title: Osteosynthesis-screw augmentation by ultrasound-activated biopolymer--an ovine in vivo study assessing biocompatibility and bone-to-implant contact.
abstract: OBJECTIVE
  Screw fixation and fragment anchoring in osteoporotic bones is often difficult. Problems like the cut out phenomenon and implant migration in osteoporotic bones have been reported. One possibility of improving the anchoring force of screws is augmentation of the screw. Cement-augmented screws in spinal surgery could exhibit a better anchoring in osteoporotic bones.
  
  
  METHODS
  The purpose of this study was to examine the effect of screw augmentation using a resorbable polymer. Ultrasound-activated biodegradable pins were used for the purpose of a resorbable augmentation technique. Cannulated screws were inserted into the femur of 12 sheep and augmented by an ultrasound-activated polylactic acid (PLDLA) pin. In a paired approach, four screws were implanted in each animal: 2× a 10-mm thread and 2× a 20-mm thread, both of which were augmented with polymer. Both screws, named A and B, were also applied without augmentation (control group) and implanted into the contralateral hind limb. After 4, 8, and 12 weeks, the sheep were euthanized and a macroscopical and histological examination followed.
  
  
  RESULTS
  The polymer spread well out of the screws into the cancellous lacunae. Around the polymer, the peripheral bone showed signs of healthy and active bone tissue. No evidence of inflammation or infection was observed. The boneto-implant contact was significantly higher in the augmented screws. Biocompatibility was proven in histopathological examination. After 12 weeks, no pathological changes were found.
  
  
  CONCLUSIONS
  Ultrasound-activated polymer augmentation of cannulated screws may improve the anchoring in osteoporotic bone.
  Can screw augmentation using a resorbable polymer improve the bone-to-implant contact in case of screw osteosynthesis? Is there any effect on the surrounding tissue by the induced temperature and liquefied polymer? Can biocompatibility be proven by this new osteosynthesis?
  
  
  CONCLUSIONS
  Screw augmentation by ultrasound-activated biopolymer leads to a significant higher bone-to-implant contact than pure screw osteosynthesis. No tissue damage could be observed by the application of the SonicFusion™.
  
  
  CONCLUSIONS
  The ovine in vivo study concept can simulate physiological conditions. First examination of screw augmentation by ultrasound-activated biopolymer. No biomechanical testing of the higher bone-to-implant contact by now.
authors: BG Trauma Hospital, Hamburg, Germany. Hanjo_Neumann@gmx.de.
authors: Hanjo
authors: H
authors: Neumann
authors: BG Trauma Hospital, Hamburg, Germany. S.breer@buk-hamburg.de.
authors: Stefan
authors: S
authors: Breer
authors: Medical Faculty, University of Lübeck, Lübeck, Germany. Nils.Reimers@STRYKER.com.
authors: Nils
authors: N
authors: Reimers
authors: Department of Orthopaedics, University Greifswald, Greifswald, Germany. kaschr@uni-greifswald.de.
authors: Richard
authors: R
authors: Kasch
authors: Medical Faculty, University of Lübeck, Lübeck, Germany. schulz@biomechatronics.de.
authors: Arndt-Peter
authors: AP
authors: Schulz
authors: BG Trauma Hospital, Hamburg, Germany. bekienast@web.de.
authors: Benjamin
authors: B
authors: Kienast
mesh_terms: D000818:Animals; D001863:Bone Screws; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods*; D008422:Materials Testing; D011091:Polyesters / Q000627:therapeutic use*; D012756:Sheep; D000069453:Ultrasonic Waves
chemical_list: D011091:Polyesters; C033616:poly(lactide)
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