title: Helical cutting as a new method for tendon-lengthening in continuity.
abstract: BACKGROUND
  Additional tendon length is occasionally needed for the surgical reattachment of retracted tendons and for lengthening of intact contracted tendons. To achieve additional length with use of established techniques such as z-plasty, the tendon is completely transected and loses continuity. The purpose of this study was to develop a new method to increase the potential range of attainable tendon length while preserving a degree of tendon continuity.
  
  
  METHODS
  Forty Achilles tendons (thirty-five study tendons and five reference tendons) were harvested from freshly slaughtered calves. Thirty of the forty tendons were cut along a helical axis located at the tendon centerline, with helical angles of 60°, 45°, and 30°; these tendons either were left unsutured or were sutured with mattress stitches along the cut lines. To provide a performance benchmark, five of the forty tendons were lengthened with use of conventional z-plasty. Five more of the forty tendons were left untreated to serve as a general point of reference. Failure behavior was quantitatively assessed in uniaxial tension.
  
  
  RESULTS
  Standard z-plasty yielded a mean length increase (and standard deviation) to 172% ± 10% of the original length, with a mean tensile strength of 70 ± 15 N. With use of helical cutting, a wide range of lengths and strengths were achieved, depending on the helical angle. A maximal length increase (279% ± 80% of the original length) was achieved with a cut angle of 30°, with an associated load to failure of 30 ± 7.6 N. In tendons cut helically with an angle of 60°, a length of 212% ± 29% was achieved, with a corresponding load to failure of 222 ± 62 N.
  
  
  CONCLUSIONS
  Helical cutting reliably leaves the tendon in continuity, allows more lengthening than that which can be achieved with z-plasty, and can offer improved resistance to tensile loads.
authors.affiliation: Department of Orthopaedics, University Hospital Balgrist, Forchstrasse 340, 8008 Zürich, Switzerland. mazda.farshad@balgrist.ch
authors.forename: Mazda
authors.initials: M
authors.lastname: Farshad
authors.forename: Christian
authors.initials: C
authors.lastname: Gerber
authors.forename: Jess G
authors.initials: JG
authors.lastname: Snedeker
authors.forename: Dominik C
authors.initials: DC
authors.lastname: Meyer
mesh_terms: D000125:Achilles Tendon / Q000601:surgery*; D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D066298:In Vitro Techniques; D008433:Mathematics; D058971:Tenotomy / Q000379:methods*; D013718:Tensile Strength