title: Tendon transfer to unossified bone in a porcine model: potential implications for early tibialis anterior tendon transfers in children with clubfeet.
abstract: OBJECTIVE
  Tibialis anterior tendon transfers (TATT) are commonly performed in young children following Ponseti casting for clubfeet. The classic TATT involves advancing the tendon through a hole drilled in the ossified cuneiform. The aim of this study was to determine if tendons transferred through unossified bones have untoward effects on subsequent bone development.
  
  
  METHODS
  Twenty-five piglets underwent one of five surgical procedures. An 18-gauge needle was then used to place a tunnel through the bony or cartilaginous portion of the calcaneus (through direct visualization) and isolated slips of the flexor digitorum superficialis (FDS) were placed through the tunnels, as determined by surgical procedure. Radiographic and/or histologic evaluations of the calcaneal apophyses were then performed. A discrete (1-4) and dichotomous "Normal" or "Abnormal" scoring system was developed and its reliability assessed to grade the appearance of the calcanei. Calcaneal appearances following the surgical procedures were then compared with controls. The average load to failure of a subset of transferred tendons was then compared using an MTS machine.
  
  
  RESULTS
  The proposed apophyseal grading system (1-4) demonstrated an intraclass correlational coefficient (ICC) for consistency of 0.92 [95% confidence interval (CI) 0.88 < ICC < 0.95] and ICC for agreement of 0.91 (95% CI 0.86 < ICC < 0.95), indicating strong agreement and consistency. Similarly, Fleiss' kappa for the 1-4 scoring system was found to be 0.67, indicating substantial agreement between reviewers. When the 1-4 system was translated into the dichotomous scheme "Normal" and "Abnormal", the kappa value increased to 0.94, indicating strong agreement. Forty-six apophyses (13 control and 33 operative) were assessed using this scoring scheme. Apophyseal transfers were significantly more abnormal than controls (p < 0.0001), while no difference in abnormalities was found following tunnel placement alone (p = 1). Mechanical testing of the tendons transferred to bone or through the cartilaginous apophysis demonstrated no significant differences (p = 0.2).
  
  
  CONCLUSIONS
  Tendon transfers through unossified bones altered subsequent bone development.
  
  
  CONCLUSIONS
  While the long-term consequence of these structural changes is unknown, these findings suggest that tendon transfers through unossified bones should be avoided and alternative methods of tendon fixation explored.
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA. halanski@ortho.wisc.edu.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Halanski
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Sam
authors.initials: S
authors.lastname: Abrams
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Lenhart
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Ellen
authors.initials: E
authors.lastname: Leiferman
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Kaiser
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Pierce
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Rachel Rebekah
authors.initials: RR
authors.lastname: Franklin
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Dayton
authors.initials: D
authors.lastname: Opel
authors.affiliation: American Family Children's Hospital, University of Wisconsin, Madison, WI, USA.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Noonan
authors.affiliation: Department of Animal Science, University of Wisconsin, Madison, USA.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Crenshaw
keywords: Apophysis; Clubfoot; Porcine model; Tendon transfer; Tibialis anterior tendon transfer; Unossified