title: Percutaneous epiphysiodesis in the proximal tibia by a single-portal approach: evaluation by radiostereometric analysis.
abstract: OBJECTIVE
  We modified the method for tibial epiphysiodesis by solely using a lateral approach to the physis. From this small-incision approach, the lateral as well as the medial part of the tibial physis were ablated. The aim of our study was to see if this operative technique might be as effective as a bilateral approach, and reduce the operation time and usage time of the image intensifier. The epiphysiodeses were monitored by radiostereometric analysis (RSA), which is a well-established method for the analysis of micro movements and has been used to monitor percutaneous epiphysiodesis with the bilateral approach. There are no reports in the literature comparing single- with double-portal approaches for percutaneous epiphysiodesis evaluated by RSA.
  
  
  METHODS
  Twenty children were treated by percutaneous epiphysiodesis for leg length discrepancies ranging from 15 to 70 mm, comprising 14 boys and 6 girls with a mean age of 13 (11-15) years. The timing of epiphysiodesis was determined by using Moseley's straight-line graph and Paley's multiplier method. For the tibial epiphysiodesis, ten patients were operated with a single surgical approach from the lateral side (Group I) and ten patients were operated with a surgical approach from both the medial and the lateral sides (Group II). The percutaneous epiphysiodesis was monitored by RSA, a method which allows analysis of the three-dimensional dynamics of the epiphysis relative to the metaphysics. RSA examinations were performed postoperatively and after 6 weeks, 12 weeks, and 6 months.
  
  
  RESULTS
  From 0 to 6 weeks after epiphysiodesis, the mean longitudinal growth across the operated physis in the tibia in Group I was 0.26 (0.01-0.6) mm. In Group II, the mean growth for the first 6 weeks after surgery was 0.17 (0.01-0.5) mm. During the time period from 6 weeks to 12 weeks after surgery, there was a mean growth of 0.06 (0.00-0.18) mm in Group I and 0.03 (0.00-0.2) mm in Group II. The mean growth from 0 to 6 weeks after epiphysiodesis for all patients was 0.22 mm, which corresponds to 30 % of the normal growth rate. From 6 to 12 weeks, the mean growth for all patients was 0.046 mm, i.e., 6 % of the normal growth rate. From 12 weeks to 24 weeks, no significant growth across the operated physis was observed in neither Group I nor Group II. The mean surgical time was 26 (21-30) min in Group I and 43 (35-48) min in Group II. This difference was statistically significant (p = 0.006). The mean time for use of the image intensifier during surgery was 202 (191-236) s in Group I and 229 (185-289) s in Group II (p = 0.013).
  
  
  CONCLUSIONS
  In our study, a single-portal technique from the lateral side for percutaneous epiphysiodesis of the proximal tibia was as effective as the double-portal technique. Actual growth arrest appeared within 12 weeks after surgery. A single-portal technique for epiphysiodesis of the tibia is a safe technique, with less surgical time and less time for image intensification compared to the double-portal technique.
authors.affiliation: Department of Children's Orthopaedics and Reconstructive Surgery, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0027 Oslo, Norway.
authors.forename: Joachim
authors.initials: J
authors.lastname: Horn
authors.affiliation: Department of Radiology, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0027 Oslo, Norway.
authors.forename: Ragnhild Beate
authors.initials: RB
authors.lastname: Gunderson
authors.affiliation: Department of Children's Orthopaedics and Reconstructive Surgery, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0027 Oslo, Norway.
authors.forename: Anders
authors.initials: A
authors.lastname: Wensaas
authors.affiliation: Department of Children's Orthopaedics and Reconstructive Surgery, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0027 Oslo, Norway.
authors.forename: Harald
authors.initials: H
authors.lastname: Steen
keywords: Epiphysiodesis; Leg length discrepancy; Percutaneous epiphysiodesis; RSA; Radiostereometric analysis; Single-approach epiphysiodesis