title: A quantitative study of intervertebral disc morphologic changes following plasma-mediated percutaneous discectomy.
abstract: OBJECTIVE
  To quantitatively evaluate interval magnetic resonance imaging (MRI) changes in disc morphology following plasma-mediated percutaneous discectomy.
  
  
  METHODS
  A retrospective comparison of pretreatment and posttreatment MRIs at a single university spine clinic.
  
  
  METHODS
  From a group of 60 consecutively treated patients, 15 met the study inclusion and exclusion criteria. All had either failed treatment or had other clinical reasons for a posttreatment MRI.
  
  
  METHODS
  Two independent physicians electronically measured disc protrusion size and disc height at the treatment discs and adjacent discs on pre- and posttreatment MRI scans. Additionally, images were compared for gross anatomic changes including disc degeneration by Pfirrman classification, new disc herniations, high intensity zone (HIZ), vertebral endplate changes, post-contrast enhancement, and changes in segmental alignment. Pearson r correlation was used to determine interobserver reliability between the two physicians' MRI measurements. Paired t-tests were calculated for comparisons of pre- and posttreatment MRI measurements, and an ANOVA was performed for comparison of pre- to posttreatment changes in disc height measurements at treatment levels relative to adjacent levels.
  
  
  RESULTS
  Correlation was high for measurement of disc height change (r = 0.89; P < 0.0001) and good for anteroposterior protrusion size change (r = 0.51; P = 0.0512). Disc height at treated discs demonstrated a small but statistically significant mean interval reduction of 0.48 mm (P = 0.0018). This remained significant when compared with the adjacent control discs (P < 0.0001). Pretreatment mean disc protrusion size (4.74 mm; range 3.75-6.55 mm) did not differ significantly (P = 0.1145) from posttreatment protrusion size (4.42 mm; range 2.55-7.95 mm). Gross anatomic changes at treatment levels included reduced disc protrusion size (N = 6), enlarged protrusion (N = 3), resolution of HIZ (N = 3), and improvement in endplate signal changes (N = 1). Also, 11/15 posttreatment MRIs included post-contrast images that showed epidural fibrosis (N = 1), rim enhancement (N = 2), and enhancement of the posterior annulus (N = 4).
  
  
  CONCLUSIONS
  Based on MRI examinations, subtle anatomic changes may occur following plasma-mediated percutaneous discectomy. Further study is required to determine the clinical relevance of these changes.
authors.affiliation: PM&R Section, Department of Orthopaedic Surgery, Stanford University, Redwood City, California, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Smuck
authors.forename: Joshua
authors.initials: J
authors.lastname: Levin
authors.forename: Eric
authors.initials: E
authors.lastname: Zemper
authors.forename: Adil
authors.initials: A
authors.lastname: Ali
authors.forename: David J
authors.initials: DJ
authors.lastname: Kennedy
mesh_terms: D000328:Adult; D017587:Diskectomy, Percutaneous / Q000009:adverse effects* / Q000379:methods*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult
keywords: Nucleoplasty; Percutaneous; Protrusion; Radiculopathy