title: An in vitro analysis of the size and shape of cryolesions for facet joint denervation.
abstract: OBJECTIVE
  Lumbar facet joint syndrome (LFJS) is the cause of lower back pain in 15-54% of the patients. Clinical studies of cryotherapy for LFJS have reported promising outcomes. However, few studies have focused on the technical aspects of cryoneurolysis for LFJS. The aim of the study was to determine the size and shape of cryolesions in vitro and to determine how they are affected by the duration of freezing, size of the cryoprobe and distance and angulation to an osseous boundary layer.
  
  
  METHODS
  Two different cryolesion generators were used. Cryolesions were generated in tempered physiologic NaCl solution in the vicinity of an osseous surface. The size of the cryoprobes, duration of freezing, distance to the bone surface and angulation of the probe were studied. Cryolesions were recorded with a video camera during their emergence. Images at distinct time points were analysed using digital image processing software.
  
  
  RESULTS
  The probe size, the system in use and the duration of the freezing cycle were the main determinants for the size of the cryolesion. The vicinity of the osseous boundary resulted in a modest increase in the size of the cryolesion. Angulation of the cryoprobe towards the osseous boundary is of minor importance for the size of the contact area to the nerve.
  
  
  CONCLUSIONS
  For cryoneurolysis of LFJS, duration of freezing, temperature and probe size are the main determinants of lesion size and thus the probability of success of the procedure. A tangential approach of the probe is not essential.
authors.affiliation: Interdisciplinary Pain Centre, University Hospital Freiburg, Freiburg, Germany. Electronic address: tilman.wolter@uniklinik-freiburg.de.
authors.forename: T
authors.initials: T
authors.lastname: Wolter
authors.affiliation: Interdisciplinary Pain Centre, University Hospital Freiburg, Freiburg, Germany; Department of Neurosurgery, University Hospital Erlangen, Erlangen, Germany.
authors.forename: Y
authors.initials: Y
authors.lastname: Bozhkov
authors.affiliation: Department of Orthopaedic and Trauma Surgery, University Hospital Freiburg, Freiburg, Germany.
authors.forename: S M
authors.initials: SM
authors.lastname: Knoeller
mesh_terms: D003452:Cryosurgery / Q000379:methods*; D003714:Denervation / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D017116:Low Back Pain / Q000601:surgery*; D008159:Lumbar Vertebrae; D021801:Zygapophyseal Joint / Q000294:innervation* / Q000601:surgery*
keywords: Cryoneurolysis; Denervation; Facet joint pain; In vitro study