Pediatric Genu Valgum 

Updated: Jan 03, 2019
Author: Peter M Stevens, MD; Chief Editor: Jeffrey D Thomson, MD 

Overview

Background

Genu valgum is the Latin-derived term used to describe knock-knee deformity. Whereas many otherwise healthy children have knock-knee deformity as a passing trait, some individuals retain or develop this deformity as a result of hereditary (see the image below) or genetic disorders or metabolic bone disease.

This 9-year-old patient has symmetrical and progre This 9-year-old patient has symmetrical and progressive genu valgum caused by a hereditary form of metaphyseal dysplasia. One method of treatment is to undertake bilateral femoral and tibial/fibular osteotomies, securing these with internal plates or external frames. However, the hospitalization and the attendant cost and risks, including peroneal nerve palsy and compartment syndrome, make this a daunting task for the surgeon and family alike. Furthermore, mobilization and weightbearing may require physical therapy but must be delayed pending initial healing of the bones.

The typical gait pattern is circumduction, requiring that the individual swing each leg outward while walking in order to take a step without striking the planted limb with the moving limb. Not only are the mechanics of gait compromised but also, with significant angular deformity, anterior and medial knee pain are common. These symptoms reflect the pathologic strain on the knee and its patellofemoral extensor mechanism.

For persistent genu valgum, treatment recommendations have included a wide array of options, ranging from lifestyle restriction and nonsteroidal anti-inflammatory drugs (NSAIDs) to bracing, exercise programs, and physical therapy. In recalcitrant cases, surgery may be advised. No consensus exists regarding the optimal treatment. Some surgeons focus (perhaps inappropriately) on the patella itself, favoring arthroscopic or open realignment techniques. However, if valgus malalignment of the extremity is significant, corrective osteotomy or, in the skeletally immature patient, hemiepiphysiodesis may be indicated.

Osteotomy indications and techniques have been well described in standard textbooks and orthopedic journals and are not the focus of this article. Hemiepiphysiodesis can be accomplished by using the classic Phemister bone block technique, the percutaneous method, hemiphyseal stapling, or the application of a single two-hole plate and screws around the physis. The senior author, having experience in each of these techniques, developed the last of these techniques in order to solve two of the problems sometimes encountered with staples—namely, hardware fatigue and migration.

The focus of this article is on the indications, techniques, complications, and outcome of guided growth using the reversible plate technique for the correction of pathologic genu valgum.

Anatomy

The radiographic parameters relevant to defining genu valgum are best measured on a full-length standing anteroposterior (AP) radiograph of the legs. The angle is measured between the femoral shaft and its condyles (normal angle, 84°); this is referred to as the lateral distal femoral angle. The other relevant angle is the proximal medial tibial angle; this is the angle between the tibial shaft and its plateaus (normal angle, 87°).

The mechanical axis (center of gravity) is a straight line drawn from the center of the femoral head to the center of the ankle; this should bisect the knee. Allowing for variations of normal, an axis within the two central quadrants (zones +1 or –1) of the knee is deemed acceptable.

With normal alignment, the lower-extremity lengths are equal, and the mechanical axis bisects the knee when the patient is standing erect with the patellae facing forward. This position places relatively balanced forces on the medial and lateral compartments of the knee and on the collateral ligaments, while the patella remains stable and centered in the femoral sulcus.

Pathophysiology

With normal alignment, the physes and epiphyses are subjected to physiologic and intermittent compression and tension and, thus, are shielded from pathologic stress. Balanced growth preserves straight legs, symmetrical limb lengths, and normal function. In genu valgum, as the mechanical axis shifts laterally (see the image below), pathologic stress is placed on the lateral femur and tibia, inhibiting growth and possibly leading to a vicious circle.

This diagram depicts genu valgum involving the rig This diagram depicts genu valgum involving the right leg (lighter shade), where the mechanical axis falls outside the knee. The goal of treatment is to realign the limb and neutralize the mechanical axis (dotted red line), thereby mitigating the effects of gravity through guided growth of the femur and/or tibia (whatever is required to maintain a horizontal knee joint axis). The darker shade depicts normal alignment with the mechanical axis now bisecting the knee.

Not only is physeal growth inhibited, but also the Hueter-Volkmann effect is exerted upon the entire hemiepiphysis (lateral femoral condyle), preventing its normal expansion. According to the Hueter-Volkmann principle, continuous or excessive compressive forces on the epiphysis have an inhibitory effect on growth. Consequently, growth in the lateral condyle of the femur is suppressed globally, resulting in a shallow femoral sulcus and a propensity for the patella to tilt and subluxate laterally.

In children younger than 6 years, physiologic genu valgum is common but is self-limiting and innocuous. In children (of any age) with pathologic valgus, when the mechanical axis deviates into or beyond the lateral compartment of the knee, regardless of the etiology, a number of clinical problems may ensue.

Medial ligamentous strain may be associated with recurrent knee pain. The patellofemoral joint may become shallow, incongruous, or unstable, causing activity-related anterior knee pain. In extreme cases, frank patellar dislocation with or without osteochondral fractures may ensue. During gait, medial thrust of the tibia relative to the femur may compromise the integrity of the restraining medial collateral ligaments, resulting in localized pain and progressive joint laxity.

In addition to knee pain and laxity, patients may develop a circumduction gait, swinging each leg outward to avoid knocking their knees together. This gait pattern is awkward and laborious; the patient is unable to run, ride a bicycle, or participate safely and effectively in play or sports activities, potentially leading to social isolation and possible ridicule. Left untreated, the natural history for this condition is likely to be that of inexorable progression and deterioration.

Because patellar dislocation reflects an insidious and progressive growth disturbance, nonoperative management, relying on physical therapy and bracing, is of little value. During the adult years, premature and eccentric stress on the knee may result in hypoplasia of the lateral condyle, meniscal tears, articular cartilage attrition, and arthrosis of the anterior and lateral compartments.

The lifelong valgus knee presents a daunting challenge to the adult reconstructive orthopedist. Total knee arthroplasty may be fraught with complications, including persistent malalignment, neurovascular compromise, patellar instability, and premature loosening of the prosthetic components.

Despite the current availability of sex-specific total knee components, or patellofemoral arthroplasty, these anatomic problems continue to pose a challenge. Therefore, it is in the best interest of the patient for the clinician to try to prevent such an outcome. Correction of genu valgum and neutralization of the forces across the knee are the goals of early and, if necessary, repeated intervention, which forestalls the need for more invasive adult reconstructive procedures.

Etiology

It is well recognized that toddlers aged 2-6 years may have physiologic genu valgum. For this age group, typical features include ligamentous laxity, symmetry, and lack of pain or functional limitations. Despite the sometimes-impressive deformities, no treatment is warranted for this self-limiting condition. Bracing is meddlesome and expensive, and shoe modifications are unwarranted. The natural history of this condition is benign; therefore, parents simply need to be educated as to what to expect and when. Annual follow-up until resolution may help to assuage their fears.

In contrast, adolescent idiopathic genu valgum is not benign or self-limiting. Teenagers may present with a circumduction gait, anterior knee pain, and, occasionally, patellofemoral instability. The natural history of this condition may culminate in premature degenerative changes in the patellofemoral joint and in the lateral compartment of the knee.

Various other conditions, including postaxial limb deficiencies, genetic disorders such as Down syndrome, hereditary multiple exostoses, neurofibromatosis, and vitamin D–resistant rickets may cause persistent and symptomatic genu valgum. Some of these conditions require team management with other health care providers; however, surgical intervention is still likely to be necessary to correct the malalignment of the knees.

Epidemiology

Adolescent idiopathic genu valgum may be familial or may occur sporadically. The true incidence is unknown. Certainly, it is one of the most common causes of anterior knee pain in teenagers and is a frequent reason for orthopedic consultation. Predisposing syndromes, such as hereditary multiple exostoses, Down syndrome, and skeletal dysplasias, are more apt to manifest in patients aged 3-10 years, and valgus may become severe if untreated. Whereas the angle may not change, as the height increases, the mechanical axis progressively shifts more laterally, manifested by increasing knee pain and/or patellar instability.

Regardless of the etiology, surgical correction of significant and symptomatic malalignment is warranted; when required in younger children, the process may have to be repeated as they continue to grow.

In countries where malnutrition is common and access to medical care is limited, the overall incidence of genu valgum is undoubtedly higher. Although polio has been largely eradicated, other infectious diseases may result in growth disturbances. Mistreated (or untreated) traumatic injuries cause physeal damage or overgrowth (for example), resulting in progressive and disabling clinical deformity. Likewise, untreated congenital anomalies, skeletal dysplasias, genetic disorders, metabolic conditions, and rheumatologic diseases may cause genu valgum.

Prognosis

Provided that the appropriate criteria (ie, sufficient growth remaining, careful analysis and preoperative planning, proper plate insertion, periodic follow-up) are met, 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.[1]

That patient and family satisfaction are excellent is not surprising, given that guided growth, compared with osteotomy, is less invasive, relatively painless, more cost-effective, and less risky. Down time is minimal, and educational and recreational activities are only temporarily interrupted. Consequently, previous arbitrary guidelines pertaining to minimum age and diagnoses have been abandoned. In the author's opinion, guided growth with a tension band 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).

Wiemann et al compared the use of the eight-plate for hemiepiphysiodesis (n = 24) with physeal stapling (n = 39) in 63 cases of angular deformity in lower extremities. The eight-plate was as effective as staple hemiepiphysiodesis in terms of correction rate (~10º/year) and complication rate (12.8% vs 12.5%). However, patients with abnormal physes (eg, Blount disease, skeletal dysplasias) did have a higher rate of complications than those with normal physes (27.8% vs 6.7%), though there was no difference between the eight-plate group and the staple group.[2]  We have not shared this experience; the complication rate is exceedingly low in both groups.[3]

After analyzing 35 patients, Jelinek et al reported that a shorter operating time for implantation and explantation was noted for the eight-plate technique than for Blount stapling.[4]

Vaishya et al retrospectively studied 24 pediatric patients with bilateral (n = 11) or unilateral (n = 13) genu valgum deformity (35 knees) that required surgical correction in an attempt to evaluate the efficacy, correction rate, and complication rate associated with the use of the eight-plate in this setting.[5] Excellent results were achieved in 91.6% of patients. There was one case (4.16%) of partial correction and one case (4.16%) of superficial infection, which was taken care of. There were two cases (8.33%) of overcorrection, which was gradually self-corrected during follow-up.

 

Presentation

History

It is important to identify and document the natural history of genu valgum. On rare occasions, genu valgum may be noted in the nursery, indicating the presence of some type of localized or generalized skeletal malformation or dysplasia. Congenital lateral dislocation of the patella has been described. The extensor mechanism of the knee is displaced laterally so that every time the child contracts the quadriceps, the knee is flexed (rather than extended) and rotates outward, accentuating the valgus deformity. Another example is postaxial hypoplasia of the limb, sometimes first manifested by the absence of a lateral ray (or two rays) of the foot.[6]

More commonly, genu valgum does not become apparent until after the child reaches walking age. A normal variant of the disorder in toddlers (physiologic valgus) typically is symmetrical and pain-free, but it should resolve spontaneously by the time the child is aged 6 years. If the valgus is unilateral or symptomatic, referral to an orthopedist and radiographic evaluation are warranted.

Family history may be important because certain heritable conditions, such as hereditary multiple exostoses, Marfan syndrome, osteogenesis imperfecta, or vitamin D–resistant rickets may predispose a patient to this condition.

Physical Examination

The physical examination should include assessment of the gait pattern, including the propensity for circumduction, and evaluation of lower-extremity lengths. Stature, craniofacial features, the spine, and the upper extremities should be evaluated. Various genetic conditions and skeletal dysplasias may be documented in this manner; consultation with a geneticist may be warranted.

With the child standing, compare the relative limb lengths by leveling the pelvis with blocks and measuring and recording the intermalleolar distance (IMD). Torsional deformities of the femur, tibia, or both should be documented. Often, genu valgum is observed in association with outward torsion of the femur, the tibia, or both. Look for retropatellar crepitus and tenderness and note patellar tilt, tracking, and stability. For situations other than the aforementioned physiologic genu valgum, medical imaging is warranted.

 

Workup

Laboratory Studies

When an underlying syndrome is suggested by the physical findings and history, consultation with a geneticist and workup are warranted. If metabolic bone problems are a concern, relevant hematologic and urine studies are warranted, along with consultation with an endocrinologist. In a select few patients, bone densitometry studies may be warranted.

Imaging Studies

The criterion standard for documentation of genu valgum is a standing anteroposterior (AP) radiograph of the lower extremities, taken with the patellae facing forward. This study permits direct visualization of both the true and the apparent limb lengths and alignment. The length of each femur and tibia is measured, and any diaphyseal deformities (which would be missed on a scanogram) are clearly visible.

The mechanical axis is a line drawn from the center of the head of the femur to the center of the ankle; this line should bisect the knee. In normal variations, this line is still in the central 50% of the knee. Genu valgum is defined by lateral deviation of the axis or deviation toward or beyond the joint margin. The deformity may be in the femur, the tibia, or both. The normal lateral distal femoral angle is 84° (6° of valgus), and the medial proximal tibial angle is 87° (3° of varus).

When physeal abnormalities are suspected, obtain AP and lateral radiographs of the hip or knee (or fluoroscopy) to have better visualization of the physis. If a skeletal dysplasia is suggested, a skeletal survey is warranted.

A sunrise or Merchant view of the patellae may reveal tilt, subluxation, and, occasionally, osteochondral defects or loose bodies. Finally, it may be helpful to obtain an AP radiograph of the left wrist for bone age to confirm that remaining growth (ideally ≥12 months) is adequate to allow correction of a deformity by means of growth manipulation.

Histologic Findings

Depending on the underlying etiology of genu valgum, epiphyseal, physeal, or metaphyseal histologic abnormalities may be present. However, biopsy of the bone rarely is necessary or helpful. Such invasive procedures may have an adverse effect upon physeal growth and the outcome of treatment.

 

Treatment

Approach Considerations

Physiologic genu valgum should be treated expectantly. The family should be educated to avert unnecessary concerns and inappropriate treatment. Bracing and corrective shoes are ineffective, and physical therapy is of no benefit. Pathologic genu valgum warrants aggressive treatment to alleviate symptoms and prevent progression. Bracing and therapy are inadequate to meet these goals. Surgical intervention is the only successful intervention for correcting the problem. Surgical options include osteotomy or growth manipulation (hemiepiphysiodesis).

Physeal closure, whether it be due to local trauma or to skeletal maturity, is the sole contraindication for using guided growth to correct the deformity. Obviously, this technique cannot be used after skeletal maturity, when the only option is a corrective osteotomy. In some cases, malrotation actually improves or is resolved as the mechanical axis is restored to neutral; therefore, rotational osteotomies may be reserved for patients who are still troubled by unresolved malrotation. Likewise, lengthening (along the anatomic axis) may be reserved for children who ultimately require limb-length equalization.

Stapling was introduced in 1949 by Blount, but its popularity has since waned. Some of the failures and criticisms were a direct result of poor technique (wrong staples, periosteal elevation). By the 1970s, stapling had been abandoned by many; even more recent review articles and book chapters pertaining to correction of angular deformities or limb-length inequality have tended to dismiss it as a risky, unpredictable, or outmoded technique. Meanwhile, osteotomies, whether secured by cast or by internal or external fixation, are not without occasional serious consequences.

Percutaneous epiphysiodesis offers the theoretical advantages of a smaller scar and no hardware to retrieve. However, it is not reversible, and thus, the timing must be perfect to avoid overcorrection. Accordingly, this technique 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 in either direction. 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 (eg, hardware rigidity, migration, and breakage), the author has devised a preferable method for guided growth. This involves the use of a nonlocking two-hole tension band plate to provide a flexible yet secure tether. With the application of a single plate per physis, the directional control afforded allows the correction of frontal-, sagittal-, or oblique-plane deformities.

This procedure 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.

Medical Therapy

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.

Surgical Options

Stapling has waned in popularity since its introduction, having been supplanted by the tension band plate concept. Reference works typically dismiss it as a historical procedure, citing unpredictability and the fear of permanent physeal arrest as results of stapling. Although stapling can work well, occasional breakage or migration of staples can necessitate revision of hardware or premature abandonment of this method of treatment. (See the image below.)

Heretofore, stapling was a viable option. This out Heretofore, stapling was a viable option. This outpatient procedure permitted simultaneous and multiple deformity correction, without casts or delayed weightbearing. However, the concept of compressing and overpowering the physes has the drawbacks of slower correction because the fulcrum is within the physis. Provided the rigid staples did not dislodge or fatigue, satisfactory correction could be realized. If the hardware failed prematurely, the correction was either abandoned or the hardware exchanged. Compared with osteotomies, it was a risk worth taking, that is, until the advent of a better option.

Some surgeons have reverted to osteotomy of the femur and/or tibia-fibula as the definitive means of addressing genu valgum. However, this is a very invasive method fraught with potential complications, including malunion, delayed healing, infection, neurovascular compromise, and compartment syndrome. Further complicating the picture, these deformities are often bilateral, requiring a staged correction. The aggregate hospitalization, recovery time, costs, and risks make osteotomy a last resort for angular corrections (unless the physis has already closed).

Percutaneous drilling or curettage of a portion of the physis yields only a small scar and no implant is required. However, this is a permanent, irreversible technique. Therefore, its use is necessarily restricted to adolescent patients and is predicated upon precise timing of intervention, requiring close follow-up to avoid undercorrection or (worse yet) overcorrection.

Some authorities advocate using percutaneous epiphyseal transcutaneous screws as a means of achieving angular correction.[7, 8]  Although this is performed through a small incision, the physis is violated, and the potential exists for the formation of an unwanted physeal bar, with its sequelae. To date, the potential for reversing the procedure has not been documented in younger children; therefore, the only reported cases have been in adolescents.

By comparison, guided growth, using a nonlocking two-hole plate and screws, is a reversible and minimally invasive outpatient procedure, allowing multiple and bilateral simultaneous deformity correction. A single implant is used per physis (see the images below); this serves as a tension band, allowing gradual correction with growth. Because the focal hinge of correction (CORA) is at or near the level of deformity, compensatory and unnecessary translational deformities are avoided.[9, 10]

The application of a single 8-plate per physis per The application of a single 8-plate per physis permits the same correction as stapling, without the potential drawbacks of implant migration or fatigue failure. Based on the principle of facilitating rather than compressing the physes, the correction occurs more rapidly and rebound growth, though possible, may be less frequent. When the mechanical axis has been restored to neutral, the plates (or metaphyseal screws) are removed (and replaced as necessary if recurrent deformity ensues).
This 14-year-old boy, weighing 132 kg, presented w This 14-year-old boy, weighing 132 kg, presented with activity-related anterior knee pain, circumduction gait, and difficulty with running and sports. His symptoms had been progressive over a period of 18 months despite nonoperative measures including physical therapy, activity restrictions, and nonsteroidal anti-inflammatory drug therapy.
Nine months following the insertion of 8-plates in Nine months following the insertion of 8-plates in the distal femora (1 per knee), the mechanical axis is approaching neutral and his symptoms abated. The plates were removed 2 months later, allowing for full correction of his valgus deformities. He has not had recurrence.

The previous empirical constraints related to the indications for instrumented hemiepiphysiodesis, including appropriate age group and the etiology of deformity, have been challenged successfully with this technique, and results have been consistently good. During the past decade, in a personal series of more than 1000 patients ranging in age from 19 months to 18 years, some of whom had pan-genu deformities, the senior author has not had a permanent physeal closure, nor have any been reported in the literature.

Guided growth has emerged as the treatment of choice in the growing child; osteotomy should be reserved as a salvage option (or for mature patients). 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 two-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 have 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. If recurrence is anticipated, an option is to remove the metaphyseal screw percutaneously, monitor subsequent growth, and insert another screw as needed.

Surgical Therapy

Preparation for surgery

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, unless progressive pain manifests. The patient's height should be recorded, along with the limb lengths and the intermalleolar distance (IMD), measured with the patient standing with knees touching.

Preoperative planning should include obtaining full-length radiographs to select the optimal solution, predict the outcome, and convey this information to the family. In 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, whereas 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).[11]

Remember to evaluate sagittal alignment of the knee, because concomitant 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), two plates are used, one just lateral to the sulcus and the other 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 the need to resort to distraction osteogenesis.

Operative details

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 (or stainless steel) two-hole (nonlocking) plate is placed over the needle, and the 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 and metaphyseal next. After starter holes are drilled to a depth of 5 mm with the cannulated 3.2-mm drill, the plate is securely attached with two of the 4.5-mm cannulated self-tapping screws. The screws need not be parallel, but they should not violate the physis or the joint. Ideally, the plate should be placed midsagittally so as to avoid an iatrogenic recurvatum 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 eight-plate, which is secured according to the technique described above. The titanium eight-plate comes in two sizes, 12 mm and 16 mm (measured from center hole to center hole). The two sizes are both low-profile and are of equal thickness, with a center hole for the needle to allow accurate placement.

The screws are titanium (or stainless steel), cannulated, and self-tapping; they come in three lengths: 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. By design, this is not a locking plate; the principle is to deflect the physis (tension band) rather than overpower it. Thus, it is a paradigm shift and departure from compressive (stapling, Metaizeau) or ablative (physeal drilling) methodologies.

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

This 14-year-old boy broke his distal femur 1 year This 14-year-old boy broke his distal femur 1 year previously. He was treated with internal fixation using a condylar plate, and the fracture healed uneventfully. However, he developed medial overgrowth of the femur, which caused progressive and painful genu valgum. Note the lateral displacement of the mechanical axis into zone 2. One alternative is to perform a supracondylar osteotomy with exchange of the plate; this was declined.
Two options for instrumented and reversible hemi-e Two options for instrumented and reversible hemi-epiphysiodesis are multiple staples versus a tension band plate. The latter, being flexible yet secure, avoids the potential risks of hardware breakage or migration. Furthermore, growth is facilitated rather than restricted and the alignment is restored more rapidly.
One year following guided growth of the femur with One year following guided growth of the femur with an 8-plate, his mechanical axis is neutral, his limb lengths are equal, and his symptoms have abated; the plate was then removed. Neither procedure required hospitalization or immobilization. Each time he was able to rapidly resume sports participation.
A 17-year-old male who underwent an arthroscopic r A 17-year-old male who underwent an arthroscopic reconstruction of his left anterior cruciate ligament utilizing braided semitendinosis 1 year prior to this film. With ensuing growth he developed progressive genu valgum with medial and anterior knee pain and difficulty running.
A fluoroscopic close-up view of the left knee demo A fluoroscopic close-up view of the left knee demonstrates, despite his chronologic age of 17, that he has significant growth remaining. (Note arrows pointing to the physis = growth plate). It was felt that the most expedient and safe treatment would be guided growth. Considering his relative skeletal maturity, it was elected to apply tension band plates to the femur and tibia simultaneously, for the sake of time.
The patient's legs are straight 11 months followin The patient's legs are straight 11 months following pan-genu guided growth of the medial femur and tibia. His pain has resolved and he has resumed a fully active lifestyle. His limb lengths are equal and his knee remains stable.
A standing AP radiograph of the legs confirms the A standing AP radiograph of the legs confirms the clinical findings; the plates were therefore removed.
This 6-year-old girl, born with tibial dysplasia, This 6-year-old girl, born with tibial dysplasia, underwent foot ablation at age 2 years, combined with surgical synostosis of the distal fibula to the tibial stump. She developed progressive genu valgum necessitating that the prosthetist move the post medially. However, she then experienced medial knee pain and stump irritation. This full-length weight-bearing radiograph demonstrates lateral displacement of the mechanical axis (red dotted line) to the joint margin.
Treatment options are limited to osteotomy or guid Treatment options are limited to osteotomy or guided growth. An osteotomy would require "down time" - out of her prosthesis and non weight-bearing while the cut bone is healing.
The family chose the option of guided growth, and The family chose the option of guided growth, and plates were applied to the distal medial femur and proximal medial tibia. She resumed full activities in her prosthesis and this full-length radiograph, taken one year later, demonstrates normalization of the mechanical axis. At this point the prosthetist moved her post laterally. Her knee pain and stump irritation have abated.
A close-up view demonstrating the neutral mechanic A close-up view demonstrating the neutral mechanical axis and open growth plates. Note the divergence of the screws. At this point, the plate was removed. Further growth will be monitored, repeating guided growth if needed.
A clinical photograph showing her alignment just p A clinical photograph showing her alignment just prior to hardware removal.

Postoperative Care

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

Complications

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 tension band plates, the problems of hardware migration or fatigue have been solved. The screws intentionally diverge with growth; however, this does not necessitate screw exchange. The screws are relatively thin (2 mm). By design, the plates have a narrow waist, enabling reverse bending if additional angular correction is required.

There have been no reports of broken plates. Rare instances of broken metaphyseal screws have been reported. This may result from a technical error. If a gap is left between the plate and the metaphysis, the screw will be subject to three-point bending stress and may fatigue.

Because the bone is not divided, no need exists to wait for bone healing. The means of avoiding this include increasing the convex contour of the plate and, alternately, tightening each screw after removing the guide pins in order to ensure tight fit of the plate against the bone.

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. This was reported with stapling,[12] especially in children younger then 10 years, but seems to be 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. A study by Farr et al found rebound of frontal plane malalignment after tension band plating to be more likely in patients who were more than 1 year short of skeletal maturity and those with an increased body mass index (BMI).[13]

In any case, in the event of recurrent deformity, repeat plate (or metaphyseal screw) application is warranted if rebound growth occurs to the point where 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 that meticulous care is taken to place (and remove) plates without disturbing the periosteum. In 10 years of plating, including more than 1000 children with the full spectrum of diagnoses, the author has yet to observe this complication. Remember that all of these patients would have had one or more osteotomies if they had not undergone guided growth.

Long-Term Monitoring

Guided growth mandates periodic follow-up evaluations (typically at 3-month 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 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) (or just the metaphyseal screws) should be removed when the mechanical axis is neutral, and further growth should be monitored.

A study by Sweeney et al suggested that changes in coronal plane anatomic alignment in patients being treated for genu valgum with hemiepiphysiodesis can be reasonably estimated by measuring changes in screw divergence and thus that focal radiographic imaging of the knee can be used for postoperative follow-up in lieu of standing full-length limb radiographs so as to limit radiation to the pelvis.[14]

Guided growth may be safely repeated for angular or length discrepancies, according to the needs of the individual patient.