title: Magnetic Resonance Imaging Signal Characteristics of Medishield: Early Postoperative Profile in a Rabbit Interlaminotomy Model.
abstract: OBJECTIVE
  Application of Medishield to the nerve root is common during spinal surgery to create a mechanical barrier from pain mediators and reduce scar formation. However, Medishield's signal characteristics on magnetic resonance imaging (MRI) have not yet been examined.
  
  
  METHODS
  Microsurgical interlaminotomy was performed on 2 lower lumbar segments in 17 adult New Zealand white rabbits. After dural exposure, applications of 1 mL (autologous blood clot or Medishield) were randomized for each level. On postoperative days 1 through 3, various MRI sequences in 1.5T were performed including T1-weighted, T2-w, T1-gadolinium-weighted, susceptibility-weighted and turbo inversion recovery magnitude (TIRM) sequence. Signaling characteristics were analyzed by 3 blinded observers. Inter-rater agreement was calculated using Fleiss's kappa coefficient (κ). Positive and negative likelihood ratios in detecting Medishield by MRI were determined.
  
  
  RESULTS
  Of 24 MRIs performed, TIRM sequence identified Medishield with the highest likelihood ratio. Medishield's positive likelihood ratio was highest (5.8) on postoperative day 1 with interobserver agreement of 93% (κ = 0.75); these rates declined to 2.5 and 1.4 on postoperative days 2 and 3 with interobserver agreements of 71% (κ = 0.43) and 83% (κ = 0.67), respectively. Medishield adherence was confirmed in each rabbit by histologic examinations.
  
  
  CONCLUSIONS
  Understanding that radiologic detection of Medishield diminished over time as its signal characteristics became less distinguishable from a blood clot is essential in clinical practice. Medishield was detected on postoperative day 1 but not 2 days later after hemodynamic changes had occurred. These results may provide a guide for postoperative findings, such as differential diagnosis of hematoma.
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland. Electronic address: edin.nevzati@gmail.com.
authors.forename: Edin
authors.initials: E
authors.lastname: Nevzati
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Jatta
authors.initials: J
authors.lastname: Berberat
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Jehuda
authors.initials: J
authors.lastname: Soleman
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Coluccia
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Carl
authors.initials: C
authors.lastname: Muroi
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Salome
authors.initials: S
authors.lastname: Schöpf
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Anton
authors.initials: A
authors.lastname: Lukes
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Fischer
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Luca
authors.initials: L
authors.lastname: Remonda
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Javier
authors.initials: J
authors.lastname: Fandino
authors.affiliation: Department of Neurosurgery, Kantonsspital Aurau, Aarau, Switzerland.
authors.forename: Serge
authors.initials: S
authors.lastname: Marbacher
mesh_terms: D000818:Animals; D002921:Cicatrix / Q000517:prevention & control; D004195:Disease Models, Animal; D005260:Female; D007796:Laminectomy / Q000379:methods*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008866:Microsurgery / Q000379:methods*; D059351:Organ Sparing Treatments / Q000379:methods*; D011184:Postoperative Period; D011817:Rabbits; D020196:Trauma, Nervous System / Q000517:prevention & control
keywords: Animal model; Interlaminotomy model; Lumbar disk disease; Magnetic resonance imaging; Medishield; New Zealand white rabbit; Postoperative fibrosis