title: Pen needle design influences ease of insertion, pain, and skin trauma in subjects with type 2 diabetes.
abstract: OBJECTIVE
  Pen needles used for subcutaneous injections have gradually become shorter, thinner and more thin walled, and thereby less robust to patient reuse. Thus, different needle sizes, alternative tip designs and needles resembling reuse were tested to explore how needle design influences ease of insertion, pain and skin trauma.
  
  
  METHODS
  30 subjects with injection-treated type 2 diabetes and body mass index 25-35 kg/m2were included in the single-blinded study. Each subject received abdominal insertions with 18 different types of needles. All needles were tested twice per subject and in random order. Penetration force (PF) through the skin, pain perception on 100 mm visual analog scale, and change in skin blood perfusion (SBP) were quantified after the insertions.
  
  
  RESULTS
  Needle diameter was positively related to PF and SBP (p<0.05) and with a positive pain trend relation. Lack of needle lubrication and small 'needle hooks' increased PF and SBP (p<0.05) but did not affect pain. Short-tip, obtuse needle grinds affected PF and SBP, but pain was only significantly affected in extreme cases. PF in skin and in polyurethane rubber were linearly related, and pain outcome was dependent of SBP increase.
  
  
  CONCLUSIONS
  The shape and design of a needle and the needle tip affect ease of insertion, pain and skin trauma. Relations are seen across different data acquisition methods and across species, enabling needle performance testing outside of clinical trials.
  
  
  BACKGROUND
  NCT02531776; results.
authors.affiliation: Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; Device R&D Device R&D, Novo Nordisk A/S, Hillerød, Denmark.
authors.forename: Kezia A
authors.initials: KA
authors.lastname: Præstmark
authors.affiliation: Medical & Science Devices , Novo Nordisk A/S , Søborg , Denmark.
authors.forename: Morten L
authors.initials: ML
authors.lastname: Jensen
authors.affiliation: Device R&D Device R&D , Novo Nordisk A/S , Hillerød , Denmark.
authors.forename: Nils B
authors.initials: NB
authors.lastname: Madsen
authors.affiliation: Insulin Pharmacology , Novo Nordisk A/S , Måløv , Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Kildegaard
authors.affiliation: Department of Biomedical Sciences , University of Copenhagen , Copenhagen , Denmark.
authors.forename: Bente M
authors.initials: BM
authors.lastname: Stallknecht
keywords: Devices; Medical Device(s); Pain; Type 2 Diabetes