Genu Valgum, Pediatrics Treatment & Management

For the child with specific and identifiable bone dysplasia, medical treatment may have an important role, influencing the outcome. For example, the child with vitamin D–resistant rickets should be on appropriate medication to optimize bone formation and mineralization. Likewise, children with osteogenesis imperfecta may benefit from treatment with bisphosphonates to increase bone density and decrease the risk of fractures. Recognizing the need for holistic care, even optimal medical management does not correct preexisting genu valgum. However, treatment may slow the progression of the condition and prevent recurrence. Bracing and physical therapy may provide a temporary reprieve of symptoms, but they do not afford long-term symptomatic relief.

Having concluded that osteotomy should be reserved as a salvage option (or for mature patients), an opportunity arises to safely use guided growth as treatment. Despite the age of the child or the etiology of the valgus, even children with "sick physes" may be well served by the application of an extraperiosteal 2-hole plate at the apex (or apices) of the deformity. The ensuing growth should correct the deformity within an average of 12 months. This is documented with quarterly follow-up evaluations, including full-length radiographs with the legs straight.

When the mechanical axis has been restored to neutral, the implants are removed. Growth should be monitored because if the valgus recurs, guided growth may need to be repeated. The goal is to correct the deformity, which alleviates the pain and gait disturbance and protects the knee throughout the growing years. If this requires repeated, yet minor, intervention, the benefits still outweigh the cost and risks of (sometimes) repeated osteotomies.

The importance of recognizing the difference between physiologic and pathologic valgus and reserving treatment for the latter cannot be overemphasized. Consider the symptoms and document the degree and progression of genu valgum before considering surgical intervention. Apart from encroaching skeletal maturity, time is not of the essence here. The patient's height should be recorded, along with the limb lengths and the IMD, measured with the patient standing with his or her knees touching.

Preoperative planning should be undertaken using the full-length radiographs to select the optimal solution, predict the outcome, and convey this information to the family. When considering guided growth, it is prudent to address any significant valgus deformity at its primary site(s) to preserve a horizontal knee axis while neutralizing the mechanical axis so that it bisects the knee. For idiopathic genu valgum, the distal femur is the preferred site of plate application, while for various skeletal dysplasias and metabolic problems, both femur and tibia may be appropriate plating sites. Only one plate is needed per level, serving as a tension band (compression of the physis is not the principle here).

Remember to evaluate sagittal alignment of the knee; these deformities may be addressed simultaneously. For example, a flexion/valgus or oblique-plane deformity of the knee may be resolved by anteromedial femoral plate application; likewise, flexion/varus warrants a single anterolateral plate. For fixed-knee flexion deformities (not the topic of this article), 2 plates are used; one is just lateral to the sulcus and one is medial. This permits unobstructed gliding of the patella. Length discrepancies may be corrected by modular guided growth—adding or removing plates as the child grows, so that equal limb lengths are achieved at maturity, without having to resort to distraction osteogenesis.

The patient should be supine on a radiolucent operating table. An image intensifier is used to localize the physes of the distal femur, proximal tibia, or both.

For femoral plating, the medial incision is centered over the adductor tubercle. An oblique incision is made in the vastus medialis fascia, mobilizing this muscle and retracting it anteriorly. The periosteum is left undisturbed to avoid premature physeal closure. A needle is inserted into the medial physis. A titanium 8-plate (Orthofix) is placed over the needle, and the 8-plate is centered on the physis. The extraperiosteal plate is then secured to the bone by first introducing the 1.6-mm. guide pins, epiphyseal first, then metaphyseal. After starter holes are drilled to a depth of 5 mm with the cannulated 3.2-mm drill, the plate is securely attached with 2 of the 4.5-mm. cannulated, self-tapping screws. While the screws do not need to be parallel, they should not violate the physis or the joint. In the sagittal plane, center the plate to avoid an iatrogenic recurvatum (too anterior) deformity.

For the proximal tibia, the medial physis is approached through a separate longitudinal incision and the superficial tibial collateral ligament is split, again leaving the periosteum intact. A needle is inserted, followed by the extraperiosteal 8-plate, which is secured according to the technique described above. The titanium 8-plate comes in 2 sizes, namely 12 or 16 mm (measured from center hole to center hole). They are both low profile and of equal thickness, with a center hole for the needle to allow for accurate placement.

The screws are titanium, cannulated, and self-tapping; they come in 3 lengths, which are 16 mm (for the ankle, wrist, or elbow), 24 mm (often used for the tibia), and 32 mm (for the femur). The plates and screws are painted and color-coded for ease of identification, but the surgeon may mix and match as dictated by the local anatomy. This is intentionally not a locking plate; the principal is to deflect the physis (tension band) rather than overpower it. Thus, it is a paradigm shift and departure from the traditional stapling methodology.

Images of corrected genu valgum in individual patients are provided below:

Following the layered closure, the tourniquet is deflated, and a soft compression dressing is applied to the knee. No immobilization is required; immediate weight bearing is encouraged, and progressive activities are permitted as tolerated. This procedure is routinely accomplished on an outpatient basis, and physical therapy is rarely required.

Guided growth mandates periodic follow-up evaluations (typically at 3-mo intervals) so that the rate of correction can be assessed to determine the optimal timing for plate removal. The parents should be instructed in how to monitor the intermalleolar distance (IMD); overcorrection into varus can be averted if parents are educated and involved. When the knees and ankles touch simultaneously (IMD = 0), a full-length radiograph should be obtained to measure the mechanical axis and limb lengths. The plate(s) should be removed when the mechanical axis is neutral and further growth should be monitored. Guided growth may be safely repeated for angular and/or length discrepancies, according to the needs of the individual patient.

For this meticulous but relatively simple operative procedure, complications are rare. Minimal dissection is involved; therefore, wound-healing problems such as hematoma, infection, or dehiscence are uncommon. If keloid formation is a problem, the scar may be excised at the time of plate removal.

With the switch from staples to the 8-plate, the problems of hardware migration or fatigue have been solved. The screws intentionally diverge with growth; however, this does not require screw exchange. The relatively thin titanium plates conform to the bone and are free to bend with correction (this is rarely observed). Because the bone is not divided, no need exists to wait for healing. This procedure does not place the patient at risk for nonunion, delayed union, compartment syndrome, or neurologic damage, all of which have been reported with osteotomy of the distal femur or proximal tibia/fibula.

The issue of rebound growth remains ill defined. While this was reported with stapling, especially in children younger then 10 years, it seems less common with the plate technique. Perhaps this reflects a different biology; one not applying a rigid construct (multiple staples) to a dynamic physis. The result may reflect a more physiologic response with less propensity for rebound. However, in the event of recurrent deformity, repeat plate application is warranted if rebound growth occurs to the point the mechanical axis drifts into lateral zone 2 or 3. This underscores the need for parental education and periodic follow-up evaluations.

Permanent physeal closure does not occur, provided meticulous care is taken to place (and remove) plates without disturbing the periosteum. In 5 years of plating, including more than 100 children with the full spectrum of diagnoses, this author has yet to observe this complication. Remember that all of these patients would have had 1 or more osteotomies if they had not undergone guided growth.

Provided the aforementioned criteria are met (ie, sufficient growth remaining, careful analysis and preoperative planning, proper staple selection and insertion, periodic follow-up), the results of guided growth are uniformly gratifying. The parents and the surgeon must be patient, however, because growth is a slow process. The immediate satisfaction (carpentry) of osteotomies is supplanted by delayed gratification (gardening). The success of this technique is predicated on skillful harnessing of the inherent power of the growth plate. Even a sick physis can respond, given enough time; this is why the procedure works even in patients with skeletal dysplasias and vitamin D–resistant rickets.^[7]

Patient and family satisfaction are excellent; this is not surprising in light of the fact that, in comparison with osteotomy, guided growth is minimally invasive, relatively painless, cost effective, and less risky. Minimal down time is associated with the procedure, and educational and recreational activities are only temporarily interrupted. Consequently, previous arbitrary guidelines pertaining to minimum age and diagnoses have been abandoned. In this author's opinion, guided growth with the 8-plate has become the treatment of choice for most angular deformities of the knee. Osteotomy can still be performed if guided growth is unsuccessful (or vice versa).

Since stapling was introduced in the 1950s, its popularity has waxed and waned. Some of the failures and criticisms were a direct result of poor technique (wrong staples, periosteal elevation). By the 1970s, this technique had been abandoned by many; even recent review articles and book chapters pertaining to correction of angular deformities or limb length inequality dismiss stapling as a risky, unpredictable, or outmoded technique. The problem is that osteotomies, whether secured by cast or internal or external fixation, are not without occasional serious consequences.

Percutaneous epiphysiodesis, recently popularized, offers the theoretical advantages of a smaller scar and no hardware to retrieve. However, it is not reversible; therefore, the timing must be perfect to avoid overcorrection. This technique, therefore, is limited to use in adolescent patients, in whom the surgeon strives to achieve a neutral mechanical axis at maturity. Determination of bone age is known to be inexact, with an error of ± 1 year. This variation represents a significant source of error in determining the optimal age for permanent epiphysiodesis.

Despite many successes with staples, and in response to its drawbacks of hardware rigidity, migration, and breakage, the author has devised a preferable method for guided growth. This involves the use of a nonlocking 2-hole titanium 8-plate (Orthofix). Applying a single plate per physis, the directional control afforded allows the correction of frontal-, sagittal-, or oblique-plane deformities. This is performed in an outpatient setting, allowing safe and gradual correction of complex, multilevel, and bilateral deformities by harnessing the power of the growth plate. The same device may be used on both large (170 kg) and small (13 kg) patients with diverse pathology. Osteotomy may be reserved for mature patients or those who require additional length or rotational correction.