Purpose:
The purpose of this study was to measure biomechanical differences between normal wrist function and wrist function following partial and complete total wrist joint replacement. For a ...comparison, proximal row carpectomy (PRC) was performed as a common wrist reconstructive salvage procedure.
Materials and Methods:
This study utilized cadaveric wrist specimens in a within-specimen analysis. Wrist function was assessed using two measures: (1) kinematic function was quantified using wrist range of motion and axis of rotation measurements and (2) changes in extrinsic flexor and extensor muscle moment arms were quantified using measurements of tendon excursion relative to angular position. All of these measurements were performed for four functional motions: wrist flexion/extension, radial/ulnar deviation, dart thrower's motion (wrist extension, radial deviation to wrist flexion with ulnar deviation), and circumduction. Three treatments were studied: (1) PRC, distal radius hemiarthroplasty (RHA), and (3) total wrist arthroplasty (TWA) (Fig. 1 and Fig. 2).
Results:
Results of this study demonstrated that following PRC there is a significant increase in wrist extension (9.3 ± 5.3°,
p
= 0.018) during the flexion/extension task without changes in wrist flexion or radioulnar deviation. Following the RHA, there were significant measurable changes in wrist motion. Following TWA, there was a significant decrease in flexion of the wrist (12.2 ± 7.0°,
p
= 0.018) compared with the native wrist, with no other significant changes in range motion.
With respect to muscle-tendon unit moment arms, there were no significant changes in muscle moment arms for the major wrist flexor and extensor muscles, suggesting that the center(s) of rotation of the wrist did not change following reconstruction motion procedures in comparison to the normal wrist. The reconstructive procedures were unable to duplicate normal-wrist dart thrower's motion or circumduction (Fig. 3).
Conclusion:
The conclusion of this study is that none of the reconstructive wrist procedures are able to duplicate the normal kinematics of the wrist. However, TWA had the least variability in comparison between specimens tested, and the center(s) of wrist range of motion changed the greatest (distal to proximal location) after PRC.
Fig. 1
Example of experimental set up.
Fig. 2
Schematic of wrist motions to be tested. (A) Abduction/Adduction (B) Flexion/Extension (C) Circumduction (D) Dart thrower's motion (18,19).
Fig. 3
Example specimen of instantaneous helical axis computation during
radial/ulnar deviation
. Solid blue line = trajectory of intact hand. Solid red line = trajectory of hand with TWA. Blue/Green gradient = instantaneous helical axis transition from radial to ulnar deviation. Red/Yellow gradient = instantaneous helical axis transition from radial to ulnar deviation. (A) Dorsal View, PRC (B) Lateral View, PRC (C) Dorsal View, RHA (D) Lateral View, RHA (E) Dorsal View, TWA (F) Lateral View, TWA.
Working memory deficits in normal aging have been well documented, and studies suggest that high memory load plus the presence of distraction negatively impacts successful memory performance to a ...greater degree in older individuals. However, characterization of the component processes that are impaired by these task manipulations is not clear. In this behavioral study, younger and older subjects were tested with a delayed-recognition and recall task in which the encoding and delay period were both manipulated. During the encoding period, the subjects were presented with either a single letter or multiple letters at their predetermined forward letter span, and the delay period was either uninterrupted or interrupted with a visual distraction. There was an age-related impairment of working memory recognition accuracy only in the combination of high memory load and distraction. These results suggest that when working memory maintenance systems are taxed, faulty recognition processes may underlie cognitive aging deficits in healthy older individuals.
Although the prefrontal cortex (PFC) is consistently found to be associated with various working memory processes, the necessity of the PFC for such processes remains unclear. To elucidate PFC ...contributions to storage and rehearsal/maintenance processes engaged during verbal working memory function, we assessed behavior of patients with lesions to the left or right lateral PFC, and neural activity of healthy young subjects during fMRI scanning, during performance of working memory tasks. We found that PFC lesions did not affect storage processes--which is consistent with the notion that posterior cortical networks can support simple retention of information. We also found that PFC lesions did not affect rehearsal/maintenance processes, which was in contrast to our finding that healthy subjects performing a verbal delayed recognition task showed bilateral PFC activation. These combined imaging and behavioral data suggest that working memory rehearsal/maintenance processes may depend on both hemispheres, which may have implications for recovery of function and development of rehabilitation therapies after frontal injury.
Recent studies that identify distinct neural correlates of perceptual awareness offer a promising step towards improved understanding of the neurological underpinnings of conscious experience. Such ...studies indicate that perceptual awareness is modular in nature, with neural correlates of awareness consisting of the specialized structures involved in perceptual processing. However, the integrative, multimodal nature of conscious experience appears to require a functional architecture that overcomes this modular segregation of function. We propose a model in which experience emerges from the dynamic interactions of specialized component processes via a distributed neural network. Such a model offers a mechanism to explain several empirical observations of the neural correlates of perceptual awareness, cognitive function, and symptoms of neurological damage.
Vascularized bone transfer Han, C S; Wood, M B; Bishop, A T ...
Journal of bone and joint surgery. American volume,
1992-December, Letnik:
74, Številka:
10
Journal Article
Recenzirano
We evaluated the results of reconstruction of a skeletal defect with use of a vascularized bone graft from the iliac crest or fibula in 160 patients who had been managed consecutively between 1979 ...and 1989. The indications for the procedure were a skeletal defect including non-union, resulting from resection of a tumor; traumatic bone loss; osteomyelitis; or a congenital anomaly. The average duration of follow-up was forty-two months (range, twelve to 112 months). For the entire series, the rate of union after the primary procedure was 61 per cent and the over-all rate at the latest follow-up examination (including the patients who had a secondary procedure) was 81 per cent. In a subgroup of seventy-six patients who had union after the primary procedure and did not have additional treatment, the average interval until union was six months and the average interval until full activity was sixteen months. The results were more favorable for the patients who had had reconstruction for resection of a tumor (of sixty-nine patients, fifty-six had union), for a congenital anomaly (of six patients, five had union), or for a non-union without infection (of twenty-five patients, twenty-three had union). The results were less satisfactory for patients who had had the reconstruction for bone loss due to osteomyelitis (of sixty patients, forty-six had union). Our data suggest that vascularized bone transfer for the reconstruction of large skeletal defects is a valuable procedure in appropriately selected patients.
Convection that penetrates the tropopause (overshooting convection) rapidly transports air from the lower troposphere to the lower stratosphere, potentially mixing air between the two layers. This ...exchange of air can have a substantial impact on the composition, radiation, and chemistry of the upper troposphere and lower stratosphere (UTLS). In order to improve our understanding of the role convection plays in the transport of trace gases across the tropopause, this study presents a 10 year analysis of overshooting convection for the eastern two thirds of the contiguous United States for March through August of 2004 to 2013 based on radar observations. Echo top altitudes are estimated at hourly intervals using high‐resolution, three‐dimensional, gridded, radar reflectivity fields created by merging observations from available radars in the National Oceanic and Atmospheric Administration Next Generation Weather Radar (NEXRAD) network. Overshooting convection is identified by comparing echo top altitudes with tropopause altitudes derived from the ERA‐Interim reanalysis. It is found that overshooting convection is most common in the central United States, with a weak secondary maximum along the southeast coast. The maximum number of overshooting events occur consistently between 2200 and 0200 UTC. Most overshooting events occur in May, June, and July when convection is deepest and the tropopause altitude is relatively low. Approximately 45% of the analyzed overshooting events (those with echo tops at least 1 km above the tropopause) have echo tops extending above the 380 K level into the stratospheric overworld.
Key Points
A new analysis of NEXRAD radar data shows the spatial and temporal occurrence of tropopause‐overshooting convection over the United States
Ten years of high‐resolution gridded NEXRAD data (GridRad) are now available through the NCAR Research Data Archive
Overshooting convection is most common over the central United States; almost half of observed overshooting events reach 380 K or higher
A series of 166 perilunate dislocations and fracture-dislocations from 7 centers was retrospectively studied. The diagnosis was missed initially in 41 cases (25%). A classification system was ...presented. The perilunate fracture-dislocations were more frequent than the perilunate dislocations at a ratio of two to one. The displacement was dorsal in 161 cases (97%) and palmar in only 5 (3%). The dorsal transscaphoid perilunate fracture-dislocations represented 96% of the dorsal perilunate fracture-dislocations and 61% of the whole series. The clinical and radiologic outcome of 115 perilunate dislocations and fracture-dislocations with at least 1 year and an average of 6 years 3 months of follow-up was studied. Open injury and delay of treatment had an adverse effect on clinical results, whereas anatomical type had less influence. In cases treated early, the clinical results were satisfactory but the incidence of post-traumatic arthritis was high (56%). In the dorsal perilunate dislocation group of pure ligamentous injuries and in the dorsal transscaphoid group, the best radiologic results were observed after open reduction and internal fixation. In the latter group, the fixation of the scaphoid alone was not always sufficient and left occasionally scapholunate dissociation, lunotriquetral dissociation, ulnar translation of the carpus, or other carpal collapse patterns. The initial appraisal of both the osseous and ligamentous pathology was very important.
Parkinson's Disease (PD) leads to poor quality of life and caregiver burden. Mindfulness-based stress reduction (MBSR) may improve these symptoms. We assessed the impact of a 9-week MBSR course on ...people with PD (PwP) and their care partners (CPs).
Participants completed questionnaires at screening, at the end of the course, and at 3-month follow-up: Parkinson's Disease Quality-39 (PDQ-39, PD only), Zarit Burden Inventory (ZBI, CP only) and Mindful Attention Awareness Scale (MAAS, both). The primary outcome measure was change in PDQ-39 (for PwP) or ZBI (for CP). Patient-reported scales were analyzed quantitatively; qualitative data on perceived effectiveness was collected.
53.8% PwP and 100% CPs completed the course. Among PwP, there was a significant reduction in MAAS(p < 0.001) and in PDQ-39 (p = 0.008). CPs experienced an increase in MAAS (p = 0.02) but no change in ZBI (p = 0.239). Qualitatively, both PwP and CPs expressed satisfaction with the course.
MBSR improves mindful awareness in CPs and improves health-related quality of life in PwP.
•Mindfulness based stress reduction is feasible and effective in Parkinson's disease.•MBSR course participation improved participants' mindful awareness and quality of life.•Virtual formats may overcome significant mobility barriers to participation.
The underpricing of private targets Cooney, John W.; Moeller, Thomas; Stegemoller, Mike
Journal of financial economics,
07/2009, Letnik:
93, Številka:
1
Journal Article
Recenzirano
We examine acquisitions of private firms with valuation histories and find a positive relation between acquirer announcement returns and target valuation revisions. Similar to other studies, acquirer ...announcement returns are positive, on average. However, positive acquirer announcement returns are mainly driven by targets that are acquired for more than their prior valuation. This relation is consistent with pricing effects associated with target valuation uncertainty and behavioral biases in negotiation outcomes.
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