Epiphysiodesis involves either removing the growth plate or taking it and modifying it before reinsertion.  Prophylactic Fixation involves inserting a metal into the bone.  A cannulated screw has a hollow central shaft.

Persisting Growth After Prophylactic Single-Screw Epiphysiodesis in Upper Femoral Epiphysis.

“Prophylactic fixation of the contralateral hip in cases of slipped upper femoral epiphysis is controversial. Using a single-cannulated screw has been widely accepted. Differing reports exist on the occurrence of persisting growth after prophylactic epiphysiodesis. The aim of this study was to evaluate the presence of persisting growth of the upper femoral epiphysis after prophylactic fixation.
From 2006 until 2009, 11 children underwent prophylactic pinning using a single-cannulated 6.5-mm cancellous screw. Time to fusion, persisting growth, and overgrowing of the screw were measured on plain radiographs taken postoperatively and at least after the growth plate was fused.
All patients except 1 (91%) showed a persisting growth of the epiphysis, and in 2 cases a hardware replacement was necessary. The mean increase of the femoral neck length was 8.2% (SEM 1.46%). Mean follow-up was 37 months (range, 12 to 49 mo). All patients had a Risser sign grade 0 at the time of surgery, and equal or less than grade 3, when the growth plate was fused{Riser 5 equals cessation of growth}.
Prophylactic fixation using a single-cannulated cancellous screw showed in our series growth persistence was the rule and in some cases the physeal overgrowth necessitates a hardware replacement.”

“After placing the guidewire under fluoroscopic guidance in a central position and drilling with a 5.0-mm drill just over the proximal femoral growth plate, the insertion of the 6.5-mm cannulated cancellous screw was carried out through a 0.5-inch incision.”

“The mean increase of femoral neck length at the time of physeal closure in patients without further surgeries was 8.6%, 7.5% in the 16mm threaded group and 10% in the 32mm threaded group.”<-The bigger the screw the larger the overgrowth.

Maybe placing a screw in adult bone will also cause a length increase?