title: Establishing an optimal "cutoff" threshold for diagnostic lumbar facet blocks: a prospective correlational study.
abstract: OBJECTIVE
  Diagnostic medial branch blocks (MBB) are considered the reference standard for diagnosing facetogenic pain and selecting patients for radiofrequency (RF) denervation. Great controversy exists regarding the ideal cutoff for designating a block as positive. The purpose of this study is to determine the optimal pain relief threshold for selecting patients for RF denervation after diagnostic MBB.
  
  
  METHODS
  In this multicenter, prospective correlational study, 61 consecutive patients undergoing lumbar facet RF denervation after experiencing significant pain relief after MBB were enrolled. A positive outcome was defined as a ≥50% reduction in back pain at rest or with activity coupled with a positive satisfaction score lasting longer than 3 months. The relationship between pain relief after the blocks and denervation outcomes was evaluated by pairwise correlation matrix, receiver's operating characteristic curve, and stratifying outcomes based on 10- and 17-percentage point intervals for MBB.
  
  
  RESULTS
  There were no significant differences in RF outcomes based on any MBB pain relief cutoff over 50%. A trend was noted whereby those patients who obtained <50% pain relief reported poorer outcomes. No optimal threshold for designating a diagnostic block as positive, above 50% pain relief, could be calculated.
  
  
  CONCLUSIONS
  Employing more stringent selection criteria for lumbar facet RF is likely to result in withholding a beneficial procedure from a substantial number of patients, without improving success rates.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD, USA. scohen40@jhmi.edu
authors.forename: Steven Paul
authors.initials: SP
authors.lastname: Cohen
authors.forename: Scott A
authors.initials: SA
authors.lastname: Strassels
authors.forename: Connie
authors.initials: C
authors.lastname: Kurihara
authors.forename: Scott R
authors.initials: SR
authors.lastname: Griffith
authors.forename: Brandon
authors.initials: B
authors.lastname: Goff
authors.forename: Kevin
authors.initials: K
authors.lastname: Guthmiller
authors.forename: Hieu T
authors.initials: HT
authors.lastname: Hoang
authors.forename: Benny
authors.initials: B
authors.lastname: Morlando
authors.forename: Conner
authors.initials: C
authors.lastname: Nguyen
mesh_terms: D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage; D018771:Arthralgia / Q000175:diagnosis / Q000601:surgery; D002045:Bupivacaine / Q000008:administration & dosage*; D017115:Catheter Ablation / Q000379:methods*; D003714:Denervation / Q000379:methods*; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis* / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000187:drug effects; D008297:Male; D008396:Maryland; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D013223:Statistics as Topic; D016896:Treatment Outcome; D021801:Zygapophyseal Joint / Q000187:drug effects
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine