title: Biomechanical study on the effect of twisted human patellar tendon.
abstract: OBJECTIVE
  To compare the stiffness and maximum strength between the untwisted and twisted free-tendon.
  
  
  METHODS
  22 twisted and untwisted sectioned-specimens of human cadaver patellar tendons were used and pulled to failure to obtain load-deformation profiles from which stiffness, maximum load to failure and elastic elongation limit were derived.
  
  
  BACKGROUND
  In the reconstruction of the deficient anterior cruciate ligament, the use of the central one-third of the patellar tendon is a well-established procedure in which, prior to insertion, the tendon graft may be twisted to mimic the natural orientation of the anterior cruciate ligament in the knee joint.
  
  
  RESULTS
  The untwisted tendons had a mean stiffness of 36.5 kg/mm (SD, 16.6 kg/mm) and maximum load of 165.9 kg (SD, 86.8 kg). With a 90 degrees twist, the average stiffness of the twisted tendon was 66.5 kg/mm (SD, 25.4 kg/mm), with maximum load at 364.5 kg (SD, 109.9 kg), an increase of over 100%. The elastic elongation limit, or allowable elongation before permanent deformation or failure, was significantly larger in twisted tendons by 35%.
  
  
  CONCLUSIONS
  Twisting increased the resistance to deformation of the tendon in this study. Relevance  The finding supports the surgical practice of pre-twisting tendon grafts for anterior cruciate ligament reconstruction, based on the premise that a stronger and stiffer graft provides a more favourable outcome.
authors.affiliation: Faculty of Medicine, Department of Orthopaedic surgery, National University of Singapore, Lower Kent Ridge Road, 119074, Singapore.
authors.forename: A
authors.initials: A
authors.lastname: Thambyah
authors.forename: P
authors.initials: P
authors.lastname: Thiagarajan
authors.forename: J C
authors.initials: JC
authors.lastname: Goh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D004548:Elasticity; D006801:Humans; D008875:Middle Aged; D017847:Patellar Ligament / Q000033:anatomy & histology / Q000502:physiology*; D018583:Pliability; D012421:Rupture; D013223:Statistics as Topic; D013314:Stress, Mechanical; D019415:Torque