title: The Volume-Outcome Effect: Impact on Trial-to-Permanent Conversion Rates in Spinal Cord Stimulation.
abstract: OBJECTIVE
  Conversion rates from trial leads to permanent spinal cord stimulation (SCS) systems have important implications for healthcare resource utilization (HCRU) and pain management. We hypothesized that there is a volume-outcome effect, with chronic pain patients who visit high volume SCS implanters will have higher trial-to-permanent conversion rates.
  
  
  METHODS
  We designed a large, retrospective analysis using the Truven MarketScan database analyzing adult SCS patients with provider information available, with or without IPG implantation from the years 2007 to 2012 was designed. Patients were divided into three provider-based groups: high (>25), medium (9-24), and low (3-8) volume providers. Univariate and multivariate models identified factors associated with successful conversion.
  
  
  RESULTS
  A total of 17,850 unique trial implants were performed by 3028 providers. Of 13,879 patients with baseline data available, 8981 (64.7%) progressed to permanent SCS. Higher volume providers were associated with slightly higher conversion rates (65.9% vs. 63.3% low volume, p = 0.029), explant rates (9.2% vs. 7.7% medium volume, p = 0.026), younger age (52.0 ± 13.4 years vs. 53.0 ± 13.4 years, p = 0.0026), Medicare/Medicaid (47.8% vs. 35.0% low volume, p < 0.0001), Southern region (53.5% vs. 38.9% low volume, p < 0.0001), and higher Charlson comorbidity scores (1.0 [SD = 1.4], p = 0.0002). Multivariate regression results showed female gender (1.13 [95% CI: 1.05-1.22], p < 0.001) and high volume providers associated with higher odds of successful trial conversion (1.12 [95% CI: 1.02-1.22], p = 0.014).
  
  
  CONCLUSIONS
  In this nationwide analysis, high volume providers achieved higher trial-to-permanent SCS conversion rates than lower volume providers. The study has implications for both training requirements and referral patterns to delineate minimum implant experience necessary for provider proficiency. Future studies may be useful to understand HCRU differences.
authors.affiliation: Department of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Kelly Ryan
authors.identifier: http://orcid.org/0000-0002-9220-3563
authors.initials: KR
authors.lastname: Murphy
authors.affiliation: Department of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Jing L
authors.initials: JL
authors.lastname: Han
authors.affiliation: Department of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Syed Mohammed Qasim
authors.initials: SM
authors.lastname: Hussaini
authors.affiliation: Department of Biostatistics, Duke University Medical Center, Durham, NC, USA.
authors.forename: Siyun
authors.initials: S
authors.lastname: Yang
authors.affiliation: Department of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Beth
authors.initials: B
authors.lastname: Parente
authors.affiliation: Department of Biostatistics, Duke University Medical Center, Durham, NC, USA.
authors.forename: Jichun
authors.initials: J
authors.lastname: Xie
authors.affiliation: Department of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Shivanand P
authors.initials: SP
authors.lastname: Lad
mesh_terms: D000328:Adult; D000368:Aged; D059350:Chronic Pain / Q000453:epidemiology / Q000628:therapy*; D015331:Cohort Studies; D016208:Databases, Factual / Q000706:statistics & numerical data; D004567:Electrodes, Implanted / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D062187:Spinal Cord Stimulation / Q000379:methods* / Q000706:statistics & numerical data*; D014481:United States
keywords: Chronic pain; outcomes; spinal cord stimulator (SCS); trial conversion; volume-outcome effect