Hip Varus Osteotomy (VRO)
Derotation Osteotomy
Femoral Osteotomy

The femur is the thigh bone. At the lower end is the knee. At the upper end is the hip. Look at figures 2, 3, & 4, above. You can see that the femur is angled and ends in a ball shaped top (called the head). The short slanted segment below the "head" is the neck of the femur. You might call the long vertical shaft of the femur, the "body", if you like.

The round head sits in the hip socket (also called the acetabulum). The hip joint is of two halves, the pelvic socket and the ball of the femur.

Problems of the hip can be many.

The socket can be too shallow, too large, too small, lacking proper round contour etc. These problems of plasticity of shape are lumped in a name "dysplasia". That's another page.

In figure 2, we see a problem of the femoral neck. It is too vertical. It does not point toward the socket sufficiently. That is called femoral neck "valgus" (or just plain valgus). The opposite of valgus is varus. In femoral varus the neck would be more horizontal.

The most common femur intervention for cerebral palsied persons, is to deal with a dislocating hip.  In that setting the hip dislocates because the hip socket is too shallow (1) and perhaps the femoral neck too vertical (2 valgus).

Cutting (tome) any bone (osteo) is called osteotomy. Osteotomy of the thigh bone just below the neck, in order to angle the upper femur (the neck) more sharply into the socket is performed at times. The advantage is that a single operation can handle an array of issues. Even if the femur neck angle is proper, a steeper varus angle causes muscles to pull less vertically toward the socket top edge but rather more horizontally toward the socket center.

In fact, most surgeries to produce varus are not to undo excess valgus, but rather to produce more varus than is normal so as to offset less vertically stable sockets.

Often, in order to further stabilize or to redirect the direction of the knee below, the reattachment of the femoral neck back to the body of the femur (with a metal plate and screws) after it has been divided is in an altered horizontal rotation (called derotation or just rotation).

The name VRO means Varus Rotational Osteotomy.
The name VDO means Varus Derotational Osteotomy
They mean about the same thing.

The disadvantage is that this femur surgery shortens the leg, makes it strangely wide at the hip, and causes the leg to track oddly between sitting posture to standing. Bone healing (to standing time) is about 8-12 weeks.  A hip metal 'nail' (a specialized angled metal plate and screw affair) is needed to hold the two pieces of divided femur together until bone healing and takes over. The "nail" is removed about one year later. Loss of position is not rare, requiring potential revision surgery.

Muscle operations are often performed at the same time. Most VROs require a body cast that includes the legs (spica cast).

Anteversion is when the femoral head+neck point too forward relative to the direction of the knee. This is the strongest argument for VRO type surgery.