Hemiepiphysiodesis (henceforth referred to as guided growth) is a minimally invasive surgical technique that permits the correction of simple or complex angular deformities of the skeletally immature limb. Correction is attained gradually through growth, without the attendant risks and costs incurred by osteotomy. The concept was first introduced in 1933 by Phemister, who elevated the periosteum and rotated a bone block. Soon thereafter, instrumented and potentially reversible techniques were introduced, using wire loops (Haas) or Vitallium staples (Blount) to achieve the same correction. The latter technique was practiced for decades, but its popularity eventually waned in favor of more modern and versatile methods. While there are some proponents of the PETS (percutaneous epiphysiodesis using transphyseal screws) technique, described by Metaizeau, currently the most popular method worldwide is the use of an extraperiosteal tension band plate. This chapter will focus upon guided growth for the correction of angular deformities employing nonlocking, two-hole plates.

An attractive feature of guided growth is that, with few exceptions (such as encroaching skeletal maturity), intervention is not time sensitive. Because guided growth is reversible, the timing of surgery is elective and does not require precise calculation—a major advantage of this technique over other techniques. Once the surgeon obtains a detailed history, including the duration and age of onset, functional limitations, prior treatment, and family history, he or she should carefully observe the gait pattern. The magnitude and direction of deformity should be noted, along with symmetry (or lack thereof), limb lengths, and spinal deformity. A neuromuscular examination should be undertaken, and concomitant rotational deformities, ligamentous laxity, patellar instability, or joint contracture should be sought and documented. If it is unclear as to whether a given deformity is physiologic or pathologic (such as genu varum in a toddler), then surgery may be postponed pending periodic reevaluation. For example, if one is inclined to observe the impact of bracing (Blount disease) or medication (rickets, osteogenesis imperfecta), in lieu of surgical intervention, there is ample time to continue monitoring. With respect to the gait alterations, it is common for children with progressive genu valgum to manifest a circumduction pattern, in order to clear the stance limb with the swinging limb. This pattern has an adverse effect upon the kinematics of gait (Fig. 30-1A). While plain radiographs demonstrate relative limb lengths and the angular deviation, they do not tell the whole story. In select cases, the Hueter-Volkmann effect upon the adjacent bone may be demonstrated on MRI (Fig. 30-1B).

In contradistinction to genu valgum, children with genu varum often present with associated intoeing and, in some cases, a waddling gait. This observation would suggest that the seemingly simple, and readily documented, frontal plane deformities are compounded by transverse plane deformities including femoral and/or tibial torsion. The latter are insidious, occurring through the physis. Frequently, if one corrects the frontal plane deformity by hemiepiphysiodesis, there is a serendipitous improvement in the rotational profile. This means that it is not necessary to resort to osteotomy, in order to effect rotational correction. Patience on the part of the surgeon (and the informed parents) will yield satisfaction in most cases and osteotomy can be avoided accordingly.

Radiographic assessment should include a weight-bearing, full-length, anteroposterior (AP) view of the legs with the patellae neutral. If there is a perceived length discrepancy, it is helpful to level the pelvis with blocks. Lateral radiographs of the extremities are warranted, as is consideration of a Merchant or similar patellar view if there are anterior knee pain symptoms.