You are in: eMedicine Specialties > Orthopedic Surgery > PEDIATRICS Genu Valgum, PediatricsArticle Last Updated: Jul 19, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Peter M Stevens, MD, Professor, Director of Pediatric Orthopedic Fellowship Program, Department of Orthopedics, University of Utah School of Medicine Peter M Stevens is a member of the following medical societies: Alpha Omega Alpha, American Academy of Orthopaedic Surgeons, American Orthopaedic Association, Limb Lengthening and Reconstruction Society ASAMI-North America, Pediatric Orthopaedic Society of North America, Utah Medical Association, and Western Orthopaedic Association Coauthor(s): Michael C Holmstrom, MD, Consulting Surgeon, Department of Orthopedics, The Orthopedic Specialty Hospital (TOSH) Editors: Mininder S Kocher, MD, MPH, Associate Professor of Orthopedic Surgery, Harvard Medical School/Harvard School of Public Health; Associate Director, Division of Sports Medicine, Department of Orthopedic Surgery, Children's Hospital Boston; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; George H Thompson, MD, Professor of Orthopedic Surgery and Pediatrics, Department of Pediatric Orthopedic Surgery, Case Western Reserve University; Director, Rainbow Babies and Children's Hospital; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Dennis P Grogan, MD, Clinical Professor, Department of Orthopedic Surgery, University of South Florida College of Medicine; Chief of Staff, Department of Orthopedic Surgery, Shriners Hospital for Children of Tampa Author and Editor Disclosure Synonyms and related keywords: physiologic genu valgum, pathologic genu valgum, adolescent idiopathic genu valgum, knock-knee deformity, osteotomy, hemiphyseal stapling, vitamin D resistant rickets, vitamin D-resistant rickets, guided growth, 8-plate INTRODUCTIONSection 2 of 12
  Genu valgum is the Latin-derived term used to describe knock-knee deformity. While many otherwise healthy children have knock-knee deformity as a passing trait, some individuals retain or develop this deformity due to hereditary or genetic disorders or metabolic bone disease. 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 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 using the classic Phemister bone block technique, the percutaneous method, hemiphyseal stapling, or, more recently, application of a single 2-hole plate and screws around the physis. The senior author, having experience in each of these techniques, has developed the later technique in order to solve 2 of the problems sometimes encountered with staples, namely hardware fatigue and migration. The rationale and versatility of this technique for managing genu valgum are the emphasis of this article. History of the ProcedureThe focus of this article is the indications, techniques, complications, and outcome of guided growth using the reversible plate technique for the correction of pathologic genu valgum. Since the introduction of staples by Walter Blount in 1949, this procedure has waxed and waned in popularity and remains the subject of criticism and controversy. Indeed, some recent review articles and book chapters dismiss stapling as a historical procedure, citing unpredictability and the fear of permanent physeal arrest as results of stapling. While stapling can work well, occasional breakage or migration of staples can necessitate revision of hardware or premature abandonment of this method of treatment. 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. While 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, its no potential for reversing the procedure has been document; therefore, the only reported cases have been in adolescents. By comparison, guided growth, using a nonlocking 2-hole plate and screws, is a reversible and minimally invasive outpatient procedure, allowing multiple and bilateral simultaneous deformity correction. A single implant (the authors prefer the Orthofix [McKinney, Tex] 8-plate) per physis; this serves as a tension band, allowing gradual correction with growth. Because the focal hinge of correction is at or near the level of deformity, compensatory and unnecessary translational deformities are avoided. The previous empirical constraints related to the indications, including appropriate age group and the etiology of deformity, have been successfully challenged using this technique, with consistently good results. In a personal series of more than 100 patients, ranging in age from 19 months to 17 years, and some with pan-genu deformities, the senior author has not had a permanent physeal closure. ProblemNormal alignment means that the lower extremity lengths are equal and the mechanical axis (center of gravity) 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. 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. 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. FrequencyAdolescent idiopathic genu valgum may be familial, or it 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. Likewise, the incidence of the predisposing syndromes is difficult to ascertain. 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. Regardless of the etiology, surgical correction of significant and symptomatic malalignment is warranted, regardless of the age of the patient. In countries where malnutrition is common and access to medical care is limited, the overall incidence of genu valgum is undoubtedly higher. While polio has been largely eradicated, other infectious diseases and mistreated (or untreated) traumatic injuries make physeal damage a frequent cause of progressive and disabling clinical deformity. Likewise, untreated congenital anomalies, genetic disorders, rheumatologic diseases, and hemophilia may cause genu valgum. EtiologyThe fact that toddlers aged 2-6 years may have physiologic genu valgum is well recognized. 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. PathophysiologyWith normal alignment, the physes and epiphyses are shielded from pathologic stress, and balanced growth preserves straight legs and normal function. In genu valgum, as the mechanical axis shifts laterally, pathological stress is placed on the lateral femur and tibia, inhibiting growth and possibly leading to a vicious cycle. Not only is physeal growth inhibited, but also the Hueter-Volkmann effect upon the entire epiphysis prevents its normal expansion. According to the Hueter-Volkmann principle, continuous or excessive compressive forces upon the epiphysis have an inhibitory effect upon 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. 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. 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. 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. ClinicalThe history of the deformity is important to ascertain and document. 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. 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. 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 and/or tibia should be documented. Often, genu valgum is observed in association with outward torsion of the femur, 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. INDICATIONSSection 3 of 12
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). RELEVANT ANATOMYSection 4 of 12
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 (the normal angle is 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 (the normal angle is 87°). The mechanical axis 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 2 central quadrants of the knee is deemed acceptable. CONTRAINDICATIONSSection 5 of 12
Physeal closure, whether it be due to local trauma or to maturity is the sole contraindication to using guided growth for deformity correction. 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. WORKUPSection 6 of 12
Lab Studies
Imaging Studies
Other Tests
Histologic FindingsDepending upon the underlying etiology of genu valgum, epiphyseal, physeal, and/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. TREATMENTSection 7 of 12
Medical therapyFor 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 therapyHaving 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. Preoperative detailsThe 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. Intraoperative detailsThe 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; McKinney, Tex) 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 (Orthofix; McKinney, Tex) 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. Postoperative detailsFollowing 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. Follow-upGuided 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 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. COMPLICATIONSSection 8 of 12
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. OUTCOME AND PROGNOSISSection 9 of 12
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. Patient and family satisfaction are excellent; this is not surprising in light of the fact that, in comparison to 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). FUTURE AND CONTROVERSIESSection 10 of 12
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; McKinney, Tex). 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. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Genu Valgum, Pediatrics excerpt Article Last Updated: Jul 19, 2007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
