Length changes in tibial osteotomy with angular correction.

Twelve boys, aged 11-17 years, who underwent percutaneus proximal tibial osteotomy with acute angular correction and application of external fixator for unilateral Blount's disease were retrospectively reviewed. Preoperative radiographs were compared with radiographs at healing to evaluate changes in tibial length and overall limb length. Angular correction increased overall limb length by a mean of 1.4 cm (range -0.4 cm to 3.2 cm). This increase was a mean 0.7 cm less than was predicted by adding the preoperative tibial and femoral lengths. This failure to achieve the predicted limb length occurs due to shortening in the tibia and should be considered when planning an osteotomy.