title: Ablation of bone, cartilage, and facet joint capsule using Ho:YAG laser.
abstract: OBJECTIVE
  The objective of this study was to determine of the efficiency of holmium:YAG laser for bone ablation, compared to cartilage and soft tissue of the intervertebral foramen of the lumbosacral spine.
  
  
  BACKGROUND
  The holmium:YAG (Ho:YAG) laser has been used for ablation of bulging or prolapsed discs and also has the potential for decompression of the nerve root when there is narrowing of the foraminae (foraminoplasty). It is proposed that laser ablation of bone and ligament of the intervertebral foramen for nerve root decompression using the Ho:YAG laser is able to produce sufficient bone ablation without inducing significant thermal necrosis in surrounding tissues due to its short absorption length, which could result in significant clinical advantages.
  
  
  METHODS
  Experiments were performed on samples of laminar bone, facet joint capsule, and cartilage for quantitative and qualitative determination of the effect of Ho:YAG ablation on tissue mass loss using a range of pulse energies from 0.5 to 1.5 J/P at 15 pulses/sec.
  
  
  RESULTS
  The results showed a significant linear correlation between the mass loss and pulse energy, and between the mass loss and radiant exposure. Electron microscopy and histology showed that the Ho:YAG ablation resulted in a very sharp and clear border with little charring. Applying 0.01 k.J of total energy at two different settings (1.5 J/p, high power, and 0.5 J/p, low power) at 15 pulses/sec, the cross-sectional area/mm(2) of the ablated bone was measured, using light microscopy and the Scion Image analysis program. The ablated areas were 2.28 +/- 0.87 and 1.16 +/- 0.43 mm(2) at high and low power, respectively (p = 0.008).
authors.affiliation: Department of Musculoskeletal Surgery, Division of Surgery, Anaesthesia and Intensive Care, Imperial College School of Medicine, Charing Cross Hospital, London, United Kingdom.
authors.forename: M I
authors.initials: MI
authors.lastname: Hafez
authors.forename: R R H
authors.initials: RR
authors.lastname: Coombs
authors.forename: S
authors.initials: S
authors.lastname: Zhou
authors.forename: I D
authors.initials: ID
authors.lastname: McCarthy
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects; D002358:Cartilage, Articular / Q000473:pathology / Q000528:radiation effects / Q000648:ultrastructure; D066298:In Vitro Techniques; D017746:Joint Capsule / Q000473:pathology / Q000528:radiation effects / Q000648:ultrastructure; D007834:Lasers; D008159:Lumbar Vertebrae / Q000473:pathology / Q000528:radiation effects* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D012756:Sheep; D014463:Ultrasonography; D021801:Zygapophyseal Joint / Q000473:pathology / Q000528:radiation effects