title: [Biomechanical research of less invasive stabilization system and dynamic condylar screw in fixing subtrochanteric fractures of femur].
abstract: OBJECTIVE
  To compare the biomechanical characteristics of the less invasive stabilization system (LISS) and the dynamic condylar screw (DCS) in the fixation of subtrochanteric fractures of the femur so as to provide theoretical basis for choosing internal fixator in clinical application.
  
  
  METHODS
  Twelve cadaveric human femurs (35-50 years old) were selected with similar proximal femur, excluding deformities, fractures, and other lesions. The twelve femur specimens were randomly divided into 2 groups, 6 specimens per group. An 1 cm gap of osteotomy model was made in the proximal femur up to 1 cm below the lesser trochanter to simulate a comminuted subtrochanteric fracture of femur, and the distal end was embedded with denture acrylic and liquid for denture acrylic. Fracture was fixed by LISS in group A, and was fixed by DCS in group B. The specimens were fixed on Instron-8874 servo-hydraulic mechanical testing machine in a single-leg standing position, and the axial compression test and dynamic fatigue test were carried out to compare the compressive strength and the strain distribution at both sides of the fracture line.
  
  
  RESULTS
  Axial compression test: the strain values of the 2 strain gauges in group A were significantly smaller than those in group B (P < 0.01); the vertical down displacement of the femoral head in group A was significantly smaller than that in group B (P < 0.01) under the same load; when the load was 600 N, the axial rigidity of group A was (209.06 +/- 18.63) N/mm, which was significantly higher than that of group B [(65.79 +/- 7.26) N/mm] (t = 3.787, P = 0.004). Dynamic fatigue test: the vertical down displacement of the femoral head in group A was significantly smaller than that in group B in the same cyclic loading cycle (P < 0.01); when the vertical down displacement of the femoral head was 0.5 mm, the force and the cyclic loading cycles in group A were significantly larger than those in group B (P < 0.01).
  
  
  CONCLUSIONS
  LISS, which has good mechanical stability, can meet the requirements for subtrochanteric fracture of femur fixation in biomechanics and anatomical structures. It can be proven that the LISS internal fixator is firmer than the DCS internal fixator by biomechanical comparison.
authors.affiliation: Department of Orthopedics, Tianjin Hospital, Tianjin 300211, PR China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.forename: Xinlong
authors.initials: X
authors.lastname: Ma
authors.forename: Jianxiong
authors.initials: J
authors.lastname: Ma
authors.forename: Shaowen
authors.initials: S
authors.lastname: Zhu
authors.forename: Baoyi
authors.initials: B
authors.lastname: Ma
authors.forename: Shuqing
authors.initials: S
authors.lastname: Ji
authors.forename: Tao
authors.initials: T
authors.lastname: Ma
authors.forename: Yang
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001858:Bone Nails; D001863:Bone Screws; D002102:Cadaver; D005269:Femur / Q000502:physiology* / Q000601:surgery; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006620:Hip Fractures / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D016268:Internal Fixators; D008875:Middle Aged; D008954:Models, Biological; D013314:Stress, Mechanical; D016474:Weight-Bearing