title: Gap formation in transpatellar patellar tendon repair: pretensioning Krackow sutures versus standard repair in a cadaver model.
abstract: BACKGROUND
  Postfixation loosening within the Krackow stitch-tendon construct may be associated with gap formation in patellar tendon repair.
  
  
  OBJECTIVE
  Pretensioning the Krackow stitch-tendon construct decreases postfixation gap formation in transpatellar patellar tendon repair.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Patellar tendon rupture was simulated in 8 pairs of cadaveric knees. Standard manual traction was used in all specimens to remove Krackow stitch slack. In the experimental group, specimens were pretensioned with a simulated active concentric quadriceps contraction with cycling of the knee 10 times from 90 degrees to 5 degrees of flexion. All specimens were then cycled at 0.25 Hz from 90 degrees to 5 degrees for 1000 cycles until failure, which was defined as 3 or 5 mm of gap formation.
  
  
  RESULTS
  A 3-mm gap occurred at 1 cycle (mean, 3.5 mm) and 35 cycles (4.0 mm) in the control and experimental groups, respectively. Gapping of 5 mm occurred at 35 (5.9 mm) and 100 cycles (5.0 mm) in the control and experimental specimens, respectively. Gap formation was smaller in the experimental group through 100 cycles (P < .05).
  
  
  CONCLUSIONS
  Gapping was lower with pretensioning in the early cycling stages. However, significant gapping occurred in both groups with repetitive concentric active loading ranging from 90 degrees to 5 degrees of flexion.
  
  
  CONCLUSIONS
  Tightening of the Krackow stitch as done in this study does not result in a clinically important decrease in gapping. This observation may be generalizable to other applications of the Krackow stitch.
authors.affiliation: Department of Orthopaedic Surgery, The Union Memorial Hospital, Baltimore, MD 21218, USA.
authors.forename: Erik M
authors.initials: EM
authors.lastname: Krushinski
authors.forename: Brent G
authors.initials: BG
authors.lastname: Parks
authors.forename: Richard Y
authors.initials: RY
authors.lastname: Hinton
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D008297:Male; D008422:Materials Testing; D019637:Orthopedic Procedures / Q000295:instrumentation / Q000379:methods*; D017847:Patellar Ligament / Q000601:surgery*; D019651:Plastic Surgery Procedures / Q000295:instrumentation / Q000379:methods; D053441:Suture Anchors; D013708:Tendon Injuries / Q000601:surgery*; D013718:Tensile Strength; D013977:Tibia / Q000601:surgery; D013997:Time Factors; D016474:Weight-Bearing