title: The anatomic reconstruction of acromioclavicular joint dislocations using 2 TightRope devices: a biomechanical study.
abstract: BACKGROUND
  For the reconstruction of acromioclavicular (AC) joint separation, several operative procedures have been described; however, the anatomic reconstruction of both coracoclavicular ligaments has rarely been reported.
  
  
  OBJECTIVE
  The aim of this biomechanical study is to describe a new procedure for anatomic reconstruction of the AC joint.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Forty fresh-frozen cadaveric shoulders were tested. Cyclic loading and a load-to-failure protocol was performed in vertical (native, n = 10; reconstructed, n = 10) and anterior directions (native, n = 10; reconstructed, n = 10) on 20 AC joints and repeated after anatomic reconstruction. Reconstruction of conoid and trapezoid ligaments was achieved by 2 TightRope devices (Arthrex, Naples, Florida). Dynamic, cyclic, and static loading until failure in vertical (n = 5) and horizontal (n = 5) directions were tested in native as well as reconstructed joints in a standardized setting.
  
  
  RESULTS
  The native coracoclavicular ligaments in static load for vertical force measured 598 N (range, 409-687), elongation 10 mm (range, 6-14), and stiffness 99 N/mm (range, 67-130); static load for anterior force was 338 N (range, 186-561), elongation 4 mm (range, 3-7), and stiffness 140 N/mm (range, 70-210). The mean maximum static load until failure in reconstruction for vertical force was 982 N (range, 584-1330) (P =.001), elongation 4 mm (range, 3-6) (P < .001), and stiffness 80 N/mm (range, 66.6-105) (P = .091); and for anterior static force 627 N (range, 364-973) (P < .001), elongation 6.5 mm (range, 4-10) (P = .023), and stiffness 78 N/mm (range, 46-120) (P = .009). During dynamic testing of the native coracoclavicular ligaments, the mean amount of repetitions (100 repetitions per stage, stage 0-100 N, 100-200 N, 200-300 N, etc, and a frequency of 1.5 Hz) in native vertical direction was 593 repetitions (range, 426-683) and an average of 552 N (range, 452-683) load until failure. In vertical reconstructed testing, there were 742 repetitions (range, 488-893) (P = .222) with a load until failure of 768 N (range, 486-900) (P = .095). In the anterior direction load, the native ligament failed after an average of 365 repetitions (range, 330-475) and an average load of 360 N (range, 307-411), while reconstructed joints ended in 549 repetitions (range, 498-566) (P = .008) with a load until failure of 547 N (range, 490-585) (P = .008). In all testing procedures, a preload of 5 N was performed.
  
  
  CONCLUSIONS
  The anatomic reconstruction of the AC joint using TightRope is a stable and functional anatomic reconstruction procedure. The reconstruction technique led to favorable in vitro results with equal or even higher forces than native ligaments.
  
  
  CONCLUSIONS
  Through anatomic repair, stable function of the AC joint can be achieved in an anatomic manner.
authors.affiliation: Clinical Trial Unit, University Hospital Basel, Basel, Switzerland. lwalz@gmx.de
authors.forename: Lars
authors.initials: L
authors.lastname: Walz
authors.forename: Gian M
authors.initials: GM
authors.lastname: Salzmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Fabbro
authors.forename: Stefan
authors.initials: S
authors.lastname: Eichhorn
authors.forename: Andreas B
authors.initials: AB
authors.lastname: Imhoff