title: Long-term stability of angle-stable versus conventional locked intramedullary nails in distal tibia fractures.
abstract: BACKGROUND
  In the last years intramedullary nailing has become the treatment of choice for most displaced diaphyseal tibia fractures. In contrast intramedullary nailing of distal tibia fractures is accompanied by problems like decreased biomechanical stability. Nevertheless the indications for intramedullary nailing have been extended to include even more distal fractures. The purpose of this study was to compare long-term mechanical characteristics of angle-stable versus conventional locked intramedullary nails in the treatment of unstable distal tibia fractures. Therefore, the effect of time on the mechanical properties of biodegradable sleeves was assessed.
  
  
  METHODS
  8 pairs of fresh, frozen porcine tibiae were used. The expert tibial nail (Synthes) was equipped with either three conventional locking screws (CL) or the angle-stable locking system (AS), consisting of a special ASLS screw and a biodegradable sleeve. Biomechanical testing included torsional and axial loading at different time-points over 12 weeks.
  
  
  RESULTS
  The AS group showed a significantly higher torsional stiffness at all time-points (at least 60%) compared to the CL group (p < 0.001). The neutral zone was at least 5 times higher in the CL group (p < 0.001). The mean axial stiffness was maximum 10% higher (week 6) in the angle-stable locked group compared to the conventional group. There was no significant change of the torsional mechanical characteristics over the 12 weeks in both groups (p > 0.05). For axial stiffness and range of motion significant differences were found in the AS group.
  
  
  CONCLUSIONS
  The angle-stable locking system (ASLS) with the biodegradable sleeve provides significantly higher long-term stability. Especially the differences determined under torsional loading in this study may have clinical relevance. The ASLS permits the potential to decrease complications like secondary loss of reduction and mal-/non-union.
authors: Department of Trauma-, Hand- and Reconstructive Surgery, Friedrich Schiller University Jena, Erlanger Allee 101, Jena 07747, Germany. Dirk.Waehnert@ukmuenster.de
authors: Dirk
authors: D
authors: Wähnert
authors: Yves
authors: Y
authors: Stolarczyk
authors: Konrad L
authors: KL
authors: Hoffmeier
authors: Michael J
authors: MJ
authors: Raschke
authors: Gunther O
authors: GO
authors: Hofmann
authors: Thomas
authors: T
authors: Mückley
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D001696:Biomechanical Phenomena; D001858:Bone Nails; D001863:Bone Screws; D019544:Equipment Failure Analysis; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D008422:Materials Testing; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D013314:Stress, Mechanical; D013552:Swine; D013978:Tibial Fractures / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D054159:Torsion, Mechanical