Neuromodulation: Technology at the Neural Interface ( DOI: 10.1111/ner.12155


Centers of Excellence for Neuromodulation: A Critical Proposal

excellence for our patients and our health care economies. That is to say that only 10% of spinal cord stimulator implanters, for example, perform 90% of these procedures, leaving 90% of implanters to do no more than 10% of SCS implants. The vast majority of implanters perform less than ten such procedures a year, far too few to ensure quality, much less excellence (personal communication, Bradley Maruca, November 25, 2013).


Figure 2. Dr. Daniel Levitin. Dr. Levitin runs McGill University’s laboratory for music perception and expertise.

Despite this, nowhere is the correlation between practice and quality more evident than in the procedural specialties of medicine (3–10). Halm and coworkers performed a systematic literature review to determine the magnitude and significance of the association between volume and outcomes (11). Searching MEDLINE for population-based studies examining the independent relationship between hospital or physician volume and clinical outcomes, the authors found 135 of 272 studies that met inclusion criteria. Seventyone percent of the studies of hospital volume and 69% of studies of physician volume reported statistically significant associations between higher volume and better outcomes. Statistically significant associations were found for AIDS treatment and for surgery for pancreatic cancer, esophageal cancer, abdominal aortic aneurysms (AAAs), pediatric cardiac surgery, coronary artery bypass surgery, coronary angioplasty, carotid endarterectomy, other cancer surgery, and orthopedic surgery. For procedures with the strongest associations, as many as 13 excess deaths per 100 cases were attributed to low volume.

© 2014 International Neuromodulation Society

Neuromodulation 2014; 17: 1–9


As a field, we have struggled with methods to increase the efficacy of our procedures, decrease their risks, and improve patient outcomes. By doing so, we further legitimize our field, improve patient satisfaction, and demonstrate the cost-effectiveness that is necessary to drive reimbursement and thus patient access to neuromodulation procedures. One important way to improve results in our specialty is to ensure that neuromodulation practitioners have, indeed, practiced, and practiced quite a lot. In his book, Outliers, Malcolm Gladwell points to the correlation between the level of practice and excellence. “The idea that excellence at performing a complex task requires a critical minimum level of practice surfaces again and again in studies of expertise. In fact, researchers have settled on what they believe is the magic number for true expertise: ten thousand hours” (1). Although Gladwell discusses excellence in sports, music, and computer science, this correlation appears to hold for virtually any discipline. He quotes Daniel Levitin, a neuroscientist whose research focuses on the development of excellence,“The emerging pictures from such studies is that ten thousand hours of practice is required to achieve the level of mastery associated with being a world-class expert—in anything” (2). Gladwell goes on to state that “practice isn’t the thing you do once you’re good. It’s the thing you do that makes you good.” Gladwell suggests that it takes about ten years to develop such excellence. “And what’s ten years? Well, it’s roughly how long it takes to put in ten thousand hours of hard practice. Ten thousand hours is the magic number of greatness” (Figs. 1 and 2). Although the actual amount of practice required may be debated, the recognition that excellence derives, at least in part, from experience cannot. Unfortunately, there Figure 1. Malcolm Gladwell, appears to be a conflict between author of several best selling the way in which neuromodulation is practiced and our desire to ensure books, including Outliers.

LEVY Birkmeyer and coworkers attempted to determine the relative importance of the experience of the operating surgeon as compared with hospital volume on surgical mortality (12). Using information from the national Medicare claims database for 1998 through 1999, the authors examined mortality among all 474,108 patients who underwent one of eight cardiovascular procedures or cancer resections. Surgeon volume was inversely related to operative mortality for all eight procedures (p = 0.003 for lung resection, p < 0.001 for all other procedures). The adjusted odds ratio (OR) for operative death (for patients with a low-volume surgeon vs. those with a high-volume surgeon) varied widely according to the procedure—from 1.24 for lung resection to 3.61 for pancreatic resection. Surgeon volume accounted for a large proportion of the apparent effect of the hospital volume to an extent that varied according to the procedure: It accounted for 100% of the effect for aortic valve replacement, 57% for elective repair of an AAA, 55% for pancreatic resection, 49% for coronary artery bypass graft (CABG), 46% for esophagectomy, 39% for cystectomy, and 24% for lung resection. For most procedures, the mortality rate was higher among patients of low-volume surgeons than among those of highvolume surgeons, regardless of the surgical volume of the hospital in which they practiced. More recently, Chowdhury and colleagues published a systematic review of the impact of volume of surgery and specialization on patient outcome (13). Their search identified 55,391 articles published between 1957 and 2002; 1075 were relevant to the study, of which 163, involving 9,904,850 patients, fulfilled the entry criteria. These 163 studies examined 42 different surgical procedures, spanning 13 surgical specialties. Hospital volume was reported in 127 studies; high-volume hospitals had significantly better outcomes in 74.2% of studies. In prospective studies, hospital volumes correlated with improved outcomes in only 40% of reports. Surgeon volume was reported in 58 studies; high-volume surgeons had significantly better outcomes in 74% of studies. Specialization was reported in 22 studies; specialist surgeons had significantly better outcomes than general surgeons in 91% of studies. The authors concluded that high surgeon volume and specialization are associated with improved patient outcome, whereas high hospital volume is of limited benefit. Analysis of specialty surgery procedure outcome data has largely confirmed these conglomerate studies. For example:



Hannan et al. (14) evaluated the effect of hospital and surgeon volume on in-hospital mortality for pediatric cardiac surgical procedures. In this population-based retrospective cohort study, the authors evaluated the results of 7169 cases from 16 acute care hospitals in New York with certificate of need approval to perform pediatric cardiac surgery. After controlling for the severity of preprocedural illness, hospitals with annual surgical volumes fewer than 100 had significantly higher mortality rates (8.26%) than those with volumes of 100 or more (5.95%). Surgeons with annual volumes of fewer than 75 had significantly higher mortality rates (8.77%) than surgeons with annual volumes of 75 or more (5.90%). Similar results have been obtained for CABG procedures (15). Peterson and coworkers performed an observational analysis of 267,089 isolated CABG procedures performed at 439 US hospitals participating in the Society of Thoracic Surgeons National Cardiac Database between January 1, 2000 and December 31, 2001. The median (interquartile range) annual hospital-isolated CABG volume

Figure 3. Artist’s rendering of single, double, and triple coronary artery bypass surgical procedure.

was 253 (165–417) procedures, with 82% of centers performing fewer than 500 procedures per year. The overall operative mortality was 2.66%. After adjusting for patient risk and clustering effects, rates of operative mortality decreased with increasing hospital CABG volume (0.07% for every 100 additional CABG procedures; adjusted OR, 0.98; 95% confidence interval [CI], 0.96–0.99; p = 0.004).

VASCULAR SURGERY Cowan and coworkers evaluated the relationship between hospital and surgeon volume and outcomes for thoracoabdominal aortic aneurysm (TAAA) repair (16). They evaluated clinical information regarding repair of intact TAAA in 1542 patients from 1988 to 1998 from the Nationwide Inpatient Sample (NIS), a stratified discharge database of a representative 20% of hospitals in the United States. Annual hospital volume of TAAA treated was grouped into terciles and defined as low (LVH; one to three cases [median, 1]), medium (MVH; two to nine cases [median, 4]), or high (HVH; 5–31 cases [median, 12]). Annual surgeon volume was defined as low (LVS; one to two cases [median, 1]) or high (HVS; 3–18 cases [median, 7]). Overall mortality was 22.3%, although mortality improved over time. LVH and HVH differed in mortality rates (27.4% vs. 15.0%; p < 0.001). Mortality between LVS and HVS also differed significantly (25.6% vs. 11.0%; p < 0.001). When controlling for patient demographic data, comorbid conditions, and postoperative complications, both hospital and surgeon volume were significant predictors of mortality for intact TAAA repair (LVS: OR 2.6, p < 0.001; LVH: OR 2.2, p < 0.001; and MVH: OR 1.7, p = 0.004). The authors suggested that regionalization of care to high-volume providers with consistently lower postoperative mortality should be considered. Dimick and coworkers (17) demonstrated that in addition to surgeon and provider volume, surgical specialty training correlated with outcomes for AAA repair. The authors reviewed the data for 3912 patients undergoing AAA repair in the NIS during 1997. In-hospital mortality was compared between high-volume hospitals (more than 35 per year) and low-volume hospitals and between high-volume surgeons (more than ten per year) and low-volume surgeons. Vascular, cardiac, and general surgery specializations were identified by analysis of other procedures performed by each surgeon. Overall, AAA repair mortality was 4.2% and was lower at highvolume hospitals (3.0%) than at low-volume hospitals (5.5%) (p < 0.001). Lowest mortality was associated with operations performed

© 2014 International Neuromodulation Society

Neuromodulation 2014; 17: 1–9

FROM THE EDITOR-IN-CHIEF by vascular surgeons (2.2%) compared with cardiac surgeons (4.0%) and general surgeons (5.5%) (p < 0.001). Mortality rates also were lower for high-volume hospitals (2.5%) compared with low-volume hospitals (5.6%) (p < 0.001). In a risk-adjusted analysis, high-volume hospital, vascular surgery specialty, and high-volume surgeon were all independently associated with lower risk of in-hospital mortality. In this analysis, risk reduction was 30% for high-volume hospitals (95% CI, 2–51%; p < 0.05) and 40% for surgery by a high-volume surgeon (95% CI, 12–60%; p = 0.01). AAA repair by general surgeons compared with vascular surgeons was associated with 76% greater risk for death (95% CI, 10–190%; p = 0.02). No significant difference in mortality was found between cardiac and vascular surgeons. The authors suggested that health policy in support of selective referral for AAA repair should consider surgical specialization in addition to provider volume thresholds.

Figure 4. Artist’s rendering of minigastric bypass surgical procedure (© Can Stock Photo Inc./Alila).

COLORECTAL SURGERY In their study of outcomes following colorectal resection, Harmon et al. (18) examined the association of surgeon and hospital case volumes with the short-term outcomes of in-hospital death, total hospital charges, and length of stay (LOS) for resection of colorectal carcinoma. Cases were divided into three groups based on annual surgeon case volume—low (less than or equal to five), medium (five to ten), and high (greater than ten)—and hospital volume—low (100 cases/year), medium (50–100 cases/year), or low volume (

Centers of excellence for neuromodulation: a critical proposal.

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