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Leslie N. Sutton, David Barranco, Joel Greenberg, Stephen Dante, Sandra Florin and Frank Welsh

✓ The relationship between cerebral blood flow (CBF) and cerebral metabolic rate of glucose (CMR gl) in the white matter was studied in a plasma infusion model of vasogenic edema in cats. Local CBF, as determined by iodoantipyrine testing, was found to be significantly decreased in edematous white matter (mean ± standard error of the mean: 17.3 ± 1.5 ml/100 gm/min) when compared with CBF in the contralateral control white matter (24.8 ± 1.8 ml/100 gm/min). When the values for edematous brain were corrected for dilution, however, the local CBF averaged 25.3 ± 1.7 ml/100 gm/min, which was similar to the control value.

Local CMRgl was found to be significantly increased in plasma-infused white matter (16.3 ± 2.2 µmol/100 gm/min) compared with that in control white matter (10.7 ± 1.3 µmol/100 gm/min). This difference remained, despite correction for dilution and recalculation of local CMRgl values based on altered kinetic constants found in edematous brain. A similar increase in local CMRgl was noted with saline-infusion edema. It is concluded that the increased tissue water level does not alter CBF, but does induce an increase in anaerobic metabolism.

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Leslie N. Sutton, Alan C. McLaughlin, Stephen Dante, Mark Kotapka, Teresa Sinwell and Elizabeth Mills

✓ In order to test the hypothesis that the cerebral arteriovenous oxygen difference (AVDO2) and venous oxygen content (VO2) could be used to monitor brain energy metabolism in the setting of increased intracranial pressure (ICP), 12 cats were studied with 31P-magnetic resonance spectroscopy. Six cats were subjected to intracranial hypertension by cisternal infusion of saline. Energy failure occurred at an average AVDO2 of 8.4 ± 3.2 vol% (± standard deviation) (range 4.7 to 14.7 vol%). The VO2 at the point of metabolic failure averaged 1.45 ± 0.6 vol% and extended over a narrower range (1.0 to 2.9 vol%). In an additional six cats, ICP was raised to the threshold of metabolic failure and hyperventilation was then instituted (pCO2 10 to 18 torr). Five of the six cats experienced a drop in VO2 with hyperventilation. In two of these animals, hyperventilation resulted in a VO2 of 1.1 vol% or less and in metabolic failure as evidenced by a fall in phosphocreatine. It is concluded that a VO2 of less than 2 vol% is correlated with brain ischemia and that the safety of hyperventilation in the setting of increased ICP can be monitored by the use of VO2.

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Matthew R. Sanborn, Jayesh P. Thawani, Robert G. Whitmore, Michael Shmulevich, Benjamin Hardy, Conrad Benedetto, Neil R. Malhotra, Paul Marcotte, William C. Welch, Stephen Dante and Sherman C. Stein

Object

There is considerable variation in the use of adjunctive technologies to confirm pedicle screw placement. Although there is literature to support the use of both neurophysiological monitoring and isocentric fluoroscopy to confirm pedicle screw positioning, there are no studies examining the cost-effectiveness of these technologies. This study compares the cost-effectiveness and efficacy of isocentric O-arm fluoroscopy, neurophysiological monitoring, and postoperative CT scanning after multilevel instrumented fusion for degenerative lumbar disease.

Methods

Retrospective data were collected from 4 spine surgeons who used 3 different strategies for monitoring of pedicle screw placement in multilevel lumbar degenerative disease. A decision analysis model was developed to analyze costs and outcomes of the 3 different monitoring strategies. A total of 448 surgeries performed between 2005 and 2010 were included, with 4 cases requiring repeat operation for malpositioned screws. A sample of 64 of these patients was chosen for structured interviews in which the EuroQol-5D questionnaire was used. Expected costs and quality-adjusted life years were calculated based on the incidence of repeat operation and its negative effect on quality of life and costs.

Results

The decision analysis model demonstrated that the O-arm monitoring strategy is significantly (p < 0.001) less costly than the strategy of postoperative CT scanning following intraoperative uniplanar fluoroscopy, which in turn is significantly (p < 0.001) less costly than neurophysiological monitoring. The differences in effectiveness of the different monitoring strategies are not significant (p = 0.92).

Conclusions

Use of the O-arm for confirming pedicle screw placement is the least costly and therefore most cost-effective strategy of the 3 techniques analyzed.

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Zoher Ghogawala, Christopher I. Shaffrey, Anthony L. Asher, Robert F. Heary, Tanya Logvinenko, Neil R. Malhotra, Stephen J. Dante, R. John Hurlbert, Andrea F. Douglas, Subu N. Magge, Praveen V. Mummaneni, Joseph S. Cheng, Justin S. Smith, Michael G. Kaiser, Khalid M. Abbed, Daniel M. Sciubba and Daniel K. Resnick

Object

There is significant practice variation and considerable uncertainty among payers and other major stakeholders as to whether many surgical treatments are effective in actual US spine practice. The aim of this study was to establish a multicenter cooperative research group and demonstrate the feasibility of developing a registry to assess the efficacy of common lumbar spinal procedures using prospectively collected patient-reported outcome measures.

Methods

An observational prospective cohort study was conducted at 13 US academic and community sites. Unselected patients undergoing lumbar discectomy or single-level fusion for spondylolisthesis were included. Patients completed the 36-item Short-Form Survey Instrument (SF-36), Oswestry Disability Index (ODI), and visual analog scale (VAS) questionnaires preoperatively and at 1, 3, 6, and 12 months postoperatively. Power analysis estimated a sample size of 160 patients: 125 patients with lumbar disc herniation, and 35 with lumbar spondylolisthesis. All patient data were entered into a secure Internet-based data management platform.

Results

Of 249 patients screened, there were 198 enrolled over 1 year. The median age of the patients was 45.0 years (49% female) for lumbar discectomy (n = 148), and 58.0 years (58% female) for lumbar spondylolisthesis (n = 50). At 30 days, 12 complications (6.1% of study population) were identified. Ten patients (6.8%) with disc herniation and 1 (2%) with spondylolisthesis required reoperation. The overall follow-up rate for the collection of patient-reported outcome data over 1 year was 88.3%. At 30 days, both lumbar discectomy and single-level fusion procedures were associated with significant improvements in ODI, VAS, and SF-36 scores (p ≤ 0.0002), which persisted over the 1-year follow-up period (p < 0.0001). By the 1-year follow-up evaluation, more than 80% of patients in each cohort who were working preoperatively had returned to work.

Conclusions

It is feasible to build a national spine registry for the collection of high-quality prospective data to demonstrate the effectiveness of spinal procedures in actual practice. Clinical trial registration no.: 01220921 (ClinicalTrials.gov).

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Praveen V. Mummaneni, Robert G. Whitmore, Jill N. Curran, John E. Ziewacz, Rishi Wadhwa, Christopher I. Shaffrey, Anthony L. Asher, Robert F. Heary, Joseph S. Cheng, R. John Hurlbert, Andrea F. Douglas, Justin S. Smith, Neil R. Malhotra, Stephen J. Dante, Subu N. Magge, Michael G. Kaiser, Khalid M. Abbed, Daniel K. Resnick and Zoher Ghogawala

Object

There is significant practice variation and uncertainty as to the value of surgical treatments for lumbar spine disorders. The authors' aim was to establish a multicenter registry to assess the efficacy and costs of common lumbar spinal procedures by using prospectively collected outcomes.

Methods

An observational prospective cohort study was completed at 13 academic and community sites. Patients undergoing single-level fusion for spondylolisthesis or single-level lumbar discectomy were included. The 36-Item Short Form Health Survey (SF-36) and Oswestry Disability Index (ODI) data were obtained preoperatively and at 1, 3, 6, and 12 months postoperatively. Power analysis estimated a sample size of 160 patients: lumbar disc (125 patients) and lumbar listhesis (35 patients). The quality-adjusted life year (QALY) data were calculated using 6-dimension utility index scores. Direct costs and complication costs were estimated using Medicare reimbursement values from 2011, and indirect costs were estimated using the human capital approach with the 2011 US national wage index. Total costs equaled $14,980 for lumbar discectomy and $43,852 for surgery for lumbar spondylolisthesis.

Results

There were 198 patients enrolled over 1 year. The mean age was 46 years (49% female) for lumbar discectomy (n = 148) and 58.1 years (60% female) for lumbar spondylolisthesis (n = 50). Ten patients with disc herniation (6.8%) and 1 with listhesis (2%) required repeat operation at 1 year. The overall 1-year follow-up rate was 88%. At 30 days, both lumbar discectomy and single-level fusion procedures were associated with significant improvements in ODI, visual analog scale, and SF-36 scores (p = 0.0002), which persisted at the 1-year evaluation (p < 0.0001). By 1 year, more than 80% of patients in each cohort who were working preoperatively had returned to work. Lumbar discectomy was associated with a gain of 0.225 QALYs over the 1-year study period ($66,578/QALY gained). Lumbar spinal fusion for Grade I listhesis was associated with a gain of 0.195 QALYs over the 1-year study period ($224,420/QALY gained).

Conclusions

This national spine registry demonstrated successful collection of high-quality outcomes data for spinal procedures in actual practice. These data are useful for demonstrating return to work and cost-effectiveness following surgical treatment of single-level lumbar disc herniation or spondylolisthesis. One-year cost per QALY was obtained, and this cost per QALY is expected to improve further by 2 years. This work sets the stage for real-world analysis of the value of health interventions.