title: Penetration force, geometry, and cutting profile of the novel and old Ozurdex needle: the MONO study.
abstract: OBJECTIVE
  To investigate the geometry, penetration force, and cutting profile of the novel and old needle of the drug delivery system (DDS) for Ozurdex injections in a standardized laboratory setting.
  
  
  METHODS
  In this experimental study, the normative geometrical data of the DDS needle were systematically analyzed according to nomenclature DIN 13097 (ISO 7864) and ISO 9626. The force to penetrate a standardized 0.4-mm-thick polyurethane foil was measured by a penetrometer, when the needle was piercing, cutting, and sliding through the foil and plotted as a load-displacement diagram. Magnified images of the consecutive cut were taken after the entire penetration through the foil.
  
  
  RESULTS
  In this experimental study, the mean point length was equal to 3.34 mm (3.28-3.36 mm) for the old DDS needle versus 3.33 mm (3.30-3.36 mm) for the new DDS needle. The secondary bevel length was 1.64 mm (1.42-1.73 mm) for the new and 1.66 mm (1.62-1.69 mm) for the old needle. The primary angle was 9.2° (9.0°-9.5°) for the old and 8.9° (8.5°-9.0°) for the new needle, respectively. The secondary bevel angle was 117.2° (116°-118°) for the old and 111.4° (110°-113°) for the new needle. The mean penetration force of the old DDS needles was significantly higher at all phases of the penetration experiment: The mean piercing force was 0.7 Newton (N) with the old and 0.47 N with the new DDS needle. The mean cutting force was remarkable higher with 1.1 N for the old DDS needle versus 0.78 N for the new DDS needle. The dilatation phase was not statistically significant between 0.94 and 0.99 N in both DDS needles. The friction phase was maintained at significantly higher levels with the old DDS needle of 0.47 N, whereas it returned to the lowest measurements of 0.11 N with the new DDS needle. Both DDS systems induced a characteristic chevron-shaped incision.
  
  
  CONCLUSIONS
  A comparison of the old and new DDS needles demonstrated a reduced penetration force with the modified new DDS needle, which may help to achieve a smooth penetration through the human sclera.
authors.affiliation: 1 Department of Ophthalmology, Pallas Clinic , Aarau, Switzerland .
authors.forename: Carsten H
authors.initials: CH
authors.lastname: Meyer
authors.forename: Zengping
authors.initials: Z
authors.lastname: Liu
authors.forename: Christian K
authors.initials: CK
authors.lastname: Brinkmann
authors.forename: Eduardo B
authors.initials: EB
authors.lastname: Rodrigues
authors.forename: Thomas
authors.initials: T
authors.lastname: Bertelmann
mesh_terms: D016503:Drug Delivery Systems / Q000295:instrumentation / Q000592:standards*; D004867:Equipment Design / Q000295:instrumentation / Q000592:standards; D007267:Injections / Q000295:instrumentation / Q000592:standards*; D009339:Needles / Q000592:standards*