Our findings indicate that directionally coupled motion patterns in the CMC joint, which lead to a specific loading profile, are similar in men and women. These patterns, in addition to other, nonkinematic influences, especially in the female population, may contribute to the pathomechanics of the osteoarthritic joint.
BackgroundRecent data indicate that chronic low-level exposure to lead is associated with accelerated declines in cognition in older age, but this has not been examined in women.ObjectiveWe examined biomarkers of lead exposure in relation to performance on a battery of cognitive tests among older women.MethodsPatella and tibia bone lead—measures of cumulative exposure over many years—and blood lead, a measure of recent exposure, were assessed in 587 women 47–74 years of age. We assessed their cognitive function 5 years later using validated telephone interviews.ResultsMean ± SD lead levels in tibia, patella, and blood were 10.5 ± 9.7 μg/g bone, 12.6 ± 11.6 μg/g bone, and 2.9 ± 1.9 μg/dL, respectively, consistent with community-level exposures. In multivariable-adjusted analyses of all cognitive tests combined, levels of all three lead biomarkers were associated with worse cognitive performance. The association between bone lead and letter fluency score differed dramatically from the other bone lead-cognitive score associations, and exclusion of this particular score from the combined analyses strengthened the associations between bone lead and cognitive performance. Results were statistically significant only for tibia lead: one SD increase in tibia lead corresponded to a 0.051-unit lower standardized summary cognitive score (95% confidence interval: −0.099 to −0.003; p = 0.04), similar to the difference in cognitive scores we observed between women who were 3 years apart in age.ConclusionsThese findings suggest that cumulative exposure to lead, even at low levels experienced in community settings, may have adverse consequences for women’s cognition in older age.
ISEE-355 Abstract: Decreased heart rate variability (HRV), a marker of poor cardiac autonomic function, has been associated with sudden cardiac death and heart failure. Several observational studies have shown a significantly decreased vagal tone in workers occupationally exposed to lead, compared with non-exposed controls. However, no study has been conducted to evaluate the effects of non-occupational lead exposure on HRV in the general population. A number of studies have shown that diabetes is associated with reduced HRV, and thus diabetics may represent a more vulnerable subpopulation. The purpose of this study was to examine the relationship between alterations in HRV, low-level lead exposure, and diabetes in a large group of community residents. We examined the association of low-level lead exposure with HRV measures among 385 male participants (mean age 73) from the Normative Aging Study. We used K-x-ray fluorescence to measure bone lead levels, and graphite furnace atomic absorption spectroscopy to measure blood lead levels. HRV variables included the standard deviation of normal-to-normal (NN) intervals, the square root of the mean of the squared differences between adjacent NN intervals, power in high (HF, 0.15 to 0.40 Hz) and low frequency (LF, 0.04 to 0.15 Hz), and LF/HF ratio, reflecting sympathovagal balance. Log 10 transformed HRV measures were used as response variables. Diabetes mellitus was defined as fasting blood glucose levels greater than 126 mg/dL and/or physician-diagnosed diabetes (n=77, 20%). After controlling for potential confounders (age, diastolic blood pressure, fasting blood glucose, cigarette smoking, serum cholesterol, and use of angiotensin converting enzyme inhibitor), no lead biomarker was associated with HRVs in the entire cohort. However, stratified analyses showed that an interquartile increase in patella lead (20 micro gram/gram) was associated with a 22.8% increase (95% confidence interval (CI), −4.5% to 78.9%) of the LF/HF ratio in diabetics, and a 7.4% decrease (95% CI, +18.3% to 4.8%) in non-diabetics. The difference in effect between diabetics and non-diabetics was significant (p=0.04 for interaction term). The associations with tibia lead were similar to those with patella lead, but less significant. Blood lead levels were not associated with any of the HRV measures examined. The results suggest that diabetics may be a population that is particularly susceptible to cardiovascular damage by low-level lead exposure, mainly explained by an altered balance of the parasympathetic and sympathetic nerve activities.
ISEE-599 Objective: Our recent study has shown that cumulative exposure to lead was associated with depression of electrocardiographic conduction, such as QT interval. This study examined whether iron metabolism genes [hemochromatosis gene (HFE), transferrin (Tf), heme oxygenase-1 (HMOX1)] modify the effects of lead on QT interval in 613 community-dwelling older men. Materials and Methods: We used K-x-ray fluorescence and graphite furnace atomic absorption spectrometry to measure bone lead and blood lead levels, respectively. Standard resting 12-lead electrocardiograms were taken at the same time as subjects' bone and blood lead measurements. Multiplex polymerase chain reaction assay was used for HFE and Tf genotyping. Length of (GT)n repeats in HMOX1 was analyzed using microsatellite polymorphisms. Results: Of the 613 subjects, 216 (35.2%) and 192 (31.3%) persons carried HFE (C282Y and H63D) and Tf C2 variants, respectively. Seventy four (12.1%) subjects had long (≥33 GT) alleles. A 10 mg/g increase in tibia lead levels was associated with 5.2 ms [95% confidence interval (CI), 1.2–9.2 ms] and 8.5 ms (95% CI, 2.8–14.2 ms) increases in the QT intervals among persons with HFE variants and long HMOX1 alleles, respectively, but had no effect in persons with the wild-type genotype and short and middle alleles. However, the difference in effect of tibia lead was not statistically significant (P for interaction=0.16 for HFE; 0.13 for HMOX1). When we stratified by the number of those 3 gene variants [none (n=237) vs. 1 (n=276) vs. 2 + (n=100)], we observed graded, significant increases in the QT interval in association with tibia lead (P for trend <0.01) and blood lead (P for trend=0.04) as the number of the gene variants increased. Conclusions: Gene variants related to iron metabolism increased the impacts of cumulative lead exposure on the prolonged QT interval.
The use of biplanar videoradiography technology has become increasingly popular for evaluating joint function in vivo. Two fundamentally different methods are currently employed to reconstruct 3D bone motions captured using this technology. Marker-based tracking requires at least three radio-opaque markers to be implanted in the bone of interest. Markerless tracking makes use of algorithms designed to match 3D bone shapes to biplanar videoradiography data. In order to reliably quantify in vivo bone motion, the systematic error of these tracking techniques should be evaluated. Herein, we present new markerless tracking software that makes use of modern GPU technology, describe a versatile method for quantifying the systematic error of a biplanar videoradiography motion capture system using independent gold standard instrumentation, and evaluate the systematic error of the W.M. Keck XROMM Facility’s biplanar videoradiography system using both marker-based and markerless tracking algorithms under static and dynamic motion conditions. A polycarbonate flag embedded with 12 radio-opaque markers was used to evaluate the systematic error of the marker-based tracking algorithm. Three human cadaveric bones (distal femur, distal radius, and distal ulna) were used to evaluate the systematic error of the markerless tracking algorithm. The systematic error was evaluated by comparing motions to independent gold standard instrumentation. Static motions were compared to high accuracy linear and rotary stages while dynamic motions were compared to a high accuracy angular displacement transducer. Marker-based tracking was shown to effectively track motion to within 0.1 mm and 0.1 deg under static and dynamic conditions. Furthermore, the presented results indicate that markerless tracking can be used to effectively track rapid bone motions to within 0.15 deg for the distal aspects of the femur, radius, and ulna. Both marker-based and markerless tracking techniques were in excellent agreement with the gold standard instrumentation for both static and dynamic testing protocols. Future research will employ these techniques to quantify in vivo joint motion for high-speed upper and lower extremity impacts such as jumping, landing, and hammering.
Abstract Background Challenges with any therapeutic program for children include the level of the child's engagement or adherence. Capitalizing on one of the primary learning avenues of children, play, the approach described in this article is to develop therapeutic toy and game controllers that require specific and repetitive joint movements to trigger toy/game activation. Objective The goal of this study was to evaluate a specially designed wrist flexion and extension play controller in a cohort of children with upper extremity motor impairments (UEMIs). The aim was to understand the relationship among controller play activity, measures of wrist and forearm range of motion (ROM) and spasticity, and ratings of fun and difficulty. Design This was a cross-sectional study of 21 children (12 male, 9 female; 4–12 years of age) with UEMIs. Methods All children participated in a structured in-clinic play session during which measurements of spasticity and ROM were collected. The children were fitted with the controller and played with 2 toys and 2 computer games for 5 minutes each. Wrist flexion and extension motion during play was recorded and analyzed. In addition, children rated the fun and difficulty of play. Results Flexion and extension goal movements were repeatedly achieved by children during the play session at an average frequency of 0.27 Hz. At this frequency, 15 minutes of play per day would result in approximately 1,700 targeted joint motions per week. Play activity was associated with ROM measures, specifically supination, but toy perception ratings of enjoyment and difficulty were not correlated with clinical measures. Limitations The reported results may not be representative of children with more severe UEMIs. Conclusions These outcomes indicate that the therapeutic controllers elicited repetitive goal movements and were adaptable, enjoyable, and challenging for children of varying ages and UEMIs.
The importance of anatomic reconstruction of the proximal humerus on shoulder biomechanics and kinematics after anatomic total shoulder replacement (aTSR) has been highlighted by a number of investigations. The humeral head designs of current-generation shoulder arthroplasty emphasize either anatomic or soft-tissue balancing total shoulder arthroplasty (sbTSR) philosophies. The purpose of this study was to compare the postoperative anatomy of TSR systems used to treat primary glenohumeral osteoarthritis.This was a matched cohort study of 60 patients treated with either press-fit aTSR or sbTSR by two shoulder surgeons. The analysis of postoperative true AP radiographs was performed to calculate multiple representative anatomic parameters of the TSR.A significant difference was observed in the average measurements between the sbTSR and aTSR designs about the humeral head center offset (5.2 ± 0.4 mm versus 3.9 ± 0.3 mm; P = 0.02), implant-humeral shaft angle (0.3 ± 0.3 varus versus 1.7 ± 0.3 valgus, P < 0.001), and humeral head to tuberosity height (8.8 ± 0.4 mm versus 6.2 ± 0.4, P < 0.001), respectively. No significant difference was observed in the average measurements between the two systems' designs regarding the head-shaft angle (133.4° ± 0.8° versus 135.0° ± 1.0°, P = 0.16) and the relation of humeral head to lateral humeral cortex (0.15 ± 0.6 mm inside the lateral cortex versus 0.19 ± 0.6 outside the lateral cortex; P = 0.69), respectively.Despite differing design philosophies of these systems, and some notable differences, the absolute differences between the measured anatomic parameters were small and not likely clinically relevant. Anatomic and soft-tissue balancing humeral arthroplasty implants can both reliably reconstruct proximal humeral anatomy.
The relations of nutritional factors to lead accumulation in the body were examined cross-sectionally among 747 men aged 49-93 years (mean 67 years) in the Normative Aging Study in 1991-1995. Means (standard deviations) for blood lead, tibia lead, and patella lead were 6.2 (4.1) microg/dl, 21.9 (13.3) microg/g, and 32.0 (19.5) microg/g, respectively. In multiple regression models adjusting for age, education level, smoking, and alcohol consumption, men in the lowest quintile of total dietary intake levels of vitamin D (including vitamin supplements) (<179 i.u./day) had mean tibia and patella lead levels 5.6 microg/g and 6.0 microg/g higher than men with intake in the highest quintile (> or =589 i.u./day). Higher calcium intake was associated with lower bone lead levels, but this relation became insignificant when adjustment was made for vitamin D. The authors also observed inverse associations of blood lead levels with total dietary intake of vitamin C and iron. When analyses were controlled for patella lead, age, smoking, and alcohol consumption, men in the lowest vitamin C intake quintile (<109 mg/day) had a mean blood lead level 1.7 microg/dl higher than men in the highest quintile (> or =339 mg/day), while men in the lowest iron intake quintile (<10.9 mg/day) had a mean blood lead level 1.1 microg/dl higher than men in the highest quintile (> or =23.5 mg/day). This study suggests that low dietary intake of vitamin D may increase lead accumulation in bones, while lower dietary intake of vitamin C and iron may increase lead levels in the blood.
