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, the relative limb lengths should be compared 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. It is important to 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.
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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.
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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.
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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.
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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).
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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A standing AP radiograph of the legs confirms the clinical findings; the plates were therefore removed.
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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.
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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.
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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.
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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.
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A clinical photograph showing her alignment just prior to hardware removal.
