title: Fatigue Failure in Extra-Articular Proximal Tibia Fractures: Locking Intramedullary Nail Versus Double Locking Plates-A Biomechanical Study.
abstract: OBJECTIVE
  The goal of this study is to compare the fatigue strength of a locking intramedullary nail (LN) construct with a double locking plate (DLP) construct in comminuted proximal extra-articular tibia fractures.
  
  
  METHODS
  Eight pairs of fresh frozen cadaveric tibias with low bone mineral density [age: 80 ± 7 (SD) years, T-score: -2.3 ± 1.2] were used. One tibia from each pair was fixed with LN, whereas the contralateral side was fixed with DLP for complex extra-articular multifragmentary metaphyseal fractures (simulating OTA 41-A3.3). Specimens were cyclically loaded under compression simulating single-leg stance by staircase method out to 260,000 cycles. Every 2500 cycles, localized gap displacements were measured with a 3D motion tracking system, and x-ray images of the proximal tibia were acquired. To allow for mechanical settling, initial metrics were calculated at 2500 cycles. The 2 groups were compared regarding initial construct stiffness, initial medial and lateral gap displacements, stiffness at 30,000 cycles, medial and lateral gap displacements at 30,000 cycles, failure load, number of cycles to failure, and failure mode. Failure metrics were reported for initial and catastrophic failures.
  
  
  RESULTS
  DLP constructs exhibited higher initial stiffness and stiffness at 30,000 cycles compared with LN constructs (P < 0.03). There were no significant differences between groups for loads at failure or cycles to failure.
  
  
  CONCLUSIONS
  For the fixation of extra-articular proximal tibia fractures, a LN provides a similar fatigue performance to double locked plates. The locked nail could be safely used for fixation of proximal tibia fractures with the advantage of limited extramedullary soft tissue damage.
authors.affiliation: Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA.
authors.forename: Utku
authors.initials: U
authors.lastname: Kandemir
authors.forename: Safa
authors.initials: S
authors.lastname: Herfat
authors.forename: Mary
authors.initials: M
authors.lastname: Herzog
authors.forename: Paul
authors.initials: P
authors.lastname: Viscogliosi
authors.forename: Murat
authors.initials: M
authors.lastname: Pekmezci
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D019544:Equipment Failure Analysis; D005260:Female; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D017276:Friction; D006801:Humans; D008297:Male; D009038:Motion; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D013718:Tensile Strength; D013978:Tibial Fractures / Q000503:physiopathology* / Q000601:surgery*