title: Biomechanical study of unilateral pedicle screw combined with contralateral translaminar facet screw in transforaminal lumbar interbody fusion.
abstract: BACKGROUND
  The biomechanical stability of unilateral pedicle screw (UPS) combined with contralateral translaminar facet screw (TLFS), especially long-term stability, still needs to be compared to traditional UPS or bilateral pedicle screws (BPSs) in details.
  
  
  METHODS
  Twenty-four porcine spines (L2-L5) were tested for flexibility with pure moments of 5Nm under intact status and transforaminal lumbar interbody fusion status using UPS+TLFS, UPS or BPS at L3-L4. After short-term (3cycles) and long-term cyclic loading (18,000cycles), the range of motion was obtained and analyzed for single-level constructs in flexion/extension, lateral bending and axial rotation modes. In addition, the relative displacement of contralateral articular processes was recorded in a real time fashion.
  
  
  RESULTS
  The range of motion was significantly reduced in all instrumented constructs. In all movement directions, UPS+TLFS achieved similar range of motion to BPS after short and long-term loading, which were significantly lower than that in UPS. A significantly larger displacement of contralateral articular process was recorded in UPS than UPS+TLFS and BPS during extension/flexion, lateral bending and axial rotation, suggesting its compromised stability.
  
  
  CONCLUSIONS
  The hybrid construct of UPS+TLFS showed instant and long-term equivalent biomechanical ability to that of traditional BPS, making it an alternative option to BPS that could be less invasive while maintains a stable and effective instrumentation.
authors.affiliation: Department of Orthopaedics, Changhai Hospital, The Second Military Medical University, Shanghai 200433, China.
authors.forename: Beier
authors.initials: B
authors.lastname: Luo
authors.affiliation: Department of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Yan
authors.affiliation: Department of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Jinghui
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Duan
authors.affiliation: Department of Orthopaedic and Spinal Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Department of Orthopaedic and Spinal Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China.
authors.forename: Jianting
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China. Electronic address: zjluo@fmmu.edu.cn.
authors.forename: Zhuojing
authors.initials: Z
authors.lastname: Luo
authors.affiliation: Department of Orthopaedic and Spinal Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China. Electronic address: qinanzhu@gmail.com.
authors.forename: Qingan
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Department of Orthopaedics, Changhai Hospital, The Second Military Medical University, Shanghai 200433, China. Electronic address: limingch@21cn.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D004195:Disease Models, Animal; D005081:Exercise Therapy / Q000295:instrumentation; D005260:Female; D008159:Lumbar Vertebrae / Q000601:surgery*; D008161:Lumbosacral Region / Q000601:surgery; D065289:Pedicle Screws; D011187:Posture; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013552:Swine
keywords: Biomechanics; Facet screw; Pedicle screw; Transforaminal lumbar interbody fusion