title: Percutaneous epiphysiodesis using transphyseal screws in the management of leg length discrepancy: optimal operation timing and techniques to avoid complications.
abstract: BACKGROUND
  Percutaneous epiphysiodesis using transphyseal screws (PETS) has been used to manage leg length discrepancy (LLD) in growing children. The purposes of this study were to analyze effects of PETS on LLD, its associated complications, to determine optimal operation timing, and find ways of preventing complications.
  
  
  METHODS
  The data of 59 patients obtained up to screw removal or at skeletal maturity were retrospectively analyzed. Retrospective growth calculations were done using multiplier method. The efficacy of LLD correction was calculated, and the predicted segment length with the index operation was compared with the final measured length and final LLD was measured. The screw insertion angle in 3-dimension was calculated, and it was correlated with the efficacy. Complications associated with screw design and the techniques used were analyzed.
  
  
  RESULTS
  The LLD correction efficacy averaged 75.5% (5.0 to 114.0) at the distal femur and 78.9% (11.0 to 111.0) at the proximal tibia. However, mean final LLD was 3.0 mm (range, -10.0 to 16.7 mm), presumably because operations were performed on average 1.3 years earlier than estimated by growth calculation. Three-dimensional screw insertion angle was positively correlated with LLD correction efficacy. Complications were closely related to the screw design and the implantation techniques.
  
  
  CONCLUSIONS
  PETS provides a minimally invasive and effective means of LLD correction. In view of its delayed effect, we recommend that PETS be performed at least 1 year earlier than estimated optimal epiphysiodesis timing. The careful selection of screw design and length and accurate screw placement are the keys to successful results.
  
  
  METHODS
  Level IV prognostic studies.
authors: *Department of Orthopaedic Surgery, Jeju National University Hospital, Jeju †Division of Pediatric Orthopaedics, Seoul National University Children's Hospital, Seoul ‡Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Seongnam, Republic of Korea.
authors: Mi Hyun
authors: MH
authors: Song
authors: Eun-Seok
authors: ES
authors: Choi
authors: Moon Seok
authors: MS
authors: Park
authors: Won Joon
authors: WJ
authors: Yoo
authors: Chin Youb
authors: CY
authors: Chung
authors: In Ho
authors: IH
authors: Choi
authors: Tae-Joon
authors: TJ
authors: Cho
mesh_terms: D000293:Adolescent; D001852:Bone Lengthening / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D001863:Bone Screws / Q000009:adverse effects / Q000592:standards; D002648:Child; D004838:Epiphyses / Q000601:surgery*; D005260:Female; D006801:Humans; D007866:Leg / Q000601:surgery; D007870:Leg Length Inequality / Q000601:surgery*; D008297:Male; D019060:Minimally Invasive Surgical Procedures; D011183:Postoperative Complications / Q000517:prevention & control*; D011379:Prognosis; D012189:Retrospective Studies; D061665:Time-to-Treatment; D016896:Treatment Outcome