To evaluate the operative treatment of Blount disease using the TSF external fixator and to evaluate the system.

During January 2004 and August 2008, 8 males and 2 females with Blount disease (16 limbs) were treated using TSF system. For the radiological assessment we obtained standard long-leg standing radiographs and we measured the anatomic medial proximal tibial angle (aMPTA), the diaphyseal-metaphyseal tibial angle (Drennan), and the femoro-tibial angle.

The mean follow-up was 29 months (15 to 45). No patient had pain around the knee, medial or lateral instability. The range motion of the knee immediately after frame removal was 10° to 90° of flexion in two patients while in the other it was from 0° to 110°. The mean leg-length discrepancy was reduced postoperatively from mean 1,9 cm (1,7–3,2) to 0,9 cm (0− +1,5). The aMPTA angle increased from mean 73° (59°– 83°) to 94° (107°–90°), Drennan angle from 17° (14°–22°) to 3° (0°–7°), and femoro-tibial angle from 17° (10°–30°) varus to 7° (2°–10°) valgus. The frame was removed at mean 9 weeks (7–14). Two patients had delayed union, two presented with loss of correction (due to dissociation of struts and secondary to medial physeal bar), two patients had pin track infection. No neurologic complications were referred.

Accurate corrections of multiplanar deformities as varus, internal rotation and shortening of the limb that coexist in Blount disease may be accomplished using TSF system