Browsing by Author "Wang, Kevin"
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Item Open Access Diagnosis-Related Group-Based Payments for Adult Spine Deformity Surgery Significantly Vary across Centers: Results from a Multicenter Prospective Cohort Study.(World neurosurgery, 2023-03) Yeramaneni, Samrat; Wang, Kevin; Gum, Jeffrey; Line, Breton; Jain, Amit; Kebaish, Khaled; Shaffrey, Christopher; Smith, Justin S; Lafage, Virginie; Schwab, Frank; Passias, Peter; Hamilton, D Kojo; Klineberg, Eric; Ames, Christopher; Burton, Douglas; Bess, Shay; Hostin, RichardBackground
To investigate the variation in total episode-of-care (EOC) payment and quality-adjusted life-year (QALY) gain for complex adult spine deformity surgeries in the United States, adjusting for case type and surgeon preferences.Methods
Patients aged >18 years with adult spine deformity with Medicare Severity-Diagnosis-Related Groups (DRGs) 453-460 and a minimum of 2 years of follow-up from index surgery were included. Index and total payments were calculated using Medicare's Inpatient Prospective Payment System. All costs were adjusted for inflation to 2020 U.S. dollar values. QALYs gained were calculated using baseline, 1-year, and 2-year Short-Form 6D scores. Mixed-effect models were used to estimate the proportion of variation in total EOC payment and QALY gain.Results
A total of 330/543 patients from 6 sites were included. Mean age was 62.4 ± 11.9 years, 79% were women, and 92% were white. The mean index and total EOC payment were $77,302 and $93,182, respectively. Patients gained on average 0.15 QALY (P < 0.0001) 2 years after surgery. In unadjusted analysis, 39% of the variation in total EOC payment across the 6 centers was attributable to relative weight of DRG and base rate. Adjusting for patient and procedural factors increased the proportion of variation in total EOC payments across the centers to 56%. Less than 2% of the variation in QALY gain was observed across the 6 centers.Conclusions
Medicare-based payments for complex spine deformity fusions are primarily driven by relative weight of the DRG and the hospital's base rate. Patient and procedural factors are unaccounted for in the DRG-based payments made to the providers.Item Open Access Dissimilar cavitation dynamics and damage patterns produced by parallel fiber alignment to the stone surface in holmium:yttrium aluminum garnet laser lithotripsy.(Physics of fluids (Woodbury, N.Y. : 1994), 2023-03) Xiang, Gaoming; Li, Daiwei; Chen, Junqin; Mishra, Arpit; Sankin, Georgy; Zhao, Xuning; Tang, Yuqi; Wang, Kevin; Yao, Junjie; Zhong, PeiRecent studies indicate that cavitation may play a vital role in laser lithotripsy. However, the underlying bubble dynamics and associated damage mechanisms are largely unknown. In this study, we use ultra-high-speed shadowgraph imaging, hydrophone measurements, three-dimensional passive cavitation mapping (3D-PCM), and phantom test to investigate the transient dynamics of vapor bubbles induced by a holmium:yttrium aluminum garnet laser and their correlation with solid damage. We vary the standoff distance (SD) between the fiber tip and solid boundary under parallel fiber alignment and observe several distinctive features in bubble dynamics. First, long pulsed laser irradiation and solid boundary interaction create an elongated "pear-shaped" bubble that collapses asymmetrically and forms multiple jets in sequence. Second, unlike nanosecond laser-induced cavitation bubbles, jet impact on solid boundary generates negligible pressure transients and causes no direct damage. A non-circular toroidal bubble forms, particularly following the primary and secondary bubble collapses at SD = 1.0 and 3.0 mm, respectively. We observe three intensified bubble collapses with strong shock wave emissions: the intensified bubble collapse by shock wave, the ensuing reflected shock wave from the solid boundary, and self-intensified collapse of an inverted "triangle-shaped" or "horseshoe-shaped" bubble. Third, high-speed shadowgraph imaging and 3D-PCM confirm that the shock origins from the distinctive bubble collapse form either two discrete spots or a "smiling-face" shape. The spatial collapse pattern is consistent with the similar BegoStone surface damage, suggesting that the shockwave emissions during the intensified asymmetric collapse of the pear-shaped bubble are decisive for the solid damage.Item Open Access Market Valuation of Patent Characteristics(2013-04-16) Wang, KevinMeasuring the returns to R&D has been an endeavor pursued by economists with vast interest in an effort to learn more about the characteristics of successful R&D. This paper empirically measures the market valuation of firms using patent statistics as a proxy for the success of R&D. It finds that self-citation and generality patent measures are largely insignificant likely due to a tendency for newer patents to be measured incorrectly. It also attempts a measure of companies’ reputation for innovation for valuation and proposes a new method of quantification. Lastly, it finds that the market valuation of R&D investment is potentially myopic during years of stock market downturns.