title: Comparative biomechanical study of reversed less invasive stabilization system and proximal femoral nail antirotation for unstable intertrochanteric fractures.
abstract: OBJECTIVE
  Unstable intertrochanteric fractures (ITFs) are mostly treated by proximal femoral nail antirotation (PFNA), Inter-Tan, Asian Hip, and other new internal fixation devices. But for complex unstable fractures, such as crushed lateral wall of the greater trochanter, the loss of fixation point on lateral wall slightly reduces the fixing effect. This study aimed to compare the biomechanical strengths between reversed less invasive stabilization system (LISS) and PFNA for treatment of unstable ITFs.
  
  
  METHODS
  Forty synthetic femurs were used to simulate unstable ITFs in vitro and were fixed using the reversed LISS or PFNA. These fractures were divided into two groups depending on whether the lateral wall of the greater trochanter is intact or not (AO classification: 31-A2.3 and 31-A3.3, respectively). The load-displacement of femur, stiffness, ultimate load, and cyclic fatigue resistance were detected using an incremental load test and a dynamic fatigue test through an MTS 858 test system.
  
  
  RESULTS
  For both 31-A2.3 and 31-A3.3, the vertical sinking displacement (VSD) of the femoral head under 500 N load was insignificantly smaller after treatment with reversed LISS than with PFNA, and when the displacement was 5 mm, the femoral head bore insignificantly greater load. The fixation with reversed LISS resulted in greater axial stiffness of the femur but smaller ultimate load. During the same cycle in the dynamic fatigue test, the VSD was insignificantly smaller with the fixation of reversed LISS.
  
  
  CONCLUSIONS
  Reversed LISS and PFNA have similar biomechanical strength for unstable ITFs. This conclusion should be supported by additional large-size research on basic biomechanics and clinical application. This is the first comparative biomechanical study comparing reversed LISS and PFNA for unstable ITFs.
authors.affiliation: Department of Orthopedics, China-Japan Friendship Hospital, Beijing 100029, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Graduate School, Beijing University of Chinese Medicine, Beijing 100029, China.
authors.forename: Shouyao
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Orthopedics, China-Japan Friendship Hospital, Beijing 100029, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Lin
authors.affiliation: Department of Orthopedics, China-Japan Friendship Hospital, Beijing 100029, China. Email: yunting1118@sina.com.
authors.forename: Yunting
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, Ji Shui Tan Hospital, Beijing 100035, China.
authors.forename: Jinhui
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, Ji Shui Tan Hospital, Beijing 100035, China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Tao
authors.affiliation: Department of Graduate School, Beijing University of Chinese Medicine, Beijing 100029, China.
authors.forename: Rongrong
authors.initials: R
authors.lastname: Cai
mesh_terms: D001696:Biomechanical Phenomena; D001858:Bone Nails; D005269:Femur / Q000601:surgery; D005593:Fracture Fixation, Internal / Q000379:methods; D005594:Fracture Fixation, Intramedullary / Q000379:methods; D006620:Hip Fractures / Q000601:surgery*; D006801:Humans