title: Assessing the Magnitude of Effect of Bone Structures on Shockwave Lithotripsy Fragmentation: Results from an In Vitro Study.
abstract: BACKGROUND
  Several anatomic and clinical factors have been implicated in the failure rates of shock wave lithotripsy (SWL), including the attenuating effects of bony structures. We designed an in vitro model that incorporates the lumbar spine, including vertebral bodies and transverse processes along the pathway of shockwaves, to mimic the clinical scenario during SWL of upper ureteral stones. We hypothesized that the presence of bone structures in the SWL pathway significantly affects the fragmentation rate.
  
  
  METHODS
  An ordnance gelatin (OG) model was conceptualized and created to allow a pig's lumbar spine to be embedded within it. Artificial urinary calculi weighing 2 ± 0.1 g (1.2-cm diameter) were prepared using BegoStone plaster. The trial was divided into two arms: group 1 models had OG only and served as the control and group 2 models had the bone embedded in the gelatin with stone wells placed above the transverse processes. Twenty-four stones per group were subjected to SWL using the STORZ MODULITH SLX-F2 lithotripter, using the same treatment parameters. Fragments were sieved through 2- and 4-mm filters, and the fragmentation coefficients (FC) were calculated. The Mann-Whitney test was used to compare FC between the two groups.
  
  
  RESULTS
  The mean fragmentation rate of group 1 was statistically significantly higher compared with group 2 using a 4-mm sieve (43% vs 0.62%, p < 0.001) and the 2-mm filter (18% vs 0.52%, p < 0.001).
  
  
  CONCLUSIONS
  The presence of bone structures dramatically reduces the fragmentation rate of phantom stones using an OG in vitro model. The OG model is inexpensive and simple to use to simulate clinical situations during SWL.
authors.affiliation: Division of Urology, Department of Surgery, Schulich School of Medicine & Dentistry, The University of Western Ontario , London, Ontario, Canada .
authors.forename: Daniel
authors.initials: D
authors.lastname: Olvera-Posada
authors.affiliation: Division of Urology, Department of Surgery, Schulich School of Medicine & Dentistry, The University of Western Ontario , London, Ontario, Canada .
authors.forename: Husain
authors.initials: H
authors.lastname: Alenezi
authors.affiliation: Division of Urology, Department of Surgery, Schulich School of Medicine & Dentistry, The University of Western Ontario , London, Ontario, Canada .
authors.forename: Thomas
authors.initials: T
authors.lastname: Tailly
authors.affiliation: Division of Urology, Department of Surgery, Schulich School of Medicine & Dentistry, The University of Western Ontario , London, Ontario, Canada .
authors.forename: Marie
authors.initials: M
authors.lastname: Dion
authors.affiliation: Division of Urology, Department of Surgery, Schulich School of Medicine & Dentistry, The University of Western Ontario , London, Ontario, Canada .
authors.forename: John D
authors.initials: JD
authors.lastname: Denstedt
authors.affiliation: Division of Urology, Department of Surgery, Schulich School of Medicine & Dentistry, The University of Western Ontario , London, Ontario, Canada .
authors.forename: Hassan
authors.initials: H
authors.lastname: Razvi
mesh_terms: D000162:Acoustics; D000818:Animals; D005780:Gelatin; D006801:Humans; D007669:Kidney Calculi / Q000601:surgery*; D008096:Lithotripsy / Q000379:methods*; D008159:Lumbar Vertebrae; D019047:Phantoms, Imaging; D013552:Swine; D014057:Tomography, X-Ray Computed; D014514:Ureteral Calculi / Q000601:surgery*; D014545:Urinary Calculi / Q000601:surgery*; D014556:Urine
chemical_list: D005780:Gelatin