Blount’s disease in children is an excessive bowing or curvature of the lower legs. If they don’t grow out of the condition, surgery may be needed to correct the deformity. Treatment is needed to improve alignment of the bone and keep an even leg length from side to side.
Once the repair has been made, the next step is to hold the bone in that position as it grows and lengthens. There are several ways to do this. The two devices you saw are likely the EBI external fixator and the Taylor Spatial frame.
The EBI is anchored to the bone with pins and clamps. It has a series of multiaxial joints that can be adjusted to change the curve, rotation, and length of the bone. The surgeon uses careful fluoroscopic (special X-ray) measurements and computer calculations to fix the device in just the right spot.
The disadvantages of this system are problems can occur from the pins if they get infected or if they damage nerves or blood vessels. If the device isn’t fixed in just the right position, a second operation may be needed to make necessary changes.
The second device (the Taylor frame) is a circular frame that fits around the lower leg. It has a series of interconnected struts that can be pulled and tightened to adjust the leg position. Any changes can be made without surgery. The advantage is the correction is more accurate and safe. The disadvantage is the correction is more gradual and may take longer.