title: Limb angular deformity correction using Dyna-ATC: surgical technique, calculation method, and clinical outcome.
abstract: OBJECTIVE
  Dyna-ATC is a unilateral external fixator with angulator, lengthener, and translator, which allows for angular correction and compensation of the secondary displacement during angular correction. The purpose of this study is to introduce surgical technique and calculation methods and to evaluate the clinical outcome of angular deformity correction using Dyna-ATC.
  
  
  METHODS
  The amounts of secondary displacement were calculated with the distances between axis of correction of angulation, Center of Rotational Angulation, and osteotomy and the amount of angular deformity. The rate of angular correction was determined to distract the corticotomy at 1 mm/day. Clinical and radiographic evaluation was performed on 13 patients who underwent deformity correction using Dyna-ATC. There were 8 proximal tibia vara, 1 tibia valga, 2 varus and 4 valgus deformities on distal femur. One patient underwent pelvic support femoral reconstruction. Concomitant lengthening was combined in all femur cases. Mean age at surgery was 17.5 years (7 to 64).
  
  
  RESULTS
  All but one achieved bony healing and normal alignment with the index procedure. Mean mechanical axis deviation improved from 31.9 mm to 3.0 mm. The average amount of angular correction was 11.0° on tibiae and 10.0° on femora. The average length gain on femora was 6.4 cm, and the healing index averaged to 1.1 mo/cm. One patient underwent quadricepsplasty and one patient had three augmentation surgeries due to poor new bone formation.
  
  
  CONCLUSIONS
  We believe that Dyna-ATC is a useful alternative to bulky ring fixators for selective patients with angular deformity less than 30 degrees in the coronal plane around the knee joint.
authors.affiliation: Department of Orthopaedic Surgery, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Hoon
authors.initials: H
authors.lastname: Park
authors.forename: Hyun Woo
authors.initials: HW
authors.lastname: Kim
authors.forename: Hui-Wan
authors.initials: HW
authors.lastname: Park
authors.forename: Ki Seok
authors.initials: KS
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D001848:Bone Diseases, Developmental / Q000601:surgery*; D002648:Child; D016267:External Fixators; D005260:Female; D005269:Femur / Q000002:abnormalities / Q000601:surgery; D006801:Humans; D007870:Leg Length Inequality / Q000601:surgery; D038061:Lower Extremity Deformities, Congenital / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D055034:Osteochondrosis / Q000151:congenital / Q000601:surgery; D019857:Osteogenesis, Distraction / Q000295:instrumentation* / Q000379:methods / Q000706:statistics & numerical data; D010027:Osteotomy; D013977:Tibia / Q000002:abnormalities / Q000601:surgery; D016896:Treatment Outcome; D055815:Young Adult